nutrition proteins

protein

essential macronutrient; carbon, hydrogen, and oxygen; also contain nitrogen

RDA for protein

0.8 g/kg

RDA adult men

56 g

RDA adult women

46 g

AMDR range for carbs

45-65% of total cals

AMDR range for fat

20-35% of total cals

AMDR range for protein

10-35% of total cals

protein roles

structural material, growth maintenance and repair, energy source

protein critical functions

enzymes, hormones, antibodies, fluid balance, pH balance, transporters, blood clotting

building blocks of protein

amino acids

amino acids are linked by

peptide bonds to form proteins

dipeptides

2 amino acids

tripeptides

3 amino acids

polypeptide

many amino acids

essential amino acids

9; cannot be produced by the body; must be obtained through the diet

non-essential amino acids

can be produced by the body

9 essential amino acids

hisitidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

first step in protein synthesis

DNA template to make the protein; transcription(mRNA copies instructions)

second step in protein synthesis

mRNA carries code to ribosomes; ribosomes are protein factories

third step in protein synthesis

mRNA specifies sequence of amino acids; translation; tRNA

what determines function of protein

shape; after translation, amino acids fold into particular shape; to function properly they must retain their 3D shape

denaturation

alters shape and function; caused by heat, light, change in pH, alcohol, or motion; important in the digestion of protein

digestion of proteins

begins in the stomach; acidic juices; pepsin(enzyme); continues in the small intestine; pancreatic proteases, absorption of amino acid

HCl role in protein digestion

denatures proteins so digestive enzymes can attack peptide bonds; converts pepsinogen to pepsin so it can make protein into smaller peptides

end goal of protein digestion

break long polypeptides into single amino acids

protein turnover

proteins are constantly broken down and reassembled; continual production and destruction; free AA form pool(in cells and blood); amino acids pool = food intake and body break down used for protein production and energy(if stripped of nitrogen)

nitrogen balance

reflects whether the body is gaining, losing, or maintaining protein; out through urine and feces, sweat and other secretion, skin hair and nails

positive nitrogen balance

growing infants, children, adolescents, pregnant women, recovering from illness; retaining protein in new tissue as they add bone, blood, skin, and muscle cells

increase in total body proteins

nitrogen eqilibrium

healthy adult meeting protein and energy needs

negative nitrogen balance

inadequate intake of protein and energy intake, conditions like fever burns and infections, bed rest, deficiency of essential amino acids, increased protein loss, increased secretion of certain hormones such as thyroid hormone and cortisol

decrease in total body protein

amino acids can be altered to produce many important compounds

synthesize proteins, metabolize as a source of energy, synthesize into glucose or fat

deamination

before protein can be used for energy the amino group 2(NH2) must be removed; 1. remove the amino group(liver converts ammonia then to urea and kidneys excrete urea) 2. remaining carbon skeleton(made into energy, glucose, or fat)

benefits of slightly higher protein intake

adults over 65 yr old; 1.2 g/kg is beneficial for reducing loss of lean body mass, improving functionality, reduce risk of disability and death, particularly effective when combined with resistance training program

do athletes need more protein

optimal protein intake for performace advantage 1.2-1.7 g/kg body weight

protein quality

measure of how well a protein food meets the needs for protein synthesis; based on proportion of essential amino acids; consuming a wide variety of plant-based foods can meet protein needs

complete protein

contain all 9 essential amino acids; meat, dairy, eggs, soy, quinoa

incomplete protein

lack one or more 9 essential amino acids; most plant foods

complementary protein

combine 2 incomplete proteins to make complete protein

limiting amino acid

amino acid in shortest supply

plant based diets emphasize whole plant foods

veggies and fruit; whole grains, beans legumes, nuts and seeds; minimal processed foods; limited animal foods; mediterranean and vegetarian diets; multiple health benefits(lower total blood cholesterol, low-density lipoprotein cholesterol levels, blood pressure, reduced cardiovascular risk, lower risk of obesity, heart disease, cancer, type 2 diabetes, and overall mortality

vegans inadequate intake

calcium, vitamin D, and riboflavin

vitamin b12

found naturally only in foods of animal origin; vegans obtain from fortified foods, fortified nutritional yeasts, b12 supplements

protein energy malnutrition

protein deficiency occurs in combination with a deficiency fo energy; worst effects seen in children, fail to grow normally, develop in diarrhea, infections, diseases, early death

marasmus

deficiency in protein and calorie intake; skin and bones appearance; weather, politics, poverty disrupt food supply

kwashiorkor

inadequate protein intake; edema/fatty liver(swollen belly); developing countries - high grain intake; shorter, flakey skin, prone to infection

US protein deficiencies

alcoholism, long term illness, malabsorption, injuries, food insecurity

high protein diets

do not differ from other diets in long term weight maintenance; may help initial weight loss; high animal protein; eat more fish, poultry, nuts, and beans