3.3: Respiration

Coenzymes

Coenzymes

Enzymes that bind with other enzymes to help catalyse a reaction or help transfer molecules.

NAD

Coenzyme that can accept 1 proton/hydrogen and 2 electrons.

FAD

Coenzyme that can accept 2 protons/hydrogens and 2 electrons.

Coenzyme A (CoA)

Co-enzyme that transfers the 2 carbon acetate group, with chemical formula.

Glycolysis

First step of aerobic and anaerobic respiration. Occurs in the cytoplasm, and produces pyruvate, 4x ATP and 2x reduced NAD.

Glucose diphosphate

Created when glucose is phosphorylated by 2 phosphate groups, requiring 2 ATP molecules. Done to make glucose less reactive and less likely to leave the cell.

Oxidation

The gain of oxygen, but the loss of electrons/hydrogens.

Reduction

The loss of oxygen, but the gain of electrons/hydrogens.

Pyruvate

Created by the removal of phosphate and oxidation via NAD of the two triose phosphate molecules.

Link reaction

The second step in aerobic respiration, where glycolysis is linked to the Krebs’ cycle.

2 carbon acetate group

Left behind after the decarboxylation and dehydrogenation in the link reaction.

Acetyl coenzyme A (AcCoA)

Produced when coenzyme A combines with the 2 carbon acetate group, with chemical formula.

Krebs cycle

Third step of aerobic respiration. Occurs in the mitochondrial matrix, and releases energy from carbon bonds. Produces 3x reduced NAD, 1x reduced FAD, 1x ATP, 2x CO2.

6 carbon compound

Intermediate in the Krebs cycle that is decarboxylated, and then dehydrogenated, making a reduced NAD.

5 carbon compound

Intermediate in the Krebs cycle that is decarboxylated, and dehydrogenated - making a reduced NAD. It also creates ATP via substrate-level phosphorylation.

4 carbon compound

Intermediate that is dehydrogenated twice, producing a reduced FAD and reduced NAD. It then combines with AcCoA.

Decarboxylase

Enzyme used in decarboxylation, removes CO"2 from the -COOH groups.

Dehydrogenase

Enzyme used in dehydrogenation.

Cytochromes

Proteins bonded to iron, allowing for redox reactions to occur.

Electron transport chain

Occurs on the inner mitochondrial membranes, and is where oxidative respiration occurs. Also known as the cytochrome chain.

Electron carrier

A respiratory enzyme which passes electrons along a chain over proton pumps.

Respiratory enzymes

Proteins that are used in the electron transport chain.

Proton pump

A respiratory enzyme which pumps protons into the intermembrane space, powered by electrons.

Protein complex

A respiratory enzyme which is associated with ATP synthetase, and used by protons to travel via chemiosmosis to the mitochondrial matrix.

Nanomachine

A term used to describe the protein complexes which are driven via proton movement. A nanometer sized machine.

3

Amount of proton pumps powered, and therefore ATP created, by reduced NAD.

2

Amount of proton pumps powered, and therefore ATP created, by reduced FAD.

Electrochemical

Gradient created by the movement of protons across the cristea.

Rotor and stalk

Parts of the protein complex which rotate when protons diffuse through.

Catalytic head

Where the ATP is formed in the protein complex.

Oxygen

Comes from the blood and collects the protons and electrons to form water, known as the final hydrogen/electron acceptor.

Apoptosis

Programmed cell death, occurs by preventing proton gradients across cell membranes from forming.

Cyanide

Non-competitive inhibitor of oxygen, which prevents the removal of used protons and electrons. They then accumulate, destroying the proton gradient and preventing ATP synthesis. The cell dies quickly.

Chemiosmosis

The movement of molecules across an electro-chemical gradient.

Intermediates

Term used to describe the 3 molecules in the Krebs cycle, the 4, 5 and 6 carbon compounds.

Anaerobic

Type of respiration that occurs in the absense of oxygen, and only comprises of glycolysis and either alcohol fermentation or lactic acid fermentation.

Lactic acid

Form of anaerobic respiration fermentation. Pyruvate accepts hydrogen to create lactate, which regenerates NAD. Happens in animal’s muscle cells during vigorous exercise.

Alcohol

Form of anaerobic respiration fermentation. Pyruvate is decarboxylased, forming ethanal, which accepts hydrogen from NAD. This makes ethanol.

Lactate

Formed during lactic acid fermentation by pyruvate accepting hydrogen. Once oxygen becomes avaliable, it is respired into water and carbon dioxide and has it’s energy released. A build up of this can cause muscle fatigue.

Ethanal

Created by the decarboxylation of pyruvate, and is reduced to ethanol.

Ethanol

Created by the reduction of ethanal. An irreversible product, which can accumulate and reach toxic concentrations.

38

Maximum number of ATP created during aerobic respiration.

30-32

Average number of ATP created during aerobic respiration, due to proton leakage across the inner mitochondrial membrane, general molecule leakage and the ATP necessary to move pyruvate and NAD and FAD reduced.

2880kj

The amount of glucose created when combusted, therefore the theoretical available energy.

2

Amount of ATP produced during anaerobic respiration.

Lipid

Alternative respiratory pathway where glycerol and 3x fatty acids are converted to parts of the Krebs cycle and glycolysis. Used in tissues with a high blood supply, desert animals and when carbohydrates run out.

Glycerol

A constituent of lipid that is phosphorylated with ATP, dehydrogenated, and converted to triose phosphate.

Fatty acids

Three of these are consitituents of lipids. They are split into 2 carbon fragments that enter the Krebs cycle as AcCoA. The longer their hydrocarbon chain, the more ATP is made.

2 carbon fragments

Made from fatty acid chains and enter the Krebs cycle as AcCoA. The longer the fatty acid chain, the more carbon and hydrogen atoms, meaning more CO2, metabolic water and reduced NAD are produced.

Protein

Alternative respiratory pathway where carbon residue is used to replace pyruvate, AcCoA and other Krebs cycle intermediates. Only used once lipids and carbohydrates are fully used, such as during starvation. Mobilises tissue protein from the heart and the kidney.

Carbon residue

A constituent of protein that is converted to AcCoA, pyruvate or another Krebs cycle intermediate.

Intermembrane space - matrix

Movement of proteins through ATP synthetase in order to create ATP.