PROTEIN

Vocabulary

Amino Group:

Denature:

Hormone:

Antibody:

Edema:

Intracellular Fluid:

Extracellular Fluid:

Deamination:

Ammonia:

Urea:

Kwashiorkor:

Marasmus:

WHAT IS PROTEIN?

•  Proteins are a sequence of amino acids

•  Of the 20 amino acids that exist, 9 are essential amino acids, and 11 are non-essential

•  There are also 4 amino acids that can be considered conditionally essential: arginine, tyrosine, glutamine, and cysteine

AMINO ACIDS: Structure

•  Consist of a central carbon atom bonded to:

•  The side group creates unique characteristics for each amino acid so they differ in: shape, size, composition, electrical charge, and pH.

AMINO ACID: Sequence

•  Amino acids link in specific sequences to form strands of protein

•  One amino acids is joined to the next by a PEPTIDE bond

•  Dipeptide –

•  Tripeptide –

•  Oligopeptides –

•  Polypeptide –

•  Proteins in the body and diet are long polypeptides (100s of amino acids)

DENATURING of PROTEINS

•  Acid, alkaline, heat, alcohol, and agitation can disrupt the chemical forces that stabilize proteins can cause them to lose their shape (denature)

•  Denaturing of proteins happens during food preparation (cooking, whipping, adding acids) or digestion (in the stomach with hydrochloric acid)

PROTEINS: Function

Structural Functions:

•  Collagen – is the most abundant protein in mammals, and gives bone and skin their strength

•  Keratin – provides structure to hair and nails

Enzyme Functions:

•  Enzymes are proteins that catalyze chemical reactions without being used up or destroyed in the process

Examples?

Hormone Functions:

•  Hormones are chemical messengers that are made on one part of the body, but act on cells in other parts of the body

Examples?

Immune Function

•  The Immune Response is a series of steps your body takes to mount an attack against invaders

•  Antibodies are blood proteins that attack and inactivate bacteria and viruses

•  Once an antibody has been made for a certain invader, your body can more quickly respond (Immunization)

Fluid Balance

•  Fluids in the body are intracellular or extracellular (interstitial and intravascular) and must remain balanced

•  Blood proteins like albumin and globulin help to regulate this balance by remaining in the capillaries and attracting fluid

•  Edema is the result of fluid imbalance

Acid-Base Balance

•  Proteins help to maintain a stable pH level in our body fluid by picking up extra hydrogen ions when conditions are acidic, and donating hydrogen ions when conditions are alkaline

•  Otherwise, the resulting conditions of acidosis or alkalosis could lead to coma or death

Transport Functions

•  Lipoproteins

•  Albumin transports a variety of nutrients such as calcium, zinc, and Vitamin B6

•  Transferrin transports iron (hemoglobin – a protein, contains iron, but it transports oxygen)

•  Proteins may also acts as channels or pumps across the cell membrane

Energy Source

•  If the diet does not provide enough energy, the body must begin to break down its own protein (from enzymes, muscle, and other tissue)

•  The proteins are broken down into individual amino acids, then deaminated, and the remaining carbon, hydrogen, and oxygen compounds are used to make energy or glucose

•  If the diet contains too much protein, the excess will be converted to glucose, or stored as fat

DIGESTION and ABSORPTION

MOUTH:

STOMACH:

SMALL INTESTINE:

•  Most protein absorption takes place in the duodenum and jejunum

•  Most amino acids are absorbed into the bloodstream, but some remain in the enterocytes and are used to synthesize enzymes and new cells

•  >99% of protein enters the bloodstream as amino acids

•  Absorption of whole protein can cause a severe allergic reaction

PROTEINS in the BODY

•  Amino Acid Pool – amino acids that are available throughout the body (tissues and fluids) for use when needed

•  Protein Turnover – of the ~ 300 grams of protein synthesized by the body each day, 200 grams are made from recycled amino acids

NITROGEN EXCRETION

•  Amino acids breakdown yields an amino group (containing nitrogen)

•  This molecule is unstable and is converted to ammonia

•  Ammonia is toxic, so it is excreted from the cells and sent to the liver, where it is converted to urea and water

•  The urea is transported to the kidney, where it is filtered from the blood and finally sent to the bladder for excretion in the urine

•  Nitrogen is also lost through hair, skin, GI cells mucus, nails, and body fluids like sweat

How Much Protein Do We Need?

Adults:

Endurance Athletes:

Heavy weight lifters:

From The Gatorade Sport Science Institute:

High Protein Diets and Protein Supplements
Protein supplements or switching to a high protein diet is not effective for athletes who already get enough calories and eat protein foods two to three times daily. Here’s why:
·  Athletes get enough protein for muscle growth and repair in an average mixed diet.
·  Protein from a food or a protein supplement acts the same in the body.
·  Extra protein not needed by the body is burned for energy or stored as fat.

PROTEIN QUALITY

•  Complete Proteins –

•  Incomplete Proteins –

PROTEIN: Health Effects

EXCESS DIETARY PROTEIN

•  May strain the kidneys

•  May cause mineral losses (especially calcium)*

•  May increase risk of obesity*

•  May increase risk of heart disease*

•  May increase risk of cancer*

*only with animal protein

INSUFFICIENT DIETARY PROTEIN

•  Protein-Energy Malnutrition (PEM) can occur anywhere in the world, but is most common in developing countries

•  Kwashiorkor

•  Marasmus

•  In industrialized nations, PEM may exist in the elderly population, in the poor, and those with anorexia, cancer, AIDS, or malabsorption syndromes

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