Koc - Peroxisomes and Mitochondria

Question 1

Fusion vs Fission

Answer 1

Fusion: Allows Exchange of Genetic Material

Fission: Distribution of mitochondira b/t daughter cells during division–transport mitochondria to areas of high energy demand

Question 2

Four regions of the mitochondria

Answer 2

Matrix

Inner Membrane

Intermembrane Space

Outer Membrane

Question 3

Mitochondria Matrix

Answer 3

Home to majority of soluble enzyme and proteins

PDH Complex

Citric Acid Cycle Enzymes

Fatty Acid Oxidation Enzymes

Question 4

Mitochondria Inner Membrane

Answer 4

Cristae increase surface area

Ion Impermeable–proton gradient formed for ATP synthesis

TIM import proteins

Question 5

What helps process targeting pre-sequence in the Inner Membrane?

Answer 5

Matrix Processing Peptidase (MPP)

Question 6

Some inner membrane proteins are encodes on _________ , the protein ________ embeds them.

Answer 6

Mitochondrial Genome

Oxa1 Translocase

Question 7

Outer Membrane

VDACs?

What mediates protein insertion into outer membranes?

Answer 7

Voltage Dependent Anion Channel, embedded in outer membrane

Very permeable to small molescules < 1000 Da

TOM complex mediates transport

SAM mediates insertion into outer membrane

Question 8

What type of signals do Transmembrane Proteins have?

What chaperones are used?

Answer 8

Internal import signals instead of presequences

Tim9-10 Chaperones bring to Tim22

Question 9

Metabolic reactions catalyzed by peroxisomes?

Answer 9

1. Oxidative Reactions using molecular oxygen

2. Synthesis of bile acids and plasmalogens

• Breakdown normal metabolites: B-oxidation of fatty acids; AAs, Uric Acid, Fatty Acid, Purines, etc
• Breakdown harmful compounds: Methanol, formaldehyde, phenol, poisons, toxins
• Produces hydrogen peroxide as byproduct of oxidative breakdown

Question 10

What two ways are peroxisomes formed?

Answer 10

1. Made from scratch–vesicle budding from the ER
2. Divisiion of existing peroxisomes (faster)

Question 11

Peroxisome Protein Synthesis

Answer 11

Synthesized on free ribosomes and cytostolic ribosomes

Question 12

Free Ribosome targeting sequence for peroxisomal matrix proteins?

What recognizes this?

Answer 12

PTS1-SKL (Ser-Lys-Leu)

PTS1 recognized by Pex5 receptor

PTS1/Pex5 complex binds to a docking complex on peroxisome

Question 13

Cytostolic Ribosome targeting sequence?

Answer 13

mPTS labels, recognized by Pex19

Pex19/cargo complex recognized by Pex3/Pex16 in peroxisome membrane

Question 14

How are electrons transported in peroxisomes?

What impact does this have on ATP?

Answer 14

Electrons are transfered directly onto oxygen, not electron transport chain.

Results in less ATP produced vs Mitochondria

Question 15

When must fatty acids be transfered from peroxisomes to mitochondria?

Answer 15

Longer fatty acid chains–peroxisomes stop at 8-carbons

Question 16

What is the major coenzyme of peroxisomes?

How are they regenerated?

Answer 16

FAD (flavin dependent)

Oxidized flavins are regenerated by reaction with oxygen to produce hydrogen peroxide

Question 17

What catalyzes initial double bond formation in peroxisomes?

What does this generate?

** Key Difference in B-Oxidation in Peroxisomes **

Answer 17

FAD-dependent Acyl-CoA Oxidase

Question 18

Rhizomelic Chrondrodysplasia Punctata Type I (RCDP Type I)

Answer 18

PEX 7 dysfunction

Question 19

Zellwegger Spectrum (ZS) Disorder

Neonatal Adrenoleukodystrophy (NALD)

Infantile Refsum’s Disease (IRD)

Answer 19

PEX: 2, 6, 5, 12

1/50,000 (rare)

Disrupted peroxisomal assemble in over 20 genes

Results:

Accumulation of VLCFA

Plasmalogen Deficiency

NALD, IRD both forms of ZS

Question 20

Human Deafness Dystonia Syndrome (Mohr-Tranabjaerg)

Answer 20

Deafness, dystonia, mental deterioration

Mitochondrial protein defects

Question 21

Cardiolipin

Answer 21

Four fatty acyl chains, found in inner mitochondrial membrane

Key for mitochondrial energy metabolism

Question 22

Barth Syndrome

Answer 22

Decrease in tetralinoleoyl

Accumulation of monolysocardiolipin

Symptoms: Cardiomyopathy, skeletal myopathy, neutropenia, growth retardation

Defect in Phospholipid Acyltransferase (Tafazzin); inability to remodel cardiolipin