Unit 3 biochemistry b4 quiz

what are carbohydrates

carbohydrates- aka sugars- have a variety of functions

1. important source of energy- plant starches consist of chains of linked glucose molecules which are broken down into glucose for generation fo ATp and other precursors

2. found in cell membranes/walls and in protective coatings

3. carbs are maker molecules that allow one type of cell to recognize and interact with other types of cells

4. they serve as precursors for a number of biological molecules, including amino acids, lipids, and nucleic acids

hydrates of carbon

Cn(H2O)n

more than half of all organic carbon is found in carbohydrates

they are classified as mono, di, oblige, and polysaccharides according ot the number of simple sugars they contain

saccharide is latin for

sweet taste!

one of the characteristics of sugars is that they taste sweet

sweetness is a SUBJECTIBE INTERACTION between molecules and taste receptors in your mouth

the sweetness receptor is encoded by two genes called

TAS1R2 and SAS1R3

these encode for GPCR

monosaccharides (simple sugars)

aldose and ketose

one has an aldehyde one has a keytone

• colorless, crystalline

• moneclature is based on number of carbons (trios, tetrose, pentose)

• D,L system

aldoses with ____ or more carbons and ketoses with _____ or more carbons are chiral

3;4

enantiomers and diasteriomeers

D and L are enantiomers- non superimposable mirror images

diasteriomers- stereoisomers that are not mirror images-D altros and D glucose

• include epimers- different at one of several asymmetric carbon atoms

  • anomers- differ at a NEW asymmetric carbon atom formed upon ring closer

D or L configuration for natural sugars

only D configuration

carbs can bind to D-sugars but not to their L isomers

diasteriomers

have different physical properties ie solubilities

epimers

two sugars that differ only in the configuration around one carbon atom

both d-mannose and D-galactose are epimers of D-glucose but they are not epimers of each other

glucose

six carbon aldehyde containing sugar- aldose

primary fuel for living cells

exclusive energy source for brain cells, erythrocytes, and cells of the eye

dietary sources include plant starch and the disaccharides lactose, maltose, and sucrose

fructose- fruit sugar

ketose sugar- hetohexose

twice as sweet as sucrose and is often used in food products in smallr amounts, produces the same sweetening effect with fewer calories

galactose

necessary to synthesize a variety of biomolecules

• lactose- mammary glands

• lglyco and phospholipids (carbs and lipids)

• proteoglycans/glycoporteins (carbs and proteins)

galactosemia

genetic disorder which an enzyme required to metabolize galactose is missing. accumulation causes liver damage, cataracts and severe mental retardation

fisher and Haworth projections

sugars normally exist as cyclic molecules rather than as the open chains forms due to higher stablity

cyclization takes place as a result of an interaction between the functional groups on distant carbons→ interaction between hydroxyl and carbonyl, highest numbered chiral carbon

• between carbon 1 and 5 in aldohexoses to for a hemiacetal

• c2 and c5 in ketohexoses to form a hemiketal

cyclization

carbonyl carbo become new chiral center called the anomeric carbon

therefore cyclic forms possess anomeric carbons and the cyclic alpha and beta forms are anomer’s of each other

alpha and beta

alpha down beta up unless aldose is on the same plane then beta

mutarotation

sugars can interconvert between alpha and beta forms in vivo

for l sugars where is the ch2oh

down

cyclization of ketoses

pyranoses and furanoses

six membered oxygen ring are pyranoss

five membered oxygen ring are furanoses

If something is a fisher projection what stereochemistry can it have

NOT alpha and beta and pyre/furan

CAN- glucose/fructose/galactose and D/L

fructose

glucose

galactose

blood glucose testing

the ring forms exist in equilibrium with the open-chains forms

aldehyde can reduct carbon 2+ to +

aldehyde can reduct Ag+ to 0

allows detection of reducing sugars, such as glucose

modern detection techniques use colorimetric and electrochemical tests with glucose oxidase

the glycosidic bond

two sugar molecules can be joined via a glycosidic bond between an anomeric and hydroxyl carbon

