Biochemistry

7/18/2019 Biochemistry

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Biochemistry



Amino acids Basic units of proteins (monomers)

Contain both carboxylic (-COOH) andamino groups (-NH2)



Amino acids hey can be !"#"$ amino acids"

according to %here the amino group

bonds &f the amino group is attached to the

carbon next to the carboxylic carbon"the amino acid is an a-amino acid' &f it is

attached to carbon next to the a-carbon"the amino acid is a #-amino acid" and soon'





Amino acidsAmphoteric they act both as acids

and bases

&n basic enironment" they hae a basicstructure

&n acidic enironment they hae anacidic structure

At isoelectric point" they hae theamphoteric structure (*%itterion)





Amino acidsHydrophobic amino acids Nonpolar amino acids %ith aliphatic +

groups,



Amino acidsNonpolar amino acids %ith aromatic +

groups



Amino acidsHydrophilic amino acids, olar amino acids,



Amino acids Acidic amino acids



Amino acids Basic amino acids



Amino acids



eptides'roteins.ore amino acids form a peptide

.ore peptides form a protein

An amido lin/age formed bet%een t%oamino acids is called peptide bond.



eptides'roteins eptides can be, dipeptides" tripeptides"

polypeptides

0ome hormones hae a peptidicstructure, &nsulin" Antidiuretic hormone"calcitonin" ACH" etc'

1hen the number of amino acids is oer

2-3" and the structure of thecompound is more complex" than %econsider it a protein



roteins Primary structure se4uence of

amino acids in the protein

hey hae an N-terminal end(containing 5NH2 group) and a C-

terminal end (containing 5COOH group)

1e usually %rite proteins (and peptides6

) from the N-terminal to the C-terminalends6



roteins Secondary structure, α-helix , helical structure in %hich the long

polypeptide chain is %ound around thelong axis' he side chains (+ groups) of the

amino acids extend out of the helicalbac/bone' his conformation of peptidechain has interactions %ithin its chains byhydrogen bonding (7 amino acids in oneturn)' &t is usually found in globin-li/eproteins (ex, Hemoglobin)



β-pleated sheet, sheet-li/e arrangementof the polypeptide chains' he hydrogen

bonds %e found bet%een the ad8acentpolypeptide chains' he polypeptidechains inoled in the pleated sheetstructure can be either parallel orantiparallel' Hydrogen bonds stabili*e the

-pleated sheet' &t is usually found in9ber-li/e proteins" li/e collagen'





Tertiary structure, three dimensionalarrangement of the polypeptide chain'

:i;erent /inds of bonds or interactionsare responsible for the maintenance ofthe tertiary structure' hey includehydrophobic forces" hydrogen bonds"

disul9de bonds" salt bridges" and <ander 1aal forces





Quaternary structure =or complex proteins" %ith multiple

subunits he %ay in %hich three-dimensional

subunits interact to form the completefunctional protein

>x, Hemoglobin





:enaturation of proteins rotein denaturation includes the complete

or partial unfolding of the polypeptide chain"

cleaage of disul9de lin/ages" and brea/ageof noncoalent interactions' :enaturation issometimes reersible' he reersing processis called renaturation.

:enaturating factors, temperature" pH"

pressure >x, boiling an egg



roteinsHolopoteins (only amino acids)

Heteroproteins, Amino acids

rosthetic group (metals" sugars" lipids"phosphoric acid" etc)

>x, Hemoglobin has =e3? as a prosthetic

group



Carbohydrates Cn(H2O)n

Monosaccharides

Disaccharides Polysaccharides.any 5OH groups and a carbonyl group

According to the carbonyl group theyare aldose sugars or etone sugars'



CarbohydratesMonosaccharides, 3"7"@"" etc Carbons in the molecule (triose"

tetrose" pentose" hexose" etc) hey hae asymmetric carbons" %hich are

optically actie" so they form a lot ofstereoisomers6 (2 mirroring isomers are calledenantiomers" 2 stereoisomers %hich are notenantiomers are called diastereoisomers and2 isomers %hich di;er only by one asymmetriccarbon are called epimers)

hey can be D-!orms or "-!orms" according to%hich side is the farthest OH group" a%ay fromthe carbonyl group





&n solution they form a cyclic form,



&n aldohexoses (li/e lucose)" the cyclic structure is formed%hen the hydroxyl group in the 9fth carbon reacts %ith thecarbonyl carbon of the aldehyde group'

he six-membered (hemiacetal) ring formed is called thepyranose ring'&f the cycle has @ members (usually for/etohexoses li/e =ructose)" than it is called a !uranose ring'

he resulting OH group can be on either side of the cycle" sothe resulting cyclic structure can either be an a-(same sideof the cycle) or a #-anomer (opposite side of the cycle)'

&n a4ueous solutions" the a- and #-anomers caninterconert" and the process is termed mutarotation



he saccharides that hae an aldolicgroup can be oxidi*ed by the ollens"

=ehling and Benedict solutions6



:isaccharidesDisaccharides are sugar units containing

t%o monosaccharides lin/ed by a coalent

bond called glycosidic bond. #x$ Maltose (t%o glucoses)

Sucrose (glucose and fructose)

"actose (glucose and galactose)

he hydrolysis of disaccharides gies theircorresponding monosaccharide subunits'





olysaccharides olymers of monosaccharides

>x, Starch =ormed from amylose (-7 lin/ed glucoses" soluble in %ater)

and amylopectin (-7 and - lin/ed glucoses" insoluble in%ater) polymers'

found in plants6

%lycogen similar to the amylopectin (insoluble in %ater)

=ound in animals (stored in muscles and lier" energy source)

&ellulose'-glucoses-people cannot digest them6









DipidsHydrophobic compounds

Esed as energy source" part of cell

membranes" functional lipids (such ashormones)

%o /inds, A (triacylglycerols)

0teroids



A =ormed by esteri9cation of glycerol and

fatty acids and are used mainly as

storage of energy



0teroidsEsed as functional lipids" especially

hormones (corticosteroids" sex

hormones)" but also as structural lipids(part of cell membrane)

he starting compound is cholesterol"from %here all the others are

synthesi*ed in the human body >xtremely important for the human

body6









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Biochemistry