Summary OCR A-Level Biology 5.2.2 Energy for Respiration
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Course
5.2.2
Institution
OCR
Book
A Level Biology A for OCR Student Book
These are detailed Revision Notes for Topic 5.2.2 of OCR A-Level (Respiration). They were written by me using a combination of the textbook and class notes. I will also be uploading the other topics and creating bundles.
Topics Included:
- Glycolysis
- Linking Glycolysis and the Krebs cycle
- ...
Respiration
18.1 Glycolysis
18.1 Glycolysis
- Outer mitochondrial membrane ~
separates the contents of the 18.2 linking glycolysis and the
mitochondria with the rest of the Krebs cycle
cell.
- Inner mitochondrial membrane ~ 18.3 Krebs cycle
contains electron transport chains 18.4 oxidative phosphorylation
and ATP synthase.
18.5 anaerobic respiration
- Cristae ~ projections of the inner
membrane that increase the surface area for oxidative phosphorylation. 18.6 respiratory substrates
- Matrix ~ contains enzymes and mitochondrial DNA
- Intermembrane space ~ proteins pumped into this space by the electron transport chain.
- Glycolysis occurs in the cytoplasm of the cell.
- Glucose is split into two 3-carbon pyruvate molecules.
- 2 net ATP, and 2 reduce NAD are produced.
Phosphorylation:
- 2 molecules of ATP are required.
- Glucose is phosphorylated to hexose biphosphate
Lysis:
- Hexose biphosphate splits into two triose phosphate (TP/ GALP) molecules
Phosphorylation:
- TP is phosphorylated by free inorganic phosphate
Dehydrogenation and formation of ATP:
- The TP molecules are dehydrogenated using dehydrogenase enzymes and reduced NAD is produced
- ATP is also released
18.2 Linking Glycolysis and the Krebs Cycle
- Pyruvate enters the mitochondrial matrix using a carrier protein.
- Pyruvate undergoes decarboxylation releasing CO2 and it is also oxidised resulting in the production of a
molecules of reduced NAD.
- This produces a 2-carbon compound called acetate which combines with coenzyme A to form
acetylcoA.
- Coenzyme A delivers the acetyl group to the Krebs cycle which is the next stage of respiration.
18.3 Krebs Cycle
- Takes place in the mitochondrial matrix
- Acetyl CoA delivers an acetyl group
- Acetyl (2 carbons) reacts with oxaloacetate (4 carbons) to produce citrate (6 carbons). Co A is released
to be used again in the link reaction
- Citrate is converted to a 4-carbon intermediate via a series of reactions that involve 2
decarboxylation’s and 2 dehydrogenation reactions producing 2CO2 and 2 oxidative decarboxylation
reactions producing 2 reduced NAD
- Oxaloacetate is regenerated via a substrate level phosphorylation of ADP to ATP, and 2 further
oxidation reactions producing a molecule of reduced NAD, ATP NADH + H+ FADH2 CO2
and a molecule of reduced FAD.
Glycolysis 2 2 0 0
- Coenzymes are required to transfer protons, electrons, and
functional groups between enzyme-catalysed reactions in Link reaction 0 2 0 2
respiration. NAD and FAD are both coenzymes. Krebs 2 6 2 4
Total 4 10 2 6
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