exchange

Question 1

Equation to work out SA:V ratio

Answer 1

Surafe area/volume

Question 2

What does a low SA:V ratio mean

Answer 2

A low SA:V ratio means that there are parts of an object that are a long way from the edge. Means there is a longer diffusion distance.

Question 3

What happens to SA:V as size increases

Answer 3

As size increases, surface area:volume ratio decreases

Question 4

What is an organisms metabolic rate

Answer 4

Metabolic rate is the amount of energy expended by that organism in a time period

Question 5

What is the general rule for metabolism

Answer 5

The greater the mass of an organism, the higher the organisms metabolic rate. This is because organisms with high metabolic rate requires more efficient delivery of oxygen to cells as more respiration is needed

Question 6

How to increase rate of exchange when it’s a big organism

Answer 6

Larger organisms come up with specialised surface area

Question 7

Unicellular organisms

Answer 7

They have a large SA:V ratio. Diffusion distance is short to get from outside the cell to the centre. They can exchange materials directly with their environment. They lose water and heat very easily so cant live in very hot or cold climates.

Question 8

Multicellular organisms

Answer 8

They have a small SA:V. Diffusion distance is large. Heat is maintained better so can survive more easily in cold climates. Some cells arent exposed to outside at all so need internal mass transport systems.

Question 9

Adaptation for cold climate

Answer 9

Challenge- heat loss
Behavioural- small mammals with large SA:V. They may also hibernate in the coldest months.
Physical- adapted animals with have a streamlined, compacted body shape to give a smaller SA:V. May also have thick fur e.g. arctic foxes

Question 10

Adaption for hot climate

Answer 10

Challenge- overheating
Behavioural- spending lots of time in the water. Nocturnal as to avoid hot daytime.
Physical- animals with a low SA:V often have larger ears to increase surface area

Question 11

Adaption for dry climates

Answer 11

Challenge: water loss
Behavioural- may be nocturnal so most active in cooler temperatures
Physical- small animals with high SA:V have kidney structures to produce less urine

Question 12

Structure of insects

Answer 12

Evolved to live on land and have microscopic air filled pipes. Trachae divides into tracheoles. Divides until they penetrate into individual body cells. Gases are directly exchanged between cells and the atmosphere- there is no need to transport them. Air enters the trachea through pores on the surface of the exoskeleton called spiracles. CO² and O² will diffuse in/out of spiracles down there concentration gradient for gases. Spiracles can be closed/not open all the time, this is to prevent water loss a d to keep the organism waterproof

Question 13

Structure of fish

Answer 13

Each gill is made of lots of gill filaments which are attached to a bony arch which creates a large surface area for water or flow over. Gill filaments have tiny folds called lamellae which increase surface area. Lamellae have lots of blood capillaries and a thin layer of cells.

Question 14

What is countercurrect flow

Answer 14

Countercurrent flow is where blood and water flow over and through the lamellae in opposite directions to each other. Blood flows next to water that has higher oxygen concentration, so diffusion happens along the full length of the lamellae. Blood absorbs more and more oxygen as it moves along. Even when blood is highly saturated there is still a concentration gradient so more oxygen can flow in

Question 15

Adapted structure for fish

Answer 15

Thin walls for lamellae- shortens diffusion distance
Lots of gill filaments and lamellae- increases surface area
Countercurrent flow of blood to water- maintains concentration gradient
Large number of capillaries and lamellae- circulation constantly removes oxygenated blood to maintain steep concentration gradient
Ventilation by operculum- ensures fresh water always goes over gills to replace lost oxygen.

Question 16

How does ventilation work in fish

Answer 16

The mouth opens, so the operculum shut. Water enters cavity due to a decrease in pressure. The mouth then closes which opens the operculum. This increases pressure which forces the water out of the gills.

Question 17

Where does co² enter and oxygen leave

Answer 17

Happens in the stomata normally on the lower epidermis

Question 18

What is right above the lower epidermis

Answer 18

The spongy mesophyll

Question 19

Adaption of spongy mesophyll

Answer 19

Lots of air gaps which means there is more air space to allow diffusion through the gas phase and increase SA:V formexchnage into photosynthesising cells

Question 20

What tissue is above the spongy mesophyll

Answer 20

The palisades mesophyll tissue

Question 21

Adaptions for palisade mesophyll layer

Answer 21

It is more compact to increase light absorption by chlorophyll. High rate of photosynthesis which maintains a steep concentration gradient.

Question 22

What layer is above the palisade mesophyll tissue

Answer 22

The upper epidermis

Question 23

Adaption of upper epidermis

Answer 23

Has few to no stomata which is topped with a waxy cuticle in order to limit water loss.

Question 24

What is the compensation point

Answer 24

At night a plants gas exchange reverses and begins a net absorption of oxygen and releases co². The point in the day when net co² uptake is 0 is the compensation point.

