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Biology Unit 3 > 3.3 -Respiration > Flashcards

3.3 -Respiration Flashcards

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1
Q

Define aerobic respiration

A

The release of large amounts of energy made available as ATP, from the breakdown of molecules, with oxygen as the terminal electron acceptor

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2
Q

Define Anaerobic respiration

A

The breakdown of molecules in the absence of oxygen, releasing relatively little energy, making a small amount of ATP by substrate level phosphorylation

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3
Q

Define metabolism

A

All of the reactions of an organism

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4
Q

Define the term metabolic pathway

A

A sequence of reactions controlled by enzymes.

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5
Q

What term is used to describe reactions of respiration?

Define this.

A

Catabolic
This means Larger molecules are separated to form smaller molecules.
E.g they break down energy-rich macromolecules (e.g glucose and fatty acids) into smaller molecules.

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6
Q

How is energy made available for phosphorylation in respiration?

A

C-C, C-H, C-OH bonds are broken and lower energy bonds formed.
The energy difference allows the phosphorylation of ADP to ATP.

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7
Q

When does ATP release energy?

A

When it is hydrolysed (the chemical breakdown of a compound due to reaction with water)

ATP+H2O⇋ADP+Pi + energy

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8
Q

Where does the energy released by ATP go?

A

The energy is available for use by the cell or is lost as heat

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9
Q

What are the 3 types of phosphorylation?

A
  1. Oxidative Phosphorylation
  2. Photo phosphorylation
  3. Substrate level phosphorylation
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10
Q

Briefly describe oxidative phosphorylation

A
  • Occurs in the inner membranes of the mitochondria in aerobic respiration
  • The energy for making the ATP comes from oxidation-reduction reactions and is released in the transfer of electrons along the electron transfer chain
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11
Q

Briefly describe photo phosphorylation

A
  • Occurs in the thylakoid membranes of the chloroplast in the light dependent stage of photosynthesis
  • The energy for making ATP comes from light and is released in the transfer of electrons along a chain of electron carrier molecules
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12
Q

Briefly describe substrate level phosphorylation

A
  • Occurs when phosphate groups are transferred from donor molecules to ADP to make ATP in glycolysis
  • Also occurs when enough energy is released for a reaction to bind ADP to inorganic phosphate (e.g in Krebs cycle)
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13
Q

What form of respiration do most living organisms use?

What is the name for these organisms?

A

Aerobic respiration

  • the break down of substrates using oxygen with the release of a large amount of energy
  • these are obligate aerobes
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14
Q

Give some examples of facultative anaerobes

Define the term facultative anaerobe

A

Facultative anaerobes can respire both aerobically and anaerobically.
Examples include: some micro-organisms e.g yeast and many bacteria

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15
Q

Give examples of those who use anaerobic respiration.

What is the name for such organisms?

A
  • Some bacteria and Archaea
  • respire without oxygen and can’t grow in its presence
  • obligate anaerobes
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16
Q

What are the four distinct but linked stages of aerobic respiration?

A

1) Glycolysis
2) The Link Reaction
3) The Krebs Cycle
4) The Electron Transport Chain

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17
Q

Briefly describe Glycolysis

A
  • occurs in solution in the cytoplasm

- generates pyruvate, ATP and reduced NAD

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18
Q

Briefly describe the link reaction

A

Occurs in solution in the matrix of the mitochondrion. Pyruvate is converted into Acetyl Coenzyme A.

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19
Q

Briefly describe the Krebs cycle

A

Occurs in solution in the matrix of the mitochondrion, generates CO2, reduced NAD and reduced FAD

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20
Q

Briefly describe the electron transport chain

A

Occurs on the cristae of the inner mitochondrial membrane, in which energy from protons and electrons generates ATP from ADP and inorganic phosphate Pi.

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21
Q

Why should you use the ending ‘ate’ for an acid e.g pyruvate over pyruvic acid?

