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Biology Mock AS1 > Respiration > Flashcards

Respiration Flashcards

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1
Q

what is aerobic respiration

A

the process of breaking down a respiratory substrate (glucose) in order to produce ATP using oxygen

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2
Q

equation for aerobic respiration

A

C6H1206 + 6 O2 → 6 CO2 + 6 H20 + 2870kJ

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3
Q

what is the energy released during the process of aerobic respiration used for

A

used to phosphorylate (add a phosphate) ADP to form ATP

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4
Q

what are the four stages of aerobic respiration

state where each stage occurs

A

Glycolysis (cytoplasm)

Different parts of mitochondria:
The Link reaction (matrix of mitochondria)

The Krebs cycle (matrix of mitochondria)

Oxidative phosphorylation (inner membrane of mitochondria)

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5
Q

what is a coenzyme

A

non protein molecule that helps enzyme carry out function without being used in the reaction itself

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6
Q

what are the roles of NAD and FAD

A

the coenzymes responsible for transferring hydrogen between molecules hence being able to reduce or oxidise a molecule

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7
Q

what is Coenzyme A responsible for

A

transfer of acetate from one molecule to another

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8
Q

what are the four main structures of the mitochondira

and describe each one

A

The outer membrane
Smooth
Permeable to several small molecules

The inner membrane
Folded (cristae)
Less permeable
The site of the electron transport chain (used in oxidative phosphorylation)
Location of ATP synthase enzymes (used in oxidative phosphorylation)

The intermembrane space
Has a low pH due to the high concentration of protons
The concentration gradient across the inner membrane is formed during oxidative phosphorylation and is essential for ATP synthesis

The matrix
Is an aqueous solution within the inner membranes of the mitochondrion
Contains ribosomes, enzymes and circular mitochondrial DNA necessary for mitochondria to function

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9
Q

what ensures that the energy trapped within the chemical bonds of the glucose molecule is released gradually and not all at once

A

These chemical reactions are controlled by intracellular enzymes

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10
Q

why is a sudden release of a large amount of energy bad

A

would result in an increase in body temperature to levels that would denature enzymes

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11
Q

why is glycolysis the first step for both aerobic and anaerobic respiration

A

It does not require oxygen to take place

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12
Q

where does the partial oxidation of glucose occur during glycolysis and what does it involve

A

takes place in the cytoplasm

Trapping glucose in the cell by phosphorylating the molecule

Oxidising triose phosphate (by losing hydrogen)

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13
Q

what is produced in glycolysis during anaerobic conditions

A

produces lactic acid or lactate instead of pyruvate

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14
Q

what happens during the phosphorylation of glucose

A

Two molecules of ATP are required to provide the two phosphates needed for the phosphorylation of glucose producing two molecules of triose phosphate and two molecules of ADP

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15
Q

what happens during the oxidation of triose phosphate

A

After triose phosphate loses hydrogen, it forms two molecules of pyruvate

The hydrogen ions are collected by NAD which reduces the coenzyme

This forms two reduced NAD or NADH
Even though a total of four ATP molecules were produced during glycolysis, two of them were used to phosphorylate glucose

There was therefore a net gain of two ATP molecules

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16
Q

Draw the process of glycolysis

A
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17
Q

what is the end product of glucolysis

A

pyruvate

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18
Q

what does pyruvate contain

A

substantial amount of chemical energy that can be further utilised in respiration to produce more ATP

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19
Q

where are the enzymes and coenzymes required for the link reaction found

A

in the mitochondrial matrix

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20
Q

when oxygen is available where does the pyruvate go

A

pyruvate will enter the mitochondrial matrix and aerobic respiration will continue
Pyruvate moves across the double membrane of the mitochondria via active transport
Once in the mitochondrial matrix pyruvate takes part in the link reaction

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20
Q

what does pyruvate require to move across double membrane of the mitochondria

A

It requires a transport protein and a small amount of ATP

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21
Q

where does the pyruvate enter the mitochondrial matrix from

A

from the cytosol (cytoplasm) by active transport

22
Q

why is it referred to as the link reaction

A

because it links glycolysis to the Krebs cycle

23
Q

what are the steps of the link reaction

A

Pyruvate is oxidised (hydrogen is removed) by enzymes to produce acetate, CH3CO(O) (also known as acetic acid)

