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NPLEX - Biochemistry > Lipids > Flashcards

Lipids Flashcards

1
Q

When the liver has enough ATP, what does it do with the build-up of acetyl CoA?

A

it forms polymers of acetyl-CoA (fatty acids)

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2
Q

Are ketone bodies produced in a fed state or in a fasting state?

A

fasting

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3
Q

Name two key functions of thromboxanes.

A

coagulation, vasoconstriction

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4
Q

Bile acids (cholic acid and chenodeoxycholic acid) are synthesized in the liver from?

A

cholesterol

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5
Q

How many carbons are in linoleic acid? How many double bonds?

A

18:2

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6
Q

T/F: VLDL delivers hepatic triglycerides to peripheral tissues.

A

T

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7
Q

Where in the cell does beta-oxidation occur?

A

mitochondrial matrix

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8
Q

What is the biological significance of cardiolipin?

A

It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain

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9
Q

Which enzyme converts arachidonic acid to leukotrienes?

A

lipoxygenase

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10
Q

What type of bond is formed between each fatty acid and the glycerol molecule in a triglyceride?

A

ester bonds

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11
Q

Where does the first double bond in linolenic acid occur?

A

third carbon from the methyl terminus

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12
Q

Type IIa hypercholesterolemia has increased levels of ___

A

LDL

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13
Q

Generally, when fatty acids are oxidized inside the mitochondria, how many carbons are removed per reaction?

A

two carbons

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14
Q

Lipoprotein functions: Which cells secrete chylomicrons?

A

intestinal epithelial cells

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15
Q

ApoE is located on all lipoproteins except ___.

A

LDL

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16
Q

Before leaving the liver, bile acids are conjugated in amide linkage to ___.

A

glycine (glycocholic acid) or taurine (taurochenodeoxycholic acid)

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17
Q

In fatty acid synthesis, which Kreb intermediate is translocated form the mitochondria to the cytosol to produce acetyl-CoA?

A

citrate

citrate is cleaved by citrate lyase to produce cytosolic acetyl-CoA and OAA

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18
Q

Does secretin get activated by low or high pH of intestinal contents?

A

low pH (chyme entering the intestine is acidic)

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19
Q

How many double bonds are in palmitic acid?

A

16:0

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20
Q

25-hydroxycholecalciferol is transported to the ___ of the kidneys where it can be hydroxylated by one of two enzymes to different forms of vitamin D.

A

proximal tubules

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21
Q

Where is lipoprotein lipase synthesized? What would a deficiency cause?

A

adipocytes and muscle cells

familial lipoprotein lipase deficiency (type I hyperlipoproteinemia) results in extremely high chylomicronemia

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22
Q

Name three cofactors required for the hydroxylation of vitamin D by 25-hydroxylase.

A

NADPH, O2, MG2+

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23
Q

Which shunt is the major supplier of NADPH for fatty acid synthesis?

A

hexose monophosphate shunt (pentose phosphate pathway)

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24
Q

Does insulin phosphorylate or dephosphorylate hormone sensitive lipase?

