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Lecture 5

Amino Acids (week 5).docx

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Health Studies
HLTH 230
Jeffery Lalonde

Protein: Amino Acids  Usually associated with strength and muscle o Muscle cells need physical activity and many nutrients  Not only protein  Protein have structional and functional roles in cells o Focusing on protein foods can cause a lack of other essential foods in the diet  Excess meat results in high saturated fat intakes  Protein can also be found in milk, eggs, legumes, and whole grains Protein Chemistry  Contain the same atoms as carbohydrates and fats o Carbon o Hydrogen o Oxygen  Protein also contain o Nitrogen Amino Acids  Means containing nitrogen o Amino acids are the links in the protein chain  Amino acids have the same basic structure o Carbon centre  Hydrogen  Amino group  Acid group  Plus a unique side chain  Side groups on each amino acid vary from one amino acid to another  Side groups make proteins more complicated than lipids are carbohydrates  Simplest amino acid is glycine o Has hydrogen atom as a side group  Amino acids o Same structures  Different in o Size o Shape o Electrical charge Non Essential Amino Acids  Made in the body with o Nitrogen  Forms an amino group o Fragments from Carbs and Fats  Form the rest of the structure  Proteins from foods supply these amino acids Essential Amino Acids  Cannot be made in the body  Must be supplied by the diet o 9 essential amino acids  –Histidine  –Isoleucine  –Leucine  –Lysine  –Methionine  –Phenylalanine  –Threonine  –Tryptophan  –Valine  HILL, MPh, TTV  Non Essential Amino Acids o –Alanine o –Arginine o –Asparagine o –Aspartic acid o –Cysteine o –Glutamic acid o –Glutamine o –Glycine o –Proline o –Serine o –Tyrosine  AAAA,CGGG, ProSerTy Conditionally Essential Amino Acids  A non essential amino acid becomes essential when the need for it is beyond the body’s ability to produce it o Eg. Tyrosine  Those with PKU cannot use phenylalanine to make tyrosine Proteins  Peptide bonds o Amino acids are connected by condensation reactions  Dipeptide o 2 amino acids bonded together  Tripeptide o 3 amino acids bonded together  Polypeptide o A chain of many amino acids bonded together Protein Chain Length  A few dozen to several hundred amino acids long  Primary Structure – Sequences o Diverse, 20 different amino acids o Can have several polypeptide chains  Polypeptide Shapes – Secondary Structure o Determined by electrical attractions within the chain o Positively charged hydrogens attract negative oxygens o Chain may twist or fold giving proteins strength and stability  Polypeptide Tangles – Tertiary Structure o Polypeptide chains twist and fold into tangled shapes o Side groups may attract or repel each other  Side groups can be hydrophilic or hydrophobic  Chains fold that so that hydrophilic groups are near water  Hydrophobic side groups are hidden in the middle o Disulfide bridges also determine tertiary structure o Different shape, different characteristics  Spherical structure can carry materials  Linear structures form tendons o Multiple Polypeptide Interactions – Quaternary Structures  Interactions between 2 or more polypeptides  Some polypeptides work together in large complexes  Hemoglobin  Four polypeptide chains Insulin  Small protein with 51 amino acids  2 polypeptide chains o Polypeptides are joined by 2 disulfide bridges o Bonds between sulfur o One chain is joined to itself by a disulphide bridge  Must be injected, not swallowed o Acid in the stomach would change shape and function of insulin  Denaturation  Change in a proteins shape and loss of its function  Brought by heat, acid, base, or other agents  Eg, eggs while heated, milk and acid  In the body, proteins are denatured by stomach acid Digestion and Absorption of Protein  Dietary proteins do not directly become proteins o Dietary proteins supply amino acids for the body to make proteins  Polypeptides are broken by enzymes into shorter strands o Then broken down into amino acids  Mouth o Little protein digestion o Foods are broken down and moistened to be swallowed  Stomach o Partial breakdown  Hydrolysis o Hydrochloric acid  Denatures peptide strands allowing enzymes to access