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BIOLOGY A LEVEL > CHAPTER 18 - RESPIRATION > Flashcards

CHAPTER 18 - RESPIRATION Flashcards

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1
Q

How many carbons does glucose contain

A

6 - Hexose sugar

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2
Q

How many stages are there in anaerobic respiration?

A

2 - Glycolysis then fermentation

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3
Q

How many stages are there in aerobic respiration

A

4 - Glycolysis, link reaction, Krebs cycle then electron transport chain (forming water)

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4
Q

Does Glycolysis require oxygen?

A

no it is an anaerobic process (but present in both aerobic and anaerobic pathways)

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5
Q

What are the products of Glycolysis

A

4 ATPs, 2 Reduced NADs and 2 Pyruvates

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6
Q

Describe the events that take place in Glycolysis

A

Phosphorylation -
2 phosphates from 2 ATP molecules attach to glucose molecule forming Hexose Bisphosphate

Lysis -
This destabilises the molecule causing it to split into two trios phosphate molecules

Phosphorylation 2 -
Another group is added to each triose phosphate to form 2 triode bisphosphate molecules, Phosphates are from free Pi in the cytoplasm

Dehydrogenation and formation of ATP -
The 2 triose bisphosphate molecules are then oxidised by removal of H atoms to form 2 pyruvate molecules - H atoms accepted by NAD forming reduced NAD and Phosphates form ATP (substrate-level phosphorylation)
(pg 481)

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7
Q

What is substrate-level phosphorylation

A

Formation of ATP without the involvement of an electron transport chain, from a short-lived highly reactive intermediate eg. creatine phosphate

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8
Q

Describe the processes of dehydration and phosphorylation in glycolysis

A

Dehydrogenation – removal of hydrogen from triose phosphate molecules to form pyruvate and reduction of NAD / formation of reduced NAD

phosphorylation – addition of phosphate group to a glucose molecule forming hexose bisphosphate

(both) catalysed by enzymes

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9
Q

Explain how NAD acts as a coenzyme in glycolysis

A

NAD accepts hydrogen (atom) and is reduced

during the formation of pyruvate

supplies hydrogen to enzyme involved in later stage of respiration

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10
Q

Explain the meaning of substrate-level phosphorylation

A

Addition of phosphate group

to ADP

or formation of ATP (using phosphate) from another molecule

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11
Q

Outline the importance of dehydrogenation and phosphorylation in glycolysis

A

Dehydrogenation –
hydrogen removed in breakdown of glucose

hydrogen required at a later stage

Phosphorylation –
addition of phosphate groups destabilises (large) molecules/glucose

leads to breakdown of glucose

synthesis of ATP

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12
Q

Where does the rest of aerobic respiration occur after glycolysis?

A

Mitochondria

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13
Q

What are the 5 parts of the mitochondria and what is their purpose

A

Outer Mitochondrial membrane - Separates the contents of the mitochondrion from the rest of the cell, creating a cellular compartment with ideal conditions for aerobic respiration

Inner Mitochondrial membrane - Contains electron transport chains and ATP synthase

Cristae - Projections of the inner membrane which increase Surface area available for Oxidative Phosphorylation

Matrix - Contains enzymes for the Krebs Cycle and Link Reaction, Also contains Mitochondrial DNA

Intermembrane space - Proteins are pumped into this space by the Electron Transport chain. The space is small so the concentration builds up quickly
(pg 482)

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14
Q

What is the Link reaction also called?

A

Oxidative Decarboxylation

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15
Q

Describe the events in The link reaction

A

Pyruvate (3-carbon) from Glycolysis loses a Carbon dioxide (diffuses away or gets removed from organism) - forming (2-Carbon) Acetyl group and a Hydrogen - which forms reduced NAD

Acetyl group binds to Coenzyme A to form Acetylcoenzyme A (acetyl CoA)

Coenzyme A delivers Acetyl group to next stage of respiration - Krebs cycle
(pg 482)

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16
Q

Explain why the removal of Carbon dioxide in the link reaction is called oxidative

