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Biology Chapter 4 Key Vocabulary
Section 4.1
1. ATP: Adenosine triphosphate, or ATP, is a molecule that transfers energy from the
breakdown of food molecules to cell processes. The energy carried by ATP is released when a
phosphate group is removed from the molecule.
2. ADP: Adenosine diphosphate, or ADP, is a lower energy molecule that can be converted into
ATP by the addition of a phosphate group.
3. Chemosynthesis: a process by which some organisms use chemical energy instead of light
energy to make energy-storing carbon-based molecules.
Section 4.2
4. Photosynthesis: a process that captures energy from sunlight to make sugars that store
chemical energy.
5. Chlorophyll: a molecule found in chloroplasts (in plant cells) that absorbs some of the energy
in visible light. The green color of plants comes from chlorophyll.
6. Thylakoid: membrane-bound structure within chloroplasts that that contain chlorophyll and
other light-absorbing pigments used in the light-dependent reactions of photosynthesis.
7. Light-dependent reactions: capture energy from sunlight and take place within and across
the membrane of the thylakoids. Water and sunlight are needed for this stage of photosynthesis.
8. Light-independent reactions: use energy from the light-dependent reactions to make sugars.
These reactions occur in the stroma of chloroplasts. Carbon dioxide molecules are needed in
this stage of photosynthesis.
Section 4.3
9. Photosystem: series of light-absorbing pigments and proteins that capture and transfer
energy in the thylakoid membrane.
10. Electron transport chain: series of protein in the thylakoid membranes that aid in converting
ADP to ATP by transferring electrons.
11. ATP synthase: enzyme that catalyzes the reaction that adds a high-energy phosphate group
to ADP to form ATP.
12. Calvin cycle: process by which a photosynthetic organism uses energy to synthesize simple
sugars from CO 2.
Section 4.4
13. Cellular respiration: an aerobic process that releases chemical energy from sugars and other
carbon-based molecules to make ATP when oxygen is present.
14. Aerobic: process that requires oxygen to occur.
15. Glycolysis: anaerobic process in which glucose is broken down into two molecules of
pyruvate and net ATP are produced.
16. Anaerobic: process that does not require oxygen to occur.
17. Krebs cycle: process during cellular respiration that breaks down a carbon molecule to
produce molecules that are used in the electron transport chain.
Section 4.6
18. Fermentation: anaerobic process by which ATP is produced by glycolysis.
19. Lactic acid: product of fermentation in many types of cells, including human muscle cells.