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 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