PROTEINS - y9sci.files.wordpress.com · Proteins are complex biomolecules that contain amino acids...

PROTEINS

Proteins are complex biomolecules that

contain amino acids linked through

peptide bonds.

Molecular weight : 6,000 to over 1,000,000

Considered as the most versatile biomolecules

Serve numerous essential functions in biological

processes

Primary constituents of living organisms

Contain NITROGEN (N) aside from C, H and O

Foods rich in proteins: animal meat, tuna, cheese,

tofu, beans

Proteins are complex biomolecules

that contain amino acids linked

through peptide bonds.

derived from the Greek word “Proteios” – of first importance

Two Major Types of Proteins:

1) Fibrous proteins (collagen, actin, keratin)

- insoluble in water; main components of the body

2) Globular proteins (albumin, hemoglobin, and

immunoglobulins)

- soluble in water; used for the other non-structural

purposes of proteins.

Proteins play a wide variety of functional

roles.

STRUCTURE: form the scaffolding that gives animal cells their shape. (skin, bones, hair, nails); Collagen & Keratin

HORMONES: Insulin helps cells absorb glucose from the blood & helps the body from using fat as a source of energy

TRANSPORT: Hemoglobin; involve in the transport of molecules across cell membranes

Proteins play a wide variety of

functional roles.

STORAGE: Casein (milk) stores nutrients for newborn mammalsFerritin, blood cell protein in the liver, stores iron

CATALYST: Enzymes (protein that speeds up all the reactionthat take place in organisms)

PROTECTION: antibodies to counteract & fight disease ; Fibrinogen = facilitates blood clotting

Proteins play a wide variety of functional

roles.

MOVEMENT: protein in muscles (myosin & actin) –

muscle contraction and relaxation

REGULATION: control & regulate the kind of protein

synthesized in a particular cell but also dictate the

time this should occur

Amino acids are the building blocks of

protein.

Composition: Central C bonded

to H, a carboxyl group (-

COOH), an amino group (-NH2)

and a side chain (R group)

Total amino acids: 20

The R group is the one that is

variable among the 20 amino

acids.

THE TWENTY AMINO ACIDS (*essential cannot be produced by the body)

Amino Acid Abbreviatio

ns

Side chain/R group Linear Formula

Alanine Ala A CH3-CH(NH2)-COOH

*Arginine(essential amino

acid)

Arg R HN=C(NH2)-NH-

(CH2)3-CH(NH2)-COOH

*Asparagine(essential amino

acid)

Asn N H2N-CO-CH2-CH(NH2)-COOH

Source: http://www.imgt.org/IMGTeducation/Aide-memoire/_UK/aminoacids/formuleAA/#formula

THE TWENTY AMINO ACIDS


ns


Aspartic

acid

Asp D HOOC-CH2-

CH(NH2)-COOH

Cysteine Cys C HS-CH2-CH(NH2)-

COOH

Glutamine Gln Q H2N-CO-(CH2)2-

CH(NH2)-COOH




ns


Glutamic

acid

Glu E HOOC-(CH2)2-CH(NH2)-COOH

Glycine Gly G NH2-CH2-COOH

*Histidine(essential amino

acid)

His H NH-CH=N-CH=C-

CH2-CH(NH2)-COOH




ns


*Isoleucine(essential amino

acid)

Ile I CH3-CH2-CH(CH3)-CH(NH2)-COOH

*Leucine(essential amino

acid)

Leu L (CH3)2-CH-CH2-CH(NH2)-COOH

*Lysine(essential amino

acid)

Lys K H2N-(CH2)4-CH(NH2)-COOH




ns


*Methionine(essential amino

acid)

Met M CH3-S-(CH2)2-

CH(NH2)-COOH

*Phenylalani

ne

(essential

amino acid)

Ph

e

F Ph-CH2-CH(NH2)-

COOH

Proline Pro P NH-(CH2)3-CH-

COOH




ns


Serine Ser S HO-CH2-CH(NH2)-

COOH

*Threonin

e(essential amino

acid)

Thr T CH3-CH(OH)-

CH(NH2)-COOH

Tyrptophan(essential amino

acid)

Trp W Ph-NH-CH=C-CH2-

CH(NH2)-COOH




ns


Tyrosine Tyr Y HO-Ph-CH2-CH(NH2)-COOH

*Valine(essential amino

acid)

Val V (CH3)2-CH-CH(NH2)-COOH


Proteins have four levels of

structure.

Depends on the sequence of the amino acids

According to complexity: Primary, Secondary, Tertiary & Quaternary


structure.


structure.

PRIMARY Structure

Linear sequence of amino

acids

Refers to the arrangement

or order of amino acids in

the protein chain


structure.

DIPEPTIDE

Formed when two amino acids combine through a condensation reaction

Proteins have four

levels of structure.

SECONDARY Structure

Refers to the spatial arrangement of the polypeptide chain of a protein

2 types: Alpha Helix & Beta Pleated Sheets


structure.

SECONDARY Structure

Alpha Helix = held

together by H bonds

between loops of a coil

Beta Pleated Sheets =

chains held together by

H bonds between

adjacent chains


structure.

TERTIARY Structure

Refers to the FINAL three-

dimensional shape of a

single polypeptide

molecule where the alpha

helix and the pleated

sheet are folded forming a

GLOBULAR PROTEIN.


structure.

TERTIARY Structure

Types of

INTERmolecular bonds:

H-bond, Dipole-dipole,

and London dispersion

Types of

INTRAmolecular

bonds: ionic &

covalent (disulphide

bond)


structure.

QUARTERNARY Structure

Contains more than one chain

Refers to the overall shape when 2 or more polypeptides bind each other

Results in the classification of proteins: fibrous, globular, or conjugated

Ex: Hemoglobin

Proteins denaturation involves the disruption and

possible destruction of the secondary and tertiary

structures of protein.

Proteins denaturation can be caused by several

factors.

pH changes – alter the IM; some functional groups of amino acids lose or gain electrostatic charge which affects the formation of bonds

Increase in Temperature –disrupt H bonds & nonpolar hydrophobic interactions

Proteins denaturation can be caused by several

factors.

Addition of various chemicals – destroy

the natural structure of

a protein

Ex. Addition of Urea (forms

H bonds with different

parts of the protein s

such as peptide groups

causing the weakening

of IMF)

PROTEINS

are made up of

AMINO ACIDS

Structural

Levels:

Primary

Secondary

Tertiary

Quarternary

May be denatured through:

pH changes

Temperature changes

Addition of Chemicals

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