NUTR 2105 Lecture Notes - Lecture 6: Essential Amino Acid, Amine, Peptide
1 May 2018
School
Department
Course
Professor
All enzymes made of proteins but only some hormones made of proteins
-
Proteins made up of chain of amino acids made based on individual's DNA
Structurally different than carbs and lipids
Excess dietary protein cannot be stored in body, but broken down
and stored as fat
§
Building blocks of proteins are amino acids
20 amino acids
□
Proteins classified by number of amino acids in the chain
Peptides: fewer than 50 amino acids
Dipeptides: 2 amino acids
◊
Tripeptides: 3 amino acids
◊
Polypeptides: more than 10 amino acids
◊
®
Proteins: more than 50 amino acids
Typically 100 to 10,00 amino acids linked together
◊
®
□
Anatomy of an amino acid
Amine group (NH2), carboxylic acid group (COOH), and
side chain (R group)
®
Side chains used to identify them
Essential, Nonessential, and Conditional Amino
Acids
◊
®
□
Peptide bonds
Form when C of acid group of one amino acid joins w/
the N atom of the amino group of second amino acid
®
Formed through condensation
®
Broken through hydrolysis
®
□
§
○
Organization and Shape of Proteins Affect their Function
4 levels of structure:
Primary structure: amino acids are linked together to form a
simple linear chain
□
Secondary structure: geometric shape of protein that is folded
and twisted
□
Tertiary structure: 3D globular shape of a protein
□
Quaternary structure: 2/ more polypeptide chains bond
together
□
§
Denaturation of Proteins Changes Their Shape
Denaturation(unfolding) of proteins when:
Heat
®
Acids
®
Bases
®
Salts
®
Mechanical agitation
®
□
Altering shape of protein alters its function□
Primary structure is unchanged by denaturing□
§
○
-
Digesting and Absorbing Protein
Begins in stomach
Bolus enters stomach
Gastrin stimulates release of HCl□
HCl denatures protein and converts pepsinogen to pepsin□
Pepsin breaks polypeptides into shorter chains□
§
○
Digestion continues in small intestine
Polypeptides enter small intestine and are broken into smaller
peptides
Cholecystokinin (CCK) stimulates release of proteases by
pancreas
□
Proteases break apart the polypeptides to tripeptides and
tripeptides and dipeptides
□
Dipeptidases and tripeptidases break the dipeptides and
tripeptides into amino acids
□
§
○
Amino acid absorption
Amino acids are absorbed into small intestine
§
Amino acids are transported to liver from intestines via portal vein
§
In liver, amino acids are:
Used to synthesize new proteins□
Converted to energy, glucose, or fat□
Released to bloodstream and transported to cells throughout
the body
□
§
Occasionally proteins are absorbed intact
§
○
How amino acids are metabolized
Liver metabolizes amino acids, depending on bodily needs
Most amino acids sent into blood to be picked up and used by
cells
□
If diet is low in carbs, amino acids converted into glucose
(gluconeogenesis)
□
§
Amino acid pools supply the body's ongoing need for protein
synthesis
Body breaks down and makes protein daily to maintain body
structures such as tissues and organs
□
Amino acid pools provide a ready supply of amino acids the
body uses to create proteins on demand
□
Extra protein is used to help the body heal if a person has
excessive wounds
□
Protein turnover is the process of degrading and synthesizing
proteins
More than 200 grams of protein is turned over daily
®
□
§
○
Protein Synthesis is Regulated by Genes
3 steps to protein synthesis:
Transcription: info about building or repairing old is stored in
DNA. When a new polypeptide chain is needed, an inverse
copy of the DNA is generated forming messenger RNA
(mRNA)
□
Translation: mRNA binds to ribosome. Code on mRNA is
"read" by transfer RNA (tRNA) brings a specific amino acids to
the ribosome, based on the code
□
Elongation: translation process continues as amino acids are
collected by tRNA and brought to the ribosomes to build a
chain in the proper sequence, continuing until the sequence is
finished and the new protein is released
□
§
Sickle-cell anemia is a common blood disorder that involves an
abnormal or flawed protein formation
§
○
Deamination Removes the Amine Group from Amino Acids ** precursor
to ch. 8
When the amino acid pool reaches capacity, the amino acids are
broken down to their component parts for other uses
§
Deamination occurs when the amine group is removed from the
amino acid. Ammonia is formed
§
Ammonia is converted to urea in the liver. Urea is subsequently
excreted in the urine
§
Carbon-containing remnants are:
Converted to glucose, if they are glucogenic (prefer to make
glucose) amino acids, through glucogeneogeneis
□
Converted to fatty acids and stored as triglycerides in adipose
tissue
□
Oxidized for energy via metabolic pathways□
§
○
Nonessential Amino Acids are Synthesized through Transamination
Transamination is the process of forming nonessential amino acids
by transferring the nitrogen from one amino acid to a keto acid to
form a new nonessential amino acid
§
○
How is Protein Metabolized? (skipped over this in class)
Protein can be used for gluconeogenesis
If too few carbs consumed□
§
Excess proteins converted to fatty acids and stored as triglycerides
in adipose tissue
§
If too few cals consumed, protein oxidized for energy
§
○
-
Function of Protein in Body
Provide structural support (ex. Collagen) and enable movement (ex. Actin
and myosin)
○
Act as a catalyst
Enzymes speed up reactions
§
○
Act as a chemical messenger
Hormones (not all are protein, some are made of fat) regulate cell
actions
§
○
Regulate fluid balance
○
Help maintain acid-base balance
○
Transport substances throughout the body
Transport proteins shuttle oxygen; waste products; lipids; some
vitamins, Na, and K through the blood and cell membranes
§
Contribute to a healthy immune system
Antibodies are proteins that bind and neutralize pathogens
that would harm the body
□
§
Provide energy
4 cals/ gram□
§
Improve satiety and appetite control
§
○
-
How Much Protein Do You Need Daily?
