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MCAT > Biochem 5, 11 > Flashcards

Biochem 5, 11 Flashcards

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MCAT flashcards
1
Q

lipids are insoluble in

A

water

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2
Q

lipids are soluble in

A

nonpolar organic solvents

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3
Q

phospholipids

A

ampthipathic

form bilayer of biological membranes

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4
Q

saturation of fatty acid tails determines

A

the fluidity of the membrane

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5
Q

phospholipids structure

A

hydrophilic (polar) head - attached by phosphodiester linkage, determines function of phospholipid (bc interacts with environment)

hydrophobic (nonpolar) tail

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6
Q

saturated fatty acids vs unsaturated fatty acids fluidity

A

saturated less fluid thatn unsaturated

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7
Q

glycerophospholipids

A

phospholipids that contain glycerol backbone

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8
Q

sphingolipids

A

contain a sphingosine or sphingoid backbone

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9
Q

sphingophospholipids

A

sphingolipids that contain a phosphodiester bond

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10
Q

sphingomyelins

A

type of sphingophospholipids

contain a phosphatidylcholine or phosphatidylethanolamine head group

major component of myelin sheath

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11
Q

glycosphingolipids

A

attached to sugar moieties instead of a phosphate group

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12
Q

cerebrosides

A

type of glycosphingolipid

have one sugar connected to sphingosine

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13
Q

globosides

A

type of glycosphingolipid

have two or more sugars connected to sphingosine

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14
Q

gangliosides

A

contain oligosaccharides with at least one terminal N-acetylneuraminic acid (NANA/sialic acid)

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15
Q

waxes

A

contain long fatty acids esterified to long chain alcohols

used as protection against evaporation and parasites in plants and animals

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16
Q

glycerol

A

3 carbon alcohol

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17
Q

saturated fatty acids

A

have no double bonds between carbons

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18
Q

unsaturated fatty acid

A

one or more double bonds between carbons

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19
Q

terpenes

A

odiferous steroid percursors made from isoprene

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20
Q

isoprene

A

5 carbon molecule

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21
Q

one terpene unit (monoprene) contains

A

two isprene units

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22
Q

steroid structure

A

3 cyclohexane rings + 1 cyclopentane ring

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23
Q

steroid hormones

A

have high affinity receptors

work at low concentrations

affect gene expression and metabolism

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24
Q

cholesterol

A

steroid important to membrane fluidity and stability

precursor to many other molecules

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25
Q

prostaglandins

A

autocrine and paracrine signaling molecules that regulate cAMP levels

have powerful effects on smooth muscle contraction, body temp, sleep wake cycle, fever, and pain

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26
Q

fat soluble vitamins include

A

ADEK

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27
Q

vitamin A

A

aka cerotene

metabolized to retinal for vision and retinoic acid for gene expression in epithelial development

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28
Q

vitamin D

A

aka cholecalciferol

metabolized to calcitriol in kidneys

regulates calcium and phosphorus homeostasis in intestines (inc calcium and phosphate absorption)

promotes bone formation

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29
Q

rickets

A

deficiency in vitamin D

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30
Q

vitamin E

A

aka tocopherols

biological antioxidants

aromatic rings destroy free radicals, preventing oxidative damage

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31
Q

vitamin K

A

aka phylloquinone and menaquinones

important for formation of prothrombin, a clotting factor

performs posttranslational modifications on many proteins, creating calcium binding sites

32
Q

triaclyglycerols

A

preferred method of storing energy for long term use

carbon atoms in lipids are more reduced than carbs, giving twice as much energy per gram during oxidation

very hydrophobic - not hydrated by body water and do not carry additional water weight

33
Q

triaclyglycerol structure

A

one glycerol attached to 3 fatty acids by ester bonds

the fatty acids usually vary within the same triacylglycerol

34
Q

adipocytes

A

storage of large triaclyglycerol deposits for animals

35
Q

free fatty acids

A

unesterified fatty acids that travel in bloodstream

36
Q

soaps

A

salts of free fatty acids

act as surfactants, forming micelles

37
Q

saponification

A

ester hydrolysis of tricycglycerols using a strong base, like sodium or potassium hydroxide

38
Q

micelle

A

dissolves lipid soluble molecules in its fatty acid core, and washes away with water because of its shell of carboxylate head groups

39
Q

surfactant

A

lowers surface tension at the surface of a liquid, serving as a detergent or emulsifier

40
Q

chemical digestion of lipids occurs in

A

small intestine

41
Q

chemical digestion of lipids is faciltated by

A

bile, pancreatic lipase, colipase, and cholesterol esterase

42
Q

digested lipids may form ____ for…

A

micelles for absorption or be absorbed directly

43
Q

short-chain fatty acids are absorbed…

A

across intestine into blood

44
Q

long chain ftty acids are absorbed as ___ and…

A

micelles and assembled into chylomicrons for release into lymphatic system

45
Q

how are lipids mobilized?

