Chapter 6: Proteins Flashcards
proteins are
macronutrients
how many kcals/g are proteins
4 kcals/g
protein involvement in enzymes
all enzymes are made of proteins
protein involvement in hormones
some hormones are made of proteins
proteins participate in
every cellular activity that helps the body function
protein structure
protein is made up of chains of amino acids that are made based on an individual’s DNA
proteins’ structure differ from that of CHO and lipids
- excess dietary protein cannot be stores in the body
- proteins contain nitrogen, along with carbon, hydrogen, and oxygen
- some proteins contain sulfur which isn’t found in CHO or lipids
amino acids
the building blocks of proteins
how many amino acids are used to make proteins
there are 20 amino acids used
types of amino acids used
essential and nonessential
how many essential amino acids
9
how many nonessential amino acids
11
essential amino acids
must be consumed in the diet
nonessential amino acids
can be synthesized in the body
how are proteins classified
by the number of amino acids in the chain
peptides
fewer than 50 amino acids
types of peptides
dipeptides, tripeptides, and polypeptides
how many amino acid chains do dipeptides have
2 amino acids
how many amino acid chains do tripeptides have
3 amino acids
how many amino acid chains do polypeptides have
3 to 50 amino acids
how many amino acid chains do proteins have
more than 50 amino acids (usually from 100-10,000 amino acids linked together)
anatomy of an amino acid
- carbon center
- amine group (NH2)
- carboxylic acid group (COOH)
- hydrogen (H)
- side chain (R group)
side chain (R group)
a unique side chain distinguishes the various amino acids
peptide bonds form through
condensation
peptide bonds break through
hydrolysis
condensation
when the carbon of the acid group (COOH) of one amino acid joins with the nitrogen atom of the amine group (NH2) of a second amino acid and release a molecule of water
hydrolytic reaction
when peptide bonds are broken down by hydrolysis, the hydroxyl group (OH) and hydrogen (H) from water are added
hydrolysis
a molecule of water is added to the amino acid
conditionally essential amino acids
tyrosine and glycine
tyrosine
production of neurotransmitters during periods of stress
glycine
collagen synthesis during pregnancy
structure impacts
function
altering the shape of a protein
alters the function of a protein
when the shape of a protein is changed, what aspect of the protein remains unchanged
the primary structure is unchanged
4 levels of protein structure
primary, secondary, tertiary, and quaternary
primary level of protein structure
sequence of amino acids in a polypeptide chain (how they are linked in the chain)
secondary level of protein structure
local folding of the chain into alpha helices and beta sheets that depends on the hydrogen bonds (how it folds)
tertiary level of protein structure
overall 3D shape of a single polypeptide chain, dependent on the interactions of the side chains (R groups) of each amino acid (how the sequence is set up and how it folds)
quaternary level of protein structure
how multiple polypeptide chains assemble into subunits into a single functional protein (larger protein molecule)
denaturation means
unfolding
denaturation of proteins occurs in the presence of
heat, acids, bases, salts, and mechanical agitations
once a protein is denatured
it can’t go back
example of denaturation
when cooking an egg, the egg white becomes white with heat (it is becoming denatured) and you cannot revert the egg white back to how it was before the heat
protein digestion begins in the
stomach
protein digestion in the stomach
gastrin stimulates the release of hydrochloric acid (HCL)
role of HCL in the digestion of proteins
HCL denatures the proteins and converts pepsinogen to pepsin
role of pepsin in the digestion of proteins
pepsin breaks polypeptides into shorter chains
digestion of proteins continues in the
small intestine
polypeptides enter the
small intestine
in the small intestine, polypeptides are
broken down
role of CCK in the digestion of proteins
CCK stimulates the release of proteases by the pancreas
role of proteases in the digestion of proteins
proteases break apart polypeptides
types of proteases
pepsinogen, trypsin, chymotrypsin, carboxypeptidase, aminopeptidase, dipeptidases, and tripeptidases
pepsinogen is made in the
stomach by chief cells
pepsinogen is
activated to pepsin by HCL
pepsinogen breaks apart
polypeptides into shorter polypeptide chains
trypsin is made in the
pancreas
trypsin is released in the
small intestine
trypsin breaks apart
peptide bonds
chymotrypsin is made in the
pancrease
chymotrypsin is released in the
small intestine
chymotrypsin breaks apart
peptide bonds
carboxypeptidase is made in the
pancreas
carboxypeptidase is released in the
small intestine
carboxypeptidase breaks free
one amino acid at a time from the carboxyl end (COOH) of a peptide chain
aminopeptidase is released in the
brush border of the small intestine
aminopeptidase breaks free
the end amino acids from tri- and -dipeptides into single amino acids
dipeptidase breaks
dipeptides into single amino acids
tripeptidases breaks
tripeptides into single amino acids
amino acids are absorbed in the
small intestine
from the small intestine, amino acids are transported to
the liver
how are amino acids transported from the small intestine to the liver
via the portal vein
the most metabolically active organ in the body is
the liver
