Amino acids proteins and enzymes
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Amino Acids Proteins, and Enzymes. Types of Proteins Amino Acids The Peptide Bond. Types of Proteins. TypeExamples Structuraltendons, cartilage, hair, nails Contractilemuscles Transporthemoglobin Storagemilk Hormonalinsulin, growth hormone Enzymecatalyzes reactions in cells

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Amino Acids Proteins, and Enzymes

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Amino acids proteins and enzymes

Amino Acids Proteins, andEnzymes

Types of Proteins

Amino Acids

The Peptide Bond


Types of proteins

Types of Proteins

TypeExamples

  • Structuraltendons, cartilage, hair, nails

  • Contractilemuscles

  • Transporthemoglobin

  • Storagemilk

  • Hormonalinsulin, growth hormone

  • Enzymecatalyzes reactions in cells

  • Protectionimmune response


Amino acids

Amino Acids

  • Building blocks of proteins

  • Carboxylic acid group

  • Amino group

  • Side group R gives unique characteristics

    Rside chain

    I

    H2N—C —COOH

    I

    H


Examples of amino acids

Examples of Amino Acids

H

I

H2N—C —COOH

I

Hglycine

CH3

I

H2N—C —COOH

I

Halanine


Types of amino acids

Types of Amino Acids

Nonpolar R = H, CH3, alkyl groups, aromatic

O

Polar ll

R = –CH2OH, –CH2SH, –CH2C–NH2,

(polar groups with –O-, -SH, -N-)

Polar/Acidic

R = –CH2COOH, or -COOH

Polar/ Basic

R = –CH2CH2NH2


Essential amino acids

Essential Amino Acids

  • 10 amino acids not synthesized by the body

  • arg, his, ile, leu, lys, met, phe, thr, trp, val

  • Must obtain from the diet

  • All in diary products

  • 1 or more missing in grains

    and vegetables


Amino acids as acids and bases

Amino Acids as Acids and Bases

  • Ionization of the –NH2 and the –COOH group

  • Zwitterion has both a + and – charge

  • Zwitterion is neutral overall

    +

    NH2–CH2–COOHH3N–CH2–COO–

    glycine Zwitterion of glycine


Ph and ionization

pH and ionization

H+OH–

++

H3N–CH2–COOHH3N–CH2–COO–H2N–CH2–COO–

Positive ionzwitterionNegative ion

Low pH neutral pHHigh pH


The peptide bond

The Peptide Bond

Amide bond formed by the –COOH of an amino acid and the –NH2 of the next amino acid

O CH3

+ || + |

NH3–CH2–COH + H3N–CH–COO–

O CH3

+ |||

NH3–CH2–C – N–CH–COO–

| peptide bond

H


Peptides

Peptides

  • Amino acids linked by amide (peptide) bonds

    Gly Lys Phe Arg Ser

    H2N- -COOH

    endPeptide bonds end

    Glycyllysylphenylalanylarginylserine


Amino acids proteins and enzymes1

Amino Acids, Proteins, and Enzymes

Primary and Secondary Structure

Tertiary and Quaternary Structure

Protein Hydrolysis and Denaturation


Primary structure of proteins

Primary Structure of Proteins

The particular sequence of amino acids that is the backbone of a peptide chain or protein

Ala-Leu-Cys-Met


Secondary structure alpha helix

Secondary Structure – Alpha Helix

  • Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape

  • Held by H bonds between the H of –N-H group and the –O of C=O of the fourth amino acid along the chain

  • Looks like a coiled “telephone cord”


Secondary structure beta pleated sheet

Secondary Structure – Beta Pleated Sheet

  • Polypeptide chains are arranged side by side

  • Hydrogen bonds form between chains

  • R groups of extend above and below the sheet

  • Typical of fibrous proteins such as silk


Secondary structure triple helix

Secondary Structure – Triple Helix

  • Three polypeptide chains woven together

  • Glycine, proline, hydroxy proline and hydroxylysine

  • H bonding between –OH groups gives a strong structure

  • Typical of collagen, connective tissue, skin, tendons, and cartilage


Tertiary structure

Tertiary Structure

  • Specific overall shape of a protein

  • Cross links between R groups of amino acids in chain

    disulfide –S–S– +

    ionic –COO– H3N–

    H bonds C=O HO–

    hydrophobic –CH3 H3C–


Globular and fibrous proteins

Globular and Fibrous Proteins

Globular proteins Fibrous proteins

“spherical” shapelong, thin fibers

InsulinHair

HemoglobinWool

Enzymes Skin

AntibodiesNails


Quaternary structure

Quaternary Structure

  • Proteins with two or more chains

  • Example is hemoglobin

    Carries oxygen in blood

    Four polypeptide chains

    Each chain has a heme group to

    bind oxygen


Protein hydrolysis

Protein Hydrolysis

  • Break down of peptide bonds

  • Requires acid or base, water and heat

  • Gives smaller peptides and amino acids

  • Similar to digestion of proteins using enzymes

  • Occurs in cells to provide amino acids to synthesize other proteins and tissues


Hydrolysis of a dipeptide

Hydrolysis of a Dipeptide


Denaturation

Denaturation

Disruption of secondary, tertiary and quaternary protein structure by

heat/organics

Break apart H bonds and disrupt hydrophobic attractions

acids/ bases

Break H bonds between polar R groups and

ionic bonds

heavy metal ions

React with S-S bonds to form solids

agitation

Stretches chains until bonds break


Secondary structure triple helix1

Secondary Structure – Triple Helix

  • Three polypeptide chains woven together

  • Glycine, proline, hydroxy proline and hydroxylysine

  • H bonding between –OH groups gives a strong structure

  • Typical of collagen, connective tissue, skin, tendons, and cartilage


Applications of denaturation

Applications of Denaturation

  • Hard boiling an egg

  • Wiping the skin with alcohol swab for injection

  • Cooking food to destroy E. coli.

  • Heat used to cauterize blood vessels

  • Autoclave sterilizes instruments

  • Milk is heated to make yogurt


Functions of proteins

Functions of Proteins

  • Structure – collagen, keratin,elastin

  • Enzyme – lysozyme, amylase,

  • Transport – hemoglobin, lipoproteins

  • Contractile – actin, myosin, tubulin

  • Hormone – insulin, growth hormone

  • Antibody – IgG,

  • Pigment – melanin, rhodopsin

  • Recognition – CD4, MHC proteins


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