Proteins B1.2

Protein

A macromolecule made from one or more polypeptide chains folded into a specific three dimensional shape

• Macromolecule: a very large molecule made up of thousands of atoms, usually formed by joining smaller building blocks called monomers

What is an amino acid? What three components is it composed of?

An amino acid is the monomer that makes up proteins; it contains an amino group a carboxyl group a hydrogen atom and a variable R group attached to a central carbon

What is a polypeptide?

A polypeptide is a chain of amino acids joined together by peptide bonds

Peptide bond

A covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid during a condensation reaction

Carboxyl group

A functional group containing carbon oxygen and hydrogen written as COOH

Amino group

A functional group containing nitrogen and hydrogen written as NH2

R group

The variable side chain of an amino acid that determines its chemical properties

Dipeptide

A molecule made from two amino acids joined by one peptide bond

How many amino acids can our body make?

The human body can synthesize 11 of the 20 standard amino acids

How many amino acids do we need from our diet?

Humans need to obtain 9 essential amino acids from their diet because the body cannot synthesize enough of them

Tripeptide

A molecule made from three amino acids joined together by two peptide bonds

Haemoglobin

A globular protein in red blood cells that transports oxygen

Keratin

A fibrous structural protein found in structures such as hair skin and nails

Lipase

An enzyme that catalyses the breakdown of lipids into smaller molecules

• biological catalysts—usually proteins—that speed up specific chemical reactions in living cells without being used up or changed in the process

Collagen

A fibrous structural protein that provides strength and support in connective tissues

Histones

Proteins around which DNA wraps to form nucleosomes.

Highly alkaline proteins that package and order DNA into structural units called nucleosomes.

Insulin

A protein hormone that helps regulate blood glucose concentration

Protein structure

The organization of a protein at primary secondary tertiary and quaternary levels

Primary structure °1

The specific sequence of amino acids in a polypeptide chain joined by peptide bonds

Secondary structure °2

The local folding of a polypeptide chain into structures such as alpha helices and beta pleated sheets

Alpha helix

A secondary protein structure in which the polypeptide chain forms a coiled shape stabilized mainly by hydrogen bonds

Beta pleated sheet

A secondary protein structure in which sections of a polypeptide chain form folded sheets stabilized mainly by hydrogen bonds

Tertiary structure °3

The overall three dimensional folding of a single polypeptide chain caused by interactions between R groups

Quaternary structure °4

The structure formed when two or more polypeptide chains associate to form one functional protein

Intermolecular forces

Forces of attraction between separate molecules that can influence the structure and properties of substances

Globular protein

A protein with a compact roughly spherical shape that is often soluble in water and performs roles such as transport regulation or catalysis

Fibrous protein

A protein with a long or extended structure that often provides strength and support

Exothermic

A reaction that releases energy to the surroundings usually as heat

Endothermic

A reaction that absorbs energy from the surroundings

Neutralization

A reaction between an acid and a base that produces a salt and usually water

Essential amino acids

Amino acids that humans cannot synthesize in sufficient amounts and therefore need to obtain from their diet

Nonessential amino acids

Amino acids that the human body can synthesize in sufficient amounts

Polar amino acid

An amino acid whose side chain has an uneven distribution of electrical charge and can interact with water

Nonpolar amino acid

An amino acid whose side chain does not have a significant electrical charge and generally does not interact strongly with water

Positively charged amino acid

An amino acid whose side chain has a positive charge at approximately neutral pH

Negatively charged amino acid

An amino acid whose side chain has a negative charge at approximately neutral pH

Alanine Ala

Nonpolar; the side chain is a small methyl group

Arginine Arg

Positively charged; the side chain contains a basic amino group

Asparagine Asn

Polar uncharged; the side chain contains an amide group

Aspartic acid Asp

Negatively charged; the side chain contains a carboxyl group

Cysteine Cys

Polar uncharged; the side chain contains a sulfur containing thiol group and can form disulfide bonds

Glutamic acid Glu

Negatively charged; the side chain contains a carboxyl group

Glutamine Gln

Polar uncharged; the side chain contains an amide group

Glycine Gly

Nonpolar; the side chain is a hydrogen atom

Histidine His

Polar and can become positively charged; its side chain contains a nitrogen containing ring

Isoleucine Ile

Nonpolar; the side chain is a branched hydrocarbon chain

Leucine Leu

Nonpolar; the side chain is a branched hydrocarbon chain

Lysine Lys

Positively charged; the side chain contains a basic amino group

Methionine Met

Nonpolar; the side chain contains sulfur within a hydrocarbon chain

Phenylalanine Phe

Nonpolar; the side chain contains an aromatic ring

Proline Pro

Nonpolar; the side chain forms a ring with the amino group and creates bends in polypeptide chains

Serine Ser

Polar uncharged; the side chain contains a hydroxyl group

Threonine Thr

Polar uncharged; the side chain contains a hydroxyl group

Tryptophan Trp

Nonpolar; the side chain contains a large aromatic ring system

Tyrosine Tyr

Polar uncharged; the side chain contains an aromatic ring and a hydroxyl group

Valine Val

Nonpolar; the side chain is a branched hydrocarbon chain