Usmle Step 1 Biochemistry

Front 1

Fat Soluble Vitamins

Back 1

Vit A = vision
Vit D = Bone calc, Ca2+ homeostasis
Vit E = Antioxidant
Vit K = Clotting factor

Front 2

Water Soluble Vitamins

Back 2

B1 (thiamine: Tpp)
B2 (riboflavine: FAD, FMN)
B3 (niacin: NAD+)
B5 (pantothenic acid:CoA)
B6 (pyridoxine: PLP)
B12 (cobalamin)
C (ascorbic acid)
Biotin
Folate

Front 3

Vit A (retinol)

*Found in liver and leafy veggies

Back 3

Function: Antioxidant; constituent of visual pigments (retinal); essential for normal diff of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting)

Deficiency: Night blindness, dry skin
Excess: Arthralgias, fatigue, headache, skin change, sore throat alopecia. TERATOGENIC (cleft palate, cardiac)--> preggers test done before isotretinoin prescribed for severe acne

Front 4

Vit B1 (thiamine)

*Seen in malnutrition and alcoholism

Back 4

Fnxn: In thiamine pyrophosphate (TPP), cofactor for several enzymes:
(1) pyruvate dehydrogenase (glycolysis)
(2) alpha-ketoglutarate dehydrog (TCA cycle)
(3) Transketolase (HMP shunt)
(4) Branched-chain AA dehydro

Deficiency: impaired glucose breakdown --> ATP depletion; highly aerobic tissues affected 1st.
WERNICKE-KORSAKOFF SYN and BERIBERI (dry: polyneuritis, sym muscle wasting, wet: cardiac failure, edema)

Front 5

Vit B2 (riboflavin)

Back 5

Function: Cofactor in oxidation/reduction (eg FADH2)

Deficiency:
**Cheilosis (inflamm of lips, scaling, fissures at mouth corners) **Corneal vascularization

Front 6

Vit B3 (niacin)

**Synthesis requires Vit B6

Back 6

Fnxn: Constituent of NAD+, NADP+ (used in redox, B3 = 3 ATP); derived from tryptophan.

Deficiency:
Glossitis. Severe deficiency leads to PELLAGRA, which can be caused by HARTNUP DZ (decreased tryptophan asbsorp), malignant carcinoid syndrome (increas. tryptophan metabolism), and INH (decreased vit B6)

Pellagra: 3D's = diarrhea, dermatitis, dementia.
excess untx'd corn in diet --> pellagra (vit b3 in corn not absorable, unless tx'd)

Excess: Facial flushing (from pharm doses for tx of hyperlipidemia)

Front 7

Vit B5 (pantothenate)

Back 7

Function:
Essential component of CoA (a cofactor for acyl transfers) and fatty acid synthase

Deficiency: dermatitis, enteritis, alopecia, adrenal insufficiency

Pantothen-A is in Co-A

Front 8

Vit B6 (pyridoxine)

Back 8

Fnxn:
(1) converted to pyridoxal phosphate, cofactor used in transamination (eg ALT and AST)
(2) decarboxylation rxns
(3) glycogen phosphorylase
(4) cystathionine synthesis
(5) heme synthesis
(6) required to synth NIACIN (vit B3) from tryptophan

Deficiency: convulsions, hyperirritability, peripheral neuropathy (deficiency inducible by INH and OCP, sideroblastic anemia

Front 9

Vit B12 (cobalamin)

**Found in animal products.
**Synthesized only by microorganisms
**Very large reserve pool stored in liver

Back 9

Fnxn: Cofactor for homocysteine methyltransferase (transfers CH3 groups as methylcobalamin) & methylmalonyl-CoA mutase

Deficiency:
macrocytic, megaloblastic anemia, hypersegmented PMNs, neurologic sxs (paresthesias, subacute combined degeneration) due to ABNORMAL MYELIN
Prolonged deficiency --> irreversible nervous system damage

*Deficiency usually due to malabsorption (sprue, enteritis, Diphyll), lack of intrinsic factor (pernicious anemia, gastric bypass surgery) or absence of terminal ileum (Crohns dz)

*Use of Schilling test to detect etiology of deficiency

Front 10

Folic Acid


**Most common vitamin deficiency in USA
**Deficiency seen in pregnancy (take supp to avoid neural tube defect) & alcoholism

Back 10

Fnxn: Converted to tetrahydrofolate (THF), a coenzyme for 1-carbon transfer/methylation rxns
Impt for synthesis of nitrogenous bases in DNA and RNA.

