Metabolism, ATP and Cellular Respiration

Define metabolism

Sum of all the biochemical reactions that occur in the body

Define catabolism

Catabolic reactions that break down larger/complex organic molecules into smaller ones (releases energy = exergonic)

Define anabolism

Anabolic reactions that use simple molecules to make larger/complex organic molecules (consumes energy = endergonic)

Define glycogenesis

Synthesis of glycogen (storage of glucose) when blood glucose levels are high

• trigger by insulin

• glycogen = glucose molecules joined together

• stored in liver and muscle cells

• anabolic reaction

Define glycogenolysis

Break down of glycogen and release into bloodstream when blood glucose levels are low

• triggered by glucagon and cortisol

• only the glycogen stored in hepatocytes (liver cells) are broken down

Define gluconeogenesis

Synthesis of glucose from non-carbohydrate sources when blood glucose levels are low

• triggered by cortisol and glucagon

• generates ATP from amino acids, lactic acid and glycerol

Define ATP

Adenosine triphosphate - transfers energy from catabolic reactions to power anabolic reactions

Describe ATP resynthesis

ATPase (enzyme that catalyses hydrolysis) hydrolyses ATP into ADP + phosphate group (releases stored energy in phosphate bond)

ATP synthesis catalyses the re-addition of a phosphate group to ADP to reform ATP

Define cellular respiration

Oxidation of glucose (removal of electrons and H+ ions)

Define glycolysis

Break down of glucose

• occurs in cytosol

• anaerobic

• catabolic reaction - uses 2 ATP to produce 4 ATP (net of 2 ATP)

Describe glycolysis process

Glucose → three pyruvic acids

Lack of O2 → anaerobic respiration → pyruvic acid becomes lactic acid (stored in liver and muscle cells, converted back into pyruvic when O2 is present)

Presence of O2 → aerobic respiration → enters mitochondria, converted into acetyl coenzyme A

Describe Kreb’s cycle (citric acid cycle)

Aerobic process

Acetyl CoA enters Kreb’s cycle via mitochondria

Describe the electron transport chain

Aerobic process

Occurs on the inner mitochondrial membrane

Integral membrane proteins (electron carriers) form a chain in membrane which electrons are passed along to generate ATP

Generates water and 26-28 ATP molecules

How much ATP is produced at each step of cellular respiration and what is the total yield

Glycolysis = 2 ATP

Kreb’s cycle = 2 ATP

Electron transport chain = 26-28 ATP

Total yield = 30-32 ATP

State the equation for cellular respiration

Glucose + oxygen → water + carbon dioxide + ATP + heat

C6H12O6 + 6O2 → 6H2O + 6CO2 + 30-32ATP + heat