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Biology Module 5 > Respiration > Flashcards

Respiration Flashcards

1
Q

Why do living organisms need to respire

A

organisms need to be able to respire so they can release energy stored in respiratory substrates (organic molecules) such as glucose which can then be used to make ATP from ADP and Pi this is then used to drive metabolic processes

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2
Q

Why do living organisms need energy

A

organisms need energy to make ATP which is used to drive biological processes such as…

  • endocytosis
  • exocytosis
  • active transport
  • DNA replication
  • cell division
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3
Q

What is respiration

A

Respiration is the process that occurs in all living cells and releases the energy stored in organic molecules such as glucose
- energy is used to synthesis molecules of ATP from ADP and Pi (inorganic phosphate)

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4
Q

Describe how ATP is made from basic hydrolysis and condensation reactions

A
  • ATP is stable therefore it does not readily break down but is hydrolysed by enzyme catalysis
  • when in solution it can be moved from place to place in the cell
  • ATP is hydrolysed into ADP and Pi, this releases energy for the use by cells to do work as well as heat which is used to keep the organism warm and allow enzymes to work at their optimum temperature and maximum rate
  • ATP is made during a condensation reaction, from ADP and Pi, this happens when energy is released from an organic substrate during respiration
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5
Q

What is ATP referred to as

A

ATP is the universal energy currency

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6
Q

DRAW OUT ATP

A

DRAW IT

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7
Q

Describe where glycolysis happens and what conditions it happens in

A
  • cytoplasm

- anaerobic conditions - this means it can happen in anaerobic respiration

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8
Q

What are the 4 stages of respiration

A
  • Glycolysis
  • the links reactions
  • the Krebs cycle
  • oxidative phosphorylation - this is the electron transport chain and chemiosmosis
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9
Q

Describe the process of glycolysis

A
  • Glycolysis is a series of reaction that extract energy from glucose by splitting it into pyruvate, these reactions happens very quickly but only a small amount of ATP is produced therefore it is inefficient.
    1. Glucose is converted to glucose phosphate, this requires the use of an ATP molecule which is reduced to ADP, in order to release energy.
    2. Glucose phosphate is then converted to fructose phosphate which is then converted to fructose diphosphate, this requires ATP to be hydrolysed to ADP and Pi.
    3. Fructose diphosphate a six-carbon compound which contains two phosphate groups, these are from the two ATP molecules that have been hydrolysed.
    4. Fructose diphosphate splits to form two three carbon compounds as it is unstable, these are a 3 carbon compound and and Glyceraldehyde phosphate (GALP). These two molecules exist in equilibrium, but the equilibrium lies towards GALP therefore all the triose phosphate is converted to GALP, meaning there are two molecules of GALP.
    5. Each GALP molecule then is converted to pyruvate in an oxidation reaction, therefore producing two pyruvate molecules, a three-carbon compound. This is an oxidation reaction as it involves the removal of hydrogen atoms from substrate molecules.
    6. To do this GALP undergoes dehydrogenation, this is when two hydrogen atoms are removed from GALP and are picked up by hydrogen acceptors called NAD, this is catalysed by the enzyme dehydrogenase and produces reduced NAD.
    7. GALP converting to pyruvate also releases enough energy to combine ADP and Pi producing ATP. This is substrate level phosphorylation, as it results in the formation of ATP by the direct transfer of a phosphate group to ADP from another phosphorylated compound. Substrate level phosphorylation occurs twice producing two molecules of ATP per GALP oxidised therefore four are produced overall.
    8. In aerobic conditions, the pyruvate molecules are actively transported into the mitochondrial matrix for the link cycle
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10
Q

Why is glucose converted to glucose phosphate during glycolysis

A
  • Glucose is converted to glucose phosphate, because glucose can easily get in and out of the cell therefore by phosphorylating it, it means it cannot exit the cell. -
  • Phosphorylation also happens to provide more energy and make glucose more reactive.
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11
Q

What are the products of glycolysis

A

The products of glycolysis are ..

