Week 5 Flashcards
proteins
- associated with strength and muscle
- important for wound healing
- structural and functional role in cells
what does excess meat result in?
high saturated fat intakes
what is protein found in?
- milk
- eggs
- legumes
- many whole grains
FRUIT=NO PROTEIN
proteins as working molecules (functional)
- enzymes
- antibodies
- transport vehicles
- hormones
- cellular “pumps”
- oxygen carriers
proteins for structure
- tendons
- ligaments
- scars
- fibres of muscles
- cores of bone and teeth
- filaments of hair
- material of nails
protein components
- made of carbons, hydrogen and oxygen
- contain nitrogen (only one)
- some amino acids also contain sulphur
- composed of amino acids
- 20 different aa make up most of the proteins of living tissue
amino acids
- an amine group at one end-nitrogen containing part
- acid group at the other
- a distinctive side chain (side group) attached to the carbon at that centre of the backbone
***gives identity and chemical nature to each amino acid
side chains (side groups) of aa
what makes the aa different from each other
1. size
2. shape
3. electrical charge
- large strands of aa = large protein molecules
essential amino acids (indispensable)
- aa that cannot be synthesized at all by the body or cannot be synthesized in sufficient amounts
- can only be replenished from foods
- body NEEDs these aa to perform work
- body can make other aa from fragments derived from carbs or fat to form backbones and nitrogen from other sources
nonessential amino acids (dispensable)
- aa that can be synthesized by the body
- the body can make these aa from
- fragments derived from carbs or fat to form backbones
- nitrogen from other sources
indispensable/essential aa
- an aa that is normally nonessential
- in circumstances when the need exceeds the body’s ability to produce it, it must be supplied by the diet
recycling amino acids
body makes some aa but also breaks down proteins to reuse those aa
when do we reuse amino acids?
food proteins (after digestion) and body proteins (after cellular work) are dismantled freeing their aa
- this provides body a tiny aa pool (150g)
- provides raw materials to build protein molecules it needs
protein turnover
bringing in and breaking down proteins
- about 300 to 400 g/day
amino acids used for energy if requires
- tissues can break down their own proteins in times of fuel or glucose deprivation
- working proteins are sacrificed
- most dispensable proteins used first (ex. small proteins of blood and muscle)
- structural proteins are guarded until their used is forced by dire need (ex. proteins of heart)
peptide bond
- connects one aa to another
- formed between the amine of one aa and the acid group of the next aa
- CONDENSATION reaction - forms a chain of aa with side chains bristling out from backbone
condensation reaction
joins amine of one aa and acid group of next aa
primary structure of peptide bonds
amino acid sequences
secondary structure of peptide bonds
polypeptide shapes
1. determined by weak electrical attractions within chain
2. positively charges hydrogens attracts nearby negatively charged O2
3. sections of chain may twist into helix or fold into a pleated sheet giving proteins strength and stability
tertiary structure of peptide bonds
polypeptide tangles
1. long polypeptide chains twist and fold into variety of complex tangles shapes
2. side groups may attract or repel each other (hydrophilic or phobic)
3. disulfide bridges determine tertiary structure
4. shape gives characteristics
hydrophilic side groups
on the surface of water
- “water loving”
hydrophobic side groups
are hidden in the middle
- “water fearing”
quaternary structures of peptide bonds
multiple polypeptide interactions
1. interactions between 2 or more polypeptides
2. some polypeptides work together in large complexes (
2. some protein strands function alone while other proteins are composed of several strands
variety of proteins
proteins perform different tasks dictated by shape
1. globular proteins are water soluble (proteins of blood)
2. some proteins form hollow balls (carry are store material in interior)
3. some proteins are much longer than wide (proteins of tendons)
collagen
a protein from which connective tissues are made
- tendons, ligaments, scars and foundations of bones and teeth
- acts like glue between cells
insulin
helps regulate blood sugar
enzymes
protein catalysts
- all enzymes=proteins
catalyst
substance that facilitates a chemical reaction without itself being altered in the process
inherited amino acid sequences
for each protein there exists a standard aa sequence
- sequence is specified by heredity
- wrong aa can be disastrous to health
sickle-cell disease
- inherited variation in aa sequence - abnormal hemoglobin
- one aa in a critical position has been replaced by a different one
genetic expression and the nutrients
- every human cell nucleus contains DNA for making every protein
- cells monitor nutrient concentrations in fluids surrounding them and triggers a cascade of molecular events leading to expression or suppression of certain genes
denaturation
the irreversible change in a protein’s shape
- caused by heat, acids, bases and alcohols
what is denaturation important for?