• reducing hemiacetal end still has free anomeric carbon

• nonreducing end- no amoebic carbond

• a glycoside- contains a glycosiding bond

important hexose derivatives

joining monosaccardies

glycosidic bonds btw monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides

disaccharides are the most common form of oligosaccharides

disaccharides

glycosides composed of two monosaccharide untis

significant source of calories in many human diets- lactose and sucrose

digestion of disaccharides is medicated by enzymes synthesized by cells lining the small intestine

surcose

common table sugar- anemia sgare

glucose and fructose

produced in the leaves and stems of plants

no free anomeric carbon

dietary considerations for carbs

gram to gram, sugars contain an equivalent number of carrels as proteins

40-60% of caloric intake by a typical American should be carbs

• 90% for soem individyals

• average college age male consumes 400g carbs per day, mostly starch and sucrose

biggest diet risk to excess of sugar is tooth decay

lactose

milk sugar- glucose and galactose

lactose intolerance is a common enzyme deficiency the disaccharide passes into the large intestine, where bacteria digest the lactose and produce co2 h2 and irritating organic acids, thereby causing diarrhea, bloating and cramps.

roughly 70% of the world’s population begins losing the ability ot synthesize lactase- the glycosides that catalyzes the digestion of the lactose in milk immediately after weaning off breast milk

structure and chemistry of polysaccharides- GLYCANS

function:

storage- of sugar + storing energy- starch and glycogen

structure- we dont use carbs for structure- bugs do- exosekelton- chitin and cellulose

recognition- viruses recognize our cells cuz of our sugars- cell surface polysaccharides are almost entirely glucose

homo vs heteropolysaccharide

storage nd structure are homo and cell surface is hetero

polysaccharides two different structures

large moleucle containing hundeds to thousands of sugar units

linear or branched

the molecular weights have no fixed values- reflection of the metabolic state of the cell producing them- can get buffer or smaller

starch and cellulose

starch- glycsoe storage molecule in plants

mostly alpha 1→4 linked glucose with a few alpha 1→6

→ helps to form a branched structure

cellulose- primary structural component of plant cells b1_>4 linked glucose

tight and strong and rigid linkages

forms of starch

homopolysaccharide of glycose

-almylose- linear

-amylopectin- branched

most starch is 10-30% amylase and 70-90% amylopectin

• molecular weight of amylopectin- up to 200 million daltons

• compact helical shape

glycose polymers- storage

amylose- linear alpha 1→4

amylopectin- highly branched, branches occur every 12-30 residues alpha 1→4 linear alpha 1→6 branch points

glycogen

main storage polysaccharide in animals

greatest abundance in liver and muscle cells

similar in structure to amylopectin, except that it has more branch points

1. more compact, an important consideration in mobile animal bodies

2. stored glucose is rapidly mobilized when the animal demands energy’

reducing end- anomeric carbon

cellulose- structural polysaccharide

structural polysaccharides- composition similar to storage polysaccharides, but small structural differences greatly influence properties (b1→4) linkages make al the difference!

more compact- no water molecule sin here

accounts for ove half of the total carbon in plants

tough, water-soluble- provides support and protection

beta 1-4 links allow molecule to stretch out and hydrogen bond with neighboring, parallel polysaccharide strands to form tough fibrils

• insoluble fiber

• most animals cannot use cellulose as a fuel source because they lack the enzyme to hydrolyze beta 1-4 inakges

cell surface polysaccharides

a host of important funtions

• animal cel surfaces contain an incredible diversity of glycosylated proteins- glycoproteins

• polysaccharide structures regulate recognitions (cell-cell interactions, adhesion, stability ect)

• the uniqueness of the information in these structures is determined by the enzymes that synthesize these polysaccharides

glycoprotein

a protein with small oligosaccharides attached

• carb is attached via anomeric carbon to amino acids on protein

  • commonly at threonine, serine, and asparagine from OH and NH

• about half of mammalian proteins are glycoprotiens

• carbs play role in protein-protien recognition

• viral proteins are heavily glycosylated, this helps evade the immune system

defined as proteins that are covalently linked to carbs through N or O linkages

flu targets

hemagglutinin and neuraminidase

glycolipids

lipids w covalently bound oligosaccardie

they are parts of plant and animal cell membranes

in vertebrates, carb composition determines blood groups

lipids

class of biomolecules defined by low solubility in water and high solubility in non polar solvents

• largely hydrocarbon in nature

heath association with low fat diet

fats are an essential part of the human diet, less than 15% of the diet is dangerous

1. promotes stiety

2. carriers of fat-soluble vitamins

3. major source of essential fatty acids- those that cannott be synthesized by the human body

   1. two essential fatty acids for humans alpha-lionlenic acid (omega 3 fatty acid) and linoleum acid (omega 6 fatty acid)

