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Biology > -5.2.2 Respiration > Flashcards

-5.2.2 Respiration Flashcards

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1
Q

What is the word equation for aerobic respiration?

A

Glucose + oxygen —> water + carbon dioxide + energy

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2
Q

What processes require energy?

A

Endocytosis,
Exocytosis,
Metabolic processes (protein syntheis eg)
Movement
Active transport
DNA replication
Activation of molecules (eg phosphorylation of glucose)
Maintenance of body temperature

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3
Q

Why is ATP the energy currency of the cell?

A

ATP is an immediate energy source as it is quickly made and broken down.
The hydrolysis of ATP releases small, manageable quantities of energy transferred to cellular processes.

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4
Q

Why is it ideal that respiration occurs in the mitochondria?

A

Mitochondria provide an isolated environment to provide ideal conditions for respiration. They also have their own DNA to produce the enzymes required for respiration.

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5
Q

What is the definition of a coenzyme?

A

A molecule that aids the function of an enzyme by transferring a chemical group from one molecule to another.

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6
Q

What does coenzyme A do in respiration?

A

It transfers acetate between molecules.

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7
Q

What do NAD and FAD do?

A

They are coenzymes that transfer protons (H+) and electrons (e-) from one molecule to another.
This means that they can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule.

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8
Q

What does hydrogen split into?

A

A proton and an electron.

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9
Q

What are the four stages of respiration?

A

Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation

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10
Q

How do the 4 stages of photosynthesis interact?

A

The first 3 stages are a series of reactions.
The products of these 3 stages are used in the final stage to produce lots of ATP.

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11
Q

What does glycolysis do in respiration?

A

It is the first stage.
Glycolysis makes 2x pyruvate from glucose.
One molecule of glucose is split into 2 pyruvate.
This occurs in the cytoplasm.
Glycolysis is anaerobic - it doesn’t require oxygen. It is the first stage of both aerobic and anaerobic respiration.

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12
Q

What are the two stages of gylcolysis?

A

Phosphorylation and oxidation.

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13
Q

What is phosphorylation and dephosphorylation?

A

Phosphorylation is the addition of an inorganic phosphate to a protein.
Dephosphorylation is the removal of a phosphate.

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14
Q

What is lysis?

A

It is splitting by destabilisation.

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15
Q

What kind of phosphorylation is glycolysis?

A

It is an example of substrate level phosphorylation - which is the formation of ATP without the electron transport chain

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16
Q

What is the ATP yield from glycolysis?

A

Two molecules of ATP. 2 enter the process and 4 leave.

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17
Q

What is the reduced NAD from glycolysis used for?

A

It is used in a later stage of respiration to synthesise more ATP.

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18
Q

What is the full process of glycolysis?

A

Starts with glucose.

Phosphorylation - 2 phosphates are released from 2 ATP molecules and attached to glucose to form hexose bisphosphate.

Lysis - Hexose bisphosphate is split into 2 molecules of triose phosphate.

Phosphorylation - another phosphate group is added to each triose phosphate to form triose bisphosphate. (free Pi in cytoplasm)

Dehydrogenation and formation of ATP - the triose bisphosphate molecules are oxidised by removal of hydrogen (dehydrogenation) to form 2 pyruvate molecules. NAD accepts the removed H (NADH now)

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19
Q

Where does the pyruvate from glycolysis go?

A

It enters the link reaction.

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20
Q

What happens in the link reaction?

A

Oxidative decarboxylation of pyruvate. Removal of CO2 and a hydrogen which is picked up by NAD.
An acetyl group is left from the pyruvate, this combines with coenzyme A to form acetyl coenzyme A (2 carbons).

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21
Q

Where does the link reaction take place?

A

The mitochondrial matrix, the pyruvate gets there by active transport through a carrier protein.

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22
Q

Where does acetylcoenzyme A go after the link reaction?

A

It enters the Krebs cycle.

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23
Q

What does each cycle of the Krebs cycle result in?

A

The breakdown of one acetyl group.

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24
Q

What processes does the Krebs cycle involve?

A

Decarboxylation, dehydrogenation and substrate-level phosphorylation.

