respiration

Question 1

write an account outlining the similarities and differences in the ways that mitochondria and chloroplasts generate a proton gradient and synthesis ATP (10)

Answer 1

similarities
* both involve transport of electrons
* electron transport chain/cytochrom chain/ carriers in membrane
* energy released used to pump
* protons
* creates proton gradient/pH gradient across the membrane
* protons diffuse down a concentration gradient
* stalked particles/ ATP synthestase
* ref to chemiosmosis differences
respiration
* substrate level phosphorylation
* electrons from hydrogens produced in respiration/ reduced carriers
* hydrogen from glucose/fats/amino acids
* electrons combine/reduce H+ and O to form water/pxygen is final electron acceptor
* chemiosomosis occurs - mitochondria,inner membrane
* low pH/H+ mitochondria inter membrane space
* three types of proton pump in mitochondria
photosynthesis
* no subsrate level phosphorylation
* electrons come from chlorophyll/water
* production of NADPH+ increases the proton gradient
* cyclic phosphorylation- electrons back to chlorophyll { non cyclic to NADP/ final electron acceptor is NADP}
* on the thylakoid membranes of chloroplasts
* chloroplast thylakoid cavity
* one type of proton pump in chloroplasts

Question 1

give the name of the reaction resulted in the bond between the second and third phosphate groups on ATP (1)

Answer 1

condensation/phosphorylation

Question 2

what is the pentose sugar in ATP (1)

Answer 2

ribose

Question 3

what is the organic base in ATP (1)

Answer 3

adenine

Question 4

describe how energy is released from ATP (3)

Answer 4

• hydrolysis/hydrolyse
• enzyme/ATPase
• ATP to ADP and Pi/phosphate
• 30.6 kj per mol

Question 5

what is the function of circular DNA in mitochondria (1)

Answer 5

• codes of primary structure of protein or enzyme of polypeptide
• allows mitochondria to replicate
• self replication

Question 6

explain how pH in outer membrane of mitochondria becomes acidic (3)

Answer 6

• chemiosmosis
• protons
• pumped from matrix into inter membrane space
• use energy from passage of electrons along ETC
• accumulation of hydrogen ions

Question 7

describe the function of enzymes and coenzymes (carriers) in the process of respiration (10)

Answer 7

• decarboxylase
• removes CO2
• in link reaction/Krebs
• dehydrogenase
• removes hydrogen
• in glycolysis/links/krebs
• ATP synthetase
• produces ATP from ADP and PI
• NAD acts as a hydrogen carrier/is reduced
• in glycolysis/link/krebs
• FAD acts as a hydrogen carrier/is reduced
• in krbs
• reduced NAD/FAD carry protons/electrons to ETC
• coenzyme A
  joined with/carries an acetyl/acetate group
  electron carriers in ETC

Question 8

the proton gradient can be maintained as long a reduced NAD is available in the mitochondrion explain the reasons for reduced NAD being required to maintain a proton gradient (2)

Answer 8

• reduced NAD supplies protons
• and brings high energy electrons
• electrons supply energy for proton pumping/fuels proton pumps

Question 9

where in the cell does glycolysis occur (1)

Answer 9

cytoplasm/cytosol

Question 10

outline the pathway for the production of triose phosphate in glycolysis (3)

Answer 10

• glucose is phosphorylated by ATP
• two phosphorylations/production of hexose/fructose biphosphate
• hexose biphosphate is split from 6C to 3C

Question 11

explain the biochemical reactions for anaerobic respiration in a tissue in humans despite the fact that lactate is toxic in high concentrations (3)

Answer 11

• allows reduced NAD to be converted back to NAD/ regenerate reduced NAD/ without oxygen reduced NAD not converted to NAD by electron transport chain/krebs/link reaction / allowing ATP production/
• without oxygen no ATP production by oxidative phosphorylation
• allows glycolysis/substrate level phosphorylation to continue
• no oxygen to act as a final hydrogen/electron acceptor/NADH must find an alternatie hydrogen acceptor/must use pyruvate

