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Elastin

Elastin is a significant component of skin. Like collagen, elastin is a protein; however there are differences between elastin and collagen. Collagen has a rigid structure that gives tensile strength to tissues. Elastin has a more flexible structure that gives resiliency to tissues. l. Organs that must endure large pulling forces have higher levels of collagen, while organs that must stretch and rebound have higher levels of elastin.

The Molecular Structure of Collagen and Elastin
Collagen is made of long straight peptide chains that are bound together to form fibers that are stronger than steel on a per gram basis. Elastin forms a large shapeless central core from which other proteins extend. The complex shape of the elastin protein allows it to stretch and recoil like a spring. The very name "elastin" comes from the elasticity that it contributes to tissues and organs.

Like the structure of all proteins, the structures of collagen and elastin result from the identity of the amino acids in them and the chemical interactions of those amino acids. Collagen is made primarily from glycine, hydroxyproline, and proline. Chains of these amino acids combine to form a triple helix that is extremely strong.

About one-third of elastin is made of the amino acid glycine. Alanine, valine, and leucine are also common in elastin. The elastin protein easily attracts water molecules, which allows elastin molecules to slide over each other as a tissue stretches. Bonds between neighboring elastin molecules pull the elastin back to its original form so that the tissue can return to its resting shape.

Collagen and Elastin in Organs
Both elastin and collagen are important parts of tendons, arteries, and skin. The relative abundance (as measured by dry weight) of each molecule in a given organ is related to the forces that organ must endure.

Tendons connect muscles to bones. They must withstand the forces that muscles apply. The Achilles tendon connects the heel to the leg. Every time a person walks, her entire weight stresses the Achilles tendon. To hold up under these conditions, the Achilles tendon is 4% elastin and 86% collagen.

The heart's pumping causes the blood pressure to swing widely. All arteries stretch and recoil to accommodate this changing flow. The aorta is the artery that carries blood right after it leaves the heart. It must stretch and recoil more than any other artery because of this. To satisfy this demand, the aorta is 75% elastin and 17% collagen.

Skin is a person's boundary to the outside world. It must stand up to the stresses of interacting with the environment. When a person climbs a rope, her skin must be strong enough to resist the tug of her weight where her hand that is in contact with the rope. Skin must also resist subtler forces. Facial expressions temporarily reshape the face. The skin on the face needs to be elastic enough to return to its original shape once the facial expression is over. Wrinkles form when the skin is not able to fully recover from these deformations. To give it both strength and resiliency, skin is 1% elastin and 72% collagen.

  Elastin Collagen
Molecular Structure Amorphous Tangle Ordered Triple Helix
Function Elasticity Strength
Organs Containing Skin, Aorta, Tendons Skin, Aorta, Tendons

The amino acids in a protein, such as collagen or elastin, determine its molecular structure. The molecular structure then determines the protein's qualities. Elastin provides resiliency to tissue while collagen gives it strength. Each organ has the proportion of collagen and elastin that helps it function best.

References:

1. Collagen and Elastin. Meat Science and Muscle Biology
University of Illinois at Urbana-Champaign
http://labs.ansci.illinois.edu/meatscience/Library/collagen.htm

2. Elastin. American Academy of Dermatology
http://www.aad.org/education/students/Elastin.htm