Question 25

How do guard cells work

Answer 25

ATP-powered proton pump transports hydrogen ions out of cells. The potassium ions diffuse into cells down electrochemical gradient. This lowers water potential inside the cell. Wated enters cell by osmosis. The turgid pressure in the cell increases. The thin wa,,s bend more so the cell curves and the stoma opens

Question 26

Where does gas exchange take place in mammals

Answer 26

In the lungs

Question 27

Structure of lungs

Answer 27

.air goes through the mouth and down the trachea. Trachea splits in half turning into bronchi, which branch of into bronchioles. These goe into the alveoli which are small air sacs

Question 28

Structure of aveoli

Answer 28

. Alveolar epithelium and capillaries are very things diffusion distance is very short
. Lots of alveoli which increases surface area
. Constant ventilation of air in and out of lungs- ensures concentration of oxygen in alveolus is higher nd concentration of co² is lower than blind and therefore maintains a steep concentration gradient.

Question 29

Process of Inhalation

Answer 29

Diaphragm contracts and moves down. External intercostal muscles contract and pull the ribcage up and out. Increases volume in thoracic cavity which reduces air pressure. Air rushes in due to there being a concentration gradient.

Question 30

Process of exhalation

Answer 30

Diaphragm relaxes and moves up. External intercostal muscles relax and move ribcage down and in. Decreases volume in thoracic cavity which increases the air pressure because there is less space. Air moved out of the trachea down the pressure gradient.

Question 31

what 2 measurements telling you about the lungs functioning

Answer 31

ventilation and tidal volume

Question 32

how to measure lung function

Answer 32

by using a spirometer and work out breathing rate, the tidal volume and ventilation from this alone.

Question 33

what is forced expiratory volume

Answer 33

the maximum volume of the air that can be breathed out in one second

Question 34

what is forced vital capacity

Answer 34

the maximum volume of air it is possible to breathe forcefully out of the lungs

Question 35

two types of lung disease

Answer 35

restrictive disease and obstructive disease

Question 36

what is restrictive lung disease

Answer 36

makes it hard to fully breathe in. severely reduces FVC but FEV is less impacted

Question 37

what is obstructive lung disease

Answer 37

makes it hard to breathe out as air ways are blocked. both FVC and FEV are both very low

Question 38

tuberculosis

Answer 38

cause- bacteria inhaled. the macrophage build up makes hard lumps in alveoli. eventually the infection will die and damage the alveoli
effect- alveoli have smaller SA. scar tissue is thicker. less elasticity.
tidal volume- decreased
ventilation rate- increased

Question 39

pulmonary fibrosis

Answer 39

cause- formation of scar tissue in the lungs after an infection or breathing in substances
effect- scar tissue is thicker. elasticity is reduced.
tidal volume- decreased
ventilation rate- increased

Question 40

asthma

Answer 40

cause- airways become inflamed due to an allergic reaction to inhaled substances
effect- reduces rate of gas exchange
FEV-severely reduced

Question 41

salivary gland and carbohydrates

Answer 41

amylase enzyme in saliva which breaks glycosidic bonds in starch to form maltose

Question 42

pancreas and carbohydrates

Answer 42

pancreatic amylase released into the small intestine which breaks glycosidic bond to hydrolyse starch to form maltose

Question 43

small intestine and carbohydrate

Answer 43

membrane bound disaccharidase into cell membrane of epithelial cells as it breaks glycosidic bonds to hydrolyse disaccharides

Question 44

how do the monosaccharides get into the cell

Answer 44

glucose and galactose- co transport with sodium
fructose- facilitated diffusion through channel protein

Question 45

digestion of proteins

Answer 45

peptidase breaks down proteins. hydrochloric acid in stomach creates optimum pH for enzyme pepsin which is secreted by cells which line the stomach. other peptidases are membrane-bound and found within cells that lined the ileum. the single amino acids are then absorbed into the bloodstream.

Question 46

three types of protease enzymes that breaks bonds

Answer 46

endopeptidases- inside hydrolyse peptide bonds within a large protein to create smaller polypeptide chain. creates more terminal ends for exopeptidases
exopeptidases- outside. hydrolyse terminal peptide bonds to remove individual amino acids and create smaller polypeptide chains
dipeptidase- a type of exopeptidase. these are often located on the membrane of epithelial cells lining the small intestine. the work specifically on dipeptides to hydrolyse the peptide bond holding them together. this creates two single amino acids which can then be transported through membrane into the epithelial cell

Question 47

what does a lipase reaction turn a triglyceride into

Answer 47

fatty acids and monoglycerides

Question 48

where are lipase

Answer 48

they are made in the pancreas and secreted into the small intestines

Question 49

where are bile salts

Answer 49

they are produced in the liver and stored in the gallbladder which releases them into the small intestine

Question 50

what does bile salts do

Answer 50

breaks down large fat globules by emulsifying them into small droplets. helps to speed up the action of lipase by increasing surface area.

Question 51

what happens once the lipid is broken down

Answer 51

the monoglycerides and the fatty acids stay attached to the bile salts and for micelles which help to absorb fat into the blood stream.

Question 52

absorption of amino acids

Answer 52

happens in the small intestine. the villi are folded thin and have a good blood supply. amino acids are absorbed by co transport binding to a sodium ion.

Question 53

absorption of lipids

Answer 53

micelles hit epithelial cells and breakdown allowing monoglycerides and fatty acids to diffuse across membrane because they are lipid soluble. transported to endoplasmic reticulum where they are resynthesised into triglycerides. inside Golgi, bind with cholesterol and protein to for chylomicrons. chylomicrons travel in a vesicle to the cell membrane and go through exocytosis into the lymphatic vessel as its too big to get into capillary.