Biochem+

Question 1

Rate-limiting enzymes of major pathways

Answer 1

Mnemonic: “PAHOF”

PFK-1 (Glycolysis)

Acetyl-CoA carboxylase (Fatty Acids synthesis)

HMG-CoA reductase (Cholesterol synthesis)

Ornitine transcarbamylase (Urea cycle)

Fructose-1,6-bisphosphatase (Gluconeogenesis)

PFK-1: phosphofructokinase-1

Question 2

ATP production per glucose

Answer 2

Aerobic = 32 ATP (malate shuttle), 30 ATP (glycerol-3P shuttle); Anaerobic = 2 ATP

Question 3

Glycolysis location

Answer 3

Cytoplasm of all cells.

Question 4

TCA cycle location

Answer 4

Mitochondria

Question 5

Electron transport chain

Answer 5

Inhibited by cyanide, CO, rotenone

Question 6

Gluconeogenesis

Answer 6

Occurs in liver, not muscles (no G6Pase in muscle)

Question 7

Glycogen storage diseases

Answer 7

“Very Poor Carbohydrate Metabolism”

Von Gierke (G6Pase def.)

Pompe (acid maltase)

Cori (debranching enzyme)

McArdle (muscle phosphorylase)

Question 8

Fatty acid synthesis vs oxidation

Answer 8

Synthesis = cytoplasm (“S = Synthesis = Cytoplasm”)
Oxidation = mitochondria

Question 9

Urea cycle

Answer 9

Mnemonic: “Ordinarily, Careless Crappers Are Also Frivolous About Urination”

Ornithine, Carbamoyl phosphate, Citrulline, Aspartate, Arginosuccinate, Fumarate, Arg, Urea

Question 10

Maple Syrup Urine Disease (MSUD)

Answer 10

Defect in branched-chain α-ketoacid dehydrogenase → can’t degrade Isoleucine, Leucine, Valine.

Question 11

DNA polymerase I vs III

Answer 11

Pol III = replication, Pol I = removes RNA primers (5’→3’ exonuclease)

Question 12

Nucleotide excision repair (Pyrimidines)

Answer 12

Defective in Xeroderma Pigmentosum.

Question 13

Base excision repair

Answer 13

Fixes spontaneous deamination

Question 14

Mismatch repair

Answer 14

Defective in Lynch syndrome (HNPCC)

Question 15

Non-homologous end joining

Answer 15

Defective in Ataxia Telangiectasia

Question 16

Silent vs missense vs nonsense mutations

Answer 16

Nonsense = Stop the nonsense (early STOP codon)

Question 17

Codon usage

Answer 17

Start = AUG (codes Met), Stop = UGA, UAG, UAA (“U Go Away”, “U Are Gone”, “U Are Annoying”)

Question 18

mRNA processing

Answer 18

Cap (5’), Tail (3’), Splice (in between)

Question 19

tRNA structure

Answer 19

CCA at 3’ end = “Can Carry Amino acids

Question 20

Collagen synthesis

Answer 20

nemonic: “Inside, Outside”

Inside: hydroxylation (vitamin C), glycosylation.

Outside: cleavage, cross-linking (requires Cu²⁺).

Question 21

Ehlers-Danlos Syndrome

Answer 21

Defect in collagen cross-linking

Question 22

Osteogenesis Imperfecta

Answer 22

Defect in type I collagen → blue sclera, fracture

Question 23

Marfan Syndrome

Answer 23

Fibrillin-1 defect

Question 24

Menke’s disease

Answer 24

Impaired copper transport → kinky hair, hypotonia.

Question 25

Elastin degradation

Answer 25

Inhibited by α1-antitrypsin → deficiency leads to emphysema

Question 26

PCR

Answer 26

Denature, anneal, extend

Question 27

Southern, Northern, Western blots

Answer 27

Mnemonic: “SNoW DRoP” Southern = DNA, Northern = RNA, Western = Protein.

Question 28

Microarrays

Answer 28

Detect gene expression differences across thousands of genes

Question 29

Gene expression regulation

Answer 29

Transcription factors bind promoter/enhancer elements

Question 30

Thiamine B1

Answer 30

Deficiency = Wernicke-Korsakoff, Beriberi

Question 31

Niacin B3

Answer 31

Deficiency = Pellagra (3 D’s: Diarrhea, Dermatitis, Dementia)

Question 32

Pyridoxine B6

Answer 32

Deficiency = neuropathy (esp. with INH

Question 33

Cobalamin B12

Answer 33

Deficiency = megaloblastic anemia + neuro symptoms

Question 34

Ascorbic acid vit C

Answer 34

Required for collagen hydroxylation → deficiency = scurvy

Question 35

Retinoic acid vit A

Answer 35

Deficiency = night blindness; excess = teratogen

Question 36

Vit K

Answer 36

Needed for clotting factor γ-carboxylation.

Question 37

Folate B9

Answer 37

Deficiency = megaloblastic anemia without neuro symptoms

Question 38

Zinc deficiency

Answer 38

Delayed wound healing, hypogonadism, acrodermatitis enteropathica

Question 39

Biotin B7

Answer 39

Deficiency = alopecia, dermatitis (from raw eggs – avidin)