Lecture 9 Flashcards
Catabolism
Set of metabolic pathways that break down molecules into smaller units & release energy.
Stage1) digestion (hydrolysis)
Stage2 & 3) oxidative processes:
- stage 2) generate acetylcoA. Begin in cytosol and peroxisomes continues in the mitochondria.
- stage 3) complete harvest of energy and ATP generation——> mitochondria
Lysosome function
Digest worn out organelles
PH for lysosomes and why?
Acidic. Because if the enzymes leave the lysosome it stops them from ingesting the cell
How is the pH of lysosomes maintained?
Use of h+ pump.
Proton pump I. The lysosomal membrane.
What are the two types of lysosomes?
Primary- can only contain hydrolytic enzymes, have homogenous matrix and smaller dimensions.
Secondary- taken up material to be digested. Larger. Heyerolysomes and autolysomes. Non homogenous matrix.
What is heterophagy?
Digestion of foreign materials
What is autophagy?
Lysosomes breaking down damaged organelles
Heyerophagy AFTER endocytosis.
Engulfed molecules form small vesicles of irregular shape which are Early endosomes. (Hydrogen ions Transport from golfi apparatus)
Components are recycled and merge with primary lysosomes forming LATE ENDOSOMES which are ph 6.
Lower ph mediates removal of phosphate from mannose 6 phosphate. This activated acid hydrolyse an dorms active secondary lysosomes.
Heterophagy AFTER phagocytosis.
Particles embedded in phaosone are delivered to lysosomes with a secondary lysosome.
Explain the use of autophagy, why is it important?
It renews and remodels during cell differentiation. It removes all cellular organelles ie when erythrocytes mature. If it didn’t it pwould cause cell aging and cell damage.
What happens after digestion in secondary lysosomes?
The organic molecules move to the cytoplasm.
The byproducts that have not been digested are retained in lysosomes as RESIDUAL BODIES.
Function of peroxisome
Break down hydrogen peroxide via catalase
Break down fatty acids
Breakdown excess purins to uric acid.
Makes plasmologens (lipids that make myelin) Makes cholesterol and bile acids
How are peroxisomes diff from lysosomes?
Like mitochondria they are assembled from free ribosomes and imported into peroxisomes as pp chains.
They replicate by division
How are proteins destined for peroxisomes assembled?
Synthesised On free ribosomes and imported into peroxisomes as PP chains
Each contains PEROXIMAL TARGET SIGNAL which binds to a receptor molecule that takes the protein to the peroxisome
Protein import results in peroxisome growth and division causes new peroxisomes
