paper two

Question 1

what are the thylakoid membranes?

Answer 1

folded membranes which contain photosynthetic proteins (chlorophyll) and embedded, transmembrane electron carrier proteins which are both involved in LDR

Question 2

what is the stroma?

Answer 2

fluid centre which contains enzymes involved in LIR

Question 3

inner and outer membrane of chloroplast

Answer 3

controls what can enter and leave organelle

Question 4

what is chlorophyll

Answer 4

a mix of coloured pigments that can absorb light
1)chlorophyll a- blue/green
2) chlorophyll b- yellow/green
3) carotene- orange
4) xantophyll- yellow
5) phaeophytin- grey

Question 5

what is the advantage of multiple pigments

Answer 5

a wider range of wavelengths are absorbed so more light energy is absorbed for LDR (more photoionisation of chlorophyll)

Question 6

3 stages of light dependent reaction

Answer 6

1) photoionisation of chlorophyll
2) photolysis
3) chemiososis

Question 7

photolysis

Answer 7

light energy absorbed by chlorophyll and splits water into oxygen, protons, electrons
protons picked up by nadp to form reduced nadp and use in LIR
electrons passed along chain of electron carrier proteins
oxygen either used in respiration or diffuses out leaf through stomata

Question 8

photoionisation of chlorophyll

Answer 8

light energy absorbed by chlorophyll
electrons become excited
move up energy level to leave chlorophyll
some energy from released electron is used to make atp and reduced nadp in chemiosmosis

Question 9

chemiosmosis process

Answer 9

1) electrons that gained energy and left the chlorophyll move along a series of electron-carrier proteins embedded within thylakoid membrane
2) as they move along they release energy and some of the energy from electrons is used to pump the protons across chloroplast membranes
3) electrochemical gradient created- protons pass through atp synthase resulting in production of ATP
4) protons combine with coenzyme NADP to become reduced NADP- as protons move down conc gradient (chemiosmosis)

Question 10

light independent reaction

Answer 10

1) co2 reacts with RuBP to form 2 molecules of glycerate 3 phosphate (GP) catalysed by rubisco
2) GP reduced to triose phosphate (TP) using atp and by accepting H from reduced NADP
3) some of carbon from TP leaves cycle to be converted ino useful organic substances
4) rest of molecule used to regenerate RuBP with energy released from hydrolosis of ATP
5) glucose can then join to form sucrose, cellulose and starch and also can be converted into glycerol and combine w fatty acids to make lipids for plant

Question 11

limiting factors for photosynthesis

Answer 11

temp
co2 conc
light intensity

Question 12

agriculture practices that incorporate techniques to remove limiting factors and increase rate of photosynthesis

Answer 12

• growing plants under artificial lighting to maximise light intensity
• heating a greenhouse to increase temp
• burning fuel (e.g. parifin burners) to release more co2

Question 13

aerobic respiration stages

Answer 13

1) glycolosis (cytoplasm)
2) link reaction (itochondrial matrix)
3) krebs cycle (mitochondrial matrix)
4) oxidative phosphorylation (cristae)

Question 14

glycolosis (sugar splitting)

Answer 14

1) substrate level phosphorylation- glucose has 2 phosphate groups added to it from 2 ATP
2) phsophorylation makes the glucose 2 phosphate unstable and it splits into 2 3-carbon compounds (TP)
3) the 2 TP molecules are oxidised by the removal of H from each to form 2 pyruvate molecules- H is picked up by 2 NAD molecules to becoe reduced NAD- releases 4 ATP- net amount of ATP produced from glycolosis is 2 ATP

Question 15

link reaction

Answer 15

1) NAD and pyruvate actively transported into mitochondrial matrix
2) pyruvate oxidised to acetate
3) NAD picks up hydrogen and becomes reduced NAD
4) acetate combines w coenzyme A to produce acetylcoenzyme A
5) 2x acetyl coA
2x CO2 released
2x reduced NAD

