Mass Transport in animals

Question 1

Describe the structure and functions of haemoglobins

Answer 1

Haemoglobins are protein molecules whose tertiary structure allows for efficient loading of oxygen under one set of conditions and unloading under another:
primary - order of amino acids joined by peptide bonds;
secondary - alpha helix/beta pleated sheet, hydrogen bonds;
tertiary - specific 3D structure. hydrogen bonds, ionic bonds, disulphide bonds;
quaternary - 4 polypeptide chains;
quaternary - prosthetic haem group;

Question 2

Explain the differences between haemoglobins in different organisms and the reasons for these differences

Answer 2

Different organisms have haemoglobin with different amino acid sequences, therefore, different tertiary and quaternary structures which affects affinity for oxygen

Question 3

association/loading of oxygen

Answer 3

the process by which haemoglobin binds with oxygen

Question 4

dissociation/unloading of oxygen

Answer 4

the process by which haemoglobin releases oxygen

Question 5

Describe and explain the shape of the oxyhaemoglobin dissociation curve

Answer 5

-In low partial pressures haemoglobin has a low affinity for oxygen (dissociates oxygen more easily), the curve is shallow
-Curve becomes steeper as the affinity for oxygen increases
-Curve levels off at nearly 100% saturation at high partial pressures of oxygen - haemoglobin has a high affinity for oxygen (dissociates less easily)

Question 6

Explain how binding of oxygen affects the shape of haemoglobin

Answer 6

-Hard for first oxygen to bind as haem groups are in the middle of the haemoglobin molecule
-First oxygen causes a conformational change in the haemoglobin (change in shape) making it easier for the second and third molecules to bind
-Harder to reach final binding site so fourth oxygen binds less easily

Question 7

Describe and explain the Bohr effect

Answer 7

-Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide.
-This means it loads oxygen less readily and unloads more easily.
-Dissolved carbon dioxide is acidic and this causes haemoglobin to change shape.
-At gas exchange surfaces there is little carbon dioxide, affinity for oxygen in high, oxygen loads readily.
-At respiring tissues carbon dioxide concentration is high, affinity for oxygen is low, oxygen is readily unloaded.

Question 8

Explain how, with reference to haemoglobin, animals are adapted to their environment

Answer 8

An animal that lives in an environment with low partial pressure of oxygen will have haemoglobin with a high affinity for oxygen, the curve is to the left - this allows fully saturated haemoglobin at low partial pressures of oxygen

Question 9

Explain why large animals have a transport system

Answer 9

Large animals have a small SA:volume and therefore have specialed exchange surfaces. Transport system is required to take substances from the exchange surfaces to all of the cells in the body

Question 10

Describe the features of a transport system in large organisms

Answer 10

A medium to carry materials (eg blood).
A form of mass transport to move the medium in bulk.
A closed system of vessels to tranport the medium to all areas of the body.
A mechanism to move the medium in vessels

Question 11

Describe the pattern of blood circulation in a mammal

Answer 11

Closed, double circulatory system. Deoxygenated blood is pumped to the lungs from the heart, oxygenated blood flows back to the heart and then is pumped around the body.

Question 12

What affects whether organisms have a specialised transport medium and whether it is circulated by a pump?

Answer 12

Activity of the organism
SA : volume
Lower SA : volume and higher activity – greater need for specialised system with a pump

Question 13

cardiac muscle

Answer 13

makes up the wall of the heart and is a thick muscular layer

Question 14

properties of cardiac muscle

Answer 14

-myogenic
-never fatigues as long as it has a supply of oxygen

Question 15

coronary arteries

Answer 15

supply the cardiac muscle with oxygenated blood

Question 16

What happens if there is a blockage in the coronary arteries

Answer 16

The cardiac muscle won’t receive oxygen, therefore they won’t be able to respire and the cells will die resulting in a heart attack

Question 17

structure of the atria

Answer 17

-Thinner muscular walls
-Do not need to contract as hard as not pumping blood far (only to ventricles)
-Elastic walls to stretch when blood enters

Question 18

structure of ventricles

Answer 18

-Thicker muscular walls to enable bigger contractions
-This creates a higher blood pressure to enable blood to flow longer distances (to the lungs and the rest of the body)

