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A-Level Biology > Chapter 18 - Respiration > Flashcards

Chapter 18 - Respiration Flashcards

1
Q

Respiration

A

Carbon framework of glucose is broken down and the carbon-hydrogen bonds are broken ; the energy released is then used in the synthesis of ATP by Chemiosmosis ; ATP is constantly synthesised and used in energy-requiring reactions and processes

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2
Q

Prokaryotic cells respiration

A

They do not have mitochondria ; so many of the reactions take place on cell membranes - process is continuous in cells but broken down into stages

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3
Q

Glycolysis

A

Occurs in the cytoplasm of the cell ; does not require oxygen and is an anaerobic process… glucose, a six carbon sugar, is split into two smaller 3 carbon pyruvate molecules ; ATP and reduced NAD are also produced

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4
Q

First step of glycolysis

A

Phosphorylation - first step of glycolysis requires two molecules of ATP ; 2 phosphates, released from the two ATP molecules, are attached to a glucose molecule forming hexose bisphosphate

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5
Q

Second step of glycolysis

A

Lysis - destabilises this unstable molecule and causes it to split into two Triose phosphate molecules

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6
Q

Third step of glycolysis

A

Phosphorylation - another phosphate is added to each Triose phosphate forming two Triose bisphosphate molecules ; these phosphate groups come from free inorganic phosphate ions present in the cytoplasm

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7
Q

4th step of glycolysis

A

Dehydrogenation and formation of ATP ; the two Triose bisphosphate molecules are then oxidised by the removal of hydrogen atoms (dehydrogenation) and they form two pyruvate molecules ; NAD coenzymes accept the hydrogen atoms and are reduced forming two reduced NAD molecules
From the removal of the two phosphates from each Triose bisphosphate - 4 ATP molecules are formed

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8
Q

What form of phosphorylation is glycolysis?

A

Substrate level - formation of ATP without the involvement of an electron transport chain ; ATP is formed by the transfer of a phosphate group from a phosphorylated intermediate to ADP

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9
Q

Overall net yield of Glycolysis

A

Two ATP molecules are used to prime the process
4 ATP molecules are produced so overall net yield = 2 ATP molecules

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10
Q

Where does glycolysis take place?

A

Cytoplasm of the cell

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11
Q

Where do the remaining aerobic reactions take place?

A

Mitochondria

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12
Q

Where is the electron transport chain/ATP synthase?

A

Inner mitochondrial membrane

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13
Q

Where does oxidative phosphorylation take place?

A

In the cristae - projections of the inner membrane with a high SA

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14
Q

Where are proteins pumped into by electron transport chain?

A

Intermembrane space - very small, concentration builds up quickly

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15
Q

Where are the enzymes for the Krebs cycle and link reaction?

A

In the matrix - also contains mitochondrial DNA

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16
Q

Purpose of outer mitochondrial membrane?

A

Separates the contents of the mitochondrion from the rest of the cell ; creating a cellular compartment with ideal conditions for aerobic respiration

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17
Q

Purpose of link reaction?

A

To link anaerobic glycolysis (cytoplasm) with the aerobic steps of respiration, occurring in the mitochondria
First step is oxidative decarboxylation

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18
Q

Link reaction

A

Pyruvate enters matrix by active transport via carrier proteins ; pyruvate then undergoes oxidative decarboxylation where carbon dioxide is removed along with hydrogen (oxidation) ; hydrogen atoms removed are accepted by NAD which is reduced to form NADH
THE RESULTING 2 CARBON ACETYL GROUP IS BOUND BY COENZYME A FORMING ACETYLCOENZYME A (acetyl CoA)

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19
Q

Purpose of products of link reaction

A

ACETYL CoA delivers the ACETYL group to the next stage of aerobic respiration known as the Krebs Cycle ; reduced NAD is used in oxidative phosphorylation to synthesise ATP

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20
Q

Carbon dioxide produced

A

Either diffuse away and be removed as metabolic waste or in autotrophic organisms it may be used as a raw material in photosynthesis

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21
Q

What to remember about link reaction?

A

HAPPENS TWICE - once for each Pyruvate molecule

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22
Q

Krebs cycle

A

Takes place in the mitochondrial matrix - each complete cycle results in the breakdown of an ACETYL group

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23
Q

Purpose of coenzymes produced during Krebs?

