Ppal99 Dissecting Usmle Step 1,2,3 4Th Edition Enzymes

Front 1

what are enzymes?

Back 1

>>Lower the Free Energy of Activation
>>Bring substrates together in space and time
>>Stabilize high energy intermediate
>> Is never consumed in the reaction

Front 2

which of the enzymes is the slowest one?

Back 2

Allosteric enzyme =the slowest one

Front 3

Efficacy

Back 3

max effect regardless if dose lower w/ non-competitive antagonist)

Front 4

Potency

Back 4

amount of drug needed to produce effect Over w / comp antagonist)

Front 5

Kd

Back 5

[D] that binds 50% of receptors

Front 6

EC50

Back 6

[D] that produces 50% of maximal response

Front 7

Competitive Inhibition: what happens to potency, Km, Vmax, ir/reversibility. MOA

Back 7

potency decreases, ⇧Km
fights for active site, reversible, no change in Vmax

Front 8

Non-competitive Inhibition: what happens to potency, Km, Vmax, ir/reversibility. MOA

Back 8

Non-competitive Inhibition: binds a regulatory site, no change in Km irreversible, efficacy decreases. Thus, Km affects potency and V max affects efficacy

Front 9

what does -ΔG mean?

Back 9

-G = ΔH -TΔS
-ΔG = drives reaction forward

Front 10

what does ΔH mean

Back 10

enthalpy (heat)

Front 11

what are the two types of enthalphy

Back 11

Endothermic
Exothermic

Front 12

silverdiazine (for burn victims) creates what kind of reaction?

Back 12

endothermic reaction

Front 13

Endothermic

Back 13

endergonic ⇨ add heat

Front 14

Exothermic

Back 14

exergonic ⇨ gives off heat => spontaneous, favorable.

Front 15

what does +AS mean?

Back 15

entropy (randomness)
High energy/randomness to low energy/randomness

Front 16

teperature: what is it proportional too?

Back 16

T proportional to V max

Front 17

what happens to Vmax when temp is too high and why?

Back 17

• If T increases too much => proteins denature therefore Vmax will drop

Front 18

what is the most common cause of death?

Back 18

heart failure

Front 19

+AE

Back 19

redox potential

Front 20

-.AE

Back 20

= > has too many electrons

Front 21

If it is being oxidized what kind of agent it is?

Back 21

=> reducing agent
Note: "OIL RIG": Oxidized Is Losing-electrons, Reduced Is Gaining electron

Front 22

function of complex I

Back 22

NADH feeds in electrons

Front 23

function of complex II

Back 23

FADH2 feeds in electrons

Front 24

function of complex III

Back 24

requires iron for heme

Front 25

function Complex IV

Back 25

Oxidation portion, Cytochrome oxidase (oxygen used to form water and requires iron for heme and copper)

Front 26

function of Complex V:

Back 26

Phorphorylation portion (forms of ATP)

Front 27

function of Coenzyme Q

Back 27

Shunts electrons to Complex III (AE gets progressively positive as it passes through the ETC)

Front 28

what is the ETC inhibitor of Complex I:

Back 28

Amytal, Rotenone

Front 29

what is the ETC inhibitor of Complex II

Back 29

Malonate

Front 30

what is the ETC inhibitor of Complex III:

Back 30

Antimycin D

Front 31

what are the ETC inhibitors of Complex IV

Back 31

CN, CO, Chloramphenicol ⇦ Cu/Fe "4C's affects complex 4"

Front 32

what are the ETC inhibitors of Complex V?

Back 32

Oligomycin

Front 33

NADH gives you how many ATP?

Back 33

3 ATP

Front 34

FADH2 give how many ATP?

Back 34

2 ATP (already passed complex I, only have 2 more places to do it)

Front 35

which complex has the electrons driven towards it?

Back 35

Complex IV "cytochrome oxidase"- has the most +ΔE => e- are driven toward it

Front 36

what are the 3 things that ETC needs to function?

Back 36

Need O2, Cu, and Fe=> low E state without 'em

Front 37

what are the retic levels in Aplastic Crisis

Back 37

low retics

Front 38

what are the retic levels in Sequestration Crisis:

Back 38

high retics
(RBCs trapped in big spleen)

Front 39

what are uncopulers and name the 3 examples

Back 39

can't make ATP now
• BNP: insecticide
• asa (Ex: Reye's syndrome)
• Free fatty acids

Front 40

MOA of CO poisoning and Tx.
How would a patient manifest?

