12 · Energy and Respiration
Cambridge A Level Biology — Full F-drive source: 12 · Energy and Respiration — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions
5 min read 9 parts Lesson 16 of 18 Unit quiz
Lesson summary
12. Energy and Respiration: overview — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Outline why cells need ATP, how it is made in aerobic respiration, and what happens without oxygen.Transport — active transport such as the sodium-potassium pump, and exocytosis.Ana…
- Anabolic reactions
- Temperature
- Energy currency
- Hydrolysis
- Cells cannot store large amounts of ATP
- Intermembrane space
Section 1 of 9Why cells need ATP
Transport
- Transport active transport such as the sodium-potassium pump, and exocytosis.
Anabolic reactions
- Anabolic reactions making DNA from nucleotides and proteins from amino acids.
Movement
- Movement movement of chromosomes on the spindle and muscle contraction.
Temperature
- Temperature maintaining body temperature in mammals and birds.
Energy currency
- ATP is a small soluble molecule that carries energy to where it is needed.
Section 2 of 9Structure and hydrolysis of ATP
Structure and hydrolysis of ATP
Structure
- Structure ribose, adenine and three phosphate groups.
Hydrolysis
- ATP is broken down to ADP and Pi by ATPase, releasing about 30.5 kJ mol-1.
Synthesis
- ADP and Pi are joined by a condensation reaction, which needs energy.
Cells cannot store large amounts of ATP
- Cells cannot store large amounts of ATP it is made as and when needed.
Section 3 of 9Four stages of aerobic respiration
| Stage | Location | What happens |
|---|---|---|
| Glycolysis | Cytoplasm | Glucose is phosphorylated and split to 2 pyruvate; net 2 ATP and 2 reduced NAD |
| Link reaction | Mitochondrial matrix | Pyruvate is decarboxylated and dehydrogenated to acetyl CoA, with CO2 and reduced NAD |
| Krebs cycle | Mitochondrial matrix | Acetyl CoA joins oxaloacetate to form citrate; decarboxylation and dehydrogenation give CO2, reduced NAD, reduced FAD and ATP |
| Oxidative phosphorylation | Inner mitochondrial membrane | Electron transport chain and chemiosmosis make most of the ATP; oxygen forms water |
Section 4 of 9The mitochondrion
Membranes
- Membranes two membranes, with the inner membrane folded into cristae.
Cristae
- Cristae give a large surface area for electron carriers and ATP synthase.
Matrix
- Matrix contains enzymes, ribosomes and circular mitochondrial DNA.
Intermembrane space
- Intermembrane space has a low pH because of its high proton concentration.
Section 5 of 9Energy value of substrates
Lipid
- 39.4 kJ per gram, the highest.
Protein
- 17.0 kJ per gram.
Carbohydrate
- 15.8 kJ per gram.
Reason
- Reason more hydrogen atoms per gram give a larger proton gradient and more ATP.
RQ
- RQ the ratio of CO2 produced to O2 taken in; it helps identify the substrate respired.
Section 6 of 9When oxygen is lacking
Electron transport chain
- Electron transport chain stops because there is no final electron acceptor.
Reduced NAD and FAD
- Reduced NAD and FAD cannot be re-oxidised, so the Krebs cycle also stops.
Fermentation
- Fermentation re-oxidises NAD so glycolysis can continue, giving 2 ATP per glucose.
Animals
- Animals pyruvate is reduced to lactate.
Yeast and plants
- Yeast and plants pyruvate is converted to ethanol and CO2.
Section 7 of 9More from the specification
More from the specification
Calorimetric combustion analysis
- Calorimetric combustion analysis measuring water temperature rise produced by burning fuels provides an experimental means to compute molar enthalpy of combustion.
Respiratory Quotient Formula
- The respiratory quotient is defined by the equation RQ = / (volume of oxygen consumed), indicating the type of substrate respired by living organisms.
- (volume of carbon dioxide produced)
Respiratory Quotient of Metabolic Substrates
- Aerobic respiration of carbohydrates produces an RQ of 1.0,
- whereas respiration of lipids yields an RQ of approximately 0.7 because lipids contain fewer oxygen atoms and require more external oxygen per mole of CO2 released.
Respirometer and Manometer Setup
- A simple respirometer uses a U-tube fluid manometer to measure changes in gas volume as respiring organisms consume oxygen, with potassium hydroxide absorbing evolved carbon dioxide.
Chemiosmotic Proton Gradient
- In mitochondrial respiration, electron transport chains pump protons across the inner mitochondrial membrane, generating an electrochemical gradient that drives ATP synthesis.
Substrate-linked phosphorylation
- Direct transfer of a phosphate from a substrate to ADP.
Volume
- The amount of cytoplasm needing supplies and producing waste.
Organism
- A living thing, such as a plant or an animal.
Carbon
- Element with four valence electrons that forms the backbone of organic molecules.
Lipids
- Concentrated energy, insulation, cell membranes.
Manometer
- U-tube whose fluid moves as gas volume changes.
Respiratory quotient
- CO_{2} produced divided by O_{2} consumed.
Anaerobic respiration
- Respiration without oxygen, releasing much less energy per glucose molecule.
Section 8 of 9Key terms
| Term | Meaning |
|---|---|
| ATP | Molecule that carries energy for cell processes. |
| Glycolysis | Breakdown of glucose to pyruvate in the cytoplasm. |
| Krebs cycle | Cycle of reactions in the matrix releasing CO2 and reduced coenzymes. |
| Oxidative phosphorylation | ATP production using the electron transport chain and chemiosmosis. |
| Coenzyme | Non-protein molecule, such as NAD, that helps enzymes. |
| Chemiosmosis | Movement of protons through ATP synthase to make ATP. |
Section 9 of 9Exam technique
1
Saying respiration makes energy — it transfers energy to ATP.
2
Thinking glycolysis needs oxygen — it takes place anaerobically in the cytoplasm.
3
Putting the Krebs cycle on the cristae — it is in the matrix.
4
Confusing respiration with breathing — respiration is the cellular release of energy.
Last updated: