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A-Level Biology > M5, C18 Respiration > Flashcards

M5, C18 Respiration Flashcards

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1
Q

define respiration

A

the process by which organisms use the energy stored in complex molecules to generate ATP

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2
Q

give some examples of what ATP is used for

A 
active transport
movement of muscles
DNA replication
exo/endocytosis
synthesis of large molecules
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3
Q

how much energy is released when you hydrolyse ATP to ADP

A

30.6 kJmol^-1

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4
Q

what is the structure of ATP

A

3 phosphates
ribose sugar
adenine base

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5
Q

what is the word equation and symbol equation for aerobic respiration

A

glucose + oxygen -> carbon dioxide + water + 36ATP

look up symbol equation

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6
Q

what is the word and symbol equation for anaerobic respiration in plants

A

glucose -> ethanol + carbon dioxide + 2ATP

look up symbol

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7
Q

what is the word and symbol equation for anaerobic respiration in animals

A

glucose -> lactate + 2ATP

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8
Q

Glycolysis steps

A

1) heroes sugar is phosphorylated By two molecules of ATP. Hexose biphosphate is formed which is less stable. It will also prevent diffusion out of the cell.
2) The hexose biphosphate (6C sugar)is split into two triose phosphates and further phosphorylation occurs from inorganic phosphate ions (Pi) in cytosol. 2 triose biphosphates are formed (3C)
3) hydrogen atoms are removed from each of the 3C sugars (via oxidation) to reduce NAD+ to NADH = dehydrogenation. Two molecules of NADH are produced in total ( one from each 3C sugar). NADH is used later in respiration.
4) Some of the energy released from the sugar intermediates is used to directly synthesise ATP. This direct synthesis of ATP is called substrate level phosphorylation (triose biphosphate to pyruvate) In total four molecules of ATP is generated during glycolysis by substrate level phosphorylation ( 2 ATP per 3 C sugar) due to removal of two phosphate groups from each (Pi +ADP = ATP)Two pyruvates are thus formed. (Net gain is 2 ATP)

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9
Q

what is the main difference between aerobic respiration and anaerobic respiration in terms of how much ATP is produced

A

aerobic respiration produces 36ATP but anaerobic produces 2ATP so aerobic produces significantly more

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10
Q

what are all the features of the mitochondria

A
  • outer membrane ~ transport proteins enable shuttling of pyruvate from cytosol
  • inner membrane - contains electron transport chain
    and ATP synthase
    -DNA
    -ribosomes
    -ATP synthase
    -matrix (fluid inside) - cavity contains appropriate enzymes and suitable ph for the Krebs cycle to occur
    -cristae (folds of the inner membrane) - increase sa:v ratio
    -white dots = lipid droplets
  • inter membrane space - membranes maximise hydrogen gradient upon proton accumulation
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11
Q

what are the similarities between the structures of chloroplasts and mitochondria

A
  • both have a double membrane
  • both have the enzyme ATP synthase
  • both have a folded inner membrane
  • both have their own DNA and ribosomes
  • similar shape (biconvex)
  • both have a fluid-filled centre
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12
Q

describe the shape, size and distribution of mitochondria

A
  • rod shaped or thread like
  • up to 1µm diameter
  • 2-5µm long
  • active cells have more mitochondria
  • an athlete may have larger mitochondria and this is due to them having longer and more densely packed cristae
  • moved by cytoskeleton
  • in some cells they’re positioned near a site of high ATP demand
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13
Q

what are the 4 stages of aerobic respiration and where do they all occur

A

1) glycolysis (cytoplasm)
2) link reaction (matrix)
3) Krebs cycle (matrix)
4) electron transport chain / oxidative phosphorylation (membrane of the cristae)

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13
Q

what are the products of glycolysis

A

2 reduced NAD
2 pyruvate
2 ATP (net)

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14
Q

The link reaction ( oxidative decarboxylation)

A

First step in aerobic respiration ( after glycolysis)
1) pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins

2) pyruvate then undergoes oxidative decarboxylation- co2 (decarboxylation) is removed along with a hydrogen (oxidation). The hydrogen atoms removed are accepted by NAD which reduces it to NADH. This forms an acetyl group.
3) results in two acetyl groups binding to coenzyme A forming acetylcoenzyme A (acetyl CoA).
4) this acetyl CoA delivers the acetyl group to next stage of aerobic respiration (Krebs)