Deficiency: macrocytic, megaloblstic anemia;
NO neurologic sxs (unlike B12)

Deficiency can be caused by several drugs (phenytoin, sulfanomides, MTX)

*Folate from FoLiage
*Small reserve pool in liver

Front 11

S-Adenosyl-methionine

*Required for the conversion of NE --> epinephrine

Back 11

ATP + methionine --> SAM
SAM transfers methyl units
(SAM is the methyl donor man)

Regeneration of methionine (and SAM) is dependent on Vit B12 & folate

Front 12

Biotin (B7)

"AVID in egg whites"

Back 12

Fnxn:
Cofactor for carboxylation enzymes (which add 1-carbon group):
(1) pyruvate carboxylase: Pyruvate (3C) --> oxaloacetate (4C)
(2) acetyl-CoA carboxylaseL Acetyl-CoA (3C) --> malonyl-CoA (4C)
(3) Propionyl-CoA carboxylase: Propionyl-CoA (3C) --> methylmalonyl-CoA (4C)

Deficiency: relatively rare. Dermatitis, alopecia, enteritis. Caused by antibiotic use or excessive ingestion of raw eggs.

Front 13

Vit C (ascorbic acid)


**Found in fruits/veggies
**British sailors carried limes to prevent scurvy

Back 13

Fnxn: ANTIOXIDANT
(1) Facilitates iron absorption by keeping iron in Fe2+ reduced state (more absorbable)
(2) Necessary for hydroxylation of proline & lysine in collagen synthesis
(3) necessary for dopamine beta-hydroxylase, which converts dopamine --> NE

Deficiency: SCURVY=swollen gums, bruising, anemia, poor wound healing

Front 14

Vit D

**drinking milk (fortified w/vitD) is good for the bones
**Calcitrol is active form

Back 14

D2= ergocalciferol -- ingested from plants, used as pharmacologic agent
D3=cholecalciferol --consumed in milk, formed in sun-exposed skin
25-OH D3 = storage form
1, 25-(OH)2D3 (calcitrol) = ACTIVE

Fnxn: INCREASE intestinal absorption of Ca2+ and phosphate, INCREASE bon resorption

Deficiency: RICKETS in children (bending bones), OSTEOMALACIA in adults, hypocalcemic tetany

Excess: Hypercalcemia, hypercalciuria, loss of appetite, stupor. Seen in sarcoidosis (INCR activation of vit D by epithelioid macrophages)

Front 15

Vit E


**E is for erythrocyte!

Back 15

Fnxn: Antioxidant (protects erythrocytes and membranes from free-radical damage)

Deficiency: INCR fragility of erythrocytes (hemolytic anemia), muscle weakness, neurodysfnxn

Front 16

Vit K

**K for Koagulation
*Synthesized by intestinal flora

Back 16

Fnxn: Catalyzes GAMMA-carboxylation of glutamic acid residues on various proteins concerned with blood clotting.
- necessary for synthesis of clotting factors 2, 7, 9, 10, and protein C and S

**Warfarin = Vit K antagonist

Deficiency: Neonatal hemorrhage w/INCR PT and aPTT, but normal bleeding time (neonates have sterile intestines and unable to synth vit K)
Def can also occur after prolonged use of broad-spectrum antibiotics

*neonates given vit K injection at birth to prevent hemorrhage

Front 17

Zinc


**deficiency may predispose to alcoholic cirrhosis

Back 17

Fnxn: Essential for the activity of 100+ enzymes. Impt in formation of zinc fingers (transcription factor motif).

Deficiency: Delayed wound healin, hypogonadism, DECRS adult hair (axillary, facial, pubic), dysgeusia (distortion of taste), anosmia (inability to perceive odors).

Front 18

Drugs that act on MICROTUBULES

Back 18

1) Mebendazole/thiabendazole (antihelminthic)
2) Griseofulvin (antifungal)
3) Vincristine/vinblastine (anti-cancer)
4) Paclitaxel (anti-breast cancer)
5) Colchicin (anti-gout)

Front 19

Immunohistochemical Stains:

1) Connective Tissue
2) Muscle
3) Epithelial Cells
4) Neuroglia
5) Neurons

Back 19

1) Vimentin
2) Desmin
3) Cytokeratin
4) GFAP
5) Neurofilaments

Front 20

Cardiac glycosides

Digoxin and Digitoxin

Back 20

Uses: Atrial fib, atrial flutter, sometimes CHF

How works:
Directly inhibit Na+/K+ ATPase, which leads to INDIRECT inhibition of Na+/Ca2+ exchange. INCR [Ca2+]i --> INCR cardiac contractility

Front 21

Collagen

Be (So Totally) Cool, Read Books.

