• Carbon, hydrogen, oxygen, and nitrogen

some basic structure for all amino acids

• central carbon
• hydrogen
• an amino group (NH2)
• an acid group (COOH)

when a nonessential amino acid becomes esstial under certan circumstances

If you lack an essential vitamin that makes nonessential vitamin body cant make nonessential amino acids therefore making it conditionally essential

two of the hemoglobins four polypeptide chains have the normal sequence, but the other two do not.

alters ability to carry oxygen effectively.

What is deamination?

stomach- hydrochloric acid uncoils each proteins tangled strands so that the digestive enzymes can attack the peptide bonds

acid converts pesinogen to pepsin

Pepsin breaks proteins into smaller polypeptide

peptidase enzyme splits dipeptides and tripeptides into amino acids

8 grams per kilogram of healthy body weight perday

weight / 2.2 lb/kg = x

xkg * .8 g/kg = grams of protein 

what are complimentary proteins?

• Sudden and recent deprivation of food
• Fatty liver develops because protein carriers are not present to take fat out of the liver

• The swelling of body tissue caused by excessive amounts of fluid in the interstitial spaces.
• Inadequate dietary intake of protein

The degredation and synthesis of protein

(within each cell, proteins are continually being made and broken down) 

• A central carbon
• A hydrogen
• An amino group (NH2)
• An acid group (COOH)
• The fourth bonding site on the carbon distinguishes each amino acid

• The side groups of amino acids vary from one amino acid to the next.
• This makes amino acids more complex than either carbohydrates and lipids
• A starch molecule would be several thousand units long, but each unit is a glucose molecule

There are 9 amino acids that the body cannot make or cannot make in sufficient amounts. These include:

1. Histidine
2. Isoleucine
3. Leucine
4. Lysine
5. Methionine
6. Phenylalanine
7. Threonine
8. Tryptophan
9. Valine

• When a nonessential amino acid becomes essential under certain circumstances, it is known as conditionally essential

• For example: the body uses phenylalanine (essential) to make tyrosine (nonessential)
• But if the diet fails to provide phenylalanine, or the person has phenylketonurea (PKU), then tyrosine becomes conditionally essential

• Cells link amino acids end-to-end in a variety of sequences to form thousands of different proteins
• A peptide bond is the bond that unites one amino acid to the next
• Condensation bonds amino acids

• Polypeptide= many amino acids linked together
• Most proteins are a few dozen to several amino acids long

• Amino Acid sequences vary within each protein.
• The variety of possible sequences for polypeptide chains is tremendous 

• Polypeptide chains twist into a variety of complex, tangled shapes, depending on their amino acid sequence
• The unique side group of each amino acid gives it characteristics that attract it to, or repel it from the surrounding fluids and other amino acids.
• Some amino acid side groups carry electrical charges that are attracted to water molecules, they are hydrophilic
• Others are neutral and are repelled by water, they are hydrophobic
• As amino acids are strung together to make a polypeptide, the chain folds so that its charged hydrophilic side groups are on the outer surface near water
• The neutral hydrophobic groups tuck themselves inside, away from the water
• This intricate coiled shape gives the protein maximum stability

1. The ____ of proteins enable them to perform their various tasks in the body.
2. Some proteins form _____ that can carry and store materials within them.
3. Some, such as those of ____, are more than ten times as long as they are wide, forming strong, rodlike structures.
4. While some polypeptide chains function just as they are, some need to associate with other polypeptides to form large working ____.

1. The unique shape of proteins enable them to perform their various tasks in the body.
2. Some proteins form hallow balls that can carry and store materials for them.
3. Some, such as those of tendons, are more than ten times as long as they are wide, forming strong, rodlike structures.
4. While some polypeptide chains functino just as they are, some need to associate with other polypeptides to form large working complexes.

Some examples of denaturation include:

1. Hardening of an egg when it is cooked
2. The curdling of milk when acid is added
3. The stiffening of egg whites when they are whipped

Digestion and absorption

• Proteins in foods do not become ____ proteins directly
• The foods supply the amino acids from which the body ____ its own proteins
• When we eat protein, enzymes break the peptide bonds and the polypeptides become shorter and shorter until only ____ are left. 

• Proteins in foods do not become body proteins directly
• The foods supply the amino acids from which the body makes its own proteins
• When we eat protein, enzymes break the peptide bonds and the polypeptides become shorter and shorter until only amino acids are left

• The major event in the stomach is partial breakdown of proteins
• Hydrochloric acid uncoils (denatures) each protein's tangled strands so that the digestive enzymes can attack the peptide bonds
  • Hydrochloric acid converts the enzyme pepsinogen (inactive) to pepsin (active)
  • Pepsin cleaves proteins into smaller polypeptides

• When polypeptides enter the small intestine, several pancreatic and intestinal proteases hydrolyze them even further to small peptides
• The peptidase enzymes on the membrane surfaces of the intestinal cells split most of the di-peptides and tri-peptides into amino acids
• Only a few di-peptides enter the circulation intact

• A number of specific carriers transport amino acids ( and di-peptides and tri-peptides) into the intestinal wall
• Once inside, the amino acids may be used for energy or to make needed compounds
• Amino acids not used by the intestinal cells are carried in the blood to the liver
• Enzymes are proteins and they get digested as well and are broken down to amino acids

• Each human being is unique because of small differences in the body's proteins.

• These differences are determined by the amino acid sequences of proteins, which in turn, are determined by genes.

• The instruction for making every protein in a person's body are transmitted by way of the genetic information received at conception.

