Module 3

Question 1

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

Answer 1

• higher hydrostatic pressure in the capillaries than tissue fluid
• fluids leaves capillaries via pores in endothelium lining of capillaries
• low hydrostatic pressure in venule end of capillary
• low water potential in the venule end of capillary
• large proteins remain in the blood
• water moves into venule end by osmosis
• excess tissue fluid drained by lymphatic system

Question 2

Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions

Answer 2

• elastic tissues stretch under pressure
• this evens out blood flow
• muscle contracts to reduce diameter
• this changes blood flow
• smooth epithelium
• reduces friction

Question 3

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

Answer 3

• micelles contain bile salts, fatty acids and monoglycerides
• this makes fatty acids and monoglycerides more soluble in water
• micelles bring fatty acids to the cell
• this maintains a higher conc of fatty acids to cell
• fatty acids absorbed by diffusion
• golgi reform triglycerides
• chylomicron is formed
• vesicles carry chylomicron to the membrane and are released by exocytosis
• enter lacteal system

Question 4

Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse

Answer 4

• mouse is smaller so it has a larger surface area to volume ratio
• more heat loss
• faster rate of respiration releases heat

Question 5

Describe how water is moved through a plant according to the cohesion-tension hypothesis

Answer 5

• water evaporates from the leaves through stomata
• reduces water potential in mesophyll cells
• water is drawn out of xylem
• creates tension
• cohesive forces between water molecules- hydrogen bonding
• adhesion between water molecules and wall of xylem vessels
• water pulled up as a column

Question 6

Describe a method this student could have used to prepare colour standards

Answer 6

• use known concentration of (contextualise eg: solvent)
• make a dilution series
• compare results with the colour standards