Mitochondria and Peroxisomes Flashcards
Structure of mitochondrian
• Outer membrane:
○ Smooth and composed of equal amounts of phospholipids and proteins
○ Has large number 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 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
Mitochondria morphology changes during apoptosis
○ The outer mitochondrial membrane becomes more permeable due to proteins in the Bcl 2 family called the proapoptotic proteins
§ This allows cytochrome C to leave the mitochondria and activate caspases
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.
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
Beriberi
- 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 micrometres 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
In mtDNA, what is the shape of chromosomes?
Circular
How are genes inherited for mtDNA?
• Genes are inherited cytoplasmically from the mother
Where is mtDNA located in the mitochondria?
In the matrix
What does the mitochondria have of its own
Mitochondria has its own ribosomes
How many base pairs does mtDNA have?
16,569
How many rRNA, tRNA and proteins does mtDNA encode?
2 rRNA, 22tRNA and 50 proteins
Comparison of mtDNA genetic code and standard genetic code
• 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.
How did bacterial endosymbionts become mitochondria?
• Aerobic bacterium engulfed by ancestral eukaryote
Some bacterial genes move to nucleus and the bacterial endosymbionts become mitochondria
How did aerobic eukaryote develop chloroplast?
• Aerobic eukaryote also may have engulfed a photosynthetic bacterium
This allows the new cell to make ATP from sunlight
What is the diameter of peroxisomes
Approximately 0.2 to 1 micrometres in diameter
What are peroxisomes surrounded by?
Single membrane
What do peroxisomes not have?
No DNA or ribosomes
Where are most peroxisomal proteins encoded?
Most peroxisomal proteins are encoded in the nucleus
Where do some peroxisome membrane proteins originate?
In the ER
What do peroxisomes contain and what do they do?
Peroxisomes contain enzymes that use molecular oxygen to oxidise various substrates
What is produced after the oxidisation of various substrates and what is it broken down into?
Reactions produce H2O2 which is broken down to water by the enzyme catalase
What are peroxisomes important for?
Important for the metabolism of long chain fatty acids
What do peroxisomes perform?
Perform critical steps in the synthesis of lipids
What do peroxisomes breakdown?
Excess purines
