Transcript 9.2.2 Plant and Animals transport dissolved nutrients and gases in a fluid medium.

9.2.2 Plant and Animals transport
dissolved nutrients and gases in a
fluid medium
Aim – Tuesday 30th October
• Aim – To be able to describe the structure of
the mammalian transport system & relate the
structure of arteries, capillaries and veins to
their function
• REF: Pg. 50-54, KISS Pg. 14 – 16, Handouts
REVISION: Gas Exchange
• Our cells require a constant supply of
oxygen for respiration. Carbon dioxide, a
waste product of respiration must be
excreted.
• The process of “swapping” oxygen for
carbon dioxide is called gas exchange – it
occurs in the alveoli of the lungs
Gas Exchange
Gas Exchange
Gas Exchange:
Alveoli
Gas exchange
Gas exchange takes place in the alveoli – oxygen is transferred
into the blood and carbon dioxide moves out of the blood.
Each alveolus has a thin wall so that gas exchange between
the lungs and the blood can take place quickly.
Gas exchange
Gas exchange takes place in the alveoli – oxygen is transferred
into the blood and carbon dioxide moves out of the blood.
Each alveolus has a thin wall so that gas exchange between
the lungs and the blood can take place quickly.
RBC’s and Haemoglobin
• The haemoglobin in the red blood cells
picks up oxygen to form oxyhaemoglobin.
• When the RBC’s reach the cells where
oxygen is needed, oxygen is released from
the oxyhaemoglobin and diffuses into the
body cells.
• At the same time, CO2 (a waste product)
diffuses into the plasma of the blood to be
carried back to the lungs to be excreted.
THE HEART
• The human circulatory system is described
as a double circulation. The blood travels
through the heart twice on each complete
journey around the body. The right side
pumps blood to the lungs to collect
oxygen. The left side pumps oxygenated
blood around the body. Deoxygenated
blood then returns to the right side of the
heart to be sent to the lungs again.
THE HEART
THE HEART
LUNGS:
Gas
exchange
TASK
1. Make a list to show the order
in which the blood flows
around the body using the
words in the pink box:
Left atrium→Left Ventricle→
2. Which side of the heart is the
thickest? Why?
3. Where do the pulmonary
artery & vein lead to & from?
4. Why are there valves in the
heart?
♥♥♥
Pulmonary artery
Pulmonary vein
Left Atrium
Right Atrium
Left Ventricle
Right Ventricle
Aorta
Vena Cava
♥♥♥
Blood Vessels: Arteries
• Carry blood away from the heart
• Have more oxygen than the blood in veins
– except for the pulmonary artery which is
going to the lungs to be re-oxygenated
• Have thick, elastic walls to withstand high
blood pressure
• The blood moves in pulses due to the
pumping action of the heart
Blood Vessels: Arteries
Arteries & Athlerosclerosis
Blood Vessels: Veins
• Carry blood back to the heart
• Carry deoxygenated blood
• Have thin walls because the blood is not
pressurised
• Muscles around the veins contract to help
move the blood back towards the heart
• Veins have one-way valves to stop blood
flowing backwards
Veins & Valves
Artery vs. Vein Structure
Thick muscular & elastic wall –
gradually reduces the harsh surge of
blood to a steadier flow
Larger Lumen (space in
middle) – less resistance to
blood flow
Blood Vessels: Capillaries
• Join arteries to veins
• Very tiny blood vessels that reach all the
cells of the body – thin permeable walls
• Capillaries provide cells with “food”,
oxygen & water and remove wastes like
carbon dioxide
Blood Vessels: Capillaries
Capillaries & transfer of
materials
Heart Disease
• To get the energy to keep pumping your heart
needs food and oxygen (for respiration)
• It gets the food & oxygen from its own blood
supply carried by the coronary arteries
• If these arteries get blocked it leads to heart
disease
Cholesterol
• Fatty substance that sticks to the inside walls
of an artery making them narrower
• This slows the blood down
• If blood vessels get blocked completely it is
called thrombosis and blood flow is stopped
Hypertension
• High Blood Pressure
• This happens when blood vessels are
partly blocked by cholesterol
• The heart has to pump much harder to
push the blood through = higher pressure
on the blood vessels
STROKE
• A thrombosis in a blood vessel in the brain
is called a stroke
• Brain cells die because they have no
oxygen
• A person who has a stroke may become
paralysed or even die
Angina
• If a coronary artery
gets partially
blocked, the heart
muscle gets too little
food and oxygen
• This results in severe
chest pains called
angina
HEART ATTACK
• A thrombosis in the coronary artery can
cause a heart attack
• This is when the heart stops beating
• “CLEAR” – but with the right treatment the
heart can be forced to start beating again
Causes of Heart Disease
• Smoking
• Being overweight
• Eating too much cream, butter, eggs, fat or
fried foods = high cholesterol in the blood
• Not exercising enough
• Being stressed (worry, angry, fear)
Avoiding Heart Disease
• Cut down on fried food
– Boil, steam or grill food instead
• Eat less red meat
– Eat more poultry (chicken) and fish
• Eat less dairy
– Eat more vegies and fruit and nuts
• Do NOT smoke
• Exercise regularly (20 min a day minimum!)