A

Reduced NAD and reduced FAD produced are used in the final, oxygen-requiring step of aerobic respiration to produce large quantities of ATP by Chemiosmosis

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24
Q

Krebs 1

A

ACETYL CoA delivers an acetyl group to the Krebs cycle ; the acetyl group combined with 4 carbon oxaloacetate to form 6-Carbon citrate

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25
Q

Krebs 2

A

Citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD and carbon dioxide - a 5 carbon molecule is formed

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26
Q

Krebs 3

A

5 carbon compound undergoes further decarboxylation and dehydrogenation eventually regenerating OAA

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27
Q

NAD and FAD

A

Coenzymes that accept protons and electrons released during breakdown of glucose

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28
Q

Difference between NAD and FAD

A

Take part in all stages of cellular respiration but FAD only accepts hydrogens in the Krebs Cycle

29
Q

How many hydrogens do coenzymes accept?

A

NAD accepts 1 hydrogen and FAD accepts two hydrogens

30
Q

When are the coenzymes oxidised?

A

Reduced NAD is oxidised at the start of the electron transport chain, while reduced FAD is oxidised further along the chain

31
Q

Synthesis of ATP molecules via coenzymes

A

Reduced NAD results in the synthesis of 3 ATP molecules
Reduced FAD results in the synthesis of only 2 ATP molecules

32
Q

NAD more accurate form?

A

NAD+ - it’s charged

33
Q

Where do coenzymes come from?

A

Derived from vitamins - that’s why they’re an essential micronutrient

34
Q

What happens with the coenzymes after?

A

Hydrogen atoms are delivered to electron transport chains present in the membranes of the cristae

35
Q

How is ATP synthesised?

A

Hydrogen atoms dissociate into hydrogen ions and electrons ; high energy electrons are used in the synthesis of ATP by Chemiosmosis
Energy is released during redox reactions as the electrons reduce and oxidise electrons carriers as they flow along the electron transport chain ; energy is used to create a proton gradient leading to the diffusion of protons through ATP synthase -> ATP synthesised

36
Q

End of electron transport chain?

A

Combine with hydrogen ions and oxygen to form water ; oxygen is the final electron acceptor and the chain cannot operate unless oxygen is present

37
Q

How many complexes in the electron transport chain?

A

4

38
Q

Formation of ATP

A

Phosphorylation of ADP dependent on electrons moving along electron transport chain - requires the presence of oxygen and is known as oxidative phosphorylation

39
Q

Why do hydrogens released from NAD and FAD not combine directly with oxygen?

A

Energy released from the formation of bonds during the production of water could not be used to synthesise ATP ; heat released in the Exothermic reaction would simply raise the temperature of the cell

40
Q

Substrate level phosphorylation

A

Production of ATP involving the transfer of a phosphate group from a short-lived, highly reactive intermediate such as creating phosphate ; different from oxidative phosphorylation which couples flow of protons down electrochemical gradient through ATP synthase to phosphorylation of ADP to produce ATP

41
Q

Molecules of ATP/glucose molecule

A

Aerobic = 38 molecules of ATP/glucose
Anaerobic = 2 molecules of ATP/glucose

42
Q

Evolution of respiration

A

Aerobic respiration was not possible when life began as there was no oxygen - new process in the evolutionary system but far more efficient than anaerobic respiration

43
Q

Obligate anaerobes

A

Cannot survive in the presence of oxygen ; almost all obligate anaerobes are prokaryotes ; for example certain strains of bacteria and fungi

44
Q

Facultative anaerobes

A

Synthesise ATP by aerobic respiration if oxygen is present ; but can switch to anaerobic respiration in the absence of oxygen - YEAST

45
Q

Obligate aerobes

A

Can only synthesise ATP in the presence of oxygen (mammals) ; individual cells of some organisms, such as muscle cells in mammals, can be described as facultative anaerobes because they can supplement ATP supplies by employing anaerobic respiration in addition to aerobic respiration when oxygen concentration is low - BUT ONLY FOR SHORT PERIODS OF TIME AND OXYGEN EVENTUALLY REQUIRED TO BREAK DOWN LACTIC ACID
Organism as a whole is an obligate aerobe

46
Q

Fermentation

A

Form of anaerobic respiration by which complex organic compounds are broken down into simpler inorganic ones without the use of oxygen or involvement of an electron transport chain

47
Q

Why does fermentation produce less ATP?

