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MCAT Qs missed > Bio / Biochem 1 > Flashcards

Bio / Biochem 1 Flashcards

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MCAT flashcards
1
Q

Lipoic enzyme

A

coenzyme in PDC
-deficiency causes lactic acid production

(same with thiamine / vitamin b1)

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2
Q

Heart contraction

A

SA node = atria contracts
SA node to AV node to Bundle of His to Bundle branches to Purkinje fibers = ventricles contract

SA node = impulse initiation = automatically send 60-100 signals per min

atrial contraction = atrial kick = 5-30% CO

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3
Q

Gap junctions

A
  • rapid exchange of ions / cell communication b/w adjacent cells
  • do NOT do cell adhesion

=connexon

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4
Q

Tight junctions

A

-prevent solutes from leaking out of cells into IF or space b/w cells or into cells w/in the same layer through intracellular shunt (prevent paracellular transport)
vs transcellular
-do NOT connect epithelium / epidermis to dermis
-link cells within a layer only, no anchoring other structures

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5
Q

Desmosomes

A
  • cell-cell adhesion by anchoring to cytoskeleton

- not b/w layers

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6
Q

Hemidesmosomes

A

-attach epithelial cells to underlying structures such as basement membrane or dermis

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7
Q

Kcat

A

turnover number of enzyme
-max # substrate converted to product per unit time
unit same as freq (s^-1)
Usually 102 s^-1

ES -> E + P (kcat over arrow)

Vmax = Kcat*[E]
Efficiency = Kcat/Km
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8
Q

At high [S]….

A

-rate of E binding to S does not limit rxn rate
-Kcat limits rxn rate— Kcat determines Vmax
Vmax = Kcat*[E]

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9
Q

Variable expressivity

A

Same genotype, dif phenotypes

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10
Q

Codominance

A

Blood groups

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11
Q

HDL

A

increase cholesterol in tissue

  • cholesterol recovery from blood
  • cholesterol to tissues like liver
  • cholesterol synthesis is powered by ATP and NADPH
  • RLS of cholesterol synth is HMG CoA reductase
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12
Q

statins

A
  • lower cholesterol

- so does glucagon

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13
Q

Complaince

A

Veins are more compliant than arteries b/c they have thinner walls / less smooth muscle

Elasticity is when, once stretched, you can contract; it’s the reciprocal of compliance

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14
Q

Myelin

A

-decreases capacitance (storage of opposite charges) by insulating axon = block accumulation of opposite charges at axonal membrane

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15
Q

Brown fat in babies

A
  • less efficient ETC
  • babies can’t shiver
  • they have a higher SA/volume ratio
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16
Q

Brain

A
  • neurons
  • use GLUCOSE not fat
  • fats can’t cross BBB easily
  • B-oxidation requires way more oxygen = risk hypoxia in brain
17
Q

Triacylglycerols are packaged in

A

VLDL’s

very low density lipoproteins

18
Q

Cardiac myocytes prefer

A

fats

Skeletal- glucose

19
Q

Following a meal, FA synthesized in…

A

liver

  • convert to TAG
  • package in VLDL’s

chylomicrons carry TAG’s absorbed from gut

20
Q

In fasting state

A
  • decrease insulin (don’t wanna decrease blood sugar)

- increase epinephrine (increase blood sugar and release fat from adipocytes)

21
Q

Sickle cells

A
  • more rigid membrane
  • swell less in hypotonic solution
  • HbS agglutinates only in low oxygen
22
Q

Mouth enzymes

A
  • salivary amylase = ptaylin- carbs into maltose and dextrins
  • lipase
23
Q

Detection bias

A

-concluding correlation/causation when there’s none

24
Q

Selection bias

A

-non-representative sample

25
Q

External validity

A

-ability to generalize results to population

26
Q

Internal validity

A

-look for correlation vs causation by CONTROLLING FOR CONFOUNDING VARIABLES

27
Q

Retroviruses

A
  • need reverse transcriptase
  • make DNA from ssRNA
  • enveloped
28
Q

Positive sense

A
  • ssRNA

- directly translated into protein; it’s basically mRNA

29
Q

Neg sense

A
  • need complementary RNA to use for protein synth

- MUST HAVE RNA replicase

30
Q

Ketogenesis

A

-in liver mitochondria
-Acetyl CoA accumulates in prolonged fasting
-HMG-CoA synthase: acetyl CoA + acetoacetyl CoA = HMG CoA
-HMG-CoA lyase: acetoacetate + acetyl CoA
-acetoacetate itself breaks down into CO2 and acetone
-too much acetone = ketoacidosis
-NADH can reduce acetoacetate into 3-hydroxybutyrate
-acetoacetate and 3-hydroxybutyrate (ketone bodies)
can go into blood and into tissues for energy
-acetyl CoA and thiophorase are in the blood

  • There, ketolysis happens (renal cortex and skeletal muscle)
  • 3-hydroxybutyrate + NAD+ to reform acetoacetate
  • Thiophorase (not in liver) adds the CoA -> turned back into acetyl CoA

If fast > 1 week, concentration of ketone bodies is high enough in blood for brain to metabolize it too

In brain, glucose is used
in prolonged fasting, inhibit pyruvate dehydrogenase, favor ketolysis (so you don’t break down brain proteins for glycolysis) = activate thiophorase

31
Q

Duodenum

A

Brush border enzymes- Small intestine
Bile, cholesterol esterase (most cholesterol is not from diet), pancreatic lipase / colipase- hydrolyze TAG into free fatty acids and 2-monoacylglycerol
Emulsify -> form micelles
chylomicrons- packages into lymph- contains apolipoproteins, fat-soluble vitamins- dumped into circulatory via THORACIC DUCT which drains into the LEFT SUBCLAVIAN VEIN

Chylomicrons are absorbed by LACTEALS- lymph vessels- low pressure (veins at lowest pressure)- so pressure gradient from lymph to thoracic duct
-short fatty acids do diffuse directly into bloodstream

32
Q

Protein metabolism

A

Pepsin- made by chief cells
-acidic env (other enzymes- basic env of duodenum)
Brush border enzymes- dipeptidase, aminopeptidase

Broken down proteins cross luminal membrane via 2ndary active transport involving Na

Proteins lose amino group via transamination/deamination- enter urea cycle- enter nephron via PCT and DCT

Glucogenic aa’s- all but L and K
Ketogenic- L, K, FITTT

33
Q

Biological metabolism

A
  • open system- exchange energy and matter
  • most bichem expts are in a closed system
  • closed system- only energy
  • isolated = nada

deltaU = Q - W
internal E of system = heat into system - work done by system
phase changes are isothermal
W = -P deltaV, which doesn’t change in biological systems

deltaH = Q at constant pressure

G = Gstd + RT lnQ
Q = pdts/reac
STP = 25 degrees C

Modified std state- neutral pH rather than 1M of H+ ions = deltaGstd prime

we use ATP to minimize amount of waste = -30.5 kJ/mol

34
Q

Pyruvate oxidation

A

C3H4O3 + NADH -> C3H6O3 + NAD+

CH3-CO-COOH —–> CH3-CHOH-COOH

MCAT Qs missed (19 decks)

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