Chapter 3 Study Guide:
Chemical Compounds in Cells
Key Concepts
An element is any substance that cannot be broken down into simpler substances.
When two or more elements combine chemically, they form a compound.
Most chemical reactions in cells could not take place without water.
Carbohydrates, lipids, proteins, and nucleic acids are important groups of organic
compounds in living things.
Key Terms
Element- Any substance that cannot be broken down into simpler substances.
Compound -Two or more elements that are chemically combined.
Carbohydrate -Energy-rich organic compound, such as a sugar or a starch, that is
made of the elements carbon, hydrogen, and oxygen.
Lipid -Energy-rich organic compound, such as a fat, oil, or wax, that is made of
carbon, hydrogen, and oxygen.
Protein -Large organic molecule made of carbon, hydrogen, oxygen, nitrogen, and
sometimes sulfur.
amino acid -A small molecule that is linked chemically to other amino acids to form
proteins.
Enzyme -A type of protein that speeds up a chemical reaction in a living thing.
nucleic acid -Very large organic molecule made of carbon, oxygen, hydrogen,
nitrogen, and phosphorus, that contains the instructions cells need to carry out all
the functions of life.
DNA -Deoxyribonucleic acid; the genetic material that carries information about an
organism and is passed from parent to offspring.
RNA -Ribonucleic acid; a nucleic acid that plays an important role in the production
of proteins.
The Cell in Its Environment
Key Concepts
Diffusion is the main method by which small molecules move across cell membranes.
Osmosis is important because cells cannot function properly without adequate
water.
Active transport requires the cell to use its own energy, while passive transport
does not.
Key Terms
selectively permeable -A property of cell membranes that allows some substances to
pass through, while others cannot.
Diffusion -The process by which molecules move from an area of higher
concentration to an area of lower concentration.
Osmosis -The diffusion of water molecules through a selectively permeable
membrane.
passive transport -The movement of materials through a cell membrane without
using energy.
active transport -The movement of materials through a cell membrane using cellular
energy.
Photosynthesis
Key Concepts
Nearly all living things obtain energy either directly or indirectly from the energy of
sunlight captured during photosynthesis.
During photosynthesis, plants and some other organisms use energy from the sun to
convert carbon dioxide and water into oxygen and sugars. The equation for
photosynthesis is
Key Terms
Photosynthesis -The process by which plants and some other organisms capture the
energy in sunlight and use it to make food.
Autotroph -An organism that makes its own food.
Heterotroph -An organism that cannot make its own food.
Pigment -A colored chemical compound that absorbs light.
Chlorophyll -A green pigment found in the chloroplasts of plants, algae, and some
bacteria.
Stomata -Small openings on the underside of a leaf through which oxygen and
carbon dioxide can move.
Respiration
Key Concepts
During respiration, cells break down simple food molecules such as sugar and
release their stored energy. The respiration equation is
Fermentation provides energy for cells without using oxygen.
Key Terms
Respiration -The process by which cells break down simple food molecules to
release the energy they contain.
Fermentation -The process by which cells break down molecules to release energy
without using oxygen.
Cell Division
Key Concepts
During interphase, the cell grows, makes a copy of its DNA, and prepares to divide
into two cells.
During mitosis, one copy of the DNA is distributed into each of the two daughter
cells.
During cytokinesis, the cytoplasm divides. The organelles are distributed into the
new cells.
Because of the way in which the nitrogen bases pair with one another, the order of
the bases in each new DNA molecule exactly matches the order in the original DNA
molecule.
Key Terms
cell cycle -The regular sequence of growth and division that cells undergo.
Interphase -The stage of the cell cycle that takes place before cell division occurs.
replication -The process by which a cell makes a copy of the DNA in its nucleus.
Mitosis -The stage of the cell cycle during which the cell’s nucleus divides into two
new nuclei and one copy of the DNA is distributed into each daughter cell.
Chromosome -A doubled rod of condensed chromatin; contains DNA that carries
genetic information.
Cytokinesis -The final stage of the cell cycle, in which the cell‘s cytoplasm divides,
distributing the organelles into each of the two new cells.