PROTEIN

Protein Structure

Polymer of amino acidsamine group (N)acid groupside chain

Protein Structure

Proteins are unique among energy nutrientsThey contain NITROGENComposed of 20 different amino

acids9 amino acids are essential, other 11 are not essential

Proteins are strands of amino acidslinked by a peptide bond with next amino acid

Glucose Triglyceride

Protein Structure

Primary StructureAmino acid sequence or strand

like a strand of pop-beads or pearls

Secondary Structure coiling of the strand

like a slinky: positive and negative parts attract each other

Protein Structure

Tertiary or third level of structureFolding back of coil

The slinky gets messed upQuaternary or fourth level of

structureSubunits fit together

Hemoglobin has four subunits to make the functional molecule

Protein Structure

SHAPE DETERMINES FUNCTIONThe shape of the protein molecule determines if the molecule is functionalthe shape of the lipase molecule determines if it will actually help breakdown a lipid

Protein StructureChange of shape is called DENATURATION

What causes change of shape?acid (like the stomach low pH) or

base(high pH)alcoholmechanical agitation(beating an egg

white)heat(heat an egg white) or heavy

metals(mercury)

Denaturation

Cellular Protein Synthesis

DNA: in nucleus: acts as a template for mRNA

mRNA moves out of nucleus to cytoplasmCarries instruction for an amino acid sequence

for a specific protein to a ribosomeRibosome ‘reads’ the mRNA which dictates which

amino acid is nexttRNA carries the correct amino acid to the mRNA

Cellular Protein Synthesis

tRNA’s line up one after the other with amino acids

Amino acids form peptide bonds to make the primary sequence of the protein

Protein then coils to form the secondary and tertiary structure

SHAPE DETERMINES FUNCTION

How Are Proteins Made?

Heredity Factor

Cystic fibrosisHypercholesterolemia

LDL-receptor

Sickle cell anemia

Sickle-cell hemoglobin

Protein Digestion

StomachDenaturationPepsin induced breakdown into shorter

‘peptides’Small Intestines

duodenum: peptidases or proteases enter from pancreas thru the common bile ductbreakdown proteins to aa’s,

dipeptides and tripeptides

Protein Digestion

Cells of small intestinecomplete digestion of proteins so that only amino acids remain

cells of S.I. absorb amino acids and a few larger peptides and release them into the blood for circulation

Protein Function

Structure proteinsMuscle fiber proteinConnective proteinsothers

Protein: Function

Supporting Growth and Maintenancebody needs amino acids to grow new cells and replace cells that are worn out

Protein: FunctionBuilding Enzymes, Hormones,

and other Compoundsamino acids used to make enzymes (e.g.. lipases for digestion)

amino acids used to make some hormones(e.g.. insulin for glucose metabolism)

Protein: FunctionBuilding Antibodies

antibodies are formed from amino acids to defend against foreign proteins and substances in the body

Maintaining fluid and electrolyte balanceProteins act like magnets and hold

water in the blood vessels and also electrolytes like sodium

Transport Proteins

Cellular content differ from the contents of the surrounding environment: fluids and electrolytesProtein Membrane carriers provide a ‘pump’ to maintain this differenceSodium-Potassium Pump

Animation of the Sodium-Potassium Pump

Protein: Function

Maintain acid-base balanceproteins buffer the blood against big changes in pH so body remains pretty neutral

.

Protein: FunctionProviding Energy

When insufficient CHO and Fat are eaten, the body takes apart Protein for energy

Nitrogen portion removed from A.A. and the rest is oxidized for energy. Nitrogen ends up in the urine as urea

Amino Acid PossibilitiesCan be added to other A.A.’s to make

a proteinCan have Nitrogen removed

then it can be oxidized for energy ormade into glucose (glucogenesis) ormade into fat (lipogenesis)

The diet needs to supply the 9 essential amino acids and 0.8 grams protein/kg wt.

Protein Quality, Use and Need

Protein Qualitythe amino acid assortment greatly influences a protein’s usefulness to the body

Protein Quality, Use and Need

Measuring Protein Qualitythe amount of the essential amino

acids present in the proteinIf all are well represented, the

protein will support growth and maintenance: COMPLETE PROTEIN

If not, it won’t support growth: POOR QUALITY PROTEIN

Protein quality

Complete or good quality proteinssoy beans, milk protein, animal flesh

Poor quality proteinsgrains (missing lysine, an essential amino

acid)many legumes(beans, missing methionine)

Mutual Supplementation or complementing proteinsmix grain and legume and get a good quality

protein eg: corn tortilla and refried beans

Vegetarian Diets-Reasons

HealthReligionEthicalEnvironmentalTaste

Types of Vegetarian Diets

Non-red meat vegetarianpoultry, fish, dairy, eggs O.Kno special nutritional problems, may be high in fat, saturated fat

Lacto-ovo vegetarianmilk and eggs O.K.no special nutritional problemsmay be high in fat, saturated fat

Vegetarian Diets: Types

Strict Vegetarian: Veganno animal productsprotein quality-complementcalciumironvitamin B 12Top Stories - The Olympian - Olympia, Washington

Vegetarian vs Meat eatersVegetarianreduced risk

obesitydiabeteshypertensionheart diseasedigestive disorderscancer

Meat eatersgrowthsupport during critical times.

Protein RDA: 0.8 grams/kg

Nitrogen balance negative balance= more out

in urine than coming in from the diet

protein is being broken down faster than it is replaced

who is in this predicament? elderly, bedridden

Protein RDA: 0.8 grams/kg

positive balance=more in the diet than going out in the urineprotein is being made into tissue faster than it is taken apart

Protein Rich Foods

Animal productsalso high in vitamin B12, iron, and

zinclacking in vitamins C and folateoften high in fat

Legumessoy protein almost “complete”high in fiber, many B vitamins, iron,

calciumlow in vitamins A, C and B12

Protein Needs154# (70 kg)RDA = 70 x .8g/kg = 56 gramsAthlete 1 to 1.5 g/kg (ADA)= 70 to 105 grams Protein/day

Too little Protein

Kwashiorkor: Protein deficiencytrue definition: what happens to the first child

when the second child is bornsymptoms: edema, ascites(swollen belly) immune system failure so many infectionsloss of pigmentation

Phenylalanine to Tyrosine to Melanin is blocked

Fatty Liverno lipoproteins to carry fats and

accumulate in liver

Too Much Protein

Dehydration100 Cal of extra protein takes 350

grams(12 oz) of water to clear( this is how many grams of protein?)100 Cal of extra CHO or Fat only

takes 50 grams of water to clearCoupled with heavy workouts may

result in dehydration

Protein needs of Athletes

May be up to 1.7 for power athletesMay be up to 1.4 grams/kg for

endurance athletesTour de France, marathoners,

triathletesThey may need every available source of energy they can get their hands on