Human Nutrition Exam 3

functions of proteins

structural materials like muscle/bone/skin/nails, growth, maintenance, repair, energy at 4kcal, critical functions like enzymes/hormones/antibodies/fluid balance/ acid base balance/ transporters/ blood clotting

healthy non growing adult

0.8 grams of protein per kg of body weight

athletes

1.2-1.7g/kg

elderly

1.0-1.2g/kg

adequate energy

with enough kcal you do not use much protein for energy and can instead keep the protein for all the functions it is needed for

protein AMDR

10-35%

find AMDR

Multiply 2400kcal or amount eaten by each percentage  

find RDA for 154 lb adult

154/2.2kg= 70kg then 70kg times 0.8g= 56g

find 12% of 2400kcal and grams

2400 times .12= 288kcal then 288/4g= 72g

structure of amino acid

Consists of central carbon atom, amino group with nitrogen, acid group, hydrogen, variable side chain  

side chain

where amino acids differ

peptide bonds

amino acids are joined by these

essential amino acids

9, can’t be made by the body

nonessential amino acids

11, can be made by the body

step 1 transcription

DNA undwinds

step 2 transcription

info from DNA is transcribed into messenger RNA or mRNA

step 3 transcription

mRNA carries info into cytoplasm where protein synthesis occurs

step 1 translation

mRNA interacts with ribosomes that read mRNA and translates it into an amino acid sequence to assemble a protein  

step 2 translation

tRNA molecules carry specific amino acids to ribosomes 

step 3 translation

ribosomes direct tRNA matching mRNA to proper position to be added 

step 4 translation

Empty tRNA carrying previous amino acid moves out of the way so TRNA carrying next amino acid moves into position and process continues  

step 5 translation

newly formed protein chain detaches from ribosomes and translation is done 

step 6 translation

peptide bonds are formed

amino acids and translation

most are used to make working proteins in the body like enzymes or muscle cells

amino acids and translation

what gets made is controlled by your DNA which codes for protein  

amino acids and translation

when a protein gets made then it is said that the gene has been ‘expressed’

3 dimensional

long chains of amino acids won’t work unless they are folded

protein folding

after translation amino acids fold into a 3 dimensional shape

protein folding

shape determines protein’s function

protein folding

proteins must retain shape to function properly

protein denaturation

Caused by heat, light, change in pH, alcohol, or motion  and is most common in cooking/digestion, protein can no longer perform its functions

step 1 protein denaturation

HCl in stomach denatures protein making it lose its shape 

step 2 protein denaturation

Pepsin then binds to protein and breaks protein into shorter strands  

protein digestion in mouth

mechanical digestion like chewing

protein digestion in stomach

pepsin breaks down denatured proteins into large peptide fragments, acidic juices like HCl denature the protein  

step 1 protein digestion in SI

Polypeptides are broken down into pancreatic proteases in small fragments  

step 2 protein digestion in SI

Continues at brush border by proteases anchored to microvilli on surface of mucosal cells 

step 3 protein digestion in SI

Individual acids or peptides are absorbed by mucosal cells of SI assisted by transport proteins 

step 4 protein digestion in SI

Dipeptides and tripeptides are broken down to single acids and leave cel through transport proteins to enter bloodstream  

protein turnover

we don’t store amino acids like we have a store of carbs and a store of fats but instead each cell maintains an amino acid pool that is in constant flux 

amino acid pool

comes from protein intake and is a small supply of amino acids present in blood cells used for protein synthesis 

protein turnover

once in the amino acid pool these amino acids can be used to make more proteins, make ATP, make glucose or make fatty acids for storage

amino acid

used to make protein or energy

amino acid

use for energy or glucose or fat

deamination

nitrogen is removed and incorporated into urea in liver and then excreted as urine, leaves CHO available to be used in energy pathways, results in dehydration

high protein diet

results in dehydration due to loss of nitrogen through urine

nitrogen lost in body

urine, feces, sweat, skin, hair, nails

zero equilibrium

nitrogen in= nitrogen out

positive equilibrium

more nitrogen in, building muscle, kids, pregnancy  

negative equilibrium

more nitrogen out, old, sedentary, losing weight, trauma or burn patients 

athletes and protein

don’t actually need more protein but benefit from optimal protein intake for performance advantage

adults over 65 and protein

Reduces loss of lean body mass, improves functionality, reduces risk of diability and health, combine with resistance training  

8 grams

1 ounce of lean meat

8 grams

1-1.5 ounces of fish

8 grams

1 jumbo egg

8 grams

½ to 2/3 cup of legumes

8 grams

¼ to 1/3 cup of nuts

8 grams

1 cup of cooked grains

8 grams

1 cup of milk

8 grams

1 ounce of cheese

protein quality

determined by digestibility and amino acid composition

digestibility

how well a protein is digested, complete proteins are more digestible

amino acid composition

does it contain essential proteins  

limiting amino acid

If there is not enough of an amino acid to make a particular protein, then that amino acid is the limiting one  

complete or high quality protein

all animal proteins and soy, have all the essential amino acids and in the right amounts

incomplete or low quality protein

ll other plant proteins, are low or lacking in one or more of the essential a.a. 

complementary proteins

combining 2 incomplete proteins to make a complete protein

made from soy foods

soy milk, tofu, tempeh, natto, edamame

soy protein isolates

very processed, protein bars and shakes  

my plate soy

soy milk is only non milk allowed  

plant estrogen

in soy foods, lowers breast cancer risk by mimicing estrogen

malnutrition and protein

low protein diets significantly affect countries malnutrition but not the US 

high protein diets

High in saturated fats, cholesterol and sodium but low in fiber, phytochemicals, certain vitamins and minerals

paleo and carnivore

low fiber, removes food groups, encourages healthy foods  

mediterranean diet

Rich in fruits, veggies, nuts, olive oil, and whole grains and low in processed and red meats, dairy products, sweets

minimally processed foods

reudce risk of heart problems and heart related deaths

vegan

no animal foods

lactoovovegetarian

eggs and dairy

lactovegetarian

dairy

pescatarian

fish

quasi vegetarian

poultry and fish

flexitarian

limited meat, poultry, and fish

semi vegetarian

pescatarian, Quasi vegetarian, flexitarian

plant food

More fiber, vitamin C/E, folate, magnesium, potassium, antioxidants, phytochemicals

plant food

less omega 3, B12, calcium, iron, protein  

cancer and diet

diet contributes to 20% of cancers

reduce risk of cancer

stay active, limit red and processed meat, limit salt and alcohol, eat plant based foods

step 1 cancer

initiation or cell mutation

step 2 cancer

promotion or enhance growth

step 3 cancer

tumor progression or cells mutate and expand quickly

step 4 cancer

malignancy or invade surrounding tissue or spread/metastisize to other parts of body  

phytochemicals

not nutrients but prevent cancer from starting or spreading

polyphenols

one category of phytochemicals we mainly eat

phytochemicals

provide color, aroma and flavor

increase phytochemicals

eat a rainbow or variety of foods

vegan diet concerns

low protein, zinc, vitamin D and B12, omega 3 and iodine 

complement proteins

mix of grain and legume like rice and beans or peanut butter and bread

heme iron

much more bioavailable from animal foods

bioavailability

amount of a nutrient that is absorbed and used by the body

vitamin C

enhances absorption of iron