Week 8 - Mitochondrial Protein L14

What are the main components of the endomembrane system?

Rough & Smooth Endoplasmic Reticulum, Golgi Complex, Endosomes, Lysosomes, Vacuoles.

What do free ribosomes synthesize?

Proteins used in the cytosol.

Which organelles contain a double membrane?

Nucleus, Peroxisome, Mitochondria, Chloroplast.

How are proteins imported into mitochondria?

Proteins are imported post-translationally, meaning after their synthesis in the cytosol.

What are the four sub-compartments of mitochondria?

1. Outer mitochondrial membrane

2. Inner mitochondrial membrane

3. Intermembrane space, Matrix.

What is the role of the outer mitochondrial membrane (OMM)?

It contains enzymes for oxidation and porins that allow the passage of small molecules.

What is unique about the inner mitochondrial membrane (IMM)?

It has a high protein:lipid ratio, contains cardiolipin, and houses the machinery for ATP synthesis.

What is found in the mitochondrial matrix?

Ribosomes, circular double-stranded DNA, non-chromosomal DNA.

What is the targeting sequence in mitochondrial protein uptake?

It is located at the N terminus of proteins and consists of positively charged amino acids.

What is the TOM complex in mitochondria?

A protein import complex in the outer mitochondrial membrane that binds preproteins and translocates them.

What is the role of the TIM complex?

It is a protein import complex in the inner mitochondrial membrane that facilitates the translocation of preproteins.

What is the function of peroxisomes?

They help break down large molecules and detoxify hazardous substances - Site of synthesis of H2O2 and Site of degradation of H2O2.

What is Zellweger Syndrome?

A rare inherited disease characterized by neurological, visual, and liver abnormalities due to the lack of peroxisomes.

What causes Adrenoleukodystrophy (ALD)?

A defect in a membrane protein that transports very long chain fatty acids (VLCFAs) into peroxisomes.

What happens if VLCFAs accumulate in the brain?

They destroy myelin sheaths that insulate nerves, leading to neurological dysfunction.

How do proteins access peroxisomes?

They have peroxisomal targeting signals (PTS) for matrix proteins or mPTS for membrane proteins.

What is the significance of the pre-sequence in mitochondrial proteins?

It serves as a targeting signal for the import of proteins into mitochondria.

What is the role of mitochondrial chaperones?

They prepare polypeptides for uptake into mitochondria and assist in their translocation or diffusion of polypeptide across membrane

What is the importance of the electric potential across the inner mitochondrial membrane?

It powers the import of positively charged targeting signals into the matrix.