Back 21

**Most abundant protein in human body.
**Organizes and strengthens extracellular matrix

4 types Collagen:
Type 1: Bones, Skin, Tendons
Type 2: Cartilage
Type 3: Reticulin
Type 4: Basement membrane

Front 22

Collagen Type I

Back 22

90% of collagen types:

1) BONE
2) Skin
3) tedon
4) dentin
5) fascia
6) cornea
7) late wound repair

Front 23

Collagen Type II

"carTWOlage"

Back 23

1) Cartilage (including hyaline)
2) Vitreous body
3) Nucleus pulposus

Front 24

Collagen Type III

Back 24

RETICULIN
1) skin
2) blood vessels
3) uterus
4) fetal tissue
5) granulation tissue

Front 25

Collagen Type IV

Type IV: under the FLOOR

Back 25

Basement membrane or basal lamina

Front 26

Blotting Procedures

1) Southern blot
2) Northern blot
3) Western blot

Back 26

SNoW = DRoP
Southern = DNA
Northern = RNA
Western = protein

Southern = DNA electro w radioactive DNA probe
Northern = RNA electro w radioactive DNA probe
Western = Protein w antibody probe

Front 27

ELISA

(Enzyme-linked immunosorbent assay

Back 27

Rapid immunologic technique testing for ANTIGEN-ANTIBODY reactivity

* Test antigen = see if immune system recognizes it

* Test antibody = see if antigen recognizes it

Front 28

Fluorescence in situ hybridization (FISH)

Back 28

Fluorescent DNA or RNA probe binds to specific gene site of interest

USE: Specific localization of genes and direct visualization of anomalies (microdeletions) at molecular level

Fluorescence = gene is present
No Fluorescence = gene has been deleted

Front 29

Cloning

Back 29

Production of recombinant DNA molecule that is self-perpetuating

1) DNA fragment inserted into bacterial plasmid containing antibiotic resistance genes
2) Restriction enzymes cleave DNA at 4-to- 6-pb sequences, allowing insertion of fragment into plasmid
3) Tissue mRNA isolated and exposed to reverse transcriptase, forming cDNA library (lacks intron)

Front 30

Sanger DNA sequencing

Back 30

Dideoxynucleotides halt DNA polymerization at each base, generating sequence of various lengths that encompass entire original sequence.

Terminated fragments electrophoresed and original sequence deduced

Front 31

Karyotyping

Back 31

Metaphase chromosomes stained, ordered, numbered according to morphology, size, arm-length ratio and banding pattern.

Tissues used: blood, bone marrow, amniotic fluid, placental tissue

Used to dx chromosomal imbalance

Front 32

Model systems

Knock out = remove gene
Knock in = insert gene

Back 32

Transgenic strategies in mice:
1) Constitutive: RANDOM insertion of gene into mouse genome
2) Conditional: TARGETED insertion/deletion of gene thru homologous recomb w/mouse gene

RNAi--dsRNA synthesized that is complementary to mRNA sequence of interest. When transfected into human cells, dsRNA separates/promotes degradation of target mRNA, knocking down gene expression

Front 33

Hardy-Wineberg Population Genetics

1) no mutation at locus
2) no selection for any genotypes at locus
3) completely random mating
4) no migration

Back 33

Disease prevalence
p^2 + 2pq + q^2 = 1

Allele prevalence
p+q= 1

Heterozygote prevalence: 2pq

Prevalence of X-linked recessive dz in males = q, in females = q^2

Front 34

Imprinting

ex. Prader-Willi - deletion of normally active Paternal allele

AngelMan's - deletion of normally active Maternal allele

Back 34

At a single locus, only 1allele is active, the other is inactive (imprinted/inactivated by methylation).

Deletion of active allele --> disease

Difference in phenotype depends on whether mutation is of maternal or paternal origin.

Front 35

Kinase

Back 35

Uses ATP to add HIGH-ENERGY phosphate group onto substrate

(ex phosphofructokinase)

Front 36

Phosphorylase

Back 36

Adds INORGANIC phosphate onto substrate without using ATP

(ex glycogen phosphorylase)

Front 37

Phosphatase

Back 37

REMOVES phosphate group from substrate

(eg fructose-1,6-biphosphatase)

Front 38

Dehydrogenase

Back 38

OXIDIZES substrate

(eg pyruvate dehydrogenase)

Front 39

Carboxylase

Back 39

ADDS 1 carbon with the help of biotin

(eg pyruvate carboxylase)

Front 40

Metabolism sites in Mitochondria

Back 40

1) Fatty acid oxidation (beta-oxidation)
2) acetyl-CoA production
3) TCA cycle
4) oxidative phosphorylation

