Usmle Step I: Epidemiology And Biochemistry

Front 1

Case control study measures...? ("What happened?")

Back 1

Odds Ratio (OR)

Front 2

Cohort Study measures...? ("What will happen?")

Back 2

Relative Risk (RR)

Front 3

Cross sectional study measures...? (Observational)

Back 3

Disease prevalance

Front 4

Prevalence =

Back 4

= total cases in a pop at a given time/ total pop at risk

= incidence x dz duration

Front 5

Incidence =

Back 5

new cases in a pop over a given time/ tot pop at risk during that time

Front 6

Sensitivity =

Back 6

= a/ (a+c)

= SNOUT (low false neg rate; rules out dz)

Front 7

Specificity =

Back 7

= d/ (d+b)

= SPIN (low false positive; rules in dz)

Front 8

PPV =

Back 8

= a/(a+b)

= prob of having dz given pos result

Front 9

NPV =

Back 9

= c/ (c+d)

= prob of being dz free given a neg test

Front 10

Odds ratio =

Back 10

= ad/bc

=odds of having dz in exposed group / odds of dz in unexposed group

Front 11

Sensitivity =

Back 11

= a/ (a+c)

= SNOUT (low false neg rate; rules out dz)

Front 12

Specificity =

Back 12

= d/ (d+b)

= SPIN (low false positive; rules in dz)

Front 13

PPV =

Back 13

= a/(a+b)

= prob of having dz given pos result

Front 14

NPV =

Back 14

= c/ (c+d)

= prob of being dz free given a neg test

Front 15

Odds ratio =

Back 15

= ad/bc

=odds of having dz in exposed group / odds of dz in unexposed group

Front 16

Relative risk =

Back 16

= [a/(a+b)] / [c/(c+d)]

= percent with dz in exposed group divided by percent with dz in unexposed group

Front 17

Random error causes...

Back 17

reduced precision in a test

Front 18

Systematic error causes...

Back 18

reduced accuracy

Front 19

The statistical distribution of a positive skew is...

Back 19

Mean > Median > Mode

Asymmetry with tail on right

Front 20

The statistical distribution of a negative skew is...

Back 20

Mean < Median < Mode

Asymmetry with tail on left

Front 21

Null Hypothesis =

Back 21

hypothesis of NO DIFFERENCE

Front 22

Type I error =

Back 22

stating that there is a difference or effect when in fact, there is NO difference

Front 23

Type II error =

Back 23

Stating that there is no difference or effect when there really IS A Difference or effect

Front 24

p < 0.5 means that...

Back 24

there is a < 5% chance that the data will show something that is not really there

Front 25

Power =

Back 25

= (1- beta) = (1 - type II error)

Front 26

To increase power, you can?

Back 26

Increase sample size

Front 27

t-test checks the difference between?

Back 27

the means of 2 groups

Front 28

ANOVA checks the difference between?

Back 28

the means of 3 or more groups

Front 29

Chi squared checks the difference between?

Back 29

2 or more % or proportions of categorical outcomes (NOT mean values)

Front 30

Primary Dz Prevention means...

Back 30

prevent dz occurrence (ex. vaccination)

Front 31

Secondary prevention means...

Back 31

early dz detection (ex. pap smear)

Front 32

Tertiary prevention means...

Back 32

preenting dz progression (insulin for diabetics)

Front 33

Reportable Diseases are:

Back 33

Hep A, B, C; HIV; Salmonella; Shigella; Syphilis; Measles; Mumps; AIDS; Rubella; TB; Chickenpox; Gonorrhea

Front 34

Top 3 causes of death in ages 1-14 year olds:

Back 34

1. Accidents 2. Cancer 3. Cong anomalies

Front 35

Top 3 causes of death in 15-24 year olds:

Back 35

1. Accidents 2. Homicide 3. Suicide

Front 36

Top 3 causes of death in 25-64 year olds:

