3-6 Gas Exchange + Digestion

Question 1

What is the relationship between the surface area and volume of an organism?

Answer 1

As the size of an organism increases: volume increases more than surface area increases

Question 2

How are single-celled organisms adapted for exchange?

Answer 2

large SA:vol, gases diffuse

Question 3

How do respiratory gases move into and out of the tracheole system?

Answer 3

Along a diffusion gradient, ends of tracheoles filled with water

Question 4

How have insects adapted to minimise water loss?

Answer 4

small sa: vol, waterproofing, spiracles

Question 5

How have plants adapted to minimise water loss?

Answer 5

thick cuticle, rolled leaves, hair, stomata in pits, reduces sa:vol of leaves

Question 6

How does gas exchange occur in insects?

Answer 6

through a network of tubes, tracheoles, they shorten the diffusion path,

Question 7

How do gills work?

Answer 7

made up of filaments, water taken in through the mouth, forced over the gills and out the openings on the body

Question 8

What is the countercurrent exchange principle?

Answer 8

blood well loaded with oxygen meets water, which is at maxiumu conc so diffusion from water to blood occurs, low oxygen blood meets water, oxygen diffuses to the blood

Question 9

What is Fick’s Law?

Question 10

What are the lungs?

Answer 10

a pair of lobed structures made up of bronchioles

Question 11

What is the trachea?

Answer 11

a flexible airway supported by rings of cartilage, made of muscle, lined with ciliated epithelium

Question 12

What are the bronchi?

Answer 12

two divisions of the trachea, produce mucus to prevent the entry of dirt, supported by cartilage

Question 13

What are the bronchioles?

Answer 13

branching subdivisions, made of muscle with epithelial cells

Question 14

What are the alveoli?

Answer 14

minute air sacs at the end of the bronchioles, between them are collagen and elastic fobres to stretch as they fill with air, then spring back to expel air

Question 15

What are the alveoli?

Answer 15

minute air sacs at the end of the bronchioles, between them, are collagen and elastic fibres to stretch as they fill with air, then spring back to expel air

Question 16

What causes expiration?

Answer 16

Internal intercostal muscles contract
External intercostal muscles relax

Ribs move downwards and inwards to decrease the thorax volume
Diaphragm muscles relax and so is pushed up by the previously compressed contents of the abdomen
Volume of the thorax is further decreased
Decreased volume increases the pressure in the lungs
The pulmonary pressure is now greater than in the atmosphere so air is forced out of the lungs

Question 17

How does gas pass from the alveoli to the capillaries?

Answer 17

capillaries very small and slow down blood, very close tp capillaries to shorten diffusion distance

Question 18

What is the stomach?

Answer 18

a muscular sac with an inner layer that produces enzymes, stores and digests food, mostly protein

Question 19

What is the ileum?

Answer 19

long muscular tube, enzymes produced in walls, villi for large surface area, microvilli even further

Question 20

What does the large intestine do?

Answer 20

absorbs water, mostly from digestive glands

Question 21

What are the salivary glands?

Answer 21

secrete amylase which hydrolyses starch into maltose

Question 22

What is the pancreas?

Answer 22

a large gland below the stomach, secretion called pancreatic juice which contains lipase, protease and amylase

Question 23

How are carbohydrates digested?

Answer 23

amylase breaks starch into maltose, maltase then breaks it into glucose monomers, sucrase and lactase for the corresponding bonds

Question 24

How are lipids digested?

Answer 24

Lipases hydrolyse lipids into fatty acids and glycerol. firstly into micelles by bile salts

Question 25

How are proteins digested?

Answer 25

endopeptidases - hydrolyse bonds in the amino acid chain
exopeptidases - hydrolyse peptide bonds on terminal amino acids, releasing dipeptides and single amino acids

dipeptidases - final hydrolysis until all amino acids are single

Question 26

How are amino acids and monosaccharides absorbed?

Answer 26

by diffusion and co-transport

Question 27

How are triglycerides absorbed?

Answer 27

once micelles are created, they breakdown when they come into contact with microvilli epithelial cells and diffuse as they are non-polar

Question 28

What is the environment around cells of multicellular liquid?

Answer 28

Tissue fluid

Question 29

What organisms require a larger volume to surface area ratio?

