paper dos

Question 1

importance of maintaining glucose concentration

Answer 1

sufficient availability of respiratory substrate, stops water potential causing cells to burst or shrivel

Question 2

role of negative feedback

Answer 2

restores systems to their original level

Question 3

what creates a greater degree of control in feedback systems?

Answer 3

having separate systems to control different departures from the original state

Question 4

how to explain action of hormones w blood glucode

Answer 4

‘activating enzymes involved in the conversion of…’

Question 5

second messenger- what hormones trigger it and what enzyme does this activate

Answer 5

glucagon and adrenaline

adenylate cyclase

Question 6

body parts involved in osmoregulation

Answer 6

hypothalamus and posterior pituitary gland

Question 7

where is glucose reabsorbed in the kidney?

Answer 7

proximal convoluted tubule

Question 8

process of glucose reabsorbtion

Answer 8

products such as glucose and amino acids are reabsorbed via co-transport with sodium ions through podocytes

Question 9

which limbs of the loop of henle are permeable to what?

Answer 9

ascending- ions only

descending- water, ions also move in

Question 10

net atp production from 1 krebs cycle

Answer 10

1 molecule

Question 11

where do the electrons in the electron transfer chain come from?

Answer 11

reduced coenzymes

Question 12

light-dependent reaction (5)

Answer 12

• chlorophyll absorbs light- it is photoionised
• some energy from photoionisation is conserved in the production of atp and nadph
• some atp is also produced from chemiosmosis, using energy from the electron transfer chain
• h+ are pumped into the thylakoid and catalyse atp synthase by moving out
• photolysis of water produces protons, electrons (which enter the etc) and oxygen

Question 13

gpp definition

Answer 13

chemical energy store in plant biomass in a given area or volume

Question 14

npp definition

Answer 14

chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

Question 15

net production of consumers

Answer 15

chemical store of ingested food - (faeces and urine + respiratory losses)
n = i - (f+r)

Question 16

example unit of productivity

Answer 16

kJ ha-1 yr-1

Question 17

nitrogen fixation

Answer 17

atmospheric nitrogen > ammonium ions, or other ammonium-containing products

Question 18

nitrification

Answer 18

ammonium > nitrate via nitrite

Question 19

denitrification

Answer 19

nitrate > atmospheric nitrogen

Question 20

ammonification

Answer 20

breakdown of ammonium-containing products into ammonium ions

Question 21

why is leaching bad

Answer 21

nitrates in water can cause problems with oxygen transport in babies, linked with increased risk of stomach cancer

Question 22

eutrophication

Answer 22

• algal growth as nutrient availability no longer limiting, causing algal blooms
• less light at lower depths
• light becomes the limiting factor for plants and algae lower down
• dead plants and algae allow more growth of saprobiontic bacteria
• the bacteria use up the oxygen
• fish and other aerobic organisms die

Question 23

why is eutrophication bad

Answer 23

populations of anaerobic organisms rise, and decompose the dead material, releasing more nitrates/other toxic material so water is bad

Question 24

process that inhibit transcription

Answer 24

increased methylation

decreased acetylation

Question 25

what is epigenetics?

Answer 25

heritable changes in gene function, without changes to the base sequence of dna

Question 26

action of oestrogen

Answer 26

• easily diffuses through phospholipid bilayer
• binds with the receptor on a transcription factor
• dna binding site on transcription factor changes shape, now complementary to dna
• enters through nuclear pore and stimulates transcription of the gene

Question 27

acetylation on transcription

Answer 27

• decreased makes the histones more positive
• so more attracted to phosphate groups on dna
• less accessible to transcription factors

Question 28

methylation on transcription

Answer 28

• increased prevents binding of transcription factors

- induces deacetylation of histones

Question 29

where do sirnas come from?

Answer 29

double stranded rna bound to an enzyme

Question 30

what are schwann cells?

Answer 30

myelin-containing cells that provide electrical insulation/general protection

Question 31

where is myelin?

Answer 31

in the cell membranes of schwann cells

Question 32

open at resting potential

Answer 32

k+ channels, net movement of na+ out of pump

Question 33

when do na+ channels close?

Answer 33

when +40mv potential has been established

Question 34

what causes hyper-polarisation?

Answer 34

outward transport of k+ through the channels that are able to close

Question 35

repolarisation

Answer 35

closable k+ channels shut, resting potential restored

Question 36

name for the node of ranvier thing

Answer 36

saltatory conduction

Question 37

greater axon diameter

Answer 37

increases speed of conductance due to less ion leakage

Question 38

types of summation

Answer 38

spatial- multiple neurones

temporal- high frequency of neurotransmitter release from one neurone

Question 39

3 purposes of the refractory period

Answer 39

one direction only
discrete impulses
limits number of action potentials

Question 40

action of an inhibitory synapse

Answer 40

• neurotransmitter causes chloride ion channels to open
• cl- move in, also triggers k+ channels to open, so they move out
• membrane potential drops
• this hyperpolarisation makes it less likely that an action potential will be triggered