in the liver, amino acids are:
- used to synthesize new proteins
- converted to energy, glucose, and fat
- released to the bloodstream and transported to cells throughout the body
occasionally proteins are absorbed
intact
amino acids are metabolized in the
liver
liver metabolizes amino acids depending on
the body’s needs
most amino acids are (amino acid metabolism)
sent into the blood to be picked up and used by cells
if the diet is low in CHO (amino acid metabolism)
the amino acids are converted into glucose through gluconeogenesis
amino acids can be used for energy when (amino acid metabolism)
the diet is deficient in kcals (ATP)
energy metabolism
niacin
amino acid pools supply
provide a ready supply of amino acids to create proteins on demand for the body’s ongoing need for protein synthesis
what does the body do daily that we need amino acid pools
the body breaks down and makes proteins daily to maintain tissues and organs
extra protein is used to help the body
heal
protein turnover
the process of degrading and synthesizing proteins
about how many proteins are turned over daily
more than 200 grams of protein is turned over daily
transcription
- DNA to mRNA (messenger RNA)
- copying/the making of the script
transcription is the first step in
protein synthesis (the making of proteins)
transcription happens in the
nucleus
steps to transcription
conversion of genetic information and preparation for translation
conversion of genetic information
copying a specific gene’s DNA sequence into mRNA
the mRNA created serves as a
temporary, mobile copy of the genetic information
preparation for translation
the mRNA molecule carriers the information from the DNA in the nucleus to the cytoplasm
where are proteins made
the cytoplasm
codons
sets of 3 nucleotides that specify particular amino acids
mRNA includes
codons
translation
- mRNA to protein
- building the actual protein
translation happens in the
cytoplasm
three steps of translation
reading the mRNA, the amino acid assembly, and the protein formation
in the cytoplasm, what reads the mRNA sequence
ribosomes
each codon in the mRNA corresponds to
a specific amino acid
amino acid assembly
- tRNA (transfer RNA) molecules bring the appropriate amino acids to the ribosome
- the ribosome matches the tRNA anticodons to the mRNA codons, linking the amino acids together in the correct order
protein formation
- as the ribosome continues to move along the mRNA, it elongates the growing protein chain until it reaches a stop codon
- at this point, the newly synthesized protein is released
sickle cell anemia
a common blood disorder that involves abnormal or flawed protein formation
deamination
the removal of an amine group from an amino acid
what is formed from deamination
ammonia and a keto acid
when the amino acid pool reach capacity
amino acids are broken down to be used
carbon containing remnants of deamination are:
- converted to glucose (if glucogenic amino acid)
- converted to fatty acids and stored as TG
- oxidized for energy via metabolic pathways
when we have excess amino acids we
pee them out
amine group is released in the liver
which creates ammonia, which is converted to urea and excreted out in the urine
transamination
the process of forming nonessential amino acids by transferring the amine group from an essential amino acid to a keto acid to form a nonessential amino acid and a new keto acid
functions of proteins
- provide structural support and enable movement
- act as a catalyst
- act as a chemical messenger
- regulate fluid balance
- help maintain acid base balance
- contributes to a healthy immune system
- transport proteins shuttle oxygen, waste products, lipids, some vitamins, sodium, and potassium through the blood and cell membranes
- provide energy
- provides satiety
proteins act as a catalyst
enzymes speed up reactions
proteins act as a chemical messenger
hormones regulate cell actions
proteins regulate fluid balance by
a protein marker found in the blood
- albumin
- C-Reactive protein
albumin
when these levels drop, the body has a hard time keeping fluid where it needs to be
edema
- excess fluid
- albumin level could be low
- push down on the skin and will take very long to come back up
proteins contributes to a healthy immune system
antibodies are proteins that bind and neutralize pathogens
proteins help transport potassium
potassium starts outside the cell but wants to be inside the cell
proteins help transport sodium
sodium starts inside the cell but wants to be outside the cell
proteins provide satiety
- more than any other macronutrient
- proteins –> carbs –> fats
nitrogen balance
- consume enough protein to replace what is used
- taking in the right amount of nitrogen and not excreting too much
positive nitrogen balance
- amount of nitrogen consumed exceeds the amount used
- associated with periods of growth
- either need to consume more or the body doesn’t excrete a lot out
- pregnancy, childhood/adolescence, exercise
negative nitrogen balance
- the amount of nitrogen used exceeds the amount consumed
- illness, injury, inadequate protein intake, malnutrition, stress
RDA for protein
0.8 g/kg for adults >18
how to find the RDA for protein
divide your weight from pounds into kg then multiple by 0.8
AMDR for protein
10-35% of total kcals
protein intake recommendations for people over 65
1 g/kg (have to think about maintaining bone density)
protein intake for athletes
athletes can need 50-100% more protein, typically recommendations don’t exceed 2.2 g/kg
