What is respiration?

3. What is respiration? ATP Respiration is the process by which organisms extract the energy stored in complex molecules and use it to generate adenosine triphosphate (ATP). In this way they obtain energy to fuel their metabolic pathways. ATP provides the immediate source of energy for biological processes such as active transport, movement and metabolism.

4. Types of respiration C6H12O6 + 6O2  6CO2 + 6H2O + 36ATP C6H12O6 2C2H5OH + 2CO2 + 2ATP ethanol C6H12O6 2C3H6O3 + 2ATP lactate During aerobic respiration, a respiratory substrate, e.g. glucose, is split in the presence of oxygen to release carbon dioxide and water. A large number of ATP molecules are produced, releasing the energy from the glucose. In anaerobic respiration, glucose is converted (in the absence of oxygen) to either lactate or ethanol. The ATP yield is low.

5. Where does respiration occur? Respiration occurs in all living cells. In eukaryotes the early stages of respiration occur in the cytoplasm. The later stages of respiration are restricted to the mitochondria. • Mitochondria contain highly folded inner membranes that hold key respiratory proteins (including the enzyme that makes ATP) over a large surface area. • Mitochondria provide an isolated environment to maintain optimum conditions for respiration. • Mitochondria have their own DNA and ribosomes, so can manufacture their own respiratory enzymes.

6. The structure of the mitochondria

7. An overview of respiration

9. Adenosine triphosphate + + + 30.5kJ  inorganic phosphate ATP H2O ADP ATP contains a sugar (ribose), a base (adenine) and three phosphate groups. adenine ribose phosphates When ATP is hydrolysed to form ADP and inorganic phosphate, 30.5kJ of energy are released.

10. Why ATP? Biological systems transfer the energy in glucose to ATP because unlike glucose… glucose ATP • ATP releases its energy instantly in a single reaction. • The hydrolysis of ATP releases a small amount of energy, ideal for fuelling reactions in the body.

11. Phosphorylation of ADP The addition of an inorganic phosphate group (Pi) to a molecule like ADP is called phosphorylation. ADP is phosphorylated during respiration. Two types of phosphorylation occur during respiration: 1. Substrate-level: glycolysis & Krebs cycle A single reaction involving the direct transfer of a phosphate group from a donor molecule to ADP. 2. Oxidative: electron transport chain A series of oxidation reactions that produce sufficient energy to form ATP from ADP and phosphate.

12. Coenzymes Coenzymes are molecules that bind with a specific enzyme or substrate, helping to catalyze a reaction. Breaking the bonds between coenzyme and product after a reaction is crucial, otherwise coenzyme concentration will drop, limiting respiratory rate. substrate enzyme coenzyme Three major coenzymes are used in respiration: • NAD (nicotinamide adenine dinucleotide) • CoA (coenzyme A) • FAD (flavine adenine dinucleotide)

13. NAD, FAD and coenzyme A NAD can accept a hydrogen molecule, forming reduced NAD (NADH). nicotinamide NAD+ + 2H NADH + H+ adenine This is used to regenerate ADP in the electron transport chain (ETC). ribose NAD Coenzyme Aaids the transition between glycolysis and the Krebs cycle, by converting pyruvate to acetyl coenzyme A. FAD,like NAD, can accept hydrogen to form reduced FAD (FADH2).

14. The molecules of respiration

16. The first stage of respiration: glycolysis

17. The stages of glycolysis

18. The fate of pyruvate

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