Front 41

Metabolism sites in Cytoplasm

Back 41

1) Fatty acid synthesis
2) Glycolysis
3) HMP shunt
4) protein synthesis (RER)
5) Steroid synthesis (SER)

Front 42

Metabolism sites in cytoplasm & mitochondria

Back 42

1) Heme synthesis
2) Urea cycle
3) Gluconeogenesis

Front 43

Rate determining enzyme of metabolic process:

Glycolysis

Back 43

phosphofructokinase-1 (PFK-1)

Front 44

Rate determining enzyme of metabolic process:

Gluconeogenesis

Back 44

Fructose-1,6-bisphosphatase

Front 45

Rate determining enzyme of metabolic process:

TCA cycle

Back 45

Isocitrate dehydrogenase (oxidizes substrate)

Front 46

Rate determining enzyme of metabolic process:

Glycogen synthesis

Back 46

Glycogen synthase

Front 47

Rate determining enzyme of metabolic process:

Glycogenolysis

Back 47

Glycogen phosphorylase

(adds inorganic phosphate w/o ATP)

Front 48

Rate determining enzyme of metabolic process:

HMP shunt

Back 48

glucose-6-phosphate dehydrogenase (G6PD)

(oxidizes substrate)

Front 49

Rate determining enzyme of metabolic process:

De novo pyrimidine synthesis

Back 49

Carbomyl phosphate synthetase II

Front 50

Rate determining enzyme of metabolic process:

De novo purine synthesis

Back 50

Glutamine-PRPP amidotransferase

Front 51

Rate determining enzyme of metabolic process:

Urea cycle

Back 51

Carbamoyl phosphate synthetase I

Front 52

Rate determining enzyme of metabolic process:

Fatty acid synthesis

Back 52

actetyl-CoA carboxylase (ACC)

Front 53

Rate determining enzyme of metabolic process:

Fatty acid oxidation

Back 53

Carnitine acyltransferase I

Front 54

Rate determining enzyme of metabolic process:

Ketogenesis

Back 54

HMG-CoA synthase

Front 55

Rate determining enzyme of metabolic process:

Cholesterol synthesis

Back 55

HMG-CoA reductase

Front 56

Signaling pathways of endocrine hormones

cAMP

Back 56

"FLAT CHAMP"

FSH
LH
ACTH
TSH
CRH
hCG
ADH (V2 receptor)
MSH
PTH
Calcitonin
Glucagon

Front 57

Signaling pathways of endocrine hormones

cGMP

Back 57

ANP
NO (EDRF)

think vasodilators

Front 58

Signaling pathways of endocrine hormones

IP3

Back 58

"GGOAT"

GRH
GnRH
Oxytocin
ADH (V1 receptor)
TRH

Front 59

Signaling pathways of endocrine hormones

steroid receptor

Back 59

Glucocorticoid
Estrogen
Progesterone
Testosterone
Aldosterone
Vit D
T3/T4

Front 60

Signaling pathways of endocrine hormones

Tyrosine Kinase

Back 60

F-PPIIG

FGF
PDGF
Prolactin
Insulin
IGF-1
GH

Front 61

Signaling pathways of endocrine hormones

cAMP

Back 61

"FLAT CHAMP"

FSH
LH
ACTH
TSH
CRH
hCG
ADH (V2 receptor)
MSH
PTH
Calcitonin
Glucagon

Front 62

Signaling pathways of endocrine hormones

cGMP

Back 62

ANP
NO (EDRF)

think vasodilators

Front 63

Signaling pathways of endocrine hormones

IP3

Back 63

"GGOAT"

GRH
GnRH
Oxytocin
ADH (V1 receptor)
TRH

Front 64

Signaling pathways of endocrine hormones

steroid receptor

Back 64

Glucocorticoid
Estrogen
Progesterone
Testosterone
Aldosterone
Vit D
T3/T4

Front 65

Signaling pathways of endocrine hormones

Tyrosine Kinase

Back 65

F-PPIIG

FGF
PDGF
Prolactin
Insulin
IGF-1
GH

Front 66

Essential Amino Acids

(need to be supplied by diet)
The Ten Acid Pornstars Liked Very Hot Ladies In Mini-skirts

Back 66

Glucogenic: Met, Val, Arg, His

Ketogenic: Leu, Lycine

Both: Ile, Phe, Thr, Trp

Front 67

Acidic Amino Acids

Back 67

Asp and Glu

Front 68

Basic Amino Acids

Back 68

Arg, Lys, and His