Question 12

describe why anaerobic reaction occurs in muscle fibres when a short burst of very rapid ATP production is needed suggest a reason for this (1)

Answer 12

• only glycolysis required/shorter metabolic pathways
• oxygen supply too slow/no need for oxygen supply/diffusion
• no need to carry out krebs cycle/electron transport/oxidative phosphorylation
• no need to build up a proton gradient
• no need to transport pyruvate into the mitochondria

Question 13

explain the importance of ATP in cells (3)

Answer 13

• suitable function of ATP/protein synthesis/active transport/muscle contraction
• different types of energy can be transferred into a common fomr
• only 1 molecule needed to transfer energy to chemical reactions
• energy can be supplied in small amounts 30.6KJ less energy/heat waster
• easily transported across membranes
• single enzyme/only ATPase needed to release energy from ATP
• single bond needed to be broken/one step reaction to release energy

Question 14

explain why ATP is sometimes called the universal energy currency (2)

Answer 14

• used by all organisms/species
• to provide energy/fuel for nearly all biochemical reactions

Question 15

Name the first three stages of respiration and where thet occur (3)

Answer 15

• glycolysis - cytoplasm
• link reaction - matrix of mitochondria
• krebs cycle - matrix of mitochondria

Question 16

which of these stages will operate in the absecence of oxygen in respiration (1)

Answer 16

glycolysis

Question 17

name the enzyme responsible for the production of CO2 (1)

Answer 17

decarboxylase

Question 18

briefly describe how reduced FAD and reduced NAD are used to create an electrochemical gradient (4)

Answer 18

• reduced NAD and reduced FAD pass electrons to the electron transport chain
• the high energy electrons/electrons provide energy
• used to power proton pumps
• on the inner mitochondrial membrane/cristae
• which pump H+ into the inter membrane space
• reduced NAD powers all pumps/reduced FAD passes to 2nd pump

Question 19

Name the two enzyme types involved in the converstion of pyruvate to acetyl CoA (2)

Answer 19

• dehydrogenase
• decarboxylase

Question 20

suggest a suitable tissue to examine mitochondrial function and explain why you have chosen this tirrue with respect to patient safety (2)

Answer 20

• (skeletal) muscle
• high numbers of mitochondria and easy to access

Question 21

what could be deduced if the oxygen consumption was low with the pyruvate as a substrate but high with a-ketoglutarate as a substrate (2)

Answer 21

low with pyruvate
* the pathway leading to acetyl CoA/link reaction is not working / enzymes/dehydrogenase/decarvoxylase are not active/there is no reduced NAD for the electron transport chain so no O2 needed
high with a-ketoglutarate
* the pathway between a-ketoglutarate and the rest of the cycle is working correctly rhere is enough reduce NAD/FAD to drive the ETC which needs O2

Question 22

what could be deduced if there was a build up of any one of the krebs cycle intermediates (1)

Answer 22

• enzymes catalysing the conversion of the molecule to the next in the cycle are not functional
• the molecule cannot be converted to the next intermediate
• build up of reduced NAD and FAD

Question 23

explain why there is a raised blood lactate level in many patients with mitochondrial disease (2)

Answer 23

• the krebs cycle/link reaction/electron transport chain is not working as well
• pyruvate levels build up/increase/higher
• excess pyruvate/NADH2 is converted to lactate

Question 24

describe the metabolism of pyruvate in the anaerobic respiration of glucose in yeast (4)

Answer 24

* pyruvate is converted to ethanal * with the removal of CO2/by decarboxylation * ethanal is reduced to ethanol * using NADH2/reduced NAD/NADH * pyruvate converted to ethanol

Question 25

describe the position of the high energy bond of ATP (1)

Answer 25

the bond between nthe terminal/last two phosphate groups on ATP

Question 26

suggest why substate level phosphorylation is referred to as the simplest and oldest way to make ATP (2)

Answer 26

* does not involved the electron transport chain/complex series of carriers and pumps * does not need stalked particles/ATP synthetase * does not need an electrochemical gradient * does not require oxygen * does not required mitochondria