      1. these are important precursors for the EICOSANOIDS

cells use approximately ____ % of their genes to synthesize all of these lipids

5

lipid classification

TAGs, waxes, phospholipids, sphingolipids, glycolipids, eicosanoids, steroids, lipoproteins, fat-soluble, vitamins, glycerophospholibipds, sphingomyelins, cerebrosides, gangliosides, prostaglandins, throboxanes, leukotrienes

divide the various types by function:

1. storage lipids

2. membrane lipids

3. specific biological activities- signals, cofactors, pigments, antioxidants

fatty acids

the simplest lipids are the fatty acids, which are also constituents of many more complex lipds

their basic structure exeplifies the amphipathic lipid model

• a long hydrocarbon chain (tail) and a terminal carboxyl group (head)

carboxylic acids with hydrocarbon (highly reduced) chains containing between 4-36 carbons

almost all natural fatty acids have an even user of carbons

most natural fatty acids are unbranched

saturated vs mono and poly unsaturated

saturated means there are no double bonds

monounsaturated- one double bond

polyunsaturaed0 more than one double bond

fatty acid nomenclature

omega is the carbon at the end so you can count backwards to the first double bond to get omega 3/6

second carbon is alpha carbon (adjacent to carboxylic carbon)

#carbons:#db(delta^where db located)

confirmation of fatty acids

melting points are lower for unsaturated fats

• a saturated chain tends ot adopt extended conformations

• unsaturated fatty acids are slightly more abundant in nature

• the double bonds in natural unsaturated fatty acids are commonly in cis configuration, which kinks the chian

• this prevents close packing and increases flexibility

do free fatty acids exist by themselves

no they are completed with something else always

fatty acid composition of food fats

olive oil, butter, and beef fat consist of mixtures of TAGS, differing in their fatty acid compostion

the melting points of these fats and hence their physical sate at room temperature are a direct function of their fatty acid composition

for exmaple, olive oil has a high proportion of long-chain unsaturated fatty acids which accounts for its liquid state at room temrpature

partial hydrogenation of cooking oils produces trans fatty acids

to improve the shelf life of veggie oils commercial veggie oils are prepped by partial hydrogenation

partial hydrogenation converts unsaturated fat oils to firmer fats which can be used as butter subs

this process converts many of the cis DB to single bonds and increases melting temp of oils

fatty acts occur in large amounts in cells but rarely in a free uncompleted state. what the heck do they complex w ?

in vertebrate animals, free fatty acids circulate in the blood bound to bovine serum albumin

however, fatty acids are present mostly as carboxylic acid derivatives. they are typically esterifed to glycerol or other backbone structures

triacylglycerols (TAGs)

aka triglycerides

• fatty acid esters of glycerol

• three fatty acids each in ester linkage to 1 glycerol

• a major energy source for many organisms

• a typical human stores sufficient calories in fat ot survive for several weeks

• why can fat provide so much energy compared to other energy forms?

  • most reduced form of carbon in nature

  • efficient packing w no salvation needed

other uses for triacylglycerols

waxes

also used as storage and water repellent

esters of long chain saturated and unsaturated fatty acids with long chain al

structural lipids in membranes

contain polar head groups and non polar tains

diversification can from form:

modifying a different backbone

changing fatty acids

modifying head grup

• head groups- determine surface properties of membrane

  • Varys both by organism and cell

membrane bilayer

membranes lipids are amphipathic

in cells, lipids do not pack well into micelles but rather tend to form lipid bilayers

consists of two leaflets of lipid monolayers

• one leaflet faces the cytoplasm

• another leaflet faces the extracellular space or the inside of membrane- enclosed organelle

• a lipid bilayer is typically 5 to 6 nm thick

structural lipids in membrane

1. phospholipds- hydrophobic region attached to polar group byphosphate

2. glycolipids- hydrophobic region attached to polar group (sugar)

3. sterols- rigid system of four fused hydrocarbon rings

phospholipids

1. backbone

   1. glycerol backbone→ glycerophospholipid

   2. sphingosine backbone→phosphosphingolipid

2. fatty acids

   1. glycerol backbone→2 fatty acids at c1 and c2 (usually one saturated and one unsaturated)

   2. sphingosine backbone→ one fatty acid at c2

3. C-3 carbon has a highly polar or charged group attached through phosphodiester bond

glycerophospholiipids

consist of glycerol-3-phospate with fatty acids esterified at the 1 and 2 positions

parent compound- phosphatidic acid

acerbity of polar groups are esterified to the phosphoric acid moeity of the molecule