exchange of substances

Question 1

explain the advantage of larger animals having a specialised system for oxygen uptake

Answer 1

1. large animals have a smaller surface area:volume ratio
2. overcomes long diffusion pathway

Question 2

explain the higher metabolic rate of a smaller animal compared to a larger one

Answer 2

• small animals have larger SA:V ratio
• more heat loss
• faster rate of metabolism releases heat

Question 3

describe the relationship between size and surface area to volume ratio

Answer 3

as size increases, ratio decreases

Question 4

explain why oxygen uptake is a measure of metabolic rate in organisms

Answer 4

oxygen used in respiration which provides energy

Question 5

explain how the countercurrent flow allows efficient oxygen uptake in fish

Answer 5

• blood and water flow in opposite directions
• concentration gradient maintained along length of lamella

Question 6

describe and explain the mechanism that causes lungs to fill with air

Answer 6

• diaphragm contracts and external intercostal muscles contract
• causes volume increase and pressure decrease
• air moves down pressure gradient

Question 7

explain why the death of alveolar epithelium cells reduces gas exchange

Answer 7

• reduces surface area
• increased diffusion distance
• reduces rate of gas exchange

Question 8

describe the gross structure of the human gas exchange system and how we breathe in and out

Answer 8

• trachea, bronchi, bronchioles, alveoli
• breathing in- diaphragm contracts and external intercostal muscles contract
• causes volume increase and pressure decrease in thoracic cavity
• breathing out- diaphragm relaxes and internal intercostal muscles contract
• volume decrease and pressure increase in thoracic cavity

Question 9

explain three ways an insects tracheal system is adapted for efficient gas exchange

Answer 9

1. tracheoles have thin walls so short diffusion pathway
2. body can be moved by muscles so maintains oxygen and carbon dioxide diffusion gradient
3. highly branched so large surface area

Question 10

explain how the countercurrent flow in fish ensures the maximum amount of oxygen passes into the blood

Answer 10

• water and blood flow in opposite directions
• blood always passing water with a higher oxygen concentration
• diffusion gradient maintained throughout length of gill

Question 11

describe the processes involved in the absorption and transport of digested lipid molecules from the oleum into lymph vessels

Answer 11

1. micelles contain bike salts and fatty acids
2. maintain higher concentration of fatty acids to ileum lining
3. fatty acids absorbed by diffusion
4. triglycerides reformed
5. vesicles move to cell membrane

Question 12

describe the role of micelles in the absorption of fats into the cells lining the ileum

Answer 12

• micelles include bike salts and fatty acids
• make fatty acids more water soluble
• bring fatty acids to ileum lining
• maintain higher concentration of fatty acids to ileum
• fatty acids absorbed by diffusion

Question 13

describe the role of enzymes in the digestion of proteins in a mammal

Answer 13

• hydrolysis of peptide bonds
• endopeptidase act in the middle of polypeptide
• exopeptidase act at end of polypeptide
• dipeptidase act on dipeptide between two amino acids

Question 14

explain the advantages of lipid droplet and micelle formation

Answer 14

1. droplets increase surface area for lipase to work on
2. so faster hydrolysis
3. micelles carry fatty acids through membrane to cell

Question 15

how is the golgi apparatus involved in the absorption of lipids?

Answer 15

• modifies triglycerides
• combines triglycerides with proteins
• packages for release