Healthy adults should be in nitrogen balance
Should consume enough to replace what is used every day
§
Individuals in positive nitrogen balance
Pregnant woman, people recovering from surgery or injury,
and growing children
□
Should consume enough to build new tissue□
§
Individuals in negative nitrogen balance
Immediately after surgery, fighting an infection, or severe
emotional trauma
□
Need to consume enough cals and proteins to meet demand□
§
○
Protein intake recommendations, MASTERING WILL ASK TO CALCULATE
RDA: 0.8 g/kg daily for adults
§
ADMR: 10-35% of daily cals
§
Overweight individuals' needs are not much greater than normal-
weight individuals for similar height
§
○
American College of Sports Medicine, the Academy of Nutrition and
Dietetics, and other experts advocate:
50-100% more protein for competitive athletes participating in
endurance or resistance exercise
§
○
Protein requirements for sports:
Recreational exercisers: 0.8-1.5g/kg
§
Endurance athletes: 1.2-1.4g/kg
§
Resistance and strength trained: 1.6-1.7g/kg
§
Limit to the rate at which the body can build muscle
§
No evidence of increase in gains when consuming over 2g/kg is
approx 1g/lb
§
○
-
Best Sources of Protein?
Not all protein is created equal
High-quality protein
Is digestible□
Contains all essential amino acids□
Provides sufficient protein to synthesize nonessential amino
acids
□
§
○
Several methods have been developed to determine the protein quality of
foods
Amino acid score
Composition of essential amino acids of a protein compared
w/ a standard, usually egg protein
□
§
Protein digestibility corrected amino acid score (PDCAAS)
Includes the digestibility of the protein and the amino acid
score
□
Used by the FDA to determine the % DV of proteins in a
serving of food
□
§
Biological value
How quickly the N from the absorbed protein is synthesized
into body protein
□
§
Complementary and complete proteins
Complete proteins
Contain all 9 essential amino acids
®
Usually animal sources are complete proteins
Exception: soy protein
◊
®
Are considered high quality
®
□
Incomplete proteins
One or more missing or incomplete essential amino
acid, referred to as limiting amino acids
®
Usually plant sources
®
□
Complementary proteins
Combining an incomplete protein w/ a food that
supplies the limiting amino acids (ex. Combining grains
and legumes)
®
□
§
○
Eggs, meat, fish, soy, and dairy contain significant amounts of protein
○
A 3-oz serving of cooked meat, poultry, or fish:
Provides 21-25 g's of protein
§
Provides about 7 g's of protein/ oz.
§
Is about the size of a deck of cards
§
Is an adequate amount for one meal
§
○
Eating a wide variety of foods is the best approach to meeting protein
needs
○
Taking protein supplements is/can be convenient, but is not necessary
and generally not recommended
○
FOR MASTERING: WHICH HAS A NEGLIGABLE AMOUNT OF PROTEIN?
FRUIT (basically fruit doesn't have protein)
○
What if too much or too little protein?
Too much protein:
May increase risk for heart disease
High intake of protein sources w/ high saturated fat
®
Choose a variety of plant sources to reduce risk of heart
disease
®
□
Increases risk for kidney stones
A diet high in animal protein and low in carbs lowers
urine pH, which can raise risk of developing kidney
stones
®
□
Increases risk for osteoporosis
If high protein intake w/ low calcium intake can lead to
increased urinary Ca losses
®
High-protein diets w/ adequate Ca (esp via dairy
sources) protect bone
®
Too low protein can lead to bone loss in elderly men
and women
®
□
§
Too much emphasis on protein in a diet can displace other
nourishing, especially other equally important food choices from
diet like whole grains, fruit, and vegetables
§
Too little protein:
Protein-energy malnutrition (PEM)
Protein is used for energy rather than for its other
functions in the body
®
Other important nutrients are in short supply
®
More prevalent in infants and children
®
Types of PEM:
Kwashiorkor
Via severe protein density
}
Generally via diet high in grains
}
Bloated stomach
}
Symptoms include:
Edema in legs, feet, and stomach
–
Diminished muscle tone and strength
–
Brittle hair that is easy to pull out
–
A pale, said and apathetic appearance
–
Being prone to infection, rapid heart
rate, excess fluid in lungs, pnemonia,
septicemia, and water and electrolyte
imbalances
–
}
◊
Marasmus
Via severe deficiency in cals
}
Really skinny
}
Symptoms:
Frail emaciated appearance
–
Weakened and appear apathetic
–
Often cannot stand w/o support
–
Appears old beyond their years
–
Hair thin, dry, and lacks sheen
–
Low body temp and blood pressure
–
Prone to dehydration infections and
unnecessary blood clotting
–
}
◊
Marasmic kwashiorkor
Combo of chronic deficiency of cals AND
protein
Edema in legs and arms
–
A "skin and bones" appearance
–
w/ treatment, edema subsides and
appearance becomes more like
someone w/ marasmus
–
}
◊
®
Treatment for PEM
Medical and nutritional treatment can
dramatically reduce mortality rate
◊
Should be implemented carefully and slowly
Step 1: address life-threatening factors
Severe dehydration
–
Fluid and nutrient imbalances
–
}
Step 2: restore depleted tissue
Gradually provide nutritionally dense
cals and high-quality proteins
–
}
Step 3: transition to foods and introduce
physical activity
}
◊
®
□
Cells lining GI tract are not sufficiently replaced as they slough
off
□
Digestive function is inhibited□
Absorption of food is reduced□
Intestinal bacteria get into the blood and cause septicemia □
The immune system is compromised due to malnutrition and
cannot fight infection
□
§
○
Vegetarian diet
Reasons
Ethical □
Religious □
Environmental □
Health □
§
Vegetarians must consume adequate amounts of non-meat
proteins sources THROUGHOUT the day
§
It is NOT necessary to complement your proteins at every meal, just
w/in 24 hrs
§
Benefits of a healthy vegetarian diet include reduced risks of:
Heart disease□
High blood pressure□
Diabetes□
Cancer□
Stroke□
Obesity□
§
Potential risks of a vegetarian diet include low intake of key
nutrients:
Protein□
Ca□
Fe□
Vitamin B12□
Zn□
Vitamins A and D□
Omega-3 fatty acids (alpha-linoleic acids)□
§
Nutrients of Concern
Protein
Meet or exceed w/ balanced diet, adequate cals
®
□
Fatty acids
Higher intakes of ALA?
®
Algae based DHA supplements
®
□
Fe
1.8x as much iron as non-vegetarians
®
□
Zn
Similar to non-vegetarians
®
Soy, grains, legumes (soaking)
®
□
Ca
Lacto meet or exceed recommendations
®
Leafy greens: high content, low bioavailability
®
Non-dairy milk: similar bioavailability to cow's milk
®
□
B12
Only in foods of animal origin
®
Must be mindful of sources: supplements, fortified
foods
®
□
§
○
-
NUTR 2105 Chpt. 6 Proteins
Monday, February 12, 2018
2:27 PM
All enzymes made of proteins but only some hormones made of proteins
-
Proteins made up of chain of amino acids made based on individual's DNA
Structurally different than carbs and lipids
Excess dietary protein cannot be stored in body, but broken down
and stored as fat
§
Building blocks of proteins are amino acids
20 amino acids□
Proteins classified by number of amino acids in the chain
Peptides: fewer than 50 amino acids
Dipeptides: 2 amino acids
◊
Tripeptides: 3 amino acids
◊
Polypeptides: more than 10 amino acids
◊
®
Proteins: more than 50 amino acids
Typically 100 to 10,00 amino acids linked together
◊
®
□
Anatomy of an amino acid
Amine group (NH2), carboxylic acid group (COOH), and
side chain (R group)
®
Side chains used to identify them
Essential, Nonessential, and Conditional Amino
Acids
◊
®
□
Peptide bonds
Form when C of acid group of one amino acid joins w/
the N atom of the amino group of second amino acid
®
Formed through condensation
®
Broken through hydrolysis
®
□
§
○
Organization and Shape of Proteins Affect their Function
4 levels of structure:
Primary structure: amino acids are linked together to form a
simple linear chain
□
Secondary structure: geometric shape of protein that is folded
and twisted
□
Tertiary structure: 3D globular shape of a protein□
Quaternary structure: 2/ more polypeptide chains bond
together
□
§
Denaturation of Proteins Changes Their Shape
Denaturation(unfolding) of proteins when:
Heat
®
Acids
®
Bases
®
Salts
®
Mechanical agitation
®
□
Altering shape of protein alters its function
□
Primary structure is unchanged by denaturing
□
§
○
-
Digesting and Absorbing Protein
Begins in stomach