digestion of food protein
- stomach acids open-up a proteins structure
- allows digestive enzymes to make contact with the peptide bond and cleave them
denaturing proteins due to cooking
a protein that binds both biotin and iron is denatured, liberating them for digestion
- without cooking some things you will be biotin and iron deficient
ex. changes that occur to egg white when an egg is cooked
digestion of proteins
- certain acid-tolerant proteins, digest proteins from food that have been denatured by acid
- coating of mucus secreted by stomach wall protects its proteins from attack by either acids or enzymes
what is the normal acid of the stomach?
PH about 2
- no food is acidic enough to make it stronger
digestion of proteins in the mouth
protein is crushed by chewing and is moistened with saliva
digestion of protein in the stomach
- acid helps to uncoil the protein’s tangled strands so that the stomach’s protein-digesting enzyme (pepsin) can attach the peptide bonds
- lining is protected from acid and enzymes by a mucus coating secreted by stomach cells
pepsin
the stomachs protein-digesting enzyme
- works best in an acidic environment
- breaks down protein chains in the stomach
- cleaves aa strands into polypeptides and a few aa
digestion of proteins in the SI
receives small denatured pieces of protein from stomach
- most are polypeptides, but a few are single aa
***where most protein digestion occurs
alkaline juices
released from the pancreas
- neutralize the acid delivered by the stomach
- pH increased to about 7 (neutral)
proteases
protein-digesting enzymes from the pancreas and SI continue to break down protein until nearly all that is left are dipeptides, tripeptides or single aa
what pH do enzymes work best in?
neutral pH (7)
single amino acid supplements
may compete for absorption sites or overwhelm a carrier resulting in possible deficiency in another aa
cells along the SI
absorb single aa
1. have enzymes on their surfaces that split most tripeptides and dipeptides into single aa, which are then absorbed
2. some di- and tripeptides are absorbed into cells where they are split into single aa before being released into bloodstream
larger peptide molecules
a few larger peptide molecules can escape the digestive process altogether and enter the bloodstream intact
- this may give information about external environment
- may stimulate an immune response and have a potential role in food allergies
amino acids in the bloodstream
- carried to liver
- used by liver or released into blood to be taken up by other cells
amino acids in the liver
used in…
1. protein synthesis
2. synthesize a nonessential aa and released into bloodstream for cells
amino acids in the cells
used for…
1. make proteins for their own use
2. make proteins that are released into lymph of blood for other uses
3. when neccessary, body cells use aa for energy
roles of proteins in the body
- supporting growth and maintenance
- building enzymes, hormones and other compounds
- maintaining fluid and electrolyte balance
- maintaining acid-base balance
- clotting of blood
- providing energy and glucose
proteins supporting growth and maintenance
- build proteins of new tissue (embryo, scar tissue, new hair and nails, etc.)
- protein helps replace worn-out cell structures
- red blood cells live only 3-4 months
- cells lining intestinal tract live only 3 days
- skin cells are constantly being shed and replaced
hormones
chemical messengers secreted by a number of body organs in response to conditions that require regulation
- each has a specific organ or tissue and elicits a specific response
- some are made from aa (proteins)
tyrosine
component of both epinephrine and norepinephrine, and is used to make both melanin and throxine
tryptophan
starting material for serotonin and niacin
antibodies
produced by the immune system
- large proteins of the blood
proteins maintaining fluid and electrolyte balance
- too much fluid in a cell = cell ruptures
- too little fluid in a cell = cell is unable to function
- cells retain fluid needed by maintaining internal proteins
- fluid is kept within blood vessels by proteins that are too large to freely move across capillary walls
water in cell vs protein
water can diffuse freely into and out of cells
- protein cannot diffuse freely, and proteins attract water
large proteins and fluid
the large proteins attract and hold water within the vessels, preventing water from freely flowing into spaces between cells
maintaining acid-base balance
proteins are important to maintain this balance
acids
compounds that release hydrogens
bases
compounds that accept hydrogens
what acts as buffers to maintain blood pH?
blood proteins
- protein buffers pick up hydrogens when there are too many in the bloodstream
- they release hydrogens when there are too few in the bloodstream
acidosis
- condition of excess acid in the blood
- below-normal pH
alkalosis
- condition of excess base in the blood
- above-normal pH
acidosis and alkalosis
can cause coma or death
- proteins can be denatured, disrupting many body processes
clotting of blood
special proteins provide the netting on which blood clots are built
proteins providing energy and glucose
when insufficient carbs and fat = energy provided
what ways can an amino acid that arrives at a cell be used?
