Biomedical Sciences I: Mitochondrion Quiz

<p>Cleavage of specific aspartic acids (B)</p> Signup and view all the answers

<p>Mitochondrial proteins (D)</p> Signup and view all the answers

<p>Protons (H+) (C)</p> Signup and view all the answers

<p>Phosphorylation of ADP to ATP (C)</p> Signup and view all the answers

<p>Neuromuscular symptoms (D)</p> Signup and view all the answers

<p>Transfers electrons to cytochrome c (B)</p> Signup and view all the answers

<p>Autophagic pathway (B)</p> Signup and view all the answers

<p>Import of nearly all nucleus-encoded mitochondrial proteins (A)</p> Signup and view all the answers

<p>SAM complex (A)</p> Signup and view all the answers

<p>Thanks to chaperones of the hsp70 family (B)</p> Signup and view all the answers

<p>Mediates the insertion of mitochondrial genome-encoded membrane proteins (D)</p> Signup and view all the answers

<p>Intervention of the endoplasmic reticulum (B)</p> Signup and view all the answers

<p>Fusing with each other and splitting (D)</p> Signup and view all the answers

<p>Their orientation and distribution within the cell (C)</p> Signup and view all the answers

<p>Yellow (D)</p> Signup and view all the answers

<p>Golgi apparatus (D)</p> Signup and view all the answers

<p>Transport of proteins at the inner membrane (C)</p> Signup and view all the answers

<p>Association with the cytoskeleton (D)</p> Signup and view all the answers

<p>Chlorophyll-rich matrix (D)</p> Signup and view all the answers

<p>Cristae (C)</p> Signup and view all the answers

<p>Storing genetic information for protein synthesis (B)</p> Signup and view all the answers

<p>Uniparentally from the mother (B)</p> Signup and view all the answers

<p>Heteroplasmy in offspring (B)</p> Signup and view all the answers

<p>Initiating cell death mechanisms (D)</p> Signup and view all the answers

<p>To ensure maternal inheritance of mtDNA (C)</p> Signup and view all the answers

<p>Mytophagy (B)</p> Signup and view all the answers

<p>Gel-like consistency filled with enzymes (D)</p> Signup and view all the answers

<p>To allow maternal dominance of mtDNA (D)</p> Signup and view all the answers

<p>It becomes inefficient. (A)</p> Signup and view all the answers

<p>Acetyl CoA (A)</p> Signup and view all the answers

<p>Mitochondrion (D)</p> Signup and view all the answers

<p>Glycolysis and the TCA cycle (D)</p> Signup and view all the answers

<p>Phosphorylates ubiquitin and Parkin (A)</p> Signup and view all the answers

<p>By the malate-aspartate shuttle (D)</p> Signup and view all the answers

<p>Cytochrome c (D)</p> Signup and view all the answers

<p>Production of ATP (B)</p> Signup and view all the answers

<p>Biosynthesis process (C)</p> Signup and view all the answers

Mitochondria are dynamic structures that move within cells, constantly changing shape, dividing, and fusing. They are also closely associated with the cytoskeleton, which determines their distribution within the cell.

Depending on the cell type, mitochondria can have different shapes. Some are individual, bean-shaped organelles, typically 1-4 micrometers in length. Others form highly branched, interconnected tubular networks.

Mitochondria are believed to have evolved from an ancient aerobic bacterium that developed a symbiotic relationship with an anaerobic host cell. This process is known as endosymbiosis.

Mitochondria are surrounded by a double-membrane system, with an outer membrane, inner membrane, and cristae. The space between the two membranes is called the intermembrane space, and the inner compartment enclosed by the inner membrane is called the matrix.

The outer mitochondrial membrane serves as the outer boundary of the mitochondrion. It's smooth and uniform and freely permeable to ions and small molecules. It's composed of various proteins, including translocases (proteins that help import mitochondrial proteins), and is rich in cardiolipin, but lacks cholesterol.

Cristae are series of invaginated membranous sheets within the inner membrane. They contain enzymes and structural proteins involved in aerobic respiration and ATP production.

The intermembrane space contains proteins involved in the initiation of cell death mechanisms. It has the same pH and ionic composition as the cytoplasm.