A

An acid solution (pyruvic acid) makes an ion (pyruvate). Acids in the cell are dissolved, so the names of their ions ending in ‘ate’ are used.

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22
Q

What is the initial stage of both aerobic and anaerobic respiration?

A

Glycolysis

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23
Q

Where does glycolysis occur? Why?

A

Glycolysis occurs in solution in the cytoplasms because glucose can’t pass through the mitochondrial membrane.

-even if it was small, the enzymes required for its breakdown are not present in the mitochondria :: can’t be metabolised there

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24
Q

Define the term dehydrogenation

A

The removal of one or more hydrogen atoms from a molecule.

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25
Q

Describe the first stage of glycolysis.

A

1) A glucose molecule is phosphorylated by the addition of 2 phosphate groups, using two molecules of ATP, making a hexose phosphate called glucose di-phosphate.

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26
Q

What is the benefit of phosphorylation of glucose in stage 1 of glycolysis

A
  • glucose diphosphate is more reactive so less activation energy is required for the enzyme controlled reactions
  • glucose diphosphate is polar and :: less likely to diffuse out of the cell
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27
Q

Describe stage 2 of glycolysis

A

The glucose diphosphate splits into two molecules of triose phosphate.

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28
Q

Describe stage 3 of glycolysis

A

A) The two triose phosphate molecules are dehydrogenated (hydrogen is removed) oxidising them to pyruvate.

B) The hydrogen atoms are transferred to NAD (hydrogen carrier molecule) making reduced NAD.

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29
Q

What is the energy released from the dehydrogenation of triose phosphate and hydration of NAD used for?

A

It’s used to synthesise four ATP molecules via substrate level phosphorylation (the phosphate from the triose phosphate converts ADP to ATP producing pyruvate

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30
Q

What is the net gain of ATP from glycolysis?

A

2ATP, because 2 ATP were used to phosphorylate the glucose molecules, and 4 were produced via substrate level phosphorylation
2 reduced NAD were also produced, each having the potential to synthesise 3 ATP if carrier molecule oxygen is available, making a total of 6 ATP produced so far via electron transport chain

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31
Q

In what forms is energy lost/transferred in glycolysis?

A
  • Some energy is lost as heat
  • considerable chemical potential energy remains in pyruvate
  • it 02 is available some of this energy can be released via the Krebs cycle in mitochondria
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32
Q

Define the term decarboxylation

A

The removal of a carboxyl group from a molecule, releasing carbon dioxide

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33
Q

When does the link reaction occur?

A

It links glycolysis to the Krebs cycle

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34
Q

Describe the link reaction

A

1) pyruvate diffuses from the cytoplasm into the mitochondrial matrix
2) the pyruvate is dehydrogenated and the hydrogen released is accepted by NAD to form reduced NAD
3) the pyruvate is also decarboxylated leaving a 2 carbon acetate group which combines with coenzyme A (CoA) making acetyl coenzyme A (AcCoA) which enters the Krebs cycle (after combining with 4c compound from Krebs cycle to form citric acid)

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35
Q

Give the summary equation of the link reaction:

A

Pyruvate + NAD + CoA —> AcCoA + reduced NAD + CO2

36
Q

Check diagram on pg 45 if unsure of glycolysis/ link reaction/ Krebs cycle

A

Check diagram on pg 45 if unsure of glycolysis/ link reaction/ Krebs cycle

37
Q

How many times does the Krebs cycle turn per glucose molecule? Why?

A

It turns twice per glucose molecule because 2 pyruvate ions are produced during glycolysis

38
Q

Describe the purpose of the Krebs cycle in one sentence

A

The means of liberating energy from C-C, C-H and C-OH bonds, producing ATP containing the energy that was held in the chemical bonds of the original glucose molecule.

39
Q

What does the Krebs cycle produce?