  • two molecules of ATP, four are made but two are used during phosphorylation,
  • two molecules of reduced NAD
  • two molecules of pyruvate
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12
Q

What happens to the reduced NAD produced in the glycolysis

A

Reduced NAD needs to be converted back to NAD in order to keep glycolysis running therefore the NAD can pass its electrons into the electron transport chain regenerating NAD therefore allowing glycolysis to continue.

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13
Q

Describe NAD

A
  • Non protein molecule that helps dehydrogenase enzymes carry out oxidation reactions
  • NAD oxidises substrate molecules during glycolysis, links reaction and the Krebs cycle
  • NAD synthesised in living cells from nicotinamide, ribose, and adenine and to phosphoryl groups
  • nicotainamide ring can accept 2 hydrogen atoms becoming reduced NAD
  • reduced NAD carries the protons and electrons to mitochondrial matrix and cristae
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14
Q

What is the cristae

A

inner highly folded mitochondrial matrix

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15
Q

What is the mitochondrial matrix

A

fluid filled inner part of the mitochondria

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16
Q

Describe the links reaction

A
  1. Pyruvate undergoes decarboxylation which is catalysed by the enzyme decarboxylase and produces carbon dioxide, it is now a two-carbon compound as one of the carbons have been lost.
  2. undergoes dehydrogenation using the enzyme dehydrogenase and produces two hydrogen atoms which are picked up by the coenzyme NAD which causes it to become reduced.
  3. This produces an acetyl group which combines with co-enzyme A forming acetyl coenzyme A, a two-carbon compound.
  4. The acetyl coenzyme A is transported to the Krebs cycle where the coenzyme A breaks away from it and goes back to the links cycle and the acteyl group joins with oxaloacetate(4C) forming a 6 carbon compound
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17
Q

Describe the Krebs cycle

A
  1. The acetyl group goes into the Krebs cycle while co-enzyme A goes back to the link cycle. The acetyl group combines with oxalo-acetic, a four-carbon compound, to form citric acid, a six-carbon compound.
  2. Citric acid undergoes decarboxylation catalysed by decarboxylase and produces carbon dioxide, this turns it to a five-carbon compound. It also undergoes dehydrogenation catalysed by dehydrogenase, forming reduced NAD.
  3. The five-carbon compound then goes then undergoes decarboxylation catalysed by decarboxylase turning it to a four-carbon compound called succinate. 4. At this stage enough energy is released for substrate level phosphorylation to happen forming one molecule of ATP from ADP and Pi.
  4. Dehydrogenation also happens and this is catalysed by dehydrogenase but the hydrogen atoms go to the coenzyme FAD which forms reduced FAD, this skips the first stage of the electron transport system.
  5. Succinate is oxidised forming malate, a four-carbon compound. This undergoes dehydrogenation and forms reduced NAD, this is the oxidation of malate and converts it to oxalo-acetic acid therefore starting the cycle again.
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18
Q

What conditions does the links reaction happen in

A

The next stage of respiration is called the links cycle, this occurs in aerobic conditions in the mitochondrial matrix and happens twice as two pyruvate molecules are produced.

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19
Q

What are the products of the Krebs cycle

A

The Krebs cycle produces…

  • six molecules of reduced NAD
  • two molecules of reduced FAD
  • four molecules of carbon dioxide
  • two molecules of ATP.
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20
Q

What conditions does the Krebs cycle happen in

A

The next stage is the Krebs cycle, this occurs in the mitochondrial matrix

  • in aerobic conditions
  • happens twice as two acetyl coenzyme A are formed due to two pyruvate molecules being formed.
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21
Q

For every molecule of glucose…..

