Comprehensive Biology Notes on Cell Systems, Organelles, and Energetics

Cells: The basic unit of structure and function in all living things.
Microscope: An instrument designed to make small objects look larger, enabling the visualization of microscopic cellular structures.
Cell Theory: A fundamental scientific concept explaining the relationship between cells and living things. It states three core principles:
- All living things are made of cells.
- Cells are the basic units of structure and function in living things.
- All new cells are produced from existing cells.

Organelle: A tiny cell structure that carries out a specific function within the cell.
Cell Wall: The rigid supporting layer that surrounds the cells of plants and some other organisms.
Cell Membrane: A thin, flexible barrier that surrounds a cell and controls which substances pass into and out of a cell.
Cytoplasm: Fills the region between the cell membrane and the nucleus.
Nucleus: A large oval organelle that contains the cell's genetic material in the form of DNA and controls many of the cell's activities.
Mitochondria: Organelles that convert energy stored in food to energy the cell can use to live and function.
Chloroplast: An organelle in the cells of plants and some other organisms that captures energy from sunlight and changes it to an energy form that cells can use in making food.
Vacuole: A sac-like organelle that stores water, food, or other materials needed by the cell.

Selectively Permeable: A property of cellular membranes that allows some substances to cross the membrane, 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 across a selectively permeable membrane.
Endocytosis: The process by which the cell membrane takes particles into the cell by changing shape and engulfing the particles.
Exocytosis: A reverse process of endocytosis that allows large particles to leave the cell.

Cell Cycle: The regular sequence of events in which the cell grows, prepares for division, and divides to form two daughter cells.
Interphase: The first stage of the cell cycle in which the cell grows and prepares for division.
Replication: The process occurring within interphase in which the cell makes a copy of the DNA in its nucleus before cell division.
Mitosis: The stage of the cell cycle during which the cell's nucleus divides into two new nuclei and one set of DNA is distributed into each daughter cell.
Cytokinesis: The final stage of the cell cycle, in which the cell's cytoplasm divides, distributing the organelles into each of the two new daughter cells.

Photosynthesis: The process by which cells capture energy in sunlight and use it to make food.
Autotrophs: Also referred to as producers, these organisms are able to create their own food in the form of glucose, an energy-giving sugar.
Heterotroph: An organism that cannot make its own food and must obtain energy by consuming other living things.
Chlorophyll: The green photosynthetic pigment found in the chloroplasts of plants that absorbs sunlight.
Cellular Respiration: The process in which oxygen and glucose undergo a complex series of chemical reactions inside cells, releasing energy.
Fermentation: The process that allows the release of energy from food without using oxygen.