Biochemistry Midterm 2.3 - Lipids/Membrane

Question 1

lipids are defined by

Answer 1

solubility properties, fats are lipids, not all lipids are fats

Question 2

fatty acids description and what they are found in

Answer 2

amphipathic, 3-35 carbons tail
at pH 7 carboxyl group is ionized
found in complex lipids (structural and storage) and micelles

Question 3

oleic acid systematic name

Answer 3

cis-9-octadecenoic acid

Question 4

fatty acid nomenclature

Answer 4

numbering of carbons starts from carboxyl end (reactive end) 𝚫
number carbons start from methyl end in nutrition omega ω
# of carbons: # of double bonds ^ 𝚫 # 1st carbon of double bond
ex. 18:1^𝚫9 = cis-9-octadecenoic acid

Question 5

linoleic acid in formula
alpha-linolenic acid formula

Answer 5

18:2^𝚫9,12
18:3^𝚫9,12,15

Question 6

melting point increases
solubility decreases

Answer 6

Melting point :
1) decreasing double bonds/increased saturation
2) increasing chain length
Solubility:
1) decreases as chain length increases

Question 7

saturated fatty acids

Answer 7

pack in an tight, ordered way
increased van der waals interactions
increased melting temp, takes more thermal energy to disrupt forces
cis bonds make for kinks that lower packing/melting temp

Question 8

process that changes a cis alkene to a trans alkene

Answer 8

partial hydrogenation and cis alkene isomerization

Question 9

biological health consequences of saturated fat and trans fat

Answer 9

saturated fat increase cholesterol by providing proper packing domains for cholesterol (LDL)
trans fats do the same and increase cell membrane rigidity
we don’t have the enzymes to break down trans fat bonds

Question 10

simple triacylglycerol

Answer 10

a triglyceride with 3 fatty acids of the same type

Question 11

enzyme that adds FA to glycerol and takes FA off
type of bond formed

Answer 11

acyl transferase and lipase
between the carboxyl end of a fatty acid and glycerol backbone is an ester bond formed by condensation reaction

Question 12

fat and oil definition

Answer 12

solid triacylglycerides, liquid triacylglycerides

Question 13

triacylglycerides description and why they are good for energy storage

Answer 13

storage lipid in animals (fats) and plants (seeds)
non polar, less soluble than fatty acids due to esterification of carboxyl groups
good for energy storage because more energy per carbon (reduced) and carry less water

Question 14

how to make soap

Answer 14

saponification: add strong base to triglycerides to form glycerol and crude soap

Question 15

waxes decription

Answer 15

esters of long chain fatty acids (saturated and unsaturated) with long chain alcohols (no glycerol back bone)
used as storage in plankton, waterproofing, and protection from evaporation
high melting point

Question 16

highest lipid types in plasma, organelles and lysosomes

Answer 16

cholesterol, phosphatidylcholine, and sphingolipids

Question 17

glycerophospholipids description

Answer 17

glycerol backbone, 2 fatty acids and a phosphate + head group on C3
primary structure in cell membranes
phosphate group is negatively charged at pH 7

Question 18

phosphatidic acid

Answer 18

base form of glycerophospholipids
glycerophospholipid with 2 fatty acids on C1/C2 and an H attached to phosphate group as the head group

Question 19

lysophosphatidatic acid

Answer 19

phosphate group attached to a glycerol backbone and 1 FA on C1

Question 20

head group for phosphatidylethanolamine

Answer 20

amine containing, net charge 0 at pH 7

Question 21

phosphatidylcholine
bonds
head group

Answer 21

major cell membrane component in most eukaryotes but prokaryotes can’t synthesis it
ester bonds between glycerol and FA and glycerol and phosphate, and phosphoester bond between phosphate and head group
amide containing, net charge of 0 at pH 7

Question 22

head group for phosphatidylserine

Answer 22

carboxylate and amine containing, net charge -1 at pH 7

Question 23

head group for phosphatidylglycerol

Answer 23

alcohol groups, net charge -1 at pH 7

Question 24

head group for phosphatidylinositol

Answer 24

cyclic, net charge -4 at pH 7

Question 25

cardiolipin head group

Answer 25

the large one, non cyclic, net charge -2 at pH 7

Question 26

in vitro DNA synthesis requires:

Answer 26

2 Mg2+ ions, incoming nucleotide triphosphate, a 3'-OH group that with act as a Nucleophile, 3 Asp residues

Question 27

sphingolipids

Answer 27

long chain amino alcohol backbone with a fatty acid connecter via an amide linkage on C2 polar head is attached by glycosidic or phosphodiester linkage

Question 28

ceramide

Answer 28

sphingolipid with 1 amide linked fatty acid on C2 head group is H

Question 29

sphinomyelin

Answer 29

sphingosine + phosphocholine at C3 type of phospholipid

Question 30

cerebroside

Answer 30

mono-sugar group + sphingosine found in nerve sheaths type of glycolipid

Question 31

ganglioside

Answer 31

sugars or oligosaccharides + sphingosine type of glycolipid

Question 32

glycosphingolipids

Answer 32

found on outside of plasma membranes for cell-cell recognition, as well as in blood type identification

Question 33

what phospholipid and sphingolipid are structurally similar?