A

there are two turns of the krebs cycle

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22
Q

How is pryuvate transported into the mitochondrial matrix

A

it is transported across the outer and inner mitochondrial membrane by a specific pyruvate-H+ symport
- this is a transport protein that transports two ions or molecules in the same direction and into the matrix

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23
Q

What other substrates other than glucose can be used

A
  • fatty acids are broken down to many molecules of acetate that enter the Krebs cycle via acetyl CoA
  • glycerol may be converted to pyruvate and enter the Krebs cycle via the link reaction
  • amino acids may be deaminated and the rest of the molecule can enter the Krebs cycle directly or be changed to pyruvate of acetyl CoA
24
Q

what is substrate-level phosphorylation

A

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

25
Q

what happens in the absence of oxygen

A
  • only the glycolysis cycle can take place as this takes place in anaerobic conditions whereas the others take place in aerobic conditions
  • pyruvate is converted, in the cytoplasm, to lactate or ethanol
  • reduced NAD molecules are re-oxidised so that glycolysis can continue to run generating two molecules of ATP for every glucose metabolised
26
Q

what is chemiosmosis

A
  • flow of protons down their concentration gradient across a membrane though a channel associated with ATP synthase
27
Q

What is oxidative phosphorylation

A
  • formation of ATP using energy released in the electron transport chain and in the presence of oxygen, last stage in aerobic respiration
28
Q

where does oxidative phosphorylation take place

A
  • mitochondrial matrix
  • aerobic conditions
  • it involves electron carrier proteins, which have iron ions at their core, embedded in the cristae
  • folded cristae gives large surface area fro the electron carrier proteins and the ATP synthase enzymes
29
Q

Describe the electron transport chain

A
  • The iron ions are reduced by the electrons but they want to become re-oxidised therefore they pass the electrons onto the next protein to become re-oxidised, this means that the electron chain is a series of redox reactions.
  • The hydrogen from the Krebs cycle enter the electron transfer chain, they reduce NAD which then releases the hydrogen atoms to return to NAD, this causes ADP to combine with Pi to form ATP.
  • The hydrogen atoms are then passed on to FAD to become reduced FAD. The hydrogens then split forming a proton and electron, and this releases enough energy to make ADP into ATP.
  • The electrons are passed on to cytochrome which now has a 2- charge, it wants to get rid of the electrons and return to cytochrome with no charge therefore it passes the two electrons on to cytochrome oxidase, this releases energy which converts ADP to ATP.
  • Cytochrome oxidase loses two electrons which it gives to oxygen, the oxygen then binds with two hydrogens, from the reduced FAD, and forms water.
30
Q

Describe the electron transport chain as it does in the book

A
  • reduced NAD and reduced FAD are reoxidised when they deliver their hydrogen atoms to the electron transport chain
  • the hydrogen atoms released from the reduced coenzymes split into protons and electrons
  • the protons go into solution in the mitochondrial matrix
31
Q

What’s the energy from the electron transport chain used for

A
  • some of the energy is used to pump protons across the inner mitochondrial membrane into the intermembrane space
32
Q

Describe the proton gradient and chemiosmosis

A
  • The energy created is used to pump protons across the inner mitochondrial membrane to the intermembrane space.
  • This creates a concentration gradient as the concentration of protons in the intermembrane space is greater than the concentration of protons in the inner mitochondrial membrane.
  • The proton gradient generates a chemiosmotic potential, this energy is what ATP is made from.
  • The proton gradient causes the protons to diffuse from a high concentration to a low concentration down the concentration gradient but they have to go through protein channels associated with ATP synthase enzymes, this is because they cannot diffuse through the lipid bilayer as its impermeable to protons.
  • As the protons flow through the protein channels, this is known as chemiosmosis, it causes a conformational change in the ATP synthase enzymes which allows ADP and Pi to combine forming ATP.
33
Q

How do bacteria use ATP synthase

A
  • they use ATP synthase but in reverse to power the movement of their flagella, they use ATP to produce a proton gradient and the energy associated with that gradient causes a flow of protons that rotates the flagella
34
Q

How much ATP is made during oxidative phosphorylation

A 
Reduced NAD
glycolysis = 2
the links reaction = 2
the krebs cycle = 6
Reduced FAD
glycolysis = 0
links reaction = 0
the krebs cycle = 2

the protons and electrons from 10 molecules of reduced NAD can theoretically produced 25 molecules of ATP, the protons and electrons from 2 molecules of reduced FAD can produced 3 molecule of ATP
therefore one molecule of glucose in oxidative phosphorylation can produced 28 molecules of ATP

