Unit 2

Cells and Their Organelles

Cell Theory•States that all living things are made of cells, cells are the basic unit of life, and cells come from preexisting cells.

Unicellular Organisms•Made of a single cell.

Multicellular Organisms

•Made of more than one cell

Organelles•Small structures in cells.

Chlorophyll•Green pigment in plant cells that trap sunlight.

Enzymes•Proteins that speed up reactions

Prokaryotic Cells•Single cell

Eukaryotic Cells•More than one cell.

DNA•Instructions for genetic traits and making proteins.

Cell Division•The process when cells makes new cells.

Differentiated•The process of cells being able to perform many jobs and functions

Stem Cells•Cells that have the potential to develop into many different cell types in the body during early life and growth; and are able to repair systems, dividing without limit to replenish other cells.

Homeostasis•To maintain a balance of internal conditions with external conditions.

Permeable Membrane•When all materials are allowed to move through the membrane

Semipermeable Membrane

•When some materials are allowed to move through the membrane

Selectively Permeable Membrane

•When specific materials are allowed to move through the membrane

Passive Transport•When materials are allowed to move down the concentration gradient without needing energy

Active Transport•When materials are allowed to move up the concentration gradient and require energy.

Diffusion•When materials move from higher concentration to lower concentration

Concentrated Gradient•The movement of materials along a barrier

Osmosis•Movement of water molecules down the concentration gradient

Lyse•to cause or produce a breakdown of a compound, substance, or cell (bursting).

Facilitated Transport•Movement of materials that require help to move.

Transport Proteins•Materials that help to move other materials along a barrier.

Endocytosis•Movement of materials into the cell by vesicles.

Exocytosis•Movement of materials out of the cell by vesicles

Cell Cycle•A series of events that take place in a cell, leading to its division and duplication.

Interphase•The resting stage of cell division in which DNA duplicates

Gap 1 Phase (GI)•A period in the cell cycle during interphase, in which the major period of cell growth takes place and new organelles are made.

Synthesis Phase•The phase during interphase of cell division in which the DNA molecules are replicated.

Chromatid•One-half of two identical copies of a replicated chromosome

Centromere•The structure that holds chromatids together

Gap 2 PhaseThe final sub-phase of interphase when the cell readies itself for mitosis

Mitosis•The second phase of cell division in which the nucleus divides into two nuclei

Prophase•The phase in mitosis in which the spindles form and the nuclear membrane begins to disappear

Metaphase•The phase in mitosis in which the chromosomes line up at the equator

Anaphase•The phase in mitosis in which the chromosomes begin to separate and move to opposite ends of the cell.

Telophase•The phase in mitosis in which the nucleus separates into two nuclei while the cytoplasm pinches inward.

Cytokinesis•The phase in cell division in which two daughter cells form.

Cleavage Furrow•The pinching in of two daughter cells to form the cell membrane in animal cells.

Cell Plate•The structure that forms between two daughter cells in plant cells to form the cell wall

Chemical Control System

•System that regulates chemical reactions in organisms

Internal Signal•Stimuli inside the organisms that turn cell division on or off, such as hormones.

External Signal•Stimuli outside the organism that turn cell division on or off, such as weather

Checkpoint•Control mechanisms that ensure the continuation of cell division

Cancer Cells•Condition in which the cell cycle goes out of control.

Malignant Tumor•Tumor that can be lethal because it has cancer cells that break away from the tumor and travel to other parts of the body.

Benign Tumor•Harmless tumor because the cells stay together and can be removed.

Biochemical Reactions•Reactions that occur in living organisms

Activation Energy•Energy needed to start a reaction

pH•Scale used to measure the strength of an acid or a base

Buffers•Substances used to neutralize the level of acids and bases in organisms

Catalyst •Substances used to speed up the rate of reactions