Bolus enters stomach
Gastrin stimulates release of HCl
□
HCl denatures protein and converts pepsinogen to pepsin
□
Pepsin breaks polypeptides into shorter chains
□
§
○
Digestion continues in small intestine
Polypeptides enter small intestine and are broken into smaller
peptides
Cholecystokinin (CCK) stimulates release of proteases by
pancreas
□
Proteases break apart the polypeptides to tripeptides and
tripeptides and dipeptides
□
Dipeptidases and tripeptidases break the dipeptides and
tripeptides into amino acids
□
§
○
Amino acid absorption
Amino acids are absorbed into small intestine
§
Amino acids are transported to liver from intestines via portal vein
§
In liver, amino acids are:
Used to synthesize new proteins
□
Converted to energy, glucose, or fat
□
Released to bloodstream and transported to cells throughout
the body
□
§
Occasionally proteins are absorbed intact
§
○
How amino acids are metabolized
Liver metabolizes amino acids, depending on bodily needs
Most amino acids sent into blood to be picked up and used by
cells
□
If diet is low in carbs, amino acids converted into glucose
(gluconeogenesis)
□
§
Amino acid pools supply the body's ongoing need for protein
synthesis
Body breaks down and makes protein daily to maintain body
structures such as tissues and organs
□
Amino acid pools provide a ready supply of amino acids the
body uses to create proteins on demand
□
Extra protein is used to help the body heal if a person has
excessive wounds
□
Protein turnover is the process of degrading and synthesizing
proteins
More than 200 grams of protein is turned over daily
®
□
§
○
Protein Synthesis is Regulated by Genes
3 steps to protein synthesis:
Transcription: info about building or repairing old is stored in
DNA. When a new polypeptide chain is needed, an inverse
copy of the DNA is generated forming messenger RNA
(mRNA)
□
Translation: mRNA binds to ribosome. Code on mRNA is
"read" by transfer RNA (tRNA) brings a specific amino acids to
the ribosome, based on the code
□
Elongation: translation process continues as amino acids are
collected by tRNA and brought to the ribosomes to build a
chain in the proper sequence, continuing until the sequence is
finished and the new protein is released
□
§
Sickle-cell anemia is a common blood disorder that involves an
abnormal or flawed protein formation
§
○
Deamination Removes the Amine Group from Amino Acids ** precursor
to ch. 8
When the amino acid pool reaches capacity, the amino acids are
broken down to their component parts for other uses
§
Deamination occurs when the amine group is removed from the
amino acid. Ammonia is formed
§
Ammonia is converted to urea in the liver. Urea is subsequently
excreted in the urine
§
Carbon-containing remnants are:
Converted to glucose, if they are glucogenic (prefer to make
glucose) amino acids, through glucogeneogeneis
□
Converted to fatty acids and stored as triglycerides in adipose
tissue
□
Oxidized for energy via metabolic pathways□
§
○
Nonessential Amino Acids are Synthesized through Transamination
Transamination is the process of forming nonessential amino acids
by transferring the nitrogen from one amino acid to a keto acid to
form a new nonessential amino acid
§
○
How is Protein Metabolized? (skipped over this in class)
Protein can be used for gluconeogenesis
If too few carbs consumed□
§
Excess proteins converted to fatty acids and stored as triglycerides
in adipose tissue
§
If too few cals consumed, protein oxidized for energy
§
○
-
Function of Protein in Body
Provide structural support (ex. Collagen) and enable movement (ex. Actin
and myosin)
○
Act as a catalyst
Enzymes speed up reactions
§
○
Act as a chemical messenger
Hormones (not all are protein, some are made of fat) regulate cell
actions
§
○
Regulate fluid balance
○
Help maintain acid-base balance
○
Transport substances throughout the body
Transport proteins shuttle oxygen; waste products; lipids; some
vitamins, Na, and K through the blood and cell membranes
§
Contribute to a healthy immune system
Antibodies are proteins that bind and neutralize pathogens
that would harm the body
□
§
Provide energy
4 cals/ gram□
§
Improve satiety and appetite control
§
○
-
How Much Protein Do You Need Daily?
Healthy adults should be in nitrogen balance
Should consume enough to replace what is used every day
§
Individuals in positive nitrogen balance
Pregnant woman, people recovering from surgery or injury,
and growing children
□
Should consume enough to build new tissue□
§
Individuals in negative nitrogen balance
Immediately after surgery, fighting an infection, or severe
emotional trauma
□
Need to consume enough cals and proteins to meet demand□
§
○
Protein intake recommendations, MASTERING WILL ASK TO CALCULATE
RDA: 0.8 g/kg daily for adults
§
ADMR: 10-35% of daily cals
§
Overweight individuals' needs are not much greater than normal-
weight individuals for similar height
§
○
American College of Sports Medicine, the Academy of Nutrition and
Dietetics, and other experts advocate:
50-100% more protein for competitive athletes participating in
endurance or resistance exercise
§
○
Protein requirements for sports:
Recreational exercisers: 0.8-1.5g/kg
§
Endurance athletes: 1.2-1.4g/kg
§
Resistance and strength trained: 1.6-1.7g/kg
§
Limit to the rate at which the body can build muscle
§
No evidence of increase in gains when consuming over 2g/kg is
approx 1g/lb
§
○
-
Best Sources of Protein?
