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biology > chapter 18 - Respiration > Flashcards

chapter 18 - Respiration Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

summarise the process of glycolysis

A

occurs in the cytoplasm of the cell
anaerobic process
glucose, 6 carbon sugar, is split into two smaller three-carbon pyruvate molecules. ATP and reduced NAD are also produced

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2
Q

what are the main steps in glycolysis

A

phosphorylation
lysis
phosphorylation
dehydrogenation and formation of ATP

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3
Q

what is a respiratory substrate

A

an organic substance that can be used/ broken down in respiration to release ATP

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4
Q

why do the organic molecules, e.g. lipids, carbs and protein, release different energy values

A

because H+ and e- combine with O2 to produce water, the more H atoms in a substrate, the more O2 needed, and more H2O is produced

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5
Q

describe lipids as respiratory substances

A
  • can only be respired anaerobically
  • gets hydrolysed into glycerol and fatty acids
  • glycerol gets converted into pyruvate
  • fatty acids consist of mainly hydrogen atoms
  • fatty acids get converted into acetyl groups (2c) through beta oxidation
  • acetyl groups combine with CoA and enter Krebs
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5
Q

describe proteins as respiratory substrates

A
  • can only be respired aerobically
  • only used during starvation, fasting or prolonged exercise
  • get hydrolysed into amino acids
  • some amino acids converted into pyruvate
  • some converted into acetate
  • others enter Krebs cycle directly
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6
Q

what are the typical Respiratory Quotients for
carbs
lipids
proteins

A

carbs - 1.0
lipids - 0.7
protein - 0.9

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7
Q

what is the Respiratory Quotient

A

the ratio of the volume of carbon dioxide given out in respiration to that of oxygen used

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8
Q

describe the process of anaerobic respiration

A

without oxygen: ETC stops (as oxygen is the final electron acceptor)
Krebs cycle stops
link reaction stops

glycolysis can continue if the NAD produced can be re-oxidised

anaerobic pathways provide somewhere for 2H to be donated and reduced NAD to become NAD and reused in glycolysis

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9
Q

what are the two anaerobic respiration pathway

A

ethanol fermentation - in some fungi and plant tissues

lactate fermentation - in animals

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10
Q

describe the ethanol pathway in anaerobic respiration

A

two step process
facultative anaerobe
- makes ATP by aerobic respiration
- can switch to alcoholic fermentation if necessary
dies when ethanol builds up to around 15%
slower than aerobic

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11
Q

describe the lactate pathway of anaerobic respiration

A

occurs in animals
one step process
lactate is toxic and removed by the liver
liver either converts lactate;
- back to pyruvate, can be converted to acetate to be used in Link/Krebs
- to glycogen and stored
liver needs oxygen to do this = oxygen debt

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12
Q

define respiration

A

the process whereby energy stored in complex organic molecules is used to make ATP

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13
Q

describe the ATP-ADP cycle

A

ATP is broken down into ADP + P
exergonic (energy released) (releases 30.5kJmol-1)

ADP + P forms ATP
endergonic (energy taken in) (requires 30.5kJmol-1)

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14
Q

how much energy is released in the hydrolysis of
ATP +H2O
ADP +H2O
AMP +H2O
why?

A

ATP = 30.6 kJmol-1
ADP = 30.6 kJmol-1
AMP = 14.2 kJmol-1
AMP is lower energy as phosphodiester bond is weaker (phosphate and ribose) compared to a phosphate and phosphate bond

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15
Q

what enzyme catalyses the hydrolysis of ATP

A

ATPase

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16
Q

what enzyme forms ATP

A

ATPsynthase

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17
Q

what is ATP used for (6)

A
  • metabolic processes - building large molecules
  • active transport - change shape of carrier proteins
  • movement - for muscle contraction
  • nerve transmission - Na+/K+ active transport pump require ATP
  • synthesis of materials within cells
  • secretion - packaging and transport of secretory products
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18
Q

what are the advantages of using ATP compared to glucose

A

only one enzyme needed to release energy from ATP (ATPase) (glucose needs more)
- ATP releases energy in smaller amounts and where needed (glycose contains large amounts we don’t need straight away)
- ATP is a common source of energy for multitude of chemical reactions, increasing the efficiency of the cells in the body (international energy currency)

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19
Q

where does oxidative phosphorylation occur?

