Topic 7 - Mass Transport

Question 1

Red blood cells contain enzymes, but these enzymes cannot be replaced. Why?

Answer 1

No ribosomes for protein synthesis.
No golgi apparatus to modify the proteins.
No mitochondria to release ATP

Question 2

For primary, secondary, tertiary, and quaternary level of protein structure, explain:

General protein structure
and
Protein structure in haemoglobin.

Answer 2

Primary - sequence of amino acids.
Two alpha and two beta polypeptide chains.

Secondary - Alpha helix and B pleated sheets (joined by hydrogen bonds).
Each polypeptide is coiled into a helix.

Tertiary - 3D shape, joined by disulfide bridges, hydrogen and ionic bonds.
Each polypeptide chain is folded into a precise shape.

Quaternary- Each polypeptide chain is associated with a haem group containing a ferrous iron (Fe+2). All 4 polypeptides are linked to form a spherical shape.

Question 3

How many oxygen molecules can each human haemoglobin molecule carry?

Answer 3

4

Question 4

What is the role of haemoglobin?

Answer 4

To transport oxygen from the lungs to the respiring tissues.

Question 5

What is ‘Affinity’?

Answer 5

An attraction between molecules that results in the formation of a new molecule.

Question 6

Why do large organisms need a transport system?

Answer 6

In small animals that have a large SA:V, they can supply oxygen and nutrients and get rid of waste with just diffusion. Larger animals have a small SA:V so diffusion is too slow to meet the needs. Therefore, they need a transport system to carry all they need to and from the exchange surfaces (it’s a long distance).

Question 7

What determines whether a transport system needs a pump?

Answer 7

• The surface area to volume ratio.
• How active the organism is.

Question 8

Describe why:
Water
A closed system
A mechanism for moving transport medium
Unidirectional flow
and Controlling the flow rate
is important in mammalian transport systems.

Answer 8

• Readily dissolves substances and moves around easily.
• Forms a branching network to distribute transport medium around organism.
• Within vessels - moves it around faster than diffusion.
• Maintains the mass flow movement in one direction.
• To suit changing needs of different parts of the organism

Question 9

Why is a closed, double circulatory system important in mammals?

Answer 9

• When blood is passed through lungs, pressure is reduced.
• Low pressure would cause slow circulation.
• Instead, blood returns to the heart and pressure increases before being circulated.
• Substances are delivered to parts of the body quickly.

Question 10

Starting from the left side, label the heart.

Answer 10

1) Aorta
2) Pulmonary veins
3) Left atrium
4) Atrioventricular valve
5) Left ventricle
6) Septum
7) Tendon
8) Papillary muscle
9) Right ventricle
10) Atrioventricular valve
11) Right atrium
12) Semi-lunar valve
13) Pulmonary artery
14) Vena cava

Question 11

How does blood flow through the human heart?

Answer 11

The right side receives deoxygenated blood from the body and pumps it through the pulmonary circulation so that the haemoglobin can be oxygenated. The left side receives oxygenated blood from the lungs and pumps it through the aorta to the systemic circulation.

Question 12

What is diastole?

Answer 12

Semi-lunar valves are closed, preventing the backflow of blood into the ventricles. The pressure in the atrium exceeds that of the ventricles, so the atrioventricular valves are open.

Question 13

What is astrial systole?

Answer 13

The walls of the atria contract simultaneously, blood is forced into the ventricles. During this stage the muscular walls of the ventricle are relaxed.

Question 14

What is ventricular systole?

Answer 14

The ventricle walls contract. The AV valves are forced shut and are prevented from inverting by the tendinous chords. The pressure in the ventricles exceeds the blood vessels. Pressure in aorta and pulmonary artery exceeds ventricles so the semi-lunar valves close and prevent any backflow.

Question 15

Why is the maximum ventricular pressure greater than atrial pressure?

Answer 15

Ventricle has a thicker wall of muscle that can contract more, thus has more pressure.

Question 16

1) When the left ventricle pressure exceeds atrium, the —– valve —–?
2) When the pressure in the ventricle is higher than the aorta, the — valve —-?
3) When the pressure in ventricle decreases, the —– valve ——?
4) When the ventricle pressure is less than the atrium, the —– valve ——?

Answer 16

1) AV Valve closes
2) Semi-lunary valve opens
3) Semi-lunar valve closes.
4) AV valve opens.

Question 17

What is cardiac output?

Answer 17

Volume of blood pumped by one ventricle in one minute.

Question 18

How do you calculate cardiac output?

Answer 18

Heart rate x stroke volume

Question 19

What are the functions for:
Artery
Arterioles
Capillaries
Veins

Answer 19

• Main transporters of oxygenated blood, limit blood flow to certain organs.
• Diameter is adjusted to regulate blood flow.
• Diffusion occurs across thin walls, tiny vessels that link arterioles to veins.
• Carry blood from capillaries back to the heart.

Question 20

Does the elastic tissue of arteries stretch and recoil or contract or relax?

Answer 20

Stretch and recoil - it is not a muscle!

Question 21

How is the thick muscle layer of an artery related to its function?

Answer 21

Can constrict and dilate to control volume of blood passing through.

Question 22

How is the thick elastic layer of an artery related to its function?

Answer 22

Blood pressure needs to be kept high. Elastic wall stretched at systole and springs back at diastole. Helps maintain blood pressure and smooth pressure surges.

