Exam 3

Question 1

Aequorin

Answer 1

Ca2+ sensitive protein which oxidizes coelectrazine whene near calcium. Amount of the fluorescent is related to amount of calcium

Question 2

Ca2+ atpase

Answer 2

Uses e very from atp hydrolysis to transport calcium against concentration gradient

Question 3

Stuides on calcium 2+ release

Answer 3

There is an initial burst and then a plateau. The Burt coming from the intracelular stores which come in waves and the plateau is calcium coming across the plasma membrane.

Question 4

What happens with each wave of released calcium

Answer 4

Each wave releases more calcium. There is a feed forward mechanism that when calcium reaches a threshold the system will turn itself of and pump calcium out of cell back into the lumen of the Er

Question 5

Ligand binds to a &TMR calcium pathway

Answer 5

This will active g alpha q then activates PLC-B where it will cleave PiP2 which results in DAG and IP3. THe IP3 will bind the Ligand calcium channel in the membrane and open it to release calcium from the ER lumen and increase in the cytoplasm

Question 6

Structure and function of IP3 receptor that is a resultant of PiP2 being cleaved

Answer 6

It is a homotetramer that has 3 functional domains. Looks like 4 cylinders with 4 eggs on top. These 4 eggs (subunits) make a channel that calcium can pass through. Important the pore is similar to to volgated gated channel that have a selectivity loop and a gate between helix 5 and 6

Question 7

When the IP3 receptor is inactive what holds the gate closed

Answer 7

When closed there is interaction between suppressor domain and gates keeper helices 5 and 6

Question 8

How it IP3 receptor activated

Answer 8

The IP3 will bind the IP3 binding core. This binding site functions as a clamshell and work by interacting negative phosphate with positive aas which will close the shell. When closed the binding site for calcium is formed. When calcium bind it will interrupt the interaction with the suppressor domain and the gate keeper helices. Calcium is then released from er and into cytoplasm

Question 9

Earlier it was mentioned that with each release of calcium it got bigger and bigger why?

Answer 9

Because each binding of IP3 causes the binding of the next IP3

Question 10

How it calcium depletion prevented

Answer 10

When calcium in lumen is high the IP3 has a high affinity for IP3-> channel opening. As luminal calcium decreases the affinity decreases and the channel will close

Question 11

Explain gas exchange

Answer 11

Occurs in capillaries where red blood cells drop of O2 and pick up Co2 deoxy blood is carried back to heart via venules and veins

Question 12

Explain the structure of artery

Answer 12

Has endothelial cells that line the inner lumen. Smooth muscle on the outside

Question 13

Explain briefly vasoconstriction and vasodilation

Answer 13

When smooth muscle contracts it make hard for blood to move increase blood pressure

Relaxation of the smooth muscle resulting in easier blood flow and decrease blood pressure

Question 14

What is the difference between skeletal muscle and smooth muscle

Answer 14

Smooth has no troponin

Question 15

The head of myosin

Answer 15

Have energy stored in the heads that use it to talk along actin and result in contraction. When phosphorylate the myosin light chains kinase releases the myosin tail and results in spontaneous self assembly of the myosin thick filament

Question 16

Calmodulin activation/ function

Answer 16

It is a calcium sensor protein with 2 ef hands at each end. When calcium is absent the helix of calmodulin is inaccessible. When calcium bind the the Ef hands it results in a conformation change which will expose the central alpha helix.

When this happens the helix will slightly unwind hinge and wrap around the target kinase. This results in activation of kinase and phosphorylation of downstream targets

Question 17

How does smooth muscles contract

Answer 17

First calcium will bind calmodulin which will bind. Myosin light chain kinase and phosphorylation light chains which will form myosin filaments. Actin and myosin will interact and contraction which will increase the blood pressure

Question 18

Nitric Oxide is a

Answer 18

Signaling molecule

Question 19

How is Nitric O synthesized and what is its role

Answer 19

Acetylcholine released from nerves which binds to 7tmr this activates g alpha q activates PLC-B cleaves PIP2 to give DAG and IP3. IP3 travels to the er to bind IP3 receptors and realease calcium that will bind calmodulin and activate nitric oxide synthase

Question 20

How is guanylyl cyclase activated

Answer 20

Nitric oxide diffuses out of endothelial cells and into smooth muscle. In the muscle is soluble guanylyl cyclase. These have

Catalytic domains- similar in structure or function to adenyl cyclase

Regulatory domains contain Fe containing hemoglobin

Nitric oxide will bind to the heme group and active 5GC and increase cGMP

C GMP wil bind on the regulatory domain of PKG which will free up the catalytic domain to phosphorylate downstream targets

Question 21

What breaks down cGMP and what inhibits it

Answer 21

Phosphodiesterase, viagra

Question 22

What causes an erection function of viagra

Answer 22

Result of nitric oxide valsodilations which supply the penis and enlarges corpus cavernousum. Erection stays until cGMP decrease due to phosphodiesterase

Viagra blocks phosphodiesterase so that cGMP cam can stay long in the system and result in longer errection

Question 23

Adenyl cyclase structure

Answer 23

Has
M1 domain 6 transmembrane helices separated by short intra and extra cellular loops
C1a loop 1/2 of enzyme active site
C1b connects back up to membrane
M2 6 transmembrane helices seperated into intra and extra cellular loops
C2 long cytoplasmic tail
C2a 1/2 enzyme active site
C2b end of protein

