Regents Biology Proteins

Regents Biology Proteins: Multipurpose molecules

Regents Biology Functions of proteins/amino acids: collagen (skin) hemoglobin structural– claws, nails, hair, hooves (keratin), outer layer of skin (collagen)  transport - hemoglobin, cell membrane transport proteins  movement contractile proteins actin & myosin  regulatory - hormones  catalytic – enzymes that speed up reactions allowing them to occur  immunological – antibodies, antigens on the exterior of a cell  storage of amino acids

Regents Biology Proteins  Building block = amino acid amino acid – amino acid – amino acid – amino acid – —N——N— H H H | —C— | C—OH || O variable group amino acids  20 different amino acids

Regents Biology H H NCC OH O H R amino group carboxyl group R group General structure of an amino acid (basic) (acidic)

Regents Biology You do NOT need to know their names! There are 20 amino acids naturally incorporated into proteins Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic acid Glutamine Glycine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tryptophan Tyrosine Valine

Regents Biology Other amino acids do exist… CH 2 H H NCC OH O H O I I II Thyroxine: used in the human body as a hormone to regulate metabolic rate …but are not normally found in proteins

Regents Biology Humans can synthesis some amino acids by altering other amino acids, however… …some amino acids cannot be synthesised and are therefore needed in the diet. These are the essential amino acids Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine

Regents Biology

Phenylketonuria or Maple Syrup Urine Disease Patients lack the enzyme phenylalanine hydroxylase – needed to dispose of the amino acid phenylalanine properly Penylalanine rapidly builds up in the blood stream - it converted to unusual metabolites which give the patient’s urine a characteristic smell - it also rapidly causes brain damage! Treatment:A diet low in phelylalanine No meat, fish, poultry, eggs, cheese, milk, beans, or peas

Regents Biology Water-fearing amino acids  Hydrophobic  “water fearing” amino acids  try to get away from water in cell  the protein folds

Regents Biology Different amino acids have different R groups Their different properties depend on their R groups Hydrophobic (‘Water-hating’) R groups CH 3 H H NCC OH O H alanine CH 2 H H NCC OH O H phenylalanine (aromatic)

Regents Biology Water-loving amino acids  Hydrophillic  “water loving” amino acids  try to stay in water in cell  the protein folds

Regents Biology Hydrophillic (‘Water-loving’) R groups CH 2 H H NCC OH O H SH cysteine CH 2 H H NCC OH O H serine

Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer  Each amino acid is different  some “like” water & dissolve in it  some “fear” water & separate from it amino acid

Regents Biology Formation of a dipeptide: carboxyl group of one amino acid reacts with amino group of second amino acid H2OH2O water molecule formed H H NCC OH O H R2R2 H H NCC O H R1R1 H H NCC O H R1R1 H NCC O H R2R2 peptide linkage a dipeptide

Regents Biology H H NCC OH O H R1R1 H H NCC O H R2R2 H H NCC O H R1R1 H NCC O H R2R2 H2OH2O Formation of a dipeptide produces a molecule of water, therefore… …this is a condensation reaction 2 amino acids  dipeptide + water

Regents Biology H H NCC OH O H R1R1 H H NCC O H R2R2 H H NCC O H R1R1 H NCC O H R2R2 H2OH2O Splitting a dipeptide to form two amino acids consumes one molecule of water, therefore… …this is a hydrolysis reaction dipeptide + water  2 amino acids

Regents Biology pepsin 3-D protein structure collagen  Proteins fold & twist into 3-D shape  that’s what happens in the cell! hemoglobin growth hormone

Regents Biology Its shape that matters!  Proteins do their jobs, because of their shape  Unfolding a protein destroys its shape  wrong shape = can’t do its job  unfolding proteins = “denature”  temperature  pH (acidity) folded unfolded “denatured”

Regents Biology Let’s eat some Proteins!