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A level Biology > 5.7 respiration > Flashcards

5.7 respiration Flashcards

1
Q

Why do living organisms need to respire?

A

Respiration releases energy from respiratory substrates such as glucose, but it does not create or make energy

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2
Q

Why is it inacurate to say respiration creates energy

A

Because it releases energy from respiratory substances. That energy is used to synthesise molecules of ATP from ADP and Pi

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3
Q

Define anabolic reactions

A

metabolic reactions where large molecules are synthesised from smaller molecules

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4
Q

Define catabolic reactions

A

Hydrolysis of larger molecules to smaller ones

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5
Q

Describe the structure of ATP

A

It is a phosphorylated molecule which consists of an adenosine nitrogenous base a ribose sugar and 3 phosphate molecules

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6
Q

What bonds join the phosphate molecules in atp

A

Phosphoanhydride bonds

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7
Q

Why is the stability of ATP useful in the molecule

A

It doesn’t break down easily when in solution but rather needs to be hydrolysed by enzymes.
This makes it easily transportable around the cell

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8
Q

Why is ATP produced and energy is not just released in the body

A

Cells can obtain the energy they need for a process in a small manageable way that will not cause damage or be wasteful

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9
Q

How is some of the waste energy released from the hydrolysis of ATP used?

A

Some heat is released may seem inefficient and wasteful; however, it helps keep the living organisms warm and enables enzyme-catalysed reactions to proceed near or at their optimum

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10
Q

Describe the chemical energy released from the hydrolysis of ATP

A

the first hydrolysis of ATP to ADP releases 30.5Kj/mol of energy and so does the second hydrolysis to AMP
The last hydrolysis to adenosine releases 13.8Kj/mol

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11
Q

define glycolysis

A

It is the first stage of respiration; a 10 stage metabolic pathway that converts glucose to pyruvate

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12
Q

Where does glycolysis occur

A

the cytoplasm

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13
Q

What co enzyme helps in glycolysis

A

NAD

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14
Q

What are the 3 steps in glycolysis

A

phosphorylation of glucose to hexose bisphosphate

splitting each hexose bisphosphate into 2 triose phosphate molecules

oxidation of the triose phosphate to pyruvate

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15
Q

Describe the role of NAD during glycolysis

A

NAD is a non-protein molecule that helps dehydrogenase molecules carry out oxidation reactions - NAD oxidises substrate molecules during glycolysis, the link reaction and krebs cycle

Reduced NAD carries the protons and electrons to the cristae of mitochondria to be used in oxidative phosphorylation

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16
Q

Describe how NAD is recycled during respiration

A

When reduced NAD gives up the protons and electrons that it had previously accepted and can be reused to oxidise more substrate and becomes reduced again

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17
Q

Describe the structure of NAD

A

it contains 2 ribose sugars an adenine group and 2 phosphate molecules with an oxygen between them

one of the ribose contains nicotinamide which is a pyrimidine that can accept 2 hydropgen atoms to become reduced NAD

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18
Q

Describe phosphorylation - the first step of glycolysis

A

One molecule of ATP is hydrolysed, and the released phosphoryl group is added to make hexose monophosphate, and this is repeated to make hexose bisphosphate

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19
Q

What stops the hexose sugar being phosphorylated from being transported out of the cell

A

the energy from the hydrolysed ATP molecules activates the hexose sugar and prevents it from being transported out the cell

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20
Q

Describe the splitting of the hexose bisphosphate molecule

A

it is split into 2 triose phosphate molecules

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21
Q

Describe the oxidation of the triose phosphate

A

the process is anaerobic

dehydrogenase enzymes aided by NAD remove hydrogens from the triose phosphate molecules

the 2 molecules accept the hydrogen atoms and become NADH

4 molecules of ATP are made for every triose phosphate molecules undergoing oxidation

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22
Q

if 4 ATP molecules are made in glycolysis, why is it that there is only a net production of 2 ATP per glucose molecule in ATP

