Proteins—in Muscle and Immune Systems

Today we took a quick tour through two more areas of the body in which proteins are essential—muscles and the immune system.  Here are some links to videos we watched in class.

Muscles are made of overlapping protein fibers called actin and myosin, which shorten (contract) the muscle by a oar-like mechanism—the myosin "heads" grab the actin fibers and pull them towards each other, increasing the overlapping and shortening the muscle. The muscle relaxes when the myosin head releases the actin, a process that uses energy in the form of ATP.  Ever wondered why dead people are called "stiffs"?!

1st Video on Muscle Structure
2nd, more detailed Video on Actin/Myosin interaction




The immune system is a complicated system of several trillion cells (out of 100 trillion in our whole body) that help protect us from foreign invaders. The molecules on the surface of invading bacteria and viruses are called antigens, which are a kind of protein that helps the invader enter our cells, where it uses our cellular machinery to copy its DNA to make more viruses. Some of our immune defenders, like antibodies, are also proteins; these help to mark the foreign cells for destruction.

The Flu Virus Video

Proteins—the Hormone Insulin

Hormones are molecules that pass along chemical signals between organs and cells. Insulin is protein hormone that is responsible for controlling the levels of glucose in the blood.  Too much glucose in the blood causes diabetes and a variety of physiological problems in the body.

Watch this short animation of the role of insulin in our body. Insulin is released from the pancreas when blood sugar levels are high (usually after eating a meal), and it attaches to receptors on fat and muscle cell membranes, causing a cascade of chemical interactions inside the cell. The result is the opening of protein channels that transport glucose into the cell. Glucose is then converted into carbohydrate storage molecules (glycogen) or fats (triglycerides) to burn for energy in the future.

Insulin Signaling Animation