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OCR AS/A Level Biology Context > module 5.2.2 > Flashcards

module 5.2.2 Flashcards

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1
Q

what is respiration

A

the process whereby energy stored in complex organic molecules (carbohydrates, fats and proteins) is used to make ATP, occurring in living cells

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2
Q

what do all living organisms need to drive their biological processes in order to survive

A

energy

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3
Q

what are some examples of metabolic reactions that require energy

A

active transport, secretion, anabolism, replication of DNA and synthesis of organelles, endocytosis

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4
Q

what is active transport

A

moving ions and molecules across a membrane against a concentration gradient - requires ATP

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5
Q

what is secretion

A

large molecules made in some cells are exported by exocytosis

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6
Q

what is anabolism

A

synthesis of large molecules from smaller ones, e.g. proteins from amino acids, steroids into cholesterol and cellulose from β-glucose

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7
Q

what is endocytosis

A

bulk movement of large molecules into cells

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8
Q

describe the movement

A

movement of bacterial flagella, eukaryotic cilia and undulipodia, muscle contraction and microtubule motors that move organelles around inside cells

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9
Q

what is activation of chemicals

A

glucose is phosphorylated at the beginning of respiration so that it is more unstable and can be broken down to release energy

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10
Q

what is all chemical reactions that take place within living cells are known collectively as

A

metabolism

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11
Q

what does ATP stand for

A

adenine triphosphate

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12
Q

what does one molecule of ATP consist of

A

consists of adenine, ribose and three phosphates

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13
Q

what can ATP be hydrolysed to

A

ADP and Pi, releasing 30.6 kJ per mole

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14
Q

what processes use the ATP hydrolysis as an immediate source of energy

A

DNA replication and protein synthesis

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15
Q

why do ATP hydrolysis happen

A

so energy is immediately available to cells in small, manageable amounts that will not damage the cell (enzymes and proteins can denature or membranes could become too fluid if too much energy is released), so it’s easier to harness the energy and it will not be wasted

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16
Q

what is ATP known as

A

the universal energy carrier

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17
Q

what are some properties of ATP

A

small and soluble and has high energy bonds between phosphates which break down to release energy when required

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18
Q

is ATP a stable or unstable molecule

A

relatively stable

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19
Q

at any one time how much ATP do you have

A

5g

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20
Q

and about how much ATP is used up a day

A

36-60kg

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21
Q

what is the definition of anabolic reactions

A

building larger molecules from smaller molecules (condensation)

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22
Q

what is the definition of catabolic reactions

A

breaking larger molecules to form smaller molecules (hydrolysis).

 - catabolic reactions release energy that the building of ATP uses. The hydrolysis of ATP releases energy that other anabolic reactions could use
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23
Q

what is glycolysis

A

occurs in the cytoplasm which can take place in aerobic or anaerobic conditions. glucose is broken down to two molecules of pyruvate

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24
Q

what is the link reaction

A

occurs in the matrix of the mitochondria. pyruvate is dehydrogenated and decarboxylated `and converted to acetate

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25
Q

what is the Kreb cycle

A

occurs in the matrix of the mitochondria. acetate is dehydrogenated and decarboxylated

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26
Q

what is oxidative phosphorylation

A

occurs on the folded inner membrane (cristae) of mitochondria. this is where ADP is phosphorylated to ATP

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27
Q

describe what a coenzyme does

A
  • are needed to help enzymes carry out oxidation reactions, where hydrogen atoms are removed from substrate molecules in respiration
  • the hydrogen atoms are combined with coenzymes, so that they can be carried and can later be split into hydrogen ions and electrons, to the inner mitochondrial membranes where they will be involved in oxidative phosphorylation
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28
Q

what is nicotinamide adenine dinucleotide

A

an organic, non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions

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29
Q

what does NAD stand for

A

nicotinamide adenine dinucleotide

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30
Q

what is NAD made up of

A
  • two linked nucleotides - nicotinamide (Vitamin B3), 5-carbon sugar ribose, adenine and 2 phosphate (phosphoryl) groups
  • the nicotinamide ring can accept hydrogen atoms which can later be split into a hydrogen ion and an electron
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31
Q

what happens when NAD accepts 2 hydrogen atoms

A

it is reduced

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32
Q

what happens to the NAD for it to be oxidised

A

loss of electrons/loss of hydrogen

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33
Q

when during respiration does NAD operate

A

in glycolysis, the link reaction, Krebs cycle and during the anaerobic ethanol and lactate pathways

