energy transfers in and between organisms

Question 1

what are the two stages of photosynthesis

Answer 1

light dependent and independent reaction (calvin cycle)

Question 2

where does the ldr occur

Answer 2

the thylakoids of chloroplasts (between the thylakoids and the stroma)

Question 3

why is the ldr not sufficient for a plant without the calvin cycle

Answer 3

it doesnt happen at night as its light dependent and doesnt produce glucose or enough atp (some tissues cant produce atp and atp cant be moved or stored as its too reactive)

Question 4

what does the ldr produce

Answer 4

oxygen (waste product), atp and nadph

Question 5

which ldr products are needed for the lidr

Answer 5

atp and nadph

Question 6

what is ps II

Answer 6

photo system II - a transmembrane complex containing chlorophyll

Question 7

what does the proton pump do

Answer 7

actively transports protons into the thylakoid using energy from electrons from chlorophyll

Question 8

what is ps I

Answer 8

photo system I - an electron carrier

Question 9

what makes up the electron transport chain (ETC)

Answer 9

psII, proton pumo, and ps I

Question 10

what is the first step of the ldr

Answer 10

1. light enters the thylakoid and excites 2 electrons (photoionisation) from the chlorophyll molecule (oxidation of psII). the proton pump gains 2 electrons (reduction). 2 electrons move up in energy level and move from psII to the proton pump.

Question 11

whats the 2nd step of the ldr

Answer 11

the reduced proton pump can actively transport protons (H+) from the stroma into the thylakoid space. this creates an electrochemical gradient between the thylakoid space and the stroma (more H+ in TS than stroma). the proton pump requires the bond with 2 electrons (e-) to work. these 2 e- become unstable

Question 12

whats the 3rd step of the ldr

Answer 12

the e- are transported from the proton pump (oxidation) to the electron carrier psI (reduction)

Question 13

whats the 4th step of the ldr

Answer 13

the protons diffuse down an electrochemical concentration gradient through the ATP synthase channel - this allows the enzyme to catalyse adp + Pi to atp. the channel turns to bring the substrates close together, adp is phosphorylated

Question 14

whats the 5th step of the ldr

Answer 14

2e- and a h+ are transferred to a coenzyme - a molecule that works with an enzyme to help it do its job - called nadp+ (+ means it can carry an e-) to make reduced nadp (nadph) ready to be used in the lidr. this occurs with the help of the enzyme dehydrogenase.

Question 15

what does dehydrogenase do

Answer 15

removes h ions or protons and sticks it to other things. in the ldr it removes proteins from atp synthae ad adds them to nadp+ to make nadp+h+. the 2e- then join to form nadph so the 2e- are at an even lower energy state

Question 16

6th step of the ldr

Answer 16

at this point the reaction will stop because the chlorophyll has given up its electrons but it needs to continuously produce atp and nadph for the lidr

Question 17

7th step ldr

Answer 17

photolysis of h2o occurs in the thylakoid space. this replenishes chlorophylls 2e-, addds to the h+ electrochemical gradient, and produces o2 as a byproduct

Question 18

what is photolysis

Answer 18

‘light breakdown’ - replenishing electrons by adding light energy to h2o to make 2e- 2h+ and oxygen

Question 19

where does the lidr occur

Answer 19

the stroma

Question 20

what is the lidr

Answer 20

a series of reactions that produce the organic compounds a plant needs including glucose

Question 21

what does nadph do in the lidr

Answer 21

supplies protons and electrons

Question 22

why will the lidr eventually stop without light

Answer 22

nadph and atp arent being replaced by the ldr

Question 23

what are the 3 stages of the lidr

Answer 23

1. carbon fixation
2. reduction
3. regeneration

Question 24

what happens during 1. carbon fixation in the lidr

Answer 24

the enzyme RUBISCO catalyses the reaction of ribulose bisphosphate (RuBP) and co2 into 2 x glycerate-3-phosphate (G3P). G3P is a 3 carbon sugar. if it is too hot then RUBISCO denatures and the plant will die