• Relax! Don’t get too stressed out – chill out!
Aim – Thursday 1st November
• Aim – To review the composition of blood and
to identify the forms in which key substances
are carried in mammalian blood
• REF: Pg. 34 – 43, KISS Pg. 14 - 16
Composition of Blood
Blood
Composition of Blood
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•
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Dsfjk – RBC’s
Erythrocytes
Leucocytes – WBC’s
Dsfjk
Thrombocytes - Platelets
Plasma
Blood
Red Blood
Cell
REVISION: RBC’s
• Bi-concave discs, anucleate, 7µm
Red Blood Cells – 45% blood
• Aka erythrocytes = very small, 7µm diameter
• Anucleate, biconcave disk shape to increase
surface area: volume ratio for oxygen
absorption (also no mitochondria or ER)
• Contain haemoglobin (gives red colour) which
functions to transport oxygen from lungs to
respiring tissues
• Fetal RBC’s are formed in the liver, then bone
marrow takes over after birth
Structure: Haemoglobin
• Large, conjugated protein
– protein part (globin) &
– prosthetic group (haem
group)
• Protein part contains 4
polypeptide chains; 2
alpha, 2 Beta
Osmosis & Red Blood Cells
Leucocytes (WBC’s)
White Blood Cells < 1%
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Leucocytes; all have a nucleus
Produced in bone marrow
Function – immune system; protect body
Larger than RBC’s – approx 10um
Not as abundant as RBC’s in blood volume
Level of WBC’s is elevated in leukaemia and
infections
Blood Smear
Platelets
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Aka thrombocytes
Cell fragments, produced in bone marrow
Half size of RBC’s approx 3-4um
Function is to clot the blood – form scabs
Plasma
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Yellow, watery fluid part of blood
90% water, 10% protein
55% volume of the blood
Carries many substances dissolved or suspended
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Plasma proteins eg. Clotting factors, antibodies
Nutrients eg. Amino acids, glucose, fatty acids
Gases eg. O2 and CO2
Waste products eg. Urea, ammonia
Ions eg. Sodium, Magnesium
Hormones
TASKS – Text Pg. 40-43
• Use the Textbook to identify the form in which
each of the following is carried in mammalian
blood:
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–
–
Carbon dioxide
Oxygen
Water
Salts
Lipids
Nitrogenous wastes
Other products of digestion
Chemicals in Blood
Chemical
Form carried in blood
Carbon dioxide
70% transported as bicarbonate ions in the plasma,
7% dissolved in plasma & 23% combines with haemoglobin
oxygen
Most combines reversibly with haemoglobin to form
oxyhaemoglobin: Hb + 4O2  HbO8
water
Carried as the liquid solvent of blood plasma
Salts
Travel as ions (charged particles) eg Na+, K+, Cl- and HCO3-
lipids
Transported as micelles in the lymphatic system as a colloid
(suspension-like) then they are processed to form chylomicrons,
they eventually rejoin blood supply
Nitrogenous wastes
Ammonia, urea, uric acid and creatinine are dissolved in the
plasma
Other products of
digestion
Glucose (simple sugars), amino acids and nucleotides are
dissolved in plasma
Aim – Friday 2nd November
• Aim – To be able to outline the need for
oxygen in living cells, why the removal of CO2
is essential and explain the adaptive
advantage of haemoglobin
• REF: Pg. 43 - 45
Need for O2 & Removal of CO2
• Oxygen necessary for cellular respiration to release
ENERGY from glucose
• Energy is needed for growth, repair, movement,
excretion & reproduction – that is energy is needed
to sustain LIFE!
