6. Exchange

Question 1

describe Fick’s law

Answer 1

relates rate of diffusion to:
- conc gradient
- diffusion distance
- SA

Question 2

calculation for rate of diffusion

Answer 2

rate =
(SA x conc diff)/thickness of membrane)

Question 3

describe the counter current principle

Answer 3

blood flows in opposing direction, so blood at high 02 concentration meets blood at high concentration and low concentration meets more low concentration.

maintains concentration gradient across exchange surface

Question 4

describe the tracheal system

Answer 4

oxygen is delivered directly to all organs and tissue

spiracles allow air in and out

trachea are tubes carrying oxygen, leading to tracheoles

Question 5

Explain the three ways that gas exchange can occur in insects

Answer 5

• diffusion, concentration gradient created by respiration.
• mass transport, insect contracts and relaxes abdominal muscles.
• respire anaerobically = lactate, lowers water potential of the cells, water leaves tracheoles. more air can enter

Question 6

Describe the structure gill filaments

Answer 6

rows of lamellae, which are single layers of cells that cover a network of capillaries

Question 7

how do insects, fish gills, and plants achieve a large surface area

Answer 7

insects; a large number of tracheoles

fish gills; a large number of filaments

plants; air spaces in the spongy mesophyll

Question 8

state two similarities between gas exchange in a plant leaf and gas in an insect

Answer 8

• water loss must be avoided
• diffusion through pores, can control opening and closing

Question 9

state two differences between gas exchange in a leaf and an insect

Answer 9

insects have smaller SA:V ratio than plants

insects have specialised structures (trachea) along which gases diffuse, plants do not

Question 10

what three things reduce water loss in insects

Answer 10

small SA:V ratio
waterproof covering
closing of spiricales

Question 11

what are plants that have adapted to limit water loss through transpiration called?

Answer 11

xerophytes

Question 12

suggest four ways xerophytes have adapted to limit water loss

Answer 12

thick cuticle, physical barrier

rolling up of leaves, inside of curl becomes saturated water vapor, no gradient = no water loss

stomata in pits, traps moist air, no gradient

less SA; must balance for photosynthesis

Question 13

why are manimal lungs located inside the body

Answer 13

• air is not dense enough to support its delicate structure
• body would lose a lot of water

Question 14

how do the internal and external intercostal muscles aid in the expiration

Answer 14

internal contracting
external relax

Question 15

when does the diaphragm contract

Answer 15

during inspiration

Question 16

give three reasons diffusion across the alveoli is rapid

Answer 16

• thin capillaries;
  cells are slowed down = more time for diffusion,
  cells are flattened against membrane = less distance to diffuse
• alveoli and capillaries have large SA
• concentration gradient is maintained by ventilation (breathing)
• blood flow maintains a concentration gradient

Question 17

what are the two types of digestion

Answer 17

physical breakdown
chemical breakdown

Question 18

what does chemical digestion involve

Answer 18

breakdown of large insoluble molecules by hydrolysis, involving enzyme action

Question 19

describe the process of carbohydrate digestion

Answer 19

• salary glands secrete amylase which hydrolyses starch into maltose
• pancreas releases amylase into the small intestine, continuing the hydrolysis of starch.
• the epithelial lining of the small intestine produces the ‘disaccharidase’ maltase (membrane-bound) maltase hydrolysis maltose into a-glucose.

(same for sucrase + lactase)

Question 20

what is a micelle? what is this process called?

Answer 20

lipids that have been split into tiny droplets by bile salts,

emulsification, increasing SA for lipases to hydrolise

Question 21

explain each peptidase role

Answer 21

• endopeptidases, hydrolyze the peptide bonds in the center of the protein molecule, leaving two polypeptide chains
• exopeptidases, hydrolyze terminal (end) peptide bond of protein, leaving dipeptide, tripeptide, or single amino acids.
• dipeptidases, hydrolyze bond between dipeptides (membrane-bound) in the lining of the ileum

Question 22

how is the ileum adapted for absorption of the products of digestion?

Answer 22

folded into a structure called villi;

-increased surface area

-thin, short diffusion pathway

-muscles allow them to move, maintaining a concentration gradient.

-a good supply of blood, maintaining the concentration gradient

-microvilli further increases surface area

Question 23

Explain the process of absorption of triglycerides

Answer 23

• micelles come in contact with epithelial lining, where they break down. releasing monoglycerides and fatty acids which diffuse into the epithelial cell.
• monoglycerides and fatty acids are transported to RER and are reformed into triglycerides.
• triglycerides reform with cholesterol forming chylomicrons, these leave the cell by exocytosis, into lacteal capillaries.

Question 24

Give three adaptations that insects have for diffusion

Answer 24

• large number of tracheoles, large SA
• walls of tracheoles are thin, short pathway
• respiration sets of gradients.

Question 25

How do insects limit water loss?

Answer 25

• small SA : V (where water can evaporate from)
• waterproof exoskeleton
• Spiracles, open and close

Question 26

Give the definition and equation for pulmonary ventilation

Answer 26

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

Pulmonary ventilation = tidal volume x ventilation rate

Question 27

What are micelles?

Answer 27

monoglycerides and fatty acids associated with bile salts.