Usmle Biochemistry (First Aid)

Front 1

Deficiency of this vitamin leads to night blindness and dry skin-- it is an important constituent of visual pigment:

Back 1

* Vitamin A (Retinol)

Front 2

Deficiency of this vitamin leads to Ber1Ber1 (Beriberi) and Wernicke-Korsakoff syndrome:

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* Vitmain B1 (Thiamine)

Front 3

Deficiency of this vitamin leads to angular stomatitis, Cheilosis, and Corneal vascularization:

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* Vitamin B2 (Riboflavin)

Front 4

Niacin deficiency is also known as:

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* Pellagra (3 D's-- diarrhea, dermatitis, dementia, and beefy glossitis)

Front 5

How is niacin made in the body?

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* From excess Tryptophan

Front 6

2 disorders that can predispose a pt to pellagra:

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* Hartnups disease (tryptophan loss) and Carcinoid syndrome (all tryptophan is used to make seratonin)

Front 7

Tryptophan plus what B-vitamin is need to make niacin?

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* B6 (pyridoxine)

Front 8

Vitamin B5 is a constituent of:

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* CoA

Front 9

Deficiency commonly seen with B6 (pyridoxine deficiency):

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* Convulsions, peripheral neuropathy, sideroblastic anemia

Front 10

Common causes of B6 deficiency:

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* Isoniazid therapy for TB, sometime oral contraceptives

Front 11

Vitamin B12 requires what for absorption in the terminal ileum:

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* Intrinsic factor from parietal cells

Front 12

How do you differentiate a pt deficient in B12 or Folate?

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* B12 deficiency has NEURO sx along with MACRO-cytic/megaloblastic anemia

Front 13

Consuming large amount of raw eggs can lead to deficiency of:

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* Biotin (AVIDin in egg whites, AVIDly binds biotin)

Front 14

A pt with Vitamin C deficiency will get:

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* Scurvey (poor wound healing, swollen gums, bruising, anemia)

Front 15

What is the metabolic function of Vitamin C?

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* Facilitates Iron (Fe2+) absorption by keeping it in a reduced state

Front 16

What test is used to dx a B12 deficiency?

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* Schilling test

Front 17

Vitamin that is used as a cofactor for transaminase reactions (ALT/AST):

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* Vitamin B6

Front 18

Vitamin that is a constituent of NAD+ and NADP+ used in redox reactions:

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* Vitamin B3 (Niacin)

Front 19

Important supplement for synthesis of nitrogenous bases:

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* Folate (deficiency can lead to neural tube defects)

Front 20

Where do you get vitamin D2 and D3 from?

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* D2 (ergocalciferol) from milk

D3 (cholecalciferol) sun-exposed skin

Front 21

What is the active and what is the storage form of vitamin D?

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* Storage = 25-hydroxy-D3

Active = 1,25-hydroxy-D3 (calcitriol)

Front 22

Deficiency of vitamin D leads to what in kids and what in adults?

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* D-deficient kids = Rickets

D-deficient adults = Osteomalacia

Front 23

What is the active form of vitamin D?

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* Calcitriol (1,25 (OH)2 D3)

Front 24

Vitamin E is most important to these cells:

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* Vitamin E is for Erythrocytes

Front 25

What are the vitamin K dependent clot factors:

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* Factors 2, 7, 9, 10, and protein C & S

Warfarin is a vitamin K antagonist

Front 26

What can happen in zinc deficiency?

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* Loss of adult hair (axillary, facial, pubic), delayed wound healing, hypogonadism

Front 27

Limiting reagent in EtOH metabolism:

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* NAD+

Front 28

What does Fomepizole inhibit in EtOH metabolism?

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* Inhibits Alcohol dehydrogenase

Front 29

What does Disulfiram inhibit in alcohol metabolism?

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* Inhibits Acetaldehyde dehydrogenase

Front 30

Why do alcoholics sometime become hypoglycemic?

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* Increase in NADH/NAD+ ratio which inhibits gluconeogenesis in the liver

Front 31

How do you get Kwashiorkor?