Not all protein is created equal
High-quality protein
Is digestible□
Contains all essential amino acids□
Provides sufficient protein to synthesize nonessential amino
acids
□
§
○
Several methods have been developed to determine the protein quality of
foods
Amino acid score
Composition of essential amino acids of a protein compared
w/ a standard, usually egg protein
□
§
Protein digestibility corrected amino acid score (PDCAAS)
Includes the digestibility of the protein and the amino acid
score
□
Used by the FDA to determine the % DV of proteins in a
serving of food
□
§
Biological value
How quickly the N from the absorbed protein is synthesized
into body protein
□
§
Complementary and complete proteins
Complete proteins
Contain all 9 essential amino acids
®
Usually animal sources are complete proteins
Exception: soy protein
◊
®
Are considered high quality
®
□
Incomplete proteins
One or more missing or incomplete essential amino
acid, referred to as limiting amino acids
®
Usually plant sources
®
□
Complementary proteins
Combining an incomplete protein w/ a food that
supplies the limiting amino acids (ex. Combining grains
and legumes)
®
□
§
○
Eggs, meat, fish, soy, and dairy contain significant amounts of protein
○
A 3-oz serving of cooked meat, poultry, or fish:
Provides 21-25 g's of protein
§
Provides about 7 g's of protein/ oz.
§
Is about the size of a deck of cards
§
Is an adequate amount for one meal
§
○
Eating a wide variety of foods is the best approach to meeting protein
needs
○
Taking protein supplements is/can be convenient, but is not necessary
and generally not recommended
○
FOR MASTERING: WHICH HAS A NEGLIGABLE AMOUNT OF PROTEIN?
FRUIT (basically fruit doesn't have protein)
○
What if too much or too little protein?
Too much protein:
May increase risk for heart disease
High intake of protein sources w/ high saturated fat
®
Choose a variety of plant sources to reduce risk of heart
disease
®
□
Increases risk for kidney stones
A diet high in animal protein and low in carbs lowers
urine pH, which can raise risk of developing kidney
stones
®
□
Increases risk for osteoporosis
If high protein intake w/ low calcium intake can lead to
increased urinary Ca losses
®
High-protein diets w/ adequate Ca (esp via dairy
sources) protect bone
®
Too low protein can lead to bone loss in elderly men
and women
®
□
§
Too much emphasis on protein in a diet can displace other
nourishing, especially other equally important food choices from
diet like whole grains, fruit, and vegetables
§
Too little protein:
Protein-energy malnutrition (PEM)
Protein is used for energy rather than for its other
functions in the body
®
Other important nutrients are in short supply
®
More prevalent in infants and children
®
Types of PEM:
Kwashiorkor
Via severe protein density
}
Generally via diet high in grains
}
Bloated stomach
}
Symptoms include:
Edema in legs, feet, and stomach
–
Diminished muscle tone and strength
–
Brittle hair that is easy to pull out
–
A pale, said and apathetic appearance
–
Being prone to infection, rapid heart
rate, excess fluid in lungs, pnemonia,
septicemia, and water and electrolyte
imbalances
–
}
◊
Marasmus
Via severe deficiency in cals
}
Really skinny
}
Symptoms:
Frail emaciated appearance
–
Weakened and appear apathetic
–
Often cannot stand w/o support
–
Appears old beyond their years
–
Hair thin, dry, and lacks sheen
–
Low body temp and blood pressure
–
Prone to dehydration infections and
unnecessary blood clotting
–
}
◊
Marasmic kwashiorkor
Combo of chronic deficiency of cals AND
protein
Edema in legs and arms
–
A "skin and bones" appearance
–
w/ treatment, edema subsides and
appearance becomes more like
someone w/ marasmus
–
}
◊
®
Treatment for PEM
Medical and nutritional treatment can
dramatically reduce mortality rate
◊
Should be implemented carefully and slowly
Step 1: address life-threatening factors
Severe dehydration
–
Fluid and nutrient imbalances
–
}
Step 2: restore depleted tissue
Gradually provide nutritionally dense
cals and high-quality proteins
–
}
Step 3: transition to foods and introduce
physical activity
}
◊
®
□
Cells lining GI tract are not sufficiently replaced as they slough
off
□
Digestive function is inhibited□
Absorption of food is reduced□
Intestinal bacteria get into the blood and cause septicemia □
The immune system is compromised due to malnutrition and
cannot fight infection
□
§
○
Vegetarian diet
Reasons
Ethical □
Religious □
Environmental □
Health □
§
Vegetarians must consume adequate amounts of non-meat
proteins sources THROUGHOUT the day
§
It is NOT necessary to complement your proteins at every meal, just
w/in 24 hrs
§
Benefits of a healthy vegetarian diet include reduced risks of:
Heart disease□
High blood pressure□
Diabetes□
Cancer□
Stroke□
Obesity□
§
Potential risks of a vegetarian diet include low intake of key
nutrients:
Protein□
Ca□
Fe□
Vitamin B12□
Zn□
Vitamins A and D□
Omega-3 fatty acids (alpha-linoleic acids)□
§
Nutrients of Concern
Protein
Meet or exceed w/ balanced diet, adequate cals
®
□
Fatty acids
Higher intakes of ALA?
