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Year 1: 08. CPR Exam 1 > Lecture 26: Lipids and Lipoproteins > Flashcards

Lecture 26: Lipids and Lipoproteins Flashcards

1
Q

What are some sources of Acetyl CoA?

A

Pyruvate
Fatty Acids
Amino Acids

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2
Q

How many units of IPP form a sterane ring?

A

6 units

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3
Q

Describe the structure of cholesterol.

A

Sterane Ring
Hydrocarbon Ring
Hydroxyl group
27 carbons total

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4
Q

Where is cholesterol utilized?

A

Bile acids and salts
Vitamin D
Steroid Hormones

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5
Q

What enzyme breaks down cholesterol?

A

None! Instead it is excreted or used biochemically

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6
Q

How does Acetyl CoA become IPP?

A

Acetyl CoA –> Acetoacetyl CoA –> HMG CoA –> Mevalonate –> IPP

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7
Q

What is the rate limiting step when Acetyl CoA become IPP?

A

HMG CoA Reductase

HMG CoA –> Mevalonate

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8
Q

What can inhibit HMG CoA Reductase?

A

Statins

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9
Q

What can be the fate for IPP?

A

Steroids
Lipid Soluble Vitamins
Other: Ubiquinone, Lipid Anchors

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10
Q

How does IPP become cholesterol?

A

IPP –> Squalene –> Lanosterol –> Cholesterol

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11
Q

What can inhibit lanosterol from becoming cholesterol?

A

Anti-fungal treatments

Tamoxifen

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12
Q

How do statin drugs work?

A

Competitive inhibitors of HMG CoA reductase

Transcription of LDL receptor and subsequent clearance of cholesterol via endocytosis

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13
Q

HMG CoA reductase is active in what form?

What can activate it?

A

Dephosphorylated form

Activated by insulin

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14
Q

What are the important proteins that play a role in controlling in the HMG CoA reductase gene?

A

SREBP
SCAP
INSIG

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15
Q

How does transcriptional control of HMG CoA reductase gene work?

A

When cholesterol is high, SREBP is the ER membrane and bound to SCAP and INSIG.

When cholesterol is low, SREBP-SCAP complex translocates to Golgi apparatus. SREBP is cleaved and binds to a sterol regulatory element to promote cholesterol production and enhance uptake into cells.

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16
Q

What are the five different types of lipoproteins?

A 
Chylomicrons
Very low density lipoproteins (VLDL)
Intermediate Density Lipoproteins (IDL)
Low Density Lipoproteins (LDL)
High Density Lipoproteins (HDL)
17
Q

What are some features of a chylomicron?

A
  • Exogenous: formed from diet and made in intestines
  • Largest
  • Least Dense
  • High concentration of TAGs
18
Q

What are some apolipoproteins found on a chylomicron?

What do they do?

A

ApoB-48: facilitates transport
ApoE: facilitates uptake into liver
ApoC-II: can break down triglycerides

19
Q

What are some apolipoproteins found on a VLDL?

What do they do?

A

ApoB-100: uptake into cells w/ corresponding receptor on cell
ApoE: facilitates uptake into liver
ApoC-II: can break down triglycerides

20
Q

What are some apolipoproteins found on a IDL?

What do they do?

A

ApoB-100: uptake into cells w/ corresponding receptor on cell
ApoE: facilitates uptake into liver

21
Q

What are some apolipoproteins found on a LDL?

What do they do?

A

ApoB-100: uptake into cells w/ corresponding receptor on cell

22
Q

Why is LDL considered “bad” cholesterol?

A

If it is not taken up by cells, can build up in arteries and cause atherosclerosis

23
Q

What are some features of HDL?

A

Smallest
Most dense
Mostly composed of proteins and phospholipids

24
Q

What are some apolipoproteins found on a HDL?

What do they do?

A

ApoA-I: esterifies cholesterol
ApoE: facilitates uptake into liver
ApoC-II: can break down triglycerides

25
Q

How are chylomicrons processed?

A

1) Nascent Chylomicrons: assembled in small intestine and transported through lymphatic system to blood stream
- only has ApoB-48

2) Mature Chylomicrons: additional apolipoproteins are added
3) ApoC-II: TAGs are hydrolyzed
4) Remnants of chylomicrons are endocytosed by liver via ApoE

26
Q

How are VLDL, IDL, and LDL processed?

A

1) VLDL produced in liver and released into bloodstream.
2) ApoC-II: TAGs are hydrolyzed –> IDL
3) Cholesterol in IDL is delivered to liver and continues to lose more TAGs
4) LDL deliver cholesterol to cells

27
Q

What is the role of LDL?

A

Transport cholesterol to peripheral tissue

Regulate de novo synthesis

28
Q

What does a LDL particle contain?

A

Shell: phospholipids and free cholesterol

Packed w/ 1500 cholesterol ester molecules

29
Q

How is HDL processed?

A

1) Synthesized in liver and small intestine
2) Picks up cholesterol from peripheral tissues
3) Esterifies cholesterol and is in core
4) Donates ApoC-II and ApoE to chylomicrons

30
Q

What are benefits of HDL?

A
  • Helps mature chylomicrons via apolipoproteins

- Retrieves cholesterol from other tissues

31
Q

What is Tangier disease?

A

Rare lipoprotein disorder: almost complete absence of plasma HDL
-loss of ABCA1

32
Q

What is Type I hyperlipoproteinemia?

A
  • inability to hydrolyze TAGs in chylomicrons and VLDL
  • due to deficiency in Apo C-II or LPL
  • high levels of plasma TAGs
  • Autosomal recessive
33
Q

What are symptoms of Type 1 hyperlipoproteinemia?

A

Abdominal pain
Acute pancreatitis
Xanthomas

34
Q

What is Type II hyperlipoproteinemia?

A

Familial Hypercholesterolemia

  • mutations in LDL receptor
  • can cause atherosclerosis
  • high levels of LDL in blood
  • mild in heterozygous, serious in homozygous
35
Q

What can happen with atherosclerosis?

A

Accumulation of LDL can become oxidized in vessel wall

  • increased vascular permeability and leukocyte adhesion
  • initiates inflammatory responses
  • macrophages become foam cells and forms plaques
  • arteries can narrow and lead to heart attacks

Year 1: 08. CPR Exam 1 (29 decks)

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