Biochem 2: Lipids and Membranes

Question 1

lipids are a

Answer 1

heterogeneous class of naturally occurring organic compounds

• insoluble in water but soluble in operatic organic solvents
• some are amphipathic

Question 2

forms of lipids include (2)

Answer 2

• open chain forms

- cyclic forms

Question 3

open chain forms of lipids

Answer 3

• fatty acids, triacylglycerols, sphingolipids, phosphoacylglycerols, glycolipids
• lipid soluble vitamins
• prostaglandins, leukotrienes, and thromboxanes

Question 4

cyclic forms of lipids

Answer 4

-cholesterol, steroid hormones, and bile acids

Question 5

fatty acids are

Answer 5

an unbranched chain carboxylic acid, most commonly of 12-20 carbons
examples include oleic, palmitic, and linoleic

Question 6

shorthand notation for fatty acids is

Answer 6

carbons : # double bonds

Question 7

saturated vs. unsaturated

Answer 7

double bonds= saturated (kicks, more tightly packed together, higher melting points)
single bonds - unsaturated

Question 8

the greater the degree of unsaturation, the _____ the melting points

Answer 8

lower

Question 9

in most unsaturated fatty acids, the ____ isomer predominates, the ____ isomer is rare

Answer 9

cis isomer predominates

trans isomer rare

Question 10

triacylglycerol (triglyceride) is an

Answer 10

ester of glycerol with three fatty acids

Question 11

hydrolysis of triglycerides

Answer 11

can be hydrolyzed with base to yield glycerol and soaps

Question 12

lipases are enzymes that:

Answer 12

hydrolyze esters in triglycerides

Question 13

phosphoacylglycerols abundance and where they are found

Answer 13

second most abundant group of naturally occurring lipids, and they are found in plant and animal membranes

Question 14

phospholipases are

Answer 14

enzymes that hydrolyze specific bonds in phospholipids

Question 15

what are waxes made up of

Answer 15

a complex mixture of esters of long-chain carboxylic acids and alcohols

Question 16

where are waxes found

Answer 16

as protective coatings for plants and animals

Question 17

sphingolipids contain _____ and are found in

Answer 17

sphingosine- a long chain amino alcohol
-found in plants and animals, abundant in nervous system
(structural similarity to phospholipids)

Question 18

glycolipids

Answer 18

a compound in which a carbohydrate is bound to an -OH group of the lipid

Question 19

the sugars in glycolipids are mostly

Answer 19

glucose or galactose

-many glycolipids are derived from ceramics

Question 20

glycolipids with complex carbohydrate that contains more than 3 sugars are known as

Answer 20

gangliosides

Question 21

structure of steroids

Answer 21

a group of lipids that have fused-ring structure of 3 six-membered rings, and 1 five-membered ring

Question 22

the molecular basis of membrane structure is in lipid components, describe them

Answer 22

• polar head groups are in contact with the aqueous environment
• nonpolar tails are buried within the bilayer

Question 23

the major force driving the formation of lipid bilayers is

Answer 23

hydrophobic interaction

Question 24

the arrangement of hydrocarbon tails in the interior can be either

Answer 24

rigid or fluid

• rigid if rich in saturated fatty acids
• fluid if rich in unsaturated fatty acids

Question 25

plant membranes have a ____ percentage of unsaturated fatty acids than in animal membranes

Answer 25

higher

Question 26

the presence of cholesterol is characteristic of ____ membrane

Answer 26

animal

Question 27

_____ membranes are less fluid (more rigid) than ____ membranes

Answer 27

animal membrane are less fluid/more rigid

Question 28

the membrane of _____ which contain no appreciable amounts of steroids, are most fluid

Answer 28

prokaryotes

Question 29

functions of membrane proteins

Answer 29

• transport substances across membranes
• act as receptor sites
• and sites of enzyme catalysis

Question 30

integral vs. peripheral proteins

Answer 30

• integral are embedded in the lipid bilayer

- peripheral are only loosely associated with the membrane

Question 31

what is passive transport and what are the types

Answer 31

passive transport is driven by a concentration gradient

-simple diffusion and facilitated diffusion

Question 32

simple vs. facilitated diffusion

Answer 32

both passive transport

• simple diffusion: a molecule or ion moves through an opening
• facilitated diffusion: a molecule or ion is carried across a membrane by a carrier/channel protein

Question 33

active transport and types

Answer 33

active transport is a substance moved against a concentration gradient
-primary active transport and secondary active transport

Question 34

primary active transport

Answer 34

transport is linked to the hydrolysis of ATP or other high energy molecule (for example Na+/K+ pump)

Question 35

secondary active transport

Answer 35

driven by concentration gradient established by primary active transport

Question 36

channel proteins vs. ion channels

Answer 36

• channel proteins: integral membrane proteins that form a channel
• ion channels: channel proteins with hydrophilic pores

Question 37

most channel proteins are ___

Answer 37

gated

can be closed or open to ion passage

Question 38

channel protein gate opens when:

ligand vs. voltage gated

Answer 38

protein is stimulated to change shape by a chemical signal (ligand) or an electrical charge difference (voltage-gated)

Question 39

function of vitamin A

Answer 39

serves as the site of the primary photochemical reaction in vision

Question 40

function of vitamin D

Answer 40

regulates calcium (and phosphorus) metabolism

Question 41

function of vitamin E

Answer 41

serves as an antioxidant and is necessary for reproduction in rats and may be necessary for reproduction in humans

Question 42

function of vitamin K

Answer 42

has regulatory function in blood clotting

Question 43

what is the precursor for vitamin A (retinol)

Answer 43

beta-carotene

Question 44

beta carotene -> vitamin A requires

Answer 44

enzyme-catalyzed cleavage of beta-carotene followed by reduction (gives 2 molecules of vitamin A)

Question 45

what is rhodopsin and what is it required for

Answer 45

rhodopsin is a pigment required for vision that is made from vitamin A

Question 46

what is the active molecule for rhodopsin formation and what does it react with?

Answer 46

the active molecule is retinal (vitamin A aldehyde) and it reacts with the protein opsin to form rhodopsin

Question 47

the primary chemical event of vision in rod cells is

Answer 47

absorption of light by rhodopsin followed by isomerization of the 11-cis double bind to the 11-trans double bond

Question 48

what is vitamin D and what is it used for

Answer 48

a group of structurally related compounds that are involved in the regulation of calcium and phosphorus metabolism

Question 49

what is vitamin E used to trap and how were those formed ?

Answer 49

vitamin E is an antioxidant which traps HOO and ROO radicals formed as a result of oxidation by O2 of unsaturated hydrocarbon chains in membrane phospholipids

Question 50

what is vitamin K made of and what is it used in

Answer 50

vitamin K has an important role in the blood-clotting process
-made of long unsaturated hydrocarbon side which consists of repeating isoprene units