Biochem Exam 3

general functions of carbohydrates

source of energy, cell membranes and walls, marker molecules, structure, precursors

carbohydrate nomenclature ending

-ose

Determining L or D from fischer projection

The highest # chiral C has the OH group to the left (L) or right (D)

Determine L or D from Hawthorne projection

terminal group attached to highest # chiral center is down (L) or up (D)

carbohydrate structural isomers

ketose vs aldose

enantiomers of carbohydrates

L and D, all chiral centers are flipped

epimer

differs at one of several chiral centers

anomer

alpha or beta, differs at a new chiral center from formation of ring

diastereomer clustering

diastereomer > epimer > anomer

natural sugars are in what conformation?

D

Glucose

aldohexose, right left right right

Fructose

ketohexose, left right right

Galactose

aldohexose, right left left right, C4 glucose epimer

carbohydrate cyclization

-OH of highest # chiral center interacts with carbonyl, C1 and C5 in aldoses and C2 and C5 in ketoses

anomeric carbon

aka reducing end, reactive carbon, formed by interaction between carbonyl and highest # chiral center -OH

alpha configuration

anomeric C’s -OH is down

beta configuration

anomeric C’s -OH is up

alpha and beta for L enantiomers

opposite

alpha and beta in vivo

can interconvert = mutarotation

pyranose

6 membered ring containing O

furanose

5 membered ring containing O

glycosidic bond

bond between anomeric carbon and hydroxyl of another monomer, condensation reaction

sucrose

one glucose and one fructose, alpha,beta(1→2) linkage, uses both anomeric carbons, non-reducing sugar

lactose

galactose and glucose, beta(1→4) linkage

polysaccharide functions

storage, structural, recognition

storage polysaccharides

branched, starch, glycogen

structural polysaccharides

linear, chitin, cellulose

recognition polysaccharides

heteropolysaccharides

starch

composed of two homopolysaccarides (amylose and amylopectin), alpha(1→4) with a few alpha(1→6) (branch points)

amylose

linear and helical, only alpha(1→4) linked, 10-30% of starch

amylopectin

mostly linear with branch points, 70-90% of starch

how often does amylopectin have branch points / alpha(1→6) linkages

every 12-30 residues

cellulose

beta(1→4) linked, forms strong, flat sheets with lots of hydrogen bonding, polar but water insoluble

glycogen

similar in structure to amylopectin but with branch point every 8-12 residues

glycoprotein

protein bound to reducing end of a saccharide, often at Ser, Thr, or Asn

O-linkage

glycoprotein bound to O, involves Ser or Thr

N-linkage

glycoprotein bound to N, involves Asn

glycolipids

lipid bound to reducing end of a saccharide, typically O-linked

Generic carbohydrate molecular formula

Cn(H2O)n

Examples of blood glucose tests

Fehling’s, Tollen’s, Benedict’s

What do blood glucose tests sense?

free anomeric carbons

reducing end

anomeric C

non-reducing end

not the anomeric carbon, C4

Calories per 1 gram fat

9

Calories per 1 gram protein

4

Calories per 1 gram carb

4

Calories per 1 gram alcohol

7

lipid

most diverse type of biomolecule, defined by low solubility in water and high solubility in nonpolar solutes, largely hydrocarbon

main types of lipids / functions

storage, membrane, specific biological activities

fatty acid

simplest unit of lipids, amphiphatic with carbonyl head group and hydrocarbon tail

How many carbons are typically in a fatty acid tail

can be 4-36, typically 12-20

saturated fatty acid

no double bonds between carbons, max amount of hydrogens

monounsaturated

contains one double bond between carbons

polyunsaturated

more than one double bond between carbons

fatty acid double bonds are cis or trans?

cis

common fatty acid double bond locations?

C9, C12, C15

what does a 18:2 (delta 9,12) fatty acid mean?

18 carbons in tail, two double bonds at carbons 9 and 12

what increases melting temp?

longer carbon chain, unsaturation

serum albumin

transport molecule for fatty acids in the blood

can fatty acids be free in the body?

no

types of storage lipids

triglycerides and waxes

triglyceride structure

glycerol backbone and 3 fatty acids

humans store enough triglycerides to survive for…

3 weeks

other triglyceride functions?

insulation, buoyancy

waxes structure

ester of long carbon chain and long alcohol chain

how long is the carbon chain portion of a wax?

14 to 36 carbons

how long is the alcohol chain portion of a wax?

16 to 30 carbons

other functions of waxes

water repellent

types of membrane lipids

phospholipids, glycolipids (sphingolipids), sterols

membrane

consists of two leaflets (=bilayer) of lipids

types of phospholipids

glycerophospholipids and phosphosphingolipids

What is the polar group of phospholipids?

phosphate-X

glycerophospholipid structure

glycerol backbone, 2 fatty acids (typically one saturated and one unsaturated), phosphate group

glycerophospholipid parent compound

phosphatidic acid

phosphosphingolipid structure

sphingosine backbone, one fatty acid, phosphate group

sphingosine

backbone that wraps around larping as a 15 carbon fatty acid, contains a -OH at the corner

sphingolipid bond to fatty acid

amide linkage instead of ester

classes of sphingolipids

phosphosphingolipids and glycosphingolipids

classes of glycosphingolipids

cerebosides and gangliosides

glycosphingolipid structure

sphingosine backbone, fatty acid, -O-sugar

cereboside

contains one sugar

ganglioside

contains 2+ sugars and sialic acid (adds neg charge)

lipase

enzyme that degrades phospholipids and sphingolipids in lysosomes

How specific are lipases?

Each hydrolyzable bond has its on enzyme

shortest ganglioside

GM3

longest ganglioside

GM1

sphingolipid parent compound

ceramide

sterol structure

x - 3 6 membered rings - 5 membered ring - alkyl side chain, planar

sterols increase membrane flexibility when

with saturated fats

sterols decrease membrane flexibility when

with unsaturated fats

main categories of lipids with specific biological activities

isoprenoids and eicosoprenoids

types of isoprenoids

steroids, terpenes, and vitamins

steroids

hormones, oxidized derivatives of sterols, lack nonpolar group

terpenes

comprised of five carbon units with conjugated double bonds (isoprene)

vitamins

both fat-soluble (can be stored) and -insoluble, cannot be synthesized in the body

vitamin A

20 C terpene hormone made from beta carotene, precursor to retinol and retinoic acid

types of eicosoprenoids

prostaglanids, thromboxanes, and leukotrienes

eicosoprenoids are derived from

arachidonic acid (20:4 delta 5, 8, 11, 13)

prostaglanids

5 carbon ring, participate in pain, fever, inflammation, smooth muscle contraction

thromboxanes

6 carbon ring, participates in blood clotting (with help of vitamin K)