®
Algae based DHA supplements
®
□
Fe
1.8x as much iron as non-vegetarians
®
□
Zn
Similar to non-vegetarians
®
Soy, grains, legumes (soaking)
®
□
Ca
Lacto meet or exceed recommendations
®
Leafy greens: high content, low bioavailability
®
Non-dairy milk: similar bioavailability to cow's milk
®
□
B12
Only in foods of animal origin
®
Must be mindful of sources: supplements, fortified
foods
®
□
§
○
-
NUTR 2105 Chpt. 6 Proteins
Monday, February 12, 2018 2:27 PM
All enzymes made of proteins but only some hormones made of proteins
-
Proteins made up of chain of amino acids made based on individual's DNA
Structurally different than carbs and lipids
Excess dietary protein cannot be stored in body, but broken down
and stored as fat
§
Building blocks of proteins are amino acids
20 amino acids□
Proteins classified by number of amino acids in the chain
Peptides: fewer than 50 amino acids
Dipeptides: 2 amino acids
◊
Tripeptides: 3 amino acids
◊
Polypeptides: more than 10 amino acids
◊
®
Proteins: more than 50 amino acids
Typically 100 to 10,00 amino acids linked together
◊
®
□
Anatomy of an amino acid
Amine group (NH2), carboxylic acid group (COOH), and
side chain (R group)
®
Side chains used to identify them
Essential, Nonessential, and Conditional Amino
Acids
◊
®
□
Peptide bonds
Form when C of acid group of one amino acid joins w/
the N atom of the amino group of second amino acid
®
Formed through condensation
®
Broken through hydrolysis
®
□
§
○
Organization and Shape of Proteins Affect their Function
4 levels of structure:
Primary structure: amino acids are linked together to form a
simple linear chain
□
Secondary structure: geometric shape of protein that is folded
and twisted
□
Tertiary structure: 3D globular shape of a protein□
Quaternary structure: 2/ more polypeptide chains bond
together
□
§
Denaturation of Proteins Changes Their Shape
Denaturation(unfolding) of proteins when:
Heat
®
Acids
®
Bases
®
Salts
®
Mechanical agitation
®
□
Altering shape of protein alters its function□
Primary structure is unchanged by denaturing□
§
○
-
Digesting and Absorbing Protein
Begins in stomach
Bolus enters stomach
Gastrin stimulates release of HCl□
HCl denatures protein and converts pepsinogen to pepsin□
Pepsin breaks polypeptides into shorter chains□
§
○
Digestion continues in small intestine
Polypeptides enter small intestine and are broken into smaller
peptides
Cholecystokinin (CCK) stimulates release of proteases by
pancreas
□
Proteases break apart the polypeptides to tripeptides and
tripeptides and dipeptides
□
Dipeptidases and tripeptidases break the dipeptides and
tripeptides into amino acids
□
§
○
Amino acid absorption
Amino acids are absorbed into small intestine
§
Amino acids are transported to liver from intestines via portal vein
§
In liver, amino acids are:
Used to synthesize new proteins□
Converted to energy, glucose, or fat□
Released to bloodstream and transported to cells throughout
the body
□
§
Occasionally proteins are absorbed intact
§
○
How amino acids are metabolized
Liver metabolizes amino acids, depending on bodily needs
Most amino acids sent into blood to be picked up and used by
cells
□
If diet is low in carbs, amino acids converted into glucose
(gluconeogenesis)
□
§
Amino acid pools supply the body's ongoing need for protein
synthesis
Body breaks down and makes protein daily to maintain body
structures such as tissues and organs
□
Amino acid pools provide a ready supply of amino acids the
body uses to create proteins on demand
□
Extra protein is used to help the body heal if a person has
excessive wounds
□
Protein turnover is the process of degrading and synthesizing
proteins
More than 200 grams of protein is turned over daily
®
□
§
○
Protein Synthesis is Regulated by Genes
3 steps to protein synthesis:
Transcription: info about building or repairing old is stored in
DNA. When a new polypeptide chain is needed, an inverse
copy of the DNA is generated forming messenger RNA
(mRNA)
□
Translation: mRNA binds to ribosome. Code on mRNA is
"read" by transfer RNA (tRNA) brings a specific amino acids to
the ribosome, based on the code
□
Elongation: translation process continues as amino acids are
collected by tRNA and brought to the ribosomes to build a
chain in the proper sequence, continuing until the sequence is
finished and the new protein is released
□
§
Sickle-cell anemia is a common blood disorder that involves an
abnormal or flawed protein formation
§
○
Deamination Removes the Amine Group from Amino Acids ** precursor
to ch. 8
When the amino acid pool reaches capacity, the amino acids are
broken down to their component parts for other uses
§
