Transcript Unit One: Cell Biology

Unit One: Cell Biology
National 4/5
Units:
• Cell Biology – now till October
• Multicellular Animals – October – Feb
• Life on Earth – February - April
National 4/5 Biology Course Unit 1
How is the course assessed?
• Course work:
– 3 end of unit tests (one for each unit) – can
have resits if necessary
– One Practical investigation
– One mini research project (100 words)
– One LARGE research project (Added Value)
(500-800 words)
– NATIONAL 5 – Final exam!
National 4/5 Biology Course Unit 1
Work
Classwork to be done in jotter.
Remember it every day!
You will get set homework sometimes –
but expected to learn the work done
each day as you go along!!!
National 4/5 Biology Course Unit 1
What is in Unit One?
• Cell Biology:
–
–
–
–
–
–
–
–
Cell Structure
Transport across membranes
Producing new cells
DNA and protein production
Genetic engineering
Proteins and enzymes
Aerobic respiration
Photosynthesis
National 4/5 Biology Course Unit 1
1: Cell Structure
Level
What you need to be able to do…
4/5
Label an animal cell – Cell membrane, cytoplasm and
nucleus
4/5
Label a plant cell – Cell wall, cell membrane,
cytoplasm, nucleus, chloroplast and vacuole
4/5
State the function of all the parts of animal and
plant cells listed above
5
Identify the mitochondria and ribosomes in a cell
diagram
5
Explain the function of a mitochondria and a
ribosome
5
Label a bacterial cell and explain the differences
between it and other types of cell.
5
4/5and
Biology
Course
Unit
1
Label a National
fungal cell
explain
the
differences
between it and other types of cell.
Cell Structure
Cells are the building blocks of all life.
Cells video
National 4/5 Biology Course Unit 1
Cell Structure
We will be looking at 4 different cell types:•
•
•
•
Animal cells
Plant cells
Bacterial cells, and
Fungal cells.
You have already looked at the basic structure of
animal and plant cells in S1- S3. We will be
looking at all of these cells in greater detail.
National 4/5 Biology Course Unit 1
What can you remember from
last year?
Task One: Complete the revision
worksheet on cells.
National 4/5 Biology Course Unit 1
Cell Structure
Task 2: Prepare slides for examination under a
light microscope.
Using the help sheets provided prepare one
type of slide – cheek cell, onion cell or Elodea
pondweed. After you have examined your own
slide share your slide with a group that has
prepared a different slide . You should look at
all 3 cell types.
National 4/5 Biology Course Unit 1
Cheek Cells
These are cheek cells viewed at 100x magnification
using a light microscope.
National 4/5 Biology Course Unit 1
http://www.stancoe.org/patterson/cms/staff/humancheekcellwebpage.htm
Onion Skin Cells
These are onion skin cells viewed at 40x
magnification using a light microscope.
National 4/5 Biology Course Unit 1
http://www.baileybio.com/plogger/images/biology/lab_-_plant___animal_cells/onion_cells.jpg
Elodea Pondweed Cells
These are Elodea pondweed cells viewed at
100x magnification using a light microscope
National 4/5 Biology Course Unit 1
http://seys-science.wikispaces.com/elodea+g
Cell Structure
We will now look in more
detail at the structure of
animal and plant cells.
To see more detail or the
ultra structure of cells
we need to use and
electron microscope.
Image from Wikipedia commons http://en.wikipedia.org/wiki/File:Electron_Microscope.jpg
National 4/5 Biology Course Unit 1
Cell Structure - Organelles
Organelle is the name given to the
structures found inside the cell e.g.
Nucleus, vacuole, chloroplasts etc.
You need to know about 2 more organelles.
Mitochondria and Ribosomes
National 4/5 Biology Course Unit 1
Mitochondria
Mitochondria are the power houses of
cells. They convert energy into forms
that are usable by the cell. They are
found in the cytoplasm and are the sites
of cellular respiration which generates
fuel for the cell's activities.
Mitochondria are found in the
cytoplasm of the cell.
National 4/5 Biology Course Unit 1
Electron microscope
image of a
mitochondrion
(credit: Tom Deerinck and Jeff Martell/MIT)
National 4/5 Biology Course Unit 1
http://people.eku.edu/ritchisong/ritchiso/mitochondrion2.gif
Ribosomes
Ribosomes can be found
floating free in the
cytoplasm or attached to
another type of organelle
called Rough Endoplasmic
Reticulum or R.E.R. for
short. (you don’t have to
know about R.E.R!)
National 4/5 Biology Course Unit 1
Electron Microscope image of
ribosomes.
Ribosomes are
responsible for
protein synthesis,
i.e. this is where
amino acids are
assembled into
proteins.
http://www.cbv.ns.ca/bec/science/cell/page11a.gif
http://bioweb.uwlax.edu/genweb/molecular/theory/translation/ribosome.jpg
National 4/5 Biology Course Unit 1
Cell Structure – Organelles
Task 3 – Collect the diagram sheets of
the animal cell and the plant cell. Label
any structures you recognise.
You will need to include:- Cell membrane,
nucleus, cell wall, vacuole, chloroplast,
cytoplasm, ribosome and mitochondria.
National 4/5 Biology Course Unit 1
Animal Cell Diagram
Cytoplasm
Nucleus
Ribosomes
Mitochondrion
Cell Membrane
National 4/5 Biology Course Unit 1
Plant Cell Diagram
Ribosomes
Mitochondria
Cell Membrane
Cell
Wall
Nucleus
Chloroplast
Vacuole
National 4/5 Biology Course Unit 1
Cytoplasm
Cell Structure - Organelles
Task 4 – Collect and complete the
worksheet :–
Cell structures and functions.
National 4/5 Biology Course Unit 1
Bacterial Cells
“For the first half of geological time our
ancestors were bacteria. Most creatures still
are bacteria, and each one of our trillions of
cells is a colony of bacteria.”
Richard Dawkins
National 4/5 Biology Course Unit 1
Bacteria
TThey are the oldest living
organisms on earth. They are
everywhere. We find them on and in
the human body, in the air we
breathe, on the surfaces we touch,
in the food we eat. Almost 99% of
these bacteria are helpful,
whereas the remaining are the
notorious ones. Some are essential
for proper growth of other living
beings. They are either free-living
or form a symbiotic relationship
with animals or plants.
http://en.wikipedia.org/wiki/File:Gram_Stain_Anthrax.jpg
National 4/5 Biology Course Unit 1
Bacteria
Task 1 : Using the information cards, list
the helpful and harmful bacteria with a
brief description of why they are useful
or what disease they cause.
Bacteria
Helpful of harmful
Why are they useful or
what disease do they
cause?
National 4/5 Biology Course Unit 1
Structure of Bacteria
Bacteria can occur in different shapes. However
their basic structure is the same.
Task 2: Collect the bacterial cell diagram
handout and the information sheet.
Use the information to complete the labels on
the diagram and to complete the table.
National 4/5 Biology Course Unit 1
Cytoplasm
Cell Wall
Capsule
Plasmid
Genetic
material
Cell
Membrane
National 4/5 Biology Course Unit 1
Structure
Function and importance
Capsule
Provides additional protection from the
environment
Cell Wall
It strengthens and supports the cell
Cell Membrane
Genetic Material
Plasmid
Cytoplasm
Controls the movement of substances into and out of
the cell
Made of DNA and controls the activities of the cell
Circular genetic material. Can convey special
abilities, e.g. a resistance to certain antibiotics.
