3. The skin protects the body by providing three types of barriers. Classify each of the protective factors listed below as an example of a chemical barrier (C),
a biological barrier (B), or a mechanical (physical) barrier (M).
1. Langerhans' cells and macrophages
2. Intact epidermis
3. Bactericidal secretions
4. Keratin
5. Melanin
6. Acid mantle

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

Describe the relationship between isotonic solutions, equilibrium, and water movement into and out of a cell.

If a cell is placed into a hypertonic environment, what will happen to it ? a)it will shrink or shrivel b)nothing c)it will burst d) it will expand or enlarge