HSS2305-L6

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Questions and Answers

How many ATP molecules are produced per Acetyl-CoA in the fatty acid oxidation process?

4 ATP

2 ATP

1 ATP (correct)

3 ATP

Which compound is primarily condensed with oxaloacetate (OAA) to start the TCA cycle?

Malate

Citrate

Acetyl-CoA (correct)

Fumarate

What is the role of NADH and FADH2 produced in the TCA cycle?

To donate electrons to the electron transport chain (correct)

To directly produce ATP

To regenerate oxaloacetate

To facilitate glycolysis

Which process directly converts pyruvate into Acetyl-CoA before it enters the TCA cycle?

Pyruvate Dehydrogenase reaction Signup and view all the answers

What is produced during the oxidation of one molecule of Acetyl-CoA in terms of reducing equivalents?

3 NADH and 1 FADH2 Signup and view all the answers

In which part of the cell does β-oxidation occur?

Mitochondrial matrix Signup and view all the answers

Which step signifies the removal of carbon atoms during the TCA cycle?

Release of CO2 Signup and view all the answers

What is the final outcome of the electron transport chain in mitochondria?

Formation of water and ATP Signup and view all the answers

What is the primary molecule produced during glycolysis from glucose?

Pyruvate Signup and view all the answers

What is the primary role of the electron transport chain in oxidative phosphorylation?

To generate a proton gradient across the inner mitochondrial membrane Signup and view all the answers

How many molecules of ATP can theoretically be produced from one molecule of glucose during cellular respiration?

36 molecules Signup and view all the answers

What role does Pyruvate Dehydrogenase play in mitochondrial metabolism?

Catalyzes the conversion of pyruvate into Acetyl-CoA Signup and view all the answers

Which component of the electron transport chain uses O2 as a substrate?

Complex IV Signup and view all the answers

Which of the following correctly describes the role of mitochondria in calcium homeostasis?

Mitochondria regulate cellular calcium levels influencing signal transduction pathways. Signup and view all the answers

Which statement about FADH2 is correct in the context of ATP yield?

It yields 2 ATP molecules upon oxidation Signup and view all the answers

Which process is primarily indicated by the term 'cataplerosis' in relation to mitochondrial function?

The synthesis of metabolic precursors from intermediates Signup and view all the answers

What is the net energy yield from one molecule of glucose during glycolysis?

2 ATPs Signup and view all the answers

What is the primary function of ATP synthase in the mitochondria?

To form ATP using the proton gradient generated by the electron transport chain Signup and view all the answers

What is the result of the mitochondrial membrane potential during oxidative phosphorylation?

It provides the energy for proton re-entry into the matrix Signup and view all the answers

Which complexes are involved in pumping protons into the intermembrane space?

Complexes I, III, and IV Signup and view all the answers

What is one of the major roles of mitochondria beyond ATP production?

Calcium storage and regulation Signup and view all the answers

In cell signaling pathways, how is energy from the mitochondrial processes typically utilized?

To regulate enzyme activity via ATP binding Signup and view all the answers

Which statement is true regarding the flow of electrons in the electron transport chain?

Electrons flow from NADH and FADH2 to oxygen Signup and view all the answers

What is the net ATP yield from mitochondrial NADH during cellular respiration?

3 ATP/NADH Signup and view all the answers

Which process significantly impacts the net ATP yield from cytosolic NADH?

Cost of transporting NADH into the mitochondria Signup and view all the answers

In oxidative phosphorylation, what is the typical ATP yield from FADH2?

2 ATP/FADH2 Signup and view all the answers

What role does ATP play in cell signaling?

Acts as a substrate for kinases Signup and view all the answers

Which of the following statements is true regarding the function of ATP?

It alters the activity of proteins through phosphorylation. Signup and view all the answers

What mechanism does the mitochondria utilize for anabolic processes?

Cataplerosis Signup and view all the answers

How much free energy is released during the hydrolysis of one mole of ATP?