Question 19

Describe the stage diastole of the cardiac cycle

Answer 19

Diastole:
Atria relaxed - begin to fill with blood
Atrioventricular valves open
Ventricles relaxed - lower pressure, blood enters from atria
Arterial pressure high
Semilunar valves close to prevent backflow of blood

Question 20

Explain how valves control the flow of blood through the heart

Answer 20

Valves prevent backflow of blood. They open when the pressure in front of the valve exceeds the pressure behind the valve and close when pressure behind the valve exceeds pressure in front of the valve

Question 21

Describe the path of blood through the heart

Answer 21

Vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta, body

Question 22

Compare single and double circulation

Answer 22

Single - blood passes through heart once on each circuit of the body. Double - blood passes through heart twice on each circuit of the body

Question 23

why does the left ventricle have a thicker muscular wall than the right ventricle

Answer 23

Left pumps blood to the body and this needs to be at a higher pressure to ensure blood reaches all the cells in the body. Thicker muscular wall enables larger contractions.

The right only has to pump blood to the lungs which needs to be at a lower pressure to prevent damage to the capillaries in the lung and so there is sufficient time for gas exchange

Question 24

Describe how the structure of arterioles are related to its function

Answer 24

Arterioles - take blood to tissues at relatively high pressure:
- muscle layer thicker than arteries to allow constriction of the lumen to control blood flow to tissues
- elastic layer thinner than arteries as blood pressure lower

Question 25

Describe how the structure of arteries are related to its functions

Answer 25

Arteries - take blood at high pressure from the heart:
- muscle layer thicker than veins to allow control of blood volume the structure passing through of arterioles,
- elastic layer thicker than arterioles and veins, stretching and recoiling to allow pressure to be maintained and smoothed
- large overall wall thickness to withstand high pressure and prevent bursting

Question 26

Describe how the the structure of veins is related to its function

Answer 26

Veins - take blood at low pressure from the tissues to the heart:
- muscle layer thin as no need to control blood flow to capillaries
- elastic layer thin as blood under low pressure
small overall thickness as low pressure blood, can also be easily flattened aiding blood flow
- valves prevent backflow of blood

Question 27

Explain the structure of capillaries and how it’s related to their function

Answer 27

Capillaries exchange substances between blood and cells
- thin endothelium only to allow short diffusion pathway
- numerous and highly branched to allow large SA for exchange
- narrow lumen to squeeze red blood cells flat decreasing diffusion pathway
- spaces between endothelial cells allow white blood cells to pass through to tissues

Question 28

Describe the composition of tissue fluid

Answer 28

Tissue fluid contains:
- water, glucose, amino acids, fatty acids, ions and oxygen

Question 29

Explain how tissue fluid is formed

Answer 29

At arterial end of capillary there is high hydrostatic pressure due to pumping of heart
- Water and other molecules forced out of the blood plasma to form tissue fluid (ultrafiltration)
- This lowers water potential of blood as proteins and cells are left behind
- Outward movement is opposed by hydrostatic pressure of tissue fluid and low water potential of the blood, but overall movement is from blood to tissues
- After exchange of materials water and other molecules return to the blood due to the higher water potential and hydrostatic pressure in the tissue fluid
- Excess water and molecules returned to the blood via the lymphatic system

Question 30

Describe the advantage of the Bohr effect during intense exercise

Answer 30

-Increased unloading of oxygen
-For aerobic respiration at respiring tissues

Question 31

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin.

Answer 31

• Haemoglobin has a lower affinity for oxygen
  -By increasing the acidity

Question 32

Describe the stage atrial systole in the cardiac cycle

Answer 32

Atrial Systole:
Atria contract - higher pressure
Ventricles relaxed - lower pressure
Atrioventricular valves open
Blood flows from atria to ventricles

Question 33

Describe the stage ventricular systole in the cardiac cycle

Answer 33

Ventricular Systole:
Ventricles contract - higher pressure
Atria relaxed - lower pressure
Atrioventricular valves close to prevent backflow of blood
Semilunar valves open
Blood flows from ventricles to arteries