Biochemical Basics

Question 1

A chemical substance that cannot be broken down further using standard chemical techniques is known as:

Answer 1

An element

For example, carbon (C) is an element. Atoms of a particular element always have the same number of protons. For example, all carbon atoms have 6 protons!

Question 2

What is the difference between an atom, a molecule, and a compound?

Answer 2

An atom is the fundamental unit of matter. Atoms contain protons, neutrons, and electrons.
A molecule is a group of two or more atoms, connected by chemical bonds (for example, O2).
A compound is a molecule that contains atoms of more than one element (for example, H2O).

Question 3

Which of the following are contained within the nucleus of a typical atom?

Protons
Neutrons
Electrons

Answer 3

A typical atomic nucleus contains protons and neutrons. Electrons are not found in the nucleus; instead, they are located in regions (“shells”) surrounding the nucleus.

Question 4

Isotopes are atoms with the same number of:

Answer 4

protons

Isotopes are atoms with the same number of protons, meaning that they must represent the same element. Isotopes differ in their number of neutrons.

Question 5

Define:

ionic bond

Answer 5

A chemical bond that forms due to the transfer of specific electrons from one atom to another, with one atom losing an electron and the other gaining it.

The atom that gains electrons is given a negative charge, while the atom that gives up electrons is given a positive charge.

Question 6

Define:

covalent bond

Answer 6

A chemical bond that forms via the sharing (not complete transfer) of electrons.

When the electrons are shared unequally, the bond is polar covalent. For example, H2O contains two polar covalent bonds between H and O, because these atoms have different electronegativities (attraction to electrons in a bond).

When the electrons are shared equally, the bond is nonpolar covalent. For example, O2 contains a nonpolar covalent bond between the two O atoms, which have the same electronegativity.

Question 7

What is the chemical formula for water, and is the water molecule polar or nonpolar?

Answer 7

Water has a formula of H2O, and it is polar. The water molecule is bent due to the presence of two lone pairs on the central oxygen atom. Oxygen is more electronegative than hydrogen, so the oxygen atom will carry a partial negative charge, while the hydrogen atoms will be partially positive. Molecules with asymmetrical charge distributions like this one are polar.

Question 8

How do hydrogen bonds differ from ionic or covalent bonds?

Answer 8

Hydrogen bonds are intermolecular, which means they occur between two or more different molecules. Ionic and covalent bonds are intramolecular, meaning they connect atoms within a single molecule.

Hydrogen bonds are attractive forces.

Question 9

Define:

a hydrophilic compound

Answer 9

One that is attracted to water.

Since water is polar, it tends to attract other polar compounds.

Question 10

Define:

a hydrophobic compound

Answer 10

One that is repelled by water.

Since water is polar, it tends to repel nonpolar compounds. A classic example is an oil slick on the top of the ocean. Oil is nonpolar, so it is not attracted to the ocean water, and the two liquids do not mix.

Question 11

Define:

macromolecule

Answer 11

A molecule that contains an extremely large number of atoms.