Answer 33

phosphatidylcholine and sphingomyelin both have phosphocholine head

Question 34

blood type is determined by

Answer 34

glycosphingolipids. The structure of the sugar is determined by glycosyltransferase and what it transfers: Type O antigen - no active glycosyltransferase Type A antigen - transfer of N-acetylgalactosamine Type B antigen - galactose group AB is both

Question 35

phospholipase A1 phospholipase A2 phospholipase C phospholipase D

Answer 35

A1: cleaves after O at C1 A2: cleaves after O at C2 C: cleaves before phosphate group (after O at C3) D: cleaves after phosphate group (before O)

Question 36

biologically active lipids

Answer 36

no glycerol or fatty acids steroids - made from acetate or modification of other sterols ex. bile salts, hormones prostaglandins - made from modified fatty acids

Question 37

sterol structure

Answer 37

4 fused rings (almost planar, A-D), hydroxyl group off A ring, and non polar side chains phytosterols - plants cholesterol - animals no sterols in bacteria

Question 38

steroid hormones

Answer 38

oxidized derivatives of sterols, made from cholesterol in gonads and adrenals no alkyl hydrophobic chain (and therefore more polar) carried through blood attached to carrier proteins

Question 39

eicosanoids

Answer 39

signaling molecules from oxidized arachadonic acid: prostaglandins - regulate inflammation and fever thromboxanes - regulate formation of blood clots leukotrienes - smooth muscle contraction

Question 40

3 structures lipids aggregate into in water

Answer 40

micelles, lipid bilayers, and liposomes dependent on type of lipid and concentration

Question 41

micelles form with

Answer 41

amphipathic molecules with larger polar heads than tails (width, conical shaped) such as: FFA, detergents, some steroids, lysophospholipids

Question 42

lipid bilayer forms with

Answer 42

cylindrical shaped lipids (more than one tail) such as: phospholipids and sphingolipids made of 2 leaflet monolayers stabilized by van der waals, hydrophobic effect and electrostatic interactions

Question 43

liposome

Answer 43

vesicle, made of same as lipid bilayer but in a hollow sphere shape inside sphere is aqueous to store and transport hydrophilic molecules

Question 44

trilaminar membrane permeability

Answer 44

impermeable to charged ions and large molecules or proteins permeable to hydrophobic molecules, neutral gases and small uncharged polar molecules like water

Question 45

uncatalyzed membrane lipid movement catalyzed membrane lipid movement

Answer 45

lateral movement and axis spin transbilayer movement flippase - outside to inside flip (ATP dependent) floppase - inside to outside flip (ATP dependent) scramblase - either direction towards equilibrium

Question 46

why is it hard for polar molecules to pass through lipid bilayer?

Answer 46

because of hydrophobic phospholipid tails on the inside of the membrane

Question 47

outer leaflet is often more

Answer 47

positively charged

Question 48

predominant outer layer phospholipids

Answer 48

phosphatidylcholine and sphingomyelin

Question 49

predominant inner layer phospholipids

Answer 49

phosphatidylethanolamine, phosphatidylserine

Question 50

where are lipids made?

Answer 50

made in the ER and move from cis golgi apparatus to trans side for packaging

Question 51

integral/intrinsic membrane proteins

Answer 51

firmly associated with the membrane, often spanning both leaflets and contain hydrophobic and hydrophilic regions can be extracted with strong detergents, change in pH, chelating agent, urea and carbonate

Question 52

Anchored (GPI-linked) membrane proteins

Answer 52

linked during regulatory events and can be removed by detergents or phospholipases GPI is a carbohydrate motif Also called amphitropic proteins

Question 53

Peripheral (non GPI-linked) membrane proteins

Answer 53

weakly associated, easily removed by pH buffers, denaturing agents and chelating agents

Question 54

monotopic/polytopic

Answer 54

spans 1 or 2 leaflets

Question 55

membrane phases are and depend on

Answer 55

gel - liquid ordered state, individual molecules don't move, tails are fully extended and densely packed liquid - liquid disordered state, fluid phase, individual molecules move, tails are randomly oriented and loosely packed increased heat increases fluidity naturally more fluid than gel, necessary for cellular function

Question 56

how cholesterol works as a fluidity buffer

Answer 56

- amphipathic molecule, acts a buffer by broadening transition temperature (AKA melting temp) - rigid hydrophobic planar rings and hydrophobic flexible branched hydrocarbon tail with a polar hydroxyl head 1) in cold temperatures, cholesterol decreases packing of lower fatty acid tail ends which decreases melting temp 2) in warm temperatures, cholesterol increases packing of upper ends of hydrocarbon tails by immobilizing methylene groups which increases melting temp

Question 57

membrane transition temp graph with and without cholesterol

Answer 57

sudden shift from gel to fluid state without cholesterol, gradual shift with cholesterol

Question 58

kind of FA that contribute to a more fluid membrane and health benefits

Answer 58

short unsaturated fatty acids also they are more adaptable to temperatures than saturated fatty acids saturated fatty acid filled membranes are stiffer and more susceptible to rupture

Question 59

what percentage of membrane proteins are integral vs peripheral

Answer 59

70% integral, 30% peripheral