A

Hydrogen is also removed

removal of hydrogen oxidises pyruvate

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17
Q

Name one organic compound and one inorganic compound produced in the link reaction

A

Acetyl group

carbon dioxide

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18
Q

Give the (simplified word) equation for the link reaction

A

Pyruvate + CoA + NAD —> Acetyl CoA + CO2 + NADH

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19
Q

Suggest why glycolysis occurs in the cytoplasm but not the mitochondrial matrix

A

Enzymes required are in cytoplasm

glucose molecule too large to move into mitochondrion

no transport proteins for pyruvate

mitochondria not originally present in (eukaryotic) cells

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20
Q

Describe the events in the Krebs Cycle

A

Acetyl CoA delivers Acetyl group to Krebs cycle. The two-carbon acetyl group combines with 4-carbon oxaloacetate to form 6 carbon citrate

The citrate molecule undergoes decarboxylation and dehydrogenation producing reduced NAD and CO2.
5 Carbon compound is formed.

The 5-carbon compound undergoes further decarboxylation and dehydrogenation reactions, producing in this order:
1: CO2, Reduced NAD
2: ATP
3: FADH2 (reduced FAD)
4: reduced NAD
5: Oxaloacetate (4 carbons)

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21
Q

What Is produced overall from the Krebs cycle

A

3 Reduced NADs
1 Reduced FAD
1 ATP
1 Oxaloacetate

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22
Q

What stages do NAD and FAD take part in

A

NAD - all stages of cellular respiration
FAD - Krebs cycle only

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23
Q

How many hydrogens does NAD and FAD accept?

A

NAD - 1 forming NADH
FAD - 2 forming FADH2

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24
Q

How many ATP molecules can FAD and NAD synthesise

A

NAD - 3
FAD - 2

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25
Q

Compare the structures of ATP and NAD

A

ATP –
three phosphate groups one ribose
one nitrogenous base

NAD –
two phosphate groups
two riboses
two nitrogenous bases

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26
Q

ATP can be described as a coenzyme. Explain why

A

It is used to link reactions

energy is released as a result of the activity of one enzyme and used by another enzyme

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27
Q

Calculate the number of ATP molecules produced by substrate-level phosphorylation after two rounds of the Krebs cycle

A

1 per turn
2 in total

28
Q

The Krebs cycle doesn’t use oxygen at any point. Suggest why the Krebs cycle is termed aerobic

A

Hydrogen needs to be removed for cycle to continue

hydrogen removed using NAD/FAD and reduced

then NAD/FAD are oxidised at electron transport chain

oxygen required for electron transport

29
Q

Suggest a reason for the involvement of FAD rather than NAD in only one specific step of the Krebs cycle

A

Enzymes are specific

active site complementary to substrate

different steps have different substrates

different steps require different enzymes

different enzymes (may) require different coenzymes

only one step in cycle has enzyme which requires FAD coenzyme

30
Q

Describe the events in oxidative phosphorylation

A

Hydrogen atoms that have been collected by the coenzymes NAD and FAD delivered to the electron transport chain present in the membranes of the Cristae of the mitochondria

Hydrogen atoms dissociate into hydrogen ions and electrons. The high energy electrons are used in the synthesis of ATP by chemiosmosis (proton gradient)

At the end of the transport chain, electrons combine with hydrogen ions and oxygen to form water. Oxygen is the final electron acceptor - cannot operate unless oxygen is present
(pg 486)

31
Q

What is oxidative phosphorylation

A

Coupling of the flow of protons down the electrochemical gadding through ATP synths to the phosphorylation of ADP to produce ATP

32
Q

Explain why hydrogen ions have to be actively pumped across the membrane from the matrix and return to the matrix by diffusion through ATP synthase

A

Actively pumped to increase concentration gradient

energy required as moving from low to high concentration

membrane impermeable to ions so ions diffuse down concentration gradient

ATP synthase provides hydrophilic channel

33
Q

Explain why the electrons released from reduced FAD, lead to the synthesis of less ATP than electrons released from reduced NAD

A

Reduced NAD releases electrons to carriers at the start of the ETC

reduced FAD releases electrons to carriers after the start of the ETC

with FAD electrons transported a shorter distance

so fewer protons are actively transported

34
Q

Cyanide is a respiratory poison. It attaches to the iron in the haem group of cytochrome C oxidase in complex IV of the electron transport chain. Suggest an explanation for the toxicity of cyanide.

