Unit 2 AP Biology Vocabulary and Explanations

1. Cell Theory - A fundamental theory stating that all living organisms are composed of cells, which are the basic units of life.

2. Prokaryotic Cell - A single-celled organism that lacks a membrane-bound nucleus; examples include bacteria.

3. Eukaryotic Cell - Cells that contain a nucleus and membrane-bound organelles, found in organisms such as plants and animals.

4. Plasma Membrane - The semipermeable membrane surrounding the cytoplasm of a cell, consisting of a lipid bilayer with embedded proteins.

5. Organelles - Specialized subunits within a cell that have specific functions, like mitochondria and ribosomes.

6. Cytoplasm - A jelly-like fluid that fills a cell and contains organelles and other substances necessary for cell function.

7. Ribosomes - Molecular machines in cells responsible for synthesizing proteins by translating messenger RNA (mRNA).

8. Endoplasmic Reticulum (ER) - An organelle that forms an essential part of the fabric of the cell; can be rough (with ribosomes) or smooth (without ribosomes) and is involved in protein and lipid synthesis.

9. Golgi Apparatus - Also known as the Golgi complex, this organelle modifies, sorts, and packages proteins for secretion or delivery to other organelles.

10. Mitochondria - Known as the powerhouses of the cell, they generate ATP through cellular respiration, converting chemical energy from food into usable energy.

11. Chloroplasts - Organelles in plant cells that conduct photosynthesis, converting solar energy into chemical energy stored in glucose.

12. Cell Wall - A rigid layer found outside the plasma membrane of plant cells, providing structural support and protection.

13. Homeostasis - The process by which living organisms maintain a stable internal environment despite external changes.

14. Diffusion - The movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached.

15. Osmosis - The specific diffusion of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

16. Active Transport - The movement of substances across a cell membrane against their concentration gradient, requiring energy in the form of ATP.

17. Passive Transport - The movement of substances across a cell membrane without the need for energy input, including diffusion and osmosis.

18. Facilitated Diffusion - A process of passive transport where substances cross a cell membrane with the help of transport proteins.

19. Semi-permeable Membrane - A membrane that allows certain molecules or ions to pass through it by diffusion and occasionally by facilitated diffusion.

20. Vesicles - Small membrane-bound sacs that transport materials within and outside the cell, as well as within organelles.

21. Cytoskeleton - A network of fibers providing structural support for the cell, aiding in movement and division.

22. Lysosomes - Organelles containing digestive enzymes to break down waste materials and cellular debris.

23. Peroxisomes - Organelles that contain enzymes for metabolizing fatty acids and detoxifying harmful substances, like hydrogen peroxide.

24. Nucleus - The membrane-bound organelle that contains the cell's genetic material (DNA) and is responsible for regulating cellular activities.

25. Nucleolus - A dense region within the nucleus where ribosomal RNA is produced and assembled with proteins to form ribosomal subunits.

26. Chromatin - The complex of DNA and proteins found in the nucleus of eukaryotic cells; it condenses to form chromosomes during cell division.

27. Centrioles - Paired structures that play a crucial role in cell division by helping organize the mitotic spindle.

28. Cilia - Short, hair-like structures on the surface of some cells that help with movement and sensing environmental changes.

29. Flagella - Long, whip-like structures used for locomotion in some cells, like sperm cells.

30. Endocytosis - The process by which cells take in substances by engulfing them in a vesicle formed from the plasma membrane.

31. Exocytosis - The process by which cells expel materials in vesicles that fuse with the plasma membrane, releasing their contents outside the cell.

32. ATP (Adenosine Triphosphate) - The primary energy carrier in all living organisms, composed of adenine, ribose, and three phosphate groups.

33. Photosynthesis - The process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, using carbon dioxide and water.

34. Cellular Respiration - The process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.

35. Glycolysis - The first step of cellular respiration, occurring in the cytoplasm, where glucose is broken down into pyruvate, producing a small amount of ATP.

36. Krebs Cycle - A series of enzymatic reactions in the mitochondria that generate electron carriers and ATP from the breakdown of acetyl-CoA.

37. Electron Transport Chain - A series of protein complexes and other molecules that transfer electrons to create a proton gradient for ATP synthesis during cellular respiration.

38. Chlorophyll - The green pigment found in chloroplasts that captures light energy for photosynthesis.

39. Stroma - The fluid-filled space inside chloroplasts where the light-independent reactions of photosynthesis occur.

40. Thylakoid - Membrane-bound compartments in chloroplasts where the light-dependent reactions of photosynthesis take place, containing chlorophyll.

41. Signal Transduction - The process by which cells respond to external signals through receptors that trigger cellular responses.

42. Ligands - Molecules that bind to receptors to initiate a biological response or signal transduction pathway.

43. Receptors - Proteins found in or on the surface of cells that receive and respond to signals from external stimuli.

44. Enzymes - Biological catalysts that speed up chemical reactions in the body without being consumed in the process.

45. Activation Energy - The minimum amount of energy required to start a chemical reaction, which enzymes help to lower.

46. Substrate - The specific reactant that an enzyme acts upon during a biochemical reaction.

47. Catalyst - A substance that increases the rate of a chemical reaction without undergoing permanent chemical change itself.

48. Feedback Inhibition - A regulatory mechanism wherein the end product of a metabolic pathway inhibits an enzyme involved in its synthesis to prevent overproduction.

49. Apoptosis - The process of programmed cell death that occurs in multicellular organisms as part of growth and development or in response to cellular damage.

50. Cell Cycle - The series of phases (G1, S, G2, and M) that a cell goes through to grow and divide into two daughter cells.