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Proteins
- performs the body's work
- provide energy (4Kcal/g)
- chemical makeup
- arranged in strands of amino acids
- supply nitrogen to the body
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Chemical makeup of Proteins
- carbon
- hydrogen
- oxygen
- nitrogen
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structure of amino acids
- acid group
- amino group
- side group
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Amino acids
- 20 diffrent amino acids make up all proteins
- nine essential amino acids
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20 diffrent amino acids make up all proteins
- analogous to letters of the alphabet
- diffrent amino acids have diffrent side chains
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Nine essential Amino Acids
must be taken in through the diet
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conditionally essential amino acids
- Genetic disease - Phenylketonuria (PKU) - infants
- Phenylalannine --> tyrosine
- patients with PKU cannot meatbolize phenylaline
- tyrosine becomes an essentail amino acid
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Protein synthesis
DNA contains coded instructions for the amino acid sequence of proteins (Genetic code)
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How amino acids build proteins
peptide bonds (link together amino acids)
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Structure and functional relationship of proteins
- order of amino acids determines its ultimate shape
- proteins final shape determines its funtion in the body
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Genetic defects
- Genetic defects can also alter protein folding
- example - sickle cell anemia
- defect in protein hemoglobin (oxygen carring protein in RBCs)
- sickle cell paintes have change in one amino acid ( valine -> glutamic acid)
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Denaturation
unfolding of proteins
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digestion of proteins in teh stomach
proteins are denaturated by cooking and or by acid in the sotmach
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Gastrin
stimulates the release of acid and pepsin
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pepsin
enzyme that breaks down proteins into smaller peptides
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Digestion of proteins in small intestine
- pancrease release enzymes ( proteases) into small intestine
- amino acids are ready for absorption
- go to liver
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Proteases
breaks down proteins into individual amino acids
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Role of Protein in the body
- support growth and maintenance
- building enzymes, hormones, antibodies
- maintaing fluid and electrolyte balance
- satlety
- provide energy (not very important)
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Proteins and energy
- contributes very little energy needs in healthy people
- total amount of protein in the body remains constant
- equilibrium = protine intake =protein excretion
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Postive protein balance
- Protein intake is greater than protein excretion
- growth
- pregnancy
- atheletic training
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Negative protein balance
- protein intake is less than protein excretion
- fasting
- starvation
- disease
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Conditions in which proteins are used for energy
- starvation
- disease states Ex. Diabetes
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Results in amino acid wasting
your not using amino acids for their prupose
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Amino acid wasting
- amino acids cannont be stored
- body dose not have enough energy from other sources
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Another form of Amino acid wasting
- body has movre protein than it needs
- exceeds the body's need for protein synthesis
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Proteins in food - Animal Protein - 70% US Diet
- beef
- poultry
- fish
- milk
- cheese
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Proteins in Food -Plant Proteins
- also provides vitamins, minerals, fiber
- nuts, beans, soy
- limited saturated fat , no cholestrol
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Dietary Protein - high quality protein (complete)
contains ample amount of all 9 essential amino acids
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Dietary Protein - low quality protein (incomplete)
- deficeient or low in one or more essentail amino acids
- limiting amino acid
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Complementary Proteins
- two or more proteins combine to compensate for deficienes in essentail amino acid content in protein
- THINK --> red beans and rice
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Is a High Protein Diet Harmful?
- low in plant foods (fiber) vitamins, phytochemical
- intake of animal protein increases risk for heat dieses
- excessive intake of red meat in linked to colon cancer
- burden on the kidneys
- increase calcium loss
- no more than 2X RDA protein
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RDA for Protein
- increased by 10-15g/day for pregnancy
- athletes may need 1.5-2g Kg body weight
- most of US east more than the RDA for protein
- excess protein cannot be stored
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Protein deficeny
Kwashiorkor
edema with maintance of some subtance for children
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Protein deficency
Morosmus
Skin and bones apperance with little or no substance for tissue
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Vegetaria Diet
- why become a vegetarian
- vegans
- fruitarian
- lactovergeterians
- lactoovovegetarians
- concerns for infants and children
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