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Biochemistry > Final Review > Flashcards

Final Review Flashcards

1
Q

How does insulin activate glycogen synthase?

A

By inactivating GSK3 & activating PP1

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2
Q

Glucagon stimulates _________ and _________ while blocking glycolysis

A

glycogen breakdown and gluconeogenesis

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3
Q

What does it mean to say the membrane lipid bilayer is amphipathic

A

it contains both hydrophilic and hydrophobic regions

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4
Q

What metabolite links glycolysis and CAC?

A

pyruvate

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5
Q

Epinephrine causes an _______ of blood glucose levels while insulin causes an ________ of BGL

A

epinephrine causes an increase of BGL and insulin causes a decrease

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6
Q

main composition of lipid bilayer

A

phospholipids & sphingolipids

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7
Q

which leaflet of the membrane is more positively charged

A

outer leaflet

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8
Q

what enzymes catalyze trans bilayer flip flop diffusion of lipids

A

lipid translocators (flippases, floppases, scramblaes)

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9
Q

Lipid raft composition

A

glycosphingolipids and cholesterol

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10
Q

How is the membrane able to undergo fusion with other membranes w/out losing continuity?

A

changes in curvature
* curvature is required for cell fusion

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11
Q

GPCRs are active when

A

GTP bound

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12
Q

2nd messengers

A

cAMP, diacylglycerol, IP3 or Ca2+
- either inhibit or activate one or more downstream targets usually protein kinases

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13
Q

What does it mean that stimulation of adenylyl cyclase is self-limiting

A

Gs alpha has intrinsic GTPase activity that switches Gs alpha into its inactive form by converting the bound GTP for GDP
** stimulated by GTPase activator protein

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14
Q

3 ways to terminate the Beta Adrenergic System

A
  1. desensitization - [epinephrine] in blood drops below the Kd for its receptor
  2. Hydrolysis of GTP–>GDP via intrinsic GTPase activity
  3. removing cAMP
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15
Q

_____ Hormone made in the adrenal glands that mediates the body’s stress response by mobilizing E in the form of glucose
– causes an increase in blood glucose levels

A

epinephrine

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16
Q

_____ causes a decrease in blood glucose levels

A

insulin

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17
Q

How does cAMP activate PKA

A

cAMP binds at the two R subunits causing them to undergo a conformational change that moves the autoinhibitory domain out of the catalytic domain causing the two R2C2 complex to dissociate and yield two catalytically active C subunits

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18
Q

PLC cleaves PIP2 into what two things

A

Diacylglycerol and IP3

IP3 causes the release of Ca2+ and together with Diacylglycerol, Ca2+ and DAG activate pKC

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19
Q

What molecules regulate the desensitization of the epinephrine pathway

A

BARK and Beta Arrestin

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20
Q

PKA is localized to particular structures by its anchoring/adaptor protein _____

A

AKAP5

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21
Q

Why are the inside of cells negatively charged

A

due to the asymmetric transport of cations by the NA+K+ATPase (3 Na+ go out as 2K+ come in)

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22
Q

what regulates the timing of the cell cycle

A

cyclin-dependent kinases

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23
Q

What are the first two steps of gluconeogenesis

A
  1. pyruvate converted to oxaloacetate via pyruvate carboxylase
  2. oxaloacetatee converted to PEP (phosphoenolpyruvate) via PEP carboxylase
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24
Q

Purpose of gluconeogenesis

A

allows for the generation of glucose when glycogen stores have been depleted (starvation/excercise)

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25
Q

Why does oxaloacetate need tot be converted into PEP or malate during gluconeogenesis?

A

b/c oxaloacetate cannot escape the inner mitochondrial membrane but malate,PEP and pyruvate can

26
Q

Hexokinase I,II,III are all regulated by?

A

Glucose-6-phosphate

27
Q

Hexokinase IV is regulated (inhibited) by

A

Fructose-6-phosphate

28
Q

What enzyme catalyzes the conversion of F-6-P to F-1,6-BP

A

PFK-1

29
Q

What increases PFK-1 activity (thus promoting glycolysis)

A

AMP & ADP

30
Q

What inhibits PFK-1, inhibiting glycolysis

A

ATP, citrate

31
Q

What converts PEP to pyruvate

A

pyruvate kinase +ADP and Pi

32
Q

Why is pyruvate converted into PEP

A

when fatty acids are available and when acetyl-coA signals that no more E production is needed

33
Q

products of the pentose phosphate pathway

A

NADPH & Ribose-5-phosphate which are necessary for producing fatty acids, cholesterol and sterols

34
Q

what inhibits pentose phosphate pathway

A

NADPH

35
Q

Transaminations - what is the cofactor and what is the enzyme

A

catalyzed by aminotransferases & PLP (pyridoxal phosphate) is the cofactor

36
Q

What is a transamination reaction

A

transfer of an alpha amino group from an alpha amino acid to an alpha-keto acid

37
Q

What is a transamination reaction?