A

This is because 2 ATP are spent in the phosphorylation of the glucose at the start

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23
Q

what are the products of glycolysis

A

2 molecules of ATP

2 molecules of NADH

2 molecules of pyruvate

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24
Q

What are the stages of aerobic respiration

A

glycolysis
the link reaction
the Krebs cycle
oxidative phosphorylation

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25
Q

how does the last stage of glycolysis differ under aerobic and anaerobic conditions

A

under aerobic conditions pyruvate is actively transported into the mitochondria for the link reaction

in the absence of oxygen pyruvate in the cytoplasm is converted to lactate or ethanol and the NADH are reoxidised so that glycolysis can continue to run

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26
Q

what is the purpose of the cofactor in the electron carrier proteins

A

the iron ion can accept and donate electrons

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27
Q

What can carrier proteins also be called

A

oxido-reductase enzymes

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28
Q

How are protons pumped from the matrix into the intermembrane space

A

using energy released from the electrons the electron carrier proteins can pump the protons from the mitochondrial matrix to the intermembrane space

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29
Q

describe the structure of ATP synthase

A

It is an enzyme that is large and protrudes from the inner membrane into the matrix and protons can pass through them

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30
Q

define decarboxylation

A

removing a carboxyl group from a molecule

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31
Q

define dehydrogenation

A

removal of hydrogen from a substrate molecule

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32
Q

Define substrate level phosphorylation

A

production of ATP from ADP and Pi during glycolysis and the Krebs cycle

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33
Q

What happens to pyruvate after glycolysis

A

it is transported across the outer and inner mitochondrial membranes via a pyruvate-H+ symport and into the matrix

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34
Q

Where does the link reaction occur

A

the mitochondrial matrix

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35
Q

Outline what occurs inthe Link reaction

A

The carboxyl group of the pyruvate is removed and is the origin of some of the CO2

the decarboxylation and dehydrogenation of pyruvate produces an acetyl group

the acetyl group combines with the coenzyme A to become acetyl CoA

NAD becomes reduced

36
Q

what is the equation that outlines what occurs in the link reaction

A

2 pyruvate + 2NAD +2CoA–> 2CO2 + 2NADH+2acetyl CoA

37
Q

Where does the Krebs cycle occur

A

the mitochondrial matrix

38
Q

Define the Krebs cycle

A

series of enzyme catalysed reaction that oxidise the acetate from the link reaction to 2 molecules of CO2 while conserving energy by reducing NAD and FAD

39
Q

what are the products of the link reaction per glucose molecule

A

2 NADH
2CO2
2acetyl CoA
0 ATP

40
Q

What are the products of the Krebs cycle

A

6 NADH
2 FADH
4 CO2
2ATP

41
Q

What can be found in the mitochondrial matrix

A

enzymes
NAD
FAD
oxaloacetate
Mitochondrial DNA and ribosomes

42
Q

how many steps are there in the Krebs cycle

A

6

43
Q

Describe the first 2 steps of the Krebs cycle

A

The acetyl group released by acetyl CoA combines with the 4 carbon compound oxaloacetate to form a six carbon citrate

Citrate is decarboxylated and dehydrogenated producing a five carbon compound one molecule of CO2 and one molecule of reduced NAD

44
Q

describe the 3rd and 4th steps of the Krebs cycle

A

the five carbon compound is further decarboxylated and dehydrogenated producing a four carbon compound one molecule of carbon dioxide and a molecule of reduced NAD

The four carbon compound combines temporarily with and is then released from CoA and substrate-level phosphorylation occurs producing one molecule of ATP

45
Q

describe the 5th and 6th steps of the Krebs cycle

A

The 4 carbon compound is dehydrogenated producing a different 4 carbon compound and a molecule of reduced FAD

rearrangement of the atoms in the 4 carbon molecule catalysed by an isomerase enzyme followed by further dehydrogenation regenerates a molecule of oxaloacetate

