topic 5

Question 1

ultrafiltration process

Answer 1

• blood is filtered from glomerulus into renal capsule then into the proximal convulated tube
• afferent arteriole is wider trhsan the efferent arteriole
• so blood in glomerulus is under a higher pressure than bowmans capsule
• pressure difference pushes fluid from glomerulus to bowmans capsule

Question 2

what is filtered out of the blood in ultrafiltration

Answer 2

water
amino acids
glucose
urea
inorganic ions

Question 3

what is left in the capillary in ultrafiltration

Answer 3

blood cells
proteins
some water

Question 4

osmoregulation process

Answer 4

1. adh detected by cell surface receptors - this is an example of cell signalling which causes a chain of enzyme controlled reactions within the cell
2. vesicles containing aquaporins fuse to the membrane
3. more water can be reabsorbed by osmosis into the blood
4. if ADH falls, the cell surface membrane folds inwards for more vesicles, which removes water permeab;le channels for less reabsorption

Question 5

why is the inner mitochondiral membrane impermeable to H+ ions

Answer 5

to maintain chemical gradient required for chemiosmosis

Question 6

what are the net products of glycolysis

Answer 6

2x NADH
2x ATP
2 x pyruvate

Question 7

products of link reaction per glucose molecule

Answer 7

2x acetyl coenzyme A
2x CO2
2x reduced NAD

Question 8

net products of krebs cycle for one molecule of pyruvate

Answer 8

3x reduced NAD
1x reduced FAD
1x ATP

Question 9

refractory period

Answer 9

period where the membrane of an axon of a neurone cant be depolarised and no action potential can be initiated

Question 10

myelin sheath

Answer 10

electrical insulator which prevents action potentials from forming

Question 11

cholinergic synapses

Answer 11

uses acetylcholine as its neurotransmitter, which is released when an action potential arrives at the pre-synaptic knob then diffuses across the synaptic cleft.

when it reaches the post synaptic membrane, a new action potential is generated

Question 12

what channels do the pre-synaptic knob have?

Answer 12

voltage gated calcium channels, which open when an action potential arrives at presynaptic knob

Question 13

what does the post synaptic membrane contain

Answer 13

sodium ion channels, which contain binding sites that are complementary to the acetylcholine shape

when acetylcholine binds to these, it causes them to become permeable to sodium ions

sodium ions entering the post synaptic cell causes depolarisation

Question 14

what are the three layers between blood in glomerulus and fluid in the bowmans capsule

Answer 14

• endothelium: narrow gaps between cells (fenestrations)
• basement membrane: fine mesh of collagen fibres and glycoproteins which acts as a filter stopping larger molecules
• podocytes: finger-like projections that ensure gaps between cells

Question 15

can protein (non steroid) hormones enter the cell?

Answer 15

no, insoluble in phospholipid membrane

Question 16

can steroid hormones enter the cell?

Answer 16

yes, can pass through the membrane

Question 17

first messenger system

Answer 17

• non steroid hormones are first messengers
• binds to receptors on the outside of the cell and initiate effects inside
• causes release of secondary messengers which stimulate a change in activity of the cell

Question 18

secondary messenger system

Answer 18

• first messenger binds to receptor
• G protein activated
• activates adenyl cyclase
• inactive ATP –> cyclic AMP
• initiates enzymes

Question 19

what happens at the ascending limb of the loop of henle?

Answer 19

1. Na+ and CL- are actively transported out of the ascending limb
2. this raises the Na+ and CL- concentration in the tissue fluid lowering the water potential, upper part of the membrane is impermeable to H2O

Question 20

what happens in the descending limb of the loop of henle?

Answer 20

3. water is drawn out of the decending limb by osmosis and Na+ and Cl- diffuse in down a concentration gradient
4. removing water from the decending limb concentrates Na+ and CL- in decending limb

Question 21

what happens as you reach the bottom of the loop of henle?

Answer 21

5. Na+ and Cl- diffuse out into the medulla