Transcript The Building Blocks of Life: Cells

The Building Blocks of Life:
Cells
History of Cells
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Until recently, the oldest fossils on earth were
little more than 600 million years old.
The world is estimated to be 4.5 billion years
old.
Within the last few years, the electron
microscope has allowed scientists to discover
that life may have possibly existed 3.5 billion
years ago.
Fleas, whales, flowers and Douglas firs all
come from the same single ancestral cell.
History of Cells
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Every human spent about half an hour as a
single cell
Every square inch of the human body has an
average of 32 million bacteria on it.
The History of the Cell: Part II
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By the early 1800s improvements to the
microscope allowed scientists to investigate
structures within a cell.
These improvements led to the development
of the cell theory
Using an electron microscope, scientists can see
things that are 0.0000001m in size.
Bacteria on the head of a pin.
Here is a fly…up close
The Cell Theory
Three Parts:
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2.
3.
All living things are made up of one or more
cells.
The cell is the functional unit of life.
All living cells come from pre-existing cells.
The Theory
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Before the development of this theory people
believed that living things could come from
non-living things. (i.e. insects from a raindrop)
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Seeing that the cell theory was uniform
scientists could look for a general explanation
of life processes as opposed to looking at the
life processes of specific organisms.
A Cell
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Think of a cell as self-contained city.
The city imports certain materials to maintain
itself.
It also exports certain materials that it
produces.
There is a central control of the city
(Municipal Hall, Provincial Government)
Specific parts of the city have specific
functions.
Common features of all cells
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They all have a cell membrane (this is what
encloses a cell)
They all have a cytoplasm (the interior fluid of
all cells)
They all have DNA in them
Cell Membrane
Cytoplasm
DNA
How DNA is held in a cell
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Some cells have their DNA free in the
cytoplasm
These kind of cells are the most primitive and
simple
Most cells have their DNA enclosed in a
membrane.
These are more advanced and complex
cells.
Primitive Cells
Advanced Cells
DNA free in the cytoplasm
DNA inside the nucleus
Cells are very small
Cells are larger
Very few other structures
Many other structures
Examples : Bacteria
Examples : Plant and
Animal cells
Prokaryotic Cells
Eukaryotic Cells
Science 9 Review (woo-hoo!)
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Cells need nutrients to grow and repair
Where do these nutrients come from?
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DIGESTION!
What parts of the cell are you already familiar
with? (hands up!)
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Can you recall their function?
The cell membrane
• A phospholipid bi-layer composed of 50%
phospholipids and 50% embedded proteins.
Phospholipids…
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Phospholipids are the
main structural
components of
membranes
They each have a
hydrophilic head and
two hydrophobic tails
Draw one and label
Cell Membrane
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In water, phospholipids form a stable bilayer
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The heads face outward and the tails face inward
DRAW IT!!
Three main functions of cell membranes
1. The cell membrane is the outer boundary of
the cell.
2. The cell membrane is selectively permeable
and controls what enters and leaves a cell.
3. Recognition markers on the outside of the
cell membrane are for cell to cell
identification.
The Brain: The nucleus
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The largest organelle.
Separated from the
cytoplasm by the
nuclear membrane.
The nucleus is the
‘brain’ of the cell: it
contains the DNA, and
controls the cell
activities.
The nucleus and the nuclear membrane
Chromatin and the nucleolus
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Chromatin
long strands of DNA
(genetic information)
that float around within
the nucleus.
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The nucleolus
a dark area within the
nucleus where
ribosomes are made.
NUCLEUS
Chromatin
Nucleolus
Nuclear
membrane
Pore
DRAW IT!!
More about Cells….The Cytoplasm
Cytoplasm:
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All the contents of a cell, including the plasma
membrane, but not including the nucleus.
“Soupy” mixture that contains a variety of cell
structures called organelles.
Rough Endoplasmic Reticulum (RER)
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continuous with the
nuclear membrane
ribosomes attached at tiny holes
(making it ‘rough’)
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The function of the Rough Endoplasmic
Reticulum is to synthesize and export
proteins and glycoproteins.
