Proteins and Amino Acids Review

Comprehensive vocabulary terms and functional descriptions of proteins and the various categories of amino acids based on lecture notes.

Proteins

Molecules containing C, H, O, and Nitrogen (N) that provide $4\,\text{kcal/g}$ of energy and are made of amino acids.

Dipeptide

Two amino acids bonded together.

Tripeptide

Three amino acids bonded together.

Polypeptide

Four or more amino acids bonded together.

Essential Amino Acids

A group of $9$ amino acids that must be obtained from the diet.

Non-Essential Amino Acids

A group of $11$ amino acids that the body can normally produce on its own.

Conditionally Essential Amino Acids

A group of $3$ amino acids including Arginine, Cysteine, and Tyrosine.

Leucine

Essential amino acid that helps reduce muscle protein breakdown, triggers muscle growth, and promotes healing of skin and bones.

Isoleucine

Essential amino acid that prevents muscle wasting, aids blood hemoglobin production, and helps regulate blood sugar.

Histidine

Essential amino acid that absorbs UV light in the skin and is involved in the production of Red and White blood cells.

Valine

Essential amino acid not processed by the liver; assists brain uptake of neurotransmitter precursors such as Tryptophan, phenylalanine, and tyrosine.

Lysine

Essential amino acid that inhibits viruses, increases Calcium absorption, and forms L-carnitine when combined with Vitamin C.

Methionine

Essential amino acid that increases antioxidant levels, neutralizes ammonia in urine, and helps remove toxic waste from the liver.

Phenylalanine

Major precursor of Tyrosine that enhances learning and memory; it is a major element in collagen and needed for the Central Nervous System.

Threonine

Essential amino acid that acts as a detoxifier to prevent fatty build up in the liver and is a component of collagen.

Tryptophan

Essential amino acid that stimulates the release of growth hormones and is a precursor to the neurotransmitter serotonin.

Arginine

Conditionally essential amino acid that can increase secretion of insulin and growth hormones; it is a precursor of GABA and Ornithine.

Cysteine

Conditionally essential amino acid that detoxifies and helps prevent damage from alcohol and tobacco use; it is a precursor of Taurine.

Tyrosine

Conditionally essential amino acid that is a precursor of dopamine, stress hormones, thyroid hormones, and melanin.

Alanine

Non-essential amino acid that is a major component of connective tissue and a key intermediate in the glucose-alanine cycle.

Aspartic Acid

Non-essential amino acid that helps convert Carbohydrates into muscle energy and reduces ammonia levels after exercise.

Glutamic Acid

Non-essential amino acid used as a source of energy and an important precursor for Glutamine, proline, ornithine, glutathione, and GABA.

Glutamine

The most abundant amino acid; it serves as brain fuel, supports the immune system, and provides energy for kidneys and intestines.

Glycine

Non-essential amino acid used as raw material for other amino acids; it is part of hemoglobin and almost all enzymes.

Serine

Non-essential amino acid used for energy production and built-up of the immune system through immunoglobulins and antibodies.

Proline

Non-essential amino acid that is a major constituent of collagen and a major component in the formation of connective tissue and heart muscle.

Taurine

Non-essential amino acid that aids in the absorption and elimination of fats and acts as a neurotransmitter in the brain and retina.

Ornithine

Non-essential amino acid that increases growth hormone secretion, participates in the urea cycle, and is needed for proper liver function.

Deamination

The process of stripping the Nitrogen-containing group from an amino acid to use it for energy production.

Urea

The substance the liver converts ammonia into to prevent the toxic buildup of ammonia in the blood.

Keto Acids

Compounds produced during amino acid breakdown that can be harmful if present in excess.

protein digestion and absorption of mouth

Chewing and crushing moisten protein foods and mix them with saliva to facilitate

protein digestion and absorption of stomach

HCl uncoils protein strands and activates

(Pepsin, HCl)

protein —————→ smaller polypeptides

protein digestion and absorption of small intestine

Pancreatic and small intestinal enzymes split

(proteases)

smaller polypeptides ————→ tripeptides, dipeptides

(tripeptidases and dipeptidases)

— ————————————→ amino acids

protein turnover

The process within each cell of proteins continually being made and broken down, requiring amino acid availability.

