3.4 - Mass transport in animals

Question 1

What is haemoglobin?

Answer 1

• water soluble globular protein (quaternary structure)
• each molecule can carry 4 O2 molecules

Question 2

What is the role of haemoglobin and red blood cells in oxygen transport?

Answer 2

bind to O2 and carry molecules

Question 3

Describe the loading, transport and unloading of oxygen by haemoglobin relative to the oxyhaemoglobin dissociation curve

Answer 3

Left:
- haemoglobin has a higher affinity for O2
- so associates with O2 molecules easily
- forming oxyhaemoglobin

Right: (Bohr effect) - haemoglobin has a lower affinity for O2
- so dissociates from O2 molecules more readily

Question 4

Describe the cooperative nature of oxygen binding to haemoglobin

Answer 4

• haemoglobin molecule undergoes conformational change to tertiary structure after binding of 1st O2
• breaks H bonds
• becomes easier for subsequent molecules to bind
• creates another binding site

Question 5

Describe the effect of CO2 concentration on the dissociation of oxyhaemoglobin

Answer 5

• Bohr effect
• decreases pH
• O2 dissociates from haemoglobin more readily as has a lower affinity for O2

Question 6

Does haemoglobin differ between animals?

Answer 6

yes, they are adapted to their environment with different types + different transport properties

Question 7

Draw a labelled diagram of the structure of the heart (including valves) and blood vessels and highlight the flow of blood

Question 8

Name the blood vessel which supplies oxygen and glucose to the heart muscle

Answer 8

coronary artery

Question 9

Describe precautions to take during/after a dissection

Answer 9

• carry sharp instruments pointed away from body
• disinfect instruments and surfaces
• wash hands with soap and water before and after
• dispose of organ in separate bag
• use sharp scalpel
• wear gloves
• cover any cuts

Question 10

Explain how an artery can reduce blood flow into capillaries

Answer 10

• muscle contracts
• narrows lumen

Question 11

Explain how an atrioventricular valve maintains a unidirectional flow of blood

Answer 11

• pressure in atrium is higher than in ventricle
• so valve opens
• pressure in ventricle is higher than in atrium
• so valve shuts

Question 12

Describe the structure and function of arteries

Answer 12

• elastic fibres allow walls to stretch following ventricular systole
• smooth endothelial lining reduces friction of blood flow
• narrow lumen and thick muscular walls maintain the high pressure so blood can be pushed far distances around the body
• thick smooth muscle layer exerts a high pressure during contraction

Question 13

Describe the structure and function of arterioles

Answer 13

same as artery but:
- smaller, thinner muscle wall and elastic layer

Question 14

Describe the structure and function of veins

Answer 14

• wider lumen than arteries for blood to flow at lower pressures
• thin muscle wall and elastic tissue
• valves prevent backflow of blood

Question 15

Describe the structure of capillaries and the importance of capillary beds as exchange surfaces

Answer 15

• one cell thick and narrow lumen for short diffusion distance
• highly branched capillary network for large surface area

Question 16

Describe how tissue fluid forms and how it is returned to the circulatory system

Answer 16

• contraction of ventricle produces high hydrostatic pressure
• forces water out of capillaries
• proteins remain in blood vessel
• creates water potential gradient
• water moves into blood by osmosis
• returns by lymphatic system

Question 17

How does the aorta maintain rate of blood flow?

Answer 17

elastic recoil of wall

Question 18

What are the common features of a circulatory system?

Answer 18

• suitable medium
• means of moving medium
• mechanism to control flow around body
• closed system of vessels

Question 19

Describe the stages of the cardiac cycle

Answer 19

cardiac diastole:
- atria and ventricles relax
- elastic recoil lowers pressure inside heart chambers
- AV valves open
- blood flows into atria
(NB: aorta pressure > ventricle pressure)

atrial systole:
- atria contract forcing blood into ventricles

ventricular systole:
- ventricles contract
- AV valves shut
- semi-lunar valves open
- blood leaves (LV via aorta, RV via pulmonary artery)

Question 20

Explain the importance of a small increase in pressure at the same time as a small increase in rate of blood flow in aorta

Answer 20

• maintains high pressure
• elastic recoil

Question 21

What causes a heart attack?

Answer 21

• coronary arteries clogged
• thickens blood

Question 22

Describe how an atheroma can block blood flow in artery

Answer 22

• atheroma (fatty deposit buildup, made from cholesterol) clogs artery
• artery walls damaged and burst open
• platelets transported to damaged part and accumulate there, causing formation of thrombus, blocking blood flow in artery as lumen narrows