A

1) one ATP by substrate level phosphorylation
2) 3 molecules of Reduced NAD and one molecule of reduced FAD (deliver h2 to the electron transport chain on the inner mitochondrial membrane)
3) 2 molecules of CO2 as a waste product

40
Q

Describe the first step in the Krebs cycle

A

1) Acetyl Coenzyme A enters the Krebs cycle by combining with a 4c acid to form a 6 carbon compound (citric acid) and the CoA is regenerated

41
Q

Describe steps 2,3 & 4 of the Krebs cycle

A

2) the 6 carbon acid is dehydrogenated, making reduced NAD, and decarboxylated to make carbon dioxide and a 5 carbon acid
3) the 5 carbon acid is dehydrogenated, making reduced NAD and reduced FAD, and decarboxylated to make carbon dioxide and regenerates the 4c acid
4) the 4 carbon acid combines with more AcCoA and cycle repeats

42
Q

How many times does decarboxylation occur in the Krebs cycle?

A

Occurs twice, removing carbon dioxide from -COOH groups of Krebs cycle intermediates
6C acid —> 5c acid —> 4c acid

43
Q

What happens to the acetate group from the original glucose molecule in the Krebs cycle?
What happens to the energy?

A

The acetate group is now entirely broken down to carbon dioxide and water.
The energy in the bonds of the glucose molecule is carried by electrons in the hydrogen atoms in the reduced NAD/FAD

44
Q

Define the term coenzyme

A

A molecule required by an enzyme in order to function

45
Q

Where is the electron transport chain located?

A

On the cristae Of the inner mitochondrial membranes

46
Q

What is the electron transport chain?

A

A series of protein molecules that are carriers and pumps (sometimes called respiratory enzymes) which catalyse reactions to release energy, which is carried by ATP.

47
Q

Why is the electron transport chain sometimes called the cytochrome chain?

A

Because the carrier molecules include cytochromes (proteins conjugated to iron or copper and the metal ions are oxidised and reduced by electron transport)

48
Q

How do H+ ions enter the ETC

A

Hydrogen atoms are carried into the electron transport chain by the coenzymes NAD and FAD.

49
Q

Important fact to note about NAD and FAD

A

NAD feeds electrons and protons into the electron transport chain at an earlier stage than FAD does

50
Q

How many molecules of ATP can each pair of hydrogen atoms carried by reduced NAD from? What about FAD? Why is this?

A
  • each pair of hydrogen atoms carried by reduced NAD provides enough energy to synthesise 3 molecules of ATP, using 3 proton pumps
  • Reduced FAD passes hydrogen atoms directly to the second proton pump, so the carrier system involved produced 2 molecules of ATP for each pair of hydrogen atoms.
51
Q

Describe the passage of electrons in the electron transport chain

A

1) reduced NAD donated the electrons of the hydrogen atoms to the first of a series of electron carrier in the ETC
2) The electrons from these atoms provide energy for the first proton pump and protons from the hydrogen atoms are pumped into the inter-membrane space
3) the electrons pass along the chain of carrier molecules providing energy for each of three proton pumps in turn
4) at the end of the chain, the electrons combine with protons and oxygen to form water:

2H+ +2e- + 1/2O2 —> H2O

52
Q

Describe the passage of protons along the Electron transport chain

A

1) inner membrane in impermeable to protons and do the protons accumulate in the inter-membrane space
2)the concentration of protons in the inter-membrane space become a hugger than in the matrix, so an electro chemical gradient is set up, maintained by the proton pumps
3) in the membrane there are protein complexes (stalked particle) which are channels where protons flow back into the mitochondrial matrix. The enzyme ATPsynthase is associated with each channel. Protons diffuse back through these channels, and so their electrical potential energy produced ATP:
ADP + Pi —> ATP + H2O
4)At the end of the chain the protons combine with electrons and oxygen to form water

53
Q

What is oxygen referred to in the Electron Transport Chain?