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15
Q

The Krebs cycle

A

1) Acetyl CoA delivers an acetyl group to Krebs cycle. The two carbon acetyl group combines with four carbon oxaloacetate to form 6C citrate.
2) the citrate molecule undergoes decarboxylation and dehydrogenation producing one NADH and CO2. A five C compound is formed.
3) the 5C compound undergoes further decarboxylation and dehydrogenation reactions, eventually regenerating oxaloacetate so the cycle continues.
4) IN A SINGLE CYCLE 2co2 , 1 ATP, 1 FADH2, 3 NADPH BUT THE CYCLE HAPPENS TWICE BECAUSE THERE ARE TWO ACETYL COA

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16
Q

what are the products of the link reaction per glucose molecule

A

2 acetyl coenzyme A
2 carbon dioxide
2 NADH

(there are 2 of everything because for every glucose molecule, the link reaction happens twice)

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17
Q

The electron transporter chain - oxidative phosphorylation

A
  • The ETC releases the energy stored within the reduced hydrogen carriers in order to synthesise ATP.
  • this is called oxidative phosphorylation, as the energy to synthesise ATP is derived from the oxidation of hydrogen carriers

OXIDATIVE PHOSPHORYLATION occurs over a number of steps

  • proton pumps create an electrochemical gradient
  • ATP synthase uses the diffusion of protons down electrochemical gradient (chemiosmosis) to synthesise ATP
  • Oxygen accepts electrons and protons to form water
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18
Q

What are the products of the krebs cycle per glucose molecule

A

6 NADH
2 FADH
4 carbon dioxide
2 ATP

(per glucose molecule, the Krebs cycle happens twice. so for one cycle, half the numbers)

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19
Q

For aerobic respiration, if 2.5 ATP are made for every reduced NAD and 1.5 ATP are made for every reduced FAD, how many ATP will be made altogether for one glucose molecule?

A

Glycolysis - 2 ATP and 2 NADH
2+(2X2.5) = 7

Link reaction - 2 NADH
2X2.5 = 5

Krebs cycle - 2 ATP, 6 NADH, 2 FADH
2+(6X2.5)+(2X1.5) = 20

7+5+20 = 32 ATP

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20
Q

It is thought that between 32-36 ATP are made from one glucose molecule in aerobic respiration. Why is this, however, not all used for energy?

A

1) Some ATP is used to actively transport pyruvate into the mitochondria.
2) Some ATP is used to transport ADP into the cell to combine with phosphate ion.
3) Some hydrogen ions (protons) leak across the mitochondrial membrane, reducing the number available for use in chemiosmosis.

21
Q

what happens to aerobic respiration if there’s no oxygen

A

In oxidative phosphorylation, oxygen is the final electron acceptor (when water is formed at the end). So without oxygen, the electron transport chain stops as does the Krebs cycle and link reaction.
Only glycolysis occurs - therefore significantly less ATP is made.
Leads to anaerobic respiration.

22
Q

What type of anaerobic respiration occurs in mammals and describe what happens

A

Lactate fermentation:
The pyruvate formed in glycolysis accepts the hydrogen ions from NADH, turning pyruvate into lactate.
Lactate dehydrogenase catalyses this.
The oxidised NAD is now available to be reused in more glycolysis and generate more ATP.

23
Q

what is the main aim of lactate fermentation and alcoholic fermentation

A

To make NAD which can be used in glycolysis to make ATP.

24
Q

What type of anaerobic respiration occurs in yeast and describe what happens

A

Alcoholic fermentation:
Pyruvate loses carbon dioxide (decarboxylation) to become ethanal.
This is catalysed by the enzyme pyruvate decarboxylase.
The ethanal accepts the hydrogen atoms from NADH to become ethanol, catalysed by ethanol dehydrogenase.
The oxidised NAD can now accept more hydrogen atoms in glycolysis.