Question 25

what happens during 2. reduction in the lidr

Answer 25

reduced nadp (nadph) from the ldr reduces (gains electrons) g3p into 2 x triose phosphate (TP) using energy from atp

Question 26

what happens during 3. regeneration in the lidr

Answer 26

some TP is converted into useful organic compounds e.g glucose. some is regenrated into ribulose bisphosphate using energy from atp to maintain its supply

Question 27

how many times does the calvin cycle occur per glucose molecule

Answer 27

6. 6 x RuBP = 30 carbon atoms. + (6 x co2) = 36 carbon atoms. - 6 carbon atoms to make glucose (C6H12O6) = 30 carbon atoms. these 30 carbon atoms are regenerated into 6 x RuBP (5 carbon sugar)

Question 28

limiting factors of photosynthesis and which stage do they affect

Answer 28

- co2 concentration (lidr) - light intensity (ldr) - temperature (both) - chlorophyll (ldr) - water availability (ldr - photolysis)

Question 29

how can we measure photosynthesis

Answer 29

- presence of starch (using iodine) - volume of o2 released - volume of co2 used up (hydrogencarbonate indicator can measure the acidity (co2) of water (pH) - as co2 is used up, the water becomes less alkaline)

Question 30

how can we measure rate of photosynthesis

Answer 30

- volume of o2 produced per minute (cm^3/min^-1) - count bubbles of o2 released per minute

Question 31

what is the law of limiting factors

Answer 31

at any given moment, the rate of photosynthesis is limited by the factor that is least favourable

Question 32

what are the 4 stages of aerobic respiration

Answer 32

1. glycolysis 2. link reaction 3. krebs cycle 4. oxidative phosphorylation

Question 33

where does glycolysis occur

Answer 33

cytoplasm

Question 34

where does the link reaction occur

Answer 34

matrix

Question 35

where does the krebs cycle occur

Answer 35

matrix

Question 36

where does oxidative phosphorylation occur

Answer 36

through the cristae of the intermembrane space of mitochondria

Question 37

where does aerobic respiration take place

Answer 37

mitochondria

Question 38

what does glycolysis do

Answer 38

breaks down glucose into pyruvate whilst producing atp and harvesting protons (h+) and electrons (e-)along the way. it removes an e- to break the covalent bond between H and another molecule in glucose (carbon)

Question 39

step 1 glycolysis

Answer 39

glucose is phosphorylated into glucose phosphate using 2 x atp

Question 40

step 2 glycolysis

Answer 40

glucose phosphate breaks down into 2 x triose phosphate

Question 41

step 3 glycolysis

Answer 41

2 x TP are oxidised into 2 x pyruvate using 2 x nad+

Question 42

step 4 glycolysis

Answer 42

oxidation of 2 x tp into 2 x pyruvate using 2 x nad+ forms 2 x nadh and 4 x atp

Question 43

what is the yield of 1 glucose molecule undergoing aerobic respiration

Answer 43

- 2 x (net) atp --> 4 are produced but 2 are invested - 2 x nadh - 2 x pyruvate (3 carbon sugar) (gets into the matrix using active transport crossing the double membrane)

Question 44

what does the link reaction happen to

Answer 44

2 x pyruvate

Question 45

step 1 link reaction

Answer 45

pyruvate is oxidised (with nad) to remove hydrogen ions and released co2 (decarboxylation). an enzyme removes a h+ and an e- making the molecule unstable, causing it to drop a carbon with 2 o2 attached. this forms acetate (2 carbon sugar)

Question 46

step 2 link reaction

Answer 46

coenzyme A is added to acetate to produce acetyl CoenzymeA (ACoA)

Question 47

how many times does the krebs cycle occur for each glucose molecule

Answer 47

2 x for every glucose molecule (same as the link reaction)

Question 48

step 1 krebs cycle

Answer 48

acetyl CoA combines with a 4 carbon molecule to form a 6 carbon molecule

Question 49

step 2 krebs cycle

Answer 49

the 6 carbon molecule is oxidised into a 5 carbon molecule using nad+ (decarboxylation occurs)