Question 16

krebs cycle

Answer 16

1) acetyl CoA reacts w 4 carbon molecule, releasing coenzyme A and producing 6 c molecule that enters kreb cycle
2) oxidation- reduction reactions- krebs cycle generates 8 reduced coenzymes, 2 atp by substrate- level phosphorylation and 4CO2s are lost

Question 17

oxidative phosphorylation

Answer 17

1) reduced coenzymes accumulate in mitochondrial matrix- release their protons and electrons
2) electrons passed down series of electron carrier proteins embedded inner mitochondrial membrane losing energy as it moves
3) energy pumps protons from metrix into intermembrane space by active transport
4) creates electrochemical gradient
5) protons move down gradient back into matrix via ATP synthase making ATP
6) o2 is final electron acceptor in etc- combines w electrons and protons to for h2o

Question 18

anaerobic respiration

Answer 18

1) occurs in cytoplasm of cell only
2) pyruvate produced in glycolosis reduced to form ethanol and co2 (in plants/microbes) or lactate (in animals) by gaining the hydrogen from reduced NAD
3) oxidises NAD so that it can be reused in glycolysis and ensures ATP is continued to be produced

Question 19

efficiency in respiration

Answer 19

1 reduced NAD can result in a yeild of 3 ATP molecules whereas 1 reduced FAD can result in a yield of 2 ATP molecules
so total yieldof ATP from 1 glucose molecule in aerobic resp should be 38 molecules of ATP- 32% efficient
anearobic is less efficient because only 2 ATP are produced from 1 glucose molecule

Question 20

biomass

Answer 20

remaining energy in a organism after respiration and excretion
can be measured in terms of dry carbon mass or dry mass of tissue per given area

Question 21

GPP

Answer 21

gross primary production
the chemical energy stored in plant biomass in a given area or volume (total energy resulting from photosynthesis)

Question 22

NPP

Answer 22

net primary production
the chemical energy stored in plant biomass taking into account the energy that will be lost due to respiration

Question 23

equation to work out NPP

Answer 23

NPP= GPP- R
R= respiration

Question 24

to work out the net prouction of consumers

Answer 24

N= I-(F+R)
I= chemical energy stored in ingested food
F= chemical energy lost to environment in faeces and urine
R= respiratory losses

Question 25

units for rates of productivity

Answer 25

KJ ha-1year-1
KJ= unit for energy
recorded as per unit to standardise results so environments can be compared
per year to take into account impact seasons will have on rain, light and heat- provides annual average to allow fair comparisons between environments

Question 26

types of nutrient cycles

Answer 26

nitrogen and phosphorous

Question 27

role of mycorrhizae

Answer 27

fungal associations between plant roots and beneficial fungi
fungi entwined around plant roots provide large SA for h2o and mineral absorption
fungi part of mycorrhizae acts lik sponge and can absorb and hold onto h2o and minerals surrounding root
SO in times of drought can store h2o and minerals (mutualistic relationship)- plant provides fingi w carbs

Question 28

nitrogen cycle

Answer 28

needed to create aas/proteins, dna, rna and atp
1) NITROGEN FIXING- nitrogen fixing bacteria can break triple bond between 2 nitrogen atoms in nitrogen gas in atmosphere and fix nitrogen into ammonium ions
2) NITRIFICATION- ammonium ions in soil converted to nitrite then nitrate by nitrifying bacteria- 2 stage oxidation reaction
3) DENITRIFICATION- returns nitrogen back to nitrogen gas in atmosphere so cant be absorbed by plants using anaerobic denitrifying bacteria- NOT USEFUL
4) AMMONIFICATION- proteins, urea and dna can be decomposed in dead matter and waste by saprobionts- bacteria/fungi that can digest waste extracellularly and return ammonium to soil (saprobiotic nutritions)

