energy II Flashcards
1
Q
Citric cycle
A
Takes place in mitochondrial matrix
Pyruvate converted to acetyl CoA CO2 and NADH produced Acetyl CoA reacts with oxaloacetate to form citrate Citrate undergoes further reactions releasing 4 CO2 6 NADH 2 FADH2 2 GTP For each glucose molecule
2
Q
Regulation of entry into the citric acid cycle
A
Formation of acetyl CoA from pyruvate irreversible
Therefore glucose either oxidized to CO2 and energy production or fatty acid synthesis Enzyme involved is pyruvate hydrogenase: Inhibited by NADH and acetyl CoA Also regulated by phosphorylation by kinase and phosphate Phosphorylation inhibit this enzyme In muscle, pyruvate dehydrogenase is activated again via the action of a phosphate – this enzyme is stimulated by Ca2+ In liver, adrenaline increases calcium through the activation of a adrenergic receptor and IP3 In liver and adipose tissue, insulin stimulates the phosphate which funnels glucose to fatty aid synthesis
3
Q
Enzyme involved in citric acid cycle
A
Acetyl CoA reacts with oxaloacetate forming citrate using citrate synthase
Isocitrate into α-ketoglutarate using isocitrate dehydrogenase α-ketoglutarate is converted to succinyl CoA by the enzyme α-ketogluterate dehydrogenase Negative regulators NADH, ATP and Acetyl CoA Stimulated by ADP and pyruvate
4
Q
Beriberi
A
Deficiency in thiamine
Common where rice is a staple food Characterized by cardiac and neurological symptons Thiamine is a prosthetic group for pyruvate and α-ketogluterate dehydrogenase Neurological disorder are common as glucose is the primary source of energy
5
Q
NADH and FADH2
A
Eletron transport chain – responsible for producing ATP by oxidative phosphorylation
NADH will donate H atom which splits into proton and electron Proton pumped into intermembrane space and passed from complex to complex Looses energy as its passed along which is required to pump out the protons Pumped against their gradient Oxygen is reduced and water is formed Gradient generates ATP Every NADH forms 3 ATPs Every FADH2 forms 2 ATPs Every NADH pumps out 10 H+ Every FADH2 pumps out 6 H+
6
Q
ATP formation
A
H+ ions pumped across membrane through ATP synthase to generate ATP
Physiological reason where gradient is uncoupled from production of ATP is in new born infants In brown fat, protons are instead let through back into the matrix using a protein channel called thermogenin which generates heat instead of ATP
7
Q
OXPHOS disease
A
Degenerative disease
Caused by mutations in genes encoding proteins of ETC Lead to a number of symptoms including fatigue, epilepsy and dementia Dependent on mutations Metabolic consequence can be congenital lactic acidosis
8
Q
Regulation of ETC
A
When a cell requires ATP, the ETC is stimulated
Electron transport is tightly coupled to phosphorylation i.e. ADP to ATP Regulation uncoupling leads to the generation of heat
