Cell organelles Flashcards
What is one theory on how the membrane developed?
The DNA was stuck to the cell membrane. Eventually, the membrane invaginated and form a vesicle. Extra membrane layering may have been a primative ER.
What are the evolutionary benefits of having membrane bound organelles (4)?
- Surface area
- Directed protein flow
- Compartmentalization
- cell waste breakdown
How much membrane is cell membrane vs organelle membrane?
2 to 98%
How much of the cell is cytosol vs membrane bound?
50/50
What are the two classifications of organelles?
Membrane- golgi, ER, mitochondria, lysosome, perioxosomes, vesicles
Macromolecular- ribosomes, proteosomes
Where are mitochondria found in the cell?
Often found in areas with the highest energy demands. They are often associated with MTs
Describe how mitochondria make energy.
The CAC occurs inside the matrix and takes Acetyl-CoA from cytosol and turns it into CO2 and the energy carriers FADH2 and NADH. NADH and FADH2 go to the intracellular membrane where they donate electrons to a series of 3 protein complexes, which pump H from the matrix into the intramembrane space (against the diffusion gradient). As the H ions return to the matrix, they pass the membrane through ATP synthase, spinning it. ATP synthase turns the kinetic energy provided by the H into ATP. It can produce as much as 100 ATP/sec.
What is unique about mitochondria as an organelle?
It contains its own DNA/ribosomes/ribosomal proteins. The copies of DNA vary widely and are inherited maternally. Most malfunctions of mitochondria occur b/c of a problem with mtDNA.
What is MERRF?
ragged red fibers- occurs b/c of mtDNA mutation to tRNA lysine.
Describe the composition of ribosomes.
Two subunits, one large and one small, each made up of a combination of protein and rRNA. The large catalyzes the new peptide bonds whereas the small is the framework for the mRNA.
Describe how translation occurs.
Ribosomes have 4 bindings spots- 1 for mRNA and 3 for peptides (A,P,E). mRNA in the A site has codon “read” and matched with appropriate tRNA. P spot AA has its carboxyl end bound to amino end of new A spot AA. Large subunit translocates relative to small, moving the two AA into the E and P spots. Small subunit translates 3 bases. tRNA in E slot is removed and new tRNA enters the A spot.
In what direction is mRNA translated?
5’ to 3’
In what direction are AA read?
N terminal to C terminal
How is where a protein is made related to where it will eventually go?
Membrane bound proteins or proteins that will be exocytosed are made in ribosomes associated with the rER. Cytosolic proteins are made by free ribosomes.
What are polyribosomes?
Found both in free and membrane ribosomes, they are a collection of ribosomes working on the same mRNA.
