Chapter 3 Cells : The Basic Units of Life

5 Levels of Organization of All Living Things 1. Cells – the basic unit of life 2. Tissues – cells working together ( muscles, nerves, blood) 3. Organs – tissues working together ( heart, kidneys, stomach, skin ) 4. Organ Systems – Organs working together ( Circulatory, Nervous, Digestive)

5. Organism – organ systems working together; (an entire living thing that carries out all the basic life functions)

Cell Theory 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of life in all living things. 3. All cells come from existing cells.

Two Types of Cells 1. Prokaryotic cells – do not have a nucleus or any membrane covered organelles; the circular DNA is bunched up in the cytoplasm ( bacteria ) p. 66 2. Eukaryotic cells – have a nucleus and cell organelles (p. 67 )

The Cell Organelles

Cell Wall Found only in plants Allows the plant to maintain its shape Helps to protect and support the structure of a plant Is made of cellulose ( long chains of sugar molecules ) p. 69

Cell Membrane Provides protection and support for the cell Controls movement of materials into and out of the cell ( gate keeper of the cell ) For an animal cell it forms the outer covering For plant cells it is located just inside the cell wall P. 68 - 69

Nucleus Control center of the cell ( the brain ) Chromosomes are located in the nucleus Nuclear membrane – covering that protects the nucleus Nucleolus – the dark area in the nucleus that is made up of protein and RNA P. 69

Cytoplasm Thick, jelly-like substance between the nucleus and the cell membrane The cell organelles float around in the cytoplasm P. 63

Endoplasmic Reticulum (ER) Passageways that lead out from the nuclear membrane to the cell membrane and other parts of the cell It creates some proteins Helps keep the correct level of nutrients in the cell Can be smooth ( no ribosomes attached ) Can be rough ( ribosomes attached ) P. 70

Ribosomes Grain-like bodies attached to the endoplasmic reticulum or free floating in the cytoplasm Protein builders of the cell P. 70

Mitochondria “Powerhouse” of the cell Makes the energy known as ATP The more mitochondria a cell has, the more active the cell is ( muscle cells have a lot ) The only place where oxygen is combined with food to release energy P. 71

Vacuoles Water-filled sack floating in the cytoplasm Storage tank for the cell ( may contain food, oil, waste ) More important to the survival of a plant cell Much larger in a plant cell P. 73

Golgi Complex Combines molecules that are to be sent out of the cell Creates Lysosomes P. 72

Lysosomes Contains enzymes that digest food molecules and injured cell parts Common in animal cells Not often found in plant cells P. 74

Chloroplast The organelle of plant cells in which photosynthesis takes place Contains green pigments called chlorophyll P. 71 or p. 74

Cell Specialization Each cell performs a specialized function Occurs only in multicellular organisms

Division of Labor Each part has a specific job to do