They can be manipulated by man to produce
bacterial cells that produce useful products e.g.
Insulin, hormones and enzymes.
Most chemical
processes
take
place
National
4/5 Biology
Course
Unit
1 here
controlled by enzymes
Fungal Cells
Fungi are one of the most important
groups of organisms on the planet. They
are important in an enormous variety of
ways: Task 3: Listen and take brief notes to
produce a spider diagram of the
importance of fungi.
National 4/5 Biology Course Unit 1
Recycling
Fungi, together with bacteria,
are responsible for most of
the recycling of nutrients
returning dead material to the
soil in a form in which it can
be reused. Without fungi,
these recycling activities
would be seriously reduced.
http://commons.wikimedia.org/wiki/File:Chanterelle_
Cantharellus_cibarius.jpg
National 4/5 Biology Course Unit 1
Mycorrhizae and plant growth
Fungi are vitally important
for the good growth of
most plants, including
crops. They do this
through the development
of mycorrhizal
associations which help
plants obtain more
nutrients from the soil.
http://en.wikipedia.org/wiki/File:Mycorrhizal_root_tips_(a
manita).jpg
National 4/5 Biology Course Unit 1
Food
Fungi are also important directly as food for
humans. Many mushrooms are edible and
different species are cultivated for sale
worldwide. Fungi are also widely used in the
production of many foods and drinks. These
include cheeses, beer and wine, bread, some
cakes, and some soya bean products.
National 4/5 Biology Course Unit 1
http://en.wikipedia.org/wiki/File:Asian_mushrooms.jpg
Medicines
Penicillin, perhaps the most
famous of all antibiotic
drugs, is derived from a
common fungus called
Penicillium. Many other
fungi also produce
antibiotic substances,
which are now widely used
to control diseases in
human and animal
populations.
Photo by: Dr. David Midgley Cultures: Dr. David
Midgley University of Sydney, Australia.
National 4/5 Biology Course Unit 1
Biocontrol
Fungi such as the Chinese caterpillar
fungus, which parasitise insects, can
be extremely useful for controlling
insect pests of crops. The spores of
the fungi are sprayed on the crop
pests which then infect the insect
resulting in its death. Fungi have also
been used to control Colorado potato
beetles, spittlebugs, leaf hoppers
and citrus rust mites. This method is
generally cheaper and less damaging
to the environment than using
chemical pesticides.
Author : L. Shyamal
http://upload.wikimedia.org/wikipedia/commons/9/9
4/CordycepsSinensis.jpg
National 4/5 Biology Course Unit 1
Crop Diseases
Fungal parasites may be useful in biocontrol, but they
can also have enormous negative consequences for
crop production. Some fungi are parasites of plants.
Most of our common crop plants are susceptible to
fungal attack of one kind or another. Spore
production and dispersal is enormously efficient in
fungi and plants of the same species crowded
together in fields are ripe for attack. Fungal diseases
can on occasion result in the loss of entire crops if
they are not treated with antifungal agents.
National 4/5 Biology Course Unit 1
Animal Disease
Fungi can also parasitise domestic animals causing
diseases, but this is not usually a major economic
problem. A wide range of fungi also live on and in
humans, but most coexist harmlessly. Athletes foot
and Candida infections are examples of human fungal
infections.
Author:James Heilman, MD
National 4/5
Biology Course Unit 1
http://en.wikipedia.org/wiki/File:FeetFung
al.JPG
Food Spoilage
It has already been noted that fungi play a major role in
recycling organic material. The fungi which make our
bread and jam go mouldy are only recycling organic
matter, even though in this case, we would prefer
that it didn't happen! Fungal damage can be
responsible for large losses of stored food,
particularly food which contains any moisture. Dry
grains can usually be stored successfully, but the
minute they become damp, moulds are likely to render
them inedible. This is obviously a problem where large
quantities of food are being produced seasonally and
then require storage until they are needed.
National 4/5 Biology Course Unit 1
Structure of a fungal cell
Task 4: Collect the diagram sheet and
label any of the structures and
organelles you recognise.
National 4/5 Biology Course Unit 1
Structure of a fungal cell
Cell Wall
Cell Membrane
Nucleus
Cytoplasm
Vacuole
National 4/5 Biology Course Unit 1
All the cell parts are now familiar. You should be able to
compare all the cell types and identify which parts
are similar and which are not. While all the cell parts
have the same functions as before there is one
difference.
The fungal cell wall.
Just as the bacterial cell wall has a different chemical
structure from a plant cell wall, so does the fungal cell
wall.
The fungal cell wall is made from a chemical called
chitin.
National 4/5 Biology Course Unit 1
It is important that you know
The cell walls in plant, bacterial and
fungal cells is structurally and
chemically different.
National 4/5 Biology Course Unit 1
Homework
Collect the homework sheet :-
Cell Structure – Review Homework
National 4/5 Biology Course Unit 1
2. Transport across cell
membranes
Level
What you need to be able to do…
4/5
Describe the structure of the cell membrane
4/5
Explain what happens during diffusion
4/5
Explain what happens during osmosis
5
Describe the effects of different water
concentrations on animal and plant cells
5
Explain the difference between passive and active
transport
National 4/5 Biology Course Unit 1
Cell membrane
• The thin, flexible cell membrane
enclosing the cell contents
controls which substances may
enter and leave the cell.
National 4/5 Biology Course Unit 1
The Cell Membrane
• The cell membrane (or plasma
membrane) is made up of a bilayer of
lipids with protein scattered throughout
and is selectively permeable.
• Proteins can;
–
–
–
–
be attached to the surface
be embedded within the bilayer
span the whole bilayer
form channels in the lipid bilayer
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
• Small molecules can pass through pores
in the membrane made by channel
forming proteins and enter or leave the
cell. This is why the plasma membrane is
selectively permeable.
• This transport of molecules is passive
and requires no energy as it is with the
concentration gradient.
National 4/5 Biology Course Unit 1
Concentration Gradients
• When molecules in gases or liquids are
unevenly distributed we say that a
concentration gradient exists.
• Because the molecules are constantly
moving around they tend to distribute
themselves evenly, i.e. they always move
from an area of high concentration to an
area of low concentration, down the
concentration gradient.
National 4/5 Biology Course Unit 1
High
Concentration
Molecules move down
the concentration
gradient
Low
Area 1
Area 2
National 4/5 Biology Course Unit 1
• Teacher demonstration of diffusion
National 4/5 Biology Course Unit 1
Diffusion
• Diffusion is the name given to this
movement of the molecules of a
substance from a region of high
concentration of that substance to a
region of low concentration of that
substance until the concentration
becomes equal.
National 4/5 Biology Course Unit 1
Diffusion Activity
• Cut a 20cm piece of visking tubing and tie a knot
in one end.
• Soak the tubing in water and never let it dry out
during the experiment.
• Fill the visking tubing with 5-10cm3 starch and
glucose solution and seal with another knot.
• Place this in a boiling tube of water completely
submerged and leave until the next lesson.
