Proteins There are an almost limitless number of proteins, which vary between species and are often species-specific. They determine the characteristics of a species.

Protein is found throughout the body—in muscle, bone, skin, hair, and virtually every other body part or tissue.

2 Types of Proteins 1) STRUCTURAL PROTEINS - these form the organism. For example: hair, nails, skin, muscle, etc.

2) PHYSIOLOGICAL PROTEINS - these carry out functions. Examples are: - enzymes (biological catalysts)

pigments (ex. various colour molecules in skin and eyes, hemoglobin)

hormones (chemical messengers)

contractile material in muscles

antibodies (disease protection)

Building Blocks of Proteins Proteins are large molecules whose building blocks are called amino acids. There are 20 different amino acid building blocks.

The Structure of an Amino Acid Each amino acid has an identical: Central carbon atom Amino group Carboxyl group

Each amino acid has a different: “R” group (aka side chain).

The Many Faces of Leucine

The Synthesis of Proteins Amino acids attach to each other by dehydration synthesis to form a peptide bond. 2 amino acids bond to form a dipeptide, 3 form a tripeptide and many joined together form a polypeptide. If more than 100 amino acids attach together it is considered a protein. Polypeptides (and proteins) are broken down via hydrolysis. Hyperlink to video!

Daily Recommended Intake The Institute of Medicine recommends or 8 grams of protein for every 20 pounds of body weight. The Institute of Medicine also sets a wide range for acceptable protein intake—anywhere from 10 to 35 percent of calories each day. Beyond that, there’s relatively little solid information on the ideal amount of protein in the diet or the healthiest target for calories contributed by protein.

All Protein Isn’t Alike Our bodies make amino acids in two different ways: Either from scratch, or by modifying others. The amino acids that our bodies can manufacture or modify are known as nonessential amino acids. Nine of the amino acids (known as the essential amino acids) must come from food as our bodies cannot make them. Conditionally Non-Essential: In times of stress or trauma the body will not have enough to make these!

Animal sources of protein tend to deliver all the amino acids we need, but only few plant sources do as well. These foods are said to be “complete proteins”.

Other protein sources, such as fruits, vegetables, grains, nuts and seeds, lack one or more essential amino acids. These foods are said to be “incomplete proteins”. Vegetarians need to be aware of this and must eat a variety of protein-containing foods each day in order to get all the amino acids needed to make new protein.

Protein Sources Some high-protein foods are healthier than others because of what comes along with the protein: healthy fats or harmful ones, beneficial fiber or hidden salt. It’s this protein package that’s likely to make a difference for health.

For example, a 6-ounce broiled porterhouse steak is a great source of protein—about 40 grams worth. But it also delivers about 12 grams of saturated fat. For someone who eats a 2,000 calorie per day diet, that’s more than 60 percent of the recommended daily intake for saturated fat.

A 6-ounce ham steak has only about 2 A 6-ounce ham steak has only about 2.5 grams of saturated fat, but it’s loaded with sodium—2,000 milligrams worth, or about 500 milligrams more than the daily sodium max.

6-ounces of wild salmon has about 34 grams of protein and is naturally low in sodium, and contains only 1.7 grams of saturated fat. Salmon and other fatty fish are also excellent sources of omega-3 fats, a type of fat that’s especially good for the heart.

Alternatively, a cup of cooked lentils provides about 18 grams of protein and 15 grams of fiber, and it has virtually no saturated fat or sodium.