A
  • from adipocytes: by hormone sensitive lipase (HSL)
  • from lipoproteins: by lipoprotein lipase (LPL)
46
Q

lipoprotein lipase (LPL)

A

necessary for metabolism of chylomicrons and VLDL

47
Q

chylomicrons

A

transport mechanism for dietary triacyclerol molecules

transported via lymphatic system

48
Q

VLDL

A

transports newly synthesized triacylglycerol molecules from liver to peripheral tissues in bloodstream

49
Q

IDL

A

aka VLDL remnant

in transition between triacylglycerol and cholesterol transport

picks up cholesteryl esters from HDL

50
Q

LDL

A

transports cholesterol for use by tissues

51
Q

HDL

A

reverse transport of cholesterol

52
Q

apoproteins

A

control interactions between lipoproteins

53
Q

cholesterol may be obtained through

A

dietary sources or de novo synthesis in liver

54
Q

key enzyme in cholesterol biosynthesis

A

HMG-CoA reductase

55
Q

fatty acids are synthesized in the ___ from __

A

cytoplasm from acetyl-CoA transported out of the mitochondria

56
Q

fatty acid synthesis steps

A

activation, bond formation, reduction, dehydration, second reduction

repeated 8 times to form palmitic acid

57
Q

palmitic acid

A

the only fatty acid that humans can synthesize

58
Q

fatty acid oxidation occurs in ___ following ___

A

mitochondria following transport by the carnitine shuttle

59
Q

beta oxidation

A

uses cycles of oxidation, hydration, oxidation, and cleavage

60
Q

fatty acid oxidation

branched and unsaturated fatty acids

A

require special enzymes

unsaturated fatty acids use an isomerase and additional reductase during cleavage

61
Q

ketogenesis

A

formation of ketone bodies

62
Q

ketone bodies form during

A

prolonged starvation state due to excess acetyl-CoA in the liver

63
Q

ketolysis

A

regenerates acetyl-CoA for use as an energy source in peripheral tissues

64
Q

protein digestion occurs primarily in

A

small intestine

65
Q

catabolism of cellular proteins occurs

A

only under conditions of starvation

66
Q

protein catabolism

A

carbon skeletons of amino acids used for energy, either through gluconeogenesis or ketone body formation

amino groups are fed into urea cycle for excretion

fate of a side chain depends on its chemistry

67
Q

urea cycle

A

occurs in liver

body’s primary way of removing excess nitrogen from the body

68
Q

Which of the following statements about fatty acid synthesis is correct?

(A) Fatty acids can be used to synthesize glucose.
(B) Fatty acids can be synthesized from glucose.
(C) Fatty acids can be broken down to generate NADPH
(D) Fatty acids are important in nucleotide synthesis.

A

(B) Fatty acids can be synthesized from glucose.

Excess glucose (from dietary carbohydrates) can be converted into acetyl-CoA, which can be used to build up fatty acids.

Because the PDH reaction is irreversible, fatty acids cannot be converted back into glucose.

69
Q

In the liver, fatty acids synthesized from glucose can be packaged with the chylomicron remnants to form:

(A) HDLs
(B) Chylomicrons
(C) VLDLs
(D) Albumin

A

(C) VLDLs

In the liver, fatty acids synthesized from glucose can be packaged with the chylomicron remnants to form very low density lipoproteins (VLDLs).

70
Q

Where in the cell does fatty acid synthesis occur?

(A) Mitochondrial intermembrane space
(B) Mitochondrial Matrix
(C) Inner membrane of the mitochondria
(D) Cytoplasm

A

(D) Cytoplasm

Fatty acid synthesis occurs in the cytoplasm.

71
Q

Triacylglyceride molecules can be broken down into glycerol and fatty acids. Glycerol can be broken down for use as energy via ______________ and fatty acid chains can be broken down for use as energy via ______________.

(A) glycolysis, beta-oxidation
(B) beta-oxidation, glycolysis
(C) pentose phosphate pathway, glycogenolysis
(D) glycogenolysis, pentose phosphate pathway

A

(A) glycolysis, beta-oxidation

Triacylglyceride molecules can be broken down into glycerol and fatty acids. Glycerol can be broken down for use as energy via glycolysis and fatty acid chains can be broken down for use as energy via beta-oxidation.

72
Q

Compare beta-oxidation and fatty acid synthesis?

A

They are almost the same exact pathway except that they are going in opposite directions. The goal of beta-oxidation is to break fatty acids down into two-carbon acetyl-CoA molecules while the goal of fatty acid synthesis is to combine acetyl-CoA molecules together in the formation of a long-chain fatty acid.

73
Q

Let’s Review – Where does each of the following metabolic pathways take place in the cell?

(1) Glycolysis
(2) Gluconeogenesis
(3) The Linking Step
(4) The Kreb’s Cycle
(5) The Electron Transport Chain
(6) Fatty Acid Synthesis
(7) Beta-oxidation

A

(1) Glycolysis - Cytoplasm
(2) Gluconeogenesis - Liver
(3) The Linking Step - Mitochondrial Matrix
(4) The Kreb’s Cycle - Mitochondrial Matrix
(5) The Electron Transport Chain - Inner Mitochondrial Membrane
(6) Fatty Acid Synthesis - Cytoplasm
(7) Beta-oxidation - Mitochondrial Matrix

74
Q

CRB True or false? NADH and FADH2 produced from the breakdown of fatty acids must be shuttled before they can be used in the Electron Transport Chain.

A

False. Because Beta-Oxidation mainly occurs in the mitochondria, the NADH and FADH2 can easily be used by the Electron Transport Chain without relying on shuttles.

75
Q

Amino acids can be used to make which of the following?

I. Protein
II. Glucose
III. Fatty Acids

(A) I Only
(B) I and II Only
(C) I and III Only
(D) I, II, and III

A

(D) I, II, and III

Amino acids can be used to make protein, glucose, or fatty acids.

MCAT (26 decks)

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