35
Q

Amount of ATP per stage created

A 
glycolysis = 2
links reaction = 0 
krebs cycle = 2
oxidative phosphorylation = 28 
total = 32
36
Q

Why wont the amount of ATP created be the same

A
  • some ATP is used to actively transport pyruvate into the mitochondria
  • some ATP is used in a shuttle system that transports reduced NAD made during glycolysis into mitochondria
  • some protons may leak out through the outer mitochondrial membrane
37
Q

Describe the structure of the mitochondria

A
  • rod shaped, thread like or spherical
  • inner and outer phospholipid membrane making up the envelope
    outer is smooth and the inner membrane is folded into cristae giving it a large surface area
  • embedded in the inner membrane are proteins that transport electrons and protein channels associated with ATP synthase enzymes allowing protons to diffuse through them
  • between inner and outer there is an intermembrane space
  • mitochondrial membrane - enclosed by inner membrane, semi-rigid and gel like, contains ribosomes, looped mitochondrial DNA and enzymes
38
Q

how the structure of mitochondria enables them to carry out their functions

A
  • enzymes catalysing the stages of respiration
  • molecules of the coenzymes NAD and FAD
  • oxaloacetate - 4 carbon compound that accepts the acetyl group from the links reaction
  • mitochondrial DNA - some of which codes for mitochondria enzymes and other proteins
  • mitochondrial ribosomes - similar structurally to prokaryote ribosomes where these proteins are assembled
39
Q

Describe the outer membrane

A
  • phospholipid
  • contains proteins which form channels or carriers that allow the passage of molecules such as pyruvate into the mitochondria
40
Q

describe the inner membrane

A
  • lipid bilayer is less permeable to small ions such as hydrogen ions than the outer membrane
  • folds creating cristae - large surface area for the electron transport chain and ATP synthase enzymes
  • electron transport chain
41
Q

describe the intermembrane space

A
  • between outer and inner layers
  • inner membrane close contact with the mitochondrial matrix so the molecules of reduced NAD and FAD can easily transport hydrogens to the electron transport chain
42
Q

Describe ATP synthase

A
  • large
  • protrude from the inner membrane into the matrix
  • protons can pass through them
43
Q

Describe respiration in the absence of oxygen

A
  1. oxygen cannot act as the final electron acceptor at the end of oxidative phosphorylation, protons diffusing through the channels associated with ATP synthase cannot combine with electrons and oxygen to form water
  2. the concentration of protons increases in the matrix and reduces the proton gradient across the inner mitochondrial membrane
  3. oxidative phosphorylation ceases
  4. reduced NAD and reduced FAD are not able to unload their hydrogen atoms and cannot be reoxidised
  5. the krebs cycle stops and so does the link reaction
    - glycolysis can take place but the reduced NAD generated during the oxidation of triose phosphate to pyruvate has to be reoxidised so that glycolysis can continue, these reduced coenzyme molecules cannot be reoxidised at the electron transport chain so another metabolic pathway must reoxidised them
44
Q

How do they reoxidise reduced NAD

A
  • fungi such as yeast and plants use ethanol fermentation

- mammals use lactate fermentation

45
Q

Draw the ethanol fermentation pathway

A

draw it

46
Q

describe the ethanol fermentation pathway

A
  • each molecule of pyruvate produced during glycolysis is decarboxylated and converted to ethanol, this stage in the pathway is catalysed by pyruvate decarboxylase which has a coenzyme thiamine diphosphate bound to it
  • the ethanal accepts hydrogen atoms from reduced NAD becoming reduced to ethanol, the enzyme ethanol dehydrogenase catalyses the reaction
  • in the process the reduced NAD is re-oxidised and made available to accept more hydrogen atoms from triose phosphate thus allowing glycolysis to continue
47
Q