6O2 + C6H12O6  6CO2 + 6H2O + ATP (energy)
• Carbon dioxide is produced as a waste product of
respiration and must be removed to prevent a
change in pH levels which would alter homeostatic
balance (enzyme functioning)
Structure: Haemoglobin
• Large, conjugated protein
– protein part (globin) &
– prosthetic group (haem
group)
• Protein part contains 4
polypeptide chains; 2
alpha, 2 Beta
Haemoglobin
• Oxygen is carried around the body by
haemoglobin
• Each chain has a haem group which contains
iron (giving it its red colour)
• Has a high affinity for oxygen – each molecule
can carry 4 oxygen molecules (4 x O2) to
become oxyhaemoglobin. This is a reversible
reaction where oxygen dissociates from it near
body cells: Hb + 4O2 → HbO8
Haemoglobin and Diet
• Iron is regularly lost from body in waste
products (faeces/urine) so must be part of a
balanced diet
• Lack of iron – anaemia
• Too much iron – haemochromatosis –
genetically inherited disease
Adaptive Advantage of Haemoglobin
1. It increases the oxygen-carrying capacity of the blood
2. Its ability to bind oxygen increases once the first oxygen
molecule binds
3. Its capacity to release oxygen increases when carbon dioxide
is present (pH is lower) (that is oxygen pressure is low & cells
need more). It has a reduced affinity for oxygen at a lower
pH, releasing O2 where it is needed (Bohr shift)
4. It has the increased ability to pick up CO2 when it releases O2
& vice versa (eg. In lungs/tissues)
5. It is enclosed in RBC so it doesn’t upset osmotic balance of
the plasma
Haemoglobin Saturation
• Haemoglobin saturation depends on the
partial pressure of oxygen (pO2)
• pO2 is a measure of oxygen concentration
(greater the concentration of dissolved O2
cells = higher pO2)
• Haemoglobins affinity for oxygen varies
depending on pO2, so at high pO2 oxygen
loads onto haemoglobin, and oxyhaemoglobin
unloads its oxygen where there’s a lower pO2
Oxygen dissociation curve
• There is a relationship between haemoglobin
saturation & oxygen partial pressure which is
shown by the oxygen dissociation curve:
Oxygen Dissociation Curve
• The first oxygen molecule to combine, alters the
shape of haemoglobin making it easier for the next
molecule to join, and so on.
• The same thing happens in reverse: it becomes
progressively harder for the oxyhaemoglobin to give
up its oxygen
• These facts account for the ‘S-shape’ curve: a small
increase in pO2 in the alveoli causes blood to become
rapidly saturated with O2, & a small drop in oxygen
level of respiring tissues will result in oxygen being
readily unloaded
The Bohr Effect
• As with all proteins, haemoglobins
conformation is sensitive to pH
• A drop in pH (more acidic) lowers the affinity
of haemoglobin for O2 – this is called the Bohr
shift
• Because CO2 reacts with water to form
carbonic acid, an active tissue will lower the
pH of its surroundings & induce haemoglobin
to give up more O2 to be used in respiration
Graph – Bohr Shift
Additional O2 is released
from haemoglobin at
lower pH (higher CO2
concentration)
1.
2.
3.
