Mitochondria: Structure, Function, and Role in Energy Production

Question 1

Which of the following is NOT a primary function of mitochondria in cells?

Accepted Answer

Lipid synthesis

Answer

Energy production

Answer

Calcium storage

Answer

Apoptosis regulation

Question 2

How does oxidative phosphorylation contribute to the formation of a proton gradient across the inner mitochondrial membrane?

Accepted Answer

The electron transport chain pumps protons across the inner mitochondrial membrane, creating a higher concentration of protons in the intermembrane space.

Answer

Oxidative phosphorylation occurs in the mitochondrial matrix and directly synthesizes ATP.

Answer

The electron transport chain uses ATP to pump protons across the inner mitochondrial membrane.

Answer

Oxidative phosphorylation is independent of the electron transport chain.

Question 3

Identify the key structural components of mitochondria and explain how they contribute to its role in cellular respiration.

Accepted Answer

Double membrane, matrix, and cristae

Answer

Single membrane, stroma, and thylakoids

Answer

Ribosomes, cytoplasm, and Golgi apparatus

Answer

Nucleus, chromosomes, and ribosomes

Question 4

To comprehensively evaluate mitochondrial morphology, function, and genetic regulation, which combination of research techniques is most suitable?

Accepted Answer

Biochemical assays, genetic techniques, and microscopy

Answer

Microscopy only

Answer

Biochemical assays only

Answer

Genetic techniques only

Question 5

How do mitochondria communicate with the nucleus and other organelles to coordinate cellular activities?

Accepted Answer

Mitochondria release calcium ions into the cytoplasm, which can be sensed by the nucleus and other organelles.

Accepted Answer

Mitochondria produce ATP, which is used by other organelles as an energy source.

Accepted Answer

Mitochondria exchange metabolites with the cytoplasm, which can influence gene expression in the nucleus.

Question 6

Which of the following is NOT a function of mitochondria?

Accepted Answer

Protein synthesis

Answer

ATP production

Answer

Calcium buffering

Answer

Cellular respiration

Question 7

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

Accepted Answer

Generate a proton gradient for ATP synthesis

Answer

Produce NADH and FADH2

Answer

Transport electrons from glucose to oxygen

Answer

Convert pyruvate to acetyl-CoA

Question 8

Which of the following is a key enzyme involved in the Krebs cycle?

Accepted Answer

Citrate synthase

Answer

Lactate dehydrogenase

Answer

Pyruvate dehydrogenase

Answer

Hexokinase

Question 9

What is the role of coenzyme Q in the electron transport chain?

Accepted Answer

Electron carrier between Complexes I and II

Answer

NADH dehydrogenase

Answer

ATP synthase

Answer

Cytochrome c

Question 10

Which of the following conditions can lead to mitochondrial dysfunction?

Accepted Answer

Genetic mutations

Answer

Adequate supply of glucose

Answer

Optimal pH levels

Answer

High levels of oxygen

Question 11

What is the significance of the chemiosmotic gradient across the inner mitochondrial membrane?

Accepted Answer

Drives ATP synthesis

Answer

Regulates mitochondrial permeability

Answer

Facilitates electron transport

Question 12

What is the main function of the mitochondrial double membrane?

Accepted Answer

Compartmentalize mitochondrial processes

Answer

Generate ATP

Answer

Transport metabolites

Answer

Facilitate protein synthesis

Question 13

Which of the following statements about mitochondrial DNA is incorrect?

Accepted Answer

Codes for all mitochondrial proteins

Answer

Circular in shape

Answer

Prone to mutations

Answer

Inherited only from the mother

Question 14

What is the role of the mitochondrial outer membrane porin?

Accepted Answer

Allows passive diffusion of small molecules

Answer

Blocks the entry of protons

Answer

Facilitates electron transport

Answer

Controls mitochondrial respiration

Question 15

Which of the following is NOT a primary function of mitochondria?

Accepted Answer

Protein synthesis

Answer

Calcium homeostasis

Answer

Energy production (ATP synthesis)

Answer

Apoptosis (programmed cell death)

Question 16

The inner mitochondrial membrane forms characteristic folds known as:

Accepted Answer

Cristae

Answer

Stroma

Answer

Matrix

Question 17

Which of the following enzymes initiates the Krebs cycle?

Accepted Answer

Citrate synthase

Answer

Pyruvate kinase

Answer

Lactate dehydrogenase

Question 18

The final electron acceptor in the electron transport chain is:

Accepted Answer

Oxygen

Answer

NADH

Answer

Carbon dioxide

Answer

FADH2

Question 19

Which of the following disorders is primarily caused by mutations in mitochondrial DNA?

Accepted Answer

Leigh syndrome

Answer

Sickle cell anemia

Answer

Huntington's disease

Answer

Cystic fibrosis

Question 20

The mitochondrial matrix is the site of:

Accepted Answer

Krebs cycle and oxidative phosphorylation enzymes

Answer

ATP storage

Answer

Protein synthesis

Question 21

Electron transport occurs in which mitochondrial compartment?

