BIOLOGY 12 - Proteins
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]