A

in the inner membrane (cristae) of mitochondria

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20
Q

where do the link reaction and Krebs cycle occur

A

in the matrix of the mitochondria

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21
Q

what is the endosymbiotic theory

A

that some of the organelles in today’s eukaryotic cells were once microbes

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22
Q

what is the primary substrate for respiration

A

glucose (C6H12O6)

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23
Q

what is oxidation and reduction in respiration?

A

oxidation - loss of hydrogen (and electrons)
reduction - gain of hydrogen (and electrons)

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24
Q

how do Co-enzymes work

A

aid enzymes in the reduction or oxidation reactions because they can pick up and lose hydrogen atoms

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25
Q

what are the co-enzymes used in respiration

A

NAD
CoA - Coenzyme A
FAD

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26
Q

what are reduced coenzymes used for

A

in the final stage of respiration (oxidative phosphorylation) which produces a lot of ATP

27
Q

how do co-enzymes work - NAD example

A

substate - hydrogen lost - oxidised substrate
hydrogen atom accepted by coenzyme (NAD-> NADH)
coenzyme is oxidised (NADH-> NAD)
hydrogen is removed and used to generate ATP

28
Q

when is NAD reduced?

A

in the first 3 stages of respiration

29
Q

when is FAD reduced

A

in the Krebs cycle

30
Q

what are the four main stages of aerobic respiration

A

glycolysis
link reaction
Krebs cycle
Oxidative Phosphorylation

31
Q

describe the process of glycolysis

A

glucose broken down into 2 pyruvate molecules
- occurs in the cytoplasm and does not require oxygen
(first step in both aerobic and anaerobic)
glycolysis results in 2 pyruvate molecules, 2 NADH and 2 ATP molecules

32
Q

describe the process of glycolysis

A
  • ATP is hydrolysed
  • energy released is used to attach Pi to the glucose at carbon 6 - phosphorylation
  • destabilises glucose and prevents it from leaving the cell as it is an ion
  • repeated after isomerisation
  • hexose 1,6 biphosphate splits into 2x triose phosphate (3C)
  • 2 hydrogens are removed from TP by dehydrogenase enzyme
    -NAD accepts hydrogen becoming NADH
    (process repeated for each triose phosphate)
    final step = formation of ATP via substrate level phosphorylation
  • intermediate compounds provide Pi at this stage,
    in addition to ATP pyruvate (3C) is formed
    all of the above happens twice
33
Q

what is the net production of ATP after glycolysis

A

2

34
Q

what are the key points of glycolysis

A

occurs in cytoplasm
no oxygen required
enzymes are used in each step
4 ATP molecules made
net ATP production = 2
2 NADH produced
2 pyruvate (3C) made

35
Q

what are the key points of the Link reaction

A

occurs in matrix of mitochondria
pyruvate and NADH from glycolysis is actively transported into mitochondria
link reaction involves conversion of pyruvate to acetyl CoA

36
Q

why is everything in the link and Krebs cycle doubled?

A

as there are 2 pyruvate molecules

37
Q

what enzyme removes 2 hydrogen atoms from pyruvate in the link reaction

A

pyruvate dehydrogenase

38
Q

describe the process of the link reaction

A
  • pyruvate dehydrogenase removes 2 hydrogens from pyruvate
  • NAD accepts hydrogens to become NADH
  • pyruvate decarboxylase removes carboxyl group and CO2 is formed

after removal of 2H and carboxyl groups, pyruvate (3C) has been converted into acetate (2C)
- CoA accepts acetate to become acetyl CoA
- Acetyl CoA moves into the Krebs cycle

39
Q

what are the products of the link reaction

A
  • 2NADH
  • 2CO2
  • 2 Acetyl CoA
    (no ATP produced)
40
Q

what are the products at the stages 1-6 of the Krebs cycle
and what are the reactions that happen to these products

A
  1. acetate 2C - joins with oxaloacetate (4C)
  2. Citrate 6C - oxidised and decarboxylated
  3. 5C compound - oxidised and decarboxylated
  4. 4C compound - converted into another 4C and ATP is produced
  5. 2nd 4C - dehydrogenated into 3rd 4C
  6. 3rd 4C dehydrogenated into oxaloacetate (4C)

all happens twice!

