Protein: Amino Acids

download report

Transcript Protein: Amino Acids

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. 163
Fig 5-1
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
– PhenylalanineTyrosine; New Borns
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)
p. 176
Protein Digestion
• Mouth
– Mixing, moisturizing
• Stomach
–HCl
–Pepsinogen  pepsin
•ProenzymeEnzyme
Protein Digestion
• Small intestine
–Proteases
•Intestinal and pancreatic
–Peptidases
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
p. 164-168
Roles of Proteins
• Enzymes=catalysts
p. 165 Fig 5-6
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
–Fibrinblood clotting
–Opsin—light-sensitive pigment
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 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 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
digestibilitycorrected
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. 171
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
• Celiac Disease; Sprue
• Liver Disease
• 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