protein sources
high quality protein, complementary and complete protein
high quality protein
- digestible
- contains all essential amino acids
- adequate protein to synthesize nonessential amino acids
complete proteins
- contain all 9 essential amino acids
- usually animal sources (meat, fish, poultry, dairy)
- exception: soy protein and quinoa
incomplete proteins
- low in one or more essential amino acids
- the limiting amino acid (missing some parts)
examples of incomplete proteins
grains, nuts, seeds, legumes
complementary proteins
- combining incomplete proteins with a food that supplies the limiting amino acid
examples of complementary proteins
- rice + beans = a full protein
- legumes + grains or nuts or seeds = a full protein
food sources of protein
eggs, meat, fish, poultry, soy, and dairy
a 3 oz serving of cooked meat, fish, or poultry
- provides about 7g of protein per oz
- 3 oz serving gives you about 21g of protein
- about the size of a deck of cards
best approach for sources of protein
eat a variety of foods
protein supplements are typically unnecessary because
most Americans well exceed their protein needs
too much protein
- may increase risk for cardiovascular disease
- increased risk for osteoporosis
- increased risk for kidney stones
may increase risk for cardiovascular disease
high protein can be associated with high saturated fats
increased risk for osteoporosis
- if there is low calcium intake
- high protein with adequate calcium intake is protective of the bone
increased risk for kidney stones
diet high in animal protein and low in CHO lowers urine pH, increasing risk for kidney stones
an overemphasis on protein can result in
a displacement of other key nutrients from fruits, vegetables, and whole grains
too little protein
- increase risk for osteoporosis
- malnutrition
- inadequate protein
malnutrition
protein energy malnutrition (PEM)
inadequate protein
- cell lining of GI tract not sufficiently replaced
- digestive function is inhibited
- absorption of food is reduced
- immune system is compromised
protein energy malnutrition (PEM)
- protein is used for energy rather than its functions in the body (we don’t want to use protein for energy!!)
- more prevalent in infants/children
- in the US, elderly people are more at risk
malnutrition (PEM)
- 1 in 8 people don’t have adequate protein intake, kcal, or both
- available protein is then used as an energy source
- lack of protein damages the GI tract
- decreased immune function
types of PEM
kwashiorkor and marasmus
kwashiorkor
- severe protein deficiency
- have enough energy and fat but not enough protein
- can come on very quickly (less than a month)
- no visible bones, fuller cheeks, very bloated stomach
symptoms of kwashiorkor
- edema in the legs, feet, and hands (albumin drops)
- diminished muscle tone and strength
- brittle hair that is easy to pull out
- pale, sad, apathetic appearance
- prone to infection, increased HR, fluid in lungs, pneumonia, septicemia, and electrolyte imbalances
marasmus
- chronic starvation
- severe malnutrition in all the nutrients
- very squared off shoulders (sign of low fat consumption)
- temporal areas and under eyes sunken in (missing the pad of fat)
- results from severe deficiency in kcals
marasmus symptoms
- frail, emancipated appearance
- weakened and appear apathetic
- often cannot stand without support
- appears older in age
- hair is thin, dry, and lacks sheen
- low body temperature and BP
- prone to dehydration, infections, and unnecessary blood clotting
treatment for PEM
- medical and nutritional treatment can reduce mortality rate
- should be implemented carefully and slowly
step 1 in treatment for PEM
address life threatening factors
addressing life threatening factors first
- severe dehydration
- fluid and nutrient imbalance
step 2 in treatment for PEM
restore depleted tissue
restoring depleted tissue second
gradually provide nutritionally dense kcals and high quality protein
step 3 in treatment for PEM
transition to foods and introduce physical activity
transitioning to foods and introducing physical activity third
any type of movement
why people choose a vegetarian diet
for a number of reasons
- ethical
- religious
- environmental
- health
lacto-vegetarian eats
grains, veggies, fruits, legumes, seeds, nuts, and dairy
lacto-vegetarian avoids
meat, fish, poultry, and eggs
lacto-ovo-vegetarian eats
grains, veggies, fruits, legumes, seeds, nuts, dairy, and eggs
lacto-ovo-vegetarian avoids
meat, fish, and poultry
ovo-vegetarian eats
grains, veggies, fruits, legumes, seeds, nuts, and eggs
ovo-vegetarian avoids
meat, fish, poultry, and dairy
vegan eats
grains, veggies, fruits, legumes, seeds, and nuts
vegan avoids
any animal foods (meat, fish, poultry, dairy, and eggs)
pescetarian eats
grains, veggies, fruits, legumes, seeds, nuts, dairy, eggs, and fish
pescetarian avoids
meat and poultry
semi vegetarian eats
a vegetarian diet that occasionally includes meat, fish, and poultry
semi vegetarian avoids
meat, fish, and poultry on occasion
potential benefits of a vegetarian diet
reduced risk of: cardiovascular disease, hypertension, diabetes, cancer, stroke, and obesity
with a vegetarian diet, at risk of deficiencies in
- protein
- calcium
- iron
- B12
- zinc
- vitamin A
- vitamin D
- omega 3 fatty acids
iron for women
women need 18 mg a day
iron for men
men need 8 mg a day
B12
have to be really cautious when pregnant
zinc
- comes in a lot of animal products
- aid in the immune system