Draw the lactate fermentation pathway

A

DRAW IT

48
Q

Describe the lactate fermentation pathway

A
  • pyruvate produced from glycolysis accepts hydrogen atoms from the reduced NAD also made during glycolysis, the enzyme lactate dehydrogenase catalyses the reaction
  • pyruvate is reduced to lactate, the reduced NAD becomes reoxidised
  • the reoxidised NAD can accept more hydrogen atoms from triose phosphate during glycolysis adn glycolysis can continue to produce enough ATP to sustain muscle contraction for a short period
49
Q

describe ATP yield from anaerobic respiration

A
  • neither ethanol fermentation nor lactate fermentation produces an ATP , however it does allow glycolysis to continue and the net gain of 2 molecules of ATP per molecule of glucose is still obtained
  • because the glucose is only partly broken down many more molecules can undergo glycolysis per minute therefore the overall yield of ATP is quite large, however each molecule of glucose the yield of ATP via anaerobic respiration is about 1/15 of that produced in aerobic respiration
50
Q

describe the fate of lactate

A

lactate produced in the muscle tissue is carried away from the muscles in the blood to the liver, when more oxygen is avaliable the lactate may be either

  • converted to pyruvate which may enter the krebs cycle via the links reaction
  • recycled to glucose and glycogen
  • if lactate was not removed then pH would be lowered and this would stop the action of enzymes involved in glycolysis and muscle contraction
51
Q

what is a respiratory substrate

A
  • an organic substance that can be oxidised by respiration releasing energy to make molecules of ATP
52
Q

how are carbohydrates good at respiratory substrate

A
  • animals and some bacteria store carbohydrate as glycogen which can be hydrolysed to glucose for respiration, plant cells store carbohydrates as starch and this can be hydrolysed to glucose for respiration
  • disaccharides can be digested to monosaccharides for respiration
  • monosaccharides such as fructose and galactose can be changed by isomerase enzymes to glucose for respiration
53
Q

Lipids as respiratory substrates

A
  • important for a number of types of tissues including muscle,
  • triglycerides are hydrolysed by lipase to glycerol and fatty acids, glycerol can then be converted to triose phosphate and respired
  • fatty acids are long chain hydrocarbons, have many carbon atoms, hydrogen atoms and few oxygen atoms so they are a source of many protons for oxidative phosphorylation and so fats produce much more ATP than an equivalent mass of carbohydrate
    1. with the aid of some energy from the hydrolysis of one molecule of ATP to AMP each fatty acid is combined with coenzyme A
    2. the fatty acid-CoA complex is transported into the mitochondiral matrix where it is broken down into two carbon acetyl groups eahc attached to CoA
    3. this beta-oxidation pathway generates reduced NAD and reduced FAD
    4. the acetyl groups are released from CoA and enter the krebs cycle by combining with the four carbon oxaloactetate
  • for every acetyl group oxidised in the krebs cycle three molecules of reduced NAD, one molecule of reduced FAD and one molecule of ATP by substrate level phosphorylation are made
54
Q

describe how proteins are used

A
  • excess amino acids released after the digestion of proteins are deaminated in the liver, deamination of amino acid involves removal of the amino group and its conversion to urea that is removed via the kidney
  • the rest of the amino acid molecule a keto acid enter the respiratory pathway as pyruvate, acetyl CoA or a krebs cycle acid such as oxaloacetic acid
  • during starvation when insufficient glucose or lipid is available for respiration, protein from muscle can be hydrolysed to amino acids which are then respired, these amino acids may be converted to pyruvate or acetate and enter the krebs cycle
55
Q

mean value of energy for
A) Carbohydrate
B) Lipid
C) Protein

A 
A = 15.8 KJ g-1
B = 39.4
C = 17.0
56
Q

what is the respiratory quotient

A
  • CO2 produced/ O2 consumed
  • if the RQ value is greater than 1 this indicates that some anaerobic respiration is taking place because it shows more carbon dioxide is being produced than oxygen consumed

Biology Module 5 (12 decks)

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