- used to build part of a growing protein
- altered to make another needed compound
- dismantled to use its amine group to build another amino acid
what can the remainder of amino acids be used for?
fuel or converted to glucose or fat
what happens if the cell is starved for energy and is lacking glucose and fatty acids?
- the amine group will be removed and the remainder used for energy
- amine group will ultimately be excreted as urine
what happens if the body has a surplus of amino acids and energy?
- the amino group will be excreted
- remainder can be used for energy or converted to glucose or fat for storage
wasted amino acids
amino acids not used to build protein of make other nitrogen containing compounds
when can we say amino acids are being wasted?
- the body does not have enough energy from other sources
- has more protein than it needs (extra protein = excess energy or stores of fat)
- has too much of any single aa, such as from a supplement
- diet supplies protein of low quality, with too few essential amino acids
how do you prevent wasting of amino acids and permit the synthesis of needed body protein?
- dietary protein must be adequate in quality
- diet must supply all the essential aa in proper amounts
- enough energy-yielding carbs and fat must be present (protein sparing)
protein sparing
when taking in enough energy from carbs and fats we are SPARING PROTEINS
what does the body’s response to protein depend on?
- the body’s state of health
- other nutrients and energy taken with the protein
- the protein’s quality
state of health
malnutrition (undernutrition) and infection may greatly increase need for protein
undernutrition of proteins
secretion of digestive enzymes slows as the tract’s lining degenerates
infection and proteins
extra protein is needed for enhanced immune function
protein quality
determines how well a diet supports the growth of children and health of adults
2 things that influences how well a diet support child growth and health of children
- a proteins digestibility
- a proteins amino acid composition
digestibility
varies from food to food
- animal sources are more easily digested and absorbed than those from plant sources
digestibility of animal sources
90+% digested and absorbed
digestibility of legumes
80-90% digested and absorbed
digestibility of grains and other plant foods
70-90% digested and absorbed
high-quality proteins
dietary proteins containing all of the essential aa in relatively the same amounts that human beings require
- may also contain nonessential aa (not as important cause we can make them)
example of high-quality proteins
an egg
amino acid composition
cells need a full array of aa from food, their own aa pool, or from both
amino acid pool
amino acids dissolved in the body’s fluids that provide cells with ready raw materials from which to build new proteins or other molecules
nonessential amino acids
if not available from food, the cell can synthesize it and continue attaching aa to the protein strand being manufactured
what happens if the diet fails to supply enough of an essential amino acid?
- cells begin to adjust their activities
- within a single day of restricted essential aa intake, cells conserve it
2 ways cells conserve essential amino acid intake
- limiting breakdown of their working proteins
- reducing their use of amino acids for fuel
what can limiting amino acids do?
limit protein synthesis
- an essential aa present in dietary protein in an insufficient amount limits the body’s ability to build protein
- lack of availability will slow protein synthesis
***normal protein-related activities resume when limiting aa is available
what happens when the shortage of amino acids is chronic?
cells begin to break down their protein-making machinery
- when protein intake becomes adequate, protein synthesis will lag until the protein-making machinery can be rebuilt
- until then, cells function less and less efficiently
example of limiting amino acids
when you cant make a protein due to limiting amino acids, the machinery shuts down
you are out of eggs (limiting aa) so you cannot make muffins (protein), so the oven is not used
what happens to partially completed proteins?
they are not kept for completion later
1. they are dismantled and the aa are returned to circulation (available to the other cells)
2. if they’re not soon used for protein synthesis, they are stripped of their amine group and the residue is used for other purposes
complementary proteins
2 or more proteins whose aa assortments complement each other in such a way that the essential aa missing from one are supplied by the other = a complete protein
- doesn’t need to be in the same meal
mutual supplementation (complementary proteins)
strategy of combining 2 incomplete protein sources so that the amino acids in one food make up for those lacking in the other food
DRI committee recommendations for protein
depends on size: larger people have a higher protein need
adults: 0.8g/kg body weight/day RDA
- 10-35% of total calories AMDR
- recommends a combination of plant and animal protein
why may athletes need more protein?