National 4/5 Biology Course Unit 1
Take a small sample of the water from around
the test tube. Test for starch and sugar
Test
for
starch
2. Add 4
drops of
IODINE
1. Put sample on
tray
Test for
sugar
BOILING
WATER
3. If starch is present it goes
from brown to black
2. Add 4
drops of
BENEDICTS
SOLUTION
3. If sugar is present it goes from
blue to orange
1. Put sample in test tube – IN a
beaker of BOILING National
WATER 4/5 Biology Course Unit 1
Activity
• Perform Benedict’s test and starch test
on the water in the boiling tube from
Diffusion in a Model Cell experiment you
set up last lesson.
• Explain your results in terms of
diffusion. (LO1 assessment).
National 4/5 Biology Course Unit 1
Importance of diffusion to
cells
In an animal cell, food (such as glucose),
oxygen and carbon dioxide will diffuse
like this:
National 4/5 Biology Course Unit 1
Carbon dioxide
Oxygen
Glucose
National 4/5 Biology Course Unit 1
Substances which diffuse in
or out of cells
Diffuse IN
Diffuse OUT
Oxygen (raw material for
respiration)
Carbon dioxide (PLANTS
ONLY, raw material for
photosynthesis)
Carbon dioxide (waste from
respiration)
Oxygen (PLANTS ONLY,
made in photosynthesis)
Glucose (raw material for
respiration)
Amino acids (raw materials
to build the cell)
Urea (a cell waste product)
National 4/5 Biology Course Unit 1
Osmosis: the diffusion of
water
National 4/5 Biology Course Unit 1
Osmosis
• The diffusion of water through a
selectively-permeable membrane from
an area of high concentration of water
molecules to an area of low
concentration of water molecules is
called osmosis.
National 4/5 Biology Course Unit 1
Osmosis words
Isotonic – same water concentration.
Hypotonic – High water concentration e.g..
Pure water
Hypertonic – Low water concentration e.g.
water with sugar and salt dissolved in it.
National 4/5 Biology Course Unit 1
Effects of Osmosis on Plant Cells
Cells in a
dilute/
hypotonic
solution
become
turgid
Cells in
concentrated/
hypertonic
solutions
become
National 4/5 Biology Course Unit 1
flaccid.
Cells in the
same/
isotonic
solution stay
the same.
Plasmolysed
cell – cytoplasm
is pulled away
from the cell
wall.
Turgid Cells
• Osmosis makes plant cells
swell. Water moves into
the plant cell vacuole and
pushes against the cell wall.
The cell wall stops the cell
from bursting. We say
that the plant is turgid.
This is useful as it gives
plant stems support.
National 4/5 Biology Course Unit 1
Flaccid Cells
• If a plant lacks water, it
wilts and the cells become
flaccid as water has moved
out of the cell. If alot of
water leaves the cell, the
cytoplasm starts to peel
away from the cell wall.
We say the cell has
undergone plasmolysis.
National 4/5 Biology Course Unit 1
Osmosis in Animal Cells
Cell placed in distilled
water/hypotonic solution
Cell placed in
concentrated/hypertonic
solution
National 4/5 Biology Course Unit 1
Active Transport
• Active transport is the movement of
molecules across a cell membrane from a
low to a high concentration i.e against a
concentration gradient.
• Active transport works in the opposite
direction to the passive transport of
diffusion and always requires energy.
• This energy is released during
respiration.
National 4/5 Biology Course Unit 1
ENERGY
National 4/5 Biology Course Unit 1
Sodium/potassium pumps
• Active transport carriers are often
called pumps.
• In this example, the same carrier
molecule actively pumps sodium ions out
of the cell and potassium ions into the
cell, each against a concentration
gradient.
• Video clip
National 4/5 Biology Course Unit 1
3. Producing New Cells
Level
What you need to be able to do…
4/5
Describe what happens during mitosis
4/5
Explain what the chromosome complement is and why
it important that it is maintained
4/5
Explain how mitosis (cell cycle) is controlled and how
this can lead to cancer
National 4/5 Biology Course Unit 1
Everyone in this room
started life as a single
cell, a fusion of a sperm
and egg cell.
What processes must
have happened to develop
you from that single cell?
National 4/5 Biology Course Unit 1
How many new cells do you
think you will make in a day?
Cell Division throughout Life
National 4/5 Biology Course Unit 1
330 000 000 in 20 minutes
so…
23,760,000,000 new cells every
day!
National 4/5 Biology Course Unit 1
What do these pictures all have
in common?
National 4/5 Biology Course Unit 1
They are all examples of Cell
Division in action for growth or
repair!
National 4/5 Biology Course Unit 1
How do Cells Divide?
Mitosis – watch this clip on the process of
mitosis and answer the following questions:
1.How are new cells produced?
2.What are chromosomes? Where are they
found?
3.What kind of cells undergo mitosis?
4.What are the only kind of cells that do not
undergo mitosis?
National 4/5 Biology Course Unit 1
Put the following stages of
mitosis in the correct order:
• New nuclear membranes form around the
chromosomes, followed by new cell membranes,
creating two new identical cells.
• Chromosomes replicate to form identical chromatids.
• Spindle fibres then pull the matching chromatids
apart, to opposite poles of the cell.
• The membrane around the nucleus breaks down, and
spindle fibres attach to the chromatids and line them
up in the centre of the cell - equator.
National 4/5 Biology Course Unit 1
Why do chromosomes need to be
copied so carefully and put into each
new cell?
• Chromosomes carry GENES, which are
stretches of DNA.
• Each GENE codes for one protein e.g.
one gene codes for haemoglobin, the
substance in red blood cells that carries
oxygen. Other genes will code for other
molecules that make up the body.
National 4/5 Biology Course Unit 1
Chromosome Complement
• The number of chromosomes that a
species of animal or plant possesses.
• Why so you think it is important that
each new cell has the same chromosome
complement as the parent cell?
National 4/5 Biology Course Unit 1
• During growth and development of an
organism will be able to provide the
animal or plant with all the
characteristics of its species.
• Losing any chromosome would mean a
loss of genetic information – the
information that forms the code
allowing the
cell
function
correctly!
National
4/5to
Biology
Course Unit
1
The Cell Cycle
Second
Growth
Phase
DNA
SynthesisNational
First
Growth
Phase
4/5 Biology Course Unit 1
What happens in each phase?
• First Growth Phase - Cell grows and
increases in mass by adding cytoplasm,
cell membrane and cell wall (if it is a
plant). The materials needed for DNA
replication are made.
• DNA Synthesis phase – DNA is
replicated. We’d see the chromosomes
replicate and become chromatids.
National 4/5 Biology Course Unit 1
• Second Growth Phase - It’s another
period of growth. The cell builds up an
energy reserve to last it through the
rest of the process and proteins
necessary for cell division are made.
• Mitosis Phase – Mitosis takes place and
cell divides.
National 4/5 Biology Course Unit 1
Need for Checkpoints
• We know that it is important that each new
cell produces is identical to the parent cell
and can perform the same function.
• The cell self checks at THREE stages to make
sure that it is ready to proceed.
• If the cell is not ready then it should not
proceed to the next stage and if there is
something wrong then the cell should not
divide at all but should be destroyed!
National 4/5 Biology Course Unit 1
The Cell Cycle
Checkpoint
Two
Second
Growth
Phase
Checkpoint
Three
Checkpoint
One
DNA
SynthesisNational
First
Growth
Phase
4/5 Biology Course Unit 1
What are the checkpoints?
