Science Questions

1. Active transport- The movement of a chemical substance through a gradient of concentration or electrical potential in the direction opposite to normal diffusion, requiring the expenditure of energy: active transport across a cell membrane.

2. Cell- The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semi permeable cell membrane.

3. Cell membrane- The semi permeable membrane that encloses the cytoplasm of a cell.

4. Cell theory- a theory in biology that includes one or both of the statements that the cell is the fundamental structural and functional unit of living matter and that the organism is composed of autonomous cells with its properties being the sum of those of its cells

5. Cell wall- a theory in biology that includes one or both of the statements that the cell is the fundamental structural and functional unit of living matter and that the organism is composed of autonomous cells with its properties being the sum of those of its cells

Chloroplast- A chlorophyll-containing plastid found in algal and green plant cells.

6. Chromatin- A complex of nucleic acids and proteins, primarily histones, in the cell nucleus that stains readily with basic dyes and condenses to form chromosomes during cell division

7. Chromosome- A threadlike linear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information.

8. Concentration- The amount of a specified substance in a unit amount of another substance.

9. Cytoplasm- The protoplasm outside the nucleus of a cell

Cytoskeleton- The internal framework of a cell, composed largely of actin filaments and microtubules.

10. Diffusion- The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.

DNA- A nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics.

11. Endocytosis - A process of cellular ingestion by which the plasma membrane folds inward to bring substances into the cell.

Endoplasmic reticulum- A membrane network within the cytoplasm of cells involved in the synthesis, modification, and transport of cellular materials.

12. Eukaryote- A single-celled or multicellular organism whose cells contain a distinct membrane-bound nucleus.

13. Exocytosis - A process of cellular secretion or excretion in which substances contained in vesicles are discharged from the cell by fusion of the vesicular membrane with the outer cell membrane.

14. Facilitated diffusion- in cell biology, a process by which substances are transported across cell membranes by means of protein carrier molecules; also called facilitated transport

Golgi apparatus- A network of stacked membranous vesicles present in most living cells that functions in the formation of secretions within the cell. Also called Golgi body, Golgi complex.

15. Lipid bilayer- the basic structure of a cell membrane consisting of a double layer of phospholipid molecules

16. Lysosome- A membrane-bound organelle in the cytoplasm of most cells containing various hydrolytic enzymes that function in intracellular digestion.

17. Microfilament- Any of the minute fibers located throughout the cytoplasm of cells, composed of actin and functioning primarily in maintaining the structural