Question 23

How is the thick wall of an artery related to its function?

Answer 23

Resists the vessel bursting under pressure.

Question 24

How does the aortic semi-lunar valve relate to the artery’s function?

Answer 24

To stop blood flowing backwards.

Question 25

How is the thick muscle layer of the arterioles related to its function?

Answer 25

Restricts flow of blood and controls its movements into capillaries that supply tissues with blood.

Question 26

How is the thin elastic layer of the arterioles related to its function?

Answer 26

Blood pressure is lower, doesn’t need thick walls.

Question 27

How is the thin muscle layer of the veins related to its function?

Answer 27

Carry blood away from tissues, constriction and dilation cannot control blood flow to tissues.

Question 28

How is the thin elastic layer of the veins related to its function?

Answer 28

Low blood pressure - will not cause them to burst, too low to create recoil action.

Question 29

How is the thin wall of the veins related to its function?

Answer 29

Pressure in veins is low, no risk of bursting. Also allows them to be flattened, aiding flow of blood.

Question 30

How are the valves present in the veins related to its function?

Answer 30

Ensures blood does not flow backwards as pressure is low. Veins compress when muscles contract, pressurising the blood - these valves ensure it travels towards the heart.

Question 31

How are the walls being only one cell thick in capillaries related to their function?

Answer 31

Allows for diffusion.

Question 32

How does the number of capillaries relate to their function?

Answer 32

Many of them - increased SA.

Question 33

How does the spaces between the endothelial cells relate to the capillaries function?

Answer 33

Highly permeable - allows substances to pass.

Question 34

What is hydrostatic pressure?

Answer 34

Capillaries are narrower than the arterioles so pressure builds up which forces water out of blood plasma.

Question 35

What is ultrafiltration?

Answer 35

Pressure pushes water and small molecules out of capillary leaving cells and large proteins behind.

Question 36

How does tissue fluid return to the circulatory system?

Answer 36

• Most water is returned to blood plasma via capillaries.
  1) Loss of water from capillaries at arteriole end reduces hydrostatic pressure inside them.
  2) Hydrostatic pressure at venule end of capillary higher outside, water is forced in.
  3) Osmotic forces pull water back into capillaries as WP in capillary at venule end is lower.
  4) Remaining tissue fluid enters lymph vessels - drain back into the veins close to the heart.

Question 37

How is water transported up the xylem?

Answer 37

1) Water evaporates from leaves.
2) Water molecules form hydrogen bonds between one another, stick together via cohesion.
3) Water forms continuous unbroken column.
4) As water evaporates in leaves, water molecules drawn up xylem as result of cohesion.
5) Column of water is therefore pulled up xylem by transpiration - transpiration stream.
6) Places xylem under negative pressure so there is tension within xylem - cohesion-tension theory.

Question 38

What is some evidence to support cohesion-tension theory?

Answer 38

• Changes in diameter of tree trunks according to rate of transpiration.
• If xylem vessel is broken and air enters, tree can no longer draw up water because column is broken.

Question 39

How is a potometer used?

Answer 39

1) Leafy shoot cut underwater.
2) Potometer filled with water.
3) Leafy shoot fitted to potometer.
4) Potometer removed and all joints sealed with waterproof jelly.
5) Distance moved by air bubble in given time is measured a few times and mean is calculated.
6) Once air bubble nears junction of reservoir tube and capillary tube, tap on reservoir is opened and syringe is pushed down until bubble is pushed back to start of scale.

Question 40

How is sucrose transferred from photosynthesising tissue into sieve tube elements?

Answer 40

1) Hydrolysis of ATP used to make H+ ions out of companion cell.
2) H+ conc. in source increases, makes conc. gradient for H+.
3) H+ flows down conc. gradient into companion cell. Cotransport - sucrose is carried too.
4) Conc. of sucrose increases in companion cell.
5) Sucrose carried into sieve tube by facilitated diffusion.

Question 41

How does sucrose and organic matter move through the phloem via mass transport? SOURCE

Answer 41

1) Sugars made at source. Moved by active transport into phloem cells (via companion cells).
2) WP in phloem decreases.
3) Water moves via osmosis from xylem to phloem.
4) Hydrostatic pressure in phloem increases.

Question 42

How does sucrose and organic matter move through the phloem via mass transport? SINK

Answer 42

1) Sucrose unloaded (involves active transport).
2) WP in phloem increases.
3) Transpiration pull in xylem.
4) Water moves from phloem into xylem.
5) Hydrostatic pressure is low.

Question 43

How are sieve cells adapted for mass transport?

Answer 43

Have thick walls which leads to more flow due to strong walls being able to resist high pressure.

Question 44

How are companion cells adapted for transport of sugars between cells?

Answer 44

Companion cells have mitochondria which release energy.

Question 45

Describe the ringing experiment.

Answer 45

1) Section of outer layer of stem removed around circumference.
2) Area above missing ring swells.
3) Samples of liquid rich in sugar.
4) Some non-photosynthetic tissues below ring die - bits above swell.
5) Conclusion = phloem and not xylem that transports organic substances around plant.

Question 46

How does the tracer experiment provide evidence for translocation?

Answer 46

1) Plants supplied with radioactive CO2.
2) Incorporated into glucose during photosynthesis.
3) Sugars can be tracked as they move through plant (autoradiography).
4) Results used to show organic substances are transported in phloem.
5) Shows transport is bi-directional.