because they eat more kcal
nitrogen balance
amount of nitrogen consumed compared with the amount excreted in a given time period
nitrogen in healthy adults, under normal circumstances
in nitrogen equilibrium = zero balance
- nitrogen in = nitrogen out
positive nitrogen balance or status
nitrogen in > nitrogen out
negative nitrogen balance or status
nitrogen in < nitrogen out
positive nitrogen balance explained
- more protein is synthesized by the body than is degraded
- nitrogen intake exceeds excretion
ex. healthy growing children, pregnant women, people recovering from protein deficiency
negative nitrogen balance explained
- body degrades more protein than it synthesizes
- body loses nitrogen as it breaks down muscle and other body proteins
ex. starving or severe stresses (burns, injuries, infections and fever)
protein-energy undernutrition (PEU, PEM)
- most widespread malnutrition problem
- includes marasmus and kwashiorkor and states in which they overlap
PCM and PEU
PCM: protein-calorie malnutrition
PEU: protein energy undernutrition
marasmus
chronic inadequate food intake
1. shrivelled and lean all over
2. inadequate energy, vitamin, mineral and protein intake
kwashiorkor
severe acute malnutrition
1. swollen belly and skin rash
- edema and inflammation of liver due to fat not being taken out
2. too little energy and protein to support body functions
consequences of marasmus
- child is thin with almost no adipose tissue
- muscles including heart, waste and weaken
- growth stopped
- brain development stunned and learning is impaired
- metabolism is slow so body temperature is subnormal
- digestive enzymes in short supply
- digestive tract lining deteriorates and absorption fails
cause of kwashiorkor
baby is weaned from breast milk when the next child is born
- go from breast milk (high-quality protein) to watery cereal (low in protein and low quality)
symptoms of kwashiorkor
resemble those of marasmus with less severe wastings of body fat and presence of edema
1. proteins and hormones that previously maintained fluid balance are diminished
2. fluid leaks out of blood and accumulates in the belly and legs
3. belly bulges with a fatty liver
PEU (PEM) in canada
- poverty or unaffordable food costs
- some elderly people
- children and adults with homelessness
- anorexia nervosa
- cancer
- addiction to drugs and alcohol
- infants and toddlers replacing milk
PEU (PEM) and serious illness
treating PEU often reduces medical complications and suffering even when the underlying disease is untreatable
(PEU and serious illness worsen each other)
hungry children
- do not learn as well as fed children
- are not as competitive
- are ill more often
- have higher absentee rates from school and cannot concentrate longs
overconsumption of proteins
- no health benefits
- may pose health risks
- heart, kidneys and bones
diets high in protein-rich foods
- protein is satiating
- protein has highest thermic effect of food
- animal protein sources can be high in saturated fat
animal protein sources in the diet
can be high in saturated fat
1. may increase LDL cholesterol
2. effect of animal protein on heart health is uncertain
***substituting plant protein for animal protein improves indicators of heart disease risk
risk of a high-protein diet
can worsen existing kidney problems and may accelerate a decline in only mildy impaired kidneys (controlled protein diet)
what people typically consume more than enough protein?
people living in developed nations
protein-rich foods
- contribute an abundance of high-quality protein (protein group - milk, meat)
- contribute smaller amounts of protein that can add up to significant qualities (veggies, grains)
foods rich in protein carry what vitamins and minerals?
vitamin B12 and iron
- tend to lack vitamin C and folate
although protein is critical in nutrition, what is the problem with eating too many protein-rich foods?
can displace other important foods from the diet
what are legumes excellent sources of?
- many B vitamins
- iron
- calcium
what do legumes lack?
- vitamin A
- vitamin C
- vitamin B12
problem heavy use of soy bean products in place of meat?
inhibits iron absorption
- improve iron absorption with small amounts of meat and/or foods rich in vitamin C
convenience foods (vegetarians)
food made from texturized vegetable protein (soy protein)
- can be formulated to look and taste like meat, fish, poultry but fall short on nutrition content (processed)
tofu (bean curd)
often rich in calcium and have a variable fat content
omnivore
includes food of both plants and animal origin
lacto-ovo vegetarian
includes dairy products and eggs but excludes animal flesh and seafood
lacto-vegetarian
includes dairy products but excluded eggs, animal flesh, and seafood
ovo-vegetarian
includes eggs, but excludes milk products, animal flesh and seafood
pesco-vegetarian
excludes animal flesh but eats seafood
- pescatarian, pescetarian, pescotarian
vegan
includes only food from plant sources and excludes all food from animal sources - also called a strict vegetarian
flexitarian
includes primary plant-based foods but animal products such as meat and fish are eaten occasionally
reasons for vegetariansim
- preference
- convenience
- advertising
- availability
- economy
- emotional comfort
- habit
- positive associations
- values or beliefs
- social pressure
outcomes for those who eat well-planned vegetarian diets (in affluent countries)
- decreased obesity rates
- decreased heart disease rates
- decreased high BP rates
- decreased cancer rates
- increased life span
positive health aspects of vegetarian diets
reduced incidences of chronic diseases
- consume more fruits and veggies
- more fibre, potassium, and vitamins
- smoke less, less alcohol more PA
vegetarian diets and weight control
- higher body weights with mixed diet compared to vegetarians
- weight increases as frequency of meat consumption increases
what is lower body weight correlated with?