Back 40

CO = Competitive inhibitor of O2 on Hb => normal O2 sat, low pO2 (Tx: O2)
•Cherry-red lips, pinkish skin

Front 41

MOA of CN poisoning

Back 41

Non-competitive inhibitor of O2 on Hb => nml O2 sat, nml p02

Front 42

Dx: Almond breath

Back 42

CN poisoning

Front 43

drugs that can cause CN poisoning (4)

Back 43

Drug induced Sulfas, Antimalarials, Metronidazole, Nitroprusside

Front 44

treatment for CN poisoning and explain why each step is done

Back 44

Tx: ''A Tortured Man Breathes"
1. Amyl Nitrite- converts Hb to MetHb => CN can't act
2. Thiosulfate- binds CN =>pee out thiocyanate
3. Methylene-blue - converts Fe3+ to Fe2+
4. Blood transfusion

Front 45

what is the etiology of MetHb (Fe3+)

Back 45

=> low O2 sat, normal p02 (can't bind O2)

Front 46

Nephrotoxicity

Back 46

water-soluble (charged)

Front 47

Hepatotoxicity

Back 47

fat-soluble (bioavailable)

Front 48

what fuels our bodies during these times:
2-4 hrs:
24 hrs:
48 hrs:
>48 hrs:

Back 48

2-4 hrs: Glucose
24 hrs: Glycogen
48 hrs: Protein ⇦Muscle
>48 hrs: Fat

Front 49

lsomerase

Back 49

creates an isomer (Ex: glucose => fructose)

Front 50

Epimerase

Back 50

creates an epimer, differs around 1 chiral carbon (glucose ⇨ galactose)

Front 51

Mutase

Back 51

moves sidechain from one carbon to another (intrachain)

Front 52

Transferase

Back 52

moves sidechain from one substrate to another (interchain)

Front 53

Kinase

Back 53

phosphorylates using ATP (-P makes it stay inside cell)

Front 54

Phosphorylase

Back 54

phosphorylates using Pi

Front 55

Carboxylase

Back 55

forms C-C (w/ ATP and biotin)

Front 56

Synthetase

Back 56

two substrates are consumed, uses ATP

Front 57

Synthase

Back 57

two substrates are consumed (name after product)

Front 58

Phosphatase

Back 58

breaks phosphate bond

Front 59

Hydrolase

Back 59

break a bond (w/ H20)

Front 60

Lyase

Back 60

cut C-C bonds (w/ATP)

Front 61

Dehydrogenase

Back 61

removes H (w/cofactor)

Front 62

Thio

Back 62

break S bond

Front 63

Rate Limiting Enzyme Glycolysis:

Back 63

PFK-1

Front 64

Rate Limiting Enzyme Gluconeogenesis:

Back 64

Pyruvate carboxylase

Front 65

Rate Limiting Enzyme HMP shunt:

Back 65

G-6PD

Front 66

Rate Limiting Enzyme Glycogenesis:

Back 66

Glycogen synthase

Front 67

Rate Limiting Enzyme Glycogenolysis:

Back 67

Glycogen phosphorylase

Front 68

Rate Limiting Enzyme FA synthesis:

Back 68

AcCoA carboxylase

Front 69

Rate Limiting Enzyme β-oxidation:

Back 69

CAT 1

Front 70

Rate Limiting Enzyme Cholesterol synthesis:

Back 70

HMG CoA reductase

Front 71

rate limiting enzymes: Ketogenesis:

Back 71

HMGCoA synthase

Front 72

rate limiting enzymes: Purine synthesis:

Back 72

PRPP synthase

Front 73

rate limiting enzymes: TCA cycle:

Back 73

Isocitrate dehydrogenase

Front 74

rate limiting enzymes: Urea cycle:

Back 74

CPS-I

Front 75

rate limiting enzymes: Heme synthesis:

Back 75

δ-ALA synthase

Front 76

rate limiting enzymes: Pyrimidine synthesis:

Back 76

Asp transcarbarnoylase (also uses CPS II)

Front 77

rate limiting enzymes TCA cycle:

Back 77

Isocitrate dehydrogenase

Front 78

rate limiting enzymes: Urea cycle:

Back 78

CPS-I

Front 79

rate limiting enzymes: Heme synthesis:

Back 79

δ-ALA synthase