25
Q

What are the problems with lactate fermentation

A
  • little ATP is made
  • lactate is acidic and can lower the pH if there are no buffers
  • reduction in pH can reduce enzyme activity in muscles and cause muscle fatigue
26
Q

what are the problems with alcoholic fermentation

A

although yeast can survive without oxygen, it is killed by high levels of ethanol

27
Q

why can diving mammals swim below water without suffering muscle fatigue

A
  • Bigger lung capacity to hold a greater volume of oxygen so they can respire aerobically for longer
  • They have buffers in their blood so they resist changes to pH caused by the lactate produced in anaerobic respiration
  • They close their nostrils to stop air escaping from their lungs so can hold oxygen in their lungs so can respire aerobically for longer
28
Q

define respiratory substrate

A

any biological molecule that can be broken down in respiration to release energy

29
Q

Why do different respiratory substrates release different amounts of energy when they’re respired? give examples

A

Most ATP is made in oxidative phosphorylation which requires hydrogen atoms from NADH and FADH. This measn that respiratory substrates that contain more hydrogen atoms per unit mass cause more ATP to be produced when respired.
Lipids that contain the most hydrogen atoms per unit mass, followed by proteins and then carbohydrates.

30
Q

what is the respiratory quotient

A

the volume of the carbon dioxide produced when that substrate is respired, divided by the volume of oxygen consumed, in a set period of time

31
Q

what 2 equations could you use to calculate the respiratory quotient of a substrate

A

RQ = volume of CO2 released / volume of O2 consumed

RQ = molecules of CO2 released / molecules of O2 consumed

32
Q

what is the RQ value for carbohydrates

A

Use the basic equation for aerobic respiration.
For every 6 molecules of oxygen consumed, 6 molecules of CO2 are released.
6/6 = 1

33
Q

why is the RQ value for lipids and proteins less than 1

A

more oxygen is needed to oxidise fats and lipids than to oxidise carbohydrates (which have an RQ value of 1)

34
Q

how could you calculate the respiratory quotient of a whole organism and why is this useful

A

directly measuring the volume of oxygen consumed and the volume of carbon dioxide released and putting in the equation:
RQ = volume of CO2 released / volume of O2 consumed

it’s useful because it tells you what kind of respiratory substrate an organism is respiring and what type of respiration its using

35
Q

why would a human have an RQ value between 0.7-0.9 under normal conditions

A

some fats are being used for respiration as well as carbohydrates

36
Q

what would a high RQ value mean (higher than 1)

A

the organism is short of oxygen and is having to respire anaerobically

37
Q

why do plants sometimes have low RQs

A

The carbon dioxide released in respiration is used for photosynthesis

38
Q

what is the average amount of energy produced by each of these respiratory substrates?

a) carbohydrates
b) lipids
c) proteins

A

carbohydrates - 15.8 kJ

lipids - 39.4 kJ

proteins - 17 kJ

39
Q

what is the average amount of energy produced by each of these respiratory substrates?

a) carbohydrates
b) lipids
c) proteins

A

carbohydrates - 15.8 kJ

lipids - 39.4 kJ

proteins - 17 kJ

40
Q

outline an experiment you could use to investigate the rate of aerobic respiration in yeast

A

1) Put a known volume and concentration of substrate solution in a test tube.
2) Add a known volume of buffer solution to keep the pH constant.
3) Place the test tube in a water bath set to 25 degrees. Leave for 10 mins so it can acclimatise.
4) Add a known mass of dried yeast and stir for 2 mins.
5) After the yeast has dissolved, put a bung with a tube attached to a gas syringe in the top of the test tube.
6) Start a stop watch as soon as the bung has been put in the test tube.
7) As the yeast respires, CO2 formed will travel up the tube and into the gas syringe which is used to measure the volume of CO2 released.
8) At regular time intervals, record the volume of CO2 that is present in the gas syringe. Do this for a set amount of time.
9) A control experiment should also be set up where no yeast is present so no CO2 should be formed.
10) Repeat the experiment 3 times. Calculate the mean rate of CO2 production.

41
Q

Outline an experiment you could use to investigate the rate of anaerobic respiration in yeast

A

1) Put a known volume and concentration of substrate solution in a test tube.
2) Add a known volume of buffer solution to keep the pH constant.
3) Place the test tube in a water bath set to 25 degrees. Leave for 10 mins so it can acclimatise.
4) Add a known mass of dried yeast and stir for 2 mins.
5) After the yeast has dissolved into the substrate, trickle some liquid paraffin down the inside of the 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.
6) Put a bung, with a tube attached to a gas syringe, in the top of the test tube.
7) Start a stop watch as soon as the bung has been put in the test tube.
8) As the yeast respires, CO2 formed will travel up the tube and into the gas syringe which is used to measure the volume of CO2 released.
9) At regular time intervals, record the volume of CO2 that is present in the gas syringe. Do this for a set amount of time.
10) A control experiment should also be set up where no yeast is present so no CO2 should be formed.
11) Repeat the experiment 3 times. Calculate the mean rate of CO2 production.