Question 29

phosphorous cycle

Answer 29

Phosphorus in rocks is slowly released into the soil and into water sources in the form of phosphate ions (PO₄³⁻) by the process of weathering (the slow breaking down and erosion of rocks over time)
Phosphate ions are taken up from the soil by plants through their roots or absorbed from water by algae
Phosphate ions are transferred to consumers during feeding
Phosphate ions in waste products and dead organisms are released into the soil or water during decomposition by saprobionts
The phosphate ions can now be taken up and used once again by producers or may be trapped in sediments that, over very long geological time periods may turn into phosphorus-containing rock once again

Question 30

fertilisers

Answer 30

added to soil to replace nitrate and phosphate lost when plants harvested and removed from nutrient cycles as crops
natural (manure)
artificial (inorganic chemicals)

Question 31

natural fertilisers

Answer 31

cheaper- often free if the farmer owns animals
but exact mineral proportions cant be controlled

Question 32

artificial fertilisers

Answer 32

chemicals created to contain exact proportions of minerals
(+) inorganic substances are more h2o soluble so more of these ions dissolve in h2o surrounding the soil
(-) theirr high solubility means larger quantities are washed away w rainfall so have greater impact on environment

Question 33

leaching

Answer 33

when h2o soluble compounds are washed away into rivers or ponds- if nitrogen fertilisers leach into waterways it causes eutrophication

Question 34

eutrophication

Answer 34

nitrates leached from fertilised feilds stimulates growth of algae in pond
excessive algae growth creates blanket on surface of h2o which blocks out light
plants cant photosynthesise and die
bacteria within h2o feed and respire on dead plant matter
increase in respiring bacteria which uses up o2 within h2o
fish die and other aquatic organisms die due to lack of dissolved o2 in h2o

Question 35

what is a stimulus

Answer 35

a detectable change in the environment
organisms increase chance of survival by responding todiff response mechanisms

Question 36

what is a tropism

Answer 36

the response of plants to stimuli via growth
can be +ve (growing towards stimulus)
can be -ve (growing away from stimulus)
plants respond to light gravity light and h2o
controlled by specific growth factors e.g. IAA

Question 37

what is IAA

Answer 37

type of auxin
controls cell elongation in shoots and inhibit growth of cells in roots
made in tip of roots and shoots but can diffuse to other cells

Question 38

positive phototropism

Answer 38

shoots need light for LDR so plants grown and bend towards light controlled by IAA

Question 39

plants grow towards light process

Answer 39

1) shoot tip cells produce IAA
2) cell elongation in shoots
3) IAA diffuses to other cells
4) if unilateral light- IAA will diffuse towards shaded side of shoot- higher conc of IAA there
5) IAA causes the cells on shaded side to elongate more so plant bends towards light

Question 40

negative phototropism

Answer 40

1) roots dont need light
2) high conc of IAA inhibits cell elongation
3) root cells elongate more on lighter side
4) root bends away from light

Question 41

negative gravitropism

Answer 41

shoots
1) IAA diffuse from upper side to lower side of shoot due to gravity
2) if plant vertical- plant cells elongate and plant grows up
3) if on side- shoot bends upwards

Question 42

positive gravitropism

Answer 42

roots
1) IAA moves to lower side of roots due to gravity
2) upperside elongates more
3) root bends down towards gravity and anchors plant in

Question 43

taxes

Answer 43

organism moves entire body towads favourable stimulus or away from unfaqvourable
towards= positive taxis
away= negative taxis
PHOTOTAXIS- move away from light but towards dark environments to help avoid dehydration, predators and find food
CHEMOTAXIS- move towards certain chemicals to aid survival

Question 44

kinesis

Answer 44

organism changes speed of movement and its rate changes direction
moves from beneficial to harmful stim= increase rate it changes direction
surrounded by -ve stim= rate of turning decreases

Question 45

simple reflex

Answer 45

stimulus- receptor- coordinator- effector- response
receptors= parcinian corpsucle, rods and cones