~7.3 kcal/mole Signup and view all the answers

Which of the following statements regarding oxidative phosphorylation is incorrect?

Each proton transported results in ATP formation. Signup and view all the answers

What is the primary purpose of ATP in active transport mechanisms?

To facilitate movement against concentration gradients Signup and view all the answers

What is the range of ATP production typically observed per glucose molecule during glycolysis and oxidative phosphorylation combined?

30-32 ATP/glucose Signup and view all the answers

What primarily regulates the permeability of the inner mitochondrial membrane?

Uniport and antiport systems Signup and view all the answers

What is the main role of mitochondrial DNA (mtDNA) in the context of energy production?

Encoding proteins for the electron transport chain Signup and view all the answers

How does the presence of cristae in the inner mitochondrial membrane affect ATP production?

Increases surface area for electron transport chain complexes Signup and view all the answers

During oxidative phosphorylation, which of the following processes occurs?

Pumping of protons across the inner membrane Signup and view all the answers

Which process allows for the selective removal of dysfunctional mitochondria within cells?

Mitophagy Signup and view all the answers

What role do ribosomes in the mitochondrial matrix play?

Synthesize mitochondrial proteins and RNA Signup and view all the answers

What key function does the porin (VDAC) protein serve in mitochondria?

Facilitating the transport of metabolites across the outer membrane Signup and view all the answers

How does mitochondrial fission influence cellular metabolism?

It affects mitochondrial length and interconnection Signup and view all the answers

What is a primary consequence of maternal inheritance of mitochondrial DNA?

Tracking evolutionary history of populations Signup and view all the answers

Which metabolic process occurs within the mitochondrial matrix?

TCA cycle Signup and view all the answers

Study Notes

Carbohydrate (Fatty Acid) Metabolism in the Mitochondria

Mitochondria are the powerhouses of the cell, involved in vital processes including energy production (ATP), anabolism, calcium homeostasis, and apoptosis.
TCA/Krebs/Citric Acid Cycle is a key step in cellular respiration, occurring in the mitochondrial matrix.
- The cycle starts with the condensation of Acetyl-CoA (2 Carbons) with oxaloacetate (OAA; 4 C) to form citrate (6 C).
- During the cycle, 2 carbons are lost as CO2, regenerating OAA.
- The cycle produces 4 pairs of electrons carried by NADH and FADH2.
- These electron carriers are then transported to the electron transport chain.
Glycolysis is an anaerobic pathway that occurs in the cytosol, breaking down glucose into pyruvate.
- It produces 2 ATP, 2 NADH, and 2 Pyruvate per glucose molecule.
- Pyruvate can be further catabolized aerobically or anaerobically.
PDH (Pyruvate Dehydrogenase) is a multienzyme complex that transforms and transports pyruvate into the mitochondrial matrix.
- It decarboxylates pyruvate to form a 2-carbon acetyl group.
- The acetyl group is transferred to Coenzyme A (HS-CoA) to produce Acetyl-CoA.
- This process requires NAD+ and produces NADH.
- The overall reaction is: Pyruvate + HS-CoA + NAD+ → Acetyl-CoA + CO2 + NADH + H+
β (Fat)-Oxidation is a stepwise process that breaks down fatty acids in the mitochondrial matrix.
- It produces Acetyl-CoA, which can then enter the TCA cycle.
- It also generates reducing equivalents (NADH and FADH2).

Oxidative Phosphorylation

Electron Transport Chain is located in the inner mitochondrial membrane, utilizing electrons from NADH and FADH2.
- These electrons pass through a chain of protein complexes (I-IV).
- Complex I (NADH dehydrogenase) and Complex II (Succinate Dehydrogenase) receive electrons from NADH and FADH2, respectively.
- Electron transport through the chain pumps H+ ions from the mitochondrial matrix to the intermembrane space.
- This generates a proton gradient and mitochondrial membrane potential.
- Oxygen is consumed at Complex IV (Cytochrome oxidase) as the final electron acceptor.
ATP Synthase (Complex V) uses the potential energy from the proton gradient to produce ATP through chemiosmosis.
- Each NADH yields approximately 2-3 ATP molecules.
- Each FADH2 yields approximately 2 ATP molecules.
- The theoretical yield of ATP per glucose molecule is 36.
- However, actual yield is typically lower, between 28-32 ATP per glucose.