A

hormone sensitive lipase is dephosphorylated and becomes inactive

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25
Is arachidonic acid a saturated or unsaturated fatty acid?
unsaturated (20:4)
26
Are triglycerides readily absorbed in the duodenum?
no
27
Does insulin activate or deactivate HMG-CoA reductase?
activate
28
List the six steps of cholesterol synthesis starting from acetyl-CoA.
acetyl-CoA to mevalonic acid to isoprene to squalene to lanosterol to cholesterol
29
HDL is screted from which two places?
liver, intestine
30
Where in the cell does steroid synthesis occur?
cytoplasm
31
apoA-1 and apoA-II are proteins located on?
HDL
32
Is stearic acid an unsaturated or saturated fatty acid?
saturated (found in many foods including red meat and peanuts)
33
Fatty acids are synthesized in the ___ of the cell.
cytosol
34
HDL - What is the major molecule it transports?
reverse cholesterol transport (from tissues to liver)
35
Fatty acid synthesis occurs in the ___ and beta oxidation occurs in the ___.
cytoplasm mitochondria
36
Fatty acid entry into cytosol is via the ___.
citrate shuttle
37
What is the pathophysiology of type IIa hypercholesterolemia?
decreased number of LDL receptors
38
Name the five main functions of prostaglandins.
inflammation, pain, fever, tissue repair, clotting
39
What is the role of PIP2?
hormonal signal transmission via activated phospholipase C formation of inositol-3-P (IP3) and diacylglycerol (DAG), followed by mobilization of Ca2+ and activation of protein kinase C
40
What are two situations where ketone bodies are found in urine?
prolonged starvation, diabetic ketoacidosis
41
T/F: short and medium chain length FAs require micelles for absorption by the intestinal mucosa
F
42
Type III dysbetalipoproteinemia has altered apolipoprotein ___, and increased ___ and ___.
E, IDL, VLDL
43
Corticosteroids (cortisol) inhibit which enzyme involved in prostaglandin synthesis?
phospholipase A2
44
Do trans fats ever occur naturally in nature, or are they always synthesized?
trans fats do occur naturally
45
Cholesterol synthesis: 2/3 of plasma cholesterol is esterified by ___.
lecithin-cholesterol acyltransferase (LCAT)
46
What is the main function of apolipoprotein E?
mediates remnant (extra) uptake
47
Thromboxane A2 is made from ___ and thromboxane A3 is made from ___.
TXA2 from arachidonic acid (AA) and TXA3 from eicosapentaenoic acid (EPA).
48
What is the main function of apolipoprotein B-48?
mediates chylomicron secretion
49
Name the five steps of fatty acid synthesis.
carboxylation, condensation, reduction, dehydration, reduction
50
Lipoprotein lipase is involved in the storage of triacylglycerol. Name the enzyme that initiates mobilization of stored fat and removes a fatty acid from carbon 1 or 3 of the triacylglycerol.
hormone sensitive lipase
51
Chylomicrons are released by exocytosis from intestinal mucosa and enter the blood via which vein located near the heart?
left subclavian vein
52
Apolipoprotein B-100 binds to ___ receptors.
LDL
53
HMG-CoA reductase catalyzes the rate-limiting step in cholesterol synthesis and inhibits the formation of?
mevalonic acid from HMG-CoA
54
Type IIb combined hyperlipidemia has increased levels of ___ and ___.
LDL, VLDL
55
Cholecalciferol is formed in the skin when UV light acts upon ___.
7-dehydrocholesterol
56
LDL is taken up by target cells via what process?
receptor-mediated endocytosis
57
Does EPI turn on or off the cAMP cascade leading to triacylglycerol degradation?
turned on (FA synthesis turned off)
58
VLDL - What is the major molecule it transports?
delivers hepatic TG to tissues
59
Which enzyme releases free fatty acids from triglycerides?
lipase
60
LDL delivers hepatic cholesterol to ___.
peripheral tissues
61
Type IV hypertriglyceridemia is caused by hepatic overproduction of ___.
VLDL
62
Name the three products of the beta-oxidation of a fatty acid.
FADH2, NADH, acetyl-CoA
63
What two factors influence the melting temperature of a fatty acid?
increasing chain length increasing melting temp addition of double bounds decreases the melting temp
64
What is the predominant fatty acid in olive oil? How many double bonds are in this fatty acid?
oleic acid 18:1 (omega-9)
65
If removal of the chylomicron remnant is defective, what condition results? Which apo protein is defective?