Question 50

step 3 krebs cycle

Answer 50

the 5 carbon molecule is oxidised into a 4 carbon molecule using the coenzyme fad+ (fad+ holds 2 x H+ creating fadh2) (decarboxylation occurs). ATP is also generated during this step (the enzyme contains a Pi that turns adp to atp)

Question 51

what does oxidative phosphorylation involve the use of from the other stages of aerobic respiration

Answer 51

nadh and fadh2 from glycolysis, the link reaction, and the krebs cycle to start a series of redox reactions - energy is harvested from these reactions

Question 52

step 1 oxidative phosphorylation

Answer 52

nadh or fadh2 is oxidised into nad+ or fad+. this releases a proton into the matrix and 2e- are transferred to carrier a in the phospholipid bilayer (reduction). once carrier a is reduced it can transport a proton into the intermembrane space. the energy from these electrons allows carrier a to pump a proton into the intermembrane space as it changes the tertiary structure of the carrier slightly

Question 53

step 2 oxidative phosphorylation

Answer 53

the electrons are lost from carrier a (oxidation) and transported to carrier b (reduction)., this provides energy to pump another proton into the intermembrane space from the matrix

Question 54

step 3 oxidative phosphorylation

Answer 54

the electrons are lost from carrier b (oxidation) and transported to carrier c (reduction). this provides energy to pump another proton into the intermembrane space from the matrix

Question 55

step 4 oxidative phosphorylation

Answer 55

the electrons in the intermembrane space from an electrochemical gradient. they diffuse through an atp synthase channel protein to allow catalysis of adp + Pi to atp. the enzyme rotates in such a way that allows the protons to pass through. the diffusion of molecules down an electrochemical gradient is called chemiosmosis

Question 56

step 5 oxidative phosphorylation

Answer 56

the 2 electrons combine with 1/2 o2 - the final electron acceptor - in the matrix which reacts with 2 h+ to make h20. the o2 delivered to mitochondria through inhalation is missing 2 electrons (so theres room for the 2e- from carrier c). this is why h2o is a product of respiration. the role of o2 in this process is critical - in its absence the ETC and the transport of hydrogen would grind to a halt

Question 57

what is biomass

Answer 57

the mass of living material in a specific area at a given time. units: gm^-2 (land), gm^-3 (water)

Question 58

why do we measure biomass

Answer 58

for farming (measuring crop/meat yield), monitoring ecosystem health/productivity, and studying food chains

Question 59

how do we prepare dry mass

Answer 59

heat a sample up to 100 degrees celsius to evaporate the contained water (dont exceed 100 degrees to avoid burning the sample as this would take carbon from its biomols for the co2 in the sample therefore losing dry mass). weigh the sample until the mass is constant i.e no more water is being lost. to prepare dry mass you need to kill the organism so usually small samples are used

Question 60

how to find the chemical energy in dry biomass

Answer 60

- found using calorimetry (bomb calorimeter) - burn the sample to release its energy and measure the temperature rise of the surrounding water - a fuse wire lights the sample ; dont use a wooden splint as wood is biomass, using a fuse wire means nothing additional is being burnt - the water in the bomb calorimeter acts as an insulator to ensure no thermal energy is lost or gained - the stirrer ensures a uniform temperature change - the amount of energy needed to raise kg of wate by 1 degree celsius (the specific heat capacity) is 4184 J (4.184 for 1g) - we use the increase in water temperature to calculate the energy contained in the sample

Question 61

how much light energy from the sun is taken in by producers

Answer 61

1-3%

Question 62

why is only 1-3% of light energy from the sun taken in by producers

Answer 62

- over 90% is reflected by clouds back into space - not all wavelengths of light can be absorbed by pigments - light may not fall on a chlorophyll pigment molecule - limiting factors may prevent energy storage e.g co2 concentration

Question 63

what is gross primary production (GPP)