Back 36

1. Cancer 2. Heart Dz 3. Accidents

Front 37

Top 3 causes of death in 65+:

Back 37

1. Heart dz 2. Cancer 3. Stroke

Front 38

APGAR Scoring

Back 38

Appearance (Blue, peripheral cyanosis, all pink)

Pulse (none, <100, >100)

Grimace (None, grimace, grimace + cough)

Activity (Limp, Some, active)

Respiration (None, Irregular, Regular)

Front 39

Low Birth weight =

Back 39

<2500 g

Front 40

Sleep Stage and EEG Waveform:

Stage I:

Back 40

Beta (high freq, low amp)

Front 41

Sleep Stage and EEG Waveform:

Stage II:

Back 41

Alpha

Front 42

Sleep Stage and EEG Waveform:

Stage 3-4:

Back 42

Deepest sleep: Delta (low freq, high amp)

Front 43

Stage of sleep when sleepwalking, night terrors, and bedwettting occurs:

Back 43

Stage 3-4

Front 44

Sleep Stage and EEG Waveform:

REM:

Back 44

Beta (high freq, low amp)

Front 45

Effect of benzos on stages of sleep:

Back 45

Shorten stage 4 sleep (and useful for night terrors, sleepwalking)

Front 46

Drug of choice to treat bedwetting:

Back 46

Imipramine (shortens stage 4)

Front 47

Principal neurotransmitter involved in REM sleep:

Back 47

ACh

Front 48

Neonate becomes mentally retarded, hyperactive, and has musty odor. Dx?

Back 48

PKU

Front 49

Rapid consumption of alcohol before dinner causes hypoglycemia how?

Back 49

incr. NADH prevents gluconeogenesis by shunting pyruvate and oxaloacetate to lactate and malate

Front 50

Alcoholic develops rash, diarrhea, and altered MS. Vitamin deficiency?

Back 50

Vit B3 (pellagra)

Front 51

urine turns black upon standing. Dx?

Back 51

Alkaptonuria

Front 52

25 year old has chest pain, xanthomas on acchilles. Dx and site of defect?

Back 52

Familial Hypercholesterolemia. --> LDL receptor

Front 53

Dark urine and muscle cramps after exercise. Dx?

Back 53

McArdles Dz

Front 54

Child has weakness and big calves. Dx and inheritance?

Back 54

Duchenne's MD, X-linked recessive

Front 55

Sxs of Deficiency--

Vitamin A:

Back 55

Night blindness, Dry skin

Front 56

Sxs of Deficiency--

Vitamin B1 (Thiamine)

Back 56

Beriberi and Wernicke-Korsakoff syndrome (alcoholism and malnutrition)

Front 57

Dry BeriBeri =

Back 57

polyneuritis, symmetric muscle wasting

Front 58

Wet BeriBeri =

Back 58

high output cardiac failure (dilated cardiomyopathy), edema

Front 59

Sxs of Deficiency--

Vit B2 (Riboflavin)

Back 59

Cheilosis (imflamm of lips) and Corneal vascularization (2 C's)

Front 60

Sxs of Deficiency--

Vit B3 (Niacin)

Back 60

Pellagra (3 D's): Diarrhea, Dermatitis, Dementia and beefy glossitis

Front 61

tryptophan + B6 =

Back 61

Niacin (Vit B3)

Front 62

Sxs of Deficiency--

Vit B5 (pantothenate)

Back 62

dermatitis, enteritis, alopecia, adrenal insufficiency

Front 63

Sxs of Deficiency--

Vit B6 (pyroxidine)

Back 63

Convulsions, hyperirritability, peripheral neuropathy

Front 64

Vit B6 deficiency can be induced by?