46
Q

at what steps in the Kreb cycle is FADH made

A

step 5

47
Q

At what step in the Kreb cycle is ATP made

A

step 4

48
Q

At what steps in the Kreb cycle is NADH made

A

step 2 3 6

49
Q

How many turns of the Krebs cycle are there per one glucose molecule

A

2

50
Q

what other substrates beside glucose can be respired aerobically

A

fatty acids
glycerol
amino acids

51
Q

how are fatty acids respires

A

they are broken down to many molecules of acetate that can enter the Krebs cycle via acetyl CoA

52
Q

How are glycerol’s respired

A

may be converted to pyruvate and enter the Krebs cycle via the link reaction

53
Q

How are amino acids respired

A

they may be deaminated and the rest of the molecule can enter the Krebs cycle directly or be changed to pyruvate or acetyl CoA

54
Q

Define chemiosmosis

A

flow of protons down their concentration gradient across a membrane through a channel associated with ATP synthase

55
Q

define oxidative phosphorylation

A

the formation of ATP using energy released in the electron transport chain and in the presence of oxygen it is the last stage of aerobic respiration

56
Q

What happens in the first stages of oxidative phosphorylation

A

NADH and FADH are reoxidised when they deliver the hydrogen atom to the electron transport chain

the hydrogen atoms released from the reduced co enzymes split into electrons and protons

The protons go into solution in the mitochondrial matrix

57
Q

Describe what occurs at the electron transport chain during oxidative phosphorylation

A

The electrons from the hydrogen atoms enter the electron carrier proteins and passes along the chain. The iron ion at its core can gain and lose electron so it can donate an electron to the next iron ion in the electron carrier

As electrons pass in the chain some of their energy is used to pump protons across the mitochondrial membrane into the intermembrane space

58
Q

Describe what happens once a proton gradient is created in oxidative phosphorylation

A

As protons accumulate in the intermembrane space a proton gradient forms across the membrane
Proton gradients cause chemiosmotic potential which is a source of potential energy and ATP is made using that energy

Protons diffuse through proton channels associated with ATP synthase enzymes and as protons diffuse down through their concentration gradient the flow of protons causes a conformational change in the ATP synthase that allows ADP +Pi to combine to form ATP

59
Q

What is the final electron acceptor in oxidative phosphorylation

A

oxygen is the final electron acceptor
It combines with the electrons coming from the electron transport chain and with protons diffusing down the ATP synthase channel forming water
4H+ +4e- +O2 –> 2H20

60
Q

What is chemiosmotic potential also known as

A

proton motive force

61
Q

What happens if there is an absence of oxygen

A

Oxygen acts as the final electron acceptor so protons diffusing through ATP synthase are unable to fuse with it and form water

The concentration of protons in the matrix increases reducing the proton gradient across the membrane so oxidative phosphorylation ceases

Reduced NAD and FAD are unable to unload their hydrogen to be reoxidises

62
Q

How can reduced NAD be oxidised again in the absence of oxygen

A

Fungi such as yeast use the ethanol pathway whereas mammals use the lactate pathway
both take place in the cytoplasm of cells

63
Q

Describe the ethanol fermentation pathway

A

Pyruvate + pyruvate decarboxylase –> ethanal + ethanol dehydrogenase (NADH ->NAD)–> Ethanol

each molecule of pyruvate is decarboxylated to produce ethanal catalysed by pyruvate decarboxylase

The ethanal accepts hydrogen atoms from NADH to produce ethanol catalysed by ethanol dehydrogenase

64
Q

Describe the lactate fermentation pathway

A

pyruvate + lactate dehydrogenase (NADH->NAD) –> lactate

Pyruvate accepts hydrogen atoms from the NADH and is reduced to lactate

65
Q

What happens to the NAD after the ethanol and lactate pathways

A

It becomes oxidised and can accept more hydrogens from triose phosphatye so glycolysis can continue

