The Cell Cell Theory Microscope Types of cells Cell Structures

Cell Theory Origin of theory – Magnification began with a single lens in the late 1500s – By the 1600s the telescope and microscope had been invented using a combination of lenses – Anton von Leeuwenhoek was one of the first to observe and record small living things in pond water – 1665 Robert Hooke used the 1 st light microscope to look at plant tissue. When he looked at cork (bark form a tree) he noticed very neat and organized chambers he called them “cells”

Cell Theory continued Between 1838 and 1839 Schleiden and Schwann had concluded that all plants and animals were composed of cells Virchow proposes that all cells come from existing cells to complete the cell theory.

*The Cell Theory 1.All living things are composed of cells 2.Cells are the basic units of structure and function in living things 3.New cells are produced from existing cells

Microscopes Microscope comes from the words … micro meaning “small” and scope meaning to “see”

Magnification is how much bigger a sample appears to be under the microscope than it is in real life. Overall magnification = Objective lens x Eyepiece lens Resolution is the ability to distinguish between two points on an image i.e. the amount of detail How it works…

Step 1 Place a clean slide onto the work surface. Step 2 Place the sample to be observed in the center of the slide. If the sample is already in a liquid suspension, skip to Step 5. If not, you will need to add a liquid medium to suspend the sample for viewing. Step 3 Add a drop of distilled water over the top of the sample. Step 4 Place the cover glass next to the droplet along one edge as shown in the diagram. The side resting against the glass will act as the pivot point as you lower the cover glass over the sample. Step 5 Lower the cover glass into place. As you hinge the glass downward, the drop will spread outward and suspend the sample between the slide and cover glass for optimal viewing Preparing a wet mount slide

Advantages: can see living specimen Disadvantage: limited to size and resolution Uses a 2 lens and a light source Total magnification is eyepeice x objective Compound Light microscope

Advantages of SEM: can see detailed structures and textures of the cell or virus Disadvantage: can not view live specimen Creates a vaccum and bombards metal coated specimen with electrons Scanning electron microscope

Advantages: see detailed images of interior of cells Disadvantages: because the specimen is thinly sliced the images do not show active function but a picture in time. Transmitting electron microscope

Types of Cells

Prokaryotic cells Prokaryotes have No nucleus Prokaryotes have No inner membranes All prokaryotes are bacteria, all bacteria are prokaryotes Ex E.Coli which lives in your intestine

Eukaryotic Cells Eukaryotes have a nucleus which contains the chromosomes Eukaryotes have inner membranes and organelles with membranes All living things except bacteria are Eukaryotic, this includes Protista, Fungi, Plant, and Animal

Plant cells

Animal Cells Animal cells have no cell wall and no chloroplast Animal cells do have lysosomes Animal cells can have flagella or cilia which allow them to move AmoebaMuscle Cells