Aging skin begins to wrinkle because the protein (A)__________ becomes more rigid and the protein (B)__________ is reduced.

Normal body cells divide 80 or 90 times before dying. When a cell divides, it makes a copy of its chromosomes so that each resulting daughter cell has a complete set of chromosomes. The ends of chromosomes are capped by segments of DNA called (C)__________. As cells divide little pieces of these capped segments are lost. A cell dies when only a tiny portion remains.

A. elastin

B. collagen
C. telomeres

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Aging skin begins to wrinkle because the protein (A) collagen becomes more rigid and the protein (B) elastin is reduced.

To get the answer to the question, we need to understand the changes that occur in aging skin. The process of aging leads to several changes in the skin, including the development of wrinkles. Two key proteins involved in maintaining the structure and elasticity of the skin are collagen and elastin.

Collagen is the main structural protein in the skin and provides strength and support. It forms a framework that gives the skin its firmness and smoothness. As we age, the collagen fibers become more rigid and less flexible, leading to the formation of wrinkles.

Elastin, on the other hand, is a protein that allows the skin to stretch and bounce back into shape. It provides elasticity to the skin, allowing it to maintain its smooth appearance. With age, the production of elastin decreases, resulting in the loss of skin elasticity and the formation of wrinkles.

So, in summary, aging skin wrinkles because collagen becomes more rigid and elastin is reduced.

Moving on to the second part of the question, normal body cells have a limited number of times they can divide before they eventually die. This limit is known as the Hayflick limit, estimated to be around 80 to 90 cell divisions. Each time a cell divides, it needs to make a copy of its chromosomes, which contain the genetic material.

The ends of chromosomes are protected by structures called telomeres, which are made up of repetitive DNA sequences. These telomeres act as protective caps, preventing the chromosomes from fraying or sticking to each other. However, with each cell division, a portion of the telomeres is lost due to the limitations of the DNA replication process.

Eventually, after multiple divisions, the telomeres become too short to protect the chromosomes effectively. At this point, the cell enters a state known as replicative senescence, which means it can no longer divide. A cell dies when only a tiny portion of the telomere remains, and it is unable to replicate further.

So, the gradual shortening of telomeres with each cell division is one of the factors contributing to cellular aging and eventual cell death.

In conclusion, aging skin wrinkles due to the increased rigidity of collagen and reduced production of elastin. Additionally, normal body cells have a limited number of times they can divide due to the gradual loss of telomeres, leading to cell death.