Cambridge International AS and A Level Biology Coursebook with CD-ROM
This section of my summarised notes covers the topic 'Energy and Respiration' in CIE 9700 Biology. These are simple, stylised note pack which are perfect for A2 biology revision. They cover the topic in the CIE syllabus with needed detail to ensure you get the perfect score.
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AS & A Level Biology 9700 : Respiration, Immunity and Infectious Diseases
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CIE
Biology
Unit 12 - Energy and Respiration (9700)
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Energy and Respiration
Metabolism
↬ all the biological reactions needed for an organism to stay alive
Anabolism: set of metabolic pathways that build larger molecules from smaller units
e.g. DNA replication, protein synthesis
Catabolism: set of metabolic pathways that break down molecules from smaller units e.g. lysis
ATP
Uses:
⇾ Anabolic reactions 3 phosphate groups
⇾ Active transport e.g Na/K pumps in
⇾ Nervous transmission
⇾ Mechanical work e.g. muscle contraction, cilia
⇾ Maintenance of body temperature Adenine
⇾ Phosphorylation in glycolysis
⇾ Bioluminescence/electrical discharge in some organisms
Universal energy source because: Ribose
• Small packets of energy, water-soluble (diffuses rapidly)
• Hydrolyses easily releasing 30.5 kJ/mol with only a single reaction
• Found in all organisms and used as an immediate energy donor from a variety of reactions
• Reversible reaction and high turnover
• Higher amount of reactions which yield than require ATP
• Links anabolic and catabolic reactions
Interconversion of ATP and ADP
Exergonic: Energy is released from hydrolysis of ATP → physical and chemical work
Endergonic: Synthesis of ATP requires energy → oxidative phosphorylation, ETC and oxidation of fuel
ATP + H2O ⇋ ADP + H3PO4
- When phosphate group is removed, ATP produces ADP and inorganic phosphate using ATPase.
- ATP synthase is used in the reversible reaction
- Some energy is converted to heat when more energy is released than required for cell reaction or
in respiration to make ATP
How ATP is produced
1. Substrate-level Phosphorylation
• Reorganising chemical bonds to add a phosphate from a high energy molecule to ADP with an
enzyme. E.g. in glycolysis and kreb’s cycle
2. Chemiosmosis
• Oxidative Phosphorylation- aerobic respiration at mitochondrial cristae - ETC (3H+ = 1ATP)
• Photophosphorylation- photosynthesis in chloroplast
SxTeri Notes Page 3
, Respiration
↬ The enzymatic release of energy from complex organic
molecules and the transfer to ATP in living cells. Cellular
respiration occurs as a series of linked, enzyme catalysed
reactions
C6H12O6 + 6O2 → 6CO2 + 6H2O
Co-Enzymes
↬ Act like enzymes (reusable, lower activation energy) but are not proteins
Nicotinamide Adenine Dinucleotide (NAD) and Flavin Adenine Dinucleotide (FAD): carrier molecules
taking hydrogens and their high energy electrons to another reaction e.g. ETC
Coenzyme A: acts as a carrier of acetyl groups (2C) transferring them from LR to KC
Glycolysis
In cell cytoplasm
• Reaction is lysis of 6C glucose into 2
molecules of 3C pyruvate
• Energy from ATP is needed to make glucose
more reactive by lowering activation energy.
This creates 6C fructose diphosphate which Phosphorylation
splits into 2 3C triose phosphate. This is then
oxidised to pyruvate
• Addition of inorganic phosphate group from
ATP is called phosphorylation
• Overall net gain of 2 ATP molecules per Glycolysis
glucose
• 2 NADH (red. NAD) also produced
• 4 ATP produced by fructose 1,6 diphosphate
• Hydrogen atoms are removed by
dehydrogenase enzymes
Number of molecules of Net ATP
gained
ATP NADH FADH
2 2 - 8
Red. NAD can generate 3 ATP molecules
Red. FAD can generate 2 ATP molecules
NB: Energy is also required for some of the processes so the energy yield can instead be NADH: 2.5
ATP and FADH: 1.5 ATP. This means there can be a total of 32 ATP instead of 38. Ex. To transport ADP
into the mitochondria and ATP into the cytoplasm
SxTeri Notes Page 4
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