A

Stops flow of electrons

stops active transport of protons

proton gradient not formed

(less) ATP synthesised; so less energy available for (vital) metabolic processes

35
Q

Explain, with reasons, whether you agree with the following statements:
1) ATP Synthase is not actually part of the electron transport chain
2) oxygen is required for the transfer of electrons along the electron transport chain
3) Hydrogen ions return to the matrix by facilitated diffusion

A

1) agree
not an electron carrier

2) agree
oxygen is final electron acceptor, required for electron transport

3) agree
diffuse through hydrophilic channels (of ATP synthase)

36
Q

How many molecules of ATP does Aerobic respiration produce per glucose molecule

A

38

37
Q

How many ATP molecules does Fermentation (form of anaerobic respiration) produce

A

(Net) 2

38
Q

What are obligate anaerobes

A

Cannot survive in the presence of oxygen. Almost all obligate anaerobes are prokaryotes eg. Clostridium (bacteria that causes food poisoning), but some are fungi as well

39
Q

What are facultative anaerobes

A

Synthesise ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen, eg. yeast

40
Q

What are obligate aerobes

A

Can only synthesise ATP in the presence of oxygen, eg. mammals.

The individual cells in some organisms, like muscle cells in mammals, can be described as facultative anaerobes because the supplement ATP supplies by employing anaerobic respiration in addition to aerobic respiration when O2 concentration is low; only for short periods and oxygen is eventually required. Anaerobic respiration produces compounds that have to be broken down when oxygen becomes available again, so the organism as a whole is an obligate aerobe

41
Q

What is fermentation

A

A form of anaerobic process in which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain.

The organic compounds, such as glucose, are not fully broken down so fermentation produces much less ATP than aerobic respiration. The small quantity of ATP produced is synthesised by substrate-level phosphorylation alone.

End products vary depending on organism

42
Q

Describe the events in lactate fermentation (in mammals)

A

Pyruvate acts as Hydrogen Acceptor taking hydrogen from Reduced NAD, catalysed by enzyme lactate dehydrogenase

Pyruvate is concerted to lactate (lactic acid) and NAD is regenerated

Can be used to keep Glycolysis going so a small quantity of ATP is synthesised

Reversible

43
Q

What happens to the lactic acid after fermentation

A

Converted back to glucose in the liver (oxygen required to complete this process)

44
Q

Why can’t lactate fermentation occur indefinitely

A

Reduced quantity of ATP produced wouldn’t be enough to maintain vital processes for along period of time

Accumulation of lactic acid causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filaments are made from proteins and will cease to function at low pH

45
Q

How is lactic acid removed from muscles and taken to the liver

A

Bloodstream

46
Q

Why is one of the main aims when improving physical fitness to increase blood supply and flow through muscles

A

To increase rate of lactic acid removal, allowing the intensity and duration of exercise to be increased

47
Q

Describe the events in Alcoholic fermentation (in yeast and many plant cells)

A

Pyruvate (3C) is converted into ethanal, catalysed by Pyruvate Decarboxylase, releasing CO2

Ethanal then accepts Hydrogen atom from Reduced NAD, becoming ethanol, regenerating NAD

NAD can then continue to act as coenzyme and glycolysis can continue

Non-reversible

48
Q

Describe an investigation into respiration rates in yeast

A

Place brewers yeast in a conical flask with a glucose solution

Seal flask ensure anaerobic conditions

Releases carbon dioxide as a byproduct

use gas syringe or stained water drop to see volume of carbon dioxide released

49
Q

Explain why the student investigated respiration rates in yeast by doing:
Carried out in Vacuum flask
Covered solution containing the yeast with liquid paraffin

