Chapter 5- Lipid Structure and Function

Question 1

lipid characterization

Answer 1

insolubility in water and solubility in nonpolar organic solvents

Question 2

2 structural building blocks of lipids and what they make up

Answer 2

Phospholipids and sterols. They make up vesicles, liposomes, and membranes

Question 3

Amphipathic

Answer 3

A molecule that has both hydrophobic and hydrophilic regions

Question 4

what happens when membrane lipids are placed in an aqueous solution?

Answer 4

they form one of three structures to maximize hydrophilic interactions and to minimize hydrophobic interactions.

1. liposome (two layer ball with inside)
2. micelle (one layer like a ball)
3. phospholipid bilayer

Question 5

phospholipid

Answer 5

1. polar head (phosphate and alcohol)

2. hydrophoblic fatty acid tail (connected to (1) by phosphodiester linkage)

Question 6

glycerol

Answer 6

three-carbon alcohol

Question 7

saturated fatty acid

Answer 7

only have single bonds, carbon is considered saturated when it is bonded to 4 other atoms with no pi bonds. (greater van der waals forces and more stability)

Question 8

unsaturated fatty acid

Answer 8

has 1 or more double bonds, introduce kinks making it hard to stack/bond/solidify

Question 9

glycerophospholipids (aka. phosphoglycerides)

Answer 9

phospholipid subtype that contain a glycerol backbone bound by ester linkages to two fatty acids and by a phosphodiester linkage to a highly polar head group (named according to the polar head group)

Question 10

sphingolipids

Answer 10

have a sphingosine/sphingoid backbone. have glycosidic linkage to sugar (glycolipid)— used in ABO blood typing system

Question 11

4 types of sphingolipids

Answer 11

1. ceramide- single hydrogen atom as head group
2. sphingomyelins
3. glycosphingolipids
4. gangliosides

Question 12

glycosphingolipids

Answer 12

2 types, mainly found on outer surface of plasma membranes

1. cerebrosides- have a single sugar
2. globosides- have 2 or more sugars

Question 13

gangliosides

Answer 13

“gangly” sphingolipids with the most complex structure and functional groups (oligosaccharides and NANA: sialic acid) in all directions

Question 14

functions of wax

Answer 14

• protection
• in animals: waxes are secreted to prevent dehydration, as a water-repellant to keep skin and feathers dry, and as a lubricant

Question 15

3 categories of signaling lipids and an important precursor to lipids

Answer 15

1. steroids
2. prostaglandins
3. fat-soluble vitamins
4. terpenes

Question 16

terpenes

Answer 16

have odor. metabolic precursor to lipid signaling molecules. built from isoprene (C5H8)

Question 17

monoterpenes

Answer 17

single terpene unit = 2 isoprene units (C10H16)– essential oils

Question 18

sesquiterpenes

Answer 18

3 isoprene units

Question 19

diterpenes

Answer 19

4 isoprene units. vitamin A is a diterpene from which retinal is derived (necessary for sight)

Question 20

triterpenes

Answer 20

6 isoprene units. can be converted to cholesterol and other steroids.

Question 21

tetraterpenes

Answer 21

8 isoprene units.

Question 22

structural characterization of steroids

Answer 22

4 cycloalkane rings (3 cyclohexane and 1 cyclopentane)
function: depends on oxidation status of these rings.
steroids are nonpolar due to large number of C and H

Question 23

cholesterol

Answer 23

1. steroid
2. major component of phospholipid bilayer (responsible for mediating membrane fluidity)
3. precursor to steroid hormones, bile acids, and vitamin D

Question 24

prostaglandins

Answer 24

1. produced by almost all cells in the body (paracrine/autocrine hormones)
2. 20-carbon molecules of unsaturated carboxylic acids derived from arachidonic acid, contain one five carbon ring.

Question 25

biological function of prostaglandins

Answer 25

act as paracrine or autocrine hormones. regulate synthesis of cyclic adenosine monophosphate (cAMP)- intracellular messenger.
downstream effects: powerful effects on smooth muscle, influence over sleep-wake cycle, elevation of body temp. associated with fever and pain.

Question 26

how do nonsteroidal anti-inflammatory drugs (NSAIDs) work?

Answer 26

(ex: asprin) they inhibit the enzyme cyclooxygenase (COX), which aids in the production of prostaglandins

Question 27

vitamin

Answer 27

essential nutrient that cannot be adequately synthesized by the body, so it must be consumed in the diet.

Question 28

Vitamin A

Answer 28

aka: carotene (CARROTS HIGH IN VITAMIN A- good for vision). unsaturated hydrocarbon. important for vision, growth, development, and immune function. (ex: retinal, retinol- storage form of vitamin A is oxidized to retinoic acid- a hormone that regulates gene expression during epithelial development)

Question 29

Vitamin D

Answer 29

aka: cholecalciferol. can be consumed or formed through sun interaction. converted to calcitriol (biologically active form of vitamin D) in the liver and kidneys. increases calcium and phosphate uptake in intestines (promoting bone production).

lack of vitamin D: rickets- condition seen in children with underdeveloped/curved long bones as well as impeded growth.

Question 30

Vitamin E

Answer 30

tocopherols and tocotrienols. 
characterized by a substituted aromatic ring with a long isoprenoid side chain. hydrophobic. 
biological antioxidants (ring destroys free radicals)

Question 31

Vitamin K

Answer 31

phylloquinone (K1) and menaquinones (K2). aids in formation of prothrombin (important clotting factor in blood). also required to introduce calcium binding sites on 3 Ca2+ dependent proteins.

Question 32

triacylglycerols (aka. triglycerides)

Answer 32

class of lipids specifically used for energy storage

Question 33

why are lipids so good to store energy?

Answer 33

1. carbon atoms of fatty acids are more reduced than those of sugars (which contain numerous alcohol groups)–so oxidation releases more energy
2. they are hydrophobic, dont draw in water for stability, making them lighter in weight than polysaccharides
3. layers of lipids are good for cold temperatures (energy storage and insulation)

Question 34

structure of triglycerides

Answer 34

3 fatty acids (usually different) bound by ester linkages to glycerol – they are nonpolar hydrophobic compounds

Question 35

2 main methods of energy storage in body

Answer 35

1. triacylglycerols in adipose tissue (lasts for months)

2. carbohydrates in glycogen (more easily accessible)

Question 36

adipocytes

Answer 36

special cells that store large amounts of fat and are found primarily under the skin, around mammary glands, and in abdominal cavity. can travel bidirectionally in bloodstream b/w liver and adipose tissue.

Question 37

free fatty acids

Answer 37

circulate in blood bound noncovalently to serum albumin

Question 38

saponification

Answer 38

made up of fatty acids and produces soap. ester hydrolysis of a triacylglycerol using a strong base (usually lye: common name for NaOH or KOH) fatty acid salt = soap

Question 39

surfactant

Answer 39

lowers surface tension at the surface of a liquid, serving as a detergent or emulsifier (mixing 2 solutions that typically wouldnt mix like oil and vinegar–forming a colloid)

Question 40

colloid

Answer 40

when two insoluble compounds mix due to soap and colloid forms which happens as a result of micelle formation