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Biochem > Lecture 11 Information > Flashcards

Lecture 11 Information Flashcards

1
Q

What determines interactions between the ligand and receptor?

A

weak interactions

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2
Q

What are components of sensitivity?

A

high affinity

cooperativity

amplification of signal

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3
Q

Cooperativity in ligand binding receptor

A

refers to large changes in receptor activation with small changes in ligand concentration (allostery)

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4
Q

Desensitization

A

cells need to be able to down regulate signal transduction pathways

Receptor activation triggers a feedback inhibition circuit that shuts off the receptor or removes it from the cell surface

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5
Q

Integration

A

the cell has to look at the sum of all the different messages it is receiving and determine a response

some receptors could be sending opposing signals

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6
Q

List the different types of signal transduction mechanisms (for our class)

A

1) G-protein coupled receptors
2) Receptor tyrosine kinases
3) Receptor guanylyl cyclase
4) Internal receptors

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7
Q

What are the 3 components of G-protein coupled response?

A

Plasma membrane receptor that binds the ligand

Intracellular g-protein

Effector enzyme that gets turned on as a result of this process

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8
Q

What is the receptor of the GPCR pathway made of?

A

7 transmembrane structures, mostly alpha helices, some beta-pleated sheets

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9
Q

G-protein subunits

A

alpha, beta, and gamma subunits

usually found in the inactive form and bound to GDP

when GDP converts to GTP, the alpha subunit detaches

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10
Q

Epinephrine mechanism

A

binds to specific receptor on the cell’s surface and triggers a conformational change in the g-protein

GDP gets converted to GTP and the alpha subunit detatches

the alpha subunit activates adenylyl cyclase which catalyzes the formation of cAMP

cAMP serves as a secondary messenger to activate protein kinase A

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11
Q

Protein Kinase A

A

allosterically activated by cAMP

starts a phosphorylation cascade of enzymes that catalyze the removal of glucose from glycogen

glucose can be used in the bloodstream for energy during flight or fight response

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12
Q

Different types of G-protein coupled receptors

A 
stimulatory form (Gs)
inhibitory form (Gi)
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13
Q

Inactive form of tyrosine kinase receptor

A

monomers

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14
Q

Active form of tyrosine kinase receptor

A

dimerized

activated through phosphorylation cascade

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15
Q

Autophosphorylation

A

tyrosine kinases ability to phosphorylate and activate the tyrosine residues on itself

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16
Q

Examples of tyrosine kinase receptors

A

insulin and epidermal growth factor (EGF)

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17
Q

Receptor guanylyl cyclases

A

have an extracellular component that is able to bind the ligand

have an intracellular component that works directly as an enzyme and cyclizes GMP (cGMP)

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18
Q

NO-activated version of guanylyl cyclase

A

doesn’t have attachment to a transmembrane protein

important for smooth muscle relaxation because it converts GTP to cGMP

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19
Q

Viagra

A

inhibits an enzyme, phosphodiesterase, that would degrade cGMP

leads to higher levels of cGMP and an erection

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20
Q

Nuclear receptors

A

proteins in the nucleus or cytoplasm that respond to steroid hormones, retinoic acid, and thyroid hormone

alter gene expression by directly binding to DNA

21
Q

Thyroid hormone

A

needs to use a protein channel to cross the membrane in order to reach a nuclear receptor

cannot cross the membrane on its own

22
Q

How fast do nuclear receptors work?

A

slowly

puberty takes years for steriod hormones to work

23
Q

Estrogen

A

needs a carrier protein to transport since it can’t dissolve in the blood

binds a cytoplasmic receptor and then the receptor goes to the inside of the nucleus where it can directly interact with DNA

24
Q

Phosphodiesterase

A

breaks down cAMP by converting it to AMP

desensitizes the epinephrine pathway

25
Q

Cholera inhibits …

A

inhibits the ability of the g-protein’s alpha subunit to convert GTP to GDP

the pathway stays activated and get more and more cAMP

26
Q

What happens when cAMP builds up with cholera?

A

stimulates an epitheal cell that lines the intestine to take chloride from inside the cell and put it in the lumen of the intestine

water follows Cl- and Na+ and will build up in the lumen of the intestine

too much water in stool and will become dehydrated quickly

27
Q

Why does cholera want to excrete large amounts of water?

A

the toxin gets flushed out of the body and enters the water where it can infect more people

spreading itself to suitable hosts

28
Q

Pertussis toxin

A

prevents GDP from converting to GTP

still leads to over production of cAMP (not sure)

29
Q

Calmodulin

A

regulatory subunit of calcium dependent enzymes

30
Q

When guanlyl cyclase make cGMP what type of bond to they make?

A

a phosphate ester

31
Q

Acetylcholine

A

triggers the opening of a ligand-gated ion chanel

acetylcholine is positively charged

acetylcholine mainly produces conformational changes

32
Q

Why do steriod hormones use carrier proteins?

A

they are too hydrophobic to dissolve in the blood by themselves

33
Q

Steriod hormone response elements

A

are sequences in the DNA that when bound to the receptor-hormone complex trigger transcription

34
Q

Transducin

A

a G-protein involved in visual signal transduction

35
Q

Myosin

A

an example of a type of protein that can be phosphorylated by cyclin-dependent protein kinases

36
Q

Amplification

A

small amounts of signal will trigger phosphorylation cascades that result in big intracellular changes

37
Q

How does cholera activate the alpha-subunit of the g-protein?

A

ADP-ribosylation which is a type of covalent modification

38
Q

What regulates protein kinase C?

A

DAG and Ca2+

39
Q

What proteins are phosphorylated in response to insulin?

A

IRS-1

phosphatidyl inositol-4,5-bisphosphate

40
Q

Do cyclins catalyze the phosphorylation of proteins?

A

no

41
Q

Glycogen synthase kinase

A

inhibits glycogen synthase

42
Q

SH2 domains bind sequences containing

A

phosphotyrosine

43
Q

What does cAMP do in cholera pathway? (according to textbook)

A

regulates Na+ levels

44
Q

What is a possible treatment for cholera?

A

replace fluids and electrolytes

45
Q

Vassopressin

A

a peptide hormone

triggers vasoconstriction (opposite of Viagra causing increased blood flow and vasodialation)

vassopressin acts by elevating Ca2+ levels as a secondary messenger

46
Q

Describe all the sources of amplification in the insulin receptor system

A

in order, insulin receptor, IRS-1, Raf, MEK, ERK;

ERK activates a transcription factor, which stimulates mRNA production.

47
Q

Examples of secondary messengers

A

cAMP and Ca2+

48
Q

cGMP

A

triggers vasodilatation, increasing blood flow and causing an erection

49
Q

RNA polymerase

A

binds to the promoter with help from nuclear receptors

controls gene expression

Biochem (20 decks)

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