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A-Level Biology > Unit 5 - Energy Transfers in & b/w Organisms > Flashcards

Unit 5 - Energy Transfers in & b/w Organisms Flashcards

1
Q

describe the structure of mitochondria

A

outer membrane - freely permeable
inner membrane
intermembrane space
matrix
cristae
ATP synthase (stalked particle)

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2
Q

describe the inner membrane

A

folded into cristae - increases SA for insertion of membrane proteins ATPsynthase & ETC proteins
selectively permeable so most substances can only pass through carrier/channel proteins
stalked particle contains ATP synthase

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3
Q

describe the matrix

A

inner space
made of semi-rigid material containing enzymes, other proteins, lipids, 70s ribosomes & circular mitochondrial DNA

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4
Q

describe mitochondria characteristics in cells that are more metabolically active?

A

more mitochondria
larger mitochondria
more densely packed cristae

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5
Q

define cellular respiration

A

the conversion of organic molecules e.g. glucose (main respiratory substance) into ATP molecules

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6
Q

describe the 2 forms of cellular respiration

A

aerobic respiration - requires oxygen, produces CO2 + H2O + 38 ATP (lots more than anaerobic respiration)

anaerobic respiration (fermentation) - absence of O2, produces lactic acid/lactate in animals & ethanol + CO2 in plants & yeast
small amount of ATP produced (2 ATP molecules)

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7
Q

what are 2 key principles in respiration & PS?

A

redox reactions & co-enzymes

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8
Q

describe redox reactions

A

molecule is oxidised - lost e-s or H atoms
molecule is reduced - gained e-s or H atoms
OILRIG
H atom (1 proton + 1e-)

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9
Q

describe coenzymes

A

carriers of H atoms (H+ + e-)
molecules that are required by some enzymes to make them function

NAD involved throughout respiration
FAD involved in Krebs cycle
NADP involved in PS
coenzyme-A required to allow Krebs cycle to continue

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10
Q

define aerobic respiration

A

series of enzyme-catalysed reaction which use coenzymes & make ATP
in presence of O2

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11
Q

what are the 4 stages of aerobic respiration & give brief overview of each?

A
  1. glycolysis
    in cytoplasm
    oxidation of glucose to form 2 pyruvate molecules
    occurs in both aerobic & anaerobic respiration
  2. link reaction
    in matrix
    pyruvate (3C) –> acetyl coenzyme-A (2C) + CO2
    aerobic
  3. Krebs cycle
    in matrix
    acetyl coenzyme A goes into cycle of oxidation-reduction reactions
    ATP & e-s produced (e-s reduce NAD & FAD)
    aerobic
  4. oxidative phosphorylation (& ETC)
    occurs in cristae & intermembrane space
    e-s from reduced NAD & reduced FAD from Krebs cycle help to synthesise ATP
    H2O is produced as a by-product
    aerobic
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12
Q

describe the process of glycolysis

A

series of enzyme-catalysed reactions in cytoplasm
1. activation of glucose by phosphorylation
glucose is made more reactive by the addition of 2 phosphate molecules, from hydrolysis of 2 ATP, to form glucose phosphate

  1. phosphorylated glucose is split into 2 triose phosphate (3C) molecules
  2. oxidation of triose phosphate
    2 triose phosphates are oxidised by the removal of hydrogen from each
    the hydrogens are transferred to NAD to form reduced NAD (NADH)
  3. production of ATP & pyruvate
    enzyme-catalysed reactions convert each triose phosphate into pyruvate (3C)
    this makes 2 ATP per pyruvate
    this is substrate-level phosphorylation
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13
Q

NB for glycolysis

A

does not need O2
if no O2, anaerobic respiration takes place after

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14
Q

what are the net products of glycolysis?

A

2 ATP (4 total but 2 used to phosphorylate glucose at the start)
2 pyruvate
2 reduced NAD (NADH) for ETC later…

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15
Q

what happens b/w glycolysis & the link reaction?

A

the 2 molecules of pyruvate are actively transported into the mitochondria matrix through carrier molecules in inner membrane, needing ATP

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16
Q

describe the process of the link reaction

A

occurs in matrix of mitochondria
1. pyruvate is oxidised by removing hydrogen
2. hydrogens are transferred to NAD to form reduced NAD (NADH)
3. CO2 is removed from pyruvate to form a 2C molecule (acetate)
4. 2C molecule (acetate) combines with a molecule of coenzyme-A to form acetyl coenzyme-A

17
Q

what are the net products of the link reaction?

A

2 reduced NAD
2 CO2
2 acetyl CoA
no ATP

18
Q

NB for the link reaction

A

2 pyruvates produced in glycolysis from 1 glucose

19
Q

describe the process of the Krebs cycle

A

occurs in matrix of mitochondria
a series of enzyme-catalysed oxidation-reduction reactions

  1. 2C acetyl coenzyme-A from the link reaction reacts with 4C molecule to produce a 6C molecule. original CoA is recycled.
  2. this 6C molecule is decarboxylated & oxidised/dehydrogenated to produce a 4C molecule, 2xCO2 & 2xNADH
  3. a single ATP molecule is produced by substrate-level phosphorylation
  4. the 4C molecule transforms into original 4C molecule, which combines with new acetyl CoA to begin the cycle again

2 turns of cycle

20
Q

what are the net products of the Krebs cycle?

