Bio 28: NutritionInstructor: Paul Nagami

Laney College

Proteins

Proteins Do Almost Everything

Proteins are the “workhouses” of the cell, making chemical reactions possible. For example, there are proteins to put together DNA and to break apart starch. A protein that runs a chemical reaction is called an enzyme.

Protein Structure

Strands of the protein keratin, a tough protein in hair. Its shape, or structure, contributes to its toughness.Let’s zoom in even closer... what are these helices (corkscrews) made out of? What holds them together?

Proteins are made of amino acids

Amino acid monomers!Proteins are

polymers, like carbohydrates!

Amino Acids

Amine functional group (has N)

Acidic functional group (like end of fatty acid)

The part in yellow is called the side chain. There are 20 different amino acid side chains in human proteins.

Assembling Proteins

Peptide bond = bond between amino acids

It’s not easy to break this bond, but we have enzymes in on our stomach that can break down proteins to harvest the amino acids.

What Makes Proteins Different from Each Other?

Proteins with different shapes can have different functions. These shapes depend on their sequence of amino acids.

Proteins Are Amino Acid Polymers (Chains)

Imagine unfolding a protein chain…You would be able to look at the individual amino acids.

Some of these amino acids would stick to each other. Others would stick to water.

Hydrophilic amino acids end up on the outside of the protein, hydrophobic amino acids end up on the inside of the protein.

The side chains (sticking out)either stick to each other or to surrounding water

DNA is the instructions for protein

DNA’s function: Instructions to make proteins, such as lactase! Differences in DNA code can lead to differences in lactase production, causing lactose intolerance.

Essential Amino AcidsAlthough there are 20 different amino acids, most people can make 11 of them.

The remaining 9 that we can’t make are called essential amino acids.

To build complete protein, you must eat all 9 of these. Meat generally has all 9.

You can get them without meat if you practice protein complementation.

By pairing foods that contain different amino acids in the same day, you can eat healthy without meat.

Making Complete Protein

Examples of complete protein: Rice + beans, rice + lentils, potatoes + milk, whole-wheat bread + peanut butter.

Dangers of Excessive Protein

If you eat too much protein, it is not stored. Instead, the body eliminates the extra amino acids in the urine.

In the long term, excessive protein consumption can lead to kidney stones and acidic blood pH.

Some carbohydrates are necessary to break down protein efficiently! If you eliminate carbs, you can’t metabolize protein well.

Protein Malnutrition

Marasmus: Lack of both protein and caloric intake in general. Leads to wasting, very common in infants.

Kwashiorkor: Lack of protein. Common after 18 months; can lead to edema/bloating, death.