5A (photosynthesis and respiration)

Question 1

why is energy important?

Answer 1

plants/ animals need energy for biological processes to occur so organism doesnt die
- photosynthesis, active transport, DNA replication, cell division, prot synthesis, muscle contraction, maintain body temp

Question 2

what is the equation for photosynthesis?

Answer 2

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 3

what is the equation for aerobic respiration?

Answer 3

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Question 4

what is the equation for anaerobic respiration in humans?

Answer 4

C6H12O6 -> lactate

Question 5

what is the equation for anaerobic respiration in plants/yeast?

Answer 5

C6H12O6 -> 2C2H5OH + 2CO2

Question 6

what are the properties of ATP?

Answer 6

- Small so manageable amount of energy released
- soluble- involves simple reaction to break down so quick
- stores/ releases manageable amount of energy at a time so no energy wasted as heat
- small, soluble so easily transported
- easily broken down so energy released instantaneously
- can be quickly remade
- can make other molecules more reactive through phosphorylation
- cant pass out of cell so cell always has immediate supply of energy

Question 7

what is the compensation point for light intensity?

Answer 7

particular level of light intensity where rate of respiration= rate of photosynthesis

Question 8

how can you work out the compensation point for a plant?

Answer 8

measure rate O2 is being produced and used by plant at diff light intensities
compensation point is light intensity at which oxygen is being used as quickly as it is produced (0 net oxygen generation)
could also measure CO2

Question 9

describe the structure of chloroplasts

Answer 9

• small, flat organelles surrounded by double membrane
• thylakoids are stacked into grana which are linked by lamella
• contain photosynthetic pigments (absorb light energy for photosynthesis)
• pigment is found in thylakoid membranes and are attached to proteins.
• protein and pigment is a photosystem (2 photosystems in plant)
• stroma contains enzymes, sugars, organic acids
  carbohydrates produced in photosynthesis that arent used straight away are stored as starch grains in stroma

Question 10

redox reactions

Answer 10

reduced- gained electrons, gained hydrogen, lost oxygen
oxidised- lost electrons, lost hydrogen, gained oxygen

Question 11

what is a coenzyme?

Answer 11

molecule that aids function of enzyme
they transfer chemical group from one molecule to another
eg NADP

Question 12

what happens in the light dependent reaction? where does it take place?

Answer 12

occurs in thylakoids
light absorbed by chlorophyll in photosystems which excites the electrons giving them more energy and they eventually leave molecule (photoionisation) chlorophyll now +
some energy released is used to produce ATP and some used to form reduced NADP
ATP transfers energy and NADP transfers hydrogen to light independent reaction
in process, H2O oxidised to O2

Question 13

what is the light independent reaction? where does it take place?

Answer 13

occurs in stroma
ATP and reduced NADP supply energy and hydrogen to make glucose from CO2
Calvin cycle

Question 14

what is the energy resulting from the photoionisation of chlorophyll used for?

Answer 14

making ATP through phosphorylation
making reduced NADP from NADP
splitting water into protons, electrons and oxygen (photolysis)

Question 15

what is non-cyclic phosphorylation?

Answer 15

produces ATP, reduced NADP, O2
photosystems are linked by electron carriers and this creates an electron transport chain

Question 16

what are the processes in noncyclic phosphorylation?

Answer 16

1) Light energy excites electrons in chlorophyll- light energy absorbed by PS2 and this excites electrons in chlorophyll so they move to higher energy level and are released from chlorophyll and move down electron transport chain to PS1

2) photolysis of water produces protons, electrons, oxygen- excited electrons that leave must be replaced. light energy splits water into protons, electrons and oxygen in photolysis H2O -> 2H+ + 1/2O2

3) energy from exited electrons makes ATP- exited electrons lose energy as they move down e- transport chain. this energy is used to transport protons to thylakoids so thylakoid has higher conc of protons than stroma. this forms proton grad across thylakoid membrane which protons move down into the stroma via ATP synthase which is embedded in thylakoid membrane. energy from this movement combines ADP and Pi to form ATP

4) Energy from exited electrons generates reduced NADP- light energy absorbed by PS1 which excites electrons again to an even higher level. finally, electrons transferred to NADP with proton from stroma to form reduced NADP

Question 17

what is the electron transport chain?

Answer 17

chain of proteins through which exited electrons flow

Question 18

what is an electron carrier?

Answer 18

protein that transfers electrons

Question 19

what is chemiosmotic theory?

