Chapter 7.1 Life is Cellular

Daily Objectives Be able to state the 3 parts of the cell theory. Describe how the different types of microscopes work. Distinguish between prokaryotes and eukaryotes.

Cells Cells = Basic unit of life! All life is composed of cells. Cells can be many different sizes (always small)

Early Scientists 1600’s Anton van Leeuwenhoek Observed tiny living organisms in water using a microscope He was one of the first to use a microscope to study nature

Early Scientists 1600’s Robert Hooke Used light microscope to look at thin slices of plant tissue Saw thousands of tiny chambers and called them cells

Early Scientists 1800’s Matthias Schleiden Theodor Schwann Concluded all plants are made of cells Theodor Schwann Concluded all animals are made of cells

Early Scientists 1800’s Rudolf Virchow New cells can only be produced from the division of existing cells

The Cell Theory The Cell Theory: All living things are composed of cells Cells are the basic unit of structure and function in living things New cells are produced from existing cells

Exploring the Cell A microscope produces an enlarged image of something very small. Most microscopes use lenses to magnify the image of an object by focusing light or electrons Microscopes available today are much better than early microscopes.

Compound Light Microscope A typical light microscope allows light to pass through a specimen and uses two lenses to form an image. First lens = Objective Lens Second Lens = Ocular Lens

Cell Stains One problem with light microscopy is that most cells are nearly transparent. In order to view the cells scientists use chemical stains or dyes. Onion cells stained with methylene blue

Electron Microscopes Can be used to study cellular structures that are as small as 1 billionth of a meter in size. Higher resolution (clarity) than light microscopes There are two major types of electron microscopes: Transmission Electron Microscope (TEM) Scanning Electron Microscope (SEM)

Transmission Electron Microscopes (TEM) Make it possible to explore cell structures and large protein molecules. Specimen must be cut into ultrathin slices so that the beam of electrons can pass through. (Appears 2 Dimensional) Mitochondria (TEM) Nucleus (TEM)

Scanning Electron Microscopes (SEM) Beam of electrons is scanned over the surface of a specimen. Scanning electron microscopes produce stunning 3 dimensional images of the specimen’s surface. Pollen (SEM)

Types of Cells Cells come in a variety of shapes and sizes. Cells fall into two broad categories, depending on whether they contain a nucleus. Prokaryotes – Cells that do not enclose DNA in a nucleus. Ex. bacteria Eukaryotes – Cells that enclose their DNA in a nucleus. Ex. Plants, animals, and protists Both types of cells contain DNA, cytoplasm, and cell membranes.

Prokaryotes and Eukaryotes

Prokaryotes Prokaryotic cells are generally smaller and simpler than eukaryotic cells. Do not have a nucleus Despite their simplicity, they carry out every activity associated with living things They grow, reproduce, respond to the environment, etc. Always single-celled organisms

Eukaryotes Generally larger and more complex than prokaryotic cells Most eukaryotic cells contain dozens of structures and internal membranes, and many are highly specialized. Eukaryotes can be single-celled (protists) or multicellular (animals and plants)

Plant Cell

Animal Cell

Review of Daily Objectives What are the 3 parts of the cell theory? How do the different types of microscopes work? What’s the main difference between a prokaryote and eukaryote?