Question 46

what is the parcinian corpsucle

Answer 46

receptor that responds to pressure changes
deep in skin
single sensory neuron wrapped w layer of tissue seperated by gel
has channel protiens in plasma membrane

Question 47

parcinian corpsucle process

Answer 47

1) plasma membranes contain channelproteins that allow ion transportation and membranes surrounding neurones have stretch mediated sodium channels
2) cahnnels open and allow influx of sodium- diffuse into sensory neuron when sretched
3) resting state- too narrow for na ions to diffuse- resting potential maintained
4)when pressure applied stretch channels deform and widen- na ions can diffuse- generator potential

Question 48

photoreceptors in the retina

Answer 48

rods and cones

Question 49

rods

Answer 49

process images as black ad white
cant distinguish diff light wavelengths
detect light of low intensity- lots of rods connect to 1 sensory neuron (retinal convergence)
pigment of rod cells (rhodopsin) breaks down by light energy to create generator potential
brain cant distinguish between seperate sources of light that stimulated it due to retinal convertgence
low visual acuity

Question 50

cones

Answer 50

3 types w diff types of iodopsin pigment- red blue green
absorb all diff wavelengths of light
iodopsin broken down if high light intensity
only 1 cone connects to bipolar cell
no spatial summation
high visual acuity

Question 51

distribution of rods and cones

Answer 51

distribution of retina uneven
most cone cells in fovea- recieves highest light intensity
rod cells located further away

Question 52

control of cardiac cycle

Answer 52

cardiac muscle= myogenic- contracts on own but rate controlled by wave of electrical activity
1) SAN release wave of depolarisation
2) AVN release another was when 1st reaches it- non conductive layer between atria and ventricles prevents wave from travelling down ventricles
3) bundle of his (in septum) conducts and passes on wave down septum and puryne fibres in ventricle walls
4) apex and v walls contract- short delay before- AVN transmits 2nd wave so ventriclels can fill

Question 53

control of heart rate

Answer 53

medulla oblongata via autonomic NS- node increase HR via sympathetic and decreases via parasympathetic
changes due to PH and blood pressure detected by chemoreceptors and pressure receptors

Question 54

response to pressure

Answer 54

if too high- can damage walls of arteries
if too low- insufficient supply of o2 blood

Question 55

response to PH

Answer 55

decrease in high respiratory rate- excess lactic acid must be removed raapidly to prevent enzymes denaturing

Question 56

response to high blood pressure

Answer 56

1- stimulus- increased pressure
2- receptor- pressure receptors stretch
3- coordinator- more impulses sent to medulla than to parasympathetic to decrease freq of impulses
4- effector- cardiac muscle- SAN tissues
5- response- reduced heart rate

Question 57

parts of motor neuron

Answer 57

cell body- contains organelle- proteins and neurotransmitters made here
dendrites- carry action potential to surrounding cells
axon- conductive long fibre carrying nervous impulse
nodes of ranvier- gaps between myelin sheath

Question 58

resting potential

Answer 58

1) diff between electrical charge inside and outside neuron
2) more positive ions outside- inside more -ve (-70mv)
3) resting p maintained by sod-pot pump
4) moves 2 pot ions in and 3 sod out creates electrochemical grad so pot diffuses out and sod in- more pot moved out

Question 59

action potential

Answer 59

neurons voltage increases beyond set point from resting p
1) stim provides energy for sod gated channels to open
2) sod influx- increases +veity, more channels open, more sod
3) threshold of 40mv inside= gated channels close, pot channels open
4) pot out, axon= -ve again, repolarises axon
5)axon more -ve than -70mv so hyperpolarised
6) pot channels close and sod-pot pump restores normal activity

Question 60

all or nothing principle

Answer 60

depolaristion doesnt exceed -55mv threshold= no action potetial= nothing
stimulus that triggers depolarisation to -55mv will peak1