9.2.2 plant and animals transport dissolved nutrients and gases in a fluid medium
TRANSCRIPT
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 ExchangeGas Exchange: Alveoli
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
Gas exchange
the lungs and the blood can take place quickly.
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
Gas exchange
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 arteryPulmonary vein
Left AtriumRight AtriumLeft Ventricle
Right VentricleAorta
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
Larger Lumen (space in middle) – less resistance to
blood flow
Thick muscular & elastic wall – gradually reduces the harsh surge of
blood to a steadier 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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• Erythrocytes – RBC’s• Leucocytes – WBC’s• 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%
• 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
• 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• Yellow, watery fluid part of blood• 90% water, 10% protein• 55% volume of the blood• Carries many substances dissolved or suspended
– 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:– Carbon dioxide– Oxygen– Water– Salts– Lipids– Nitrogenous wastes– Other products of digestion
Chemicals in BloodChemical 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 blood2. Its ability to bind oxygen increases once the first oxygen
molecule binds3. 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. Lets imagine a cell with an oxygen tension of 30mmHg
2. At high PCO2 (80mmHg), haemoglobin is less saturated (30%) – it releases its O2 more readily
3. 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-to-end, that form the transport tube
2. “Sieve parts” are the end-walls 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
Phlo
em
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 & sieve tube making direction contact between their cytoplasms
Plasmodesmata
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 up1. 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 leaf1. Water moves up the xylem vessels2. Water leaves a xylem vessel through a pit – it may
enter the cytoplasm of cell wall of a mesophyll cell3. Water evaporates from the cell wall into an air
space4. Water vapour diffuses from air space through open
stoma5. Water vapour is carried away from the leaf surface
by air movements
DO NOW
• Match the term with the correct explanationTerm Explanation
Symplast route Water moves from root hair to xylem via the tonoplast then through the sap vacuole of each cell
Apoplast route Water moves from root hair to xylem via the cytoplasm of the cells via plasmodesmata
Vacuolar route (symplast) Water moves from the root hair to xylem via the cell walls of adjacent cells
DO NOW - Answers
Term ExplanationSymplast route Water moves from root hair to
xylem via the cytoplasm of the cells via plasmodesmata
Apoplast route Water moves from the root hair to xylem via the cell walls of adjacent cells
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
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OSMOSIS
Factors affecting Transpiration Rate
1. Light Intensity – lighter = faster, stoma open in light for photosynthesis & close in darkness
2. Temperature – higher = faster3. Humidity – lower = faster4. 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
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
Thick, waxy cuticle on epidermis –
waterproof to reduce evaporative water loss
Spines instead of leaves (eg. cactus) – reduces surface area for water loss
Reduced number of stomata –
fewer places 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 up5. This increases the water potential inside the phloem sieve tubes so water leaves the tubes by osmosis & joins xylem6. This lowers the pressure inside the phloem sieve tubes7. 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
• 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 - Homework1. Explain the terms source and sink in connection
with translocation2. 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