Topic 3.4 - Mass transport in animals

Question 1

How does the binding of the first oxygens to haemoglobin affect the affinity of haemoglobin?

Answer 1

· 1 Oxygen molecule binds to haemoglobin;

· This alters tertiary structure of Hb;

· Leads to another binding site/ haem group being uncovered

· This increases the affinity of Hb to Oxygen (so it’s easier for the 2nd and 3rd molecules of oxygen to bind)

· This is called cooperative binding

Question 2

Describe the structure of haemoglobin. Why do we say it has quaternary structure?

Answer 2

It is a protein made of 4 polypeptide chains (two alpha chains and two beta chains)

Each polypeptide chain has a heme group which is where the oxygen molecule binds.

(One haemoglobin molecules can hold up to 4 oxygen molecules)

It has a quaternary structure because it is made of more than 1 polypeptide chain

Question 3

What is the function of the coronary arteries?

Answer 3

To supply blood to the heart muscle

Question 4

What is the equation for cardiac output?

Answer 4

Cardiac output (cm3min-1) = stroke volume (cm3) x heart rate (min-1)

Question 5

How else can you calculate heart rate?

Answer 5

Heart rate = 60 / time taken for one cardiac cycle

Question 6

Describe and explain the function of each layer. (Blood vessels)

Answer 6

Elastic tissue

· Elastic tissue stretches when pressure is high (during ventricular systole)

· Recoils during ventricular diastole

· This evens out pressure (so that pressure surges are reduced) and maintains smooth blood flow

Muscle

· Muscle contracts;

· This reduces the diameter of the lumen (this is called vasoconstriction)

· This reduces the amount of blood that can flow through the vessel (and increases the pressure)

Epithelium

· the epithelium is smooth

· This reduces friction so that there is less resistance and reduced chance of blood clots

Question 7

Explain why people who lack protein in their diet often accumulate tissue fluid which leads to swelling

Answer 7

· The lack of protein means that the water potential (in capillary) is not as low as it should be (it is less negative)

· Therefore the water potential gradient is reduced;

· Therefore more tissue fluid is formed at arteriole end (because more water leaves the capillaries and moves into the tissue fluid)

· And less water is absorbed from the tissue fluid into the blood capillary by osmosis

Question 7

Describe how tissue fluid is formed and how it returns to the circulatory system

Answer 7

· At the arterial end:

o The Hydrostatic pressure is higher in the capillary than the tissue fluid

o The hydrostatic pressure is higher than the osmotic pressure

o Therefore water (and substances dissolved in water) are forced out of the capillaries and into the tissue fluid

· At the venous end

o The hydrostatic pressure is much lower in the capillary (due to loss of fluid) than at the arterial end

o The total water potential is lower in the capillary at the venule end than at the arterial end (and also lower in the capillary than in the tissue fluid) due to large soluble proteins which remain in the blood vessel

o Therefore the osmotic pressure (pulling water in) is greater than the hydrostatic pressure

o So water is returns to the capillary from the tissue fluid by OSMOSIS

· Excess water in the tissue fluid is taken up by the lymph capillaries which return it to the circulatory system at the subclavian vein

Question 8

Write an equation to show the reversible reaction between haemoglobin and oxygen

Answer 8

Haemoglobin + oxygen ->
oxygaemoglobin