Cytoplasmic Organelles Flashcards
Where does much of the energy generating metabolism occur in the cell?
Mitochondria, chloroplasts, and peroxisomes
What feature of mitochondria and chloroplasts have which allows them to encode their own genes?
They carry their own DNA
What feature of mitochondria and chloroplasts have which allows them to make some of their own proteins?
They carry their own ribosomes
How do mitochondria, chloroplasts, and peroxisomes divide?
Autonomously; binary fission
What does the endosymbiont hypothesis explain?
Explains the origins of eukaryotes from prokaryotes
What evidence backs up the endosymbiont hypothesis?
Mitochondria and chloroplasts:
- Have circular DNA
- Have inner membranes with prokaryote properties
- Have 70S ribosomes
- Have unique protein import mechanisms
- Divide by binary fission
- If chloroplasts are depleted from a cell, they cannot reform
What are mitochondria developed from?
Proteobacteria
What are chloroplasts developed from?
Cyanobacteria
Where are the proteins translated in the post-translational pathway?
On free ribosomes in the cytosol
What molecule helps the transport of proteins through organelle membranes?
Chaperonins
How many mitochondria are found in a cell?
20 - >1000 /cell
What is the name of the protein that forms the small pores found in the outer membrane of a mitochondrion?
Perforin
What size of molecules can diffuse through the pores in the mitochondria’s outer membrane?
Less than 10kDa
What do the integral proteins found in the mitochondria’s inner membrane do?
Principally required for transport and processes that lead to ATP production
What will you find in a mitochondrion’s matrix?
- Molecules that have been specifically transported across the membrane, or have been generated by the mitochondrion’s own DNA
- Mitochondrial DNA, RNA, ribosomes
- Enzymes for the Kreb’s cycle
- Small granules
How big are chloroplasts?
5 - 10µm
What is the difference between the outer and the inner membrane of chloroplasts?
Outer - permeable to small molecules
Inner - impermeable to most molecules, inc. small ones
How are thylakoids arranged?
In stacks called grana
Where exactly does photosynthesis occur?
In the thylakoid membranes
What occurs during photosynthesis?
The capture of photons
Electron transport and ATP production
Reduction of NADP+ to NADPH
Where do light dependent and light independent (dark) reactions occur?
Light dependent - thylakoids
Light independent - stroma
Where are photons absorbed?
By pigments (usually chlorophyll) in photocentres
What happens during the Calvin cycle?
CO2 from the atmosphere is converted to 3-carbon sugar phosphates, which can then be converted to glucose
How big are peroxisomes?
0.5µm
How many peroxisomes are found in a cell? What kind of cell would contain more?
~500/cell, more in liver cells
What are the 2 more well known functions of peroxisomes?
A compartment for oxidation reactions, and lipid synthesis
What do the oxidation reactions in peroxisomes achieve?
They break down a variety of substrates, inc. uric acid, ethanol, and methanol
What is the by-product of the oxidation reactions that occur in peroxisomes?
Hydrogen peroxide (hence the name peroxisome)
What kind of lipids are peroxisomes involved in the synthesis of?
Cholesterol and bile acids (derived from cholesterol)
What is the name of the phospholipid found in the cell membranes of Schwann cells? (Synthesised by peroxisomes)
Plasmalogen
