Exchange (Chapter 6)

Question 1

How are epithelial cells adapted for absorption?

Answer 1

Microvilli give large SA

Many mitochondria - release energy for active transport

Carrier proteins - for active transport & facilitated diffusion

Co-Transport of sodium ions and glucose

Membrane bound enzymes digest disaccharides and produce glucose.

Question 2

Define Digestion

Answer 2

The hydrolysis of larger/insoluble molecules into smaller, soluble ones.

Question 3

Where is amylase made?

Answer 3

Salivary glands, pancreas and small intestine

Question 4

What does amylase hydrolyse and what to?

Answer 4

Starch > Maltose

Question 5

Where is maltase made?

Answer 5

Epithelial lining of small intestine

Question 6

What does maltase hydrolyse and what to?

Answer 6

Maltose > 2 alpha glucose

Question 7

Describe the active transport of glucose

Answer 7

Transported by co-transport as 2 molecules are needed.

1) Sodium ions are actively transported to blood from epithelial cells by Na/K pump.
2) Forms diffusion gradient for sodium to enter from lumen.
3) Glucose enters by facilitated diffusion.

Question 8

Describe the Digestion of Proteins

Answer 8

1) Hydrolysis of peptide bonds.
2) Endopeptidases hydrolyse internal peptide bonds from polypeptides to smaller peptide chains (more ends for exopeptidases).
3) Exopeptidases remove terminal amino acids.
4) Dipeptidases hydrolyse dipeptides into amino acids.

Question 9

Describe the Digestion of Lipids

Answer 9

1) Lipids are split up into smaller droplets by bile salts).
2) Droplets increase surface area (for lipase/ensyme action).
3) Faster hydrolysis/digestion of lipids/triglycerides
4) Micelles carry fatty acids and glycerol/monoglycerides to/through membrane to internal epithelial cells.
5) Fatty acids and glycerol enter the intestinal epithelium by diffusion.

Question 10

Describe the Absorption of Lipids

Answer 10

1) Golgi modifies/processes triglycerides.
2) Combines triglycerides with proteins to form chylomicrons.
3) Packaged for release/exocytosis or forms vesicles.
4) Chylomicrons enter the lymphatic system, eventually draining into the circulatory system.
5) Triglycerides are hydrolysed by an enzyme in the endothelial layer of capillaries.
6) Fatty acids can then diffuse into cells.

Question 11

Describe how oxygen goes from lungs to blood

Answer 11

1) Oxygen goes into alveoli and dissolves in the moist lining of alveolus.
2) Diffuses across alveolus epithelium and blood capillary epithelium
3) Picked up by red blood cells.

Question 12

What are the adaptations of the lungs for exchange?

Answer 12

• Large SA:V ratio as many aveoli.
• Short diffusion pathway - single layer of epithelial cells and endothelial capillary walls.
• Partially permeable.
• Concentration gradient as constant ventilation/circulation replaces blood saturated with oxygen.

Question 13

Describe the process of inspiration

Answer 13

1) External intercostal muscles contract.
2) Ribs move up and out.
3) Volume of thorax increases.
4) Diaphragm muscles contract - diaphragm flattens.
5) Volume increases (pressure decreases in thorax).
6) Air drawn in (atmospheric pressure bigger than pulmonary pressure).

Question 14

Define Pulmonary Ventilation

Answer 14

Total volume of air moved into the lungs in one minute.

Question 15

What is the equation for pulmonary ventilation?

Answer 15

Tidal Volume x Ventilation Rate

Question 16

Describe the process of expiration

Answer 16

1) Internal intercostal muscle contract.
2) Ribs move down and in.
3) Diaphragm muscles relax - diaphragm moves up.
4) Volume decreases/pressure increases.
5) Pulmonary pressure in more than atmospheric pressure so air moves out.

Question 17

Describe the adaptation of ventilation system in fish

Answer 17

• Large SA:V as many lamellae/filaments.
• Short diffusion pathway as thin epithelium (surface) (short distance between blood and water).
• Concentration gradient is maintained along length of filament due to counter-current flow (blood and water flow in opposite directions)/circulation replaces blood saturated with oxygen.

Question 18

Describe the adaptation of gas exchange in leaves

Answer 18

• Large SA as air spaces between spongy mesophyll inside leaves.
• Maintained concentration gradient of CO2 as wind replaces air around leaves.
• CO2 moves by diffusion through stomata that are controlled by guard cells.

Question 19

Describe the adaptation of ventilation system in insects

Answer 19

• Large SA:V as small.
• Spiracles control the gas exchange and prevent too much water loss.
• Simple diffusion along trachea to respiring tissue.
• Concentration gradient created as oxygen used in respiration so oxygen diffuses in.