Mitochondria + Peroxisomes Flashcards
Describe the structure of mitochondria?
2 membranes=> inner + outer membrane
Between the 2 membranes are called the intermembrane space
Inner membrane form Cristae
Matrix- inner most space
Mitochondrial morphology changes during:
Apoptosis= cell death
Ca2+ transfer
Cell cycle
Nutrient starvation- mitochondria elongates
Mitochondria contain their own DNA
Mitochondria chromosome are circular in bacteria
Mitochondrial genes are inherited cytoplasmically from mother
Mitochondrial DNA (mtDNA) is located matrix
Mitochondria contain their own ribosomes
Other mitochondrial proteins are encoded in nucleus, translated in cytoplasm + imported into mitochondria
Mitochondrial genetic code differed from standard nuclear code
Describe the endosymbiosis theory for origin of mitochondria?
Mitochondria evolved from ancient bacteria
Got incorporated into cells when eukaryotic cells evolved
Aerobic bacteria is taken by ancestral anaerobic eukaryote + then it multiples
Aerobic metabolism uses O2 that can break down nutrient molecules much more efficiently thereby generates vastly more ATP than anaerobic bacterium would have been able to produce
What are functions of mitochondria?
Breakdown of fatty acids into acetyl coA which takes place in matrix
Decarboxylation of pyruvate into acetyl coA which is important in metabolism
Citric acid cycle
Oxidative phosphorylation
Thermogenesis=> generation of heat. Important in hibernating animals
Play a role during apoptosis
Localisation of mitochondria near sites of high ATP utilisation
Cardiac muscle=> within muscle fibres are mitochondria. Muscle contraction requires ATP
Sperm cell=> ATP is required for sperm cell to rotate, to have motility so they can move. Mitochondria is wrapped around flagellar axoneme
What is the disease Beriberi?
Caused by dietary deficiency thiamine (vitamin B1)
Is neurologic + cardiovascular disorder
Thiamine pyrophosphate => prosthetic group for 2 mitochondrial enzymes
Substrates of enzyme accumulate in patients suffering from disease
What are effect of Beriberi on patients?
Damage to peripheral nervous system Pain in limbs Weakness of musculature Distorted skin sensation Heart may be enlarged + cardiac output inadequate
What are peroxisomes?
Extremely rich, highly concentrated enzymes that carry specific aspects of oxidative reactions, metabolism. Concentration may be so high that proteins form crystals
Describe the structure of peroxisomes?
Approximately 0.2-1 um in diameter
Are surrounded by single membrane
Contain no DNA or ribosomes
Most peroxisomal proteins encoded in nucleus, translated in cytoplasm + then imported
At least some peroxisomal membrane proteins originate in ER
All peroxisomes contain enzymes that use molecular oxygen to oxidise various substrates
Reactions produce hydrogen peroxide which is broken to water by enzyme catalase
What is function of peroxisomes?
Important for metabolism of long-chain fatty acids
Perform critical steps in synthesis of certain lipids e.g. cholesterol
Breakdown of excess purines (AMP, GMP) to Uric acid