Cell Bio Final

Front 1

What are the 4 basic properties of cellular membranes?

Back 1

Fluid, closed compartments, semi-permeable, and asymmetric (with reference two the content of the individual layers)

Front 2

What are the 3 basic components of membranes?

Back 2

Lipids, sterols and proteins.

Front 3

Which of the following fatty acids would be expected to have the lowest melting point:

a) C 16:0

b) C 16:1

c) C 18:0

d) C 18:1

Back 3

b) C 16:1

Shorter and more unsaturated means less VDW forces and a lower MP.

Front 4

Which of the following is not regulated to control cell membrane fluidity:

a) Cholesterol content

b) Degree of unsaturation

c) Length of phospholipid fatty acid tail

d) Temperature

Back 4

d) Temperature

Front 5

We are observing GFP labelled and bleached membrane proteins in a human brain cell (live and in the body). Which of the following is the least likely explanation as to why we would observe 50% fluorescence recovery (i.e. 50% mobility) rather than 100% recovery:

a) Temperature was not high enough to make the membrane 100% fluid

b) 50% of the proteins bleached were attached to the cytoskeleton

c) The brain cell did not contain enough cholesterol to cause 100% mobility

d) None of the above

Back 5

a) Temperature was not high enough to make the membrane 100% fluid

Temperature is not a regulatory element w.r.t membrane fluidity.

Front 6

Which of the following transmembrane proteins have a cytosolic N terminal?:
i) Type 1

ii) Type 2

iii) Type 3

iv) Type 4

v) Tail anchored

vi) GPI linked

Back 6

ii) Type 2, v) Tail anchored

(And type 4 A)

Front 7

How many of the following proteins are involved in secondary active transport:

i) Calcium-ATPase

ii) Na+/K+ ATPase

iii) Na+/Glucose Symporter

iv) GLUT1/2

Back 7

ii) Na+/K+ ATPase and iii) Na+/Glucose Symporter

Front 8

What is the effect of Acetylcholine on a muscarinic acetylcholine receptor?

Back 8

Muscarinic acetylcholine receptor is a GPCR that leads to the opening of K+ channels and will cause a decrease in heart rate.

Front 9

Explain the pathway that occurs upon ingestion of Cholera infected water.

Back 9

Once cholera is in the stomach/intestines it begins producing cholera toxin. Cholera toxin is imported into the cells via endocytosis. Once in the cell the toxin acts as a GEF, in that it promotes the G stimulatory protein to disassociate with GDP and bind ATP, thereby activating it. Once activated the G protein will activate adenylyl cyclase, which will produce an unregulated amount of cAMP. cAMP is a cofactor for CFTR, and the high amounts of cAMP will cause Cl to be pumped out of the cell. A Cl gradient will cause Na to flow out of the cell as well to balance the charge gradient. Osmosis will cause water to follow. The effect of all this is water flow into the intestine causing diarrhea and dehydration which can be lethal.

Front 10

Explain the pathway that occurs upon inhaling Bordetella pertussis.

Back 10

Inhaling Bordetella pertussis will lead to the production of pertussis toxin in the lungs. The toxin will be imported into the cell by endocytosis. The toxin functions by inhibiting the G inhibitory proteins. Without the inhibition proteins the stimulatory G protein will be unchallenged and cause over stimulation of adenylyl cyclase, producing cAMP. As cAMP is a cofactor of CFTR, the high concentration of cAMP will cause the over activation of CFTR and pump too many Cl ions across the membrane into the lungs. Na ions (by potential) and water molecules (by osmosis) will also move into the lungs causing a build up of fluid. You must cough to rid your lungs of the fluid.

Front 11

Explain the pathway that occurs when you see a big ass bear chasing you.

Back 11

First epinephrine is produced and secreted into the lungs. When epinephrine binds to the appropriate GPCR, which is on various types of cells, the G protein ⍺ subunit will disassociate with the β,𝛾 subunit and become active. The active ⍺ subunit will then activate the effector protein adenylyl cyclase, which in turn begins producing cAMP. cAMP then builds up un the cytosol and will bind to the regulatory subunits of PKA in a complementary binding fashion. The regulatory subunits then detach from the catalytic subunits, it is now active PKA. PKA is a kinase and it is involved in phosphorylating various proteins, the end result is shutting down the glycogen production pathway and activating the glycogen breakdown pathway to make glucose. Then some other stuff happens to reverse it involving an active PP (non phosphorylated).

Front 12

Explain a long term pathway associated with GPRC (CREB pathway).

Back 12

Same beginning as above question. The active PKA will go into the nucleus and phosphorylate CREB (to activate it). CREB is a DNA binding protein and transcriptional factor. It binds a specific sequence that I don't think we have to know. It can directly result in transcription increase or recruit more machinery.

Front 13

Explain the pathway that follows from acetylcholine being introduced to epithelial cells (near smooth muscle). Be detailed bisch.

