Lecture 2.2 - energy production (carbohydrate 3 and lipids)

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Questions and Answers

What is the primary function of ATP synthase complex in the mitochondrial matrix?

To generate ATP from ADP and Pi (correct)

To pump H+ ions into the intermitochondrial space

To facilitate the electron transport chain

To regulate mitochondrial DNA replication

What is the effect of high ATP levels on oxidative phosphorylation and electron transport?

Decreased ATP synthesis and electron transport (correct)

Increased ATP synthesis and electron transport

No effect on ATP synthesis and electron transport

Increased electron transport but decreased ATP synthesis

What is the primary consequence of mitochondrial dysfunction in highly-energetic tissues?

Increased ATP synthesis and energy production

Increased lactate production and glycolysis

Increased mitophagy and mitochondrial biogenesis

Decreased ATP synthesis and energy production (correct)

What is the function of uncoupling agents, such as UCP 1-5, in the electron transport chain?

To uncouple electron transport from ATP synthesis, producing heat Signup and view all the answers

What is the effect of cyanide on the electron transport chain and glycolysis?

Cyanide inhibits complex 4 of the electron transport chain and inhibits glycolysis Signup and view all the answers

What is the primary characteristic of lipids in terms of solubility?

They are generally insoluble in water but soluble in organic solvents Signup and view all the answers

What is the effect of low ADP levels on the electron transport chain and ATP synthesis?

Decreases electron transport and ATP synthesis Signup and view all the answers

What is the consequence of mitochondrial dysfunction in terms of patient safety?

Patients require rapid treatment to avoid death due to energy depletion Signup and view all the answers

What is the primary function of the electron transport chain in the mitochondria?

To transfer electrons to molecular oxygen, generating a proton-motive force Signup and view all the answers

Which of the following is a characteristic of oxidative phosphorylation?

It conserves energy from reduced carriers into ATP Signup and view all the answers

What is the result of proton translocation during electron transport?

The generation of a proton-motive force Signup and view all the answers

What is the role of ATP utilisation in the regulation of the citric acid cycle?

It decreases the ATP/ADP ratio Signup and view all the answers

What is the effect of uncoupling agents on oxidative phosphorylation?

They decrease ATP synthesis Signup and view all the answers

What is the site of ATP synthesis during oxidative phosphorylation?

The inner mitochondrial membrane Signup and view all the answers

What is the result of a high NADH/NAD+ ratio in the citric acid cycle?

A high-energy signal Signup and view all the answers

What is the role of oxygen in the electron transport chain?

It is the final electron acceptor Signup and view all the answers

What is the primary function of the tricarboxylic acid cycle in the context of carbohydrate catabolism?

To break the C-C bond in acetate and oxidize the C-atoms to CO2 Signup and view all the answers

What is the consequence of a deficiency in pyruvate dehydrogenase (PDH) in carbohydrate catabolism?

Lactic acidemia, leading to Leigh's disease Signup and view all the answers

What is the reactant required for the conversion of pyruvate to acetyl-CoA?

Pyruvate dehydrogenase (PDH) Signup and view all the answers

What is the byproduct of the tricarboxylic acid cycle that is used in biosynthesis?

Precursors for biosynthesis Signup and view all the answers

What is the energy status of the cell that regulates the conversion of pyruvate to acetyl-CoA?

Sensitive to the energy status of the cell Signup and view all the answers

What is the location of the tricarboxylic acid cycle in the context of carbohydrate catabolism?

Mitochondrial matrix Signup and view all the answers

Study Notes

Stage 3: Tricarboxylic Acid Cycle (TCA Cycle)

Occurs in mitochondria
Requires NAD+, FAD, and oxaloacetate
Breaks the C-C bond in acetate (as acetyl CoA) and oxidizes the C-atoms to CO2, which is released
H+ and e- removed from acetate are transferred to NAD+ and FAD (NADH and FADH2 produced)
Requires oxygen
Produces ATP and GTP (energy)
Some reactions are irreversible

Stage 4: Oxidative Phosphorylation (OXPHOS)

Converts chemical energy from nutrients into ATP
Energy conserved in reduced carriers (NADH and FADH2) is used to synthesize ATP
Two processes: electron transport and ATP synthesis
Occurs inside the mitochondria, specifically in the invaginations of the inner membrane
Electron transport: transfer of electrons to molecular oxygen mediated by four specialized complexes (I-IV)
Electrons come from NADH and FADH2, shuttled to the intermembrane space
Proton translocation results in "proton-motive force" (also referred to as electro-chemical potential)
Requires oxygen: reduced to water at complex IV

Regulation of OXPHOS

Normally oxidative phosphorylation and electron transport are tightly coupled
Both regulated by mitochondrial ATP
High ATP = Low ADP
When ADP is low: no substrate for ATP synthase, inward flow of H+ stops, and concentration of H+ in the intermitochondrial space increases
Prevents further H+ pumping, stopping electron transport
Reverses with low ATP

Clinical Relevance

Mitochondrial dysfunction: loss of efficiency in the electron transport chain and reductions in the synthesis of ATP
Linked to most human conditions in highly-energetic tissues (e.g., brain, neurodegeneration)
Mitochondrial DNA mutations: abnormal components of the respiratory chain
Uncouplers and inhibitors: uncoupling agents (UCP 1-5) important for heat production, inhibitors (poisons) stop ATP and heat production

Lipids

Generally insoluble in water (hydrophobic) but soluble in organic solvents
Most contain only C, H, and O (phospholipids also contain P and N)
More reduced than carbohydrates

Catabolism of Carbohydrates

Stage 2: pyruvate is converted to acetyl CoA by pyruvate dehydrogenase (PDH) - regulated allosterically
Reaction is irreversible (pyruvate loses one C-atom)
Sensitive to the energy status of the cell
Deficiencies of PDH: X-linked dominant disorder leading to lactic acidemia - Leigh's disease (necrotizing encephalopathy)

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Description

This quiz covers the stages of cellular respiration, focusing on the tricarboxylic acid cycle and oxidative phosphorylation processes, including the breakdown of acetate and the production of ATP and GTP.