PROTEINS Q1

Enzymatic proteins

Catalyze (speed up) chemical reactions; enzymes catalyze hydrolysis of bonds in food molecules during digestion

Defensive proteins

Antibodies (immunoglobulins), Y-shaped; recognize and inactivate/destroy pathogens (virus, bacteria, fungi, parasites)

Storage proteins

Store amino acids for later use; casein (milk) = amino acid source for mammals, ovalbumin (egg white) = amino acid source for developing embryo

Transport proteins

Move substances around the body; hemoglobin carries O2 in blood, membrane channels/carriers move molecules across the cell membrane

Hormonal proteins

Coordinate body activities; insulin (from pancreas) signals tissues to take up glucose, lowering blood sugar

Receptor proteins

Detect chemical stimuli; found on nerve cells, bind signaling molecules released by other neurons at the synapse

Structural proteins

Provide support; keratin (hair), silk (insects), collagen (connective tissue)

Contractile/motor proteins

Cause movement; actin + myosin in muscle contraction, also drive cilia/flagella movement

Protein

Macromolecule made of amino acids linked by peptide bonds;

Protein g/mol

MW 6,000–1,000,000 g/mol; contains C, H, O, N

Amino acid structure

Has an amino group, carboxyl group, alpha carbon, and R group (side chain); R group determines the protein's unique chemical property and how it folds/functions

Essential amino acids

9 of the 20; body cannot produce them, must come from diet

Non-essential amino acids

11 of the 20; body can synthesize these on its own

Peptide bond vs polypeptide

One bond = peptide bond; chain of many = polypeptide

Primary structure

Linear sequence of amino acids

Secondary structure

Zigzag/coiled folding pattern (e.g. alpha helix, beta sheet) from hydrogen bonding

Tertiary structure

Full 3D folding into a globular shape

Quaternary structure

Two or more polypeptide chains joined together

Globular vs fibrous proteins

Globular = compact, rounded, usually functional (enzymes, antibodies); fibrous = elongated strands, usually structural (collagen, keratin)