12.2.4
Chemiosmosis & Coenzymes
Chemiosmotic Theory
Chemiosmotic Theory
Chemiosmotic theory explains how oxidative phosphorylation and photophosphorylation work in relation to the production of ATP.
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Chemiosmosis
Chemiosmosis
- Chemiosmosis is the movement of ions across a membrane down an electrochemical gradient.
- ATP synthesis is an example of chemiosmosis because protons move across a membrane down an electrochemical gradient.
- Chemiosmosis happens in photophosphorylation and oxidative phosphorylation.


ATP synthase
ATP synthase
- ATP synthase is an enzyme found in the inner mitochondrial membrane of mitochondria, and in the thylakoid membrane of chloroplasts.
- Protons flow through ATP synthase, which releases energy needed to make ATP from ADP and P.
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Proton gradients
Proton gradients
- In mitochondria, protons are pumped from the matrix into the intermembrane space and in chloroplasts, protons are pumped from the stroma into the thylakoids.
- The energy needed to pump protons across the membrane comes from the electron transport chain.
- Pumping protons creates an electrochemical gradient. Protons move down the electrochemical gradient through ATP synthase, releasing energy.


Electron transport chain (ETC)
Electron transport chain (ETC)
- The electron transport chain (ETC) is a series of electron carrier proteins in the thylakoid membrane and the inner mitochondrial membrane.
- As electrons move down the ETC, they lose energy, which is used to pump protons across the membrane.
- In respiration, electrons come from the oxidation of NADH and FADH2.
- In photosynthesis, electrons come from the photoionisation of chlorophyll.
Coenzymes in Respiration
Coenzymes in Respiration
NAD, FAD, and Coenzyme A are important coenzymes in respiration:


NAD
NAD
- NAD is a coenzyme that can be reduced to NADH.
- NADH is produced in glycolysis (2 molecules per glucose), the link reaction (1 molecule per pyruvate), and the Krebs cycle (3 molecules per acetate).
- NADH gets oxidised in oxidative phosphorylation, releasing electrons for the ETC and protons.


FAD
FAD
- FAD is a coenzyme that can be reduced to FADH2.
- FADH2 is produced in the Krebs cycle (1 molecule per acetate).
- FADH2 gets oxidised in oxidative phosphorylation, releasing electrons for the ETC and protons.


Coenzyme A
Coenzyme A
- Coenzyme A binds with acetate in the link reaction to form acetyl coenzyme A, which goes on to enter the Krebs cycle.
- The link reaction links together glycolysis and the Krebs cycle.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
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