Proteins —> Basic material of every body cell

Contain carbon, hydrogen oxygen, nitrogen. (CHON)

—> Only nutrient group that contains nitrogen and some contain sulfur

Amino Acids —> Proteins are composed of chemical compounds; building block of the protein

Functions

Building and Repairing Body Tissue

Primary Function

Made possible by the provision of the correct type + # of amino acids in the diet

As cell are broken down during metabolism (catabolism), some amino acids released into the blood are recycled to build new and repair other tissue (Anabolism, this method)

Regulating Body Functions

Proteins are important components of hormones + enzymes. —> essential for the regulation of metabolism + digestion

Maintain fluid + electrolyte balance in the body + prevent edema (abnormal retention of body fluids)

Essential for the development of antibodies and for a healthy immune system

Providing E

Can provide E if and when the supply of carbohydrates and fats is really low

Each gram of protein is 4 calories

NOT good use of protein

Food Sources

Found in both animal + plant foods

Animal food sources provide highest quality of complete proteins.

—> Include meats, fish, poultry, eggs, milk + cheese

—> Also provide saturated fats + cholesterol

—> Should be carefully selected from low-fat animal foods (fish, poultry, lean meats and low-fat dairy products)

Proteins found in plant foods are incomplete proteins and lower quality

—> Nuts, sunflower seeds, sesame seeds, soybeans, navy beans etc.

—> Can be used to produce textured soy protein + tofu ]→ Called Analogues

Tofu —> Soft, cheese-like food made from soy milk

—> Bland product that easily absorbs the flavors of other ingredients with which it’s cooked

—> Rich in high-quality proteins + B vitamins + low in sodium

Classification

Classification + Quality of a protein depends on the number + types of amino acids it contains.

There are 20 amino acids —> 10 of them are essential to us

—> Necessary for normal growth + development; must be provided in the diet

Complete proteins —> Proteins containing all the essential amino acids are of high biologic value; extremely bioavailable

Bioavailable —> The ability of a nutrient to be readily absorbed and used by the body

Nonessential amino acids can be produced in the body from essential amino acids, vitamins + minerals

Incomplete proteins —> Lack 1 or + of the essential amino acids

—> Cannot build tissue without the help of other proteins

—> Value of Each is increased when it’s eating in combination with another incomplete protein.

Complementary Proteins —> Proteins that contain all the essential amino acids

Gelatin is the only protein from an animal source that’s incomplete

Digestion + Absorption

Begins in the mouth where the teeth grind the food into small pieces —> Mechanical digestion of protein

Chemical digestion being in the stomach

1. Hydrochloric acids prepares the stomach so tht the enzyme pepsin can begin reducing protein to polypeptides (Ten or more amino acids bonded together)

2. After it reaches the small intestine 3 pancreatic enzymes (trypsin, chymotrypsin, carboxypeptidase) continue chemical digestion

3. Amino acids in the small intestine get absorbed and are carried by the blood to all the body tissues

Metabolism + Elimination

When amino acids are broken down, the nitrogen-containing amine group is stripped off. —> process called deamination

—> Produces ammonia which is released into the bloodstream by cells

—> Liver picks up the ammonia, converts it to urea and returns it to the blood stream for the kidneys to filter out and excrete

The remaining parts are used for E / converted to carbohydrate or fat and stored as glycogen or adipose tissue.

Dietary Requirements

Protein requirement is determined by size, age, sex and physical + emotional conditions

Large person has more body cells to maintain than a small person. Athletes + active individuals require more protein.

When digestion is inefficient, fewer amino acids are absorbed by the body —> protein requirements is higher

—> case with the elderly

Extra proteins are required after surgery, sever burns, during infections→ Function is to replace lost tissue + manufacture antibodies

Extra protein are also greater for women who are pregnant.

To determine ur requirement

1. Divide body weight by 2.2 (# of pounds per kilogram)

2. Multiply the answer obtained above by 0.8 (grams of protein per kilogram of body weight)

Protein Excess

The saturated fats + cholesterol common to complete protein foods may contribute to heart disease + provides more calories than u want.

Might result in colon cancer + high calcium excretion (depletes the bones of calcium)

Excess protein intake may put more demands on the liver and the kidneys to excrete urea than they are prepared to handle.

Protein and Amino Acid Supplements

Protein needs can easily be met through the diet.

Ex of this are protein shakes, bars, powders.

Proteins comes from whey, casein, soy, bean, or pea protein.

High quality protein foods are more bioavailable than expensive supplements.

Single Amino acids can be harmful to the body + never occur naturally in food.

Nitrogen Balance

Nitrogen Balance —> When nitrogen intake equals nitrogen excreted.

Positive nitrogen balance —> nitrogen intake exceeds outgo

—> Occurs during pregnancy, children’s growing years, athletes develop additional muscle tissue and when tissues are rebuilt after physical trauma (illness or injury)

Physical trauma —> Extreme physical stress

Negative nitrogen balance —> more nitrogen lost than taken in

—> Indicates protein is being lost

—> Caused by fevers. injury, surgery, burns, starvation or immobilization

Protein Deficiency

Albumin —> Protein that occurs in blood plasma

When ppl don’t get a good supply of protein for an extended period, muscles wasting, arms + legs will become thin and also albumin deficiency will occur.

Water is excreted when sufficient protein is eaten

Signs are usually see in neglected children, elderly, poor or incapacitated

Protein Energy Malnutrition

Protein E Malnutrition (PEM) —> malnutrition resulting from inadequate intake of protein + energy-rich foods

—> Types are Marasmus + Kwashiorkor

Marasmus —> Severe wasting caused by lack of protein + all nutrients or faulty absorption

Kwashiorkor —> Deficiency disease caused by extreme lack of protein

Mental retardation —> Below normal intellectual capacity

Children who lack sufficient protein don’t grow to their potential size.

Marasmus + Kwashiorkor are 2 deficiency diseases that affect children.

—> Even if they survive they could suffer from permanent mental retardation

—> Mortality rates are high for kwashiorkor