The "gray matter of the brain is largely made up of which of the following?

From the heart, blood flows through major arteries, which then branch to give rise to arterioles, which then divide into capillaries that deliver blood to the target organ.

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.

Cardiac muscles have intercalated discs that enable them to contract in a coordinated manner. Skeletal muscles do not have intercalated discs, as their contraction is under voluntary control and does not require the same level of synchronization seen in the involuntary contraction of cardiac muscle.

Urea is a nitrogenous waste product that is produced when the liver breaks down proteins and amino acids. It is then excreted from the body via sweat.

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

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.

a. Water boils to produce steam at 100°C - This is a phase change (from liquid to gas) and not a chemical reaction of water.

b. Water dissolves sugar - This is a physical change, not a chemical reaction of water.

c. Water produces gas with sodium metal - This reaction involves the chemical reaction of water with sodium metal to produce hydrogen gas.

d. Water and oil separate when combined - This is a physical separation, not a chemical reaction of water.

A gene is a segment of DNA that codes for a specific protein or polypeptide.

Uracil is the nucleotide that is only found in RNA. The other nucleotides are found in both DNA and RNA

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.