Respiration

Question 1

What type of sugar is glucose?

Answer 1

A hexose sugar produced during photosynthesis

Question 2

What happens to glucose in respiration

Answer 2

Broken down and carbon-hydrogen bonds are broken. Energy released used in synthesis of ATP by chemiosmosis.

Question 3

What is the first stage of respiration

Answer 3

Occurs in the cytoplasm of the cell and doesn’t require oxygen as is anaerobic

Question 4

What’s the first stage of glycolysis and what happens

Answer 4

Phosphorylation

The first step of glycolysis requires two molecules of ATP. Two phosphates, released from two ATP molecules are attached to a glucose molecule forming hexose bisphosphate

Question 5

What’s the second stage of glycolysis

Answer 5

Lysis

This destabilises the molecule causing it to split into two triose phosphate molecules

Question 6

What’s the third stage of glycolysis

Answer 6

Phosphorylation

Another phosphate group is added to each triose phosphate forming two triose bisphosphate molecules. These come from the free inorganic phosphate ions present in the cytoplasm

Question 7

What’s the fourth stage of glycolysis

Answer 7

Dehydrogenation and formation of ATP-

The two triose bisphosphate molecules are then oxidised by the removal of hydrogen atoms (dehydrogenation) to form two pyruvate molecules

NAD coenzymes accept the removed hydrogens- reduced forming two reduced NAD molecules

Question 8

What is substrate level phosphorylation

Answer 8

The formation of ATP without the involvement of an electron transport chain. ATP is formed by the transfer of a phosphate group from a phosphorylated intermediate to ADP.

Question 9

Where does glycolysis occur

Answer 9

In the cytoplasm

Question 10

What is the link reaction (oxidative decarboxylation)

Answer 10

It is the first step in aerobic respiration

Pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins.
Pyruvate then undergoes oxidative carboxylation- carbon dioxide and hydrogen removed.

Hydrogen atoms removed are accepted by NAD- which is reduced to from NADH.

The resulting two carbon acetyl group is bound by Coenzyme A to make acetyl CoA.

Acetyy CoA delivers the acetyl group to the next stage of aerobic respiration- Krebs cycle

Reduced NAD used to synthesise ATP

Question 11

The Krebs cycle

Answer 11

Each complete cycle results in the breakdown of an acetyl group. Acetyl groups are all that remains of the glucose that enters glycolysis

Involves decarboxylation, dehydrogenation and substrate-level phosphorylation.

Hydrogen atoms released are picked up by NAD and FAD.

CO2 is a byproduct and ATP produced is available for use by energy requiring processes

Question 12

Steps of the Krebs cycle

Answer 12

1. Acetyl CoA delivers an acetyl group to the Krebs cycle. Two-carbon acetyl group combines with a four carbon oxaloacetate to form six carbon citrate
2. Citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD and CO2- a FIVE carbon compound is formed
3. The five carbon compound undergoes further decarboxylation and dehydrogenation reactions- eventually regenerating oxaloacetate.

Cycle continues- more co2, two more reduced NAD and one reduced FAD are produced. ATP produced by substrate level phosphorylation

Question 13

What are the differences in NAD and FAD

Answer 13

NAD takes part in all stages of cellular respiration but FAD only accepts hydrogens in the Krebs cycle

NAD accepts only one hydrogen and FAD accepts two hydrogens

Reduced NAD is oxidised at start of ETC releasing protons and electrons while reduced FAD is oxidised further along the chain

Reduced NAD results in the synthesis of three ATP molecules but reduced FAD results in the synthesis of only two ATP molecules

Question 14

What are NAD and FAD

Answer 14

Both coenzymes that accept protons and electrons released during the breakdown of glucose in respiration

Question 15

What is the importance of coenzymes

Answer 15

Required to transfer protons, electrons and functional groups between many of these enzyme catalysed reactions.

Question 16

What is oxidative phosphorylation

Answer 16

Hydrogen atoms collected by the coenzymes NAD and FAD are delivered to the ETC in the membranes of the cristae of the mitochondria

Hydrogen atoms disassociate into hydrogen ions and electrons, the high energy electrons are used in synthesis of ATP by chemiosmosis.

Energy released in redox relations as the electrons reduce and oxidise electron carriers as they flow along the ETC. Creates a proton gradient leading to the diffusion of protons through ATP synthase- synthesis of ATP

At end of ETC- electrons combine with hydrogen ions and oxygen to form water. Oxygen is final electron acceptor

Question 17

What is substrate level phosphorylation

Answer 17

Production of ATP involving transfer of a phosphate group from an intermediate such as creatine phosphate.