Unit 1 - Cellular respiration Key Area 7

Question 1

What is Glycolysis

Answer 1

Glycolysis is the breakdown of glucose to

pyruvate in the cytoplasm.

Question 2

Describe the Glycolysis

Answer 2

Glucose is broken down to pyruvate through a series of enzyme controlled reactions.
Takes place in the cytoplasm

Energy investment stage = ATP is required here to phosphorylate glucose and intermediate molecules.
2ATP are added

Energy pay off stage = ATP is made
4ATP is generated here, giving a net gain of 2ATP
Hydrogen ions and electrons are removed during glycolysis and passed to coenzyme NAD to form NADH

Dehydrogenase = enzyme that removes hydrogen ions and electrons.

Question 3

What is Cellular Respiration

Answer 3

Cellular respiration is a series of metabolic pathways that releases energy from food and generates a high energy compound called adenosine triphosphate (ATP)

Question 4

When is energy released from ATP

Answer 4

Energy is released from ATP when the bond attached to the terminal phosphate is broken by enzyme action

ATP releases energy and breaks down to form Adenosine diphosphate (ADP) and inorganic phosphate (Pi)

Question 5

Why is ATP so important

Answer 5

ATP is very important as it acts as the link between catabolic energy releasing reactions (e.g. respiration) and anabolic energy-consuming reactions (e.g. protein synthesis)

Question 6

Why do humans not need a vast store of ATP

Answer 6

ATP is continuously made at the same time as it is being used up, so there is no need for humans to have a vast store of ATP

Question 7

What is Phosphorylation

Give an example

Answer 7

Phosphorylation is an enzyme controlled process where a phosphate group is added to a molecule.

The conversion of ADP to ATP is an example of phosphorylation.

ADP + Pi —> ATP

Question 8

Name the three stages of Cellular Respiration

Answer 8

There are 3 stages involved in Cellular Respiration:-

Stage 1 – Glycolysis (occurs in the cytoplasm of a cell)

Stage 2 – Citric Acid Cycle ( occurs in the mitochondrial matrix)

Stage 3 – Electron Transport Chain (occurs in the inner membrane of mitochondria)

Question 9

Describe the Citric Acid Cycle

Answer 9

Oxygen is required (aerobic respiration)
Takes place in the matrix of the mitochondria

Pyruvate is broken down to form an acetyl group and combines with Coenzyme A to form Acetyl Coenzyme A
The acetyl group of Acetyl Coenzyme A combines with Oxaloacetate to form Citrate
The cycle then involves many enzyme controlled steps which results in:-
- Regeneration of Oxaloacetate
- Release of Carbon Dioxide
- Generation of ATP
Dehydrogenase enzymes remove H+ ions and electrons and pass them to NAD to make NADH.

Question 10

Describe the Electron Transport Chain

Answer 10

1) The Electron Transport Chain consists of protein molecules found attached to the inner membrane of the mitochondria
2) NADH from Glycolysis and the Citric Acid pathways release high-energy electrons to the electron transport chain.
3) The flow of electrons pump hydrogen ions across the membrane. This creates a high concentration of hydrogen ions in the inter membrane space.
4) The hydrogen ions then flow through the enzyme, ATP synthase, moving from a high concentration to a low concentration. The flow of hydrogen ions drives the enzyme to synthesise the build up of ADP + Pi to ATP
5) The electrons leave the electron transport chain in a low energy state and combine with oxygen and hydrogen to form water.

Oxygen is said to be the final electron acceptor.