•
•
•
End of First Growth Phase. Checking the Cell
Size – is the cell big enough to continue? Yes –
go to S phase!
End of Second Growth Phase. Has the DNA
been copied correctly? Is DNA replication
complete? Has the cell enough
energy/materials to continue. Yes – can enter
mitosis!
During mitosis, have the chromatids been
pulled apart correctly? Then the cell can
divide!
National 4/5 Biology Course Unit 1
What would happen if the
controls failed?
National 4/5 Biology Course Unit 1
What goes wrong in Cancer?
Decreased
cell death
= more
cells
1
111
1
1 1
2
Increased
cell
division =
more cells
2
22
22
2 3
22
2
2 2
Ability to invade
surrounding tissues
3 33
3
33 33 3
3
33
3
3
3
3 33
3
3 3 3
43
Loss of
contact
inhibition –
the cells no
longer stay
Loss of DNA
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place
Repair
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Ability to move
- metastasis
Escape from immune
surveillance
Course
Unit 1 = cells not
destroyed
Cancer cells – Research Task
1. Find out the meaning of the following terms…
•
Benign
•
Malignant
•
Metastasis
2. Research a type of cancer and find out the following:
•
What part of the body does this cancer affect?
•
What are the clinical symptoms?
•
How common is this cancer (in the UK)?
•
What is the treatment given for this cancer?
•
What research is being done on this cancer?
•
Is there a charity fundraising to help support people
affected by this type of cancer?
National 4/5 Biology Course Unit 1
4. DNA and Protein
Production
Level
What you need to be able to do…
4/5
Explain what is meant by DNA, genes and
chromosomes
5
Describe structure of a nucleotide
5
State the letters which identify the 4 different
bases and how they pair up
5
Explain how the genetic code works
4/5
Explain the structure of proteins
National 4/5 Biology Course Unit 1
What is DNA?
Watch the following video that introduces DNA and its
importance.
DNA video
National 4/5 Biology Course Unit 1
DNA, genes and chromosomes
Chromosomes
The cell’s nucleus contains chromosomes made from long
DNA molecules.
DNA
DNA molecules are large and complex. They carry the
genetic code that determines the characteristics of a
living thing.
Genes
Think back to the last section!
National 4/5 Biology Course Unit 1
DNA, genes and
chromosomes
The diagram shows the relationship between the cell, its
nucleus and the chromosomes in the nucleus that are made
up of DNA, and genes.
DNA
National 4/5 Biology Course Unit 1
Collect the handout sheet and stick it into your jotters.
From Genes to Proteins?
Watch the following video that gives a basic
definition of a gene and what genes do.
What exactly is a gene?
National 4/5 Biology Course Unit 1
DNA Structure
DNA consists of two molecules that are
arranged into a ladder-like structure called a
Double Helix.
A molecule of DNA is made up of millions of tiny
subunits called Nucleotides.
National 4/5 Biology Course Unit 1
Nucleotide Structure
Each nucleotide consists of:
Phosphate
Group
Organic
Base
Deoxyribose
Sugar
Copy this diagram into your jotters.
National 4/5 Biology Course Unit 1
DNA Structure
The phosphate and
sugar form the
backbone of the
DNA molecule,
whereas the
bases form the
“rungs”. Collect
the handout and
stick it into your
jotters.
National 4/5 Biology Course Unit 1
The Genetic Code
The genetic code determines the order in which
amino acids are joined together to produce a
specific protein.
The code itself is determined by the order of the
organic bases in the DNA molecule.
There are 4 different bases.
Guanine Cytosine Adenine and Thymine
National 4/5 Biology Course Unit 1
Each base can only join with one other type of
base:Guanine always pairs with Cytosine
Adenine always pairs with Thymine
G-C
and
A-T
These are called complementary base
pairs.
National 4/5 Biology Course Unit 1
Complementary Base Pairs
National 4/5 Biology Course Unit 1
Build your own DNA
Molecule
Task 1: Collect the handout sheets
DNA origami instructions and template
Follow the instructions to complete your own
model DNA!
National 4/5 Biology Course Unit 1
Protein Structure
Proteins are made up of amino acids.
The order of the amino acids determines
the proteins molecular structure, its shape
and its function.
The order of the amino acids is
determined by the order of the bases in
the DNA molecule – the genetic code.
National 4/5 Biology Course Unit 1
So how does the genetic code get translated
into a protein?
National 4/5 Biology Course Unit 1
Watch Again
Watch the ‘What is DNA?’ video again. This time try to
answer the following questions:- Video
• How is the genetic code from the DNA molecule
copied?
• What happens to the copy of the genetic code?
Where does it go?
• In which organelle is the copy of the genetic code
translated to form proteins?
• How are the National
proteins
4/5formed?
Biology Course
Unit 1
National 4/5 Biology Course Unit 1
Translating the genetic
code
Task 1: Using the information in the video, the questions
and discussion with your teacher write a short paragraph to
describe how the genetic code from the DNA is translated
into a protein.
You could use a
diagram to help
illustrate you
description.
National 4/5 Biology Course Unit 1
Translating the genetic code
The genetic code in the DNA is copied or
transcribed by another molecule called
Messenger RNA (mRNA).
The mRNA carries the code out of the nucleus to
the ribosomes in the cytoplasm.
The ribosomes then translate the code from the
mRNA into the specific protein using amino acids
found free in the cytoplasm.
National 4/5 Biology Course Unit 1
mRNA
The DNA for the gene being turned into a
protein is copied into a mRNA molecule.
It is different from DNA, it is:
• Shorter
• Single stranded
• Have URACIL instead of THYMINE.
National 4/5 Biology Course Unit 1
How does mRNA become a
protein
Every 3 letters in the mRNA tell the
ribosome which amino acid to add to the
protein.
AUGCGAUGGACG
mRNA
Alanine
Serine
Glycine
Proline
National 4/5 Biology Course Unit 1
Translating the genetic
code
Task 3: In groups produce an A4 poster to illustrate
protein synthesis.
Your poster should contain the following information:•
•
•
•
DNA carries the genetic code for producing proteins
mRNA copies the code
mRNA carries the copy of the code to the ribosomes
The ribosomes translate the copy of the code to
produce proteins
National 4/5 Biology Course Unit 1
Glossary of terms
Task 4: Homework – collect the handout
Glossary of Terms – DNA and the production of
proteins.
National 4/5 Biology Course Unit 1
Research Task – Who
Discovered DNA?
Your task is to write an essay or newspaper/magazine article that discusses the
scientists who played significant roles in the discovery of DNA, its structure and
its importance.
You should include:
• James Watson, Francis Crick, Rosalind Franklin, Maurice Wilkins
and Erwin Chargaff and any other scientist you think is important.
• The importance of the roles they played in the discoveries about
DNA, including dates.
• Any special recognition they received (or did not receive) for
their discoveries
Your work should be at least one side of A4 and should contain some
illustrations.
4/5
Biology
Course
1
Your work should beNational
in your own
words
and not
copiedUnit
and pasted
directly from
the web.
5. Genetic Engineering
Level
What you need to be able to do…
4/5
Describe the process of genetic engineering
4/5
List examples of how genetic engineering has been
used
5
Describe what is meant by a GM organism and why it
might be controversial
National 4/5 Biology Course Unit 1
What is genetic
engineering?
What is it used for?
