Module 5 Section 6: Respiration Flashcards

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1
Q

4 stage of respiration

A

Glycolysis, the link reaction, krebs cycle, oxidative phosphorylation

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2
Q

How do the 4 stages of respiration interact and link together

A

First three stages are a series of reactions.
The products from these reactions are used in the final stage to produce ATP

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3
Q

Where do the stages of photosynthesis take place

A

Glycolysis happens in the cytoplasm of cells
Link reaction, Krebs cycle and oxidative phosphorylation take place in the mitochondria.

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4
Q

Structure of mitochondrion

A
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5
Q

What can the glucose that is respired be replaced by

A

All cells use glucose to respire, but organisms can also break down other complex organic molecules (e.g. fatty acids, amino acids), which can then be respired

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6
Q

What does stage one of respiration create

A

Glycolysis Makes Pyruvate from Glucose

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7
Q

Overview of glycolysis

A

Glycolysis involves splitting one molecule of glucose (with 6 carbons - 6C) into two smaller molecules of pyruvate (3C)
The process happens in the cytoplasm of cells.
Glycolysis is the first stage of both aerobic and anaerobic respiration and doesn’t need oxygen to take place - so it’s an anaerobic process

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8
Q

Process of glycolysis

A

Phosphorylation:
Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP.
This creates 1 molecule of hexose bisphosphate and 2 molecules of ADP.
Then, hexose bisphosphate is split up into 2 molecules of triose phosphate.

Oxidation:
Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate.
NAD collects the hydrogen ions, forming 2 reduced NAD.
4 ATP are produced, but 2 were used up in stage one, so there’s a net gain of 2 ATP

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9
Q

Draw process of glycolysis

A
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10
Q

What is reduced NAD also called

A

NADH

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11
Q

What happens to the products of glycolysis

A

The two molecules of reduced NAD go to the last stage (oxidative phosphorylation)
The two pyruvate molecules are actively transported into the matrix of the mitochondria for the link reaction

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12
Q

Where does the link reaction take place

A

In the mitochondrial matrix

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13
Q

Process of link reaction

A

Pyruvate (3C) is transported to the matrix of the mitochondria
Pyruvate is decarboxylated removing a single carbon as CO2
NAD is reduced to NADH — it collects hydrogen from pyruvate, changing pyruvate into acetate
Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA).

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14
Q

Draw diagram of link reaction

A
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15
Q

How many cycles of link reaction does one glucose molecule provide

A

For every glucose molecule, 2 pyruvate is made in glycolysis so link reaction can cycle twice meaning:
Two molecules of acetyl coenzyme A go into Krebs cycle
Two CO2 molecules are released as waste product of respiration
Two molecules of reduced NAD are formed and go to last stage (oxidative phosphorylation)

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16
Q

Stage 1 of Krebs cycle: citrate formed

A

Acetyl group from acetyl CoA (produced in link reaction) combines with oxaloacetate to form citrate (citric acid) which is a 6C compound
This is catalysed by citrate synthase
Coenzyme A goes back to the link reaction to be used again

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17
Q

Stage 2 of Krebs cycle: citrate turned into 5C molecule

A

The 6C citrate molecule is converted to a 5C molecule (intermediate)
Decarboxylation occurs where CO2 is removed
Dehydrogenation also occurs where hydrogen is removed
The hydrogen is used to produce reduced NAD from NAD

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18
Q

Stage 3 of Krebs cycle: oxaloacetate reformed

A

The 5C molecules is then converted to a 4C molecule
(There are some intermediates compounds formed during this conversion but don’t need to know them)
Decarboxylation and dehydrogenation occur, producing one molecule of reduced FAD and two reduced NAD
ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP
When a phosphate group is directly transferred from one molecule to another its called substrate level phosphorylation
Citrate has now been converted into oxaloacetate

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19
Q

Draw Krebs cycle

A
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20
Q

Products per cycle of Krebs cycle

A

3 reduced NAD
1 reduced FAD
1 АТР
2 CO2

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21
Q

Products per glucose molecule for Krebs cycle

A

6 reduced NAD
2 reduced FAD
2 АТР
4CO2

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22
Q

Where does Krebs cycle occur

A

Mitochondrial matrix

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23
Q

Full process of oxidative phosphorylation

A

Hydrogen atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD. The H atoms split into protons (H+) and electrons (e-).
The electrons move along the electron transport chain (made up of three electron carriers) in the inner mitochondrial membrane
They lose energy at each carrier
This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space
The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix — this forms an electrochemical gradient
Protons move down the electrochemical gradient, back into the mitochondrial matrix, via ATP synthase.
This movement drives the synthesis of ATP from ADP and inorganic phosphate (Pi)
This process of ATP production driven by the movement of H+ ions across a membrane (due to electrons moving down an electron transport chain) is called chemiosmosis
In the mitochondrial matrix, at the end of the transport chain, the protons, electrons and O2 (from the blood) combine to form water.
Oxygen is said to be the final electron acceptor.

