Biochem Ii Exam 2

Front 1

N2 + 3H2 --> 2NH3

Energy cost?

Back 1

∆G is -33kJ/mol, but huge activation energy (K is 1 at 100˚C

Haber-Bosh makes with 400ºC and 200atm

Requires 16ATP in diazotrophs

Front 2

Ammonia

Back 2

pKa of 9 so most is NH4+ in cell

Front 3

Reducing activation energy of nitrogen fixation

Back 3

ATP reduces E˚' of dinitrogenase reductase so ∆E is positive.

ATP hydrolysis increases entropy

ATP incr enthalpy when binds to reductase

∆G = ∆H - T∆S = -Fn∆E

Front 4

How to kill ALL cancer cells

Back 4

give them aspariginase, which converts Asn back to Asp, usingup all their asparigine

*They don't make a Asn

Front 5

Methotrexene

Back 5

similar to THF and inhibitor of DHFR

-1000x increase in Km over THF

Front 6

Digestion of proteins in stomach

Back 6

Gastric cells make HCl (pH 1-2.5 in stomach) - denatures proteins and kills pahtogens
Chief cells make pepsinogen (a xymogen that autocatalytically cleaves to pepsin at low pH)

Front 7

Sketch parietal cell

Back 7

notes

Front 8

Pepsin

Back 8

An aspartyl protease

-Selective for large aromatic amino acids
-max activity at pH2, denatures 8+
-2 Asp catalytic residues
-noncovalent mech

Front 9

Proteases classes

Back 9

1)Serine
2)Cysteine
3)Aspartyl
4)Metalloprotease

First two are covalent mechs

Front 10

Small intestine protein digestion

Back 10

Secretin hormone causes pancreas to release bicarbonate (pH to 7)

CCK hormone causes release of more proteases

Front 11

CCK causes release of?

Back 11

1)Trypsinogen
2)Chymotrypsinogen
3)Procarboxypeptidase A and B
4)Proelastase

Front 12

Trypsin

Back 12

a serine protease

cleaves at arg and lys

Front 13

Entropeptidase

Back 13

Cleaves xymogens of trypsinogen to trypsin, which then cleaves xymogens of carboxypeptidase, chymotrypsin, and elastase

Front 14

Chymotrypsin

Back 14

Leu, Met, Tyr, Phe, Trp

Serine protease

Front 15

Elastase

Back 15

Ser, Gly, Ala

Serine protease

Front 16

Carboxypeptidase

Back 16

Cleave a C terminus

A: Aromatic and aliphatic aa's
B: + charged aa

Front 17

Aminopeptidases

Back 17

Membrase associated on gut epithelia

-cleave from N terminus, especially di and tripeptides that are about to enter cells

Front 18

Transport of aa into gut cells

Back 18

Free aa with ATPase active transport
Di and tripeptides co-transported with H+

Front 19

Catabolism of AA in liver

Back 19

1) Amine group passed to Glu

aa + alpha-KG ---> alpha-keto acid + Glu

alpha keto acids = ketogenic, glucogenic, or both

Front 20

Glucogenics

Back 20

alpha keto acid to pyr or OAA for CAC or gluconeogensis

Front 21

Ketogenic

Back 21

Carbon converted to Acyl-CoA

Front 22

Steps of chymotrypsin (exemplar serine protease)

p208

Back 22

1) Ser stabilized by His-Asp attacks carbonyl
2) O- stabalized in oxyanion hole with Gly and Ser backbone; amide bond attacks H on His and 1/2 leaves
3)Water donates H to His and its HO- attack carbonyl carbon
4)Oxyanion again stabilized; bond to Ser attacks H of His and other half leaves

Front 23

Where do the atoms in urea come from?

Back 23

One NH2 from NH4+

One NH2 from Asp (from a Glu in CAC)

C from bicarbonate

O from water

Front 24

Energy cost of urea cycle

Back 24

Net +2ATP

Glutamate dehydrogenase makes NAD(P)H
Malate Dehydrogenase makes NADH
t4, 5 ATP

Use 3 (One to make argininosuccinate, and two to make carbamoyl phosphate)

Front 25

Location of urea cycle steps

Back 25

Cytosol: pre-1, 3,4,5, OAA -> Asp
Matrix: pre-2, 1, 2 and relevant TCA

Need transporters into matrix for Glu, ornithine, bicarbonate

Need transporters out for citrulline, OAA

Front 26

Breakdown of urea

Back 26

by urease in bacteria

Front 27

Non-dietary protein breakdown determinants?

Back 27

1)N-term aa identity (position 2)
2)PEST sequences
3)Ubiquination