Back 13

Acetylcholine will bind the appropriate GPCR and lead to activation of the G protein ⍺ subunit. The G protein then activates phospholipase C which will catalyze the cleavage of PIP2 to make IP3 and DAG. IP3 is cytosolic while DAG is membrane bound. Now the IP3 will go to the ER and bind to IP3 gated Ca Channels causing an outflow of Ca ions from the ER into the cytosol. Calcium then binds either PKC or calmodulin. If it binds PKC it will be partially activated and move to the membrane to bind to DAG and become a fully activated protein kinase. If Ca binds to calmodulin then calmodulin will then go and activate NO synthase, which catalyzes the production of NO and citrulline from arginine. NO is small and non-polar so it freely diffuses through the cell membrane into the adjacent smooth muscle cells (paracrine). Once in the smooth muscle cells the NO is a cofactor for guanylyl cyclase which will catalyze the production of cGMP from GMP (note that PDE catalyzes the reverse reaction and is inhibited by viagra). cGMP binds to PKG and then somehow causes muscle relaxation and vasodilation.

Front 14

Explain the pathway that follows the binding of EGF to EGF receptors

Back 14

First EGF binds to a EGFR monomer. This causes a conformational change and two monomers associate to become a functional dimer (RTK). This dimerization causes the activation lip to be phosphorylated, followed by a few more auto phosphorylations. The phosphate groups serve as docks to bind adaptor proteins, specifically SH2 and two SH3. The adaptor proteins collectively called GRB2 can then bind to sos. Then sos binds to Ras and acts as a GEF leading to GTP binding Ras and activating it. Now Ras can go activate a non-active Raf complex. This activation involves the dephosphorylation of Ras and also Raf. When Raf is dephosphorylated 14-3-3 can no longer bind and inactivate it, thus Raf is now active. Raf is a kinase and phosphorylates MEK. MEK is also a kinase and phosphorylates MAPK. MAPK then phosphorylates and does other stuff to activate gene expression and stuff. Summary Ras -> Raf -> MEK -> MAPK

Front 15

Explain the process of apoptosome formation.

Back 15

In response to various stimuli pores in the mitochondrial proteins can be formed and opened (Bax, Bak etc). If this occurs cytochrome c will diffuse out of the mitochondrial matrix and dimerize with Apaf-1. 7 of the dimers will then form a heptamer (wheel of death). Then a caspase 9 dimer will join to the heptamer forming the final functional apoptosome.

Front 16

Explain apoptosis from DNA damage, from cytoskeletal disruption, from a lack of trophic factors and from extrinsic cell signalling.

Back 16

If DNA damage occurs ATM can cause the phosphorylation of p53. If p53 is phosphorylated it will cuase the transcription of Puma (p53 is a transcriptional factor). Puma (BH3 only) will bind to Bcl-2 removing it from inhibiting Bak/Bax. Bak/Bax can then polymerize with some others in the mitochondrial outer membrane and form a pore. The pore will allow cytochrome c to escape and eventually form the apoptosome and cleave procaspase-3 to make caspase-3 and cause apoptosis. Same process for cytoskeletal disruption except instead of puma Bim in the BH3 only protein. For the trophic factors, when present trophic factors binding will cause the activation of PI-3 kinase, which activates PKB. PKB ensures Bad, another BH3 only protein, is phosphorylated such that it can bind to 14-3-3 and remain inactive. If there are no trophic factors Bad is active and will bind Bcl-2 activating Bak/Bax and normal apoptosis process occurs. For extrinsic cell signalling, Fas-ligand can bind a Fas receptor of another cell and the signal will activate FADD which will cleave procaspase 8 to make caspase 8 which is an initiator caspase. Caspase 8 will cleave caspase 3,6 and 7, which are effectors and cause apoptosis. Furthermore caspase 8 also cleaves BID into t-BID (another BH3 only protein). BID can then bind to bcl-2 and activate the regular apoptosis pathway.

Front 17

Which of the following are true for the Raf protein:

i) It is monomeric

ii) It is a G protein

iii) Low GTPase activity

iv) Mutation at Glycine-12 causes cancer

Back 17

All.

Front 18

What are the 4 main things effector caspases will digest?

Back 18

Inhibitors of DNAase, nuclear lamins, golgi apparatus and cytoskeletal components.

Front 19

For each of the following lipid linked proteins, which way do they face, which terminal is and at what amino acid is the protein bound to the lipid?

i) Prenylation

ii) Acylation

iii) GPI anchored

Back 19

i) In prenylation the C terminal is linked to the lipid by a cysteine residue. The protein is on the cytosolic leaflet.

ii) In acylation the N terminal is linked to the lipid by a glycine residue. The protein is on the cytosolic leaflet.

iii) In GPI anchored proteins, the C terminal of the protein is linked to the lipid with some sugars and stuff in between. The protein is attached to the exoplasmic leaflet.