Lets imagine a cell with
an oxygen tension of
30mmHg
At high PCO2 (80mmHg),
haemoglobin is less
saturated (30%) – it
releases its O2 more
readily
At low PCO2 (20mmHg),
haemoglobin is still 75%
saturated, and releases
O2 less readily
Aim – Friday 2 November
• Aim – To perform a first-hand investigation to
demonstrate the effect of dissolved CO2 on
the pH of water
• REF: Pg. 45 – 47
• PRAC LESSON
STILL TO DO
• Aim – To perform a first-hand investigation
using the light microscope to estimate the size
of red and white blood cells AND draw scaled
diagrams of each
• REF – Pg. 37-39
HOMEWORK TASK
• Analyse information from secondary sources
to identify current technologies that allow
measurement of oxygen saturation and
carbon dioxide concentrations in blood and
describe & explain the conditions under which
these technologies are used
• REF – Pg. 47 - 50
Thursday 15th November
• Aim – To be able to describe current theories
about the processes responsible for the
movement of materials through plants in
xylem & phloem tissue
• REF – Pg. 64 – 67, KISS 19- 20
Redwood
• Need for a
transport
system???
Multicellular plants need a transport
system
• Plant cells need substances like water,
minerals and sugar to live
• They need to get rid of wastes
• Multicellular plants have a small surface
area:volume ratio
• Exchange of substances by direct diffusion
would be too slow so plants need transport
systems to move substances to/from cells
quickly
Transport Tissue in Plants
• Two types of tissue:
– Xylem tissue transports water and mineral ions
– Phloem tissue transports dissolved substances like
sugars
• Both are found throughout the plant – they
transport materials to ALL parts
• Where they are found in each part is
connected to the xylem’s other function support
Distribution of phloem & xylem
1. In a root, the xylem and phloem are in the
centre to provide support for the root as it
pushes through the soil
Distribution of phloem & xylem
1. In the stems, the xylem and phloem are near
the outside to provide a sort of “scaffolding”
that reduces bending:
Distribution of phloem & xylem
• In a leaf, the xylem and phloem make up a
network of veins which support the thin
leaves
Overview:
• Distribution of
vascular bundles
in roots, stems
and leaves.
Xylem Tissue
• Xylem is a tissue made from several different
cell types; Vessel elements & tracheids, fibres &
parenchyma cells
• Xylem tissue has 2 functions; support &
transport
Xylem Vessel
• Long, tube-like structures formed from cells (xylem
elements) joined end-end
• No end walls = uninterrupted tube
• Dead cells – no cytoplasm
• Walls thickened with woody substance called
lignin for support
• Amount of lignin increases as cell gets older
• Water & ions move in & out of the vessels through
small pits in the walls where there’s no lignin
Xylem Vessels
Pits
Phloem Tissue
• Transports solutes
• Like xylem, formed from
cells arranged in tubes
• Purely for transport –
no support function
• Phloem tissue contains
phloem fibres,
parenchyma, sieve tube
elements & companion
cells
Phloem Tissue : Sieve tube elements
1. Living cells, joined end-toend, that form the
transport tube
2. “Sieve parts” are the endwalls which have lots of
holes to allow solutes
through
3. Although living, sieve tube
cells have no nucleus, few
organelles & a very thin
layer of cytoplasm
Phloem
Phloem Tissue : Companion Cells
•
The lack of nucleus & other organelles in sieve tube
elements means they can’t survive on their own
•
•
So, there’s a companion
cell for every sieve tube
element
Companion cells carry out
living functions for both
themselves & their sieve
cells eg. they provide the
energy (ATP) for the active
transport of solutes
Plasmodesmata
• Numerous
plasmodesmata pass
through the cell
walls of both the
companion cell &
Plasmodesmata
sieve tube making
direction contact
between their
cytoplasms
Plasmodesmata
Phloem: Sieve tube & Companion cell
Sieve
elements:
No nuclei,
ribosomes or
tonoplast
Companion
Cells: actively
transport
sugars in/out of
the sieve tubes
via
plasmodesmata
Water enters a plant through its root hairs
• Root hairs have a large surface area to
increase the absorption of water from the soil
• Once its absorbed, water travels through the
root cortex & endodermis to reach the xylem
Soil to Root Hair
• Water moves from an area of high water
potential to areas of low water potential – it
goes DOWN a water potential gradient
• The cell sap has a lower water potential than
the surrounding soil, so water moves into the
root hair cell by osmosis
Root Hair to Xylem
• Water can take two possible routes through
the cortex cells to the xylem:
Transport between cells
Apoplast Pathway
• Water moves from cell wall to cell wall
through intercellular spaces or directly
between adjacent cells
• When transpiration rates are high, more water
travels this way
Symplast Pathway
• Water moves into the cytoplasm or vacuole
for a cortical cell and then into adjacent cells
through interconnecting plasmodesmata
Casparian Strip
• Impenetrable barrier to water in the walls of
the endodermis cells:
• Formed by waxy band
of suberin in cell walls
• This blocks the
apoplast pathway
From Roots to Leaves
• Water moves up a plant from the roots to the
leaves in the transpiration stream, against gravity.
