Chapter 2

Question 1

Cell

Answer 1

The smallest unit of life.

Question 2

Cell membrane

Answer 2

The outer layer or coating that surrounds the cell and controls which molecules enter and leave the cell.

Question 3

Cell wall

Answer 3

A tough, rigid outer covering that protects certain cells and gives them shape.

Question 4

Chloroplast

Answer 4

An organelle that absorbs light energy and converts it to chemical energy for the manufacture of food in the process called photosynthesis.

Question 5

Compound

Answer 5

A chemical combination of atoms of two or more different elements.

Question 6

Cytoplasm

Answer 6

A jelly-like fluid made up of water, salts, and dissolved organic molecules that is enclosed by the cell membrane and provides the right environment for the many chemical reactions needed to produce energy, convert organic molecules into needed proteins, or break down old proteins to be recycled.

Question 7

Cytoskeleton

Answer 7

An internal Skeleton in cells, made of a network of fibers that holds the organelles of the cell in place, maintains the shape of the cell, and provides a system of “tracks” that motor proteins use to move cell products from place to place inside the cell or to the cell membrane.

Question 8

Element

Answer 8

One of the 118 different types of atoms of which all matter is composed.

A substance composed of atoms with the same atomic number.

Question 9

Enzyme

Answer 9

A protein that controls and speeds up chemical reactions without being changed or used up.

Question 10

Eukaryotic cell

Answer 10

A membrane-bound cell that contains a membrane-bound nucleus.

Question 11

Hormone

Answer 11

A protein that directs cells to perform specific tasks.

Question 12

Mitochondrion

Answer 12

An organelle that provides energy for all the energy-requiring processes of cells

Plural of mitochondrion is mitochondria

Question 13

Nucleus (of a cell)

Answer 13

The organelle that directs the cell’s activities and stores DNA

Question 14

Organic molecule

Answer 14

A molecule that contains carbon and hydrogen.

Question 15

Prokaryotic cell

Answer 15

A cell that lacks internal membrane-bound structures such as a nucleus and other organelles.

Question 16

Ribosome

Answer 16

An organelle made of protein and RNA that assembles proteins from amino acids.

Question 17

What causes matter to change state from solid to liquid or from liquid to gas?

Answer 17

The amount of energy in the particles of a substance determine the state it is in. Solids possess the lowest amount of particle energy, liquids possess a greater amount of particle energy, and gases possess the highest amount of particle energy. Th energy in the particles of a substance is increased by heating. Th is is why heating a solid causes it to melt into a liquid, and heating the liquid causes it to vaporize into gas.

Question 18

What determines the chemical identity of an atom?

Answer 18

An atom’s chemical identity is determined by how many protons the atom has in the atomic nucleus.

Question 19

Compare and contrast elements and compounds.

Answer 19

An element is a substance composed of atoms with the same atomic number, that is, all the atoms have the same number of protons in their nuclei. A compound is formed when atoms of two or more diff erent elements are chemically bound together.