A

‘The final electron acceptor’ or ‘The final hydrogen acceptor’ as it is essential to remove protons and electrons (as oxygen is reduced by the addition of electrons and protons to form water) allowing for a continuous ETC

54
Q

What is the effect of Cyanide on the ETC

A

Cyanide is a non-competitive inhibitor of the final carrier in the ETC and :: electrons and protons (H+ ions) can’t be transferred to water.

  • They accumulate, destroying the proton gradient.
  • ATPsynthase can’t operate and the cell dies very quickly
55
Q

For each molecule of glucose entering glycolysis the electron transport system receives what?

A

10 molecules of reduced NAD which generates 30ATP
2 molecules of reduced FAD which generates 4 ATP
2 ATP net from glycolysis
2 ATP net from substrate level phosphorylation in the Krebs cycle
:: Total ATP: 38 ATP synthesised in aerobic respiration

56
Q

What stage of respiration is possible in anaerobic conditions?

A

Glycolysis

57
Q

What can’t take place in the absence of oxygen?

A
  • no oxidative phosphorylation and :: no ATP formed
  • reduced NAD can’t be oxidised and :: no NAD is regenerated to pick up more hydrogen
  • :: the Krebs cycle and link reaction can’t take place
58
Q

How does glycolysis occur in anaerobic conditions?

A

Pyruvate accepts hydrogen from reduced NAD (regenerating NAD and removing hydrogen/pyruvate) continuing the cycle

59
Q

What is the only way ATP can be made in the absence of oxygen?

A

Via substrate level phosphorylation.

60
Q

What is the anaerobic pathway in animals where hydrogen is removed From reduced NAD?

A

Occurs in the cytoplasm. When deprived of oxygen (e.g muscle cells during vigorous exercise) pyruvate is a hydrogen acceptor and is converted to lactate, regenerating NAD.

61
Q

What happens to the Lactate in animals once oxygen becomes available?

A

The lactate is respired to carbon dioxide and water, releasing the energy it contains.

62
Q

What is the anaerobic pathway in various microorganisms such as yeast where hydrogen is removed From reduced NAD?

A

Pyruvate is converted to carbon dioxide and to ethanal, a hydrogen acceptor, by enzyme decarboxylase.
Ethanal is reduced to ethanol and NAD is regenerated, in alcoholic fermentation.

63
Q

What is the process where ethanal is reduced to ethanol and NAD is regenerated called in plants?

A

Alcoholic fermentation

64
Q

What is the problem with the anaerobic pathway in plants not being reversible

A

Even if oxygen becomes available again, ethanol is not broken down. It accumulates on the cell and can rise to toxic concentrations

65
Q

Give a summary sentence regarding anaerobic respiration in animals and other microorganisms

A

In the absence of oxygen the pyruvate produced during glycolysis is converted to either lactate or ethanol. This is necessary in order to deoxidise reduced NAD so that glycolysis can continue.

66
Q

What is the total of ATP molecules produced per glucose molecule?

A

38 ATP molecules are produced
10 reduced NAD (in glycolysis, link reaction and Krebs cycle) = 30ATP
2 reduced FAD (in the Krebs cycle) = 4 ATP
4 ATP from substrate level phosphorylation (in glycolysis and the Krebs cycle)

67
Q

Why is the 38 ATP molecules a theoretical total?

A

The cell is not 100% efficient because:

  • ATP is surf to move pyruvate, ADP, reduced NAD and reduced FAD across the mitochondrial membrane
  • The proton gradient may be compromised by proton leakage across the inner mitochondrial membrane, rather than passing through ATPsynthase
  • Molecules may also leak through membranes
68
Q

What is the actual average values of ATP molecules produced per molecule of glucose respires

A

30-32 molecules per glucose respired

69
Q

What is the efficiency of ATP production equation?

A

Energy made available through ATP/Energy released in combustion x100

(Energy made available through ATP is the energy required to make ATP (30.6kj/mile) multiplied by the 38 molecules released per 1 respired glucose molecule)

70
Q

What is the value of ATP molecules produced in the absence of oxygen (anaerobic respiration?)

