BIOLOGY 12 - Proteins

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Denaturation and what causes it?

A protein has lost normal shape (function) because r-group bonding is disturbed, - heating - change in pH - heavy metals added

Polypeptides

Chains of amino acids (proteins are made up of one or more polypeptide molecules)

Protein

Large, complex organic macromolecules that are composed of amino acids

Amino Acid

Monomer of protein: - There are 20 types - 11 can be made by your body, 9 must be ingested

Tertiary structure

bonding (ionic, covalent, polar covalent) between R-groups makes the helix bend and twist into "globs" of protein of various shapes. This shape determines the function of the protein

General Structure of an amino acid

carboxyl group, 2 carbons, amino group and a variable group (r group) ---- C - C - N backbone

Formation of polypeptides

dehydration synthesis between the H on the amino group of the OH on a carboxyl group. - one peptide bond (polar covalent) is a dipeptide, multiple bonds are polypeptides

Quaternary structure

some proteins are made of more than one polypeptide chain which arrange themselves together based on their r-group interactions

Of critical importance to the eventual shape/function of the protein (tertiary)?

the original sequence

Primary structure

the sequence of amino acids joined in a line

Secondary structure

- since there are polar peptide bonds, hydrogen bonding occurs between amino acids - often the chain coils up into an alpha helix (a-helix) or folds into a beta-pleated sheet (B-sheet)

4 levels of protein organization

1) Primary 2) Secondary 3) Tertiary 4) Quarternary

3 main functions of proteins

1) Structural Support - cytoskeleton, elastin, collagen in cartilage and bone 2) Movement - actin/myosin in muscle cells - cilia, flagella 3) Metabollic Functions i) enzymes - biological catalysts ii) transport - carriers and channels across cell membrane, hemoglobin transports o2 iii) antibodies - fighting infection iv) hormones - maintain homeostasis

3 interactions within polypeptides

1) hydrogen bonds with the backbone 2) electrostatic interactions between R Groups - attraction/ repulsion between + and - 3) covalent, polar covalent and ionic bonding between R Groups [because of these interactions, a polypeptide can take on complex shapes]


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