A

2 ATP
6 NADH
& 2 FADH2 both carrying H atoms to be used in ETC
4CO2

21
Q

how many turns of Krebs cycle per glucose molecule?

A

glucose forms 2 pyruvate in glycolysis
–> 2 acetyl CoA in the link reaction
–> 2 turns of Krebs cycle

22
Q

complete the table to show the differences b/w the Krebs cycle & Calvin cycle for site, e-/H carriers, CO2 & ATP

A

see booklet

23
Q

what happens b/w the Krebs cycle & oxidative phosphorylation?

A

the H atoms removed during glycolysis, the link reaction & the Krebs cycle are carried to the ETC by reduced NAD & reduced FAD

24
Q

define electron transport chain

A

the mechanism by which the energy of electrons within H atoms is converted into ATP

25
Q

describe oxidative phosphorylation

A

on cristae
1. the reduced NAD & reduced FAD are oxidised as they donate H atoms to carrier molecules attached to the inner mitochondrial membrane. so, the carrier molecules are reduced.

  1. the H atoms dissociate into protons & electrons
  2. the e-s are transferred along other carrier molecules in the ETC in a series of redox reactions
  3. as the e-s pass down the chain, they lose energy, which is used to power 3 proton pumps (in the carrier molecules)
  4. protons are pumped from the matrix into the intermembrane space where they accumulate
  5. the protons move back into the matrix bc fac. dif. through proton channels/ATPsynthase down the electrochemical gradient. this potential energy makes the ATPsynthase catalyse the condensation of ADP + Pi to form ATP
  6. at the end of the ETC, H+ & e- recombine to form H atoms
  7. O2 is the final electron acceptor in the ETC as the H atoms link with oxygen to form H2O
26
Q

describe chemiosmosis/chemiosmotic theory

A

the e-s are transferred along other carrier molecules in the ETC in a series of redox reactions

as the e-s pass down the chain, they lose energy, which is used to power 3 proton pumps (in the carrier molecules)

protons are pumped from the matrix into the intermembrane space where they accumulate

the protons diffuse back into the matric through proton channels down the electrochemical gradient. this potential energy makes the ATPsynthase catalyse the condensation of ADP + Pi to form ATP

27
Q

diagram of oxidative phosphorylation

A

see booklet

28
Q

why is oxygen needed for ATP production?

A

oxygen is the final electron acceptor
electrons cannot be passed along the ETC if there is no oxygen to accept them

if O2 is absent then protons & electrons would back up along the ETC & the process of aerobic respiration stops
decreased ATP produced
NADH & FADH2 cannot donate their H atoms to become oxidised so less NAD & FAD for the rest of respiration

29
Q

what are alternative respiratory substrates?

A

lipids & proteins

30
Q

describe the respiration of lipids

A

lipids are hydrolysed into fatty acids & glycerol (3C)

fatty acids are broken down into 2C fragments & converted into acetyl CoA –> enters Krebs cycle

glycerol is phosphorylated to convert it to triose phosphate which enters glycolysis pathway

31
Q

describe the respiration of proteins

A

proteins are hydrolysed into amino acids
amine group removed
enter respiratory pathway at different point depending upon # of C atoms - 4C/5C enter Krebs cycle, 3C converted into pyruvate & enter the link reaction

32
Q

what is the respiratory quotient?

A

the ratio of the volume of CO2 exhaled to that of oxygen consumed by an organism, tissue or cell in a given time

RQ = CO2 produced / O2 used

look at molar ratio in chemical equation

33
Q

how does cyanide affect the ETC?

A

respiratory poison
prevents the transfer of e-s from the final e- carrier in the ETC to O2

34
Q

why is the theoretical yield of ATP rarely achieved?

A
  1. protons leak across the mitochondrial membrane not through ATP synthase
  2. ATP produced is used for active transport of pyruvate into mitochondria (for link reaction)
35
Q

describe anaerobic respiration

A

occurs in the absence of O2 so no final e- acceptor in ETC
less ATP formed
ATP only formed by substrate-level phosphorylation
glycolysis then production of lactate or ethanol + CO2
No link reaction, Krebs cycle or ETC

36
Q

what happens in glycolysis in anaerobic respiration?

A

pyruvate is reduced to ethanol/lactate
hydrogen is removed from reduced NAD, oxidising it to NAD
pyruvate accepts hydrogen
NAD can be used in further glycolysis, producing ATP
net gain of 2 ATP molecules

37
Q

what is the equation for the anaerobic respiration/fermentation of plants & yeast?

A

pyruvate is decarboxylated/reduced
pyruvate + NADH –> ethanol + CO2 + NAD

38
Q

what are the uses of ethanol & CO2?

A

ethanol used in brewing w yeast
CO2 used in baking w yeast (makes bread rise)

39
Q

what is the equation for the anaerobic respiration/fermentation in animals?

A

pyruvate + NADH –> lactate + NAD
when oxygen is available lactate must be oxidised back to pyruvate

A-Level Biology (12 decks)

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