- high fibre intakes
- low fat intakes
vegetarian diets and heart disease
- die less often from heart disease and related illnesses
- lower in saturated fats and cholesterol than mixed diets
- higher in dietary fibre
4.lower disease risk due to phytochemicals
soy protein replacing animal protein benefit
reduces…
1. total blood cholesterol
2. LDL cholesterol
3. triglycerides
4. BP
vegetarian diets and BP
lower BP and lower rates of HTN (hypertension)
diet influences of BP
high in fibre, fruits and veggies
lifestyle factors influencing BP
- appropriate body weight
- smoking and alcohol intake raise BP
- PA lowers BP
vegetarian diets and defense against cancer
significantly lower rates of some caners (maybe due to abundance of fruits and veggies)
colon cancer
correlates with moderate-to-high intakes of:
1. alcohol
2. total food energy
3. fatty red meats and processed meats (but not poultry or fish)
what do the healthiest meat eaters base their diets on?
- abundant veggies, fruits, whole grains and milk products
- small servings of fish, poultry and meat
extreme meat lovers and misguided weight-loss dieters
- eliminate many fruits, veggies and grains
- risk of nutrient deficiencies and increased chronic disease risk
what are poorly planned vegetarian diets at risk of?
inadequate…
1. protein
2. iron
3. zinc
4. calcium
5. vitamin B12
6. vitamin D
7. omega-3s
what are poorly planned vegetarian diets at risk of?
insufficient…
1. vitamin A
2. vitamin C
3. folate
4. fibre
RDA for protein
same for vegetarians as for others
- vegetarians who use animal-derived foods get high quality proteins and likely meet needs
iron
can be a problem even for meat eaters
1. iron in plant foods is poorly absorbed
2. absorption of iron from plants (non-heme iron) is enhanced by vitamin C consumed with iron-rich foods
DRI committee recommendations for iron in vegetarians
iron intake for vegetarians be increased to 1.8x the general RDA
zinc
similar to iron in that meat is it s richest source
1. zinc from plant sources is not well absorbed
2. can be a problem for growing children
3. few vegetarian adults are zinc deficient
what interfered with zinc absorption?
soy
how can a vegetarian meet zinc needs?
- eat a variety of nutrient-dense foods
- maintain an adequate energy intake
- include whole grains, nuts, legumes
calcium
- with milk products- similar intake to general pop.
- without milk products - risk inadequacy
calcium rich-foods
calcium-fortified juices, soy beverages, yogurt
- sources of calcium should be varied because calcium absorption from some plant sources is limited
plant-sources of calcium
- figs
- some legumes
- broccoli
- turnip greens
- some nuts and seeds
vitamin B12
requirement is small, but significant amounts are found ONLY in animal-derived foods
- vegans must rely on B12-fortified foods or supplements
vitamin D
- animal foods such as milk and butter are fortified
- margarine and some
3 milk alternatives are fortified - fatty fish are sources of vitamin D
when may vitamin D supplements be needed?
- if vitamin D fortified foods are not used
- limited sun exposure
vegetarian diet and omega-3 fatty acids
vegetarian diets typically provide enough omega-6 fatty acids but often lack omega-3 fatty acids
- should include good sources of linolenic acid cause it is an essential nutrient
what does imbalance of omega-3 and omega-6 fatty acids cause?
slows production of EPA and DHA
planning a good vegetarian diet
- choose fresh, whole foods
- avoid reliance on heavily processed convenience foods that contain added sugars, salt, saturated fats and trans fat
- dark green veggies and legumes help meet iron and zinc needs
- select fortified foods or use supplements to ensure adequate intakes of vitamin B12, vitamin D and calcium
- soy beverages and tofu fortified with vitamin B12, vitamin D and calcium can substitute for cow’s milk products