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24
Q

Where does 1 coenzyme A go after Krebs cycle

A

Reused in next link reaction

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25
Q

Where does oxaloacetate go after Krebs cycle

A

Regenerated for use in next Krebs cycle

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26
Q

Where does the 2 CO2 go after Krebs cycle

A

Released as a waste product

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27
Q

Where does the 1 ATP go after Krebs cycle

A

Used for energy

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28
Q

Where does the 3 reduced NAD produced go after Krebs cycle

A

To oxidative phosphorylation

29
Q

Where does the 1 reduced FAD go after Krebs cycle

A

To oxidative phosphorylation

30
Q

What is oxidative phosphorylation

A

Oxidative phosphorylation is the process where the energy carried by electrons, from reduced coenzymes (reduced NAD and reduced FAD), is used to make ATP.
The point of the previous stages is to make reduced NAD and reduced FAD for the final stage

31
Q

Where does oxidative phosphorylation take place

A

Takes place in the inner mitochondrial membrane

32
Q

How many ATP molecules can be made from one glucose molecule over the whole of respiration

A

32 ATP

33
Q

How many molecules of ATP are made from each coenzyme in oxidative phosphorylation

A

In oxidative phosphorylation 2.5 ATP are made from reduced NAD and 1.5 ATP are made from each reduced FAD

34
Q

What doesn’t anaerobic respiration require

A

Oxygen
Doesn’t use link reaction, Krebs cycle or oxidative phosphorylation

35
Q

Two types of anaerobic respiration

A

Alcoholic fermentation and lactate fermentation

36
Q

Similarities and differences between alcoholic fermentation and lactate fermentation different

A

Both take part in the cytoplasm and both start with glycolysis
Differ in which organisms they occur in and what happens to pyruvate

37
Q

Process of lactate fermentation

A

Reduced NAD (from glycolysis) transfers hydrogen to pyruvate to form lactate and NAD.
NAD can then be reused in glycolysis.

38
Q

How does lactate fermentation still fuel some biological processes

A

The production of lactate regenerates NAD.
Glycolysis needs NAD in order to take place.
This means glycolysis can continue even when there isn’t much oxygen, so a small amount of ATP can still be produced to keep some biological process going.

39
Q

What happens when lactate starts to build up

A

Our cells can only tolerate a high level of lactate (and the coinciding low pH conditions) for short periods of time.
E.g. during short periods of hard exercise, when they can’t get enough ATP from aerobic respiration

However, too much lactate is toxic and is removed from the cells into the bloodstream.
The liver takes up lactate from the bloodstream and converts it back into glucose in a process called gluconeogenesis

40
Q

In what organisms does lactate fermentation occur

A

Mammals and bacteria

41
Q

Process of alcoholic fermentation

A

CO2 is removed from pyruvate to form ethanal.
Reduced NAD (from glycolysis) transfers hydrogen to ethanal to form ethanol and NAD.
NAD can then be reused in glycolysis

42
Q

How does alcoholic fermentation still fuel some biological processes

A

The production of ethanol also regenerates NAD so glycolysis can continue when there isn’t much oxygen around

43
Q

In what organisms does alcoholic fermentation occur

A

Yeast cells and plants

44
Q

What else can cells respire

A

Cells respire glucose as well as carbohydrates, lipids and proteins
Cells can respire different substrates
Any biological molecule that can be broken down in respiration to release energy is called a respiratory substrate

45
Q

Where do lipids and proteins enter respiration

A

The Krebs cycle

46
Q

How to tell how suitable something is to be respired

A

Different respiratory substrates release different amounts of energy when they’re respired

47
Q

What has the best energy value and why

A

Lipids release the most energy followed by proteins and then carbohydrates
Lipids contain the most hydrogen atoms per unit of mass, followed by proteins and then carbohydrates.
Respiratory substrates that contain more hydrogen atoms per unit of mass cause more ATP to be produced when respired.
Because most ATP is made in oxidative phosphorylation, which requires hydrogen atoms from reduced NAD and reduced FAD.

48
Q

What is a respiratory quotient (RQ)

A

This is what can be worked out when an organism respires a specific respiratory substrate
The RQ is the volume of carbon dioxide produced when that substrate is respired, divided by the volume of oxygen consumed, in a set period of time

49
Q

Equation for respiratory quotient

A
50
Q

How to work out the RQ for cells that only respire glucose

A

Equation for respiration:
C6H12O6 + 6O2 -> 6CO2 + 6H2O
RQ of glucose = molecules of CO2 released / molecules of O2 consumed
6/6 = 1

51
Q

Explain the values in the table of RQs for carbohydrates, proteins and lipids

A

Lipids and proteins have an RQ value lower than one because more oxygen is needed to oxidise them than to oxidise carbohydrates

52
Q

What information can RQs provide

A

RQ for an organism says what kind of respiratory substrate an organism is respiring
Says type of respiration it’s using (aerobic or anaerobic).

