Exchange

Question 1

Elephant surface area to volume ratio

Answer 1

small

Question 2

mouse SA:V ratio

Answer 2

large

Question 3

Fick’s law equation

Answer 3

rate of diffusion = (SA x difference in concentration)/length of diffusion path

Question 4

how do single celled organisms exchange gases

Answer 4

across their body surface as they have a large SA:V ratio

Question 5

Describe the tracheal system of insects

Answer 5

Trachea + tracheoles

spiracles

Question 6

How does gas exchange occur in insects

Answer 6

• Gases enter and exit through spiracles
• gas exchange through diffusion as CO2 and O2 move down the concentration gradient
• Mass transport, contraction of abdominal muscles to move gases along
• when aerobic respiration occurs to produce lactate, lactate will lower cells water potential of cells so water moves from tracheoles to cells, so more air is drawn in due to decreases volume in tracheoles

Question 7

How does gas exchange occur in fish

Question 8

Structure of gills in fish

Answer 8

Gill filaments at right angles to increase surface area

lamellae in gill filaments, deep folds in gills which lead to an increased surface area

Gill bar in the middle of gill filaments

Question 9

Adaptations of gills in fish

Answer 9

lamellae are folded so have a large surface area

lamellae and filaments are thin so diffusion rate increases

counter current exchange to ensure a high amount of oxygen diffuses into blood

Question 10

what is counter current exange

Answer 10

water and blood flow in opposite directions

this ensures a favourable concentration gradient of oxygen is maintained across the whole length of the lamellae between the water and bloodstream

Question 11

Adaptations of plants for gas exchange and how it happens

Answer 11

Gas enters and exits through stomata

guard cells control opening and closing of stomata which prevents water loss by evaporation

Small SA : V which prevents evaporation

thick waxy cuticle preventing water loss by evaporation

Hairy leaves trap water vapour, reducing water potential gradient, reducing water lost by evaporation

rolled leaves can reduce water potential gradient

Question 12

Structures of the lungs

Answer 12

Trachea

bronchi

bronchioles

alveoli

diaphragm

Question 13

How does inspiration work

Answer 13

External intercostal muscle contract and internal relaxes

ribs are pulled upwards and outwards

diaphragm contracts and flattens

this increases thoracic volume, so air pressure decreases, forcing air to move down the pressure gradient into the lungs

Question 14

How does expiration work

Answer 14

Internal intercostal muscles contract and external relax

ribs are pulled downwards and inward

diaphragm relaxes and pushes back into a dome shape

this decreases thoracic volume, increases air pressure, so air is forced out of the lungs

Question 15

adaptation of alveoli

Answer 15

very large surface area, so a higher rate of diffusion

surrounded by lots of capillaries, diffusion distance is thin

alveolar epithelium is thin

Question 16

Where is amylase produced and where is it secreted

Answer 16

salivary glands
the pancreas secretes into small intestine

Question 17

What does amylase do

Answer 17

hydrolyses starch into maltose

Question 18

what are membrane bound disaccharidases

Answer 18

enzymes present in membrane of small intestine

hydrolyse disaccharides to monosaccharides

Question 19

What does lipase do

Answer 19

hydrolyse lipids to monoglycerides and fatty acids

Question 20

What do proteases do and what are the 3 types

Answer 20

hydrolyse proteins ( polypeptides ) into amino acids

endopeptidases
exopeptidases
membrane bound dipeptidases

Question 21

What is the role of endopeptidases

Answer 21

hydrolyse peptide bonds in the middle region of the polypeptide chain

Question 22

what is the role of exopeptidases

Answer 22

to hydrolyse bonds on the terminal amino acids

Question 23

What is the role of membrane bound dipeptidases

Answer 23

Hydrolyse dipeptides into 2 amino acids

Question 24

how are lipids digested into the epithelium

Answer 24

bile salts from the liver emulsify lipids so they have a large SA so are more easily hydrolysed by lipases

products from lipid hydrolysis can form micelles with bile salts

these can travel to the ileum and are broken down in contact with epithelium, these products can diffuse straight into epithelium

Question 25

How are amino acids and monosaccharides absorbed into bloodstream

Answer 25

co-transport

Na+ ions move with the molecule into the epithelium by co transport from the lumen to the epithelium

Na+ ions in epithelium are actively transported into the blood via a Na-K pump to ensure a favourable concentration gradient of sodium between lumen and epithelium

substance then moves via facilitated diffusion from epithelium into blood