protein: amino acids. objectives after reading chapter 5, class discussion and activities you will...
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Protein: Amino Acids
Objectives• After reading Chapter 5, class
discussion and activities you will be able to:– Describe the role of proteins– Distinguish between complete and
incomplete proteins– Identify sources of quality protein – Calculate calories from protein
Objectives• Describe protein digestion/absorption• Identify RDA for protein• Discuss health related effects of
protein
Protein• Essential part of all living cells• Found in animals and plants;
Particularly rich in animal foods – meats, poultry, eggs, etc.
• Protein is in your skin, hair, nails, muscles, etc.
• Made of amino acids – amino acids contain nitrogen, which is necessary for life.
Amino Acids
p. 182
Fig 6-1
Amino Acids• Nonessential amino acids
– Body can synthesize– Over half of the 20 AA
• Essential amino acids– Body cannot synthesize– Nine (9)
• Conditionally essential amino acids– PhenylalanineTyrosine; New Borns
p.182 Tab 6-1
Proteins• Peptide bond
– Dipeptide– Tripeptide– Polypeptide
Proteins
• Dipeptide
Proteins• Polypeptide (Example: Insulin)
• Protein shape and function
• Amino Acid Sequences
Proteins• Protein denaturation
– Uncoiling & loss of shape– Therefore, loss of function– Caused by heat, acid, mechanical– Examples: cooked egg, egg whites,
curdling of milk, separation of foods with milk or egg (syneresis)
Protein Digestion• Mouth
– Mixing, moisturizing
• Stomach– HCl– Pepsinogen pepsin
•ProenzymeEnzyme
Protein Digestion• Small intestine
– Proteases•Intestinal and pancreatic
– Peptidases
p. 186
Fig 6-6
Protein Absorption• Carriers
– Transport AA into intestinal cells– Used for synthesis and energy
• Capillaries– Carried to liver
• Absorption misconceptions– Enzyme/amino acid supplements
Protein Synthesis• Delivering the instructions
– DNA•mRNA- attaches to ribosome
–Protein-making machine
Protein Synthesis• Sequencing errors
Roles of Proteins• Building material: Building blocks
of muscles, blood, skin, bones, teeth; protein matrix=collagen – Growth– Maintenance
Roles of Proteins• Enzymes=catalysts
p. 190 Fig 6-9
Roles of Proteins
• Hormones– Switching Machines
Roles of Proteins• Regulation of fluid balance
– Edema
• Acid-base regulation– Acidosis– Alkalosis
• Transport proteins
Roles of Proteins• Immunity: Molecular Memory
– Antibodies: Giant protein molecules designed to combat
– Antigens: Invading foreign proteins (virus)
Roles of Proteins• Source of energy
– Gluconeogenesis– No storage source=muscle wasting– “Amino acid pool”
• Other roles– Fibrinblood clotting– Opsin—light-sensitive pigment
Protein Metabolism• Protein turnover
– Amino acid pool: supply of AA from food/body; collect in cells & blood; ready for use
• Nitrogen balance– Positive nitrogen balance– Negative nitrogen balance
Protein Metabolism• Using amino acids to make
proteins=CONDENSATION
• Using amino acids to make nonessential amino acids
Protein Metabolism• Using amino acids to make other
compounds– Neurotransmitters
• Using amino acids for energy and glucose
• Deamination: AA stripped of N– Ammonia produced
Protein Quality• High-quality proteins
– All essential AA– Animal proteins=complete– Plant proteins=incomplete
• Amino acid composition– Limiting amino acid
• Digestibility– Animal vs. vegetable
Protein Quality
• PDCAAS– Protein
digestibility-corrected amino acid score
• Reference Protein
Protein Quality• Complementary proteins
– Two protein foods make up for the lack of certain amino acids in each other when eaten together
Food Labels• Quantity of protein
• Daily Value– 50 g protein
•10% of a 2000 kcal diet
Nitrogen Balance• Determine adequacy of protein intake• N2 In - N2 Out = Nitrogen Balance
– N2 In = Protein Intake as Nitrogen– N2 Out = 24 Hour Urine Collection for N2
+ Stool, Insensible Losses
• Positive Nitrogen Balance– Body excretes less protein than is taken in (Anabolism)
• Negative Nitrogen Balance– Body excretes more protein than is taken in (Catabolism)
Protein-Energy Malnutrition (PEM)
• Marasmus– Slow developing, chronic PEM– Muscle wasting; no body fat– Pluckable hair; dry skin
• Kwashiorkor ??????
• Marasmus-kwashiorkor mix
p. 197
Tab 6-3
p. 197 Tab 6-3
Protein-Energy Malnutrition (PEM)
• Infections not protein intake– Dysentery
• C-Reactive Protein
Health Effects• Conditions Associated with Other
Nutrients:– Osteoporosis – Calcium– Heart Disease – Fat– Obesity – Fat/CHO– Cancer - Fat
Health Effects• Genetic Associated Diseases
– Phenylketonuria– Sickle Cell Anemia
• Kidney Disease
Recommended Intakes
• RDA– 0.8 g/kg/day– 10% - 35% of energy intake
Objectives• After reading Chapter 5, class
discussion and activities you will be able to:– Describe the role of proteins– Distinguish between complete and
incomplete proteins– Identify sources of quality protein – Calculate calories from protein
Objectives• Describe protein digestion/absorption• Identify RDA for protein• Discuss health related effects of
protein