ESS 3 Lecture Notes - Lecture 5: Enzyme, Red Meat, Carbohydrate
Protein
Protein is an essential, energy-yielding macronutrient
➔Needs to be supplied through the diet
➔Yields calories
➔Needed in large amounts
➔Contains nitrogen, carbon, hydrogen, oxygen
Recommended DIetary Allowance (RDA)
➔primarily calculated based on body weight
➔0.8 g/kg of body weight for adults
◆154 lb divided by 2.2 lb/kg = 70kg
◆70kg x 0.8 g/kg = 56g of protein/day
➔Most Americans exceed their RDA for protein
◆Average
● Men: 100g
● Women: 70g
◆RDA
● Men: 56g
● Women: 46g
➔Acceptable macronutrient distribution range (AMDR)
◆10% - 35%
◆50 - 175g for 2000 calorie diet
➔More than 60% of protein consumed comes from animal products
◆Greater percentage of saturated fat
Roles of protein in the body
➔Critical functions
◆Antibodies: viruses and bacteria
◆Fluid balance: regulating distribution of fluids
◆Acid-base balance
◆Structure and movement
◆Transporter: chylomicron
◆Hormone and regulation: regulate bodily processes
➔Structural material
◆Muscle, bone, hair, skin, fingernails
➔Growth, maintenance, and repair
➔Energy source
Amino acids
➔Building blocks of protein
➔20 amino acids in the body
◆9 essential that must be supplied by the diet
◆11 non-essential that the body can synthesize
◆Varying proportions and sequences
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➔Unique characteristic: nitrogen attached
➔Linked together by peptide bonds
◆Dipeptides (2 amino acids)
● Condensation of 2 amino acids to form a dipeptide
◆Tripeptides (3 amino acids)
◆Polypeptides (many amino acids)
The shape of proteins determines their function
➔After translation, amino acid chains fold into a particular shape
➔Sequencing errors
◆Results in an altered protein and dysfunction
◆Sickle cell anemia: two of the four hemoglobin polypeptide chains have normal
sequence but the other two do not
● Hemoglobin loses its ability to carry oxygen
● Depressed immune system
➔Denaturation: alters shape and function of proteins to bind to enzymes
◆Caused by heat, light, change in pH, alcohol
◆Important in the digestion of protein
Digestion
Protein digestion in the GI Tract
➔Denatured by hydrochloric acid
➔Pepsin activated to break proteins into single amino acids
➔Proteases are secreted to digest polypeptides
➔Amino acids are transported in the liver and sent to cells
Protein absorption
➔Transport into intestinal cells
◆Uses of amino acids by intestinal cells
➔Unused amino acids transported to liver
➔Enzyme digested
➔Predigested proteins
Protein turnover: Proteins in the body are constantly being broken down and reassembled
➔Can be used as a source of energy to produce glucose and fat
◆Amino acids used for these purposes must be replaced by dietary proteins
◆Risk of entering catabolic state
Energy uses
Amino acids are chemically altered to produce many important compounds
➔Used for protein synthesis
➔Synthesized into glucose or fat
➔Metabolized as a source of energy
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Document Summary
Needs to be supplied through the diet. 0. 8 g/kg of body weight for adults. 154 lb divided by 2. 2 lb/kg = 70kg. 70kg x 0. 8 g/kg = 56g of protein/day. Most americans exceed their rda for protein. 50 - 175g for 2000 calorie diet. More than 60% of protein consumed comes from animal products. 9 essential that must be supplied by the diet. 11 non-essential that the body can synthesize. Condensation of 2 amino acids to form a dipeptide. After translation, amino acid chains fold into a particular shape. Results in an altered protein and dysfunction. Sickle cell anemia: two of the four hemoglobin polypeptide chains have normal sequence but the other two do not. Hemoglobin loses its ability to carry oxygen. Denaturation: alters shape and function of proteins to bind to enzymes. Caused by heat, light, change in ph, alcohol. Pepsin activated to break proteins into single amino acids.