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34
Q

what is coenzyme A made up of

A

from pantothenic acid (a B-group vitamin), adenosine (ribose and adenine), 3 phosphate (phosphyl) groups and cysteine (amino acid)

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35
Q

what is the function of coenzyme A

A

to carry ethanoate (acetate) groups, made from pyruvate during the link reaction, onto Krebs cycle and can also carry acetate groups that have been made from fatty acids or from some amino acids on to the Krebs cycle

36
Q

what does FAD stand for

A

flavin adenine dinucleotide

37
Q

when FAD accepts 2 hydrogen atoms with their electrons, what happens

A

it becomes reduced

38
Q

what is the function of FAD

A

operates during the Krebs cycle. It then acts as a reducing agent by donating electrons at the inner mitochondrial membrane during oxidative phosphorylation

39
Q

what happens in the matrix

A
  • where the link reaction and Krebs cycle takes place
  • it contains enzymes that catalyse the stages of these reactions, coenzyme NAD, Oxaloacetate (a 4-carbon compound that accepts acetate from the link reaction), mitochondrial DNA (some of which codes for mitochondrial enzymes and other proteins), and mitochondrial ribosomes where these proteins are assembled
40
Q

what happens at the outer membrane

A

contains proteins, some of which form channels or carriers that allow the passage of molecules such as pyruvate, or other proteins such as enzymes

41
Q

what happens at the inner membrane

A
  • has a different lipid composition from the outer membrane and is impermeable to most small ions, including hydrogen ions (protons) meaning protons accumulate in the intermembrane space, building a proton gradient - a source of potential energy
  • it’s folded into cristae to give a large surface area and embedded in it is many electron carriers and ATP synthase
42
Q

what happens in the electron transport chain

A
  • each electron carrier is an enzyme, each associated with a cofactor. the cofactors can accept and donate electrons because the iron ions can become reduced (to Fe2+) by accepting an electron and oxidised (to Fe3+) by donating an electron to the next electron carrier. they are oxidoreductase enzymes as they are involved in oxidation and reduction reactions
  • some of the electron carriers also have a coenzyme that pumps (using the energy released from the passage of electrons) protons from the matrix to the intermembrane space. protons flow down a proton gradient, through the ATP synthase enzymes, from the matrix into the intermembrane space - this is called chemiosmosis. the force of this flow drives the rotation of part of the enzyme and allows ADP and Pi to be joined to make ATP

The ATP synthase enzymes are large and protrude from the inner membrane into the matrix, are also known as stalked particles, and allow protons to pass through them.

More active organisms have more mitochondria, larger mitochondria, and larger cristae

43
Q

what happens in glycolysis

A
  • one molecule of ATP is hydrolysed and the phosphate group produced is used to convert glucose into glucose-6-phosphate. the energy from the hydrolysed ATP molecule activates the hexose sugar and prevents it from being transported out of the cell
  • glucose 6-phosphate is rearranged, using the enzyme isomerase, into fructose 6-phosphate
  • phosphorylation via hydrolysis of a molecule of ATP occurs again forming hexose 1,6-bisphosphate
    -the hexose 1,6-bisphosphate splits into two molecules of triose phosphate.
  • each triose phosphate is dehydrogenated, removing hydrogen atoms using dehydrogenase enzymes
  • the coenzyme NAD accepts the hydrogen atoms and becomes reduced NAD
  • two molecules of ATP are formed, via substrate-level phosphorylation (the formation of ATP directly during glycolysis and the Krebs cycle only)
  • the triose phosphate molecules are converted to pyruvate, which is actively transported to the mitochondrial matrix. in the process, another two molecules of ADP are phosphorylated to make two molecules of ATP
44
Q

during aerobic respiration in animals, what is the triose phosphate molecules converted into

A

pyruvate

45
Q

how is pyruvate produced during glycolysis transported

A

across the inner and outer membrane to the mitochondrial matrix where the link reaction takes place

46
Q

what is decarboxylation

A

the removal of a carboxyl group

47
Q

what is dehydrogenation

A

the removal of hydrogen atoms

48
Q

what happens during the link reaction

A
  • the pyruvate molecule is decarboxylated by the enzyme pyruvate decarboxylase, removing a carboxyl group which eventually becomes carbon dioxide.
  • the pyruvate molecule is also dehydrogenated by the enzyme pyruvate dehydrogenase, removing hydrogen atoms, forming acetate
  • the hydrogen atoms are accepted by the coenzyme NAD, becoming reduced NAD
  • the acetate combines with coenzyme A forming acetyl CoA
    2 pyruvate + 2NAD+ + 2CoA → 2CO2 + 2NADH + 2 acetyl CoA
49
Q