Question 24

Explain the wreath like structure of adenyl cyclase

Answer 24

ATP bind to the top of the wreath between the c1 and c2 subunits and is activated by g alpha q
The switch of g alpha q goes through conformation change when bound to either gdp or GTP and interacts with c2a at the bottom of the wreath

Question 25

How does g alpha s interact with adenyl cyclase to from camp

Answer 25

Switch 2 pushes against c1 and rotates the wreath clockwise and open site for atp. When atp bind another conformation change where pyrophosphate is displaced and camp is formed

Question 26

What is forskolin and how does it work

Answer 26

It is a chemical from coleus plant that binds at bottom of adenyl cyclase wreath of c1 and c2 which rotates clockwise and activates adenyl cyclase in abscent of G protein

Question 27

How is adenyl cyclase inhibited

Answer 27

This happens when g alpha i blocks atp binding by inserting into the c1a of the wreath which further prevents formation of camp

Question 28

How is adenyl cyclase deactivated

Answer 28

It does so via feedback communication with g alpha s. Gaps then hydrolyze GTP to gdp which causes it to return back to original conformation. G alpha s will dissociate from ac and reassociate with beta gamma which deactivates atp binding units reactivated

Question 29

Why are 2nd messengers important

Answer 29

Server as amplification Distribute message away from membrane

Question 30

Regulation of lac operan

Answer 30

Camp bind with protein called cap. The combo bind to promoter on lac operon which codes for enzyme to metabolize lactose

Question 31

Explain camp signaling in dictyostelium

Answer 31

Secreted camp bind to a 7TMR which will activate a G protein and activate guanylyl cyclase and increase cGMP. Adenyl cyclase is then activated to release camp and release a signal to attract more cells to growing mound. Feed forward mechanism which is products of reaction stimulate more product to be made

Question 32

PKa is a what that does what and talk about structure

Answer 32

Ser/thr kinase that phosphorylates target proteins. The ser/thr to be phos must be in the consensus sequence Has regulatory subunits and catalytic subunits

Question 33

Explain why a pseudo substrate would prevent enzymatic activity

Answer 33

Active site of pKa will bind pseudo substrate but if there is no ser thr on it then the subunit cant be phosphorlated and released from the active site

Question 34

Activation by camp when binding pKa

Answer 34

Each subunit contains binding sites for camp. When adenyl cyclase makes the camp it binds to the subunits of pKa and result in conformation change which decrease affinity for pseudo sub so that the two subunits of pKa dissociated so that real substrate can bind and phosphorylate targets

Question 35

How is PKa inactivated

Answer 35

Camp dissociates and the pseudo substrate binds back to the subunit to block further interaction of pKa

Question 36

Mechanism of pKa and transcription activation

Answer 36

The active pKa subunits move to nuclear pore and phosphorylate TXN factor know as creb. The Phospho creb bind to promoter of camp. When the se interact it determines when a gene is transcribed. CREB will only bind to certain dna called camp response element. When bound to promoter activate TXN and binding of RNA pol II

Question 37

What are the functions of the 4 phospholipases

Answer 37

A1 cleaves the first ester bond A2 cleaves the 2nd Ester bond Phospholipase c cleaves infront of the phosphate Phospholipase d cleaves behind the phosphate

Question 38

Phospholipase C

Answer 38

Cleaves IP3 and DAG

Question 39

IP3 and DAG

Answer 39

Both are hydrophobic 2nd messengers. IP3 causes the release of calcium from the lumen into the ER. DAG activates protein kinase c which will phosphorylate downstream protein targets on ser/thr kinases

Question 40

PLC isotopes are activated by

Answer 40

Ca2 plc Heterotrimeric G proteins Tyrosine kinase receptors Cytosolic G proteins PLC

Question 41

How is PLC beta interact with G alpha q

Answer 41

Ligand binds to 7tmr where g alpha q exchanges gdp for GTP and separates from beta gamma. G alpha q-GTP interact with the c terminal trial from caltalytic core that allows the catalytic barrel to push up into membrane where Pip is cleaved to give IP3 and DAG

Question 42

Inactive PKC

Answer 42

Activation loops is phosphorylated by pseudo substrate ligand will bind to 7tmr resulting in a conformation change in the 3rd cytoplasmic loop where the receptor will insert in the camp between g alpha q. Gdp pops out and takes place of gdp changing the conformation of switch 2 of g alpha q. It separates from beta gamma and interact with the terminal tail of PLCA and ultimately cleave IP3

Question 43

Active PKC

Answer 43

The c4 and c3 s subunit swing down from the hinge region and expose the catalytic domain so that appropriate response can be carried out

Question 44

Macrophage

Answer 44

Tissue cell that protect body from invasion of micro as bacteria and virus

Question 45

Infected cells are destroyed by what mechanism

Answer 45

Free radicas that steal electrons from nearby cells. Therefore production is strictly regulated by phagocyte oxidase enzyme

Question 46

The phagocyte oxidase enzyme structure

Answer 46

Made of 5 subunits 2 of which are membrane bound, and also has 2 sH3 domains

Question 47

Mechanism of phagocyte oxidase

Answer 47

Microbe bind to 7tmr which activate g alpha q, activates PLC B resulting in DAG increasing ca2 levels, this activate PKC to phosphorylate p47phox to conformation change and revels the sH3 domain, the phox22 interacts with the subunits of the membrane to make fully assembled active phago oxidase