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OCR 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

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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9
Q

what are all the features of the mitochondria

A
  • inner and outer membrane
  • DNA
  • ribosomes
  • ATP synthase
  • matrix (fluid inside)
  • cristae (folds of the inner membrane)
  • granules
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10
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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11
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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12
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

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14
Q

what is the process of glycolysis

A

1) Phosphorylation - glucose (6C) is phosphorylated by adding a phosphate from a molecule of ATP.
2) This creates one molecule of hexose phosphate (6C) and a molecule of ADP.
3) Hexose phosphate is phosphorylated by ATP to form hexose bisphosphate (6C) and another molecule of ADP.
4) Hexose bisphosphate is split up into 2 molecules of triose phosphate (3C).
5) Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate (3C).
6) NAD collects the hydrogen ions, forming 2 reduced NAD.
7) 4 ATP are produced but 2 were used up in stage 1 so there’s a net gain of 2 ATP.

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15
Q

what is the process of the link reaction

A

If there’s enough oxygen, pyruvate is actively transported into the matrix of the mitochondria.

1) Pyruvate is decarboxylated so one carbon atom is removed from pyruvate in the form of carbon dioxide.
2) NAD is reduced - it collects hydrogen from pyruvate, changing pyruvate into acetate.
3) Acetate is combined with coenzyme A to form acetyl coenzyme A.

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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

what are the steps of the Krebs Cycle?

A

1) Acetyl coenzyme A from the link reaction combines with oxaloacetate to form citrate (citric acid).
2) Citrate is decarboxylated and dehydrogenated to form a 5-carbon compound. NAD accepts the hydrogen atoms and becomes reduced.
3) This 5-carbon compound then is decarboxylated and dehydrogenated too. This forms a 4-carbon compound and another NADH.
4) The 4-carbon compound is changed to another 4-carbon compound. During this a molecule of ADP is phosphorylated to produce an ATP molecule.
5) This is changed into another 4-carbon compound. A pair of hydrogen atoms is removed and accepted by the coenzyme FAD, which is reduced.
6) The third 4-carbon compound is dehydrogenated and regenerates oxaloacetate. Another molecule of NAD is reduced.

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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

What is the process of oxidative phosphorylation

A

1) The NADH or FADH from the Krebs cycle are reoxidised and they release a hydrogen atom.
2) The hydrogen atom splits into an electron and hydrogen ion (proton).
3) The electron passes down the electron carrier chain, releasing energy.
4) This energy is used to pump the hydrogen ions from the matrix into the intermembrane space.
5) There is now a higher concentration of hydrogen ions in the intermembrane space so they diffuse down a concentration gradient through a channel protein, activating ATP synthase.
6) ATP synthase catalyses the reaction to produce ATP.
7) The hydrogen ions are collected, along with the electrons from the carrier chain and they react with oxygen to produce water.

20
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

21
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.

22
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.

23
Q

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

A

Lactate fermentation:
The pyruvate formed in glycolysis accepts the hydrogen toms 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.

24
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.

25
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.

26
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
27
Q

what are the problems with alcoholic fermentation

A

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

28
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
29
Q

define respiratory substrate

A

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

30
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.

31
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

32
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

33
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

34
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)

35
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

36
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

37
Q

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

A

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

38
Q

why do plants sometimes have low RQs

A

The carbon dioxide released in respiration is used for photosynthesis

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

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

41
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.

42
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.

43
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.

44
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.

45
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)

OCR A LEVEL BIOLOGY (23 decks)

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