Answer 29

Organisms with a higher metabolic rate exchange more materials so require a larger surface area to volume ratio

Question 30

What are the characteristics of specialised exchange surfaces?

Answer 30

Large surface area relative to volume
Very thin so diffusion distance is reduced

Selectively permeable to allow selected materials across
Movement of the environmental medium maintains the concentration gradient
A transport system to ensure the moment of the internal medium

Question 31

What is the internal system of insects?

Answer 31

The internal network of tubes called tracheae
Tracheae are supported by strengthened rings which prevent them from collapsing

Tracheae divide into smaller dead-end tubes called tracheoles
Tracheoles extend throughout the bodily tissues
This creates a short diffusion pathway

Question 32

How do respiratory gases move in/out of the trachea via the diffusion gradient?

Answer 32

When cells are respiring, oxygen is used up and the concentration at the ends of the tracheoles falls
The concentration gradient causes oxygen to diffuse from the air to the tracheae to cells

Carbon dioxide is produced by cells which creates an opposite concentration gradient
Carbon dioxide diffuse from the cell’s to the atmosphere
Diffusion in air is more rapid than in water so this is a quick method

Question 33

How do respiratory gases move in/out of the trachea via mass transport?

Answer 33

The contraction of muscles in insects can squeeze the tracheae enabling mass movements of air in and out
This spread up the exchange of respiratory gases

Question 34

How do respiratory gases move in and out of the trachea system via the ends of the tracheoles being filled with water?

Answer 34

During major activity, the muscle cells around the tracheoles respire anaerobically
This produces lactate which is soluble and lowers water potential

Water moves into the cells from the tracheoles by osmosis
The water decreases in volume and so draws air into them
The final diffusion pathway is in a gas rather than a liquid phase so is more rapid
This leads to greater water evaporation

Question 35

How does the countercurrent help diffusion of oxygen?

Answer 35

Blood that is already loaded with oxygen meets with water that’s loaded with oxygen
Blood with little oxygen meets water with little oxygen

This means diffusion of oxygen from water to blood is constantly taking place

Question 36

How are leaves adapted for photosynthesis/respiration?

Answer 36

Large surface area: rapid diffusion
Thin and flat leaves: short diffusion pathway

Stomata usually occur on the underside of the leaf: stops water loss
Numerous interconnecting air spaces: allow for gases to come in contact with mesophyll cells
Guard cells: open and close stoma to prevent water loss

Question 37

What is the equation for pulmonary ventilation?

Answer 37

Tidal volume (dm3) X breathing rate (min~1)

Question 38

What is the pulmonary ventilation rate?

Answer 38

The total volume of air that is moved into the lungs during one minute

Question 39

What is tidal volume?

Answer 39

The volume of air that is normally taken in at each breath when the body is at rest. This is usually around 0.5dm3

Question 40

What are the enzymes involved in the digestive system?

Answer 40

Carbohydrases: hydrolyses carbohydrates, ultimately into monosaccharides
Lipases: hydrolyse lipids into glycerol and fatty acids

Proteases: hydrolyse proteins, ultimately into amino acids

Question 41

What are the steps of starch digestion in humans?

Answer 41

Mouth: saliva contains mineral salts that maintain a neutral optimum pH and salivary amylase which starts to hydrolyse starch
Stomach: acidic which denatures amylase so hydrolysis stops

Ileum: pancreatic juice contains pancreatic amylase which converts starch to maltose and alkaline salts which maintain the optimum neutral pH, muscles push the food along
Maltase is a part of the cell surface membranes of the epithelial cells which line the ileum (membrane-bound disaccharide)
Maltase hydrolyses maltose into alpha glucose

Question 42

What is the process of lipid digestion?

Answer 42

Hydrolysed by enzymes called lipases
Lipases hydrolyse the ester bond in triglycerides to form fatty acids and monoglycerides

Lipids are firstly split up into tiny droplets called micelles by bile salts which are produced by the liver
This is emulsification which increases surface area of the lipids so the action of lipases is sped up

Question 43

How are micelles formed?

Answer 43

One end of the bile salt is soluble in fat and hydrophobic, other is reversed
This means that they can arrange themselves with their ends in fatty acid droplets and their lipophobic ends sticking out

This prevents fat droplets from sticking to each other to form large droplets, leaving tiny droplets (micelles)