Discovery of Cells

The first scientist to look at cells under a microscope was the English scientist Robert Hooke

Common feature in all cell:

Plasma membrane :the border of cell and function to regulate passage of materials into and out of cell

Nucleus :region contain genetic material

Cytoplasm :the components enclosed by the plasma membrane

Two Cell types

Prokaryotic Cells do not have an organized nucleus

surrounded by an envelope and are relatively small (1-10 um)

compose two domains Eubacteria and Archaebacteria

Eukaryotic Cells are much larger and have an organized

nucleus enclosed by a nuclear envelope

Eukarya forms 4 kingdoms :the animals ,plants ,protists

and fungi

Common ancestor

Archaea Eubacteria Eukaryota

Protista Kingdom Fungi

Kingdom Plant

Kingdom Animal

Eubacteria (Prokaryotes)

Three fundamental bacterial cell shapes

Cocci

Bacilli

Spirilli

Exe 4-1

bacteria in yoghurt

Yogurt is a nutrient-rich culture of lactic acid bacteria such as lactobacillus

These bacteria live on lactose (milk sugar) and converts milk to yogurt

To observe bacteria in yogurt the following procedure is employed

Place a very small amount of yogurt on slides by using tooth pick , spread yogurt by using other slide (smear)

Add one drop of methylene blue to the yogurt and place the cover slip

Observed under microscope

Exe 4-2

Cyanobacteria

Photosynthetic prokaryotes

Live in aquatic environment

E.x : Anabaena

Is filamentous organism and each filament is composed of long chains of greenish cells

Exe 4-3

Eukaryotic cells

The nucleus is separated from the rest of the protoplasm by a double membrane (nuclear envelope)

Human cheek cells (animal cell)

The lining inside your mouth is composed of many cell layers that serve to protect your body by forming a barrier

Exe 4-4

Human skin cells (animal cells) Exe 4-5

Microscope

Onion epidermal cells

The onion is an underground ,storage structure made up of thickened modified leaves called scales.

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