Cells

Definitions  Cell – the smallest unit of a living organism; surrounded by a thin membrane  Unicellular – an organism consisting of only one cell  Multicellular – living things made up of many cells  Tissue – a group of cells working together  Organ – two or more tissues that work together to perform a specific function  System – organs working together

More Definitions…  Cell Membrane – A cell’s external boundary for the material inside the cell  Cytoplasm – A jellylike substance made mostly of water and containing many substances, such as proteins and fats, that are essential to the cell; found inside the cell membrane  Organelle – A tiny structure inside the cytoplasm of most cells that helps carry out the function of the cell

More Definitions…  Nucleus – a large organelle that contains the chromosomes; separated from the rest of the cytoplasm by its own membranes  Chromosomes – tight bundles of DNA (the coded instructions the cell follows); usually found in the nucleus of a cell  Mitochondria – the cell’s engine; responsible for breaking down the cell’s food and releasing energy  Endoplasmic reticulum (ER) – the cell’s system of passageways that allows material to move from one part of the cell to another

More Definitions…  Ribosomes – responsible for making proteins that the cell needs; also carry out the instructions given to the cell by the DNA  Vacuole – a bubble-like organelle in cells; generally used for storage  Cell wall – a rigid structure that provides support for some kinds of cells  Chloroplasts – organelles that contain chlorophyll; organelles where photosynthesis takes place  Chlorophyll – a green pigment that absorbs energy from sunlight and uses it to produce food and energy for the plant

Cells working together  Unicellular vs. Multicellular  Cells > Tissues > Organs > Systems

Cell Structures  Cells come in all sorts of shapes and sizes  All cells have a cell membrane

Animal Cell

Plant Cell