Cells Unit 3 The Discovery of Cells Microscopes

Cells Unit 3

The Discovery of Cells • Microscopes have become an important tool for studying biology • In 1665, Robert Hooke used a simple microscope (30 magnification) to look at a thin slice of cork, in which he saw many “little boxes” • He called them cells because they reminded him of the small rooms in which monks lived

The Discovery of Cells • Ten years later, Anton van Leeuwenhoek used a more powerful microscope (300 magnification) and discovered “tiny animals” that lived in pond water

Cell Theory • In the 1800’s, the cell theory was developed because of the works of Schleiden, Schwann, and Virchow • The cell theory states that: – All living things are made up of one or more cells – Cells are the basic units of structure and function in organisms – All cells arise from existing cells

Cell Size & Shape • Cells vary greatly in size and shape • These variations enable them to perform specific functions in the body • It is important for a cell to have the biggest surface-area-to-volume ratio possible so that nutrients traveling through the cell membrane can reach their destination easily • If a cell is large, its shape will often be one that increases surface-area-to-volume ratio

Cell Size & Shape • Which cell has a bigger surface-area-tovolume-ratio, and therefore, will be more successful?

Cell Features • ALL CELLS HAVE: – Cell Membrane: Outer boundary of cell – Cytoplasm: Fluid in which all contents of cell are suspended – Ribosomes: Where proteins are made – DNA: genetic material

Two types of Cells: The Basics • PROKARYOTIC – Occur individually – No nucleus or other membrane bound organelles – Genetic Material is single loop of DNA – Cell wall surrounds cell membrane for structure – Capsule helps cell cling to surfaces – Ex: Bacteria!! • EUKARYOTIC – “You” have “Eu”karyotic cells – Occur single celled or multicellular – Membrane bound nucleus & other organelles – Includes all cells (plant, animal, fungi, algae) except bacteria – Ex: Skin Cells

Inside the Eukaryotic Cell • Cytoskeleton helps the cell move, keep its shape, and organize its parts – made of protein fibers

Inside the Eukaryotic Cell • There are many organelles in eukaryotic cells, which are membrane bound structures that carry out specific activities • Nucleus: Stores DNA • Endoplasmic Reticulum (ER): System of internal membranes that move protein and other substances throughout cell – Rough ER have ribosomes attached and smooth ER do not

Inside the Eukaryotic Cell • Golgi Apparatus: Modifies, sorts and packages cell products • Lysosomes: Where enzymes digest old, damaged or unused organelles • Mitochondria: Uses energy from macromolecules to make ATP (power house of cell)

Inside the Eukaryotic Cell • PLANT CELLS HAVE ALL OF THE ABOVE PLUS: • Chloroplasts: Use light energy to make food for plants • Central Vacuoles: Store water and waste. When vacuole is full, plants are sturdy • Cell wall: Made of cellulose and provides support

Levels of Cellular Organization • Cell: Smallest unit of life (ex: lung cell) • Tissue: Distinct group of cells that have similar structures and functions (ex: lung tissue) • Organs: Specialized structure that has a specific function (ex: lung) • Organ Systems: Various organs that carry out a major body function (ex: respiratory system)