A

Glucose is not fully broken down ; small quantity of ATP produced is synthesised by substrate-level phosphorylation alone

48
Q

Alcoholic fermentation

A

Occurs in yeast and some plant root cells

49
Q

End products of alcoholic fermentation

A

Ethanol and carbon dioxide

50
Q

Lactate fermentation

A

Produces lactate (lactic acid) in animal cells

51
Q

What happens when oxygen is unable to act as the final electron acceptor?

A

Whole process backs up - first Chemiosmosis stops and as flow of electrons has stopped, reduced NAD and FAD are no longer able to be oxidised because there is nowhere for the electrons to go ; so coenzymes cannot be regenerated and so decarboxylation and oxidation of pyruvate and Krebs cycle comes to a halt as there are no coenzymes available to accept the hydrogens being removed

52
Q

Lactate fermentation

A

Pyruvate acts as a hydrogen acceptor and takes the hydrogen from reduced NAD catalysed by the enzyme lactate dehydrogenase ; pyruvate is converted to lactate and NAD is regenerated

53
Q

Purpose of regeneration of NAD?

A

Used to keep glycolysis going so a small quantity of ATP still synthesised ; anaerobic respiration in muscles is often supported by ATP from aerobic respiration from other parts of the body

54
Q

Oxygen debt

A

Lactic acid converted back to glucose in the liver using oxygen

55
Q

Why can lactate fermentation not occur indefinitely?

A

Reduced quantity of ATP would not be enough to maintain vital processes for a long period of time
Accumulation of lactic acid causes a fall in pH - proteins denature - respiratory enzymes/muscle filaments will cease to function at low pH

56
Q

Main aims of fitness

A

Increase blood flow through muscles which increases the rate at which lactic acid is removed - allowing the intensity of exercise to be increased

57
Q

Alcoholic fermentation

A

IRREVERSIBLE PROCESS UNLIKE LACTATE FORMATION
1) Pyruvate to ethanal via decarboxylation
2) Ethanal to ethanol ; accepts a hydrogen atom from reduced NAD
NAD can continue to act as a coenzyme and glycolysis continues

58
Q

Alcohol fermentation

A

Not a short term process and can continue indefinitely in the absence of oxygen - ethanol is a toxic waste product to yeast cells and they are unable to survive if ethanol accumulates above approximately 15% ; allowed to happen during the production of alcohol in brewing or wine making

59
Q

Is lactic acid a waste product?

A

No - it is recycled as glucose

60
Q

Respiratory substrates

A

Organic molecules that are broken down to release energy for the synthesis of ATP - triglycerides are hydrolysed to fatty acids which enter the Krebs cycle

61
Q

Fatty acids

A

Can lead to the formation of as many as 50 acetyl CoA molecules resulting in the synthesis of up to 500 ATP molecules; lipids store and release twice as much energy as carbohydrates
Protein roughly same as carbohydrates

62
Q

Why does protein produce less ATP?

A

They have to first be hydrolysed to amino acids and they then have to be delaminated before they enter the respiratory pathway - usually via pyruvate ; these steps require ATP, reducing the net production of ATP

63
Q

RQ

A

CO2 produced/O2 consumed

64
Q

How is RQ measured?

A

Using a respirometer

65
Q

Why do lipids have a lower RQ value than carbohydrates?

A

Lipids contain a greater proportion of carbon-hydrogen bonds than carbohydrates which is why they produce so much more ATP in respiration ; lipids require relatively more oxygen to break them down and release relatively less CO2

66
Q

During normal activity?

A

RQ in the range of 0.8-0.9 ; carbohydrates and lipids are being used as respiratory substrates

67
Q

During anaerobic respiration?

A

RQ>1 ; this is not easy to measure as the point at which anaerobic respiration begins is not easy to pinpoint

68
Q

Purpose of potassium hydroxide?

A

Absorbs CO2

69
Q

What does a respirometer measure?

A

Change in volume of oxygen or carbon dioxide

A-Level Biology (37 decks)

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