familial type II hyperlipoproteinemia (aka dysbealipoproteinemia) apoE
66
Which enzyme converts arachidonic acid into prostaglandins?
cyclooxygenase
67
The simplest glycerophospholipid is ___.
phosphatidic acid
68
Which lipoproteins contain apoC-II?
chylomicrons, VLDL, HDL
69
What is the rate-limiting step of cholesterol synthesis?
HMG-CoA reductase
70
The side chains of bile salts contain which two amino acids?
glycine, taurine
71
Fatty acids are degraded in the ___ of the cell.
mitochondria
72
Which organ makes ketone bodies but cannot use them?
liver
73
T/F: type V mixed hypertriglyceridemia has only increased VLDL.
F increased VLDL and chylomicrons
74
In fatty acid synthesis, acetyl-CoA via carboxylation forms ___.
malonyl-CoA
75
Apolipoprotein C-II is a cofactor for which enzyme?
lipoprotein lipase
76
How does a drug that lowers bile acids lower cholesterol?
when bile is removed, replacement bile must be synthesized from cholesterol, which lowers cholesterol
77
Which phospholipid does not have a glycerol backbone and is abundant in neurons?
sphingomyelin
78
HDL mediates transport of cholesterol from where to where?
periphery to liver (reverse cholesterol transport)
79
Chylomicrons deliver dietary ___ to ___ and dietary ___ to ___.
triglycerides to peripheral tissues cholesterol to liver
80
Is the tail of a phospholipid hydrophilic or hydrophobic?
hydrophobic
81
Cholecalciferol is hydroxylated in the liver to ___ by the enzyme ___.
25-hydroxycholecalciferol 25-hydroxylase
82
Vitamin D is hydroxylated first in the ___ and then in the ___.
liver kidney
83
Fatty acid entry into mitochondria is via ___, which is inhibited by ___.
carnitine shuttle cytoplasmic malonyl-CoA
84
Of the 15-30g of bile salts secreted per day, ___ grams are lost in feces.
0.5
85
Is the head of a phospholipid hydrophobic or hydrophilic?
hydrophilic
86
Arrange the following in order of size (largest to smallest): LDL, IDL, HDL, VLDL, Chylomicron
Chylomicron, VLDL, IDL, LDL, HDL
87
Apolipoprotein A-I activates ___.
activates LCAT
88
In which part of the small intestine does the process of emulsification of dietary lipids begin?
duodenum
89
LDL - What is the major molecule it transports?
delivers hepatic cholesterol to tissues
90
Would high levels of malonyl-CoA increase or decrease the levels of acylcarnitine transferase I?
decrease malonyl-CoA inhibits acylcarnitine transferase I
91
Name the enzyme found in the mucosa of the jejunum and lower duodenum that causes gallbladder contractions in response to dietary lipids?
CCK - cholecystokinin
92
Is oleic acid a mono- or polyunsaturated fatty acid?
mono
93
Describe the composition of a triglyceride.
triglycerides are formed from a single molecule of glycerol, combined with three fatty acids on each of the OH groups
94
Define the term amphipathic.
contains both hydrophobic and hydrophilic regions (ex: phospholipid)
95
The enzyme 1-alpha-hydroxylase is activated by ___ to form the main biologically active vitamin D.
PTH
96
Congenital abetalipoproteinemia occurs when triacylglycerols accumulate in the intestinal mucosa. Name the apo protein that is deficient.
Apo B-48
97
Fatty acids are made by a multienzyme complex called ___.
fatty acid synthase
98
In fatty acid synthesis, what is the enzyme that catalyzes the reaction of acetyl-CoA to malonyl-CoA?
acetyl-CoA carboxylase (biotin enzyme)
99
Where is VLDL secreted from?
liver
100
How many carbons are linolenic acid? How many double bonds?
18:3
101
Excess lipids in the feces is termed ___.
steatorrhea
102
What is the active carrier of choline?
CDP-choline
103
Where does the digestion of lipids begin?
stomach
104
Ketone bodies are metabolized by the brain to two molecules of ___.
acetyl-CoA
105
Where is the cell acetyl-CoA generated?
cytosol
106
The hormonally active form of vitamin D is also known as ___.
calcitriol
107
Chylomicron - where is it secreted and what two main dietary substances does it transport?
delivers dietary TG to peripheral tissue and dietary cholesterol to liver secreted by intestinal epithelium
108
Name the four major families of eicosanoids.
leukotrienes (LTA), thromboxanes (TXA), prostacyclins (PGI), prostaglandins (PGE)

NPLEX - Biochemistry (8 decks)

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