Organelles Flashcards
What are some benefits of having distinctive organelles in a eukaryotic cell?
Membrane-bound spaces permit the segregation of functions within the cell and the concentration of specific functions. organization of protein movement through the cell. Both facilitate increasing levels of complexity found in eukaryotes. Another key function is to facilitate degradation of worn-out cell components in the longer-lived eukaryotes. The same degradative system can be modified to process extracellular material.
What is the major benefit of having membrane-bound organelles?
Organelles increase membrane surface area, maintain specificity and complexity of function
Which organelles are not membrane bound?
Ribosomes and proteasomes are macromolecular complexes.
What is the function of mitochondria?
Powerhouse of cell. Produces ATP through the electron transport chain and citric acid cycle.
Describe process of ATP generation in mitochondria
- Electron goes through 3 complexes, pumping out H+ out of matrix (creates gradient). ATP synthase rotates due to gradient change, driving ATP synthesis
What is the function of the Golgi?
The Golgi apparatus consists of stacks of flattened vesicles that have been likened to pita bread. Proteins from the ER are modified (e.g. glycosylation) and then sorted to their various specific final locations.
About what proportion of cells are within the membrane bound organelles? Which, are the largest?
Cytosol 50%; Mitochondria- 20%; Golgi and ER: 15%; nucleus 6%; rest take up small portions
Where are most of the proteins involved in ATP generation located?
The inner mitochondrial membrane (which is folded into christae) contains the proteins of the electron transport system and the enzyme ATP synthase.
What is the driving force for ATP synthesis?
The electrochemical gradient of hydrogen ions in the intermembrane space, created by the electron transport system, is the driving force that activates ATP synthase.
What is the role of the two components of the ribosomal complex?
The small subunit binds mRNA, which then binds to the large ribosomal unit. The large ribosomal unit has three sites (A-site, P-site and E-site) for binding of tRNAs
What is the function of the smooth ER?
Synthesis of membrane lipids (phospholipids, cholesterol and glycolipids), synthesis of steroid hormones, drug detoxification (cytochrome p450 enzymes) and sequestration of calcium.
How does protein know to go into the endoplasmic reticulum?
There is a signal recognition particle (SRP) that recognizes a signal sequence on the beginning of the developing protein. This particle binds to the endoplasmic reticulum and the forming protein is inserted through the membrane of the endoplasmic reticulum, where it folds.
What kinds of proteins are inserted into the endoplasmic reticulum?
Secreted proteins and proteins that become associated with the membranes of the cell surface or other organelles.
Why do ribosomes represent an important target of antibiotics?
Prokaryotes (such as bacteria) have different ribosomal subunits which can be targeted by specific chemicals (killing the bacteria and not damaging the eukaryotic cell).
What is the role of proteosomes and what would happen if these were not functional?
They degrade proteins attached to ubiquitin. This is used to recycle some normal proteins, but also to eliminate misfiled proteins. These proteins would accumulate in the cell if the system were not functional.