National 4/5 Biology Course Unit 1
Watch the following clip on Genetic
Engineering and in pairs answer the
following questions:
1.What 3 things are produced by
genetically modifying microbes?
2.Name the first organisms to be
genetically modified and when this was
done.
3.What does
insulin
normally
do?1 What
National
4/5 Biology
Course Unit
condition arises from not making insulin?
GMO Defined…
• An organism that is generated through
genetic engineering is considered to be
a genetically modified organism (GMO).
• The first GMOs were bacteria in 1973;
GM mice were generated in 1974.
Insulin-producing bacteria were
commercialized in 1982 and genetically
modified food has been sold since 1994.
National 4/5 Biology Course Unit 1
The process of Genetic
Engineering
• The control of all the normal activities of a
bacterium depends upon its single
chromosome and small rings of genes called
plasmids.
• In genetic engineering pieces of chromosome
from a different organism can be inserted
into a plasmid. This allows the bacteria to
make a new substance.
National 4/5 Biology Course Unit 1
Task 1 – Use the cut out sheet
and put the stages of genetic
engineering in the correct
order.
Use the following diagram to
help you.
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
Uses of Genetic Engineering 1
Genetic engineering is used for the production
of substances which used to be both expensive
and difficult to produce. Examples include:
•insulin for the control of diabetes
•antibiotics such as penicillin
•various vaccines for the control of disease
•enzymes for laundry detergent
National 4/5 Biology Course Unit 1
Uses of Genetic Engineering 2
Genetic engineering is a way of producing
organisms which have genotypes best suited for
a particular function. In the past man has used
selective breeding to achieve this. This was
done by choosing only his most suitable animals
and plants for breeding.
National 4/5 Biology Course Unit 1
Genetic engineering has several advantages over
selective breeding. Some are:
• particular single characteristics can be
selected
• the selection may be quicker
• a desirable characteristic can be transferred
from one species to another
National 4/5 Biology Course Unit 1
Genetic Engineering – now and
the future?
• It is not just bacteria that can be genetically
modified, plants and animals can be modified
too.
• It is therefore possible to genetically engineer
people!
• It holds the promise of curing genetic diseases
like cystic fibrosis, and increasing the immunity
of people to viruses.
National 4/5 Biology Course Unit 1
• It is speculated that genetic engineering could
be used to change physical appearance,
metabolism, and even improve mental faculties
like memory and intelligence, although for now
these uses seem to be of lower priority to
researchers and are therefore limited to
science fiction.
National 4/5 Biology Course Unit 1
Issues?
• There are dangers involved with genetic
engineering since it involves creating
completely new strains of bacteria.
There is a possibility of creating some
which are harmful to animal or plant
life.
• What is your opinion on GM Food (plant
and animal), GM organisms for research
and GM People?
National 4/5 Biology Course Unit 1
Task 2 – Genetically Engineering
the Future
• Thinking about the possibilities and issues
surrounding genetic engineering, I want you to
imagine 50 years from now. Technology has
moved on and GMO is commonplace in
agriculture, medicine and all organisms.
• Write a letter to your present self,
describing this new world. Be honest in this
letter, what are the good and bad points
about GMO in the future?
National 4/5 Biology Course Unit 1
Therapeutic Uses of Cells
- HeLa Cell Line
National 4/5 Biology Course Unit 1
Henrietta Lacks
Listen as your teacher
reads out the poem
“The Life and Life of
Henrietta Lacks” by
Carol Satyamurti.
National 4/5 Biology Course Unit 1
Task 1 – Find out more…using the Fox Thinking
Tool
1. In pairs divide the information sheets about Henrietta Lacks and the HeLa
Cell Line and spend time reading through them.
2. Individually on a piece of paper/card or sticky note write a brief summary of
what you have read
3. Individually on a second piece of paper/card or sticky note write your
opinions of what you have read
4. Talk to your partner to exchange findings and ideas about the section you
have read.
5. Compare your pairs ideas with the rest of your group/table by carrying out a
quick “sweep” of the information that you write down.
6. Stick the summaries and opinions on the poster paper to form a “doughnut”
or ring shape
7. In the middle of “doughnut” give the points (3-5) the group thinks are the
most important
8. Around the outside give the reasons (3-5) why the group thinks these are
most important
•You will then be asked
to use
your
work to
discussUnit
a Key
National
4/5
Biology
Course
1 Question
The story of Henrietta Lacks and the HeLa Cell Line
bring up a lot of issues including:
1. Scientific progress and the possibilities of human
cloning
2. Scientific ethics (the rights and wrongs in how
things are done)
3. The moral and legal aspects of cloning – for example,
if you are cloned, will you be you, or something like
your own child, or a completely new person?
4. Aspects of social history, relating to
– Poverty
– Gender
– Race
National 4/5 Biology Course Unit 1
The Key Question to debate:
Should scientists be free to use
our cells in scientific research
such as in the case of the HeLa
Cell Line?
National 4/5 Biology Course Unit 1
• Further Reading:
The Immortal Life
of Henrietta Lacks
by Rebecca Skloot.
National 4/5 Biology Course Unit 1
6. Proteins and Enzymes
Level
What you need to be able to do…
4/5
Explain what enzymes do and what the main features
of an enzyme are
4/5
Give 3 named examples of chemical reactions carried
out by enzymes and be able to draw the word
equations
4/5
Explain how temperature effects enzyme activity
4/5
Explain how pH effects enzyme activity
4
Describe some uses of enzymes in industry e.g.
Biological detergents and rennet in cheese making
National 4/5 Biology Course Unit 1
Protein structure
• Proteins are made up of sub-units called
amino acids.
• There are 21 amino acids.
• The order of amino acids in a protein is
dictated by the genetic code.
• Every protein has different amino acids
in different orders.
National 4/5 Biology Course Unit 1
• The order of the amino acids affects
the shape of the protein.
• Proteins can be fibrous or globular:
• GLOBULAR – enzymes
• FIBROUS – keratin (hair)
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
Catalysts
A catalyst speeds up a chemical reaction,
but is unchanged in the process and can
be used over and over again.
In living things, catalysts are known as
enzymes.
National 4/5 Biology Course Unit 1
If cells did not have enzymes in their
cytoplasm, then the chemical reactions
which happen in our cells would happen
so slowly that life would be impossible!
National 4/5 Biology Course Unit 1
An example of an enzyme:
CATALASE
Hydrogen peroxide (H2O2) is a liquid
similar to water (H2O), but with one
extra oxygen.
Over a long period of time hydrogen
peroxide naturally breaks down into
water and oxygen.
National 4/5 Biology Course Unit 1
The word equation for this reaction is:
Hydrogen peroxide
water + oxygen
This process can be sped up using an
enzyme.
National 4/5 Biology Course Unit 1
Into each test tube – measure out 5 ml of
Hydrogen peroxide AND 5 drops of
detergent.
CAUTION!!
Hydrogen
peroxide is a
dangerous
chemical.
Safety goggles
must be worn!!
1. Add nothing
2. Potato
3. Carrot
4. Liver
Leave for 10
minutes.
Measure
National
4/5 Biology
Coursethe
Unit
height of the foam bubbles.
1
Test tube contents
Height of foam (mm)
Nothing – “CONTROL”
Potato
Carrot
Liver
National 4/5 Biology Course Unit 1
Conclusion
Only the plant and animal tissues speed up
the breakdown of hydrogen peroxide.
