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Biochemistry Exam 3 > Chapter 29: Lipid Synthesis: Storage Lipids, Phospholipids, and Cholesterol > Flashcards

Chapter 29: Lipid Synthesis: Storage Lipids, Phospholipids, and Cholesterol Flashcards

0
Q

What is the storage form of FAs?

A

Triacylglycerol

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1
Q

Lipids are made from _____ or from their breakdown products.

A

Fatty acids

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2
Q

Phospholipids and sphingolipids make up…

A

Membrane lipids

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3
Q

Membrane components and precursor to steroid hormones

A

Cholesterol

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4
Q

What is the precursor of storage lipids?

A

Phosphatidate

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5
Q

Phosphatidate (diacylglycerol 3-phosphate) is formed by the addition of _____ to _____.

A

Two fatty acids to glycerol 3-phosphate

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6
Q

Glycerol 3-phosphate –> _____ –> _____.

A

–> Lysophosphatidate –> Phosphatidate

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7
Q

What is bound to ER and synthesizes triacylglycerol from phosphatidate and acyl CoA in liver?

A

Triacylglycerol synthase

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8
Q

TAG is transported to _____ or _____

A

Muscle (fuel) or Adipose tissue (storage)

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9
Q

Phosphatidate –> DAG –>

A

TAG

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10
Q

Phosphatidate is the precursor to make…

A

Triacylglycerols (TAG)

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11
Q

Phospholipids are generated from _____ and _____ in the ER.

A

Phosphatidate and Alcohol

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12
Q

Phospholipid synthesis requires the activation of _____ to provide the needed energy

A

Either alcohol or phosphatidate

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13
Q

DAG is activated by forming _____.

A

CDP-diacylglycerol

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14
Q

In other cases, the alcohol is activated by _____ and subsequent _____ to form _____.

A

Activated by phosphorylation and subsequent reaction with CTP to form CDP-alcohol

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15
Q

The activated alcohol in phospholipid synthesis reacts with _____ to form the phospholipid.

A

Diacylglycerol

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16
Q

Sphingolipids are synthesized from _____.

A

Ceramide

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17
Q

Sphingolipids: Membrane lipids found in all eukaryotic cells, have a _____ instead of a glycerol bakcbone.

A

Sphingosine backbone

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18
Q

Sphingolipids are synthesized from _____ and _____.

A

Palmitoyl CoA and serine

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19
Q

What is the initial product of sphingolipid sythesis?

A

Ceramide

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20
Q

The _____ of ceramide is substituted to form other sphingolipids.

A

Terminal hydroxyl group

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21
Q

_____ is found in the extracellular fluid in lungs and prevent lung collapse after exhaling.

A

Dipalmitoyl phosphatidylcholine

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22
Q

Describe Respiratory Disease Syndrome

A

Failure to synthesize sufficient dipalmitoyl phosphatidylcholine, leading to collapse of the lung

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23
Q

Describe Tay-Sachs Disease.