66
Q

What is the fate of lactate

A

It will either be converted to pyruvate and enter the krebs cycle via the link reaction (in the liver)

recycled to glucose and glycogen

67
Q

Why must lactate be removed

A

The pH of tissues could be lowered inhibiting enzyme activity

68
Q

What is the ATP yield of anaerobic respiration

A

1/15th of aerobic respiration

69
Q

Describe the process for calculating the rate of reproduction of yeast cells under aerobic and anaerobic conditions

A

4 beakers of differing volumes are filled with 50cm3 of cider
a drop of yeast suspension is added (shake yeast thoroughly first)
cover with cheesecloth and leave in a warm place for about a week

Swirl and drop some of the fluid on a haemocytometer slide and count the number of yeast cells in the corner and cetral squares

70
Q

escribe a haemocytometer

A

it has a dipped square central chamber about 0.1mm thick and grooves on it

71
Q

How would you use a haemocytometer

A

Breathe onto the underside of the slip to moisten it
slide the coverslip whilst pressing gently you will know its in the correct place when you see 6 rainbow patterns so the depth of the central chamber is 0.1mm

place the pipette tip at the entrance to the groove and allow liquid to enter and leave for 5 minutes
Place the haemocytometer on the microscope stage with 40x-100x magnification

count the cells in the 4 corner squares

72
Q

How do you calculate the number of yeast cells in a certain volume by using a haemocytometer

A

find the volume of the haemocytometer square for example if the depth is 0.1 and the lengths are 0.2 do 0.20.20.1= 0.004mm3
you counted 5 squares making the volume 5*0.004=0.02mm3
if you multiply the cells you counted by 50000 you will find the number of cells in 1cm3

73
Q

define respiratory substrate

A

An organic substance that can be oxidised using respiration releasing energy to make molecules of ATP

74
Q

What are some examples of respiratory substrates

A

carbohydrates
lipids
proteins

75
Q

Describe how carbohydrates can be used as respiratory substrates

A

disaccharides can be digested to monosaccharides for respiration

monosaccharides such as galactose and fructose can be changed by isomerase enzymes to glucose for respiration

76
Q

Describe how lipids can be used as respiratory substrates

A

triglycerids can be hydrolysed to glycerol which can be converted to triose phosphate and respired

fatty acids can be combined with coenzyme A and transported to the mitochondrial matrix and be broken down to 2 acetyl carbon groups attached to a CoA

This beta oxidation pathway generate NADH and FADH and then the carbons can enter th ekrebs cycle

77
Q

Describe how proteins can be used as respiratory substrates

A

Deamination of amino acids produces a keto acid which can enter the respiratory pathway as pyruvate, acetyl CoA or a krebs cycle acid such oxaloacetic acid

78
Q

What are the energy values of carbohydrates proteins and lipids

A

c - 15.8
l - 39.34
p- 17

79
Q

What is the respiratory quotient

A

co2 produced / co2 consumed

80
Q

What does a rq larger than 1 indicate

A

Some anaerobic respiration is taking place

81
Q

What are the rq values of glucose
fatty acids
amino acids

A

glucose = 1
fatty acid = 0.7
amino acid = 0.8

82
Q

What is a respirometer

A

Appararus used to measure the rate of respiration of living organisms

83
Q

Describe a respirometer

A

The living organism uses oxygen and exhales co2 in respiration which is absorbed by a sodium hydroxide solution which decreases pressure as the volume of oxygen is large in the tube with no organism
this moves the fluid in the capillary containing tube towards the organism

84
Q

how do you reset a respirometer

A

inject air using the syringe to get the liquid in the manometer to the starting position

85
Q

How do you calculate respiration rate using a respirometer

A

Find the volume of the cylinder and check how much it has moved and you can use it to measure volume of oxygen absorbed in the time taken

Volume is given by volume of a cylinder V = π r 2 h , where is the distance moved by the coloured liquid. The unit of rate of respiration is cm 3/min.

A level Biology (25 decks)

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