Answer 19

the process of electrons flowing down electron gradient across membrane to drive ATP synthesis

Question 20

what is cyclic phosphorylation?

Answer 20

Produces ATP and only uses PS1
cyclic because electrons from chlorophyll molecule are passed to NADP but are passed back to PS1 via electron carriers. electrons recycled repeatedly . doesnt produce reduced NADP or oxygen and only small amounts of ATP produced

Question 21

what is the Calvin cycle

Answer 21

takes place in stroma
makes triose phosphate from CO2 and ribulose biphosphate
TP can be used to make glucose/ other useful organic substances

Question 22

describe the Calvin cycle

Answer 22

1) formation of glycerate-3-phosphate
CO2 enters through stomata and diffuses into stroma where it combines w RuBP catalysed by rubisco. forms unstable 6 carbon compound which breaks into 2 molecules of gycerate-3-phosphate (GP)

2) formation of triose phosphate
hydrolysis of ATP from ldr provides energy to reduce GP into TP (also 3 carbon). this requires H+ which come from reduced NADP. some TP converted into useful organic compounds, some continue in calvin cycle to regenerate RuBP

3) regeneration of RuBP
5/6 molecules of TP produced are used to regenerate RuBP. this uses rest of ATP produced by ldr

Question 23

what is a hexose sugar? how many times does the Calvin cycle need to occur to make one hexose sugar? why?

Answer 23

hexose sugar is 6-carbon sugar made from 2 TP
cycle needs to turn 6 times to make 1 hexose sugar as 3 turns produces 6 TP (2 made for every CO2). 5/6 used to regenerate RuBP so 3 turns, only 1 TP that is produced is used to make hexose sugar
but, 2 TPs needed so must happen 6 times

Question 24

what organic substances can be made from the Calvin cycle

Answer 24

carbohydrates- hexose sugars made from 2 TP and more complex made of multiple hexose sugars

lipids- made of glycerol synthesised from TP and fatty acids synthesised from GP

amino acids- some made from GP

Question 25

what are the ideal conditions for photosynthesis?

Answer 25

high light intensity- provide energy for ldr certain wavelength- only some absorbed by chlorophyll 25 degrees- below 10, enzymes (ATP synthase, rubisco) inactive and above 45, denature. high temp also means stomata close to not lose water so photosynthesis slows as less CO2 enters CO2 at 0.4% (usually 0.04 in atmosphere) increased increases ror but higher, stomata start to close water- too little= photosynthesis has to stop, too much= waterlogged soil (reduced uptake of minerals needed to make chlorophyll)

Question 26

what are the limiting factors of photosynthesis?

Answer 26

light, temperature, carbon dioxide

Question 27

how do farmers create optimum growing conditions?

Answer 27

add CO2 by burning small amount of propane in CO2 generator light gets in through green house glass, lamps at night green houses trap heat energy from sun which warms air, heaters/ coolers used to keep constant temp, air circulation systems- make temp even throughout

Question 28

practicals

Question 29

describe the structure of mitochondria

Answer 29

folds (cristae) in inner membrane provide large sa to maximise resp

Question 30

what are the coenzymes in respiration?

Answer 30

NAD, coenzyme A, FAD NAD and FAD transfer hydrogen between molecules so can reduce/oxidise molecules coenzyme A transfers acetate between molecules

Question 31

what are the stages of aerobic respiration? where do they all take place?

Answer 31

glycolysis- cytoplasm of cell link reaction- mitochondrial matrix Krebs cycle - mitochondria oxidative phosphorylation- mitochondria

Question 32

what are the stages of anaerobic respiration?

Answer 32

glycolysis- cytoplasm products of glycolysis converted to ethanol or lactate

Question 33

what are the stages of glycolysis? what happens in each?

Answer 33

makes 2 pyruvate (3C) from glucose (6C) 1) glucose phosphorylated using pi from ATP creates 1 molecule of glucose phosphate and 1 molecule of ADP ATP used to add another Pi forming hexose bisphosphate which is then split in 2 triose phosphate 2) oxidation triosephosphate is oxidised (loses H) forming 2 pyruvate NAD collects H+ forming 2 reduced NAD. 4 ATP produced but 2 used in stage 1 so net gain of 2

Question 34

what are the products of glycolysis (aerobic resp)?

Answer 34

2 reduced NAD- go to oxidative phosphorylation 2 pyruvate- actively transported to matrix for link reaction 2 ATP (net)- used for energy

Question 35

what are the products of glycolysis (anaerobic respiration)?