Back 64

INH or
Oral Contraceptives

Front 65

Sxs of deficiency of:

Vit B12 (cobalamin)

Back 65

Macrocytic, megaloblastic anemia, neuro sxs (differentiate if from folate def), glossitis

Front 66

Reasons for Vit 12 deficiency:

Back 66

1. Malabsorption
2. Lack of Intrinsic factor (pernicious anemia)
3. Ansence of terminal ileum (Crohn's)

Front 67

which is stored longer:
B12 or folate?

Back 67

B12!

Front 68

Where can you get B12? Folate?

Back 68

B12: Only in animal products;
Folate: green leafy veggies

Front 69

Sxs of Deficiency--

Biotin

Back 69

Dermatitis, enteritis

Front 70

Causes for Biotin deficiency:

Back 70

1. Abx
2. Excessive ingestion of raw eggs

Front 71

Sxs of deficiency:

Vit C (ascorbic Acid)

Back 71

Scurvy (swollen gums, bruising, anemia, poor wound healing)

Front 72

Sxs of deficiency:

Vit D

Back 72

Rickets (kids)--bending bones;
Osteomalacia (adults)--soft bones, hypocalcemic tetany

Front 73

Vit D2 comes from?

Back 73

Milk (ergocalciferol)

Front 74

Vit D3 comes from?

Back 74

sun-exposed skin (cholecalciferol)

Front 75

Fcn of Vit D:

Back 75

Increases intestinal absorption of calcium and phosphate

Front 76

Storage form of Vit D:

Back 76

25-OH D3

Front 77

Active Form of Vit D:

Back 77

1,25 (OH)2 D3

Front 78

Sxs of excess Vit D:

Back 78

Hypercalcemia, loss of appetite, stupor

Front 79

One cause of excess vit D:

Back 79

Sarcoidosis (epithelioid macrophages convert Vit D to active form)

Front 80

Sxs of deficiency:

Vit E:

Back 80

increases frag of erythrocytes, neuerodysfunction

Front 81

Fcn of Vit E:

Back 81

Antioxidant (protects erythrocytes from hemolysis)

Front 82

Sxs of Deficiency:

Vit K

Back 82

neonatal hemorrhage with Incr. PT and PTT, nml bldg time (neonates are given Vit K injection)

Front 83

Vit K dependant clotting factors:

Back 83

II, VII, IX, X, protein C and S

Front 84

Mechanism of action of Warfarin:

Back 84

Vit K antagonist

Front 85

Sxs of deficiency:

Zinc

Back 85

delayed wound healing, hypogonadism, Decreased adult hair

Front 86

Mechanism of action:

Antabuse (Disulfiram)

Back 86

Inhibits acetaldehyde dehydrogenase (acetaldehyde accumulation gives hangover sxs)

Front 87

Purines =

Back 87

A, G (PURe As Gold: PURINES)

Front 88

Pyrimidines =

Back 88

C, T, U (CUT the PY: PYrimidines)

Front 89

Which bond is stronger? G-C or A-T?

Back 89

G-C (3 H bonds)

Front 90

DNA Mutations Definitions--

silent:

Back 90

Same aa

Front 91

DNA Mutations Definitions--

Missense:

Back 91

Changed aa, but new aa is similar in chemical structure to original

Front 92

DNA Mutations Definitions--

Nonsense:

Back 92

Change results in Early STOP codon ("stop the nonsense!)

Front 93

DNA Mutations Definitions--

Frame Shift:

Back 93

change results in misreading of all nucleotides downstream (truncated protein)

Front 94

Put these mutations in order of severity:
silent, missense, nonsense

Back 94

Nonsense > Missense > Silent

Front 95

Site of action of fluouroquinolones:

Back 95

DNA gyrase

(gyrase is specific prokaryoptic topoisomerase)

Front 96

Role of DNA polymerase III:

Back 96

elongates DNA chain by addine deoxynucleotides to the 3' end (leading strand)

Front 97

Progression of enzymes in DNA replication:

Back 97

1. Helicase--> unwinds DNA template at replication fork

2. DNA Topoisomerase--> creates a nick in helix to relieve supercoils

3. Primase--> Makes an RNA primer on which DNA poly III can initiate replication

4. DNA PolIII--> elongates chain

5. Exonuclease--> proofreads each added nucleotide

6. DNA PolI--> degrades RNA primer and fills in gap with DNA

7. Ligase--> Seals

Front 98

Direction of DNA replication:

Back 98

5' --> 3'

Front 99

Mutation in Hereditary nonpolyposis colorectal cancer:

Back 99

Mismatch repair (unmethylated string is recognized, nuc removed and gap refilled)

Front 100

Mutation in xeroderma pigmentosum:

Back 100

Nucleotide excision repair (oligonucleotide with damaged bases is removed)

Front 101

Start codon:

Back 101

AUG (AUG inAUGurates protein synthesis)

Front 102

Stop codons:

Back 102

UGA (U Go Away)
UAA (U Are Away)
UAG (U Are Gone)

Front 103

Function of rough ER (RER):

Back 103

synthesis of secretory (exported) proteins and of N-linked oligosaccharide addition to proteins

Front 104

Function of Nissl bodies:

Back 104

(In neurons) -->synthesize enzymes and peptide neurotransmitters

Front 105

Function of free ribosomes:

Back 105

unattached to membrane--> synthesis of cytosolic and organellar proteins

Front 106

Function of Smooth ER (SER):

Back 106

site of steroid synthesis and detoxification of drugs and poisons

Front 107

What modification in the golgi targets proteins to the lysosome?

Back 107

Mannose-6-phosphate

Front 108

Failure of the addition of mannose-6-phosphate to proteins causes?

Back 108

I-cell disease (enzymes are secreted outside of the cell rather than targeted to the lysosome)

Front 109

5 Drugs that act on microtubules:

Back 109

1. Mebendazole (antihelminthic)
2.Paclitaxel (anti-breast cancer)
3. Griseofulvin (antifungal)
4. Vincristine/vinbalstine (anti-cancer)
5. Colchicine (anti-gout)

Front 110

What is Kartagener's syndrome?

Back 110

Immotile cilia due to defect in dynein (ATPase causes bending of cilia).

Results in male/female fertility, bronchiectasis, recurrent sinusitis.

associated with situs inversus

Front 111

The cytoskeletal element found in: Microvilli

Back 111

Actin and myosin

Front 112

The cytoskeletal element found in: Cilia

Back 112

Microtubule

Front 113

The cytoskeletal element found in: Flagella

Back 113

microtubule

Front 114

Type of collagen found in: Bone

Back 114

Type I

Front 115

Type of collagen found in: Cartilage

Back 115

Type II

Front 116

Type of collagen found in: skin, blood vessels, uterus, granulation tissue

Back 116

Type III (reticulin)

Front 117

Type of collagen found in: Basement membrane

Back 117

Type IV

Front 118

Type of collagen found in: Skin

Back 118

Type I

Front 119

Type of collagen found in: Tendon

Back 119

Type I

Front 120

Type of collagen found in: Nucleus pulposus

Back 120

Type II

Front 121

Site in collagen synthesis which requires Vitamin C, and the dz that results when there is a deficiency:

Back 121

Step II (Hydroxylation of residues in alpha chain or preprocollagen)--> Scurvy

Front 122

Step of collagen synthesis disrupted in osteogenesis imperfecta:

Back 122

Step III, Glycosylation (formatgion of procollagen-->triple helix of alpha chains)

Front 123

Clinical Manifestations of ehlers-danlos and most commonly type of collagen affected:

Back 123

Type III

1. hyperextensible skin
2. easy bruising/bleeding
3. Hypermobile joints
(assoc with berry aneurysms)

Front 124

Disease of blue sclera and multiple fractures with little trauma:

Back 124

OI (osteogenesis imperfecta)

Front 125

Type of collagen typically affected in OI:

Back 125

Type I