A

Vacuum flask to control the temperature

paraffin prevents oxygen entering the solution

ensures respiration is anaerobic

50
Q

What mammalian adaptions are there for low oxygen environments

A

Biochemical adaptations - greater conc of Haemoglobin and myoglobin than land animals, helps maximise oxygen stores and delays onset of anaerobic metabolism
High tolerance to CO2 levels, effective buffering systems

Physiological -
Modified circulatory system, peripheral vasoconstriction so blood is shunted to the brain, heart and muscles, heart rate slows by 80%
Greater exchange of air in lungs (80-95% as opposed to 15% in humans)

Physical adaptions -
Streamlining to reduce drag, efficiency in propulsion

51
Q

The lungs of whales are proportionally no larger than humans, but some whales can stay underwater for 2 hours. Suggest how the lungs might be adapted to enable these long dices and why larger lungs would be a disadvantage to a whale

A

Flexible rib cage;

lungs can collapse under high pressure

air compressed

maintaining concentration gradients

exhalation before inhalation

increase proportion of air exchanged

Larger lungs would increase buoyancy

more energy would be used during dives

52
Q

Summarise the adaptations of whales for making long underwater dives

A

Streamlined

heart rate slowed

reduced energy requirements

blowhole on top of the head

large breath (when surface)

larger red blood cells

more haemoglobin

more blood

faster oxygen transport

more myoglobin

increased oxygen storage

53
Q

Explain why yeast cells are described as facultative anaerobes

A

Yeast cells normally respire aerobically

can respire anaerobically when required

54
Q

Describe why alcoholic fermentation can be described as having more in common with aerobic respiration than with fermentation

A

Electron transport chains present in some types of anaerobic respiration

aerobic respiration always includes presence of electron transport chains

no electron transport chains present in lactate fermentation

55
Q

Explain why the build-up of lactic acid eventually stops muscle contraction which we experience as fatigue

A

Increase in lactic acid leads to decrease in pH

muscle contraction depends on protein

e.g., enzymes, contractile proteins

decreasing pH denatures protein

protein no longer functional

56
Q

Glycolysis, the anaerobic stage of respiration, is the only source of ATP in red blood cells. Cardiac muscle is adapted to reduce the chances of anaerobic respiration ever being needed. Outline the benefits to red blood cells and cardiac muscle of different types of respiration they undertake

A

Red blood cells adapted to carry oxygen

lack of mitochondria means more space for haemoglobin

increased oxygen transport

lactic acid not produced in cardiac muscle

enzymes not denatured, no fatigue

blood flow to rest of organism not interrupted

57
Q

How are triglycerides converted to pyruvate ready to be respired?

A

Hydrolysed into fatty acids then enter Krebs cycle via Acetyl CoA and Glycerol,

58
Q

How many molecules of ATP can the fatty acids in a triglyceride synthesise?

A

500 (forming 50 Acetyl CoA molecules)

59
Q

How are proteins prepared to be respired

A

Hydrolysed into amino acids, then deaminated, before entering pathway, converting to ATP

These steps require ATP therefore reducing net production

60
Q

How is the Respiratory Quotient calculated

A

CO2 produced/O2 Consumed

Calculated for a substrate

61
Q

Biological molecules diagram of respiration

A

PAGE 493

62
Q

What instrument is used to measure respiratory quotient

A

Respirometer

63
Q

What are some key points about low carb diets to consider (maybe not needed but in textbook)

A

Read page 494

64
Q

Describe an experiment into the factors affecting the rate of respiration using respirometers

A

Pea seeds, glass beads and varying water content in separate containers with mesh and KOH solution in

Vary temperature and measure gas release using respirometer or gas syringe

65
Q

Outline there respiration pathway of a triglyceride

A

Triglyceride is broken down into fatty acids and glycerol

fatty acids undergo beta oxidation forming acetyl groups

acetyl groups are taken into Krebs cycle by coenzyme A

glycerol is converted to pyruvate, which undergoes oxidative phosphorylation

66
Q

Describe the difference between a respirometer and a spirometer

A

Both measure oxygen uptake/carbon dioxide release

so rate of respiration

respirometer is modified spirometer/(usually) used for smaller organisms

BIOLOGY A LEVEL (24 decks)

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