Question 27

where in respiration where there is a conversion of an organic molecule from one form to another and substrate level phosphorylation occurs (2) and how many ATP made from each substrate level phosphorylation

Answer 27

* in conversion of triose phosphate to pyruvate -4 ATP * adter the 5C compound in the krebs cycle - 2 ATP

Question 28

where does the link reaction occurs in cells (1)

Answer 28

in the mitochondrial matrix

Question 29

name the two types of enzymes involved in the link reaction (1)

Answer 29

dehydrogenase and decarboxylase

Question 30

describe the role of the electron transport chain in the synthesis of ATP and explain the importance of ATP in living organisms (10)

Answer 30

* reduced NAD and reduced FAD provide * light/photon energy excited electrons in the reaction centre to provide * high energy electrons/transfer of electron energy * which fuels the proton pumps * proton pumps pump H+ into the inter membrane/thylakoid cavity * creating an electrochemical/chemiosmotic gradient/pH gradient/H+ gradient * use of electron carriers to move electrons to the next proton pump * the synthesis of ATP takes place by means of a flow of protons from inter membrane space to matrix/thylakoid cavity to stroma * down a concentration gradient through the enzyme ATP sythase/synthetase * use of oxygen a the final electron acceptor/formation of water in mitochondira * use of NADP as the final electron accpetor in chloroplast * energy is released when ATP is brokendown into ADP and phosphate/ terminal phosphate of ATP is hydrolysed * this is linked to energy requiring reactions/active transport/muscle contraction/synthesis of organic chemicals/drives the calvin cycle * called the universal energy currency * used by all living organisms for cellular processes

Question 31

describe the proceesses of glycolysis and the link reaction (10)

Answer 31

* glycolysis takes place in the cytoplasm and does not require oxygen * glucose is phosphorylate/use of ATP * the splitting of 6C/hexose phosphate formed into two 3C/triose phosphate molecules * removal of hydrogen/action of dehydrogenase enzymes * formation of reduced NAD ued in the ETC * substrate level phosphorylation * yield of 4 ATP per glucose/2 ATP per triose phosphate * net yield of 2 ATP for cellular processes * pyruvate passes into the link reaction * which takes place in the matric of the mitochondrion * the conversion of pyruvate to acetate * as a result of the removal of carbon/carbon dioxide/action of decarboxylase enzymes * and the removal of hydrogen by the reduction of NAD * the acetyl group then combines with co enzyme A * and enters the krebs cycle

Question 32

where do amino acids and product of hydrolysis of triglycerides enter the respiatory pathways (3)

Answer 32

* glycerol - phosphorylated 3C sugar -> pyruvate * fatty acids - acetyl coenzyme A -> beginning of krebs cycle * amino acid - pyruvate-> whole of krebs cycle

Question 33

describe the role of oxygen in aerobic respiration (2)

Answer 33

* final electron acceptor/ accepts electrons and protons * from final proton pump * in the electron transport chain

Question 34

Name one other metabolic produce of anaerobic respiration in muscle cells (1)

Answer 34

* lactate/lactic acid

Question 35

where in a cell does anaerobic respiration occur (1)

Answer 35

cytoplasm

Question 36

describe the importance of ATP to muscle cells (1)

Answer 36

provides energy for muscle contraction

Question 37

suggest what would happen to the RQ (respiratory quotent)/ volume of Co2 produced divded by volume of O2 consumed ) value if you were investigating anaerobic respiation in yeast and explain your answer

Answer 37

it would be higher/rise because there would be high CO2 levels and little/no O2 uptake

Question 38

describe how the electron transport chain leads to the synthesis of ATP (4)

Answer 38

* reduced NAD delivers high energy electrons to the first proton pump * pumps powered by electron energy pump H+ into inter membrane cavity/space * creating an electrochemical / chemiosmotic gradient * H+ flow down into the matrix through a stalked particle containing ATP synthetase

