Questions

Define the following terms:

Amphipathic, plasmalemma, glycocalyx
An amphipathic molecule is one with a polar and an non-polar end.
The plasmalemma is the cell membrane.
The glycocalyx is the carbohydrate-rich region surrounding the cell. This includes phospholipids, glycoproteins and proteoglygans. It is protective of the cell and also provides recognition molecules.
Triskelion is the shape of clathrin. It consists of three bent arms that interlock with adjacent molecules.
A phagosome is the product of fusion of a phagocytic vesicle with lysosomes.
Autophagosomes are a method for disposing of old organelles by encapsulation with endoplasmic reticulum and fusion with lysosomes.
Opsonization is the coating of an object (such as a bacteria) with antibodies that will permit recognition by phagocytic cells.
If something cannot be digested in the lysosomes it will form lipofuscin (more prevalent in older cells).
Euchromatin is lighter staining, actively transcribing, loose packed chromatin. A euchromatic nucleus means a cell is very active in protein synthesis.
Heterochromatin is darker staining, non-transcribing, tight packed chromatin. The two types are constitutive (at edge of nucleus and rarely transcribed) and facultative (shut down but may be activated if needed).
Kayokinesis is the separation of the nucleus into two daughter nuclei.
Cytokinesis is the separation of the cytoplasm into two daughter cells.
A nucleosome consists of about 150 base pairs of DNA wrapped around an octameric core od histone proteins.
A solonoid consists of one turn of a spiral of nucleosomes.

Answer the following questions:

Question 1. What is the chemical composition of the lipid part of the cell membrane? What is the most common lipid?

Answer 1. They are phospholipids (two fatty acid chains attached to a glycerol molecule that is, in turn, attached to a polar side chain by a phosphate group). The most common type is Phosphatidylcholine.

Question 2. What determines whether something will pass the lipid bilayer?

Answer 2. The ability to cross the lipid bilayer is dependent on lipid solubility and size of the molecule. Things that are highly fat soluble and small cross the membrane. Large molecules and charged particles (such as ions) do not. Small polar molecules are in between.

Question 3. What factors stiffen the plasma membrane? What makes it more fluid?

Answer 3. Cholesterol in the membrane functions to stiffen it up, while the unsaturation of the phosopholipids makes the layer fluid.

Question 4. What enzymes are responsible for distributing phospholipids in the correct side of the membrane?

Answer 4. Flipases function to selectively transfer certain lipids from one side of the bilayer to the other.

Question 5. Where are new membranes made?

Answer 5. Golgi and sER are responsible for making new membrane.

Question 6. What is the role of the Golgi in creation of membrane?

Answer 6. The Golgi will glycosylate some membrane phosphlipids (glycolipid) and will also glycosylate proteins in the membrane.

Question 7. When vesicles of membrane are added to the plasma membrane, which side winds up facing the outside of the cell?

Answer 7. The side inside the vesicle will be on the outer surface of the plasma membrane lipid bilayer.

Question 8. What is the role of the glycocalyx?

Answer 8. Glycocalyx has cell recognition and protective properties.

Question 9. What are the functional types of transmembrane proteins?

Answer 9. Transporters, anchors, receptors, enzymes and pumps.

Question 10. What is the role of integrins?

Answer 10. These are anchor proteins that attaché cytoskeletal elements to extracellular elements.

Question 11. Are there more proteins associated with the inner or outer leaflet of the lipid bilayer? Why?

Answer 11. Thre are more attached to the inner leaflet since many of the proteins attached to that side have enzymatic or regulatory functions within the cell.

Question 12. What is a lipid raft and why is it important?

Answer 12. A lipid raft is a domain within the cell membrane within which are clustered protiens of complimentary function. This allows them to function efficiently,

Question 13. What is the most common shape of protein that permits it to exist within the plasmalemma?

Answer 13. Proteins that span the plasma membrane or that insinuate themselves in one side of the membrane usually have an alpha-helical structure.

Question 14. What functional type of protein typically has multiple transmembrane spanning regions? Why do they do this?

Answer 14. Ion channels create fluid-filled (hydrated) pores through which ions can cross the membrane.