Unit TWO- Chapter 3Cell Structure

Mrs. Cook

Biology

History of the Microscope

• Robert Hooke-• 1665- used an early light microscope to look

at slice of cork from an oak tree. • What he saw looked like little boxes that he

called “cells”• He noticed that the cells of trees, roots and

stems looked similar.

Anton Van Leeuwenhoek•1673- Dutch scientist observed first living cells- “microorganisms”. Invented the microscope.• observed cells from algae called spirogyra and bell-shaped cells on stalks of protists called vorticella.• called these organisms “beasties” and then formally “Animacules” we now call them Protists.

History of the Microscope http://www.youtube.com/watch?v=XgW1HiV9SJs

The Cell Theory

• 1838, German Botanist- Matthais Schleiden said that all plants were made of cells.

• 1839, German Zoologist, Theodor Schwann said the same thing for animals.

• The German Physician, Rudolf Virchow (1821-1902), said that all cells come from other cells.

The Cell Theory

• These ideas were combined to form a basic theory about the cellular nature of life called The Cell Theory.

1. All living things are made of one or more cells.

2. Cells are the basic units of structure and function of organisms.

3. All cells arise from existing cells.

Note: somatic cells = body cells

gametes = sex cells (sperm and eggs)

The Cell Theory Song…http://www.youtube.com/watch?v=KuJqqiATlqw

All living things include the following characteristics

• ORGANIZATION• METABOLISM• CHANGE WITH TIME• RESPOND TO STIMULI• REPRODUCTION• MAINTAIN HOMEOSTASIS• GROWTH & DEVELOPMENT

Microscopes

• The continuous development of microscopes has helped scientists to clarify our definition of life.

Compound Microscope Scanning electron Microscope

Microsopes cont.

• Light microscope: light passes through one or more lenses to produce an enlarged image.

• Electron microscope: forms an image using a beam of electrons rather than light.

• Parts of a microscope:• Magnification- is the quality of making an image

appear larger than the objects actual size.

• Resolution- is a measure of the clarity of an image

Compound Light microscope

Cell Features• We have trillions of cells that range from 5 nanometers in size to 20

nanometers.

• So, Why do we have trillions of little cells instead of fewer larger cells?• This has to do with surface area to volume ratio.

• Smaller the cell, the quicker it can get substances into the cell and to the area that needs them. The larger the cell, the longer it would take for the substances to travel through the cell.

http://youtu.be/wuXSEOKNxN8

Cell Features cont. http://youtu.be/o1GQyciJaTA

• All cells share 3 common features:

1. Cell Membrane (aka plasma cell membrane)-

- the cells outer boundary

-acts as a barrier between the inside and the outside of the cell

- All materials must enter or exit through this• castle walls• Gates to Turnpike

Cell Features Cont. • 2nd feature common to all cells:

2. Cytoplasm-

- the region inside the cell membrane that includes all fluids (Cytosol), organelles (tiny organs), and the nucleus.

Cell features cont.

• 3rd feature common to all cells:

3. DNA

-all cells have DNA for regulating function and reproduction.

- DNA in some cells floats freely

- Other cells have a membrane bound organelle, that contains the cells DNA, called the Nucleus.

Two Basic Types of Cells

Prokaryotes• Smallest and simplest cells• Single celled organisms (bacteria, amoebas)• Lacks a nucleus, has circular DNA• No organelles• Has a protective cell wall surrounding its cell

membrane. Gives the cell structure, stability, and shape.

• Most have flagella- long threadlike structures that protrude from the cell’s surface for movement.

Second Type of Cell

Eukaryotic Cells• cells that have a nucleus

- Nucleus -internal compartment that holds the cell’s DNA - Control center for the cell

• Has specialized structures called organelles.- Organelles- well defined structures that

carry out specific functions within the cell. - located inside the cell membrane

and outside the nucleus• Cilia- some single celled Eukaryotes contain them

to move around- short hair like flagella.