what is coenzyme A’s role in the link reaction

A
  • coenzyme A (CoA) accepts acetate to become acetyl coenzyme A. the function of CoA is to carry acetate to the Krebs cycle
50
Q

what happens during the kreb cycle

A
  • the acetate is offloaded from coenzyme A and joins with oxaloacetate (4C), to form citrate (6C)
  • citrate is decarboxylated and dehydrogenated forming a 5-carbon compound. the pair of hydrogen atoms is accepted by the coenzyme NAD (hydrogen acceptor), which becomes reduced NAD
  • the 4-carbon compound is decarboxylated and dehydrogenated forming a 4-carbon compound and another molecule of reduced NAD
  • the 4-carbon compound is changed into another 4-carbon compound. during this reaction a molecule of ADP is phosphorylated to produce a molecule of ATP - substrate-level phosphorylation
  • the second 4-carbon compound is changed into another 4-carbon compound. it’s dehydrogenated and the coenzyme FAD (hydrogen acceptor) accepts the hydrogen atoms, and becomes reduced FAD
  • the third 4-carbon compound is further dehydrogenated and regenerates oxaloacetate and forms another molecule of reduced NAD
51
Q

what happens in oxidative phosphorylation

A
  • NADH is reoxidised to form NAD+ and 2 hydrogen atoms, aided by the enzyme NADH dehydrogenase which is attached to the first electron carrier. the hydrogen atoms split into protons and electrons
  • the electrons are passed along electron carriers in the electron transport chain and lose energy by doing this
  • the energy that was lost in the electron transport chain is used to pump protons into the intermembrane space creating a proton gradient– the protons will want to move back into the matrix from a high concentration to a low concentration
  • the H+ ions cannot diffuse through the lipid part of the membrane so they diffuse through protein channels that are associated with ATP synthase, which is linked to the synthesis of ATP. the flow of protons is chemiosmosis
  • the flow of protons through the protein channels creates a proton motive force which drives the rotation of the ATP synthase enzyme attached to the protein channel. the rotation causes the phosphorylation of ADP to make ATP
  • the electrons are passed from the last electron carrier in the chain to oxygen, which is the final electron acceptor. hydrogen ions also join forming water
52
Q

describe the theorectical yield from respiration

A

the 10 molecules of NAD can theoretically produce 26 molecules of ATP during oxidative phosphorylation (each NAD molecule can make 2.6 molecules of ATP). together with the 4 ATP made during glycolysis and the Krebs cycle, the total yield of ATP molecules, per molecule of glucose respired, should be 30. however this is rarely achieved for the following reasons:
—– some protons leak across the mitochondrial membrane, reducing the number of protons to generate the proton motive force.
—– some ATP produced is used to actively transport pyruvate into the mitochondria
—– some ATP is used for the shuttle to bring hydrogen from reduced NAD made during glycolysis, in the cytoplasm, into the mitochondria

53
Q

what is anaerobic respiration

A

the process where ATP is produced by substrate-level phosphorylation during glycolysis in the absence of oxygen, in the cytoplasm of eukaryotic cells

54
Q

as anaerobic respiration occurs in the absence of oxygen, what cannot happen and what does this lead to

A
  • the electron transport chain cannot happen so the link reaction, Krebs cycle and oxidative phosphorylation cannot happen
  • therefore only glycolysis can happen and only ATP can be produced via glycolysis. the reduced NAD has to be reoxidised so that it can keep accepting hydrogen atoms in glycolysis
55
Q

what are the 2 ways that NAD can be reoxidised

A

lactate fermentation and alcohol fermentation

56
Q

what happens in lactate fermentation(mammals)

A
  • reduced NAD is oxidised to NAD and the NAD formed goes back into glycolysis
  • pyruvate accepts the hydrogen atoms and is reduced to lactate with the help of the enzyme lactate dehydrogenase
57
Q

where does lactate fermentation occur

A
  • occurs in mammalian muscle tissue during vigorous activity
  • the lactate is carried in the blood away from muscles, to the liver
58
Q

what happens in alcohol fermentation (yeast)

A
  • pyruvate is decarboxylated to ethanal with the help of the enzyme pyruvate decarboxylase, releasing CO2 (pyruvate has the coenzyme thiamine diphosphate),
  • ethanal accepts hydrogen atoms from reduced NAD, becoming reduced itself forming ethanol, with the help of the enzyme ethanol dehydrogenase
  • the NAD formed goes back into glycolysis
59
Q

yeast is a facultative anaerobe, what does this mean

A

it can live without oxygen although it is killed when the concentration of ethanol builds up to around 15%

