your hair is composedof protein known as keratins that have an alpha helix- like
ID: 23428 • Letter: Y
Question
your hair is composedof protein known as keratins that have an alpha helix- like fibrous structure. the alpha helix-structure has approximately 3.6 amion acids per turn of of the helix and a linear dimension of 0.54nm per turn of the helix. for simplicity, let's imagine that a strand of hair is composed of a single keratin molecule in this alpha helix-like state. if you were to grow 25mm(~1inch) in one year, how many turns of alpha helix must be added to the keratin molecule each minute of the year?Explanation / Answer
The large-scale characteristics of proteins are consistent with their secondary structures. Proteins can be either fibrous (derived from fibers) or globular (meaning, like a globe). Fibrous proteins are usually important in forming biological structures. For example, collagen forms part of the matrix upon which cells are arranged in animal tissues. The fibrous protein keratin forms structures such as hair and fingernails. The structures of keratin illustrate the importance of secondary structure in giving proteins their overall properties. Alpha keratin is found in sheep wool. The springy nature of wool is based on its composition of alpha helices that are coiled around and cross-linked to each other through cystine residues. Chemical reduction of the cystine in keratin to form cysteines breaks the cross-links. Subsequent oxidation of the cysteines allows new cross-links to form. This simple chemical reaction sequence is used in beauty shops and home permanent products to restructure the curl of human hair—the reducing agent accounts for the characteristic odor of these products. Beta keratin is found in bird feathers and human fingernails. The more brittle, flat structure of these body parts is determined by beta keratin being composed of beta sheets almost exclusively. Globular proteins, such as most enzymes, usually consist of a combination of the two secondary structures—with important exceptions. For example, hemoglobin is almost entirely alpha-helical, and antibodies are composed almost entirely of beta structures. The secondary structures of proteins are often depicted in ribbon diagrams, where the helices and beta sheets of a protein are shown by corkscrews and arrows respectively 3.6 amion acids per turn of of the helix and a linear dimension of 0.54nm per turn of the helix. so nm/acid=.54/3.6=.15nm/acid 25inch of growth responds= 25*2.54 =63.5 cm no.of turns in 63.5 cm=63.5 *10^7 nm/.15nm =4.23*10^9 turn now turn per minute=4.23*10^9 turn /(365*24*60) hence ...... total turn per min= 8054
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