Accepted Answer

Intermembrane space

Answer

Krebs cycle

Answer

Fatty acid oxidation

Answer

Glycolysis

Question 22

What is the primary function of uncoupling proteins in mitochondria?

Accepted Answer

Generate heat instead of ATP

Answer

Regulate ion transport

Answer

Synthesize proteins

Answer

Increase ATP production

Question 23

Mitochondrial DNA is characterized as:

Accepted Answer

Circular and double-stranded

Answer

Circular and single-stranded

Answer

Linear and single-stranded

Answer

Linear and double-stranded

Question 24

The primary function of the electron transport chain is to:

Accepted Answer

Pump protons to establish a proton gradient

Answer

Synthesize proteins

Answer

Generate ATP directly

Answer

Reduce NADH and FADH2

Question 25

**Where in mitochondria does oxidative phosphorylation occur?**

Accepted Answer

**Inner mitochondrial membrane**

Answer

Intermembrane space

Answer

Mitochondrial matrix

Answer

Outer mitochondrial membrane

Question 26

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

Accepted Answer

**Pump protons across the inner mitochondrial membrane**

Answer

Synthesize ATP directly

Answer

Transfer electrons from NADH to oxygen

Question 27

**Which enzyme catalyzes the first step of the citric acid cycle in mitochondria?**

Accepted Answer

**Citrate synthase**

Answer

Pyruvate dehydrogenase

Answer

Hexokinase

Answer

Creatine kinase

Question 28

**In the electron transport chain, what is the role of FADH2?**

Accepted Answer

**Donates electrons to the electron transport chain**

Answer

Reduces NADH

Answer

Oxidizes glucose

Answer

Synthesizes ATP directly

Question 29

**Which characteristic describes mitochondrial DNA?**

Accepted Answer

**Circular and double-stranded**

Answer

Linear and single-stranded

Answer

Linear and double-stranded

Answer

Circular and single-stranded

Question 30

**What is the primary function of the mitochondrial matrix?**

Accepted Answer

**Contains enzymes for the citric acid cycle and fatty acid oxidation**

Answer

Generates ATP

Answer

Houses the electron transport chain

Question 31

**Which of the following factors does NOT influence mitochondrial function?**

Accepted Answer

**Sleep deprivation**

Answer

Nutrient availability

Answer

Age

Answer

Exercise

Question 32

**What is the fundamental role of mitochondria in cellular metabolism?**

Accepted Answer

**Energy production**

Answer

DNA replication

Answer

Waste disposal

Answer

Protein synthesis

Question 33

**Which condition is known to cause impaired mitochondrial function?**

Accepted Answer

**Mitochondrial myopathy**

Answer

Fracture

Answer

Anemia

Answer

Diabetes

Question 34

**What is the significance of mitochondria being considered semi-autonomous organelles?**

Accepted Answer

**They possess their own replication and gene expression mechanisms**

Answer

They are transported freely within the cell

Answer

They are unaffected by changes in the cellular environment

Question 35

A patient presents with weakness, fatigue, and muscle cramps. Genetic testing reveals a mutation in the mitochondrial DNA encoding pyruvate dehydrogenase. This enzyme is responsible for which crucial step in cellular respiration?

Accepted Answer

Conversion of pyruvate to acetyl-CoA, linking glycolysis to the citric acid cycle

Answer

Electron transfer from NADH to oxygen

Answer

Oxidative phosphorylation

Answer

Fatty acid oxidation

Question 36

Which of the following is the primary function of the electron transport chain in mitochondria?

Accepted Answer

Generation of a proton gradient across the inner mitochondrial membrane

Answer

Oxidation of pyruvate to acetyl-CoA

Answer

Direct phosphorylation of ADP to ATP

Question 37

Mitochondrial DNA (mtDNA) differs from nuclear DNA in several aspects. Which of the following is a unique characteristic of mtDNA inheritance?

Accepted Answer

Maternal inheritance pattern

Answer

Double-stranded helical structure

Answer

Encoding for ribosomal RNA

Answer

Presence of introns

Question 38

A group of cells is observed to have reduced mitochondrial cristae density. This structural alteration is likely to have the most direct impact on which cellular process?

Accepted Answer

Oxidative phosphorylation

Answer

Glycolysis

Answer

Krebs cycle

Answer

Fatty acid synthesis

Question 39

Which molecule can passively diffuse across the inner mitochondrial membrane?

Accepted Answer

Oxygen

Answer

Pyruvate

Answer

ATP

Answer

NADH

Question 40

What is the primary function of uncoupling proteins (UCPs) in mitochondria?

Accepted Answer

Dissipation of the proton gradient, generating heat instead of ATP

Answer

Transport of electrons from NADH to oxygen

Answer

Pumping of protons from the matrix to the intermembrane space

Question 41

Which event is a critical step in the mitochondrial pathway of apoptosis?