41
Q

what are the products of the Krebs Cycle

A
  • 4 CO2
  • 6 NADH
  • 2 FADH
  • 2 ATP

net ATP production in Krebs = 2
net ATP production so far = 4

42
Q

what is stage 1 of the Krebs cycle

A

Acetate (2C) leaves CoA and joins with oxaloacetate (4C) forming citrate (6C)

43
Q

stage 2 of the Krebs Cycle

A
  • citrate (6C) is oxidised/ dehydrogenated and decarboxylated to form 5C compound
  • Enzymes involved - dehydrogenase and decarboxylase
  • NAD accepts the hydrogen becoming NADH and CO2 is released
44
Q

stage 3 of the Krebs Cycle

A
  • 5C compound is oxidised/ dehydrogenated and decarboxylated to form 4C compound
  • NAD accepts hydrogen becoming NADH and CO2 is released
45
Q

stage 4 of the Krebs Cycle

A

4C compound is then converted into another 4C compound and ATP is produced through substrate level phosphorylation

46
Q

stage 5 of the Krebs Cycle

A

2nd 4C compound is then converted into a 3rd 4C compound through dehydrogenation and FAD accepts the 2H atoms becoming FADH

47
Q

stage 6 of the Krebs Cycle

A

3rd 4C is then converted into oxaloacetate (4C) through dehydrogenation and NAD accepts the 2H atoms becoming NADH

47
Q

in oxidative phosphorylation, what are protein carriers referred to as

A

complexes I-IV

48
Q

stages 1-3 of oxidative phosphorylation

A
  1. NADH is oxidised and donates 2H
  2. the 2H are split (by enzyme) into 2 electrons and 2 protons
  3. complex I receives electrons which are passed along the electron transport chain (ETC)
    protein carriers contain iron ions (Fe3+)
    Fe3+ become Fe2+ until electron is passed to next protein
49
Q

stage 4 of oxidative phosphorylation

A

the 2 protons are pumped from the matrix across the inner membrane into the intermembrane space
the energy released from the ETC provides the energy used for active transport

50
Q

stage 5 of oxidative phosphorylation

A

FADH is also oxidised and the 2H are split into 2e- and 2p+
the 2 electrons are received by complex II and passed along ETC
2 protons are pumped into intermembrane space

51
Q

stage 6 of oxidative phosphorylation

A

hydrogen ions/ protons accumulate in the intermembrane space and are at a higher concentration than in the matrix
- electrochemical gradient - protons move back into the matrix via chemiosmosis (proton motive force)

52
Q

stages 7 and 8 of oxidative phosphorylation

A
  1. the protons travel through a protein channel in ATP synthase
  2. the movement of protons through the channel changes the shape of ATP synthase allowing it to create ATP from ADP and Pi
53
Q

stage 9 of oxidative phosphorylation

A

the protons have re-entered the matrix join with the electrons released at the end of the ETC at complex IV forming hydrogen
hydrogen reacts with O2 to form water (4H+ +4E- + O2 = 2H2O)

oxygen is the driving force - without it then the electrochemical gradient wouldn’t be as steep as protons accumulate in the matrix

54
Q

how much ATP is produced in oxidative phosphorylation

A

10 NADH used so 25 ATP produced
2 FADH used so 3 ATP produced
28 in total

55
Q

how many ATP are made from one molecule of:
NAD
FAD

A

1 NAD = 2.5 ATP
1 FAD = 1.5 ATP

56
Q

how much ATP would we expect to be produced in aerobic respiration
(incl. different stages)

A

glycolysis = 2 net
link = 0
Krebs = 2
oxidative phosphorylation = 28

total = 32 ATP produced

57
Q

why might less ATP be produced than we expect?

A
  • some protons leak across the membrane in the mitochondria - reducing electrochemical gradient
  • some ATP used in transporting pyruvate and reduced NAD from glycolysis into mitochondria
58
Q

what process converts fatty acids in lipids into acetyl groups (2C)

A

beta oxidation

59
Q
A
60
Q

What is the:
type of respiration,
Location of enzyme
And inhibitor
Of citrate synthase

A

Aerobic
Mitochondria
Citric acid

61
Q

What are the net products of the Krebs cycle for ONE pyruvate molecule

A

3NADH
1 FADH
2CO2
1ATP

62
Q

What is a similarity in the way ATP is made in respiration and photosynthesis

A

Both involve proton gradients

63
Q

Explain the relative yield of ATP in aerobic and anaerobic respiration

A

Anaerobic produces less ATP per glucose molecule because NAD is not regenerated in oxidative phosphorylation

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