42
Q

Outline how you could use respirometers to measure the rate of respiration in woodlice.

A

Page 145 of revision guide. (shows how apparatus is set up)

1) A syringe is used to set the coloured fluid to a known level.
2) Leave the apparatus for a set time. There will be a decrease in the volume of air in the test tube, due to oxygen consumption by the woodlice. The decrease in the volume of air will reduce the pressure in the tube and cause the coloured liquid in the manometer to move towards the test tube.
3) The distance moved by the liquid in a given time is measured. This can then be used to calculate the volume of oxygen taken in by the woodlice per minute.
4) Any variables that could affect the results are controlled and kept the same (eg. volume of potassium hydroxide and mass of woodlice)
5) Repeat experiment 3 times and calculate the mean volume of oxygen taken in by the woodlice.

43
Q

Why would it be better to attach a respirometer to sensors and data loggers

A

Reduces the chance of human error.
The data collected by the data logger can be put into data analysis software which can help you to analyse your data and draw conclusions from your experiment.

44
Q

what is the chemiosmotic theory or chemiosmosis

A

the process of ATP production driven by the movement of hydrogen ions across a membrane (due to electrons moving down the ETC)

45
Q

Where does respiration occur in eukaryotes and prokaryotes?

A

Eukaryotes - cytoplasm and mitochondria

Prokaryotes- cytoplasm and cell membrane

46
Q

Importance of coenzymes in respiration

A
  • Coenzymes Are required to transfer protons, electrons and functional groups between many of these enzyme catalysed reactions
  • redox reactions have an important role in respiration and thus without coenzymes transferring electrons and protons between these reactions many respiratory enzymes would be unable to function
  • NAD and FAD are both coenzymes that accept protons and electrons released during the breakdown of glucose in respiration.
47
Q

Differences between NAD and FAD

A
  • NAD takes part in all stages of cellular respiration. But FAD only accepts hydrogens in the Krebs cycle.
  • NAD accepts one hydrogen and FAD accepts two hydrogen
  • NADH is oxidised at start of the electron transport chain releasing protons and electrons while FADH is oxidised further along the chain.
  • NADH results in synthesis of 3 ATP but FADH results in the synthesis of only two ATP molecules
    Coenzymes are usually derived from vitamins
48
Q

Why is glucose a good respiratory substrate?

A

1) Glycolysis (cytoplasm) phosphorylation and oxidation
2) link reaction (oxidative decarboxylation in matrix of mitochondria)
3) Krebs cycle (mitochondria)
4) electron transport chain (mitochondria cristae ) oxidative phosphorylation

49
Q

What is respiration?

A

A series of oxidative reactions removing hydrogens to form ATP

50
Q

Oxidative phosphorylation ( Electron transporter chain)

A

1) The hydrogen carriers (NADH And FADH ) are oxidised and release high energy electrons and protons.
2) The electrons are transferred to the ETC which consists of several transmembrane carrier proteins
3) as electrons pass through the chain, they loose energy which is used by chain to pump protons from the matrix into the intermembrane space
4) the accumulation of H+ ions within the intermembrane space creates an ec gradient
5)These protons move back into the matrix diffusing down a concentration gradient through a channel protein, activating ATP synthase.
6) ATP synthase catalyses the reaction to produce ATP (this chemical movement is called chemiosmosis)
6)lastly reduction of oxygen occurs where the de-energised electrons are accepted by oxygen to remove them to allow the ETC to continue and prevent the chain from blocking.
7) the oxygen also binds with free protons in matrix which forms water which maintains the proton gradient
(IN ABSENSE OF OXYGEN HYDROGEN CARRIERS CANT TRANSFER ENERGISED ELECTRONS TO CHAIN AND ATP PRODUCTION HALTED)

A-Level Biology (23 decks)

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