An Introduction to Cells

Indicator B – 2.1: Recall the three major tenets of cell theory

Indicator B – 2.3:

Compare the structures and organelles of prokaryotic and eukaryotic cells.

Key Concepts

n  Cell Theory

n  Unicellular vs. Multicellular Organisms n  Prokaryotes vs. Eukaryotes

It is essential for you to know:

n  All living things are composed of one or more cells.

n  Cells are the basic unit of structure of all living things.

n  All presently existing cells arose from previously existing cells.

Objectives

n  Recall the major tenets of the Cell theory.

n  Compare unicellular organisms and multicellular organisms.

n  Differentiate between prokaryotic cells and eukaryotic cells.

Vocabulary Words

Please define the following words: 1.  cell theory 2.  cytoplasm 3.  organelle 4.  prokaryotic cell 5.  eukaryotic cell

The Cell

LIFE IS CELLULAR

Before we begin... ATP (adenosine triphosphate) = ENERGY!

Cells take sugar (glucose) from food and turn it into ATP.

The History of Cell Biology

The History of Cell Biology

A person who studies cells is called a cytologist. They work in the field of cytology.

The History of Cell Biology

Anton van Leeuwenhoek n  1600’s n  Became one of the first

people to use a microscope to study nature.

n  Was the first person to see tiny living organisms in a drop of water.

The History of Cell Biology Robert Hooke

n  1665 n  Saw “cells” in a cork under a light microscope.

The History of Cell Biology Matthias Schleiden

n  1838 n  Concluded that all

plants have cells.

The History of Cell Biology Theodor Schwann

n  1839 n  Concluded that all

animals have cells.

The History of Cell Biology

Rudolf Virchow n  1855 n  Studied cell

reproduction

The Cell Theory

n  A cell is the basic unit of life. n  All of the scientists’ work contributed to

what is now called the cell theory: 1)  All living things are composed of one or more

cells. 2)  Cells are the basic units of structure and function

in an organism. 3)  Cells come only from the reproduction of existing

cells.

Prokaryotes & Eukaryotes

Biologists divide cells into two main categories:

n  Prokaryotes n  Eukaryotes

Prokaryotes & Eukaryotes Prokaryotes

n  No nuclei n  Have cell membrane, cell

wall, plasmid, ribosomes, cytoplasm

n  Smaller and simpler n  Most bacteria and archae n  Divide by binary fission

Prokaryotes & Eukaryotes Eukaryotes

n  Have a nucleus n  Usually bigger and

more complex n  Cell membrane,

cytoplasm, & organelles.

n  Plants, animals, fungi, and many microorganisms.

Unicellular Organisms

n  Sometimes the cell is the organism. n  Do everything that you would expect a

living thing to do. n  Include both prokaryotes and eukaryotes.

n  Prokaryotes: bacteria and archae n  Eukaryotes: some types of algae, protists,

fungi.

Multicellular Organisms

n  Made up of more than one cell. n  Cells in multicellular organisms are

specialized to perform particular functions within the organism. n  This is called cell specialization. n  Think:

n  blood cells, hair cells, digestive cells, etc.

Levels of Organization

The levels of organization in a multicellular organism are:

n  individual cells n  tissues n  organs n  organ systems

Levels of Organization

Cell: nerve cell Tissue: nerve tissue Organ: the brain Organ System: Nervous System