E.g. under normal conditions the usual RQ for humans is 0.7-1.0.
An RQ in this range shows that some fats (lipids) are being used for respiration, as well as carbohydrates (glucose)
Protein isn’t normally used by the body for respiration unless there’s nothing else

53
Q

What do high RQs tell you

A

High RQs (greater than 1) mean that an organism is short of oxygen, and is having to respire anaerobically as well as aerobically.
Plants sometimes have a low RQ.
This is because the CO2 released in respiration is used for photosynthesis (so it’s not measured)

54
Q

What dye to use to measure aerobic respiration

A

Methylene blue is a redox indicator dye that can take the place of electron acceptors in oxidative phosphorylation
Changes blue to colourless.
The rate of colour change shows the rate of respiration of the yeast.

55
Q

Method of measuring aerobic respiration

A

Known volume and concentration of substrate solution (e.g. glucose) in a test tube.
Add known volume of buffer solution to keep the pH constant.
Place the test tube in a water bath set to 25°C.
This ensures that the temperature stays constant throughout the experiment (leave it there for 10mins to stabilise temperature)
Add known volume of yeast suspension to test tube and stir for 2mins
Add known volume of methylene blue and seal the tube with a bung.
Shake the test tube for set number of seconds (e.g. 10 seconds) and place it back in water bath.
Start a stopwatch immediately afterwards.
Record how long it takes for the solution in the test tube to change from blue to colourless.
Use control to compare colours
Repeat steps 1-5 three times and calculate mean time for the colour change to occur.
Calculate mean rate of respiration of the yeast using the following equation:
Mean rate of respiration = 1 / mean time for colour change to occur

56
Q

Process behind measuring anaerobic respiration

A

Yeast produces CO2 when it respires anaerobically, so the rate at which CO2 is produced gives an indication of the yeast’s respiration rate.
Measured using gas syringe

57
Q

Method to determine rate of anaerobic respiration

A

Known conc and volume of substrate solution in test tube, add known volume of buffer solution to test tube, place in 25° water bath, then add known volume of yeast suspension
Trickle liquid paraffin down inside of test tube so that it settles on and completely covers the surface of the solution.
This will stop oxygen getting in, which forces the yeast to respire anaerobically.
Put a bung, with a tube attached to a gas syringe, in the top of the test tube and start a stopwatch.
Set gas syringe to zero.
As the yeast respire, the CO2 formed will push gas into the syringe, which measures volume of CO2 released.
Record the volume of gas in the gas syringe at regular time intervals (every minute).
Do this for a set amount of time (10mins).
Repeat the experiment three times and calculate mean rate of CO2 production.

58
Q

How to increase validity of aerobic respiration experiment

A

Set up test tube containing water (instead of substrate solution and buffer solution) to act as a control.
After the yeast and methylene blue is added, it shouldn’t decolourise as the yeast will not be respiring aerobically.

59
Q

How to increase validity of anaerobic respiration experiment

A

A negative control experiment should also be set up, where no yeast is present.
No CO2 should be formed without the yeast

60
Q

How to measure variables affecting both aerobic and anaerobic respiration

A

Repeat the same experiments but change certain variables e.g:
Substrate concentration: replace glucose with sucrose
Temperature: put test tubes in water baths of different temperatures

61
Q

How are respirometers used

A

Used to indicate rate of aerobic respiration
Measures how much oxygen is consumed by an organism over a period of time
Can be used to measure respiration of small organisms like woodlice or seeds

62
Q

How to set up respirometer

A

Each test tube contains KOH (potassium hydroxide), also known as soda lime, which absorbs CO2
Control tube set up in same way but without living organisms (may use glass beads which have same mass as organism but don’t respire)
Coloured fluid is added to the manometer through capillary action
Apparatus left for a set period of time (20mins)

63
Q

How does a respirometer work

A

During the time you leave the respirometer to set there’ll be a decrease in volume of air in test tube
This is due to oxygen consumption by organism (CO2 produced is absorbed by soda lime)
Decrease in volume of air reduced pressure in the tube and cause the coloured liquid in manometer to move towards the test tube
Distance move by the liquid in a given time is measured
This can be used to calculate volume of oxygen taken in per min

64
Q

Equation to measure the rate oxygen taken up per min in a respirometer

A

Volume calculated using:
πr^2h
Divide this by time taken

65
Q

How to make sure the results from a respirometer are more accurate

A

Any variables which can affect the results are controlled
E.g. temperature, volume of KOH is kept the same

66
Q

How to increase precision and validity of results from respirometer

A

Experiment is repeated and a mean volume of O2 is calculated
Use electronic oxygen sensor and data logger to record O2 conc at set intervals
Data is then put into data analysis software to help draw conclusions from experiment

67
Q

Limitations of using a respirometer

A

Can be difficult to accurately read meniscus of the fluid in manometer

68
Q

Adaptations of inner mitochondrial membrane for chemiosmosis to occur

A

Large surface area
Membrane mostly impermeable to H+, forcing it to travel through proteins
Contains ATP synthase to produce ATP from ADP and Pi