1. Transcription- A stretch of DNA is used as a template to make a strand of RNA (ribonucleic acid) known as messenger RNA (mRNA). mRNA then takes the code across the nuclear membrane into the body of the cell. It attaches itself to one of the ribosomes (protein making machine)
2. Translation- mRNA specifies the sequence in which the amino acids line up for synthesis of a protein

• Transfer RNA (tRNA) collects amino acids from the cell fluid and brings them to the mRNA
• Each of the 20 amino acids has a specific tRNA
• Thousands of tRNA each carrying its amino acids wait to unload its amino acid
• When the mRNA's list calls for a specific amino acid, the tRNA moves into position, then the next and so on
• Enzymes bind the amino acids together'
• The protein strand is released and the tRNA are freed to return for other loads of amino acids

• In a person with sickle cell anemia, two of hemoglobin's four polypeptide chains have the normal sequence, but the other two do not
• Valine takes the place of glutamic acid
• This alterations alters hemoglobin's ability to carry oxygen effectively
• Sickle cell anemia raises energy needs, causes many medical problems, and can be fatal

• Proteins are very versatile
• They have many roles in the body:
  • Building materials 
  • Enzymes
  • Hormones
  • REgulators of fluid balance
  • Acid-base regulators
  • Transporters
  • Antibodies
  • Source of energy and glucose
  • other roles

• The amino acid pool remains constant regardless of rate of degradation and intake.
• These amino acids can be used to make other proteins, or their nitrogen will get stripped and they will be stored as fat

Nitrogen balance

• In healthy adults, protein ____ balances ____
• Protein ____ balances with nitrogen ____ in the urine, feces, and sweat.
• When nitrogen intake = nitrogen output a person is in nitrogen equilibrium or ____.

• In healthy adults, protein synthesis balances degradation
• Protein intake balances with nitrogen excretionin the urine, feces, and sweat.
• When nitrogen intake = nitrogen output a person is in nitrogen equilibrium or zero nitrogen balance.

• If the body makes more protein than it breaks down, the body is in positive nitrogen balance.
  • Growing infants
  • Children
  • Adolescents
  • Pregnant women
  • People recovering from protein deficiency or illness
• These people retain the protein to make new tissues (blood, bone, skin, and muscle cells) so they do not excrete as much nitrogen as they take in

• If the body degrades more than it synthesizes and loses proteins, nitrogen status becomes negative.
  • People who are starving
  • Burn victims
  • Severe injuries
  • Fever
• Their output exceeds their intake because muscle and other body proteins are being broken down for energy

• Deamination produces amonia and is released into the blood
• The liver picks up the ammonia and converts it to urea (less toxic than ammonia). Urea is the principle nitrogen excretion product of protein metabolism (2 ammonia fragments and a CO2)
• The urea returns to the blood
• The production of urea increases as dietary protein increases
• Urea reaches its maximum production rate when a person consumes ~250 grams per day
• The kidneys filter urea out of the blood
• The remaining carbon fragments (after deamination) can enter a number of pathways
  • Used for energy
  • Used for production of glucose, ketones, cholesterol, or fat

• Quality is determined by
  • Protein digestibility (animal proteins: 90-99%) (plant proteins: 70-90%) (soy and legumes: >90%)
  • Amino acid composition (if the diet does not supply an essential amino acid, a cell will dismantle its own proteins to obtain it)-not good!

Complimentary Proteins

• In general plant proteins are ____ quality than animal proteins and plants also offer ____ protein (per weight or measure of food).
• For this reason ____ improve the quality of proteins in their diets by combining plant-protein foods that have different but complementary amino acid patterns
• This strategy yields ____ that together contain the essential amino acids in quantities sufficient to support the body

• In general plant proteins are lower quality than animal proteins and plants also offer less protein (per weight or measure of food).
• For this reason vegetarians improve the quality of proteins in their diets by combining plant-protein foods that have different but complementary amino acid patterns
• This strategy yields complimentary proteins that together contain the essential amino acids in quantities sufficient to support the body

• When people are deprived of protein, energy, or both, the result in protein-energy malnutrition (PEM)
• Most often strikes in childhood
• Most prevalent form o malnutrition in the world
• PEM occurs in 2 forms
  • Marasmus
  • Kwashiorkor

• Named after the Greek word meaning "dying away"
• Severe deprivation of food over a long period of time
• Most common in children 6-12 in overpopulated, impoverished areas

• Sudden and recent deprivation of food
• Typically occurs in children between 18 months and 2 years
• Weight loss is not as severe as marasmus
• Proteins and hormones that previously maintained fluid balance diminish and fluid leaks causing the abdomen and limbs to become swollen with edema
• Fatty liver develops because protein carriers are not present to take fat out of the liver
• After several severe problems, the child can die

• Antibodies can be broken down to provide the body with amino acids it needs 
• This causes the immune system to weaken
• This can cause an infection of the immune system known as dysentery
• Dysentery causes diarrhea which causes dehydration
• If anemia kicks in (body not producing hemoglobin) then further weakness occurs
• All this leads to heart failure and death

• In developed countries we see an excess of protein intake
• Overconsumption of proteins offers no benefits and may even pose health risks
• High-protein diets have been associated with:
  • Heart disease
  • Cancer
  • Osteoporosis
  • Obesity
  • Kidney stones

Heart Disease

• A high protein diet may contribute to the progression of ____ due to the consumption of animal products which have high levels of ____ fats.

• A high protein diet may contribute to the progression of heart disease due to the consumption of animal products which have high levels of saturated fats.