• The mechanisms that move the water include
– Cohesion and tension
– Adhesion
– Root pressure
Refer to page 131 – 133 Text
Cohesion-adhesion-tension Theory
(Transpiration Stream theory)
• Cohesion and tension help to transport water
from the roots to leaves against gravity:
1.Water evaporates from the leaves at the “top”
of the xylem through transpiration stream
2.This creates tension (suction) which pulls
more water into the leaf (think of a straw)
3.Water molecules are cohesive (stick together
H-bonding) so a column of water moves
upwards through the xylem
From roots to leaves
Adhesion
• Adhesion is also partly responsible for the
movement of water from the roots to leaves
1. As well as being attracted to each other,
water molecules are attracted to the xylem
vessel walls
2. This helps water rise up through the xylem
vessels
Root Pressure
• Root pressure also helps move the water up
1. When water is transported into xylem in the
roots, this creates a pressure that shoves
water already in the xylem upwards
2. This pressure is weak, and is not significant in
most plants, but is significant in small plants
still developing leaves.
REFER TO PG. 133 TEXT
Water movement through leaf
1. Water moves up the xylem vessels
2. Water leaves a xylem vessel through a pit – it
may enter the cytoplasm of cell wall of a
mesophyll cell
3. Water evaporates from the cell wall into an air
space
4. Water vapour diffuses from air space through
open stoma
5. Water vapour is carried away from the leaf
surface by air movements
DO NOW
• Match the term with the correct explanation
Term
Explanation
Symplast route
Water moves from root hair to
xylem via the tonoplast then
through the sap vacuole of each
cell
Water moves from root hair to
xylem via the cytoplasm of the
cells via plasmodesmata
Water moves from the root hair
to xylem via the cell walls of
adjacent cells
Apoplast route
Vacuolar route (symplast)
DO NOW - Answers
Term
Explanation
Symplast route
Water moves from root hair to
xylem via the cytoplasm of the
cells via plasmodesmata
Water moves from the root hair
to xylem via the cell walls of
adjacent cells
Apoplast route
Vacuolar route (symplast) Water moves from root hair to
xylem via the tonoplast then
through the sap vacuole of each
cell
Transpiration is a consequence of Gas
Exchange
• It is an inevitable consequence of gas
exchange because stomata need to be open to
allow entry of CO2 for photosynthesis.