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25
What is a byproduct of respiration?
Carbon dioxide.
26
What is produced in the Krebs cycle?
CO2 which is released as a waste product. ATP which is used in the cell. Reduced NAD and FAD enter the final stage of respiration.
27
What are the stages of the Krebs cycle?
1- Acetyl CoA delivers an acetyl group which combines with oxaloacetate (OAA) to form 6-carbon citrate. 2- Citrate undergoes decarboxylation and dehydrogenation which produces one NADH and CO2. A 5-carbon compound is formed. 3- The 5-carbon compound undergoes further decarboxylation and dehydrogenation reactions, eventually regenerating oxaloacetate. The cycle continues.
28
What is the total yield of ATP from glycolysis and Krebs cycle? (total yield of ATP from first 3 stages)
2 from both. 4 ATP yield total per glucose molecule.
29
What is the total yield of NADH from glycolysis, the link reaction and the Krebs cycle?
2 from glycolysis. 2 from the link reaction. 6 from the Krebs cycle. 10 NADH yielded total for one glucose molecule.
30
What is the total yield of FADH2 from the Krebs cycle?
2
31
What is the total yield from the link reaction and Krebs cycle?
2 from link. 4 from Krebs. 6 total per glucose molecule.
32
Where does glycolysis occur?
Cytoplasm of the cell.
33
Where does the link reaction take place?
Mitochondrial matrix.
34
Where does the Krebs cycle take place?
Mitochondrial matrix
35
What are the net products of glycolysis?
2 ATP 2 NADH 2 pyruvate
36
What are the net products of the link reaction?
2 acetylcoenzyme A 2 NADH 2 CO2
37
What are the net products of the Krebs cycle?
2 ATP 2 FADH2 6 NADH 4 CO2
38
Where does oxidative phosphorylation take place?
Across the inner membrane of the mitochondrion. Energy carried by electrons from reduced NAD and FAD is transferred to produce ATP.
39
What is the process of oxidative phosphorylation? Final stage of respiration.
Reduced NAD and reduced FAD release hydrogen atoms and become oxidised. The hydrogen atoms split into protons (H+0 and electrons (e-). The electrons move along the electron transport chain, losing energy at each carrier. When a carrier receives electrons, it is reduced. When it passes on the electron it becomes oxidised again. Some of this energy is transferred to pump H+ from the matrix into the intermembrane space, the rest is lost as heat. The concentration of protons in now higher in the intermembrane space than in the matrix. Protons move down their electrochemical gradient back into the matrix via ATP synthase. This movement drives synthesis of ATP from ADP and Pi. This is chemiosmosis. The final electron acceptor is oxygen. Oxygen combines with protons (H+) and electrons (e-) to form water.
40
What is the theoretical yield of ATP in respiration?
38 ATP per glucose molecule.
41
Why is the actual yield of ATP usually lower than the theoretical yield of 38?
Some of the ATP is used to actively transport pyruvate into the mitochondria. Some ATP is used to transport reduced NAD from glycolysis into the mitochondria. Some protons may leak out through the outer mitochondrial membrane.
42
What are the differences between NAD and FAD?
NAD takes place in all stages of respiration, FAD only accepts hydrogen in the Krebs cycle. NAD accepts one hydrogen and FAD accepts two. Reduced NAD is oxidised at the start of the electron transport chain releasing electrons and protons while reduced FAD is oxidised further along the chain. Reduced NAD results in the synthesis of 3 ATP molecules but reduced FAD results in the synthesis of only 2 ATP molecules.
43
How many ATP does anaerobic respiration yield?
Only 2.
44
What categories do organisms fall into determined by their dependence on oxygen?
Obligate anaerobes - cannot survive in the presence of oxygen, almost all of these are prokaryotes. Facultative anaerobes - synthesise ATP by aerobic respiration if oxygen is present but can switch to anaerobic if required, eg yeast. Obligate aerobes - can only synthesise ATP in the presence of oxygen, eg mammals. Only temporary and short periods of anaerobic respiration in a few cells, eg mitochondria.
45
How does a lack of oxygen prevent aerobic respiration?
Without oxygen, oxidative phosphorylation and the Krebs cycle cannot function. Reduced coenzymes accumulate in the cell. Eventually, all the NAD+ is converted to NADH and metabolism stops.
46
What is fermentation and when does it occur?
It occurs in the absence of oxygen. Organic compounds are not fully broken down so less ATP is produced than aerobic respiration. The small amount of ATP is produced by substrate-level phosphorylation only as the electron transport chain cannot run. When there is no oxygen to act as the final electron acceptor, the flow of electrons stops. This means that ATP synthesis by chemiosmosis stops too.
47
What is lactate fermentation in mammals?
Pyruvate can act as the final electron acceptor, taking hydrogen from reduced NAD (NADH). It is catalysed by lactate dehydrogenase. Pyruvate is converted into lactate (lactic acid). NAD+ is thus regenerated. Lactic acid is converted back into glucose in the liver, requiring oxygen.
48
What are the 2 reasons that lactate fermentation cannot occur indefinitely?
