Gasexchange And Digestion

Question 1

2 features of unicellular organisms

Answer 1

Have large SA:V
Short diffusion distance

Question 2

2 features on multicellular organisms

Answer 2

Have a small SA:V
Diffusion distance is large

Question 3

Why do smaller animals have a lower metabolic rate?

Answer 3

Because they have a greater SA:V but they lose heat more easily

Question 4

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

Answer 4

Oxygen used in respiration which provides energy/ ATP

Question 5

What do the salivary glands produce and help to digest

Answer 5

Produces amylase in saliva
Breaks glycosidic bonds in starch to form maltose

Question 6

What does the pancreas produce and help to digest

Answer 6

Produces pancreatic amylase which is released into the small intestine
And it helps to break down glycosidic bonds to hydrolyse starch to form maltose

Question 7

What does the small intestine produce and help to break down

Answer 7

Produces membrane bound disaccharides in the cell membrane of epithelial cells
Breaks glycosidic bonds or hydrolyse disaccharides into monosaccharides

Question 8

Describe the role of enzymes of the digestive system in the complete breakdown of starch

Answer 8

Amylase, in pancreas, hydrolyses starch into maltose
Maltose is then hydrolysed into glucose by the enzyme maltase
Amylase is secreted by the salivary gland in the mouth which hydrolyses starch into maltose
Pancreas secretes amylase to further hydrolyse starch into maltose
Alpha glucose is co-transported into epithelial cells and into the blood

Question 9

Describe the processes involved in the absorption of the products of starch digestion

Answer 9

Glucose move in with sodium into epithelial cells
Ions and glucose molecules are co-transported into the epithelial cell via facilitated diffusion
Glucose molecules diffuse across the epithelial cell & enter the capillary at the other end of the cell via facilitated diffusion
The low concentration of sodium ions is maintained by actively transporting sodium out of the epithelial cells and into the blood.

Question 10

What are peptidases/ proteases

Answer 10

Enzymes which breakdown proteins in a series of hydrolysis reactions

Question 11

Role of an endopeptidase

Answer 11

Hydrolyse peptide bonds within a protein to create smaller polypeptide chains
Create for terminal ends for exopeptidases to work on

Question 12

Role of exopeptidases

Answer 12

Hydrolyse terminal peptide bonds to remove individual amino acids and create smaller polypeptide chains

Question 13

Role of dipeptidases

Answer 13

(Type of exopeptidase)
Located on the membrane of epithelial cells lining small intestine
- work on dipeptides to hydrolyse the peptide bond holding them together

Question 14

Describe the roles of micelles in the absorption of fats into the cells lining the ileum

Answer 14

Micelles include bile salts and fatty acids
Makes the fatty acids more soluble in water
Releases fatty acids into the lining of the ileum
Maintains a higher concentration of fatty acids to the lining of the ileum
Fatty acids are absorbed by diffusion

Question 15

How are sodium ions involves in the absorption of amino acids

Answer 15

Used in co-transport

Question 16

What are lipases

Answer 16

Enzymes which hydrolyse the ester bonds in triglycerides to form fatty acids and monoglycerides

Question 17

Where are bile salts stored and produced and released

Answer 17

Produced by the liver and stored in the gall bladder which releases them into the small intestine

Question 19

Role of bile salts

Answer 19

Help to break down large fat globules by emulsifying them into smaller droplets, helping to speed up the action of lipases by increasing the SA of lipids that can be exposed to the enzyme

Question 20

What happens once the lipid is broken down by lipase

Answer 20

The monoglycerides and fatty acids stay attached to the bile salts & form micelles

Question 21

What are the steps in absorption of lipids (5 points)

Answer 21

1 micelles hit epithelial cells and breakdown allowing monoglycerides and fatty acids to diffuse across the membrane because they re lipid soluble
2 monoglycerides and fatty acids are transported to the ER where they recombine to form triglycerides again
3 inside the Golgi they bind with cholesterol and proteins and are packages to form chylomicrons
4 chylomicrons travel in a vesicle to the cell membrane and are exocytosed from epithelial cell
5- chylomicrons enter lacteals transporting them away from the small intestine to muscle tissue

Question 22

Suggest how chylomicrons leave the epithelial cell

Answer 22

Travel in a vesicle to the cell membrane then are exocytosised out of the cell as the size is too large to leave by other methods

Question 23

Explain the advantages of lipid droplet and micelle formation

Answer 23

Droplets increase surface area for enzyme action so there’s faster hydrolysis of lipids
Micelles carry fatty acids and glycerol