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* Lack of protein in the diet-- kids with swollen bellys

MEAL (malnutrition, edema, anemia, liver-fatty)

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How do you get Marasmus?

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* Energy malnutrition-- muscle and tissue wasting occur, loss of subcutaneous fat

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Chromatin that is less condensed and transcriptionally active:

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* Euchromatin (heterochromatin in inactive)

Front 34

Only histone that is not in the nucleosome core:

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* H1 (ties nucleosomes in a string)

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What are the purines and how many rings do they have?

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* A and G (have 2 rings)

Front 36

Which nucleotides bond the strongest because they have 3 H-bonds?

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* G-C (has 3 H-bonds)

(more G-C bonds = higher melting point)

Front 37

What are the pyrimidines and how many rings do they have?

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* C, U, T -- (have 1 ring)

Front 38

What 3 amino acids are required for purine synthesis?

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* GAG (glycine, aspartate, glutamine)

Front 39

Substituting a purine for another purine is:

Substituting a pyrimidine for a purine is:

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* Same (purine for purine) = transition

ConVersion = TransVersion (purine for pyrmidine or vice versa)

Front 40

A DNA mutation that results in a stop codon is:

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* a NONSENSE mutation (stop the nonsense)

Front 41

DNA mutation that results in misreading of all nucleotides downstream-- usually results in a truncated protein:

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* Frameshift

Front 42

3 stop codons are:

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* UGA (u go away), UAA (u are away), UAG (u are gone)

Front 43

Alpha-amanitin is found in the death cap mushroom and inhibits:

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* RNA polymerase II (makes mRNA)

Front 44

Part of DNA that is contains the actual genetic info coding for the protein:

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* Exons (INtrons stay IN the nucleus, whereas EXons EXit and are EXpressed)

Front 45

Where do Rb and p53 suppressor normally inhibit the cell cycle?

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* G1 to S progression

Front 46

Permanent cells such as Neurons, Skeletal/Cardiac muscle, and RBC's remain in what cell cycle phase?

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* G0 phase

Front 47

These two body cells are stable, that is they will enter G1 from G0 when stimulated:

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* Hepatocytes and lymphocytes

Front 48

Labile cells never go to G0 and divide rapidly with a short G1:

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* Bone marrow, gut epithelium, skin, hair follicles

Front 49

Drugs that inhibit microtubules include:

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* Mebendazole (antihelminthic), Paclitaxel (anti-breast cancer), Griseofulvin (antifungal), Vincas (anticancer), and Colchicine (anti-gout)

Front 50

Syndrome characterized by microtubule polymerization defects resulting in decreased phagocytosis:

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* Chediak-Higashi syndrome

Front 51

Syndrome that causes immobile cilia due to a dynein arm defect-- results in infertility, sinusitis, and situs inversus:

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* Kartagener's syndrome

Front 52

Use this stain for connective tissue:

Use this stain for muscle tissue:

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* Vimentin for CT

Desmin for muscle

Front 53

Type I collagen is important for:

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* Bone, skin, tendon, dentin, fascia, cornea, and late wound repair

Osteo Imperfecta-- deficient Type I collagen

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Type II collagen is important for:

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* Cartilage, vitreous body, nucleous pulposus

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Type III collagen is important for:

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* Skin, blood vessels, uterus, fetal tissue, and granulation tissue

Ehlers-Danlos-- deficient type III collagen

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Type IV collagen is important for:

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* Basement membrane

Goodpastures-- deficient type IV collagen

Front 57

What part of collagen synthesis requires vitamin C?

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* Hydroxylation of proline and lysine in the ER

Front 58

Disorder of type III collagen causing hyperextensible skin, easy bruising, hypermobile joints, and associated with Berry aneurysms:

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* Ehlers-Danlos syndrome

Front 59

Elastase is inhibited by:

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* Alpha-antitrypsin

Emphysema can be caused by excess elastase activity

Front 60

These 3 metabolic processes all occur in both the mitochondria and cytoplasm:

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* HUG's take 2 (Heme synthesis, Urea cycle, and Gluconeogenesis)

Front 61

Hexokinase is feedback inhibited by:

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* Glucose-6-phosphate

Front 62

Where is glucokinase found and what does it do?