60
Q

what is one similarity between ethanol and lactate fermentation

A

neither of them produce ATP

61
Q

is glucose partially or fully broken down by glycolysis

A

partially

62
Q

what is the fraction of ATP produced in anaerobic respiration in comparison to aerobic respiration

A

1/15

63
Q

how much mitochondria do fast twitch muscles have

A

a few/ none

64
Q

what do fast twitch muscles use to power their short duration contractions

A

they use glycolysis

65
Q

what are some properties of fast twitch muscles

A
  • they fatigue easily
  • appear pale in colour due to lack of electron transport proteins
  • they lack myoglobin - a protein that stores O2 in some muscles
66
Q

what colour are slow twitch muscles

A

dark red

67
Q

what are some properties of slow twitch muscles

A
  • they contain many mitochondria
  • are slow to fatigue
  • they operate aerobically for endurance exercise
68
Q

how can rate of respiration be measured

A

by rate of CO2 consumption
- as CO2 dissolves in the medium it lowers pH, which can be measured using a pH meter

69
Q

what is a respiratory substrate

A

an organic substance that can be used for respiration

70
Q

what does more protons mean

A

more ATP produced as most ATP is formed from the flow of protons through channel proteins during chemiosmosis

71
Q

what does a molecule of respiratory substrate having more hydrogen atoms result in

A

more ATP that can be generated when that substrate is respired

72
Q

if more H2 is need for the respiratory substrate, what is also needed

A

more O2 is needed to respire the substrate

73
Q

what is the general formula for carbohydrate respiratory substrates

A

Cn(H20)n

74
Q

what is the chief carbohydrate respiratory substrate and what does it do

A
  • glucose
  • some mammalian cells (e.g. brain cells and red blood cells) can only use glucose for respiration
75
Q

how do plants and animals store glucose

A
  • starch
  • glycogen
76
Q

what is the theoretical max energy yield for glucose

A

-2870 kJ mol-1

77
Q

how much energy is required to produce 1 mol ATP

A

30.6 kJ mol-1

78
Q

what is the remaining energy from glucose used for

A

heat – maintain suitable body temperature, allowing enzyme-controlled reactions to proceed

79
Q

what are lipid respiratory substrate mostly used

A

many tissues - mostly muscles

80
Q

what are triglycerides hydrolysed by and into

A

by lipase
fatty acids and glycerol

81
Q

what can be respired from the following: glycerol and fatty acids

A

glycerol can be respired but not fatty acids

82
Q

what does the fatty acids do

A

combine with CoA and the fatty acid-CoA complex transported into the mitochondrial matrix – broken down(by β-oxidation pathway) into 2-carbon acetyl groups that are attached to CoA and forms reduced NAD and FAD

83
Q

what are fatty acids

A

are long-chained hydrocarbons

84
Q

protein respiratory substrate

A

deamination involves the removal of the amine group and its conversion to urea – the rest of the molecule is changed into glycogen or fat = stored and later respired to release energy

85
Q

what does fasting, starvation and prolonged exercise cause (protein)

A

protein from muscle can be hydrolysed to amino acids, which can be respired
some can be converted to pyruvate, or to acetate, and be carried to the Krebs cycle – some may enter the Krebs cycle directly

86
Q

what causes proteins to release more energy than the equivalent masses of carbohydrates

A

the number of hydrogen atoms per mole accepted by NAD and then used in oxidative phosphorylation is slightly more than the number of hydrogen atoms per mole of glucose

87
Q

how do you use a respirometer/ devise an experiment

A
  • in the boiling tube the volume of oxygen decreases due to respiration. the volume of carbon dioxide also decreases as the soda lime absorbs it
  • overall, the volume of the boiling tube decrease, causing an air pressure decrease. this causes an air pressure gradient between the boiling tube and the capillary tube, and so the drop of liquid moves towards the boiling tube, as it has a lower air pressure
  • ensure that the apparatus is equilibrated – use syringe to adjust the position of the fluid in the manometer
  • record the position of the liquid and leave the apparatus for a certain length of time to allow time for respiration, then record the new position of the liquid. repeat and take the mean. if the diameter of the capillary tube is known, use the formula πr2lto find the volume of oxygen uptake to give the rate
  • the second boiling tube is a control – air pressure stays the same so no changes occur. there is a closed tap to ensure no air can enter or leave during the experiment
  • if measuring respiration rates in photosynthetic organisms, wrap the tubes in foil or black paper to exclude light and prevent photosynthesis

OCR AS/A Level Biology Context (24 decks)

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