ATP

Adenosine Triphosphate (ATP) is the universal energy currency of the cell.
- It stores chemical energy that can be released through hydrolysis, forming ADP (adenosine diphosphate) and inorganic phosphate.
- This reaction releases approximately 7.3 kcal/mole of free energy.
- ATP powers essential cellular processes:
  - Active transport of molecules and ions
  - Nerve impulses
  - Maintenance of cell volume
  - Protein phosphorylation
  - Muscle contraction
  - Cilia and flagella beating
  - Bioluminescence

ATP: Other Functions

Cell Signalling: ATP serves as a substrate in signal transduction pathways by kinases, which phosphorylate proteins and lipids. ATP is also utilized by adenylyl cyclase to produce cyclic AMP, a second messenger molecule.
Anabolism: ATP is a monomer used in the synthesis of RNA and DNA (after conversion to deoxyATP).

Cataplerosis

Cataplerosis refers to the use of metabolic intermediates from the TCA cycle for anabolic processes.
- These intermediates are utilized in the synthesis of various anabolic molecules.
- Example: Oxaloacetate can be used for gluconeogenesis.
Mitochondrial Matrix contains circular DNA (mtDNA), ribosomes, and enzymes essential for the TCA cycle and other metabolic processes.

Mitochondrial Structure

Mitochondrial Membranes are highly proteinaceous, containing approximately 50% protein in the outer membrane and 75% in the inner membrane.
Outer Membrane:
- Highly permeable due to the presence of Porin, a large pore-forming protein.
- Allows the exchange of ions, small molecules, NADH, and ATP.
Inner Membrane:
- Contains the electron transport chain and cristae, which are invaginations or folds that increase the surface area.
- Largely impermeable to most molecules, except for:
  - O2
  - CO2
  - H2O
- Contains specialized transport systems (uniports and antiports) for specific metabolites.
- The regulated permeability is key for the bioenergetics of the cell.
Matrix:
- The innermost compartment of the mitochondria.
- Contains:
  - mtDNA
  - Ribosomes
  - Enzymes for the TCA cycle, β-oxidation, and other metabolic pathways.
- Can synthesize RNA and proteins.

Mitochondrial DNA (mtDNA)

Encodes for 13 proteins, all part of the electron transport chain.
Multiple copies of mtDNA exist within each cell, typically more than nuclear genes.
Inherited primarily from mothers through the oocyte mitochondria.
Used to track human migration and evolution because it mutates at a faster rate than nuclear DNA.
Single nucleotide polymorphisms can be used to study maternal ancestry.
However, most mitochondrial proteins are encoded by nuclear DNA, not mtDNA.

Mitochondrial Dynamics

Mitochondrial Biogenesis: the creation of new mitochondria.
Mitophagy: the selective degradation of old or dysfunctional mitochondria via autophagy.
- Autophagy involves lysosomal recycling of cellular components.
Fusion: mitochondria can fuse with one another, creating larger and interconnected networks.
Fission: mitochondria can divide into two daughter mitochondria.
- The endoplasmic reticulum (ER) might play a role in inducing fission.
- Fusion and fission are crucial for maintaining the number, length, and interconnection of mitochondria.

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Description

Explore the intricate processes of carbohydrate metabolism, particularly the roles of mitochondria in energy production through the TCA cycle and glycolysis. This quiz covers major concepts like the transformation of Acetyl-CoA and the importance of NADH and FADH2 in cellular respiration.