3 nonenzymatic protein function and protein analysis

Question 1

In which way do kynesins and dyneins move?

Answer 1

Kynesins bring things along microtubules to the positive end (e.g. towards the synaptic terminal in neurons)

Dyneins brings things along microtubules to the negative end (e.g. bringing waste back from synpase to soma).

Question 2

What are the three types of cell adhesion molecules (CAMs)?

Answer 2

Cadherins: glycoproteins that mediate calcium-dependent cell adhesion. Holds similar cells together (e.g. epithelial cells in epithelial tissue)

Integrins: alpha and beta two membrane spanning chains that help cell interact with extracellular matrix (e.g. involved in clotting)

Selectins: Bind to carbohydrate molecules that project from other cell surfaces. Expressed on white blood cells and epithelial cells. Involved in inflammation.

Question 3

Antibodies are a type of immunoglobulin produced by b cells have a polypeptide sequence at the end of one light chain arm called the antigen-binding site that can recognize antigens and bind them to V domain (other light chain arm).

When antibodies bind to antigens what are three things they can then do?

Answer 3

• Neutralize the antigen, making the pathogen or toxin unable to exert its effect on the body
• Marking the pathogen for destruction by other white blood cells immediately (opsonization)
• Clump together (agglutinating) the antigen and antibody into large insoluble protein complexes that can be phagocytized and digested by macrophages.

Question 4

Which molecules cannot easily pass through cell membranes and must use facilitated diffusion? (3 criteria)

Answer 4

• Large
• Polar
• charged

Question 5

What are the three types of ion channels involved in facilitated diffusion?

Answer 5

• Ungated channels
• Voltage-gated channels (regulated by membrane potential)
• Ligand-gated channels (e.g. channels at the postsynaptic membrane, GABA binds to a chloride channel and opens it).

Question 6

In electrophoresis, in which direction to anions and cations move?

Answer 6

Cations move towards the cathode (negative polarity)

Anions move towards to anode (positive polarity)

Question 7

What is the difference between PAGE (polyacrylamide gel electrophoresis) and SDS-PAGE?

Answer 7

SDS-PAGE uses sodium dodecyl sulfate and separates only on the basis of relative molecule mass alone. SDS neutralizes the protein and denatures it.

Question 8

Which direction will an acidic protein move on a polyacrylamide gel that is set up for isoelectric focusing?

Answer 8

An acidic protein will move towards the anode because the anode has a positive charge and the negatively charged hydroxides associated with an acid will attract it towards the cathode.

Question 9

Out of electrophoresis and chromatography, which allows separated proteins to be isolated, purified, identified, and quantified?

Answer 9

Chromatography. It is the method of choice for large amounts of protein separation.

All chromatography is about the affinity of a substance for the mobile and stationary phases, except for size-exclusion chromatography