The matrix is a gel-like substance within the inner membrane. It's rich in soluble proteins (enzymes for the Krebs cycle), contains a small amount of DNA (mtDNA), and has free ribosomes, smaller than those found in the cytoplasm.

Mitochondrial DNA (mtDNA) encodes for essential proteins, rRNA, and tRNA. It has a high mutation rate, leading to heteroplasmy (a mixture of different mtDNA variants within a cell). This makes it valuable for tracing evolutionary history.

Unlike nuclear DNA, mitochondrial DNA is inherited maternally. This means offspring receive mtDNA solely from their mother. During fertilization, sperm mitochondria are typically degraded and eliminated from the fertilized egg.

Most proteins destined for the mitochondria are synthesized by ribosomes in the cytosol and then transported into the organelle.

Specialized protein complexes embedded within the mitochondrial membranes that facilitate the transport of proteins into the organelle.

A complex located in the outer mitochondrial membrane essential for importing nearly all proteins encoded by the nucleus.

A complex responsible for inserting beta barrel proteins into the outer mitochondrial membrane, ensuring their proper folding.

Protein complexes embedded in the inner mitochondrial membrane that mediate the import of proteins into the mitochondrial matrix and inner membrane.

A complex that guides the insertion of membrane proteins encoded by the mitochondrial genome into the inner mitochondrial membrane.

Proteins destined for the mitochondria remain unfolded in the cytosol, preventing aggregation, thanks to chaperones of the Hsp70 family.

Mitochondria are dynamic organelles that can change their shape by fusing with each other (fusion) or splitting into separate units (fission).

The microtubular cytoskeleton is associated with mitochondria, influencing their orientation and distribution within the cell.

The endoplasmic reticulum plays a role in initiating mitochondrial fission, starting the constriction process that eventually splits the organelle.

Mitochondria that are no longer functional undergo a process called mitophagy, a specialized form of autophagy, where they are targeted for degradation within the cell.

When a mitochondrion loses its electrochemical gradient, its protein import mechanism becomes inefficient. This leads to the accumulation of the PINK1 protein kinase on the outer mitochondrial membrane.

Activated PINK1 phosphorylates both mitochondrial ubiquitin and the Parkin protein. These phosphorylations trigger the formation of an autophagosome, a structure that engulfs the damaged mitochondrion for degradation.

Mutations in the PINK1 and Parkin genes are often associated with Parkinson's disease, a neurodegenerative disorder characterized by the accumulation of dysfunctional mitochondria in neurons.

Mitochondria are the powerhouses of the cell, converting glucose into ATP through oxidative phosphorylation.

Mitochondria are involved in the urea cycle, a process that removes nitrogenous waste from the body. The two critical steps of the urea cycle occur in the mitochondrial matrix of liver cells.

Mitochondria are involved in the synthesis of heme groups, essential components of hemoglobin and other proteins. This process happens in both the mitochondrion and the cytoplasm.

Mitochondria play a key role in membrane biosynthesis. They synthesize lipids such as phosphatidylethanolamine, phosphatidylglycerol, and phosphatidic acid.

Mitochondria play a role in apoptosis, a programmed cell death process, by being involved in the caspase-dependent pathway.

Mitochondria regulate the concentration of calcium ions in the cytosol. They interact closely with the endoplasmic reticulum (ER) to exchange lipids.

Electrons from either NADH (via complex I) or FADH2 (via complex II) enter the electron transport chain.

Electrons are passed from complex I or II to ubiquinone.

Reduced ubiquinone (ubiquinol) transfers electrons to complex III and then to cytochrome c.

Cytochrome c carries electrons to complex IV (cytochrome oxidase), where they finally reach oxygen, forming water (H2O).

The energy released as electrons move through the chain is used to pump protons from the mitochondrial matrix across the inner membrane, creating a proton gradient.

The electrochemical gradient drives protons back into the matrix, powering ATP synthase to generate ATP.

A caspase is a protease (enzyme that breaks down proteins) that plays a crucial role in apoptosis (programmed cell death).

Caspases are synthesized as inactive precursors and activated only during apoptosis.

Two main pathways trigger caspase activation: the extrinsic pathway (activated by external signals) and the intrinsic (mitochondrial) pathway (activated by internal signals).

Mitochondrial diseases are a heterogeneous group of disorders caused by defects in mitochondria, leading to impaired energy production.