Question 39

cyanid binds to the third proton pump on the electron transport chain explain how this would affect ATP synthesis (2)

Answer 39

* would stop ATP synthesis * it woul dstop the final proton pump from combining with the electrons with oxygen and H+ to form water / electrons cannot move along ETC

Question 40

arsenic inhibits pyruvate dehydrogenase. explain the effect this would have on the sequence of events in the diagram (2)

Answer 40

* no hydrogen can be removed from pyruvate / prevents the oxidation of pyruvate * so there is no reduced NAD to suppy electrons to the ETC

Question 41

describe the sequence of events in the link reaction (4)

Answer 41

* carbon dioxide is removed by decarboxylation/using a decarboxylase enzyme * hydrogen is removed by dehydrogenation/ using a dehydrogenase enzyme * from pyruvate * forming 2C acetyl group * which combines with conenzyme A to form Acetyl Co enzyme A

Question 42

complete the table for the krebs cycle for produce and number produced per molecule of glucose (2) ATP -> CO2 -> -> 6 ->2

Answer 42

* ATP -> 2 * CO2->4 * reduced NAD ->6 * reduced FAD ->2

Question 43

glycolusis is regulated by slowing down or speeding up certain steps in the pathway by inhibiting or activating the enzymes that are involved a common mechanism by regulating enzymes is allosteric control which is a type of non competitive inhibition explain how the action of a non competitive inhibitor could inhibit glucose (4)

Answer 43

* binds to a eg dehydrogenase enzyme * away from active site * changes the shape of the active site * triose phosphate (glyceraldehyde-3-phosphate/substrate) no longer fits into the active site * so hydrogen not removed / produce not formed

Question 44

describe the stage of the biochemical pathway in the cytoplasm which produceds recuced NAD (2)

Answer 44

* from glycolusis * oxidation/dehydrogenation reaction/ action of dehydrogenase * conversion of triose phosphate to pyruvate

Question 45

The energy budget for the complete oxidation of a single glucose molecule is frequently quoted as 38 ATP. The majority of ATP produced in respiration is from the re-oxidation of the reduced NAD and reduced FAD, by the electron transport chain. Some of the reduced coenzymes must be transferred from the cytoplasm into the mitochondrial matrix. This is done via two mechanisms in insect flight muscles. A If levels of reduced NAD in the cytoplasm are high, the reduced NAD is transferred into the matrix through the outer and inner mitochondrial membranes. B If cytoplasmic levels of reduced NAD are low, then an alternative pathway is used whereby the reduced NAD passes its electrons to FAD in the inner mitochondrial membrane. (ii) Explain why the ATP yield per glucose molecule will be decreased if mechanism B is used. (2)

Answer 45

* reduced FAD (passes its electrons to the second proton pump/only uses two proton pumps) * only 2 ATP are produced per reduced FAD

Question 46

The energy budget for the complete oxidation of a single glucose molecule is frequently quoted as 38 ATP. The majority of ATP produced in respiration is from the re-oxidation of the reduced NAD and reduced FAD, by the electron transport chain. Some of the reduced coenzymes must be transferred from the cytoplasm into the mitochondrial matrix. This is done via two mechanisms in insect flight muscles. A If levels of reduced NAD in the cytoplasm are high, the reduced NAD is transferred into the matrix through the outer and inner mitochondrial membranes. B If cytoplasmic levels of reduced NAD are low, then an alternative pathway is used whereby the reduced Explain why mechanism A would be used in the muscle of flying insects. (2)

Answer 46

* more respiration/more ATP required for muscle contraction * the cells use the mechanism which yiels more ATP/3 ATP per reduced NAD

Question 47

if a human eats a diet low in nutrients, amino acids from muscle tissue can be used as a alternative respiratory substrate, the amino acids when processed produce nitrogenous waster describe the production of nitrogenous waste and state where this takes place (3)

Answer 47

* removal of amine/NH2 group / deamination/formation of keto acids/ammonia * combining of amino group with carbon dioxide/fomration of urea amine/NH2 group * in the liver