Deamination occurs when the amine group is removed from the
amino acid. Ammonia is formed
§
Ammonia is converted to urea in the liver. Urea is subsequently
excreted in the urine
§
Carbon-containing remnants are:
Converted to glucose, if they are glucogenic (prefer to make
glucose) amino acids, through glucogeneogeneis
□
Converted to fatty acids and stored as triglycerides in adipose
tissue
□
Oxidized for energy via metabolic pathways□
§
○
Nonessential Amino Acids are Synthesized through Transamination
Transamination is the process of forming nonessential amino acids
by transferring the nitrogen from one amino acid to a keto acid to
form a new nonessential amino acid
§
○
How is Protein Metabolized? (skipped over this in class)
Protein can be used for gluconeogenesis
If too few carbs consumed□
§
Excess proteins converted to fatty acids and stored as triglycerides
in adipose tissue
§
If too few cals consumed, protein oxidized for energy
§
○
-
Function of Protein in Body
Provide structural support (ex. Collagen) and enable movement (ex. Actin
and myosin)
○
Act as a catalyst
Enzymes speed up reactions
§
○
Act as a chemical messenger
Hormones (not all are protein, some are made of fat) regulate cell
actions
§
○
Regulate fluid balance
○
Help maintain acid-base balance
○
Transport substances throughout the body
Transport proteins shuttle oxygen; waste products; lipids; some
vitamins, Na, and K through the blood and cell membranes
§
Contribute to a healthy immune system
Antibodies are proteins that bind and neutralize pathogens
that would harm the body
□
§
Provide energy
4 cals/ gram□
§
Improve satiety and appetite control
§
○
-
How Much Protein Do You Need Daily?
Healthy adults should be in nitrogen balance
Should consume enough to replace what is used every day
§
Individuals in positive nitrogen balance
Pregnant woman, people recovering from surgery or injury,
and growing children
□
Should consume enough to build new tissue□
§
Individuals in negative nitrogen balance
Immediately after surgery, fighting an infection, or severe
emotional trauma
□
Need to consume enough cals and proteins to meet demand□
§
○
Protein intake recommendations, MASTERING WILL ASK TO CALCULATE
RDA: 0.8 g/kg daily for adults
§
ADMR: 10-35% of daily cals
§
Overweight individuals' needs are not much greater than normal-
weight individuals for similar height
§
○
American College of Sports Medicine, the Academy of Nutrition and
Dietetics, and other experts advocate:
50-100% more protein for competitive athletes participating in
endurance or resistance exercise
§
○
Protein requirements for sports:
Recreational exercisers: 0.8-1.5g/kg
§
Endurance athletes: 1.2-1.4g/kg
§
Resistance and strength trained: 1.6-1.7g/kg
§
Limit to the rate at which the body can build muscle
§
No evidence of increase in gains when consuming over 2g/kg is
approx 1g/lb
§
○
-
Best Sources of Protein?
Not all protein is created equal
High-quality protein
Is digestible□
Contains all essential amino acids□
Provides sufficient protein to synthesize nonessential amino
acids
□
§
○
Several methods have been developed to determine the protein quality of
foods
Amino acid score
Composition of essential amino acids of a protein compared
w/ a standard, usually egg protein
□
§
Protein digestibility corrected amino acid score (PDCAAS)
Includes the digestibility of the protein and the amino acid
score
□
Used by the FDA to determine the % DV of proteins in a
serving of food
□
§
Biological value
How quickly the N from the absorbed protein is synthesized
into body protein
□
§
Complementary and complete proteins
Complete proteins
Contain all 9 essential amino acids
®
Usually animal sources are complete proteins
Exception: soy protein
◊
®
Are considered high quality
®
□
Incomplete proteins
One or more missing or incomplete essential amino
acid, referred to as limiting amino acids
®
Usually plant sources
®
□
Complementary proteins
Combining an incomplete protein w/ a food that
supplies the limiting amino acids (ex. Combining grains
and legumes)
®
□
§
○
Eggs, meat, fish, soy, and dairy contain significant amounts of protein
○
A 3-oz serving of cooked meat, poultry, or fish:
Provides 21-25 g's of protein
§
Provides about 7 g's of protein/ oz.
§
Is about the size of a deck of cards
§
Is an adequate amount for one meal
§
○
Eating a wide variety of foods is the best approach to meeting protein
needs
○
Taking protein supplements is/can be convenient, but is not necessary
and generally not recommended
○
FOR MASTERING: WHICH HAS A NEGLIGABLE AMOUNT OF PROTEIN?
FRUIT (basically fruit doesn't have protein)
○
What if too much or too little protein?
