3.5 Respiration

Question 1

ATP Summary

Answer 1

Nucleotide derivative
Composed of the base adenine, pentose sugar ribose + 3 phosphate groups

Question 2

Substrate-level phosphorylation

Answer 2

mitochondrial matrix

Question 3

Oxidative phosphorylation

Answer 3

mitochondrial cristae

Question 4

glycolysis

Answer 4

cytoplasm

Question 5

summary of glycolysis

Answer 5

the splitting of the 6C glucose into two 3C pyruvates

Question 6

summary of the link reaction

Answer 6

the 3C pyruvate enter into a series of reactions to form acetyl coenzyme A, a 2C molecule

Question 7

summary of Krebs

Answer 7

the introduction of acetyl coenzyme A into a cycle of REDOX reactions that yield some ATP and a large quantity of reduced NAD and FAD

Question 8

summary of oxidative phosphorylation

Answer 8

the use of the electrons associated with reduced NAD and FAD from Krebs to synthesise ATP with water produced as a by-product

Question 9

detailed steps of glycolysis

Answer 9

Phosphorylation of glucose to glucose phosphate:

Two molecules of ATP are hydrolysed to release two phosphate groups which are added onto the glucose 6C molecule. This provides the energy to activate glucose and lowers activation energy for the following enzyme controlled reactions. Forms glucose phosphate 6C.

Splitting of glucose phosphate:

Each glucose molecule splits into two 3C Triose Phosphate molecules, each with one phosphate group

Oxidation of triose phosphate:

Hydrogen is removed from TP by dehydrogenase enzymes and is accepted by NAD, reducing the coenzyme which then carries the protons and electrons to the mitochondrial cristae for oxidative phosphorylation. This oxidises TP.

Production of ATP:

Enzyme controlled reactions convert each oxidised TP into 3C pyruvate which produces two molecules of ATP, after being regenerated from ADP.

Question 10

energy yield of glycolysis

Answer 10

One glucose molecule produces two molecules of TP so produces four molecules of ATP and two molecules of reduced NAD + pyruvate
Overall, one glucose produces two ATP, one RNAD, and one Pyruvate

Question 11

detailed steps of link reaction

Answer 11

Pyruvate (2 molecules) are actively transported into the mitochondrial matrix by being actively pumped across the outer and inner mitochondrial membrane.
One molecule of pyruvate is decarboxylated and dehydrogenated to become oxidised to acetate. The 2C acetate combines with coenzyme A to form acetyl coenzyme A.
The decarboxylation of 3C pyruvate releases a carbon dioxide molecule, dehydrogenation releases two hydrogens. NAD accepts released hydrogens to form reduced NAD, which is later used to form ATP.

Question 12

decarboxylation

Answer 12

the removal of a carboxyl group from a substrate

Question 13

dehydrogenation

Answer 13

removal of hydrogen atoms from a substrate

Question 14

Pyruvate dehydrogenase complex

Answer 14

catalyses the decarboxylation and dehydrogenation of 3C pyruvate

Question 15

why does link need to occur in the matrix

Answer 15

the matrix contains specific enzymes to catalyse steps of the reaction and contains molecules of NAD.

Question 16

yield of link

Answer 16

2 reduced NAD, 0 reduced FAD, 2 carbon dioxide and 0 ATP (2 rounds.)
The reaction has to go twice because two molecules of pyruvate are produced from glycolysis

Question 17

detailed steps of the Krebs cycle

Answer 17

The 2C acetyl group released from acetyl coenzyme A combines with a 4C molecule to produce a 6 carbon molecule (citrate)
The 6 carbon molecule loses carbon dioxide and hydrogen to form a 4 carbon molecule in a series of reactions and a single molecule of ATP produced by substrate level phosphorylation (overall loses 2 molecules of carbon dioxide and reduced NAD)
The 4C compound is dehydrogenated to produce a different 4C compound and reduced FAD
Catalysis of an isomerase enzyme causes a different arrangement of the atoms so the original 4C oxaloacetate is regenerated and one molecule of reduced NAD is produced

Question 18

yield of krebs

Answer 18

3 reduced NAD, 1 reduced FAD, 2 ATP and 2 CO2 released from Krebs each round. 0 ATP is used in Krebs and 2 are made so net is 2.