Role of protein turnover

Protein turnover is essential for forming new tissue such as in embryos, muscles being trained, growing children, healing scar tissue, and producing new hair or nails.

Break down of proteins

amino acids are liberated within the cells or released into the bloodstream. Some amino acids are recycled into other proteins, while others are stripped of nitrogen and used for energy.

daily impact of amino acid breakdown in the body

Every day, a quarter of the body’s available amino acids are irretrievably broken down and used for energy.

Amino acids from foods

needed daily to support new growth and maintenance of cells.

Negative nitrogen status

if the body synthesizes more than it degrades

Positive nitrogen status

if the body degrades more than it synthesizes

Nitrogen balance

used to estimate protein requirements

Chemically unique

What distinguishes us chemically from each other are minute differences in our own particular body proteins.

These differences are determined by our proteins’ amino acid sequences, which are written into the genes we inherited from our parents and ancestors. The genes direct the making of all the body’s proteins

650 muscles

number of muscles

187 joints

number of joints

Enzyme

catalysts that are essential to all life

Functions of enzyme

Break down macronutrients into small units that can be absorbed and used by cells

➢ Ensemble and disassemble lipids

➢ Put together amino acids to build proteins

➢ Break apart compounds and put other compounds together

➢ Proteins become enzymes themselves

pepsinogen

inactive enzyme in stomach converts into pepsin to breakdown protein

trypsinogen

inactive enzyme in pancreatic juice precursor of trypsin to breakdown protein

transporters

A large group of proteins specialize in transporting other substances such as lipids, vitamins, and minerals around the body. They do it within the blood, into cells and out of cells or even around the cellular interiors.

Hemoglobin

carries oxygen from the lungs to the cells

Lipoproteins

transport lipids in the watery blood

What circumstances can disrupt nitrogen balance in the body?

People who are starving or suffering severe stress such as burns, injuries, infections, and fever have a disrupted nitrogen balance as the body loses nitrogen by breaking down muscle proteins.

Location of body fluid

spaces inside the blood vessels, spaces within the cells, spaces between the cells

EDEMA

excess fluid accumulation in the interstitial spaces (between cells)

Quantity of fluid

vital; is the composition of fluid

antibodies

specialized proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses.

hormone

messenger molecules carried in the blood

Gastrin

hormone released by the stomach

stimulates the secretion of gastric acid (HCl) to aid in digestion.

Cholecystokinin (CCK)

hormone secreted by the small intestine

stimulates the gallbladder to contract and release bile, promotes the secretion of digestive enzymes from the pancreas, aiding in digestion and fat absorption.

Gherlin

hormone produced influences insulin secretion in the pancreas &primarily in the stomach

signals hunger to the brain and stimulates appetite

Leptin

hormone produced by fat tissue

signals satiety to the brain, helping to regulate energy balance and inhibit hunger.

location of glucose

stored as glycogen in liver and muscles

Protein deficiency

➢The body slows its synthesis of proteins while increasing its breakdown of body tissue protein to liberate the amino acids it needs for other critical needs.

➢The body’s life-sustaining activities come to a halt (slow growth, impaired brain and kidney function, weakened immune defenses, impaired nutrient absorption

Severe Acute Malnutrition (SAM) or Protein-Energy malnutrition (PEM):

when diet delivers too little protein

Protein recommendations

RDA states 0.8 grams per kilogram of weight (or 2.2 pounds). 10-35% of energy intake

Protein quality

Is dictated by:

1. Digestibility: Plant Protein is less digestible.

2. Animal Protein is highly digestible.

3. Amino Acid Composition: The higher the content of ESSENTIAL amino acids the higher the quality