[BIOCHEM} Peptides & Proteins

Peptides and proteins

polymers of amino acids joined by peptide bonds

Peptide Bonds

a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O)

Amide Bond

other term for Peptide bond

Peptide bonds

covalent bonds between amino acids in a peptide

Amino Acid

is covalently linked together by the formation of an amide bond between a-carboxyl group of one amino acid with another a-amino group of another amino acid

Left to Right

direction of how Peptide Sequences are written

-COO

carboxyl group

NH3+

Amino group

Dipeptide

peptide that consists of 2 amino acids

Dehydration Reaction

the process of removing or loss of water from the molecule or ion

Peptide

has a lower molecular weight compared to protein

Peptide

consist less than 50 amino acids

Protein

molecules with more than 50 amino acids

Protein

consist of one or more polypeptide chains

Protein

is the heaviest among peptides, oligopeptides, and polypeptides

Oligopeptide

a polymer consisting of 2 to 10 amino acids (less than 10 and around 2)

Tripeptide

peptide that has 3 amino acids

Polypeptides

peptide that have more than 10 amino acid residues (more than 10, below 50)

9

# of amino acids of Oxytocin

9

# of amino acids of Vasopressin

51

# of amino acids of Insulin

84

# of amino acids of Parathyroid hormone

Oxytocin

hormone secreted by the posterior pituitary gland; stimulates contractions of the uterus and ejection of milk

Altruistic behavior

selflessness characteristic of an individual

Vasopressin

- responsible in the regulation/control of blood pressure and blood volume

Vasopressin

hormone that stimulates the kidneys to retain water when a person is dehydrated

Insulin

hormone that facilitates entry into insulin-sensitive cells

Parathyroid hormone

hormone that functions in regulating blood calcium levels

Enkephalins

- are pentapeptides neurotransmitters produced by the brain
- responsible for binding receptor sites in the brain to reduce pain

Met-enkephalin & Leu-enkephalin

best known Enkephalins

Glutathione

is significant for its antioxidant property

Antioxidant

are substances that protect the cells against free radicals

Glu-Cys-Gly

the tripeptide present in high levels of most cells

Proteins

most important out of all biological compounds

Proteios

greek word for protein; meaning "of first importance"

400-500

# of amino acid residues in common proteins

40-100

# of amino acid residues in small proteins

Monomeric

a protein that contains one polypeptide chain

Multimeric

a protein that contains two or more polypeptide chains

Simple proteins

proteins that are entirely made up of Amino acids only

Albumin

protein that is soluble in water; soluble in diluted aqueous salt sol'n and heat coagulable

Globulin

protein that is insoluble in water, soluble in aqueous salt solution, and heat coagulable

Glutelin

protein that is soluble in dilute acid and alkalies and is heat coagulable

Prolamine

an alcohol soluble protein

Albuminoid or Scleroprotein

the least soluble protein

Protamine

- the simplest and basic protein, is soluble and dilute ammonia, acid, and alkali
- is found in spermatozoa

Histone

- basic protein and is soluble and very dilute acid
- found in combination with DNA

Conjugated Proteins

proteins that are made up of amino acids and other substances

Prosthetic Group

other term for Conjugated proteins

Nucleic Acid

prosthetic group of Nucleoprotein

Carbohydrates

prosthetic group of Glycoprotein

Phosphoric acid residues

prosthetic group of Phosphoprotein

Chromoprotein

the prosthetic group that gives color

Lipid

prosthetic group of Lipoprotein

Metals or Minerals

prosthetic group of Metalloprotein

Derived Proteins

the degradation products obtained by the hydrolysis of natural proteins with acids, alkalis, and enzymes

Primary Derived

proteins derived from simple or conjugated proteins by physical or chemical means

Denatured Protein

other term for Primary derived protein

Secondary Derived

protein formed through progressive hydrolytic product of protein hydrolysis

Protein Hydrolysis

aims to break down the peptide bonds and to increase the free amino acid and carboxyl groups

Fibrous Proteins

proteins that are
- elongated, asymmetrical
- tough
- insoluble in water
- arranged around a single axis to form a fiber
- involved in structural functions

Collagen

most abundant fibrous protein in the human body (25%)

Keratin

a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair, feathers, nails

Globular Proteins

proteins that are
- circular and symmetrical
- involved in mobile and dynamic functions
- soluble in water
- for transport purposes (MAIN PURPOSE)

Primary Protein Structure

describes the linear sequence of amino acids in the polypeptide chain

Secondary Protein Structure

- localized regional structure of a protein
- formed due to the hydrogen bonds between peptide bonds

Tertiary Protein Structure

protein structure that shows the overall shape of the protein

Quaternary Protein Structure

protein structure that shows the interactions between proteins

Primary Protein Structure

Secondary Protein Structure

Tertiary Protein Structure

Quaternary Protein Structure

20^n

the number of peptides possible for a chain of n amino acid

20

# of peptides for each amino acid

Leu, Ala, Gly, Ser, Val, Glu

most abundant amino acids in proteins

Trp, Cys, Met, His

rarest amino acids in proteins

Pauling & Corey

first one to proposed the 2 secondary structures of protein:
~ alpha-helix
~ beta-sheet

Alpha Helix

~ rod-like structure (phone cord)
~ amino acid R groups extend OUTWARD from the helix
~ main chain atoms on the INSIDE
~ helices can be right or left-handed

Beta-Pleated Sheet

~ second most commonly occurring secondary structure of protein
~ R groups lie ABOVE/BELOW the zigzagging planes of the pleated sheet and are nearly PERPENDICULAR to them

Antiparallel beta-sheet

- neighboring H-bonded polypeptide chains run in OPPOSITE DIRECTION
- more stable
- 2 linear polymers of AA run in opposite direction

Parallel beta-sheets

~ H-bonded extend in the SAME DIRECTION
~ the adjacent strands run in the SAME DIRECTION

Tertiary Protein Structure

- results from the interactions between amino acid side chains ( R grps) that are widely separated from each other
- have WATER-SOLUBLE proteins fold into compact structures with NONPOLAR CORES

Quaternary Protein Structure

- highest level of protein organization
- polypeptide chains (subunits) maybe identical or different

Dimer

protein structure that consist of 2 polypeptide chains/subunits

Trimer

a polymer consisting of 3 polypeptide chains

Tetramers

a polymer consisting of 4 polypeptide chains

Pentamer

a polymer consisting of 5 polypeptide chains

Protein Folding

- process by which a protein structure assumes its functional shape or conformation
- a process where a protein chain acquires its 3-dimensional structure

Chaperones

assist in preventing the protein from associating to inappropriate molecules

Denaturation

the process of destroying the native conformation of a protein by chemical or physical means

Gly

Glycine

G

Glycine

Ala

Alanine

A

Alanine

Val

Valine

V

Valine

Leu

Leucine

L

Leucine

Ile

Isoleucine

I

Isoleucine