Too much protein:
May increase risk for heart disease
High intake of protein sources w/ high saturated fat
®
Choose a variety of plant sources to reduce risk of heart
disease
®
□
Increases risk for kidney stones
A diet high in animal protein and low in carbs lowers
urine pH, which can raise risk of developing kidney
stones
®
□
Increases risk for osteoporosis
If high protein intake w/ low calcium intake can lead to
increased urinary Ca losses
®
High-protein diets w/ adequate Ca (esp via dairy
sources) protect bone
®
Too low protein can lead to bone loss in elderly men
and women
®
□
§
Too much emphasis on protein in a diet can displace other
nourishing, especially other equally important food choices from
diet like whole grains, fruit, and vegetables
§
Too little protein:
Protein-energy malnutrition (PEM)
Protein is used for energy rather than for its other
functions in the body
®
Other important nutrients are in short supply
®
More prevalent in infants and children
®
Types of PEM:
Kwashiorkor
Via severe protein density
}
Generally via diet high in grains
}
Bloated stomach
}
Symptoms include:
Edema in legs, feet, and stomach
–
Diminished muscle tone and strength
–
Brittle hair that is easy to pull out
–
A pale, said and apathetic appearance
–
Being prone to infection, rapid heart
rate, excess fluid in lungs, pnemonia,
septicemia, and water and electrolyte
imbalances
–
}
◊
Marasmus
Via severe deficiency in cals
}
Really skinny
}
Symptoms:
Frail emaciated appearance
–
Weakened and appear apathetic
–
Often cannot stand w/o support
–
Appears old beyond their years
–
Hair thin, dry, and lacks sheen
–
Low body temp and blood pressure
–
Prone to dehydration infections and
unnecessary blood clotting
–
}
◊
Marasmic kwashiorkor
Combo of chronic deficiency of cals AND
protein
Edema in legs and arms
–
A "skin and bones" appearance
–
w/ treatment, edema subsides and
appearance becomes more like
someone w/ marasmus
–
}
◊
®
Treatment for PEM
Medical and nutritional treatment can
dramatically reduce mortality rate
◊
Should be implemented carefully and slowly
Step 1: address life-threatening factors
Severe dehydration
–
Fluid and nutrient imbalances
–
}
Step 2: restore depleted tissue
Gradually provide nutritionally dense
cals and high-quality proteins
–
}
Step 3: transition to foods and introduce
physical activity
}
◊
®
□
Cells lining GI tract are not sufficiently replaced as they slough
off
□
Digestive function is inhibited□
Absorption of food is reduced□
Intestinal bacteria get into the blood and cause septicemia □
The immune system is compromised due to malnutrition and
cannot fight infection
□
§
○
Vegetarian diet
Reasons
Ethical □
Religious □
Environmental □
Health □
§
Vegetarians must consume adequate amounts of non-meat
proteins sources THROUGHOUT the day
§
It is NOT necessary to complement your proteins at every meal, just
w/in 24 hrs
§
Benefits of a healthy vegetarian diet include reduced risks of:
Heart disease□
High blood pressure□
Diabetes□
Cancer□
Stroke□
Obesity□
§
Potential risks of a vegetarian diet include low intake of key
nutrients:
Protein□
Ca□
Fe□
Vitamin B12□
Zn□
Vitamins A and D□
Omega-3 fatty acids (alpha-linoleic acids)□
§
Nutrients of Concern
Protein
Meet or exceed w/ balanced diet, adequate cals
®
□
Fatty acids
Higher intakes of ALA?
®
Algae based DHA supplements
®
□
Fe
1.8x as much iron as non-vegetarians
®
□
Zn
Similar to non-vegetarians
®
Soy, grains, legumes (soaking)
®
□
Ca
Lacto meet or exceed recommendations
®
Leafy greens: high content, low bioavailability
®
Non-dairy milk: similar bioavailability to cow's milk
®
□
B12
Only in foods of animal origin
®
Must be mindful of sources: supplements, fortified
foods
®
□
§
○
-
NUTR 2105 Chpt. 6 Proteins
Monday, February 12, 2018 2:27 PM
Document Summary
All enzymes made of proteins but only some hormones made of proteins. Proteins made up of chain of amino acids made based on individual"s dna. Excess dietary protein cannot be stored in body, but broken down and stored as fat. Proteins classified by number of amino acids in the chain. Typically 100 to 10,00 amino acids linked together. Amine group (nh2), carboxylic acid group (cooh), and side chain (r group) Form when c of acid group of one amino acid joins w/ the n atom of the amino group of second amino acid. Organization and shape of proteins affect their function. Primary structure: amino acids are linked together to form a simple linear chain. Secondary structure: geometric shape of protein that is folded and twisted. Tertiary structure: 3d globular shape of a protein. Quaternary structure: 2/ more polypeptide chains bond together together. Hcl denatures protein and converts pepsinogen to pepsin. Polypeptides enter small intestine and are broken into smaller peptides.
