Mitochondrial Functions and Biogenesis Overview

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Questions and Answers

What percentage of mutant mtDNA typically leads to clinical symptoms?

70-80%

30-40%

50-60% (correct)

80-90%

Which protein is identified as the master regulator of mitochondrial biogenesis?

ATP Synthase

ERRa

NRF-1

PGC1a (correct)

What is the impact of increasing mitochondrial quantity on pathogenic mutations?

It makes no difference.

It only affects nDNA mutations.

It can worsen clinical symptoms.

It can alleviate symptoms of pathogenic mutations. (correct)

Which of the following factors require PGC1a as a co-activator for mitochondrial biogenesis?

NRF-1, NRF-2, and ERRa Signup and view all the answers

What type of mutations are often pathogenic in mtDNA?

Heteroplasmic mutations Signup and view all the answers

What is required for mitochondrial biogenesis besides the formation of new mitochondria?

Replication of mtDNA Signup and view all the answers

What role do transcription factors like NRF-1 and NRF-2 play in mitochondrial biogenesis?

They regulate the synthesis of mitochondrial proteins. Signup and view all the answers

Which of the following statements about mtDNA mutations is true?

Heteroplasmic mutations can lead to clinical symptoms. Signup and view all the answers

What is the primary target for small molecule-mediated inhibition mentioned in the context of cancer metabolism?

Hexokinase-2 Signup and view all the answers

Which of the following compounds is mentioned as a potential inhibitor of HK-2?

3-Br-Pyruvate Signup and view all the answers

Which pathway is implicated in the metabolism of glucose after its conversion to glucose-6P?

Pentose Phosphate Pathway Signup and view all the answers

What mechanism do clotrimazole and bifanazole use to affect HK-2?

Dislodge HK-2 from VDAC Signup and view all the answers

Which of the following is NOT involved in the glycolytic pathway as per the discussed content?

Chlorophyll Signup and view all the answers

What role does Tfam play in mitochondrial function?

Facilitates the transcription of mitochondrial DNA Signup and view all the answers

Which factors are activated by PGC1α to influence mitochondrial gene expression?

NRF-1 and NRF-2 Signup and view all the answers

Which complexes are involved in the mitochondrial respiratory apparatus?

Complexes I-V and ATP synthase Signup and view all the answers

What is the primary role of NRF-1 and NRF-2 in mitochondria?

To activate genes necessary for mitochondrial respiratory function Signup and view all the answers

Which process is NOT associated with mitochondrial DNA?

Protein synthesis Signup and view all the answers

What does the abbreviation TOM stand for in mitochondrial biology?

Translocase of the outer membrane Signup and view all the answers

Which component is primarily responsible for importing proteins into mitochondria?

TIM Signup and view all the answers

Which of these is NOT a function of mitochondrial DNA?

Regulating nuclear DNA Signup and view all the answers

What is the relationship between PGC-1α and mitochondrial biogenesis?

PGC-1α promotes mitochondrial biogenesis through other transcription factors Signup and view all the answers

What is the primary function of the mitochondrial membrane potential?

To drive ATP synthesis from ADP and inorganic phosphate Signup and view all the answers

What is the role of GSK3b in the regulation of PGC-1a?

It phosphorylates PGC-1a for degradation. Signup and view all the answers

Which of the following is a significant generator of oxidants in mitochondria?

H2O2 Signup and view all the answers

What happens to mitochondria during unbalanced fusion?

They become elongated. Signup and view all the answers

Which co-activator is primarily responsible for regulating mitochondrial biogenesis?

PGC-1a Signup and view all the answers

How do mitochondria contribute to programmed cell death?

By releasing cytochrome c. Signup and view all the answers

What is one function of mitochondrial dynamics in the cell?

To regulate energy needs. Signup and view all the answers

What effect does phosphorylation of PGC-1a at Threonine295 have?

Targets it for degradation. Signup and view all the answers

What is the principal role of AMPK in mitochondria?

Regulating energy balance and metabolism. Signup and view all the answers

What occurs during mitophagy?

Breakdown of cellular contents. Signup and view all the answers

What is an outcome of excessive production of oxidants in mitochondria?