This is because the cells contain catalase.
Catalase is an enzyme found in living
cells.
National 4/5 Biology Course Unit 1
Catalase
Hydrogen peroxide
water + oxygen
The tissue which contained the most
catalase was ______________.
National 4/5 Biology Course Unit 1
Breakdown and Synthesis
Catalase is an enzyme involved in chemical
breakdown.
“Breakdown” means chopping up larger
molecules into smaller molecules.
National 4/5 Biology Course Unit 1
Other enzymes do the opposite – the
build large molecules from smaller
molecules. This is called synthesis.
National 4/5 Biology Course Unit 1
An example of a synthesis
enzyme: Phosphorylase
Glucose-1-phosphate is a chemical made
by plants during photosynthesis. It is
stored in plant cells be converting it
into a large molecule called starch.
National 4/5 Biology Course Unit 1
Phosphorylase
Phosphorylase
Glucose-1-phosphate
Starch
National 4/5 Biology Course Unit 1
Substrates and products
The substrate is the substance the
enzyme works on.
The product is the substance the enzyme
makes.
Enzyme
Substrate
Product
National 4/5 Biology Course Unit 1
Enzyme
Substrate
Product
Catalase
Phosphorylase
Amylase
Pepsin
Lipase
National 4/5 Biology Course Unit 1
How enzymes work
Enzymes are made of protein. This
protein has a special shape which is
unique to each enzyme.
Enzyme
Active site
National 4/5 Biology Course Unit 1
Substrate
Enzyme
The active site is the correct shape to fit the
substrate.
Substrate
Turned into
the products
Enzyme
National 4/5 Biology Course Unit 1
Substrate
Enzyme
Other substrates are the wrong shape to fit in
the active site of the enzyme.
Therefore the enzyme will only work with one
substrate. This is described as being SPECIFIC.
National 4/5 Biology Course Unit 1
“Specific”
When talking about enzymes, SPECIFIC
means that the ENZYME WILL ONLY
WORK WITH ONE SUBSTRATE.
National 4/5 Biology Course Unit 1
One enzyme = one substrate
5 ml Starch
3 ml Water
5 ml Starch 5 ml Starch 5 ml Starch
3 ml Amylase 3 ml Pepsin 3 ml Lipase
Put in waterbath for 10 minutes. Test all 4 test-tubes with
National 4/5 Biology Course Unit 1
Benedict’s Solution
Results
Sugar present?
Starch + water
Starch + amylase
Starch + Pepsin
Starch + Lipase
National 4/5 Biology Course Unit 1
Conclusion
The test-tube containing Starch and
Amylase had the most sugar.
This shows that only Amylase can convert
starch to sugar.
Amylase is said to be SPECIFIC to starch.
National 4/5 Biology Course Unit 1
Effect of temperature on
enzymes
National 4/5 Biology Course Unit 1
5 ml Starch
5 ml Starch
5 ml Starch
3 ml Cold Amylase 3 ml Amylase 3 ml 80oC Amylase
Iced water
37oC
80oC
Put in waterbath
for 10
Test allUnit
3 test-tubes
with
National
4/5minutes.
Biology Course
1
Benedict’s Solution
Temperature
Was sugar present?
0 oC
37 oC
80 oC
National 4/5 Biology Course Unit 1
All enzymes have a temperature at which
the work fastest.
This is called the optimum temperature.
In humans the optimum temperature for
all enzymes is 37oC.
National 4/5 Biology Course Unit 1
Enzymes work slowly at cold
temperatures.
National 4/5 Biology Course Unit 1
At very high temperatures enzymes
become changed and do not work.
This is called being denatured.
Once an enzyme is denatured it will never
work again.
National 4/5 Biology Course Unit 1
The effect of pH on enzymes
Into all 5 test tubes put 5ml Hydrogen Peroxide and 5
drops of soap
3ml pH1 buffer
3ml pH4 buffer
3ml pH7 buffer
3ml pH9 buffer 3ml pH 14 buffer
LAST: Add 1 cm cylinder of potato to each
test tube. Measure height of foam after 10
National 4/5 Biology Course Unit 1
minutes.
Results
pH
Height of foam (mm)
1
4
7
9
14
National 4/5 Biology Course Unit 1
Conclusion
The optimum pH for the catalase enzyme
is pH _______.
All enzymes have a different optimum pH
depending on where they are found in
the body.
National 4/5 Biology Course Unit 1
Uses of enzymes
Yoghurt and cheese making
Biological detergents
Yoghurt and cheese
Yoghurt and cheese making depend on the
activities of enzymes in bacteria.
Bacteria used lactose sugar in milk as a
source of energy.
National 4/5 Biology Course Unit 1
They make the waste product called lactic
acid which makes the milk increasingly
acidic and sour tasting.
Lactose
energy + lactic acid
National 4/5 Biology Course Unit 1
• This is another example of
fermentation.
National 4/5 Biology Course Unit 1
1.
•
•
•
•
Yoghurt making
Milk is heated to kill microbes
Special yoghurt bacteria are added
The lactose in the milk is fermented
by the bacteria.
The milk becomes acidic and so it:
–
–
Thickens
Tastes sour
National 4/5 Biology Course Unit 1
2. Cheese making
The process is similar to yoghurt making,
but after the fermentation, rennet is
added which curdles the milk.
The solid curds are separated from the
liquid whey.
The curds are then pressed into hard
cheese.
National 4/5 Biology Course Unit 1
Task 3 – Note Taking
• The following slides will tell you about biological
detergents; how they are made, why they are
useful and their environmental impact.
• Your task is to take notes from the slides – this
could be mind mapping key words and concepts
under the headings above or a table of
information or bullet point. Decide quickly which
method you find most useful when revising and
try it this way.
National 4/5 Biology Course Unit 1
How Biological Detergents are
produced:
• Biological detergents contain enzymes such as protease,
amylase and lipase to digest proteins, starch and fats
respectively.
• Enzymes can be produced using bacteria that have been
genetically engineered to make these enzymes. They
are grown in industrial fermenters in vast quantities.
This equipment ensures that the bacteria receive food
and oxygen so that they grow well. The bacteria will
produce the enzymes and pass them out into the culture
liquid. The bacteria and the filtered off and the
enzymes extracted from the liquid. The enzymes are
purified and added to washing powder.
National 4/5 Biology Course Unit 1
Value and Use of Product:
• Advantages of using biological detergents
include reducing fuel costs as clothes can be
washed at lower temperatures reducing the
electricity consumption; Less damage to
delicate fabrics such as acrylic and wool
whilst still cleaning effectively and the ability
to remove difficult stains such as grass and
blood. These will be completely removed by
biological washing powder but not by nonbiological even at high temperatures.
National 4/5 Biology Course Unit 1
Environmental Impact 1:
• Reduced Fuel Consumption - using
Biological Detergents has a positive
impact on our environment as it reduces
CO2 and SO2 production from burning
fossil fuels in Power Stations to
generate electricity.
National 4/5 Biology Course Unit 1
Environmental Impact 2:
• Detergents are rich in chemicals called phosphates.
This chemical passes from waste water from people’s
homes to sewage works. Unfortunately it is hard to
remove during processing and can end up in local
rivers where they cause algal bloom. This single celled
plant can overwhelm the balance of the ecosystem
and when it dies can cause bacterial numbers to
increase. The bacteria use up oxygen in the water
which leads to the death of other organisms.
