Exam specific answers

Question 1

explain the advantages of lipid droplet and micelle formation. (3)

Answer 1

lipids droplets have an increased surface area for lipase to act on
therefore there is faster hydrolysis of lipids
micelles carry monoglycerides and fatty acids through the membrane

Question 2

suggest how the Golgi apparatus is involved in the absorption of lipids. (3)

Answer 2

it modifies triglycerides
it combines triglycerides with proteins
it packages the triglycerides for release by exocytosis

Question 3

suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own. (2)

Answer 3

exopeptidases hydrolyse the peptide bonds at the ends of peptide molecules
therefore, using endopeptidases creates more ends for the exopeptidase to act on

Question 4

describe the processes involved in the absorption and transport of
digested lipid molecules from the ileum into lymph vessels. (5)

Answer 4

micelles contain bile salts and fatty acids/monoglycerides
micelles bring the fatty acids and monoglycerides to the lining of the ileum
the fatty acids and monoglycerides are absorbed by diffusion
the triglycerides are reformed in cells
vesicles move to the cell membrane

Question 5

describe the role of micelles in the absorption of fats into the cells lining the ileum. (3)

Answer 5

1. micelles carry fatty acids to cells lining ileum
2. they maintain a high concentration of fatty acids to the cells lining the ileum
3. fatty acids are absorbed into cells by diffusion

Question 6

explain why a bacterium can rely on diffusion for gas exchange, but animals need a transport system. (3)

Answer 6

animals have a smaller surface area to volume ratio than bacterium
the diffusion distance is larger in animals
diffusion would not supply enough oxygen for the volume of the animal

Question 7

explain why oxygen uptake is a measure of metabolic rate in organisms. (1)

Answer 7

the oxygen is used in respiration which is a metabolic process

Question 8

describe how humans breathe in and out. (5)

Answer 8

inspiration:
diaphragm contracts and flattens
external intercostal muscles contract and ribcage is pulled up
this causes a volume increase and pressure decrease below atmospheric pressure in the thoracic cavity

expiration:
diaphragm relaxes and moves up
external intercostal muscles relax and ribcage moves down
this causes a volume decrease and pressure increase above atmospheric pressure in the thoracic cavity

Question 9

explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. (3)

Answer 9

tracheoles have thin walls so short diffusion distance

large number of tracheoles creates large surface area for diffusion

fluid in the end of the tracheoles moves into tissues during exercise, meaning there is a faster diffusion through the air to the gas exchange surface