The reduced quantity of ATP wouldn't be enough to sustain vital processes for a long period of time. The accumulation of lactic acid causes a fall in pH which would inhibit respiratory enzymes.
49
What is the equation for lactate fermentation?
Pyruvate + NADH ---> lactate + NAD+
50
Describe the process of alcoholic fermentation in plants and yeast.
Pyruvate is the starting compound. (3C) CO2 is removed by pyruvate decarboxylase. Now we have ethanal (2C). Ethanal is reduced by reduced NAD (NADH) by transferring a hydrogen to form ethanol. NAD+ can now be reused in glycolysis.
51
Is alcoholic fermentation reversible?
NO
52
What is the hydrogen acceptor is lactate fermentation?
Pyruvate
53
Is CO2 produced in lactate fermentation?
NO
54
Is ATP produced in lactate fermnetation?
Only in glycolysis.
55
What are the end products of lactate fermentation?
Lactate, NAD+
56
What is the enzyme involved in lactate fermentation?
Lactate dehydrogenase
57
Where is the site of lactate fermentation?
Cytoplasm of mammalian muscle.
58
What is the hydrogen acceptor in alcoholic fermentation?
Ethanal
59
Is CO2 produced in alcoholic fermentation?
YES
60
Is ATP produced in alcoholic fermentation?
Only in glycolysis.
61
What are the end products of alcoholic fermentation?
Ethanol, NAD+, CO2
62
What are the enzymes involved in alcoholic fermentation?
Pyruvate decarboxylase, ethanol dehydrogenate.
63
What is the site of alcoholic fermentation?
Cytoplasm of yeast or plant cells.
64
What is a respiratory substrate?
A biological molecule that can be broken down in respiration to release energy.
65
What are the respiratory substrates that can be used by cells?
Glucose mainly but also carbohydrates, lipids and proteins.
66
Where do carbohydrates enter respiration?
In glycolysis
67
Where do lipids and proteins enter respiration?
Krebs cycle
68
What is the order of energy values for carbohydrates, lipids and proteins?
Lipids > proteins > carbohydrates
69
Why do lipids have the highest energy value?
Most ATP is made during oxidative phosphorylation. Hydrogen atoms are required from NADH and FADH2. Respiratory substrates that contain more hydrogen atoms per unit of mass allow more ATP to be produced.
70
How are lipids respired?
Triglycerides are hydrolysed into glycerol and fatty acids. Glycerol is then converted to triose phosphate and respired. The fatty acid is combined with coenzyme A. This complex is transported into the mitochondrial matrix where it is broken down into acetyl groups attached to CoA. The acetyl groups are released from CoA and enter the Krebs cycle.
71
What happens to excess protein?
It is deaminated in the liver (the amino group is removed and converted to urea). The rest of the amino acid, a keto acid, enters the respiratory pathway as pyruvate, acetyl coA or a krebs cycle acid eg oxaloacetic acid.
72
What are the two equations to work out the respiratory quotient?
RQ = volume of CO2 released / volume of O2 consumed RQ = molecules of CO2 released / molecules of O2 consumed
73
What is a respiratory quotient?
It is the volume of carbon produced when that substrate is respired, divided by volume of oxygen consumed during a set period of time.
74
Why do respiratory quotients between molecules differ?
Because the number of carbon-hydrogen bonds differs.
75
What is the respiratory quotient of lipids, proteins or amino acids and carbohydrates?
Lipids = 0.7 Proteins or amino acids = 0.9 Carbohydrates = 1
76
What does it mean that lipids and proteins have a RQ of lower than 1?
More oxygen is required to oxidise fats and lipids than to oxidise carbohydrates.
77
What does it mean if the RQ is more than 1?
It means that anaerobic respiration is taking place because more carbon dioxide is being produced than oxygen is being consumed.
78
How can you work out the respiratory quotient for a whole organism?
You calculate a mean of all respiratory quotients for all the different respiratory quotients.
79
Why is it useful to calculate the RQ for whole organisms?
It tells you what kind of respiration is taking place and which respiratory substrates are being used.
80
How do you use a respirometer?
A known mass of organisms, eg woodlice, germinating seeds, maggots are placed in 1 respirometer tube. The manometer fluid is placed into the manometer tube and the apparatus is connected with the tubes open. The apparatus is placed in a water bath for 10 minutes. The level of the fluid is marked with a pen. The taps are closed, and the apparatus is left for 10 minutes. The change in the level of manometer fluid is measured and if the radius of the tube is known, can be used to calculate a volume. The syringe barrel can be used to reset the apparatus. The volume of oxygen absorbed per gram of living organisms per minute can then be calculated. Soda lime or hydrogen carbonate can be used to absorb carbon dioxide released.
81
Why is a thin layer of oil used when measuring respiration rates in yeast?
It can be used to exclude oxygen and cause yeast to respire anaerobically.
82
What does it mean that methylene blue and DCPIP are redox indicators?
This means that they change colour when they are reduced from blue to colourless. The faster the rate of respiration, the faster the colour change. When oxygen dissolved in the methylene blue, it is reoxidised and turns blue.

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