National 4/5 Biology Course Unit 1
Task 3 – Note Taking
• Your task was to take notes from the
slides – it would be useful to check your
notes with a peer. Have you covered
similar key areas?
• If you are not sure, the check with your
teacher!
National 4/5 Biology Course Unit 1
Task 4 – Write a Newspaper
Article
OPTION 1 – Write a newspaper article advocating the Use
of Biological Detergents. This should look favourably on
their usage, highlighting their value rather than any
negative aspect.
OPTION 2 – Write a newspaper article examining the
Environmental Impact of Biological Detergents. In this
option you should be highlighting why people should not
use these and the damage that they can cause.
BE AWARE: Be sure that you justify your argument with
facts and do not make up “facts” to suit your argument!
This task has to be completed for homework.
National 4/5 Biology Course Unit 1
Task
• Create a Summary of
Enzymes. This can be done in
any format you choose; bullet
point notes, mind map,
poster. Before you start
think about how you learn and
what you create should be
suited to your learning style
– do you need colour? Or
pictures? Or real life
examples?
• The summary should include
information about the
following:
• Enzymes are Biological
Catalysts
• Enzymes are protein
• Enzymes are specific (active
site)
• Enzyme activity is affected
by pH and temperature
• They have optimum
conditions and can be
denatured
• Enzymes are used in a variety
of industries including
producing detergents and
making cheese
National 4/5 Biology Course Unit 1
Peer Review
• Check your table and summary with a
peer to check that you have both
covered all the key areas!
National 4/5 Biology Course Unit 1
7. Respiration
Level
What you need to be able to do…
4/5
Explain what cells need energy for
4/5
Write the word equation for aerobic respiration
5
Explain what ATP is and draw its structure
5
Explain how ATP is produced in the cell and how many ATP
are produced for each molecule of glucose
5
Explain what happens during glycolysis
4/5
Describe what is meant by anaerobic respiration
5
Explain what the products of anaerobic respiration are in
humans and yeast
4
Explain how anaerobic respiration can be used to benefit man
(fermentation in yeast – breadmaking and brewing)
4
National 4/5 Biology Course Unit 1
Explain how exercise and training can improve your recovery
time
Why do cells need energy?
National 4/5 Biology Course Unit 1
Respiration
Why do cells need energy?
Living cells need energy to carry out a variety of
cell functions.
cell
division
chemical
reactions
cell
growth
energy in
living cells
nerve
impulses
building
up large
molecules
muscular
contraction
National 4/5 Biology Course Unit 1
energy from food
National 4/5 Biology Course Unit 1
• The three main food groups are _____,
____________, and __________.
• _____ contains the most energy.
National 4/5 Biology Course Unit 1
Aerobic Respiration
Energy in a cell is produced by a chemical
reaction called aerobic respiration.
glucose + oxygen
carbon
water +
dioxide
energy released
National 4/5 Biology Course Unit 1
ATP
The energy produced during aerobic
respiration is stored in a molecule called
ATP (Adenosine triphosphate).
Every molecule of glucose that is “burned”
in the cell produces 38 ATP molecules.
National 4/5 Biology Course Unit 1
ATP structure
ATP is made up of one Adenosine and
three phosphates
High Energy
Bond
ADENOSINE
P
P
3 PHOSPHATE
GROUPS
National 4/5 Biology Course Unit 1
P
ATP is made by joining ADP (Adenosine
diphosphate) and phosphate.
ADP  Pi
ATP
National 4/5 Biology Course Unit 1
• As a molecule to transfer energy in cells
Carbon
Dioxide
+
Water
RESPIRATION
Glucose
+
Oxygen
Energy
ATP
Energy
Energy
ENERGY
TRANSFER
ADP
+
Pi
e.g.
Amino
Acids
WORK
Energy
Protein
molecule
National 4/5 Biology Course Unit 1
Glycolysis
Respiration should be seen as a series of
enzyme controlled reactions in which
•
6-carbon glucose is oxidised (broken
down) to form carbon dioxide
•
this is accompanied by the synthesis of
ATP from adenosine diphosphate (ADP) and
inorganic phosphate (Pi).
National 4/5 Biology Course Unit 1
Glucose (6C)
2ADP + 2Pi
2ATP
Pyruvic Acid
(2x3C)
National 4/5 Biology Course Unit 1
The first stage of respiration is called Glycolysis.
• This process takes place within the cytoplasm.
• does not require oxygen
• involves the step by step breakdown of a 6carbon sugar such as glucose to form two 3carbon pyruvic acid units
Glycolysis results in a production of 2ATP.
National 4/5 Biology Course Unit 1
What happens next?
If there is oxygen available ( the normal
situation), then the pyruvic acid produced
by glycolysis diffuses into an organelle
called mitochondrion for further
breakdown if oxygen becomes available.
National 4/5 Biology Course Unit 1
Structure of a
Mitochondrion
Cristae
Outer Membrane
Inner Membrane
Matrix Fluid
National 4/5 Biology Course Unit 1
• Pyruvic acid from glycolysis diffuses
into central matrix fluid
• Pyruvic acid is broken down further in
the presence of oxygen by a cycle of
reactions called the Kreb’s cycle
releasing most of the 38 ATP produced
during respiration
National 4/5 Biology Course Unit 1
Anaerobic respiration
• If there is no Oxygen- Anaerobic
Respiration occurs.
• Anaerobic respiration occurs in human
after heavy exercise.
National 4/5 Biology Course Unit 1
Pyruvic acid is converted to either
(i) Lactic Acid (in animal and bacterial cells)
(ii) Ethanol and carbon dioxide (in plant and
fungal cells)
• No further ATP is made – so only the net 2
ATPs are produced.
• In animal cells the Lactic Acid is converted
back to Pyruvic Acid when oxygen becomes
available.
National 4/5 Biology Course Unit 1
Complete this summary table
Aerobic
respiration
Anaerobic respiration
Humans
Yeast/Plant
Site in the
cell
Number of
ATP
Final
products
National 4/5 Biology Course Unit 1
Complete this summary table
Aerobic
respiration
Anaerobic respiration
Humans
Yeast/Plant
Cytoplasm
Cytoplasm
Site in the
cell
Cytoplasm &
Mitochondria
Number of
ATP
38
2
2
Carbon
dioxide &
water
Lactic acid
Ethanol &
Carbon
dioxide
Final
products
National 4/5 Biology Course Unit 1
8. Photosynthesis
Level
What you need to be able to do…
4
Explain the importance of plants and give examples of the uses
of named plants e.g. food, raw materials and medicines
4/5
Explain the importance of photosynthesis
4/5
Write the word equation for photosynthesis
4/5
Describe how to test a leaf for starch
5
Explain what happens in the first stage (light reaction) of
photosynthesis
5
Explain what happens in the second stage (carbon fixation) of
photosynthesis
4/5
Label the parts of a leaf
5
Explain the role of the xylem and phloem
4/5
Explain what a limiting factor is
4/5
List the limiting factors for photosynthesis
4
4/5 and
Biology
Coursecontrol
Unit 1the limiting
Describe National
how farmers
gardeners
factors to ensure healthy plant growth
Photosynthesis
 Why are plants important?
 What is photosynthesis?
 What do plants need for
photosynthesis?