Answer 35

pyruvate produced is converted to ethanol (alcoholic fermentation- plants/yeast) or lactate (lactate fermentation- animals)) using reduced NAD this regenerates oxidised NAD so glycolysis can continue w lack of O2 see diagrams on page 40

Question 36

what is the link reaction?

Answer 36

converts pyruvate to acetyl coenzyme A pyruvate is decarboxylated so 1C removed in form of CO2 at same time, pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD acetate combined with CoA to form acetyl CoA no ATP produced

Question 37

how many times do the link reaction and Krebs cycle occur per glucose molecule?

Answer 37

2 pyruvate formed per glucose molecule that enters glycolysis so link reaction and krebs cycle happen twice for every glucose

Question 38

what are the products of the link reaction?

Answer 38

2 acetyl CoA- to Krebs cycle 2 CO2- released as waste 2 reduced NAD- to oxidative phosphorylation

Question 39

what is the Krebs cycle?

Answer 39

produces reduced coenzymes and ATP involves redox reactions in matrix of mitochondria happens once per pyruvate

Question 40

describe the Krebs cycle

Answer 40

1) formation of 6C compound- acetyl CoA combines w 4C molecule (oxaloacetate) to form 6C molecule (citrate), coA goes back to link reaction to be reused 2) formation of 5C compound- 6C molecule is converted to 5C molecule. decarboxylation occurs where CO2 is removed. dehydrogenation also occurs- the hydrogen is used to produce reduced NAD 3) regeneration of oxaloacetate- 5C molecule is converted to 4C molecule. decarboxylation and dehydrogenation occur producing 1 reduced FAD and 2 reduced NAD. ATP produced by direct transfer of phosphate group from intermediate compound compound to ADP (substrate level phosphorylation) citrate has now been converted to oxaloacetate

Question 41

what are the products of the Krebs cycle

Answer 41

1 coA- reused in next link reaction oxaloacetate- regenerated for use in next Krebs cycle 2CO2 reduced as waste 1 ATP- used for energy 3 reduced NAD- to oxidative phosphorylation 1 reduced FAD- to oxidative phosphorylation

Question 42

describe oxidative phosphorylation

Answer 42

1) H atoms released from reduced NAD and reduced FAD as theyre oxidised to NAD and FAD. H atoms split into H+ and e- 2) e- move down electron transport chain, losing energy at each carrier 3) this energy used by electron carriers to pump protons from matrix to intermembrane space 4) conc of protons is now higher in intermembrane space so forms electrochemical grad 5) protons move down electrochemical grad back across inner mitochondrial membrane and into matrix via ATP synthase. this movement drives synthesis of ATP from ADP and Pi 6) ATP production driven by movement of H+ ions across membrane is called chemiosmosis 7) in matrix, at end of transport chain, protons, electrons and oxygen join to form water. oxygen is the final electron acceptor

Question 43

what is oxidative phosphorylation?

Answer 43

process where energy carried by electrons from reduced coenzymes is used to make ATP involves electron transport chain and chemiosmosis

Question 44

how does a cell make 32 ATP from 1 glucose molecule?

Answer 44

glycolysis produces 2 ATP and 2 reduced NAD (2.5 ATP each) link reaction produces 2 reduced NAD (2.5 ATP each) krebs cycle produces 2 ATP, 6 reduced NAD (2.5 ATP each) and 2 reduced FAD (1.5 ATP each)

Question 45

mitochondrial diseases

Answer 45

affect functioning of mitochondria affect how proteins involved in oxidative phosphorylation or krebs cycle function, reducing ATP production may cause anaerobic resp to increase which results in lactate production which causes muscle fatigue and weakness. some lactate will diffuse into bloodstream leading to high lactate conc in blood

Question 46

respiration experiments

Question 47

compare/ contrast chemiosmotic theory in photosynthesis vs respiration

Answer 47

photosynthesis - occurs in thylakoids and stroma of chlorophyll -water isnt produced - photolysis of water - only green plants - protons pumped from stroma to thylakoid - transforms light energy into chemical energy respiration - occurs in intermembrane space and matrix of mitochondria - water is produced - photolysis of water isnt required - all living cells - proton pumped from matrix into intermembrane space - transforms chemical energy from food into ATP both - active transport - transport of protons - ATP synthase channels

Question 48

why isnt all light used in photosynthesis? or is it in food chains topic?

Answer 48

- some reflected- green (only absorbs certain wavelengths) - not all lands on a leaf - gaps between chloroplasts