Pyruvate is also decarboxylated (carbon is removed) in the form of carbon dioxide

Reduction of NAD to NADH or reduce NAD by collecting hydrogen from pyruvate

Acetate combines with coenzyme A to form acetyl coenzyme A (acetyl CoA)

24
Q

is ATP produced during the link reaction and what is produced

A

No ATP is produced

Acetyl coA
CO2
NADH

25
Q

equation of Link reaction
DRAW THIS

A

pyruvate + NAD + CoA → acetyl CoA + carbon dioxide + reduced NAD

26
Q

why will the link reaction and Krebs cycle occur twice for every molecule of glucose

A

Every molecule of glucose produces two pyruvate molecules

Hence, each molecule of glucose will produce:
Two molecules of acetyl CoA
Two molecules of CO2
Two molecules of reduced NAD

27
Q

What does the Krebs cycle consist of

A

a series of enzyme-controlled reactions

2 carbon (2C) Acetyl CoA enters the circular pathway from the link reaction in glucose metabolism

4 carbon (4C) oxaloacetate accepts the 2C acetyl fragment from acetyl CoA to form the 6 carbon (6C) citrate

Coenzyme A is released in this reaction to be reused in the next link reaction

Citrate is then converted back to oxaloacetate through a series of oxidation-reduction (redox) reactions

28
Q

Draw Kreb cycle

A
29
Q

when can Acetyle CoA be entered directly into the Krebs Cycle

A

Acetyl CoA formed from fatty acids (after the breakdown of lipids) and amino acids enters directly into the Krebs Cycle from other metabolic pathways

30
Q

where is Oxaloacetate regenerated

A

regenerated in the Krebs cycle through a series of redox reactions

31
Q

Describe process of regeneration of oxaloacetate

A

Decarboxylation of citrate
Releasing 2 CO2 as waste gas

Oxidation (dehydrogenation) of citrate
Releasing H atoms that reduce coenzymes NAD and FAD
These will be used during oxidative phosphorylation
3 NAD and 1 FAD → 3NADH + H+ and 1 FADH2

Substrate linked phosphorylation
A phosphate is transferred from one of the intermediates to ADP, forming 1 ATP to supply energy

32
Q

why are two cycle required per glucose molecule during the regeneration of oxaloacetate

A

Because two acetyl-CoA molecules are produced from each glucose molecule

Therefore, at the end of two cycles, the products are:
Two ATP
Six NADH (reduced NAD)
Two FADH2 (reduced FAD)
Four CO2

33
Q

where does oxidative phosphorylation occur and what does it produce

A

it takes place at the inner mitochondrial membrane

It results in the production of many molecules of ATP and the production of water from oxygen

34
Q

explain the chemiosmotic theory of oxidative phosphorylation

A

energy from electrons is passed through a chain of proteins in the membrane, known as the electron transport chain

This energy is used to pump protons (hydrogen ions) against their concentration gradient into the intermembrane space

The protons are then allowed to flow by facilitated diffusion through a channel enzyme called ATP synthase into the matrix

The energy of the protons flowing down their concentration gradient resulting in the phosphorylation of ADP into ATP by ATP synthase

35
Q

where are hydrogen atoms donated from and what do the hydrogen atoms do (outline of oxidative phosphorylation)

A

by reduced NAD (NADH) and reduced FAD (FADH2) from the Krebs Cycle

Hydrogen atoms split into protons (H+ ions) and electrons
The high energy electrons enter the electron transport chain and release energy as they move through the electron transport chain

The energy released is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space

A concentration gradient of protons is established between the intermembrane space and the matrix

The protons return to the matrix via facilitated diffusion through the channel enzyme ATP synthase

The movement of protons down their concentration gradient provides energy for ATP synthesis

Oxygen acts as the ‘final electron acceptor’ and combines with protons and electrons at the end of the electron transport chain to form water

36
Q

structure of electron transport chain

A

a series of membrane proteins/ electron carriers

They are positioned close together which allows the electrons to pass from carrier to carrier

The inner membrane of the mitochondria is impermeable to hydrogen ions so these electron carriers are required to pump the protons across the membrane to establish the concentration gradient

37
Q

what does oxidative phosphorylation use energy for from the reduced NAD and FAD

A

Oxidative phosphorylation uses energy from reduced NAD and FAD to produce ATP

3 ATP molecules for every reduced NAD molecule
2 ATP molecules for every reduced FAD molecule

38
Q

how many ATP molecules produced during aerobic respiration for every molecule of glucose

A

38 ATP molecules

39
Q

why is oxygen important for aerobic respiration

A

Oxygen acts as the final electron acceptor. Without oxygen the electron transport chain cannot continue as the electrons have nowhere to go. Without oxygen accepting the electrons (and hydrogen ions) the reduced coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD, so they can’t be used in further hydrogen transport.