• Inside leaf = higher concentration of water
than the air outside the leaf, so water
DIFFUSES down the water potential gradient
Water evaporates from surface of mesophyll cells
first, then diffuses out through stomata
Stomatal Opening
OSMOSIS
Overview: Water transport
in plants
Factors affecting Transpiration Rate
1. Light Intensity – lighter = faster, stoma open in
light for photosynthesis & close in darkness
2. Temperature – higher = faster
3. Humidity – lower = faster
4. Wind Speed – windier = faster
TASK: Temperature, humidity and wind all
alter the water potential gradient. Light
does not. Explain. (5 minutes)
Xerophytes & Transpiration
• Xerophytic plants are adapted to reduce water
loss eg. cacti, pine trees & prickly pears
• Adapted to dry climates – to avoid losing too
much water by transpiration
Xerophyte - Cactus
Xerophytic adaptations
Stomata are sunk in
pits – sheltered from
the wind, helps slow
transpiration
Reduced
number of
stomata –
fewer places
for water
loss
Thick, waxy cuticle on
epidermis –
waterproof to reduce
evaporative water loss
Layer of ‘hairs’ on the epidermis –
traps moist air round the stomata –
reduces the water potential
gradient between the leaf & air,
slowing transpiration
Curled leaves – traps moist
air. Also lowers the exposed
surface area for losing water
& protects stomata from
wind
Spines instead of leaves (eg. cactus) –
reduces surface area for water loss
TASK - Questions
1. Explain why transpiration is a consequence of
gaseous exchange
2. What piece of apparatus is used to measure
transpiration?
3. What is a xerophyte?
4. Suggest 3 ways that xerophyte leaves are
adapted to reduce water loss by transpiration
Tuesday 20 November
• To be able to explain the transport of
materials in phloem: translocation by the
pressure flow theory (aka Mass Flow or
Source-Sink Theory)
• REF: Text Pg. 66-67, KISS Pg. 20, Handouts
Translocation
• Translocation is the movement of dissolved
substances (aka assimilates) eg. sugars like
sucrose & amino acids to where they’re
needed in a plant.
• It is an energy-requiring process that happens
in the phloem
• Translocation moves substances from
‘sources’ to ‘sinks’
Translocation & Mass Flow
• Areas in a plant where sucrose is
loaded into the phloem are called
sources
• The usual source of sucrose is the
photosynthesising leaf
• Areas where sucrose is removed
from the phloem are known as
sinks
• Sucrose is removed from the
phloem to form starch in the root.
Example:
• Sinks
– food storage organs et. Potato,
carrot,
– meristems (areas of growth) of
the root, stems and leaves
– Fruit eg. apple
Translocation & Enzymes
• Enzymes maintain a concentration gradient
from the source to the sink by changing the
dissolved substances at the sink into
something else.
• This ensures there is always a lower
concentration at the sink than the source
Mass Flow Hypothesis
• The Mass Flow hypothesis best explains
phloem transport:
1. Active transport is used to actively load
solutes into the sieve tubes of the phloem at
the source
2. This lowers the water potential inside the
sieve tubes, so water enters by osmosis
3. This creates a high pressure inside the sieve
tubes at the source end of the phloem
Mass Flow Hypothesis
4. At the sink end, solutes are removed from the
phloem to be used up
5. This increases the water potential inside the
phloem sieve tubes so water leaves the tubes by
osmosis & joins xylem
6. This lowers the pressure inside the phloem sieve
tubes
7. The result is a pressure gradient from the source to
the sink. This pushes solutes along the phloem sieve
tubes to where they’re needed!!
Mass Flow Hypothesis
TASK - Cut & Paste
• Cut the 10
statements out
and arrange them
in order to
explain the
process of
translocation
shown
Cut & Paste - ANSWERS
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•
•
•
•
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•
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1. Source produces organic molecules
2. Glucose from photosynthesis produced
3.Glucose converted to sucrose for transport
4. Companion cell actively loads the sucrose
5. Water follows from xylem by osmosis
6. Sap volume and pressure increased to give Mass flow
7. Unload the organic molecules by the companion cell
8. Sucrose stored as insoluble starch
9. Water that is released is picked up by the xylem
10. water recycles as part of transpiration to re supply the
sucrose loading
TASK
• You are given the
following picture –
you must write a
description of what is
happening at each
number 1-4
• You have 7 minutes
Answers
• Use this to
check your
answers
Translocation - Homework
1. Explain the terms source and sink in connection
with translocation
2. The mass flow hypothesis depends on a
pressure difference in the phloem and sieve
tubes between the source and the sink. Explain
how sugars cause the pressure to increase at the
source end, according to the mass flow
hypothesis