Module 1: Part 5 Lipids

Question 1

Why do all foods have fat?

Answer 1

Because cell membranes are fat

Question 2

Lipid classification

Answer 2

Soluble in organic solvents (alcohol/ether), but not water
no common subunit

Question 3

Cholesterol is

Answer 3

a steroid precursor
derived from acetyl-coA
waxy substance, expensive to produce (animals) and cannot be oxidized

Question 4

Saturated fatty acids to know (and formula)

Answer 4

Palmitic acid, C16:0
Stearic acid, C18:0

found in lard and beef tallow

Question 5

Unsaturated fatty acid examples

Answer 5

Oleic acid, C18:1, ex. Olive oil

Linoleic acid, C18:2 (essential), Ex. safflower oil

Linolenic, C18:3 (essential)

Arachadonic acid, C20:4 (nonessential sort of, derived from linolenic acid but not efficient in humans)

Question 6

Short to very long chain metrics

Answer 6

Short: 2-4
Medium 6-12
Long: 14-20
Very long: 22+

Question 7

Steroid receptors
Examples

Answer 7

Homodimer nuclear receptor

GR - Glucocorticoid
MR - mineralcorticoid
PR - progesterone
AR - androgen
ER- estrogen

Question 8

RXR Heterodimer nuclear receptors
Examples

Answer 8

Binds with transcription factor and then gene
T3R - Thyroid hormone
RAR - all-trans retinoic acid (vitamin A)
VDR - vitamin D
PPAR - fatty acids/fatty acid metabolites
EcR - ecdysone (steroid for molting in insects)
FXR - bile acids
CAR - androstane (weak androgen)
LXR - oxysterol (cholesterol derivative)
PXR - xenobiotics

Question 9

Dimeric orphan receptors
Examples

Answer 9

homodimeric nuclear receptors with unknown ligand that regulate a known class of gene
RXR - 9-cis retinoic acid
COUP
HNF-2
TR2
TLX

Question 10

Monomeric/tethered orphan receptors

Answer 10

not dimerized receptor
NGFI-B
SF-1
Rev-erb
ROR
ERR

Question 11

How steroids enter cell

Answer 11

either in high concentrations or escorted with receptor from cytosol

Question 12

Type I nuclear receptors

Answer 12

Reside in cytoplasm, in complex with chaperone proteins
When ligand binds, receptor leaves chaperone and forms homodimer complex bound to hormone response element (HRE) of DNA
Ex. steroid receptor

Question 13

Type II nuclear receptors

Answer 13

Type II receptors localized in nucleus
No ligand - interact with co-repressor
Yes ligand - interact with co-activators
Forms heterodimer with RXR (retinoid X receptor)
Direct repeat HRE

Question 14

Type III nuclear receptors

Answer 14

Similar to type II - localized in nucleus
Ligand binds corepressor –> becomes coactivator
Forms homodimer on HRE (no RXR)
Direct repeat HRE

Question 15

Type IV nuclear receptors

Answer 15

like type III but bind HRE as a monomer
localized in nucleus
No ligand - interact with co-repressor
Yes ligand - interact with co-activators

Question 16

Why essential fatty acids are essential in humans
Ex.

Answer 16

Humans cannot make double bonds from position 8 or less (counting from methyl end)

Ex. Linoleic acid (w-6) and linolenic acid (w-3)

Question 17

EFAs are important for the synthesis of:
Functions involved

Answer 17

Substrates for eicosanoids: prostaglandins, leukotrienes and thromboxanes

Involved in inflammation response, immune function, blood clotting, vasodilation, kidney and cognitive function

Question 18

Symptoms of EFA deficiency and excess

Answer 18

Deficiency: growth retardation, sparse hair growth, dry skin/eczema, weakness, depression, slow wound healing, susceptibility to infection, edema, vision problems, neurological problems (severe deficiency)

Excess: excessive bleeding due to slow blood clotting
No current UL

Question 19

Uses of fatty acids in the body

Answer 19

Energy source, structural components, covalent modification of proteins, signalling molecules, ligands for TF

Question 20

Carnitine role and derivation

Answer 20

Carnitine is required to transport long chain FA into mitochondria for oxidation
Carnitine is derived from lysine and methionine and can be deficient in vegans or during parenteral nutrition

Question 21

Acylation is

Answer 21

The addition of a fatty acid