The Cell TheoryCells Unit

September 28, 2015

https://www.youtube.com/watch?v=wJyUtbn0O5Y

Some Random Cell Facts

The average human being is composed of around 100 trillion individual cells!

On an average day, 50-70 billion cells die in the human body.

The biggest cell in the world is the ostrich egg, which can be seen with your naked eye!

WOW!!!

Anton van Leuwenhoek

In 1673 Leuwenhoek, a Dutch biologist, used a handmade microscope.

He used the microscope to observe pond scum and discovered single-celled organisms.› He called them “animalcules.”

Discovery of Cells

In 1665 an English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork.

Observations› Saw that the cork was composed

of thousands of tiny chambers. › He called these chambers “cells.”

Significance: opened up the study of cells.

150-200 Year Gap??? Very little cell advancements were made after

Hooke and Leuwenhook. This is probably due to belief in spontaneous

generation.› Definition: ordinary formation of living organisms

without descent from similar organisms.› Mice appearing from dirty clothes/corn husks.› Maggots appearing from rotting meat.

19th Century Advancement

Much doubt existed around spontaneous generation.

Conclusively disproved by Louis Pasteur.

Ummm, I don’t think so!!!

Development of Cell Theory

1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells.

1839- German physiologist, Theodor Schwann, stated that all animal tissues are composed of cells.

Development of Cell Theory

1858- Rudolf Virchow, German physician,, concluded that cells must arise from preexisting cells.› No spontaneous generation!

The Cell Theory Complete

The 3 Basic Components of the Cell Theory were now complete:1. All organisms are composed of one or

more cells.2. The cell is the basic unit of life in all living

things.3. All cells are produced by the division of

preexisting cells.

http://ed.ted.com/lessons/the-wacky-history-of-cell-theory

Two Basic Cell Types:Prokaryotic vs. Eukaryotic Cells

Cells UnitSeptember 28,

2015

Two Basic Types

Remember….cells are the basic unit of life for ALL living things.

There are two basic types of cells:1. Prokaryotic cells – found in bacteria.2. Eukaryotic cells – found in protists, fungi,

plants and animals.

Characteristics Shared Same basic functions. Plasma membrane to control what

enters and leaves the cell. “Filled” with cytoplasm. Contain ribosomes to make protein. Contain DNA (genetic information).

What Makes Eukaryotic Cells Different?

Much more complex. Much larger. Contain a nucleus to house the genetic

material.› Linear DNA packaged into chromatin found inside

the nucleus. Contains organelles-specialized structures in the cytoplasm.

What Makes Prokaryotic Cells Different?

Much smaller. Less complex. No nucleus. Circular DNA that is

found in the cytoplasm.

No organelles found in the cytoplasm.

Surrounded by a cell wall.

What does size have to do with it?Why are prokaryotes smaller than eukaryotes?

Smaller surface area to volume allows nutrients to easily and quickly reach center of the cell.

Eukaryotic cells are larger and can not pass nutrients as quickly. Specialized organelles:› carry out metabolism.› provide energy.› transport chemicals throughout the cell.

How can we study cells?

Problem:They are microscopic!

Solution:Use a microscope!

Types of Microscopes

1. Compound Light Microscope

› Light passes through lenses to magnify image up to 1000X.

› Can observe living cells.

Types of Microscopes

2. Electron microscope

› Uses a beam of electrons to magnify image

> 1000X.› Kills cells being

observed.