in which of the following locations does fertilization of an egg cell typically occur?

A spectrophotometer is an instrument that measures the intensity of light absorbed after it passes through a sample solution. With the spectrophotometer, the concentration of a chemical substance can be determined by measuring the intensity of light detected.

A chlorine molecule contains the fewest covalent bonds among the options provided. It consists of two chlorine atoms bonded together by a single covalent bond. Compared with the other options, ammonia has three covalent bonds, methane has 4 while water has 2.

Melanocytes are specialized skin cells that produce melanin, which is the protective skin-darkening pigment. They are found mainly in the epidermis, though they occur elsewhere, such as in the hair.

Helper T cells are important cells that stimulate the action of other immune cells. For instance, they not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.

The digestive system breaks down complex food substances into small and less complex absorbable compounds. Proteins, for instance, are broken down to constituent amino acids through a digestion process that combines mastication and enzymatic breakdown.

• Potassium is an alkali metal, which tends to lose one electron to form a cation with a \(\pm1\) charge.
• Likely to become a cation.

Rationale

Chromatin refers to a complex of DNA and proteins in human cells. This material is packaged by histones to make up the chromosomes. The chromosomes then contain genetic information that is heritable.

Browning of the apple surface is due to the action of the enzyme polyphenol oxidase. Lemon juice is acidic and lowers the pH of the apple's surface. This inactivates the enzyme polyphenol oxidase, which works best at a neutral pH. This in turn reduces the browning action on the apple.

Crushing a solid reactant into powder increases the surface area of the reactant, thereby increasing chemical reaction. This is because more of the reacting molecules or ions are exposed to the other reactant, which increases the chance of particles colliding and leads to more successful collisions per second.

Most of the carbon dioxide from the blood moves into the alveoli through the process of diffusion down a concentration gradient. In the lungs, there is a higher concentration of carbon dioxide in the blood compared to the alveoli. Its molecules, therefore, move from an area of higher concentration (blood) to an area of lower concentration (alveoli) until equilibrium is reached. This is a passive process and does not require energy or carrier proteins.