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BMB 402 > Chapter 15: Lipid Structure and Function > Flashcards

Chapter 15: Lipid Structure and Function Flashcards

1
Q

What are many lipids made from?

A

fatty acids

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2
Q

What are some of the roles that lipids serve in the body?

A
  • energy storage
  • cell membranes
  • endocrine signaling
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3
Q

Describe fatty acids

A
  • consist of a carboxylic acid and a hydrocarbon tail 4-36 C long
  • the most abundant fatty acids are unbranched chains of 12-20 carbons and are even numbered
  • can covalently bond to proteins to tether proteins to biological membranes
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4
Q

Compare saturated to unsaturated fats

A

Saturated fats contain fully reduced methylene groups (maxed out on H) and are typically solid at room temp

Unsaturated fatty acids contain at least one double bond (makes a kinked shape). Monounsaturated have one double bond while polyunsaturated FA contain multiple double bonds. They are typically liquid at room temp

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5
Q

Why are saturated FAs solid and unsaturated FAs liquid at room temp?

A

Saturated FAs have regular packing and more extensive intermolecular interactions.

Unsaturated FAs have looser packing and fewer intermolecular interactions due to the branching in their tails

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6
Q

What is hydrogenation?

A

The commercial process of using H2 gas to reduce C to C double bonds.

This process raises the melting point of lipid mixtures and converts unsaturated fatty acids to saturated fatty acids.

It produces a semisolid mixture.

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7
Q

What are trans fats?

A

Fatty acids created by partial hydrogenation. They are associated with high rates of cardiovascular disease. They were ruled unsafe by the FDA in 2013, and have been found to increase levels of LDL while decreasing levels of HDL

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8
Q

What are waxes?

A

Molecules classified as lipids that contain long chain alcohols linked to long-chain fatty acids.

They have high melting points.

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9
Q

How much energy is released from the full oxidation of a triglyceride?

A

~ 38 kJ/g

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10
Q

How are dietary TGs packaged?

A

as chylomicrons

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11
Q

How are TGs synthesized in the liver packaged?

A

as VLDL particles (lipoprotein)

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12
Q

How are TGs released from adipose packaged?

A

as albumin

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13
Q

Describe the process of TG packaging to VLDLs in the liver.

A
  • Triacylglycerol biosynthesis uses acetyl-CoA and proteins to generate palmitic acid in the cytosol
  • palmitic acid is converted to triacylglycerols and exported as VLDL particles
  • liver VLDL assembled in endoplasmic reticulum and Golgi body, then repackaged and exported to circulatory system
  • liver cells synthesize cholesterol from acetyl-CoA, which is packaged into VLDL particles as cholesterol esters
  • VLDL particles deliver triacylglycerols and cholesterol esters to tissues throughout the body
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14
Q

What are lipid droplets?

A

storage vehicles for newly formed triacylglycerols from adipocytes

they are surrounded by a phospholipid monolayer containing perilpin

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15
Q

How are triacylglycerols metabolized?

A

They are cleaved by lipases to generate free fatty acids and glycerol

Fatty acids can pass through the membrane on the luminal side of intestinal epithelial cells

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16
Q

How is the glucagon signaling pathway involved with fatty acid metabolism?

A

Glucagon signaling initiates a cascade resulting in fatty acid release to the bloodstream

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17
Q

What are the three major membrane lipids?

A
  1. glycerophospholipids
  2. sphingolipids
  3. cholesterol
18
Q

Describe glycerophospholipds

A
  • they are the most abundant membrane lipids
  • they are an important source of FA derived signaling molecules, which are released by phospholipase enzyme catalysis
  • contain two FAs and a phosphate group attached to a glycerol
19
Q

Describe sphingolipids

A

they are derived from sphingosine and one FA

20
Q

What is Tay-Sachs Disease?

A

A lipid based genetic disorder. Normally, the enzyme hexosaminidase A acts on ganglioside GM2 (a sphingolipid) to remove its terminal moiety and form ganglioside GM3.

In patients with Tay-Sachs, hexosaminidase A is defective causing a building up GM2 ganglioside in the spleen and brain.

Symptoms include developmental delays, cognitive dysfunction, and death.

21
Q

What proportion of lipids in the plasma membrane is composed by cholesterol?

A

25-40%

22
Q

What is the structure of cholesterol?

A

contains 27 carbons and a rigid four-ring steroid core

23
Q

What function does cholesterol serve in the membrane?

A

affects membrane fluidity

24
Q

What are lipid rafts?

A

Protein aggregated into discrete patches as densely packed protein complexes.

These areas contain large transmembrane proteins and act as receptors for extracellular signaling.

25
Q

How do lipids function in cell signaling?

A

The hydrophobic property of lipids contributes to their function as high-affinity stereospecific ligands that bind to hydrophobic pockets in receptor proteins

26
Q

What is cholesterol a precursor to?

A

steroid hormones and bile acids

derived from mevalonate

27
Q

Excess levels of cholesterol contribute to what condition?

A

cardiovascular disease

28
Q

What do steroid hormones do?

A

They can act as ligands for nuclear receptor proteins which mediate hormone signals by altering the expression for specific genes

They are potent signaling molecules that have a critical role in:
- cell development
- reproductive biology
- organismal physiology

29
Q

progesterone

A

synthesized by corpus luteum

functions in menstration, development of mammary tissue

30
Q

cortisol

A

synthesized by adrenal cortex

functions in liver metabolism, immune functions, adaptation to stress

31
Q

aldosterone

A

synthesized by adrenal cortex

functions in ion transport in the kidneys, blood pressure regulation

32
Q

testosterone

A

synthesized by testicles, adrenal cortex

functions in development of male reproductive organs

33
Q

estradiol

A

synthesized by ovaries

development of female reproductive organs

34
Q

What are synthetic hormones?

A

Agonists that mimic the biological response of the hormone

35
Q

dihydrotestosterone

A

natural androgen agonist that promotes male reproductive development

36
Q

nandrolone

A

potent synthetic androgen agonist that has been used by bodybuilders

37
Q

bicalutamide

A

nonsteroidal androgen antagonist used to treat prostate cancer

38
Q

Vitamin D

A

the “sunshine” vitamin converted to the active form 1,25-dihydroxyvitamin D3 from 7-dehydrocholesterol

39
Q

What are eicosanoids?

A

A group of signaling molecules derived from 20C polyunsaturated fatty acids. They have important roles in inflammation.

Eicosanoids are released from the membrane by phospholipids and modified by mitochondrial enzymes.

They’re produced by cells at their sites of action (paracrine) and have half-lives on only a few minutes.

40
Q

What are the four major classes of eicosanoids?

A

prostaglandins
prostacyclins
thromboxanes
leukotrienes

41
Q

What are NSAIDs?

A

non-steroidal anti-inflammatory drugs

42
Q

Why are selective COX inhibitors preferred to non-selective versions?

A

Selectively inhibiting COX-2 it can prevent unwanted side effects.

Non-selectively inhibiting COX-1 along with COX-2 can lead to GI issues since COX-1 is more broadly expressed and has more functions.

BMB 402 (14 decks)

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