Topic 8.2: Cellular respiration

Question 1

How are organic molecules broken down?

Answer 1

Via a number of discrete processes

a) By staggering the breakdown, the energy requirements are reduced
b) Released energy is transferred to electron carriers via redox reactions.

Question 2

Reduction reactions

Answer 2

a) Gain of electrons / hydrogen

b) Loss of oxygen

Question 3

Oxidation reactions

Answer 3

a) Loss of electrons / hydrogen

b) Gain of oxygen

Question 4

Function of electron carriers

Answer 4

Transfer chemical energy via redox reactions

a) Organic molecules are oxidized to form reduced carriers
b) Reduced carriers are oxidized to form ATP

Question 5

Examples of electron carriers

Answer 5

a) NAD+ + 2H+ + 2e– → NADH + H+

b) FAD + 2H+ + 2e– → FADH2

Question 6

Definition of ATP

Answer 6

High energy molecule that works as an immediate source of energy for cell processes

Question 7

Function of ATP

Answer 7

a) Energy currency of the cell by releasing energy when hydrolyzed to ADP
b) Transfer a PO4 3- to an organic molecule, make them less stable and more reactive

Question 8

Glycolysis

a) Site
b) Conditions

Answer 8

a) Cytoplasm

b) Absence of hydrogen

Question 9

Reactants of glycolysis

Answer 9

a) Carbohydrates
b) Lipids
c) Proteins

Question 10

Steps of glycolysis

Answer 10

a) Phosphorylation
b) Lysis
c) Oxidation
d) ATP formation

Question 11

Phosphorylation

Answer 11

a) Glucose is phosphorylated by 2 molecules of ATP, forming an hexose biphosphate
b) This makes the molecule less stable

Question 12

Lysis

Answer 12

Hexose biphosphate is split into two triose phosphates

Question 13

Oxidation

Answer 13

a) Hydrogen atoms are removed from each of the 3C sugars to reduce NAD+
b) Two molecules of NADH are produced in total

Question 14

ATP formation

Answer 14

a) Some of the energy released from the sugar intermediates is used to synthesize ATP
b) Four molecules of ATP are produced in total via substrate level phosphorylation

Question 15

Products of glycolysis

Answer 15

a) 4 ATP molecules (2 net ATP)
b) 2 NADH + H+
c) 2 Pyruvate

Question 16

Site of link reaction

Answer 16

Matrix of the mitochondria

Question 17

Type of chemical reactions in link reaction

Answer 17

Oxidative decarboxylation

Question 18

Steps of link reaction

Answer 18

a) Pyruvate is transported from the cytosol into the mitochondrial matrix
b) Pyruvate is decarboxylated (CO2 produced)
c) 2C compound loses hydrogen atoms via oxidation (reduction of NADH)
d) Coenzyme A binds to acetyl to form Acetyl CoA

Question 19

Products of Link Reaction

Answer 19

a) 2 NADH + H+
b) 2 CO2
c) 2 Acetyl CoA

Question 20

Site of Krebs Cycle

Answer 20

Matrix of the mitochondria

Question 21

Steps in Krebs Cycle

Answer 21

a) Acetyl CoA transfers its acetyl group to oxaloacetate to make citrate (CoA is released)
b) Two C atoms are released via decarboxylation to form molecules of CO2
c) Multiple oxidation reactions (4) result in the reduction of electron carriers (NAD + FAD)
d) One molecule of ATP is produced via substrate level phosphorylation

Question 22

Products of Krebs Cycle

Answer 22

a) 4 CO2
b) 2 ATP
c) 2 FADH2
d) 6 NADH + H+

Question 23

Site of electron transport chain

Answer 23

Inner mitochondrial membrane

Question 24

What happens in oxidative phosphorylation?

Answer 24

Energy within the reduced hydrogen carriers is released to synthesize ATP via oxidation reactions

Question 25

Process in Electron Transport Chain

Answer 25

a) Generating a proton motive force
b) ATP synthesis via chemiosmosis
c) Reduction of oxygen

Question 26

Generating a proton motive force (1)

Answer 26

a) Electron carriers are oxidized and release high energy electrons and protons
b) Electrons are transferred to electron carriers, which consist of various transmembrane proteins
c) As electrons pass through the chain, they lose energy which is used to pump protons from the matrix
d) The accumulation of protons within the intermembrane space creates an electrochemical gradient

Question 27

ATP synthesis (2)

Answer 27

a) The electrochemical gradient causes H+ to diffuse back into matrix through ATP synthase
b) As protons move through ATP synthase, they trigger the synthesis of ATP from ADP + Pi

Question 28

Reduction of oxygen (3)

Answer 28

a) Oxygen acts as the final electron acceptor from the ETC, preventing the chain from becoming blocked
b) Oxygen binds with free protons to form water, Maintaining the hydrogen gradient

Question 29

Products of electron transport chain

Answer 29

32 ATP

6 H2O

Question 30

Function of mitochondria

Answer 30

Synthesize large amounts of ATP via aerobic respiration

Question 31

Structure of mitochondria

Answer 31

a) Outer membrane
b) Inner membrane
c) Cristae
d) Intermembrane space
e) Matrix
f) Ribosome 70S
g) Loops of DNA

Question 32

Adaptation

Answer 32

A change in structure so that something carries out its function more efficiently

Question 33

Function of outer membrane in mitochondria

Answer 33

Separates the contents of the mitochondrion from the cytosol

Question 34

Function of inner membrane in mitochondria

Answer 34

Contains ETC and ATP synthase used for oxidative phosphorylation

Question 35

Function of cristae in mitochondria

Answer 35

Inner membrane is arranged into folds that increase the SA:Vol ratio

Question 36

Function of intermembrane space

Answer 36

Small space to easily accumulate protons in chemiosmosis

Question 37

Function of Ribosome 70S / Loops of DNA

Answer 37

Expression of mitochondrial proteins

Question 38

Definition of electron transport chain

Answer 38

Series of electron carriers, located in the inner membrane of the mitochondrion

Question 39

Definition of chemiosmosis

Answer 39

Generation of ATP using energy released by the movement of hydrogen ions across a membrane