Question 26

How are amino acids transported from the lumen of the ileum into the blood

Answer 26

Majority of amino acids move from the lumen to epithelial cells via co transport using sodium ions When the concentration of amino acids is greater in the lumen than the epithelial cells, they can move via facilitated diffusion Facilitated diffusion into the blood

Question 27

3 products of the digestion of lipids by lipase

Answer 27

Monoglycerides, fatty acids and glycerol

Question 28

What do chylomicrons enter rather than capillaries

Answer 28

Lacteals- found alongside the capillaries

Question 29

Why do Tracheoles have thin walls

Answer 29

Shorter DD of gases into cells

Question 30

Why are Tracheoles highly branched

Answer 30

Increases SA for gas exchange

Question 31

Why is there fluid in the ends of the trachea where it joins tissue

Answer 31

- gas exchange from air to liquid occurs in the Tracheole which allows gases to diffuse to tissue quicker - tracheal fluid can be withdrawn into the body fluid to increase the SA of the Tracheole exposed to air

Question 32

Benefit of muscles pumping body and forcing air in/out

Answer 32

Maintains concentration gradient for gases

Question 33

Benefit of having spiracles closed / not open all the time

Answer 33

Prevents water loss and keeps organism waterproof

Question 34

What does pumping of the insects body muscles do

Answer 34

Raises pressure in the body and forces air our of the spiracles down the concentration gradient

Question 35

What are the folds on the gill filaments called and what do they do

Answer 35

Lamellae - further increase the SA of the gills and have lots of capillaries and a thin layer of cells

Question 36

What occurs at the lamella

Answer 36

Gas exchange - counter-current flow

Question 37

What is countercurrent flow

Answer 37

Water and blood flow over and through the lamellae in opposite directions to each other Blood always flows next to water that has a higher oxygen concentration so diffusion happens along the full length of the lamellae The blood absorbs more and more oxygen as it moves along

Question 38

Why do fish have thin epithelium / walls of lamellae

Answer 38

Shortened DD of gases from water to blood

Question 39

Why do fish have ventilation by operculum

Answer 39

Ensures constant fresh water flow over gills to replace lost oxygen and maintains a steep concentration gradient

Question 40

Ventilation in fish

Answer 40

Mouth opens, operculum shuts Water enters cavity due to decreased pressure Mouth closes, operculum opens Increased pressure Forces water over gills

Question 41

Role of pleural fluid

Answer 41

Lubricates the lungs and allows lungs to expand with the chest during inhalation

Question 42

Function of cartilage in trachea and bronchi

Answer 42

Provides stranger by holding the airway open Prevents collapse of airway when air pressure falls

Question 43

Function of surfactant that coats the surface of the lungs

Answer 43

Phospholipid layer which maintains moisture but reduces surface tension to stop alveoli collapsing when air pressure falls

Question 44

Function of smooth muscle lining trachea and bronchioles

Answer 44

Can contract to constrict airways

Question 45

Function of goblet cells

Answer 45

Secrete mucus which traps particles of dust and bacteria which are breathed into the lungs

Question 46

Function of ciliated epithelial cells

Answer 46

Beat regularly to move mucus up the airway towards the mouth to be removed Helps keep airways clear and prevent infections Contains lots of mitochondria to provide energy requires to move cilia

Question 47

Role of elastin lining airways and alveoli

Answer 47

Allows lung tissue to stretch when breathing in and filling up the lungs Allows alveoli to return to original shape after exhaling

Question 48

Role of squamous epithelium

Answer 48

Gives a short DD pathway for oxygen and carbon dioxide in the alveoli

Question 49

What happens to guard cells when plants are hydrated

Answer 49

The guard cells become turgid keeping pores open

Question 52

What happens to guard cells when plants are dehydrated

Answer 52

Guard cells become flaccid causing hole to close

Question 53

What are xerophytes

Answer 53

Plants adapted to a dry habitat

Question 54

Why do xerophystes have sunken stomata in pits

Answer 54

Creates local humidity and decreases exposure to air currents

Question 55

What does the presence of hairs in xerophytes create

Answer 55

Local humidity and decreases exposure to air currents by reducing flow around stomata

Question 56

What does a think waxy cuticle of xerophytes allow

Answer 56

Makes plant more impermeable to water as water cant pass through or leave

Question 57

What does a small sa of a leaf allow

Answer 57

Reduced SA for evaporation

Question 58

What does stomata on inside of rolled leaf create

Answer 58

Local humidity and decreases exposure to air currents because water vapour evaporates into air spaces rather than in the atmosphere