Lectures 11 and 12 NHM 361 PROTEIN
Lectures 11 and 12 NHM 361 PROTEIN NHM 361
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This 3 page Class Notes was uploaded by Vanessa Notetaker on Thursday September 15, 2016. The Class Notes belongs to NHM 361 at University of Alabama - Tuscaloosa taught by Amy Cameron Ellis in Fall 2016. Since its upload, it has received 5 views. For similar materials see Nutritional Biochemistry in Nutrition and Food Sciences at University of Alabama - Tuscaloosa.
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Date Created: 09/15/16
NHM 361 Proteins Amino Acids All proteins are polymers of amino acids + Amino acids contain a ca-bon atom bonded to an amino group(NH ), a 3 carboxylate group(COO ) and a side chain (R) H l + - o NH 3-C—lOO R Different amino acids have different side chains o They can be nonpolar, polar, basic or acidic giving them their unique properties They exist as zwitterions which have a net charge of zero from the positive amino and negative carboxylate cancelling out o The non-ion form does not exist They are called α- amino acids because the amino group is bonded to the alpha carbon Can also act as buffers because the zwitterions give the property of being able to donate or accept hydrogens in solution All amino acids except for glycine (has H as R group) are chiral All amino acids are L-amino acids because the functional group(amino) is on the left Bonding Amino acids are linked together by peptide bonds ( a dehydration synthesis reaction) o Dipeptide- 2 amino acids o Tripeptide- 3 a.a o Polypeptide- Less than or equal to 50 a.a o Protein- Over 50 a.a Amino acid chains typically have a N-terminal residue and a C-terminal residue o N-terminal residue is the end of the peptide chain that has a free amino group(NH ) 3 o C-terminal residue is the end of the peptide chain with a free - carboxylate group(COO ) Amino Acids in the Diet Nonessential amino acids are not required in the diet and can be produced endogenously Essential amino acids MUST be obtained from the diet because the body cannot synthesize them alone o Phenylalanine o Valine o Threonine o Tryptophan o Isoleucine o Methionine o Histidine o Arginine (NOT ESSENTIAL BUT PART OF THE ACRONYM) o Leucine o Lysine Conditionally essential o Not essential under normal conditions but during times of illness or stress they may become essential Complete Protein o Contains all 9 essential amino acids o Animal proteins and soy Complementary Protein o Supplementing a protein with another that may contain essential amino acid that the first lacks o Does not need to be consumed at the same meal o Rice and beans Functions of Proteins in the Body Hormones o Peptide hormones Vasopressin, insulin and glucagon o Amine hormones Made of modified amino acids Epinephrine and norepinephrine Buffers o Can bind or release hydrogen ions thanks to zwitterion Osmotic balance o Plasma proteins like albumin maintains osmotic balance Low albumin leads to high amounts of liquid in interstitial space Enzymes o Proteins that catalyze virtually all the reactions in the body Antibodies/Immunoglobulins o Specialized proteins that recognize and bind to foreign invaders in body Structural proteins o Part of the muscle, skeleton matrix, collagen of skin and keratin of hair, skin and nails Movement o Proteins actin and myosin function to facilitate muscle contraction Storage o Store small molecules of ion o Ferritin stores iron Carrier mediated transport o Embedded in phospholipid bilayer to transport substances in and out of cells Neurotransmitters o Many are derived from amino acids or precursor proteins o Transmit nerve impulses between gaps separating nerve cells Transport proteins Bind to hydrophobic substances for transport in aqueous environments o Cholesterol needs to be bound to LDL and HDL(Low density lipoprotein and high density lipoprotein) Different Levels of Protein Structure Primary o Linear sequence of amino acids Secondary o Folding between single amino acid chain involving hydrogen bonding o α helix or β pleated sheet Tertiary o Complex bending and folding of single polypeptide into 3D shape o Hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic interactions Quaternary o Interactions between two different polypeptide chains to form a functional protein Individual chains are called subunits o Hemoglobin polypeptide chains Reactions Peptide bonds can be broken by hydrolysis reactions Denaturization is the unfolding of the 3D structure of a protein o Occurs due to change in pH or temperature o The change in texture in cooking eggs is due to this o DOES NOT BREAK PEPTIDE BONDS
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