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* Found in the liver and pancreatic beta cells, it phosphorylates excess glucose to sequester in the liver

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Rate limiting enzyme in glycolysis:

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* Phosphofructokinase-1

Front 64

Most potent activator of phophofructokinase:

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* Fructose 2,6 BP

Front 65

How do RBC's metabolize glucose?

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* Anaerobically via glycoysis

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Rate limiting enzyme of gluconeogenesis:

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* Pyruvate carboxylase

Front 67

Rate limiting enzyme of TCA cycle:

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* Isocitrate dehydrogenase

Front 68

Rate limiting enzyme of Heme synthesis:

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* ALA synthase

Front 69

Rate limiting enzyme of Urea cycle:

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* Carbamoyl phosphate synthase I (CPS I)

Front 70

Rate limiting enzyme of HMP shunt:

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* G6PD (glucose 6 phosphate dehydrogenase)

Front 71

Rate limiting enzyme of ketogenesis:

Rate limiting enzyme of cholesterol synthesis:

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* Keto = HMG-CoA synthase

Cholesterol = HMG-CoA reductase

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G6PD is need for this pathway _____ so that NADPH is produced to keep _____ reduced.

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* needed for HMP shunt so that NADPH can reduce glutathione to detoxify free radicals and peroxides

Front 73

Fructose intolerance is d/t hereditary deficiency of:

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* Aldolase B (must decrease intake of fructose and sucrose)

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Essential fructosuria is d/t a defect in:

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* Fructokinase (fructose appears in blood and urine)

Front 75

Absence of what enzyme causes galactosemia:

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* Absence of galactose-1-phosphate uridyltransferase (AR disorder)

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This disorder of aromatic amino acid metabolism can lead to MR, eczema, fair skin, and a musty body odor:

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* Phenylketonuria (decreased phenylalanine hydroxylase)

Tx: increased TYROSINE in diet

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What are 2 underlying causes of Albinism:

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* Deficient Tyrosinase or defective tyrosine transporters

Front 78

What are the 3 branched amino acids that are blocked in Maple Syrup Urine Disease?

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* Ile, Val, Leu (I Love Vermont Maple Syrup)

Front 79

Disorder that is a purine salvage problem owing to the absence of HGPRT:

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* Lesch-Nyhan syndrome

Front 80

These don't need insulin for glucose uptake:

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* BRICK L (Brain, RBC's, Intestine, Cornea, Kidney, and Liver)

Front 81

A person who has no C-peptide has:

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* DM type I (they have no endogenous insulin)

Endogenous (body) insulin has C-peptide

Front 82

Where are GLUT1 receptors found?

GLUT 2? GLUT 4?

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* GLUT 1 = RBC's and brain

GLUT 2 = B-cells, liver, kidney

GLUT 4 = adipose tissue, skeletal muscle

Front 83

The 2 essential fatty acids:

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* Linoleic and Linolenic acids

(Eicosanoids are dependent on fatty acids)

Front 84

What are the function of the following lipoproteins: B100, CII, B-48, A1

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* A1 = Activates LCAT
B100 = Binds LDL receptor, mediates VLDL secretion
CII = Cofactor for lipoprotein lipase
B48 = Mediates chylomicron secretion

Front 85

What is the deficiency in familial hypercholesterolemia?

