Cellular respiration
We need energy to live, but how do we get it? We eat food and, via the process of respiration, we transfer the energy within this food to energy our bodies can use. Respiration is the chemical process of releasing energy from organic compounds. It is a series of enzyme-controlled reactions
in which energy is transferred to produce adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate (Pi).
Glycolysis Occurs in cytoplasm
Oxidation of glucose ( = one carbon atom) mitochondrion glucose to 2 ATP form pyruvate 2 ADP P – – P hexose bisphosphate KEY TO SYMBOLS Net products: Carbon atom: Coenzyme A: • 2 ATP Phosphate group: P • 2 reduced NAD P – P – triose phosphate • 2 pyruvate NAD 2 ADP reduced 2 ATP Is oxygen YES NAD pyruvate AEROBIC RESPIRATION available? NO Occurs in mitochondrial matrix LINK REACTION
CYTOPLASM Removal of hydrogen and carbon dioxide from pyruvate (decarboxylation)
pyruvate Net products: NAD • 2 reduced NAD ANAEROBIC reduced • 2 CO2 RESPIRATION Occurs in cytoplasm CO2 NAD • 2 acetyl CoA acetyl Respiration that uses group final electron acceptors acetyl CoA other than oxygen
Net ATP yield: 2 ATP (from glycolysis) Occurs in mitochondrial matrix KREBS CYCLE
Plants (and some micro- Animals (and some micro-organisms, Complete oxidation of acetyl CoA organisms, e.g. yeast): e.g. Lactobacillus): Net products pyruvate pyruvate (two turns of cycle): reduced NAD reduced NAD • 6 reduced NAD NAD NAD • 2 reduced FAD • 2 ATP (from GTP) ethanol lactate acetyl CoA • 4 CO2
CO2
citrate
oxaloacetate CO2 NAD reduced NAD reduced NAD NAD
ELECTRON CO2 TRANSPORT CHAIN INTERMEMBRANE Space GDP ADP INNER ATP reduced FAD NAD GTP ATP Using electron transport to power MEMBRANE CYTOCHROME c SYNTHASE FAD reduced NAD + the transport of protons (H+), H+ H+ H leading to the production of ATP H+
– 2e – – – MATRIX Net ATP yield: 2e 2e 2e The amount of ATP made per molecule of glucose 2e– CRISTA varies according to conditions. In theory, each can reduced reduced yield a maximum of 38 ATP, but around 30 is more likely. NAD FAD + ATP + H + H H Pi + Glycolysis and Krebs cycle 4 ATP NAD INNER MEMBRANE 1/2 O + 2e– + 2H+ ADP 10 x reduced NAD (electron transport chain) 30 atp 38 ATP FAD 2 2 x reduced FAD (electron transport chain) 4 atp H O 2 OUTER MEMBRANE CYTOCHROME OXIDASE MITOCHONDRIAL INterMEMBRANE SPACE MATRIX GLOSSARY
Acetyl CoA: An intermediate formed ATP (adenosine triphosphate): A Cytochrome oxidase: Terminal FAD (flavine adenine dinucleotide): GTP (guanosine triphosphate): A NAD (nicotinamide adenine Oxidative phosphorylation: A process in the link reaction by the joining of molecule found in all living cells that is component of the electron transport A coenzyme that acts as a hydrogen molecule produced during the Krebs dinucleotide): A coenzyme that acts as in which mitochondria make ATP using coenzyme A (CoA) and a two-carbon involved in the transfer of energy. Most chain, which oxidises cytochrome c. This acceptor in respiration. FAD accepts cycle that donates a phosphate group a hydrogen acceptor in respiration. NAD the energy released when electrons are compound. This enters the Krebs cycle. of a cell’s ATP is made during respiration. is where oxygen is actually consumed, by hydrogen in the Krebs cycle and becomes to ADP to make ATP. It is also very accepts hydrogen in the link reactions transported from reduced NAD and FAD ADP (adenosine diphosphate): A ATP synthase: An enzyme that catalyses acting as the final electron acceptor and reduced. In the electron transport chain, important elsewhere in the cell. and the Krebs cycle and becomes to oxygen in the electron transport chain. molecule found in all living cells that is the synthesis of ATP in oxidative being converted to water. it transfers electrons from this hydrogen. Hydrogen carrier: A molecule that reduced. In the electron transport chain, Redox reaction: When one substance involved in the transfer of energy. phosphorylation. Decarboxylation: A chemical reaction GDP (guanosine diphosphate): A can accept hydrogen atoms or ions it transfers electrons from this hydrogen. is reduced and another oxidised. It is produced when a phosphate group Coenzyme: Small non-protein organic that releases carbon dioxide (CO2). molecule converted to GTP during and donate them to another carrier. OILRIG: A mnemonic for redox reactions Reduction: The gain of electrons or is removed from ATP, a process that molecules that bind to and are required Electron carrier: A molecule that can the Krebs cycle. Hydrogen carriers include NAD and FAD. – oxidation is loss (of electrons or hydrogen, or the loss of oxygen by releases energy. for the activity of their associated accept one or more electrons and Glycolysis: The splitting of sugar. This Mitochondrion: A rod-shaped body that hydrogen), reduction is gain (of electrons a molecule, atom or ion. or hydrogen). Aerobic: Using oxygen. enzyme. An example is coenzyme A donate them to another in an electron process, in which glucose is oxidised, takes supplies chemical energy to eukaryotic Substrate-level phosphorylation: Anaerobic: Without oxygen. (CoA), which combines with a two- transport chain. They include NAD, FAD place in the cytoplasm. It is the first stage cells (plural: mitochondria). Oxidation: The loss of electrons or A process that makes ATP through carbon compound during the link and the cytochromes. of both aerobic and anaerobic respiration. hydrogen (called dehydrogenation), or the the donation of a phosphate group reaction to form acetyl CoA. gain of oxygen by a molecule, atom or ion. from an intermediate directly to ADP, for example during glycolysis.
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