Answer 63

th total amount of energy stored by a producer in a given time (kJ m^-2 year^-1). plants use 20-50% of gpp in respiration, the remaining energy is stored as biomass

Question 64

what is net primary production (NPP)

Answer 64

the chemical energy store of plants (biomass)

Question 65

what is the equation to work out npp

Answer 65

npp = gpp (energy from photosynthesis) - respiratory losses

Question 66

how much of the npp stored by producers is transferred to biomass in primary consumers

Answer 66

5-10%

Question 67

why is only 5-10% of npp stored by producers transferred to biomass in primary consumers

Answer 67

- the whole organism isnt consumed e.g roots - the whole organism isnt digested e.g cellulose/fibre - some energy is lost in faeces and urine (inefficiency of digestion and absorption) - some energy is lost to the environment as heat from respiration

Question 68

what is the equation to work out the net biomass production of consumers

Answer 68

N = ingested energy (I) - (energy lost in faeces/urine (F) = respiratory losses (R))

Question 69

how much energy is transferred between primary consumers and secondary consumers

Answer 69

15-20%

Question 70

why is the energy transferred into biomass between primary and secondary consumers higher than that transferred between producers and primary consumers

Answer 70

theyre both animals so theres less that ant be utilised/eaten as theyre more similar

Question 71

why do food chains typically only have 4/5 trophic levels

Answer 71

energy transferred at each level decreases moving along the food chain. this is also why the biomass of secondary and tertiary consumers (g m^-2) is less than that of producers (e/g in a field there will be more grass than foxes)

Question 72

consequences of agricultural farming

Answer 72

- intensive farming of food has improved food productivity - intensive food production places large demand on soil - nutrients are removed but not replaced as crops are removed before they can decay

Question 73

how can we replenish nutrients in agricultural farming

Answer 73

- crop rotation gives soil time to recover different nutrients - fallow years - e/g grass (less leaching) followed by ploughing - allowing animals to grace as faeces/manure is organic fertiliser - using organic fertilisers e/g plant/animal remains, manure, slurry, bone meal - using inorganic fertilisers e/g NPKfertilisers (a blend of phosphorus, nitrogen, and mined potassium-containing rocks

Question 74

positives of nitrogenous fertiliser

Answer 74

- more amino acids (amine group), atp (adenosine), dna (bases) - more growth (protein synthesis) of leaves and roots - more photosynthesis leads to improved productivity

Question 75

what is nitrogen burn

Answer 75

when fertiliser has been added to such a point that water becomes a limiting factor. the water potential of the soil has decreased meaning water in roots of plants leaves via osmosis which dehydrates the crop. this reduces crop yield

Question 76

negatives of nitrogenous fertiliser

Answer 76

- reduced species diversity - grasses/nettles/weeds favour nitrogen rich soil and outcompete other species - leaching - nitrates (NO^3-) easi;y dissolve and are washed away leading to eutrophication

Question 77

describe the process of eutrophication

Answer 77

- nitrogenous fertiliser in ponds/water causes growth of algae/surface plants/algal bloom to block light - reduced/no photosynthesis so submerged plants die - saprobionts/saprobiotic microorganisms - aerobically respire/use oxygen in respiration - less oxygen is available for fish to respire/aerobic organisms die

Question 78

advantages of organic fertiliser

Answer 78

- acts as soil conditioner by containing slow release nutrients (needs to decay first)/improves drainage and aerates soil as its fibrous and porous/increases organic content of soil - contains a wider range of elements - production of artificial fertiliser is energy consuming - less leaching/slower release of nutrients as it needs to decay first so less risk of eutrophication

Question 79

what is the nitrogen cycle needed for

Answer 79

- amino acids (amine group) - dna/rna (bases) - atp (adenine) - nad/nadp (adenine)

Question 80

the nitrogen cycle

Answer 80

Question 81

the phosphorus cycle

Answer 81

Question 82

what is the phosphorus cycle needed for

Answer 82

- atp (triphosphate) - dna/rna (phosphodiester bonds/ sugar phosphate backbone) - phospholipids