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* Decreased LDL receptors

Front 86

Disorder of glucose-6-phosphate where there is severe fasting hypoglycemia, high LACTATE, and hepatomegaly:

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* Von Gierkes disease (Type I Glycogen storage disease)

Front 87

Disorder of Lysosomal alpha-1,4-glucosidase with cardiomegaly and systemic findings leading to death:

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* Pompe's disease (Type II glycogen storage disease)

Pompes trashes the pumps (heart, liver, muscle)

Front 88

Disorder of debranching enzyme alpha 1,6 glucosidase where gluconeogenesis is intact and blood lactate levels are normal:

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* Cori's disease (Type III glycogen storage disease)

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Disorder of skeletal muscle glycogen phosphorylase where increased glycogen in muscle leads to painful muscle cramps and myoglobinuria with exercise:

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* McArdle's disease (Type V glycogen storage disease)

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Pneumonic for remembering the 4 main glycogen storage diseases:

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* Very Poor Carb Metabolism

Von Gierkes I -- low sugar, high lactate
Pompe's II -- trashes the pump
Cori's III -- normal lactate
McArdles V -- muscle pain/myoglobinuria

Front 91

2 XR lysosomal storage diseases from first aid:

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* Fabry's and Hunters

Front 92

Kid with MR, gargoylism, airway obstruction, course features, and CORNEAL CLOUDING think:

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* Hurlers syndrome (accumulation of Heparan and Dermatan Sulfate)

Hurler's is AR, Hunter's is XR

Front 93

What is the deficient enzyme in a MR kid with course features and corneal clouding:

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* Alpha-L-IDURONIDASE (Hurler's)

Front 94

A kids with a mild MR, aggressive behavior, and NO corneal clouding think:

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* Hunter's syndrome (accumulation of Heparan and Dermatan Sulfate)

Hunter aim for the X-- it is XR

Front 95

What are the deficient enzymes seen in Hunter's and Hurlers syndrome (both are accumulation of dermatan and heparan sulfate):

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* Hurlers = alpha-L-Iduronidase

Hunters = Iduronidate SULFATE

Front 96

Way to remember differences between Hurlers and Hunters:

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* Hurlers need AI (alpha Iduronidase) and are serious and CLOUDY (corneas)

Hunters IS (Iduronidate sulfate) good at aiming for the X (XR inheritance)

Front 97

Kid with hepatosplenomegaly, ASEPTIC NECROSIS OF THE FEMUR, bone crisis, think:

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* Gauchers-- deficient Beta-glucocerebrosidease leading to accumulation of glucocerebroside

This is AR inheritance and is the most common lysosomal storage disease

Front 98

Kid with hepatosplenomegaly, neurodegeration, FOAM CELLS + CHERRY-RED SPOT on macula think:

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* Niemann-Pick disease (deficient sphingomyelinase leading to accumulation of sphingomyelin)

NP is an AR inheritance

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Kid with neurodegeneration, developmental delay, and ONION SKIN LYSOSOMES + CHERRY-RED SPOT think:

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* Tay-Sachs (deficient hexosaminidase A leading to accumulation of GM2 ganglioside)

TS is AR inheritance

Front 100

Kid with peripheral neuropathy, developmental delay, OPTIC ATROPHY, and globoid cells think:

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* Krabbe's disease (deficient galactocerebrosidase leading to accumulation of galactocerebroside)

Krabbes is AR inheritance

Front 101

A kid with central and peripheral demyelination with dementia and ataxia think:

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* Metachromatic leukodystrophy (arylsulfatase A deficiency leading to accumulation of cerbroside sulfate)

ML is an AR inheritance

Front 102

A kid with peripheral neuropahty or hands/feet, ANGIOKERATOMAS, and cardio/renal disease think:

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* Fabry's disease (alpha-galactosidase A deficiency leading to an accumulation of ceramide trihexoside)

Fabry's is XR inheritance, like Hunters disease

Front 103

This chemical is the most potent regulator of the rate-limiting step of glycolysis:

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* Fructose 2,6 BP

(activates PFK-1)

Front 104

These 2 compounds are inhibitors of the rate limiting step of glycolysis:

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* Citrate and ATP (although F 2,6 BP can override their inhibition)

Rate-limit of glycolysis = PFK-1

Front 105

How does insulin affect glycolysis and how?

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* Insulin activates F2,6 BP thus activating PFK-1 (the rate limiting step in glycoysis)-- this all occurs in the FED state

Front 106

In an ischemic heart during a heart attack, what compound will be elevated in the cardiac cells?

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* PFK-1 -- Rate limiter of glycolysis

Anaerobic state predominates