Respiration

What Respiration covers

Respiration closes Module 5. It covers the mitochondrion and the role of ATP, glycolysis, the link reaction and the Krebs cycle, oxidative phosphorylation and chemiosmosis, what happens when oxygen runs out, and how the respiratory quotient identifies the substrate being used.

The 6 subtopics

Each one has its own page.

• Respiration, ATP and the mitochondrionWhat respiration transfers and why plants, animals and microorganisms all need it, and the membranes, cristae, matrix and DNA of a mitochondrion.Open →
• GlycolysisWhere it happens, the two phosphorylation steps, the splitting of hexose bisphosphate into triose phosphate, and the net ATP and reduced NAD produced.Open →
• The link reaction and the Krebs cycleDecarboxylation of pyruvate and the formation of acetyl coenzyme A, the citrate cycle, and the decarboxylation, dehydrogenation and coenzymes involved.Open →
• Oxidative phosphorylation and chemiosmosisThe electron transport chain and the role of oxygen, the proton gradient across the inner membrane, and how chemiosmotic theory explains ATP synthesis.Open →
• Anaerobic respirationWhat happens to pyruvate in mammals and in yeast, why regenerating NAD matters, and how the ATP yield compares with aerobic respiration.Open →
• Respiratory substrates and the respiratory quotientWhy lipids yield more energy per unit mass than carbohydrates, how proteins are used, and the respiratory quotient, the respirometer and the variables to control.Open →

What you need to know

Answer each one before you reveal it.

Take Respiration further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Glycolysis vs The link reaction

  Glycolysis: the cytoplasmic splitting of glucose into two molecules of pyruvate. The link reaction: the mitochondrial conversion of pyruvate into acetyl coenzyme A.

• Substrate-level phosphorylation vs Oxidative phosphorylation

  Substrate-level phosphorylation: making ATP by transferring a phosphate directly from another molecule. Oxidative phosphorylation: making ATP using energy from electrons passing along the transport chain.

• Chemiosmosis vs The electron transport chain

  Chemiosmosis: the flow of protons through ATP synthase down their gradient. The electron transport chain: the series of carriers whose electron transfers build that gradient.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Define respiration in terms of energy transfer.

   Model answer

   Respiration transfers the energy held in complex organic molecules across to ATP.

2. 2

   What is the role of ATP in biological processes?

   Model answer

   ATP provides the immediate source of energy for biological processes.

3. 3

   Why do plants need to respire?

   Model answer

   Plants need to respire to provide ATP for active transport of mineral ions across root cell membranes.

4. 4

   State two processes in animals that require ATP from respiration.

   Model answer

   Muscle contraction and active transport.

5. 5

   Why do microorganisms need to respire?

   Model answer

   Microorganisms need to respire to provide ATP for metabolic reactions such as protein synthesis.

6. 6

   Describe the permeability of the outer mitochondrial membrane.

   Model answer

   The outer mitochondrial membrane is permeable to small molecules.

What is inside Levo

Six ways to work the same material.

Respiration revision questions

What does Respiration cover in OCR A-Level Biology?

6 subtopics: respiration, atp and the mitochondrion, glycolysis, the link reaction and the krebs cycle, oxidative phosphorylation and chemiosmosis, anaerobic respiration and respiratory substrates and the respiratory quotient. Each one has its own page with questions and model answers.

How is Respiration organised?

By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.