Exchange Exam Qs

Question 1

Why might mitochondria be found close to the cell surface membrane in larger cells?

Answer 1

Larger cells have a smaller surface area to volume ratio
So it takes longer for oxygen to diffuse to mitochondria as diffusion pathway longer

Question 2

What is the advantage of larger animals having a specialised system to facilitate oxygen uptake

Answer 2

Larger organisms have smaller surface area: volume ratio
So specialised system overcomes long diffusion pathway

Question 3

Describe how environmental conditions result in gills (system on outside of body)

Answer 3

Water has lower oxygen partial pressure/ concentration
So outside system gives large surface area in contact with water
Water is denser than air, so water supports the systems/ gill

Question 4

Why does a mouse have higher metabolic rate than a horse

Answer 4

Mouse smaller so has larger surface area to volume ratio
Mouse has faster heat loss than horse in relation to body size
So faster rate of respiration releases heat

Question 5

Describe the relationship between size and surface area to volume ratio of organisms

Answer 5

As size increases, surface area to volume ratio decreases

Question 6

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

Answer 6

Oxygen is used in respiration WHICH is a metabolic process/ chemical reaction

Question 7

Tubifex worm have no specialised gas exchange or circulatory system.

Name the process by which oxygen reaches the cells inside the body of a tubifex worm

Answer 7

Simple diffusion

Question 9

Describe and explain one feature of reg alveolar epithelium well adapted as a surface for gas exchange
(Don’t refer to surface area or gas exchange)

Answer 9

Single layer of flattened cells
Reduces diffusion pathway
Permeable
So allows diffusion of oxygen/ carbon dioxide

Question 10

Tidal volume = volume of air inhaled and exhaled

How would reduced tidal volume affect the exchange of co2 between blood and alveoli

Answer 10

Less co2 exhaled out of lung
So reduced concentration gradient between blood and alveoli
So less movement of co2 out of blood/ more stays in blood.

Question 11

Explain how the counter current principle allows efficient oxygen uptake in the fish gas exchange system

Answer 11

Blood and water flow in opposite directions
Concentration gradient maintained along the lamella

Question 12

Describe and explain the mechanism that causes the lungs to fill up with air

Answer 12

Diaphragm muscle contracts and external intercostal muscles contact
Causes volume increase and pressure decreases
Air moves down a pressure gradient, enters from higher atmospheric pressure

Question 13

Why does a scientist stain lungs with haematoxylin solution (stains DNA blue) rather than iodine (stains starch blue black)

Answer 13

Animal/ lung tissue does not contain starch
Haemotoxylin makes nucleus visible

Question 14

Explain why death of alveolar epithelium cells reduces gas exchange in the human lungs

Answer 14

Reduced surface area, increased distance for diffusion
Reduced rate of gas exchange

Question 15

Describe and explain the advantage of the counter current principle in gas exchange across a fish gill

Answer 15

Water and blood flow in opposite directions
Maintains diffusion gradient of oxygen, oxygen conc always higher in water
So diffusion can occur along whole length of lamellae

Question 16

Suggest and explain one way the leaf growth of xerophytic plants would be different from the leaf growth of sunflowers

Answer 16

Lower and slower growth due to smaller number of stomata for gas exchange
OR
Growth can continue at low water potentials due to adaptations involved in photosynthesis

Question 17

Why do plants grown in soil with very little water grow slowly

Answer 17

Stomata close to retain water
Less carbon dioxide taken up
So less photosynthesis
So less glucose produced for growth

Question 18

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

Answer 18

Across alveolar epithelium
Of capillary

Question 19

Explain how one feature of an alveolus allows efficient gas exchange to occur

Answer 19

Alveolar epithelium is one cell thick
So creates a short diffusion pathway

Question 20

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

Answer 20

• Name structures in correct order: trachea, bronchi, bronchioles, alveoli
• breathing in- diaphragm contracts and external intercostal muscles contract
  causes volume to increase and pressure decrease in thoracic cavity
  pressure decreases to below atmospheric pressure, resulting in air rushing in
• breathing out- diaphragm relaxes and internal intercostal muscles relax and lung tissues elastic so recoils
  causes volume decrease and pressure increase in thoracic cavity
  to above atmospheric pressure so air rushes out

Question 21

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

Answer 21

• tracheoles have thin walls so short diffusion distance to cells
• highly branched/ large number of tracheoles so large surface area for gas exchange
• trachea provide tubes full of air so enable fast diffusion
• fluid in the end of tracheoles that moves out into tissues during exercise so faster diffusion through air to gas exchange surface
• body can be moved by muscles o move air so maintains diffusion

Question 22

why might larvae who actively hunt prey have gills, and larvae who dont actively hunt not have gills?

Answer 22

hunting larvae have higher metabolic and respiratory rate
so uses/ needs more oxygen

Question 23

explain two ways in which the structure of the gills is adapted for efficient gas exchange

Answer 23

1. many lamellae/ filaments so larger surface area
2. thin surface so short diffusion pathway

Question 24

explain how the counter current mechanism in fish gills ensures the maximum amount of oxygen passes into the blood flowing through the gills

Answer 24

water and blood flow in opposite directions
blood always passing water with higher oxygen concentration
diffusion gradient maintained throughout length of the gill
if water and blood flowed same direction, equilibrium would be reached

Question 25

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

Answer 25

micelles contain bile salts and fatty acids/ monoglycerides bring fatty acids to lining of ileum, make them more soluble fatty acids absorbed by diffusion triglycerides reform in cells vesicles move to cell membrane

Question 26

explain function of ATP hydrolase at carrier protein facilitating Na+ and K+ pump

Answer 26

ATP=ADP+Pi releases energy energy allows ions to be moved against a concentration gradient by active transport

Question 27

explain how the movement of Na+ out of the cell allows absorption of glucose into the cell lining the ileum

Answer 27

maintains a concentration gradient for Na+ from ileum into cell Na+ moving in by (facilitated diffusion OR co-transport), brings glucose with it

Question 28

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

Answer 28

- micelles include bile salts and fatty acids - they make the fatty acids more soluble in water - bring/ release fatty acids to the lining of the ileum - maintain higher conc of fatty acids to the lining of the ileum - fatty acids absorbed by diffusion

Question 29

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

Answer 29

- hydrolysis of peptide bonds - endopeptidases act in the middle of protein/ polypeptide, produces shorter polypeptides - endopeptidases act at end of polypeptide, produce amino acids - dipeptidase acts on dipeptide, between 2 amino acids, producing single amino acids

Question 30

which process do fatty acids and glycerol enter the intestinal epithelial cell by

Answer 30

diffusion

Question 31

advantage of lipid droplet and micelle formation

Answer 31

droplets increase surface area for lipase action so faster hydrolysis of triglycerides micelles carry fatty acids and glycerol through membrane to intestinal epithelial cell

Question 32

how do cells lining the ileum of mammals absorb glucose by cotransport with sodium ions

Answer 32

sodium ions actively transported from ileum cell to blood maintains/ forms diffusion gradient for sodium o enter cells from gut glucose enters by facilitated diffusion with sodium ions

Question 33

give the pathway a red blood cell takes when travelling from kidney to the lungs do not include descriptions of pressure changes in the heart or role of valve

Answer 33

- renal vein - vena cava to right atrium - right ventricle to pulmonary artery

Question 34

explain how water from tissue fluid is returned to the circulatory system

Answer 34

plasma proteins remain creates water potential gradient water moves to blood by osmosis returns to blood by lymphatic system