Question 19

significance of Krebs

Answer 19

Breaks down macromolecules into smaller ones, pyruvate is broken down into carbon dioxide molecules
Produces hydrogen atoms which are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation which leads to the production of ATP to provide metabolic energy for the cell
Regenerates 4C molecule that combines with CoA which would otherwise accumulate
Source of immediate compounds that are used by cells in the manufacture of fatty acids, amino acids and chlorophyll

Question 20

absence of oxygen on Krebs and link

Answer 20

All FAD and NAD will be reduced so none will be available to take up the protons produced during Krebs so enzymes will stop working

Question 21

the need for hydrogen to be removed in glycolysis in anaerobic

Answer 21

Without hydrogen, the already limited supply of NAD in cells will be entirely converted into reduced NAD, leaving no NAD to take up hydrogen produced from glycolysis

Question 22

how is NAD replenished in anaerobic respiration

Answer 22

reduced NAD donates hydrogen to to the pyruvate molecule formed from glycolysis

Question 23

products of anaerobic in plants

Answer 23

ethanol and carbon dioxide

Question 24

products of anaerobic in animals

Answer 24

lactate

Question 25

production of ethanol in some microorganisms

Answer 25

The pyruvate formed at the end of glycolysis loses a molecule of carbon dioxide It also accepts hydrogen from reduced NAD to form ethanol Pyruvate + reduced NAD = CH3CH2OH + carbon dioxide + oxidised NAD

Question 26

production of lactate in animals

Answer 26

When oxygen is in short supply, NAD from glycolysis can accumulate and needs to be removed In order to remove NAD, each pyruvate molecule produced takes up the two hydrogen atoms donated by the reduced NAD to form lactate Pyruvate + reduced NAD = lactate + oxidised NAD

Question 27

summary of eukaryotic anaerobic respiration

Answer 27

The products of glycolysis are two molecules of pyruvate and 2 of reduced NAD as well as a net gain of 2 ATP. The pyruvate molecules accept the hydrogen atoms from reduced NAD, which is catalysed by lactate dehydrogenase Pyruvate is reduced and converted to two molecules of lactate The reduced NAD are reoxidised so glycolysis can continue because the coenzymes can accept the hydrogen atoms released during the oxidation of triose phosphate

Question 28

effect of lactate accumulating

Answer 28

can cause cramping and muscle fatigue. It also causes pH changes which affect enzymes due to its acidic nature. Lactate needs to be taken to the liver to be converted into glycogen after being removed by the blood.

Question 29

why can krebs or electron transfer chain not occur in anaerobic respiration

Answer 29

Pyruvate is converted to lactate or ethanol so is not available for krebs, means neither krebs or the electron transfer chain can take place so the only source of ATP in anaerobic respiration is glycolysis

Question 30

detailed steps of oxidative phosphorylation

Answer 30

Reduced NAD and FAD deliver their hydrogen atoms to the electron transfer chain, re oxidising the coenzymes Hydrogen atoms split to produce protons and electrons Protons go into solution in the mitochondrial matrix Electrons are accepted by the first electron carrier in the electron transfer chain Iron 3 ion accepts the electron and is reduced to iron 2 This accepted electron is donated to the next cytochrome in the chain Energy is released when each electron is donated to the next cytochrome which is used to pump protons from the matrix across the inner mitochondrial membrane and into the intermembrane space Protons accumulate in the intermembrane space due to reduced permeability of the inner membrane and this forms a proton gradient across the membrane Protons diffuse through the channels by chemiosmosis and cause a conformational change to the rotator ATP synthase ATP synthase now catalyses the synthesis of ATP Oxygen combines with electrons off the final protein in the electron transfer chain and with protons diffusing down the channel to form water Oxygen acts as the final electron acceptor

Question 31

why do reoxidised NAD and FAD return to the matrix

Answer 31

The reoxidised NAD and FAD coenzymes return to the matrix where they work with dehydrogenase enzymes and accept any released protons in the link reaction or krebs cycle, this allows the reactions to continue.

Question 32

why is oxygen important as the final electron acceptor

Answer 32

otherwise the protons and electrons would ‘back up’ along the chain and respiration would stop.

Question 33

why are electrons transferred down an energy gradient

Answer 33

The greater the energy that is released in a single step, the more of it that is released as heat and there is less available for more useful purposes. This is why electrons are transferred down an energy gradient where each carrier is at a slightly lower energy level, because energy can be released gradually and more usefully.

Question 34

define respiratory substrate

Answer 34

organic molecules that can be oxidised by respiration to release energy to make molecules of ATP

Question 35

Respiration of lipids

Answer 35

Hydrolysed to glycerol + fatty acids Glycerol phosphorylated and converted to triose phosphate for use in glycolysis and Krebs Fatty acid broken into 2C components converted to acetyl coenzyme A which is used in Krebs Protons produced from high ratio of hydrogen atoms form a chemiosmotic gradient across the inner mitochondrial membrane to help form ATP in oxidative phosphorylation

Question 36

respiration of proteins

Answer 36

Deamination necessary because the amine group is toxic so the amino acid cannot be stored if in excess unless it is removed Depending on the number of carbons they contain, they enter at different points E.g 3C to pyruvate, 4 + 5C to intermediates in Krebs