Mitochondrial oxidative damage. Signup and view all the answers

What is the molecular structure of SRT-1720 characterized by?

Presence of sulfur and nitrogen atoms Signup and view all the answers

What functional groups are present in Resveratrol?

Hydroxyl groups Signup and view all the answers

Which compound features a methoxy group?

SRT-1720 Signup and view all the answers

Which structural feature is commonly associated with SRT-2104?

Multiple nitrogen substituents Signup and view all the answers

What distinguishes SRT-1720 from Resveratrol?

SRT-1720 has a more complex nitrogen structure Signup and view all the answers

How many nitrogen atoms are present in SRT-1720?

Two Signup and view all the answers

What role do hydrogen bonds play in the molecules described?

Stabilizing molecular structure Signup and view all the answers

What type of bonding is primarily involved with the sulfur atoms in SRT-1720?

Covalent bonds Signup and view all the answers

Which of the following statements is true about SRT-2104?

It contains oxygen as a part of functional groups. Signup and view all the answers

Which compound has a simpler structure compared to the others discussed?

Resveratrol Signup and view all the answers

Study Notes

Mitochondrial Functions Overview

Mitochondria are the powerhouses of the cell, responsible for ATP production.
They maintain cellular energy homeostasis.
Mitochondria generate reactive oxygen species (ROS), which can cause oxidative damage but also act as signaling molecules.
They are involved in cell death pathways through the release of messengers like cytochrome c.
Mitochondrial biogenesis is regulated by transcription factors under the control of PGC-1a, a co-activator that senses various physiological signals.
Mitochondria are dynamic organelles undergoing fusion and fission to meet energy needs.
Autophagy and mitophagy are processes that break down cellular contents, conserving energy and protecting against damaged biomolecules.

Mitochondrial DNA and Biogenesis

Many pathogenic mtDNA mutations are heteroplasmic, coexisting with wild-type mtDNA.
Clinical symptoms arise when the amount of mutant mtDNA surpasses a critical threshold (usually 50-60%).
Mitochondrial biogenesis, the process of forming new mitochondria, is regulated by PGC-1a.
PGC-1a activates nuclear transcription factors (NRF-1, NRF-2, and ERRa) involved in mitochondrial biogenesis.
NRF-1 and NRF-2 regulate the expression of genes crucial for mitochondrial respiratory apparatus maintenance.
Tfam, a transcription factor, facilitates transcription of the mitochondrial genome.
Protein import assembly machinery (TOM and TIM) facilitates the import of proteins into the mitochondria.

Regulation of PGC-1a

Glycogen synthase kinase 3b (GSK3b) negatively regulates PGC-1a by phosphorylating it, leading to its degradation.
AMPK and SIRT are positive regulators of PGC-1a.
AMPK activates PGC-1a through phosphorylation.
SIRT deacetylates PGC-1a, enhancing its activity.

Mitochondrial Dynamics

Mitochondria are dynamic organelles undergoing fusion and fission.
Fusion leads to mitochondrial elongation, while fission leads to fragmentation.
Resveratrol, SRT-1720, and SRT-2104 are compounds that can modulate mitochondrial dynamics.

Cancer, the Warburg Effect, and Hexokinase-2

The Warburg effect describes the increased glycolytic metabolism in cancer cells, even in the presence of oxygen.
Hexokinase-2 (HK-2), a key enzyme in glycolysis, is often overexpressed in cancer cells.
HK-2 binds to the voltage-dependent anion channel (VDAC) on the mitochondrial outer membrane, favoring glycolysis over oxidative phosphorylation.
Targeting this HK-2/VDAC interaction is a potential anticancer strategy.
Several compounds can disrupt this interaction, including clotrimazole, bifanazole, methyl jasmonate, and 3-Br-Pyruvate.
These compounds have the potential to inhibit tumor growth by redirecting cancer cells towards oxidative phosphorylation, reducing their energy supply.

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Description

This quiz explores the critical functions of mitochondria, including ATP production, energy homeostasis, and their role in cell death pathways. It also covers mitochondrial DNA, its mutations, and the regulation of mitochondrial biogenesis. Test your knowledge on this essential aspect of cell biology and the mechanisms behind mitochondrial dynamics.