mitochondria and peroxisomes Flashcards
structure of mitochondrian
Outer membrane:
Smooth and composed of equal amounts of phospholipids and proteins Has large numbers of proteins known as porins Porins are integral membrane proteins that allow the movement of molecules Inner membrane: Inner membrane folded to form structure called cristae Folding increases surface area Strictly permeable to ATP and oxygen Intermembrane space: Space between inner and outer membrane Matrix: Complex mixture of enzymes and proteins which are important for the synthesis of ATP molecules
Microtubules network in mitochondria
Movement in the cytoplasm shows mitochondria are associated with microtubules
This determines the positioning and orientation of the mitochondria
Mitochondria plasticity
Mitochondria is constantly changing shape
Mitochondria fuse with one another and then separate
Mitochondrial morphology changes during
Apoptosis
The outer mitochondrial membrane becomes more permeable due to proteins in the BcI 2 family called the proapoptotic proteins This allows cytochrome C to leave the mitochondria and activate caspases Ca2+ transfer Cell cycle Nutrients starvation Induces mitochondrial tubulation to protect the mitochondria from degradation from the autophagy pathway
Mitochondria morphology changes during nutrients starvation
Induces mitochondrial tubulation to protect the mitochondria from degradation from the autophagy pathway
In what 2 ways is mitochondrial proteins produced?
Mitochondrial proteins are produced in two ways. RNA synthesised from the nucleus of the cell and the mitochondria’s DNA are used to translate into proteins.
Mitochondrial DNA
Chromosomes are circular
Genes are inherited cytoplasmically from the mother mtDNA is located in the matrix Have their own ribosomes mtDNA contains 16,569 base pairs which encode 2 rRNAs, 22tRNAs and 50 proteins Mitochondrial genetic code differs from the standard nuclear code. UGA is a stop codon in the nucleus whereas in the mitochondria it codes for tryptophan
Functions of mitochondria
Breakdown of fatty acids to acetyl CoA
Decarboxylation of pyruvate to acetyl CoA Citric acid cycle Oxidative phosphorylation Thermogenesis Play an important role in apoptosis
Beri Beri
A neurological and cardiovascular disease caused by a dietary deficiency of thiamine
Patients suffering have a higher than normal serum levels of the enzyme substrates of pyruvate dehydrogenase and alpha ketoglutarate Damage to peripheral nervous system Pain in the limbs Weakness of the musculature Distorted skin sensation Heart may enlarge and cardiac output may be inadequate
Structure of peroxisomes
Approximately 0.2 to 1 micrometers in diameter
Peroxisomes are surrounded by a single membrane No DNA or ribosomes Most peroxisomal proteins are encoded in the nucleus Some peroxisomal membrane protein originates in the ER Peroxisomes contain enzymes that use molecular oxygen to oxidise various substrates Reactions produce H2O2 which is broken down to water by the enzyme catalase Important for the metabolism of long chain fatty acids Perform critical steps in the synthesis of lipids Breakdown of excess purines
Peroxisome biogenesis
Peroxisome precursor vesicle buds off the ER
The vesicles fuse with one another or with pre-existing peroxisomes Growth by uptake of specific peroxisomal proteins and lipids from cytosol Fission can then occur to form daughter peroxisomes
