I. Introduction to Cells Chapter 7-1

A. Discovering Cells Problem -- we can’t see cells with naked eye First cells seen & recognized were in plants, not animals The cell walls make them visible Figure: 04-15 Title: Common Structures in Animal and Plant Cells Caption: Common Structures in Animal and Plant Cells.

First description of cells By Robert Hooke In 1665 He Named them for a monk’s cell Referring to bare walls

Frog cartilage From pig embryo Further ID of cells Description of cells from many organisms T. Schwann in 1839 Frog cartilage From pig embryo

B. Cell theory The smallest unit of life is a cell. All life is either a cell, or is composed of cells. Every cell comes from another cell. Human beings cannot form cells from scratch in lab yet apparently, nature made cells from simple molecules only once

3 How many types of cells are in this picture? Figure: 04-00UN3c Title: Red and White Blood Cells Caption: (c) Human red and white blood cells inside a blood vessel. The large, dark ovals that can be seen in the background are flat cells that form the interior lining of the blood vessel. 3

A specialized nasal nerve cell Figure: 04-01 Title: Cells Can Specialize Caption: In more complex organisms, different cells carry out different functions. In the picture at left, you can see one type of cell,—a nerve cell, in this case located in the lining of the nose and surrounded by gray accessory cells. A closer look at one of these nerve cells, in the picture at right, shows a number of hair-like extensions, called cilia, protruding from it. When we smell muffins in the oven, gas molecules that waft off the muffins bind with the cilia, which sets in motion a nerve impulse to the brain about the muffins. A specialized nasal nerve cell

C. 2 Cell Types Prokaryotes Eukaryotes Bacteria Plants Animals Fungi & Others

2. Differences between the 2 types Location of the DNA Eukaryotes = In the membrane bound nucleus Prokaryotes = In the cytoplasm Size Eukaryotes are “large” visible at 100x Prokaryotes are tiny Visible at 1000x

Organization Organelles Eukaryotes are often multicellular (like us) Prokaryotes are all unicellular Organelles Eukaryotes have small membrane bound inner parts called organelles Prokaryotes do not have membrane bound organelles

Metabolism Eukaryotes usually need oxygen Prokaryotes can often live without oxygen

D. Cell Sizes Cells are tiny 85x 425x 2100x 0.1mm – 0.0001mm Ex) Bacteria on the Tip of a Pin Title: Hidden Life Caption: Microscope enlargements of the tip of this pin show an abundance of life—in this case bacteria—thriving on an object that we normally think of as being devoid of living organisms. 85x 425x 2100x

Figure: 04-02-02UN Title: Little and Big Caption: The sizes of some selected objects in the natural world.

Why So Small? Volume increases much faster than surface area. Surface Area = 4π r2 Volume = 4/3π r3 Limited surface = limited import of everything Food