THE CELL

Definition of Cell

A cell is the smallest unit that is capable of performing life functions.

Cell Theory

1. All organisms are composed of cells

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

3. All cells come from preexisting cells

Two types of cells Prokaryotic

Pro / karyote

Before / nucleus (Greek)

Prokaryotes: more primitive cells that lack a true nucleus. Eukaryotic

Eu / karyote

True / nucleus

Eukaryotes: cells that have a true membrane bound nucleus that contains the DNA

Prokaryotic cells

Two domains in living world: Archaea and Bacteria

These are prokaryote E. coli bacteria on the head of a steel pin.

Bacteria

For the first half of geological time our ancestors were bacteria. Most creatures still are bacteria, and each one of our trillions of cells is a colony of bacteria.

Richard Dawkins

Archaea

•Not discovered until late 1970s

•Once thought to inhabit only extreme environments: hot springs, deep sea trenches, under the earth, salt flats (extremophiles) but now known to live everywhere

•Leading scientists to rethink how life arose in early days of Earth

Prokaryotic Cell•Cell wall – protects cell and gives it shape

•Plasma membrane – regulates movement of materials in and out of cell

•Cytoplasm – gel-like liquid that contains parts that do work of the cell

•Ribosomes – build proteins

•DNA – hereditary material sits loose in the cell, is not in nucleus

Very small: .1-10 microns

Prokaryotes play a huge role in our lives Yes, harmful diseases

TB

Rod shaped cells (bacilli)

Strep throat

Circular shaped cells (cocci)

Lyme disease

Spiral shaped cells (spirochete)

But life wouldn’t exist as we know it without them Cyanobacteria: their ability to

photosynthesize created the oxygen-rich atmosphere that exists today

•Digestion – E coli in our intestines helps us break down food to get the nutrients we need

• Decomposers: recycle nutrients

Example: nitrogen-fixing bacteria: help plants that we eat obtain enough nitrogen to grow

Biotechnology: solutions for major problems Example: environmental clean-up

Example: Faster growing, disease resistant, more nutritious food

Example: Cure diseases

Eukaryotes

Includes 4 kingdoms:

Protists Fungi

PlantsAnimals

(including us)

Eukaryotes vs. ProkaryotesBig differences: Have a membrane-bound nucleus that

encloses the DNA* DNA is organized as chromosomes Have other membrane-bound organelles to

carry out cell life processes Much larger (10-100 microns) Specialize to form multicellular organisms

Advantages of each kind of cell architecture

Prokaryotes Eukaryotes

simple and easy to grow

can specialize

fast reproduction multicellularity

can live in many different environments

can build large bodies

Vocabulary Be able to define/explain theseCell Theory

Prokaryote

Eukaryote

Bacteria

Archaea

Unicellular

Multicellular

Nucleus

Cytoplasm

Ribosomes

Membrane