Accepted Answer

Release of cytochrome c into the cytoplasm

Answer

Inhibition of caspase enzymes

Answer

Activation of DNA polymerase

Answer

Increased ATP synthesis

Question 42

A mutation in mitochondrial DNA affects the function of ATP synthase. Which component of the electron transport chain would be directly impaired by this mutation?

Accepted Answer

Complex V

Answer

Cytochrome c

Answer

Complex I

Answer

Coenzyme Q

Question 43

Which of the following is a consequence of mitochondrial fission?

Accepted Answer

Increases the total number of mitochondria within the cell

Answer

Prevents the inheritance of mitochondria by daughter cells

Answer

Reduces the rate of ATP production

Question 44

What is the primary role of the mitochondrial matrix in ATP production?

Accepted Answer

The matrix houses the citric acid cycle, which generates electron carriers for oxidative phosphorylation.

Answer

The matrix provides a location for ATP synthase to function.

Answer

The matrix stores the necessary enzymes for protein synthesis.

Answer

The matrix is the site of glycolysis, the initial step in glucose breakdown.

Question 45

A patient exhibits a genetic defect affecting mitochondrial ATP synthase. What is the most likely consequence of this defect?

Accepted Answer

Impaired oxidative phosphorylation, resulting in reduced ATP production and potential cellular dysfunction.

Answer

Enhanced glycolysis to compensate for reduced ATP production.

Answer

Increased mitochondrial biogenesis to compensate for the defect.

Answer

Increased production of reactive oxygen species (ROS), contributing to oxidative stress.

Question 46

Which of the following is NOT a characteristic of mitochondrial DNA (mtDNA)?

Accepted Answer

mtDNA is organized into multiple, linear chromosomes.

Answer

mtDNA replicates independently of nuclear DNA.

Answer

mtDNA is circular and double-stranded.

Answer

mtDNA encodes for some proteins involved in oxidative phosphorylation.

Question 47

A drug inhibits the electron transport chain in mitochondria. What is the most immediate impact on ATP production?

Accepted Answer

ATP production will decrease significantly, as the electron transport chain is crucial for generating the proton gradient that drives ATP synthase.

Answer

ATP production will remain unchanged, as other pathways can compensate.

Answer

ATP production will be temporarily halted, but will resume once the drug is removed.

Answer

ATP production will increase, as the cell compensates by relying on glycolysis.

Question 48

What is the primary role of the inner mitochondrial membrane in cellular respiration?

Accepted Answer

To create and maintain a proton gradient, which is utilized by ATP synthase to generate ATP.

Answer

To transport molecules between the matrix and the intermembrane space.

Answer

To synthesize mitochondrial proteins.

Answer

To serve as a barrier separating the cytoplasm from the mitochondrial matrix.

Question 49

Which statement accurately describes the link between mitochondria and apoptosis?

Accepted Answer

Mitochondria play a critical role in apoptosis by releasing cytochrome c, activating caspase cascades.

Answer

Mitochondria initiate apoptosis by releasing reactive oxygen species (ROS).

Answer

Mitochondria protect cells from apoptosis by increasing ATP production.

Answer

Mitochondria are unaffected by apoptosis, as they are independent organelles.

Question 50

A patient has a rare genetic disorder affecting the import of mitochondrial proteins. What is a likely consequence of this defect?

Accepted Answer

Dysfunctional mitochondria due to the absence of essential proteins required for respiration.

Answer

Increased mitochondrial fission, leading to smaller, more numerous mitochondria.

Answer

Increased mitochondrial fusion, leading to larger, more efficient mitochondria.

Answer

Enhanced glycolysis, providing an alternative source of ATP.

Question 51

What is the primary function of the mitochondrial cristae?

Accepted Answer

To increase the surface area of the inner mitochondrial membrane, enhancing the efficiency of oxidative phosphorylation.

Answer

To provide structural support for the mitochondrial matrix.

Answer

To facilitate the import of proteins into the mitochondria.

Answer

To regulate the flow of ions between the matrix and the intermembrane space.

Question 52

What is the most likely outcome of a mutation that inhibits the production of NADH dehydrogenase (complex I) in the electron transport chain?

Accepted Answer

Reduced ATP production due to a disruption in the electron flow and proton gradient.

Answer

Increased ATP production due to the accumulation of electron carriers.

Answer

Enhanced glycolysis, providing an alternative source of ATP.

Answer

No significant change in ATP production, as other complexes can compensate.

Question 53

A research team observes that muscle cells have an increased number of mitochondria compared to other cell types. What is the most likely explanation for this observation?

Accepted Answer

Muscle cells have a high energy demand for contraction, requiring more mitochondria for ATP production.

Answer

Muscle cells have specialized mechanisms for ATP production that do not rely on mitochondria.

Answer

Muscle cells have a low energy demand, requiring fewer mitochondria.

Answer

Muscle cells have a higher rate of mitochondrial fission, leading to increased numbers.