A
  • Inability to degrade ganglioside (phospholipids) due to lack of beta-N-acetylhexosaminidase in lysosomes
  • Neurons become swollen with lipid-filled lysosomes, which leads to lack of psychomotor skills and blindness
  • Tay-Sachs disease results in death by age 3
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24
What is a key regulatory enzyme in lipid metabolism?
Phosphatidic Acid Phosphatase
25
What catalyzes the conversion of phosphatidate to diacylglycerol?
Phosphatidic acid phosphatase (regulates lipid metabolism)
26
Different lipids are synthesized depending on whether the phosphatase is _____ or \_\_\_\_\_.
Active or Inactive
27
Loss of phosphatase activity in mice results in loss of _____ and the development of \_\_\_\_\_.
Loss of body fat Development of insulin resistance
28
Excess phosphatase activity results in \_\_\_\_\_.
Obesity
29
No cholesterol = ?
No membrane function
30
Cholesterol is synthesized from \_\_\_\_\_.
Acetyl Coenzyme A
31
\_\_\_\_\_ is the primary site of cholesterol synthesis.
Liver
32
All 27 carbons of cholesterol are derived from \_\_\_\_\_.
Acetyl CoA
33
Cholesterol is synthesized from acetyl CoA to _____ to \_\_\_\_\_.
Mevalonate to isopentenyl pyrophosphate
34
6 molecules of isopentenyl pyrophosphate are condensed into \_\_\_\_\_.
Squalene
35
Squalene is cyclized into...
Cholesterol
36
What is the rate-limiting step of cholesterol synthesis?
Mevalonate formation
37
\_\_\_\_\_ initiates the synthesis of cholesterol
Formation of mevalonate
38
First step in the synthesis of cholesterol is the formation of mevalonate by...
HMG-CoA Reductase
39
HMG-CoA Reductase catalyzes the _____ and is the major _____ for cholesterol synthesis.
Catalyzes the committed step and is the major control site
40
HMG-CoA Reductase is an _____ in the \_\_\_\_\_.
Integral membrane protein in the ER
41
In other words, mevalonate determines...
How much cholesterol is synthesized by the cell
42
HMG-CoA reductase is controlled by four different mechanisms in response to cellular cholesterol levels:
1. Regulation of transcription 2. Covalent modification 3. Regulation of translation 4. Control of degradation
43
HMG-CoA Reductase synthesis rate is controlled by...
SREBP
44
HMG-CoA Reductase: When cholesterol levels increase,
Degradation of the reductase occurs
45
HMG-CoA Reductase: Phosphorylation will
Inactivate the enzyme
46
Cholesterol and triacylglycerols are NOT _____ and transported in the blood in form of _____ particles.
NOT water-soluble and transported in the form of lipoprotein particles
47
Lipoprotein particles consist of a _____ component and various \_\_\_\_\_.
Protein component and various lipids
48
The protein(s) serve to _____ the lipids and to _____ the particles to specific targets.
Serve to solubilize the lipids and to direct the particles to specific targets (specific tissues)
49
Lipoprotein particles are classified according to \_\_\_\_\_.
Increasing density
50
Proteins are _____ than lipids.
Denser The higher density lipoproteins have MORE protein
51
VLDL is what % lipid?
98%
52
Cholesterol is carried by \_\_\_\_\_.
LDLs.
54
High levels of HDL...
Decrease the risk for heart disease
55
LDL _____ bloodstream; HDL _____ bloodstream.
LDL brings chol. to bloodstream; HDL removes chol. from bloodstream
56
The major carrier of cholesterol in the blood
Low-density lipoprotein (LDL)
57
Carries cholesterol released into the blood back to the liver - reverse cholesterol transport
High-density lipoprotein (HDL)
58
Which type is known as the 'bad' cholesterol?
LDL - can cause heart attacks
59
LDL plays a central role in...
Cholesterol Metabolism
60
LDLs deliver cholesterol to peripheral tissues and cholesterol enters the cell by \_\_\_\_\_.
Receptor-mediated endocytosis
61
What is the genetic disease that results from the **absence of functional LDL receptor**?
Familial hypercholesterolemia * High levels of cholesterol and LDL in plasma * Excess LDL contribute to development of heart attacks
62
What is the goal to treat high blood cholesterol?
* Goal is to **increase # of LDL-R** to more effectively remove cholesterol
63
How do you treat high blood cholesterol? 2 Treatments
1. _Decrease new cholesterol synthesis_ by inhibition of HMG-CoA reductase by a class of drugs called **statins**. 2. Block the uptake of dietary cholesterol * Blocked by ingesting a **resin that binds to the bile salts**
64
HDL protects against...
Atherosclerosis
65
HDL is considered the 'good' cholesterol because it can _____ by retrieving cholesterol from other tissues to the liver for excretion.
Prevent heart attacks
66
What is the precursor to steroid hormones, vitamin D and bile salts?
Cholesterol
67
Steroid hormones are crucial \_\_\_\_\_.
Signaling molecules
68
All five major classes of steroid hormones are derived from \_\_\_\_\_.
Cholesterol
69
Vitamin D is derived from cholesterol by \_\_\_\_\_.
Energy of sunlight
70
Regulation of calcium and phosphate metabolism
Vitamin D
71
Active form of vitamin D formed from cholesterol
Calcitriol
72
Deficiency of vitamin D results in...
* **Rickets**: inadequate calcification of cartilage and bone
73
In adults, vitamin D deficiency results in...
**Osteomalacia**, a condition characterized by soft and weak bones
74
T or F: HMG CoA reductase catalyzes the first committed step of cholesterol synthesis.
True
75
T or F: HMG CoA reductase can be regulated by phosphorylation.
True
76
T or F: The absence of sterols results in an increase in HMG CoA reductase degradation
False
77
T or F: SREBP is involved in transcriptional regulation of the HMG CoA reductase gene
True
78
T or F: Statins are competitive inhibitors of HMG CoA reductase.
True
79
Lipids in the intestine are coated with _____ and digested by \_\_\_\_\_?
* Coated with bile salts * Digested by pancreatic lipases
80
Which is NOT a method for regulation of HMG CoA reductase? * Inactivation due to phosphorylation by AMP-dependent kinase * Alteration in rate of translation of reductase mRNA by dietary cholesterol * Regulation of rate of synthesis of reductase mRNA by SREBP * Proteolytic degradation of reductase controlled by cholesterol levels * Transportation of reductase to the mitochondria controlled by cholesterol levels
Transportation of reductase to the mitochondria controlled by cholesterol levels
81
Cholesterol is used in formation of: * Bile salts * Testosterone and other steroid hormones * Cholesterol esters * Vitamin D
All are correct
82
If levels of cholesterol are low: * Proteolysis of HMG CoA reductase is increased * HMG CoA reductase is phosphorylated by AMP-activated protein kinase * HMG CoA reductase is translocated to the nucleus * SREBP is cleaved by a protease, allowing the DNA binding domain to increase transcription of the HMG CoA reductase gene * HMG CoA reductase expression is not altered in any way
SREBP is cleaved by a protease, allowing the DNA binding domain to increase transcription of the HMG CoA reductase gene
83
Lipoproteins: * Are used primarily to transport amino acids throughout the body * Contain hydrophobic cores with triacylglycerols and cholesterol esters * Have hydrophobic surfaces with charged carbohydrates * Contain only cholesterol as a lipid component * Function only in the liver
Contain hydrophobic cores with triacylglycerols and cholesterol esters

Biochemistry Exam 3 (10 decks)

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