Human hair is composed of the protein keratin At the hair sa

Human hair is composed of the protein keratin. At the hair salon, two techniques are used to modify the three-dimensional shape of hair. Styling involves heat, and a perm involves cleaving and re-forming disulfide bonds. How would you investigate these phenomena in terms of protein structure? The image below shows a community. According to the hierarchy of biological systems, what level is created with the addition of nonliving components like sunlight and rain? The results in Dr. Hayes\'s comparative experiments were more variable than the results from his controlled experiments. How would you explain this?

Solution

7.Hair is made up of a protein known as keratin. Keratin is composed of long chains of amino acids.The strength of hair can be attributed to a special property unique to proteins like keratin, which are made up of a large number of sulfur-containing amino acids. Sulfur atoms, from adjacent chains of keratin, bond together to form disulphide bonds. These extra bonds make the fibers that have keratin very strong. In addition, they ensure that the position of the keratin molecules remains fixed, such that the shape of the hair fiber stays the same.The extreme heat causes the disulphide bonds to break. This breakage allows the keratin chains to move around slightly and assume a position that results in straightened hair. When the hair cools down, the disulphide bonds between the keratin are reformed.

Permanent hair straightening techniques use harsher methods, with chemicals, to break the disulphide bonds and reform them. The disulphide bonds cannot be broken apart by oxidizing agents, which are acids, but can be broken apart by strong reducing agents, which are bases. Alkaline solutions, therefore, are applied to hair to break apart the disulphide bonds. The hair is then held straight and acidic solutions are applied to it.

The acid neutralizes the base, stopping the disulphide bond cleavage reaction and allowing the disulphide bonds to reform in new positions. Although all chemical hair-straightening techniques have this same basis, each has a slightly different mode of action on the hair. Alkaline hydroxides are the harshest and most rapid agents for breaking the disulphide bonds; usually, either sodium hydroxide or calcium hydroxide is used for this purpose. Along with breaking the disulphide bonds, these solutions also cause the hair to swell. Since they are so harsh, these chemicals should not be left in the hair for more than 10 minutes, as they can cause severe damage to the hair and scalp if not used properly. Hair is usually treated with a cream to protect it from the caustic effects of these chemicals before applying the alkaline hydroxides. Thoroughly washing off the solutions allows the reaction to stop and the disulphide bonds to reform, sealing the hair in its new, straightened position.

8.An ecosystem.An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system. These biotic and abiotic components are regarded as linked together through nutrient cycles and energy flows.

9.The controlled experiments compared the effects of various atrazine concentrations on reproductive tissues.

He studied two groups of frogs that live along the same river in California. For the experiment he placed the frogs, same species, in cages in the water. One group was placed upstream of the Salinas valley, one of the largest agricultural areas of the country, which is farmed intensely all year round. Runoff containing Atrazine and other chemicals from the farms flows into the river.

The other group of frogs was placed about 50 miles downstream in a clean area. He found that the tadpoles in the area near the farms had retarded growth. They were tiny compared to the frogs in the healthier area. Hayes then injected both groups of frogs with bread yeast. The group of frogs near the farms died within a day or two after being injected with the yeast. The other frogs, from the cleaner area upstream of the agricultural area, survived. They were larger and had stronger immune systems and so were able to fight off the effects of the yeast.

According to Hayes, the link between atrazine and altered \"aromatase and estrogen production has been demonstrated... in fish, frogs, alligators, birds, turtles, rats and human cells\", and, he believed that the preponderance of the evidence shows atrazine to be a risk to wildlife and humans.