National 4/5 Biology Course Unit 1
The importance of plants
National 4/5 Biology Course Unit 1
Raw materials
National 4/5 Biology Course Unit 1
Food
National 4/5 Biology Course Unit 1
Medicines
National 4/5 Biology Course Unit 1
Photosynthesis
Importance of plants
FOOD
RAW MATERIALS
MEDICINES
Wheat – for bread
Wood – for building
Poppy – pain killers
Grapes – for wine
Cotton – for clothes
Foxglove – heart
medicine
Sugar cane – for
sugar
Flowers – for
perfumes
Mint – menthol for
cough sweets
National 4/5 Biology Course Unit 1
Photosynthesis
Green plants make their own food using
light energy
Green plants convert
light energy to
chemical energy (food)
using a green pigment
in the leaves called
chlorophyll.
National 4/5 Biology Course Unit 1
Light energy
- from sun
Glucose
used for energy
or stored as
starch
Carbon Dioxide
taken up from air
Oxygen given
off as waste
Water - from soil
National 4/5 Biology Course Unit 1
This can be summarised by the following
equation
Carbon
Water Light energy Glucose Oxygen
Chlorophyll
dioxide
Raw Materials
Energy
source
and pigment
which
traps it
Products
Glucose is used for
energy, stored as
starch or built up into
cellulose
Oxygen is waste gas
National 4/5 Biology Course Unit 1
What happens to the glucose?
•
Glucose which are used for energy
(respiration)
•
Storage carbohydrates such as starch these can be broken
down to simple sugars if needed
•
Structural carbohydrates such as
cellulose - these are used to build
the cell wall
National 4/5 Biology Course Unit 1
Chloroplast structure
National 4/5 Biology Course Unit 1
Stages of Photosynthesis
biochemistry
• There are two stages of photosynthesis. The
equation you have just learned is actually
more complex and occurs at two separate
stages.
National 4/5 Biology Course Unit 1
Stage 1
• The first stage is called PHOTOLYSIS.
• This stage involves using energy from the
sunlight to split water molecules into
hydrogen and oxygen.
National 4/5 Biology Course Unit 1
WATER
Oxygen
ENERGY
Hydrogen
(ATP)
National 4/5 Biology Course Unit 1
Light energy
Chlorophyll
ADP + Pi
Water
Chemical
energy
ATP
Passed on to
second stage
Hydrogen + Oxygen
Passed on to
second stage
National 4/5 Biology Course Unit 1
Released to the
air as oxygen gas
Stage 2
• The second stage is known as the
Carbon Fixation stage
• Here the energy and hydrogen from
stage one are used along with the
carbon dioxide.
• It is at this stage where glucose
molecules are produced.
National 4/5 Biology Course Unit 1
From the first
stage
Hydrogen
From the first
stage
ATP
ADP + Pi
Glucose
Carbon
dioxide
Enzyme
controlled
reactions
From the air
National 4/5 Biology Course Unit 1
• This stage is energy consuming so that
is where the ATP comes in.
• This stage is also controlled by
enzymes.
• Carbon dioxide and hydrogen join to give
us glucose
National 4/5 Biology Course Unit 1
Leaf cut through
Cut end
magnified
Section4/5
highly
National
Biology Course Unit 1
magnified
National 4/5 Biology Course Unit 1
Cuticle
Upper
Epidermis
Palisade
Mesophyll
Xylem /
Phloem
Spongy
Mesophyll
National 4/5 Biology Course Unit 1
Guard
Cells
Stoma Pore
Stomata
Lower
Epidermis
Light
Glucose
O2
H2O
National
CO 4/5 Biology Course Unit 1
2
Stomata are found on
the bottom surface
Stomata are made
up of special cells
which control the
size of a small
pore
A) Guard cells –
these change
shape and
control the size
of :
B) Pore
Stomata also
control the
exchange of gases
National 4/5 Biology Course by
Unitthe
1 leaf
Guard Cells
The guard cells take in water by osmosis.
They swell more outwards than inwards due to
the size of cell wall.
This pushes back epidermal cells and opens
the pore.
They close by losing water.
National 4/5 Biology Course Unit 1
Part of Leaf
Waxy Cuticle
Epidermis
Function
Waterproof layer prevents
water evaporation
These cells on top and bottom
of leaf are for protection
Palisade Mesophyll
These cells under the upper
epidermis is where
photosynthesis occurs
Spongy Mesophyll
Photosynthesis occur in the
cells and O2 and CO2 can
diffuse through the air
spaces
Stomata
These cells are in the lower
National 4/5 Biology
Course and
Unitlet
1 gases and
epidermis
water in and out.
Limiting factors
Three possible factors can limit the rate of
photosynthesis in a plant when they are in
short supply :-
• Light intensity – this limits the energy
available.
• Carbon dioxide concentration – this is an
essential raw material
• Temperature – this limits the rate at which the
enzymes controlling photosynthesis work.
National 4/5 Biology Course Unit 1
Effect of light on the rate of photosynthesis
We can use the rate of production of oxygen
bubbles by pond weed to measure the rate of
photosynthesis
Diagram “bubbler”
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
• A large water trough or sheet of glass
stops the heat from the lamp from
affecting the experiment.
• Lamp moved away -> less oxygen bubbles
produced
• The amount of light therefore limits the
rate of photosynthesis. It is called a
limiting factor.
National 4/5 Biology Course Unit 1
Increasing rate
of
photosynthesis
Point X Optimum
Increasing light intensity
Part B
Part A
Further increases in light causes
As light intensity
no further increase in the rate of
increases the rate of
photosynthesis since the rate is
photosynthesis
limited by a shortage of some other
National 4/5factor
Biologye.g.
Course
Unit dioxide
1
increases.
carbon
or
temperature
Increasing rate
of
photosynthesis
Point X Optimum
Carbon Dioxide Concentration
Part B
Part A
Further increases in CO2 conc.
As CO2 conc.
causes no further increase in the
increases the rate of
rate of photosynthesis since the
photosynthesis
rate is limited by a shortage of
increases.
National 4/5some
Biologyother
Course
Unit e.g.
1 light or
factor
temperature
Increasing rate
of
photosynthesis
0.4% CO2
0.3% CO2
0.2% CO2
Increasing light intensity
light intensity is
limiting factor
CO2 is limiting factor
National 4/5 Biology Course Unit 1
Increasing rate
of
photosynthesis
Point X Optimum
Increasing temperature
Part A
Part B
As temperature
Further increases in
increases the rate
temperature results in a drop in
of photosynthesis
the rate due to the denaturing
National 4/5of
Biology
Course Unit
1 carry out
increases.
the enzymes
that
photosynthesis
Photosynthesis and horticulture
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
National 4/5 Biology Course Unit 1
Photosynthesis and horticulture
Horticulture is the cultivation of plants in
gardens and greenhouses.
The use of a greenhouse helps remove
limiting factors:
National 4/5 Biology Course Unit 1
(a) Lighting and heat
By increasing the light, the rate of
photosynthesis increases and leads to
an increase in the growth rate of the
crop:
• crop is ready to be picked earlier.
• increased crop yield.
National 4/5 Biology Course Unit 1
(b) Carbon dioxide enrichment
Increased carbon dioxide in the atmosphere
increases the yield (size) of crops. This
happens because the rate of photosynthesis
is increased.
National 4/5 Biology Course Unit 1