peptide bonds  Concerts pepsinogen into pepsin, active form  Pepsin breaks down polypeptides into smaller pieces  Pepsinogen, proenzyme, zymogen o Inactive form of an enzyme  Small intestine o Pancreatic and intestinal juices act on polypeptide chains  Polypeptides are hydrolyzed into short peptide chains, tripeptides,dipeptides, and amino acids o Peptidase enzymes  Membrane surface of intestine  Split most tripeptides and dipeptides into single amino acids  Proteases are enzymes that hydrolyze protein  Absorption o Amino acids, dipeptides and tripeptides are transported by carriers into intestinal cells  Inside intestinal cells amino acids may be used for energy  Or used to make other compounds o Amino acids that are not used in the intestinal cells enter capillaries and are transported to the liver Misconceptions  Enzymes will not digest your cells o Enzymes gets digested when they leave the stable PH of their environment  Amino acids are supplements are not better than protein o Amino acid supplements prevent the body from overworking o The body can easily handle the break down of protein o Amino can overwhelm a transporter and prevent over amino acids from being picked up Protein Synthesis (formation)  Protein is made through o Transcription  Instructions to make proteins o Translation  Specifying sequence of amino acids  Sequencing Errior o Sequence determines shape  Shape determines function  Miscopied protein can alter function  Eg. Sickle cell anemia  Hemoglobin has valine instead of glutamic acid  Red blood cells with abnormal hemoglobin become crescent shaped instead of disk shaped Roles of Protein  Structural Materials o Form building blocks of muscle, blood, skin o Proteins are needed for replacement of cells  Matrix o Basic substance that gives form to a developing structure  Collagen o Protein from which connective tissues are made  Prives material for ligaments and tendons  Strengthen arteries  Holds tissue together in scars  Enzymes o Proteins that create chemical reactions, but do not change in the process o “minister in a wedding”  Hormones o Elicited from glands o Response to altered conditions to act on a target issue o Elicit a specific response  Some hormones are proteins  Rise in blood glucose  Insulin is released from the pancreas  Stimulates glucose to enter cells  Regulators of Fluid Balance o Help to maintain body’s fluid blanace  Body fluids are contained both inside and outside the cell  Extracellular fluid can be found within blood vesels or between cells  Interstitial – between cells Intravascular – within blood cells  Normal fluid Balance o Fluids and other materials are exchanged betwens the cells and blood o Proteins are large and cannot pass freely across capillary walls  Remain in the cells and plasma  Some plasma proteins do leak out of the plasma into  Interstitial and intercellular fluid  Abnormal Fluid Balance o Illness, protein malnurtrition o Plasma proteins leaking out of blood vessels o Proteins attract water o Causes swelling  Edema  Excessive protein losses, inflammation  Inadequate protein  With inadequate consumption of protein, concentration of proteins in the bloodstream drops below normal  Excess fluids build up in surround tissues  Not enough protein in the blood to counteract  Acid Base Regulators o Acid – many hydrogen ions o Normal body process produce acids and based that get carried to kidneys and lungs, then get excreted o Proteins have negative charges on their surface o Therefore attract hydrogen (acidic) overall decreasing acidity o By accepting and releasing hydrogen atoms, proteins maintain acid base balance  Blood acidity is tightly controlled  Extremes  Acidosis or alkalosis  Transporters o Proteins can carry nutrients and other molecules around the body o Proteins can act as pumps  Hemoglobin carries oxygen  Lipoproteins transport lipids around the body  Antibodies o Proteins defend against disease o Without enough protein the body cannot make antibodies to fight against disease  Antibodies  Large protein molecules produced by the immune system  A response to invasion of foreign invaders  Energy Source and Glucose o Proteins can be sacrificed for energy if inadequate calo
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