“The Variety of Proteins” Different types, with different tasks

Review What determines the behavior of a molecule? Like Legos, if we change the shape, we change its use and how it attaches to others.

Different shapes allow the Legos to do different jobs, just like different shapes allow proteins to do different jobs. Proteins in our tendons are 10x as long as they are wide, forming stiff, strong structures.

What is collagen? “The protein collagen acts like glue between cells.” As we get older and lose our ability to make collagen, our skin wrinkles and sags.

“Enzymes are proteins that change other substances chemically.” Digestive enzymes, for example.

Some work alone, while others need to work together. Hemoglobin is made of four smaller protein strands; each holds iron for the blood.

It also turns our blood red. Methemoglobinemia

How so much variety? As we’ve mentioned, it’s all about the combination of the 20 amino acids. You could compare this to a Lego set, with 20 bricks. Imagine all of the different shapes you could make… Your body contains 10,000 different proteins.

Inherited Amino Acid Sequences Remember that the amino acid sequence is specified by heredity. “In sickle-cell disease, one aa is wrong, changing the shape of hemoglobin.”

Gene Expression “When a cell makes a protein, the gene for that protein has been ‘expressed.’” So if you received a blond hair gene from mom and a brown hair gene from dad, And your hair turns out brown, The brown hair gene was expressed.

Can what I eat change my DNA? “Nutrients don’t change DNA.” “They do influence expression.” So perhaps consuming a nutrient could trigger you to express a hidden gene! Ghost in Your Genes: New science!

So How Much Protein Do We Need to Eat? “Nutritionists say we should get a minimum of 10% of calories from protein.” If you’ll remember, the specific amount was “0.8 grams of protein per kilogram of body weight.”

What about athletes? Athletes may need slightly more, but the increased need is well covered by most Americans’ diets. So most of us are already eating more than we need.

“Nitrogen Balance” So why are the recommendations what they are? In order to figure out how much protein we need, we have to look at the nitrogen we eat and compare it to the nitrogen we need to excrete.

“In healthy adults, nitrogen-in (consumed) = nitrogen-out (excreted).” How can we measure someone’s nitrogen excreted? Under controlled conditions, we can examine the nitrogen totals in urine, sweat, feces. Then we can calculate what the person needs to consume to make up for these losses.

Balance of Nitrogen Value “Normal adults: nitrogen equilibrium.” There are other situations, where one is greater than the other, We’ll take a look at who this would be.

“Nitrogen-in>nitrogen-out: person is making more proteins than they are losing.” Who might be in this situation? “growing child, person building muscle, pregnant woman”

“Nitrogen-in<nitrogen-out: losing protein.” Who might be in this situation? “sick person, astronaut” Why an astronaut?

“Complimentary Proteins” So if we need all of the amino acids, and no food contains them all, what would be a logical way to construct a diet? “A diet should contain different proteins, so that all aa’s are consumed.”

“When we eat multiple aa-rich foods, our bodies build complementary proteins.” This means that what we don’t get from one food, we get from another.

This plan is called mutual supplementation. In this example, legumes and grains go together because they supply different aa’s.

Benefit of Living Here In the U.S., we have access to all different proteins! In countries where food is limited, they may have adequate quantity, but they may only have one type of aa. That can cause malnutrition.