A

transfer of an alpha amino group from an alpha amino acid to an alpha-keto acid

38
Q

What is the purpose of step 2 in glycolysis?

A

makes the next steps in the reaction require less energy –C1 of fructose is easier to phosphorylate by PFK , allows for symmetrical cleavage by aldolase

39
Q

What is the purpose of step 3 in glycolysis?

A

the 2nd phosphorylation converts fructose-6-phosphate to fructose-1,6-bisphosphate

– this is the first committed step of glycolysis…b/c fructose 1,6 bisphosphate is committed to becoming pyruvate

40
Q

What is the purpose of step 4 in glycolysis?

A

Step 4 is the aldol cleavage of a 6-carbon sugar into two 3-carbon sugars GAP and DAP

41
Q

What is the purpose of step 5 in glycolysis?

A

This step completes the preparatory phase of glycolysis - allows glycolysis to proceed to the payoff phase by a single chemical pathway

conversion of dihydroxyacetone phosphate to GAP (glyceraldehyde-3-phosphate)

42
Q

What is the purpose of step 6 in glycolysis?

A

– incorporates inorganic phosphate
– the first energy-yielding step in glycolysis, produced NADH

43
Q

Pathway that converts pyruvate (and its related 3 and 4 carbon compounds) to glucose

A

gluconeogenesis

44
Q

What molecules in gluconeogenesis are permeable to the mitochondrial membrane…which are impermeable

A

Permeable molecules = Malate, PEP, pyruvate

IMpermeable = oxaloacetate

45
Q

What is oxaloacetate converted to in order to allow for transport to the cytosol for gluconeogenesis?

A

oxaloacetate can be converted to PEP or malate

46
Q

A reason why gluconeogenesis is physiologically necessary

A

The brain, NS, and red blood cells can only generate ATP from glucose

47
Q

In mammals, where is the main site of gluconeogenesis

A

liver

48
Q

How is phosphofructokinase-1 (PFK-1) regulated?

A

PFK-1 is regulated by the binding of ATP to an allosteric site - this occurs when there is an excess in ATP

Citrate inhibits PFK-1 by increasing the inhibitory effects of ATP – causes a smaller concentration of ATP to seem like more

49
Q

How is (FBPase) fructose 1,6 bisphosphate ALLOSTERICALY regulated (inhibited)

A

high concentrations of AMP (low ATP) inhibit FBPase –> thus slowing glucose synthesis

high ATP concentrations slow glycolysis and speed up gluconeogenesis

50
Q

How does F26BP regulate PFK-1

A

Binds to PFK-1 and increases its affinity for fructose-6-phosphate

51
Q

Hows does F26BP regulate FPBase-1?

A

binds to FPBase-1 and REDUCES its affinity for substrate

52
Q

Under aerobic conditions what does pyruvate become?

A

pyruvate gets oxidized to acetyl-coA

53
Q

High ______ concentrations inhibit the committed step of glycolysis to prevent excess glucose degradation

A

ATP

54
Q

3 things that affect the rates of biochemical reactions

A
  1. Concentration of reactants
    Rate = k[reactants]
  2. activity of the catalyst
    the concentration of the enzyme & intrinsic activity of the enzyme
  3. Concentration of effectors
55
Q

What is the breakdown of cellular glycogen to glucose-1-phosphate ?

A

glycogenolysis

56
Q

What enzyme performs the isomerization of glucose 1-phosphate to glucose-6-phosphate

A

Phosphaglucomutase

57
Q

What substrate serves as the primer for glycogen synthesis

A

glycogenin

58
Q

What stimulates the conversion of phosphorylase b (inactive) into a (active)?

A

breaking down glycogen = cells need more E
* epinephrine (muscle activity)
* glucagon in liver

59
Q

What molecule converts glycogen synthase a (active) to synthase b (inactive) by adding phosphoryl groups to three serine residues on synthase a

A

Inactive glycogen synthase = stop using glucose to make glycogen

GSK3: Glycogen synthase kinase 3

60
Q

What inactivates GSK3 (which itself inactivates glycogen synthase)

A

insulin bc inslun says hey we have exttra glucose time to sttorage that bitch

61
Q

What must happen before glycogen synthase kinase 3 (GSK3) can phosphorylate glycogen synthase?

A

Casein Kinase II (CKII) must first phosphorylate the glycogen synthase on a nearby residue

62
Q

Glycogen breakdown is catalyzed by?

A

glycogen phosphorylase

Biochemistry (10 decks)

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