A

Only by substrate level phosphorylation in glycolysis :: only 2 molecules

Much less efficient than aerobic respiration

71
Q

Why is the Krebs cycle sometimes called the ‘metabolic hub?’

A

Because the metabolic pathways of carbohydrates, lipids and proteins can feed into it.
Sometimes proteins and fats can be used as respiratory substrates

72
Q

Why is Acetyl coenzyme A a significant molecule in the Krebs cycle or ‘metabolic hub’?

A

It’s significant because it links the metabolism of proteins, carbohydrates and lipids.

(LOOK AT DIAGRAM ON PG 50)

73
Q

What is the benefit of lipids as a respiratory substrate?

A

Fat provides an energy store and is used as a respiratory substrate when carbohydrates in the body such as glycogen and blood glucose are low.

74
Q

Describe how lipids enter the respiratory pathway

A

1) fat is hydrolysed into glycerol and fatty acids
2) glycerol is phosphorylated with ATP, dehydrogenated with NAD and converted into a 3 carbon sugar (triose phosphate) which enters the glycolysis pathway

75
Q

Describe how energy in molecules egested contributes more to energy loss from a herbivores food chain than carnivores

A

Ruminants feed on plant material containing cellulose which is digested by mutualsitic micro-organisms and passed out as faeces which contain a high proportion of undigested material.
A carnivores protein rich diet is more efficiently digested and consequently only 20% of its energy is lost as waste compared to a ruminants 60%

76
Q

Describe other methods of energy loss from the food chain.

A

1) energy lost a respiratory heat following processes fuelled by the energy generated in respiration e.g muscle contraction
2) energy remains in molecules in parts of an animal/plant that may not be eaten e.g bones, fur or roots

77
Q

State the efficiency of energy transfer equation

A

Energy incorporate unto biomass after transfer/ energy available in biomass before transfer
x100

78
Q

What is an ecological pyramid?

A

A diagram that shows a particular feature of each trophic level in an ecosystem, these can include:

  • pyramid of numbers
  • pyramid of energy
  • pyramid of biomass
79
Q

Name a fault with ecological pyramids and a positive feature

A

Positive= useful in describing ecosystems

Negative= don’t recognise that some organisms operate at more than one trophic level at the same time (think about eating an egg sandwich, your a primary consumer when eating bread, but secondary consumer when eating egg)!

80
Q

Describe the positives and negatives of the pyramid of numbers:

A

Positives:
-easy to construct

Negatives:

  • doesn’t account for size of organisms
  • doesn’t recognise the difference between juvenile and adult forms
  • range of numbers may be so larger that it’s difficult to draw to scale
  • pyramid or part of it may be inverted
81
Q

What does the pyramid of energy show?

A

Shows the energy transfer from one trophic level to the next per unit area/volume per unit time.

82
Q

Why are pyramids of energy never inverted?

A

As material passes up through the food chain energy is lost from the ecosystem and :: areas of the bars decrease accordingly :: never inverted

83
Q

What is a positive of pyramids of energy?

A

Pyramids of energy make it easy to compare the efficiency of energy transfer between trophic levels in different communities

84
Q

Describe some positives and negatives of pyramids of biomass:

A

Positives:

Negatives:

  • difficult to measure accurately, for example all the plant roots must be included
  • pyramids of biomass may be inverted
  • trophic level may seem to contribute more to the next than it actually does as organisms contain structures e.g bone or beaks that will not transfer
  • species with similar biomass may have different life spans. A direct comparison of their total biomass is therefore misleading.
85
Q

Describe and example where there’s an inverted pyramid of biomass

A

In an aquatic ecosystem phytoplankton are major producers.
Lots of energy flows through the first trophic level and they reproduce quickly
Some are eaten immediately, leaving just enough to maintain the population
This means their standing crop (the mass of the individuals present at a given time is lower than the biomass or zooplankton which eat them) :: inverted pyramid of biomass.

Biology Unit 3 (7 decks)

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