NUCLEUS
Chromatin
Nucleolus
Nuclear
membrane
Pore
ROUGH
ENDOPLASMIC
RETICULUM
Ribosomes
Smooth endoplasmic reticulum
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connected to the RER
(and nucleus), but has
no attached ribosomes
smooth ER makes
lipids (fat)
DRAW IT!!
Products leave the ER in vesicles:
Vesicle
buds off from ER
Ribosome
Protein inside
vesicle
Protein created
DRAW
DRAWIT!!
IT!!
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ROUGH ER
Vacuole
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In plant cells, vacuoles are larger, act as
storage areas, and help regulate water
When vacuoles fill with water, they get larger
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The vacuole pushes against the cell wall
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What happens to a plant cell when this takes
place?
The firmness makes veggies crisp and plants
stand up!
In animal cells, vacuoles are called
vesicles…
Vesicles
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Vesicles have a simple structure.
Liquid filled sacs surrounded by a single
membrane.
Package liquids containing a wide variety of
substances and carry these materials to other
parts / outside of the cell.
Vesicles also form around material (liquid or
solid) that are brought into the cell.
Vesicles are the shipping containers within
cells.
Ribosomes
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Where proteins are synthesized.
May be free, or attached to the RER.
Where the information that DNA contains is
transformed into protein.
Lysosomes
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Contain digestive enzymes
Digest worn out organelles, food particles,
viruses and bacteria
Cell janitors – keep the cytoplasm clean
The Golgi complex
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the Golgi complex is a stack of membranous
sacs, like a stack of pancakes
these receive and modify products of the ER,
then send them on to other organelles or to the
cell membrane.
think of it like a distribution company, with a
“shipping and receiving” function
The Golgi complex
Golgi apparatus
“Receiving” side of
Golgi complex
Vesicle
from ER
New
vesicle
forming
“Shipping”
side of Golgi
complex
Transport vesicle
from the Golgi
Mitochondria
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The “power-house” of the cell.
This is the structure where cellular respiration
occurs. (i.e. where food is converted into
energy)
In everyday language:
glucose (sugar) + oxygen  carbon dioxide +
water + energy
The mitochondrion (mitochondria)
Note: Double
Membrane
Note: Folds/Creases
Cell appendages
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Cilia: thin, tail-like projections that beat in one
direction or have sensory functions
Flagella: long, whip-like projection used for
movement
Plant vs Animal Cells…Round 1
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Animal cells have centrioles
Centrioles are protein fibres that aid cell
division by helping to move chromosomes
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Animal cells take round 1!
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Plant vs Animal Cells…Round 2
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Plant cells have a cell wall
The cell wall protects that plant cell and helps
maintain the cell’s shape
Made of cellulose
Plant cells take round 2!
Round 3…the final blow
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Chloroplasts are found in plant cells only
They carry out photosynthesis, which
converts sun’s energy into nutrients
Carbon dioxide + water + sunlight  glucose
+ oxygen
Without chloroplasts, we would have no
oxygen and no sugar
What makes plants green?
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Ok, smarty pants…
Why are plants green?
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Chloroplasts contain chlorophyll, which
absorbs sunlight
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If chlorophyll is green, then what colors of
light (ROYGBIV) do they absorb?
Common structures in plant and
animal cells:
Organelles found in plant cells
Cell wall – made of cellulose,
gives cell strength and
protection
Larger vacuoles – store
water and keep cell rigid
Chloroplasts – make sugar
from CO2 and sunlight photosynthesis
Organelles found in animal cells
Centrioles – attachment
for the cytoskeleton,
organise spindle fibres
during cell division
IMPORTANT SLIDE!!!
Plant Cells
Animal cells
Have a cell wall
Do not have a cell wall
Have chloroplasts
Do not have chloroplasts
Have large vacuoles
Have small vacuoles
No visible centrioles
Centrioles visible