40
Q

method for investigating the rate of respiration

A

Measure oxygen consumption: set up the respirometer and run the experiment with both tubes for a set amount of time (e.g. 30 minutes)

As the seeds consume oxygen, the volume of air in the test tube will decrease (CO2 produced during respiration is absorbed by soda lime or KOH)

This reduces the pressure in the capillary tube and manometer fluid will move towards the test tube containing the seeds

Measure the distance moved by the liquid in a given time
Use this measurement to calculate the change in gas volume within a given time

Reset the apparatus: Allow air to re-enter the tubes via the screw cap and reset the manometer fluid using the syringe
Repeat experiment several times and calculate the average volume of oxygen consumed

41
Q

how can the volume of oxygen consumed be worked out

A

The diameter of the capillary tube r (cm)

The distance moved by the manometer fluid h (cm) in a minute using the formula

πr2h

42
Q

consequences of not enough oxygen available for respiration

A

There is no final acceptor (oxygen) of electrons from the electron transport chain

The electron transport chain stops functioning

No more ATP is produced via oxidative phosphorylation

Reduced NAD and FAD aren’t oxidised by an electron carrier

No oxidised NAD and FAD are available for dehydrogenation in the Krebs cycle

The Krebs cycle stops

The link reaction also stops

43
Q

what are the anaerobic pathways

A

Some cells are able to oxidise the reduced NAD produced during glycolysis so it can be used for further hydrogen transport

This means that glycolysis can continue and small amounts of ATP are still produced

Certain types of micro-organisms and mammalian muscle cells use lactate fermentation

44
Q

explain lactate fermentation

A

In this pathway reduced NAD
transfers hydrogen to pyruvate to form lactate

NAD can now be reused in glycolysis

Pyruvate is reduced to lactate by enzyme lactate dehydrogenase

Pyruvate is the hydrogen acceptor
The final product lactate can be further metabolised

A small amount of ATP is produced

45
Q

what two things happen after lactate is produced

A

It can be oxidised back to pyruvate which is then channelled into the Krebs cycle for ATP production

It can be converted into glucose by the liver cells for use during respiration or for storage (in the form of glycogen)

46
Q

why do animals breathe deeper and faster after exercise

A

The oxidation of lactate back to pyruvate needs extra oxygen
This extra oxygen is referred to as an oxygen debt

47
Q

why is ATP used in the start of glycolysis

A

to make glucose more reactive and reduce activation energy

48
Q

importance of outer mitochondrial membrane being impermeable to hydrogen ions

A

to stop H* diffusing out (of mitochondrion) / into cytoplasm (1)
* (therefore) maintaining a high concentration (of H* in the intermembrane space (1)
so {hydrogen ions / protons / H*) can move down (concentration / electrochemical gradient (1)
* (by) chemiosmosis (1)
* to synthesise ATP (1)

49
Q

explain why some ATP is broken down during glycolysis

A

(because the breakdown of ATP) (donates phosphate to / phosphorylates} the glucose (1)
* (ATP) supplies energy to break down the glucose (1)
to produce (phosphorylated) 3-carbon compounds (1)

50
Q

explain the role of carrier molecules in the electron transport chain

A

receive hydrogen from reduced NAD AND FAD
split hydrogen into electron and H+ and protons
the electrons are transferred down the electron transport chain via redox reactions
energy released is used to pump protons into the intermembrane space

51
Q

why is ATP required to convert F6P to F26BP

A

hydrolysis of ATP (1)
provides energy for the reaction (1)
provides phosphate group for phosphorylation of
F-6-P

52
Q

what is the need for reduced NAD to be oxidised in the mitochondira

A

so that hydrogen can be delivered to the electron transport chain (1)
to allow { ATP synthesis / chemiosmosis } (1)
to regenerate NAD (1)

53
Q
A

Biology Mock AS1 (8 decks)

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