M5, C18 Respiration

Question 1

define respiration

Answer 1

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

Question 2

give some examples of what ATP is used for

Answer 2

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

Question 3

how much energy is released when you hydrolyse ATP to ADP

Answer 3

30.6 kJmol^-1

Question 4

what is the structure of ATP

Answer 4

3 phosphates
ribose sugar
adenine base

Question 5

what is the word equation and symbol equation for aerobic respiration

Answer 5

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

look up symbol equation

Question 6

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

Answer 6

glucose -> ethanol + carbon dioxide + 2ATP

look up symbol

Question 7

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

Answer 7

glucose -> lactate + 2ATP

Question 8

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

Answer 8

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

Question 9

what are all the features of the mitochondria

Answer 9

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

Question 10

what are the similarities between the structures of chloroplasts and mitochondria

Answer 10

• 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

Question 11

describe the shape, size and distribution of mitochondria

Answer 11

• 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

Question 12

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

Answer 12

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

Question 13

what are the products of glycolysis

Answer 13

2 reduced NAD
2 pyruvate
2 ATP

Question 14

what is the process of glycolysis

Answer 14

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.

Question 15

what is the process of the link reaction

Answer 15

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.

Question 16

what are the products of the link reaction per glucose molecule

Answer 16

2 acetyl coenzyme A
2 carbon dioxide
2 NADH

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

Question 17

what are the steps of the Krebs Cycle?

Answer 17

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.

Question 18

What are the products of the krebs cycle per glucose molecule

Answer 18

6 NADH
2 FADH
4 carbon dioxide
2 ATP

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

Question 19

What is the process of oxidative phosphorylation

Answer 19

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.

Question 20

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?

Answer 20

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

Question 21

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?

Answer 21

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.

Question 22

what happens to aerobic respiration if there’s no oxygen

Answer 22

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.

Question 23

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

Answer 23

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.

Question 24

what is the main aim of lactate fermentation and alcoholic fermentation

Answer 24

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

Question 25

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

Answer 25

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.

Question 26

What are the problems with lactate fermentation

Answer 26

• 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

Question 27

what are the problems with alcoholic fermentation

Answer 27

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

Question 28

why can diving mammals swim below water without suffering muscle fatigue

Answer 28

• 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

Question 29

define respiratory substrate

Answer 29

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

Question 30

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

Answer 30

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.

Question 31

what is the respiratory quotient

Answer 31

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

Question 32

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

Answer 32

RQ = volume of CO2 released / volume of O2 consumed

RQ = molecules of CO2 released / molecules of O2 consumed

Question 33

what is the RQ value for carbohydrates

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

some fats are being used for respiration as well as carbohydrates

Question 36

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

Answer 36

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

Question 37

why do plants sometimes have low RQs

Answer 37

The carbon dioxide released in respiration is used for photosynthesis

Question 38

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

a) carbohydrates
b) lipids
c) proteins

Answer 38

carbohydrates - 15.8 kJ

lipids - 39.4 kJ

proteins - 17 kJ

Question 39

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

a) carbohydrates
b) lipids
c) proteins

Answer 39

carbohydrates - 15.8 kJ

lipids - 39.4 kJ

proteins - 17 kJ

Question 40

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

Answer 40

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.

Question 41

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

Answer 41

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.

Question 42

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

Answer 42

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.

Question 43

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

Answer 43

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.

Question 44

what is the chemiosmotic theory or chemiosmosis

Answer 44

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