High Yield for Midterm Last Minute

Question 1

Describe the pathway of the serine/threonine kinase receptor

Answer 1

1. TGF-B binds to the extracellular region of the type II receptor causing it to dimerize with the type I recepter.
2. The type II receptor phosphorylates and activates the type 1 receptor
3. The activate type I receptor binds and phosphorylates SMAD
4. Phosphorylated SMAD leaves the receptor and binds coSMAD and translocates to the nucleus
5. This results in the inhibition of epithelial growth

Question 2

Describe the pathway of Janus Kinase receptors

Answer 2

1. Cytokines (INFy, IL) bind to a receptor which is continuosly bound to JAK
2. The receptor dimerizes with another receptor and the JAKs phosphorylate each other.
3. The Phosphorylated JAKs phosphorylate a tyrosine on the receptor creating an SH domain.
4. STAT binds and is phosphorylated
5. Phosphorylated STAT dimerizes and heads to the nucleas to activate transcription

Question 3

What is a major disease that occurs when the JAK/STAT pathway is blocked?

Answer 3

Severe Combined Immunodeficiency Disease results becasuse the JAK/STAT pathway of the cytokines is critical for the differentiation of the agranulocytic leukocytes lineages

Question 4

Describe the action of tyrosine kinase receptors for EGF

Answer 4

1. EGF binds causing the receptor to homodimerize
2. Receptors phosphorylate tyrosine residues on each other creating SH domains
3. GRB2 binds which causes SOS to exhange GDP for GTP on RAS
4. Activated RAS binds RAF (MAPKKK)
5. MAPKKK phosphorylates to MAPKK and MAPKK phosphorylates to MAPK which activates transcription factors and turns on genes

Question 5

What happens when there is excess HER2 present in the membrane?

Answer 5

HER2 dimerizes with the receptor for EGF and starts the RAS/RAF pathway leading to cellular proliferation and cancer (this is the cause of 30% of breast cancer)

Herceptin can block HER2 helping to keep this from happening

Question 6

Describe the insulin receptor pathways

Answer 6

1. Insulin receptor has 2 subunits, the intracellular subunits phosphorylate one another when insulin binds
2. The phosphorylate B subunit binds IRS which it phosphorylates on a tyrosine to form an SH domain
3. IRS can bind GRB2 (RAS/RAF), PLCy (DAG/IP3), or PI3 kinase which adds a phosphate to PIP2 to form PIP3
4. PIP3 binds PDK1 and ACT which phosphorylates akt causing the number of glucose transporters to rise on the membrane

Question 7

Describe the mechanism of action of GPCRs

Answer 7

1. Ligand binds to receptor causing it to phosphorylate GDP attached to Ga subunit into GTP
2. The Ga subunit dissociates from the receptor and from Gb and Gy subunits and binds to Adenelyl cyclase
3. AC causes the production of more cAMP which activates PKA and causes glucose production in the muscle and liver (when glucagon binds)

Question 8

What happens when cholera is present?

Answer 8

Cholera prevents the Ga subunit from automatically hydrolyzing bound GTP to GDP. This results in overproduction of cAMP and overstimulaton of the CFTR which causes Chloride to leak into the lumen. This binds with NaH to form salt causing the cells to secrete water into the lumen resulting in diarrhea.

Question 9

Pertussis does what?

Answer 9

Pertussis prevents the Gai subunit from binding to adenylyl cylclase in the lungs resulting in the overexpression of cAMP. It is not well understood how this contributes to disease.

Question 10

What is special about the Gaq subunit?

Answer 10

1. It turns on phospholipase C resulting in the conversion of PI2 to DAG and IP3. This causes the release of calcium into the cell and also the phosphorylation of a number of proteins increasing cellular activity.

Question 11

To what kind of receptor does Acetylcholine bind?

Answer 11

Ion receptor

Question 12

To what kind of receptor does Angiotensin II bind? What inhibitor prevents this?

Answer 12

GPCR, ACE inhibitors block the conversion of Angiotensin I to Angiotensin II

Question 13

What is the equation for the relative risk? Is it for cohort or case control studies?

Answer 13

Relative Risk Ratio = (A/A+B)/(C/C+D), it is used in cohort studies (it is the incidence)

Question 14

What is the equation for Prevalence Ratio, what kind of studies is it used in?

Answer 14

PR = (A/A+B)/(C/C+D), Cross sectional studies

Question 15

If the relative risk is less than 1 what is it called?

Answer 15

The protective effect

Question 16

What is the equation for attributable risk?

Answer 16

AR = Iexp - Iunexp, this is used in cohort studies to determine the risk that is associated with the behavior

Question 17

What is the equation for population attributable risk?

Answer 17

PAR = Prevalence of Exposure x AR, it is used to determine the number of diseased cases that are caused in a population by the risk factor

Question 18

What is the formula for an odds ratio? What is it used for?

Answer 18

It is used for case control studies, OR = (A/C)/(B/D) = AD/BC

Question 19

What does an OR greater than 1 indicate?

Answer 19

Increased Risk

Question 20

What is secreted by normal endothelium to inhibit formation of thrombosis?

Answer 20

1. TPA breaks down fibrin
2. NO, PGI2 and ADP prevent platelet aggregation and promote vasodilation
3. Tissue Factor Pathway Inhibitor inhibits the extrinsic pathway preventing clot formation
4. Heparin-like molecule binds antithrombin III to prevent activity of thrombin
5. Thrombomodulin binds thrombin and stimulates protein C and protein S which inhibit Factor V and factor VIII

Question 21

What is sensitivity of a test?

Answer 21

How many does it catch that have the disease? TP/TP+FN

Question 22

What is specificity?

Answer 22

TN/TN+FP

Question 23

What is false negative rate?

Answer 23

FN/FN+TP

Question 24

What is false positive rate?

Answer 24

FP/FP+TN

Question 25

When do you want a specific test?

Answer 25

When a false negative is worse than a false positive