CELLS All images courtesy of www.cellsalive.com

The Cell Theory The Cell Theory arose after hundreds of years of observation, and many scientists. A few key scientists involved in the cell theory are Hooke, Schleiden, Schwann and Virchow. Robert Hooke- The first scientist to describe what he saw as “cells” when viewing samples of cork under the microscope in 1665.

The Cell Theory Nearly 200 years later, Matthias Schleiden viewed living plant specimens under the microscope and discovered they were made up of cells. Around the same time as Schleiden, Theodor Schwann viewed nonliving animal parts under a microscope and realized that they, too were made up of cells.

The Cell Theory Finally, Rudolf Virchow witnessed cell division under the microscope and learned that all cells arise from preexisting cells. The findings of these scientists, among others, lead to the cell theory, which states: All living things are made of cells. Cells are the basic unit of structure and function of life. Cells come from preexisting cells.

TYPES OF CELLS 1. Eukaryotic cells 2. Prokaryotic cells Defined by having a nucleus. Defined by having complex organelles. Plant and animal cells. 2. Prokaryotic cells Defined by NOT having a nucleus Bacteria cells.

Common Cell Features Both prokaryotic and eukaryotic cells contain: DNA A cell membrane (protects cell and allows things in and out of the cell). Ribosomes (protein making factories). Cytoplasm (water-based substance inside the cell). These are typically the only similarities between the two different types of cells.

There are approximately a dozen different organelles! Plant cell Eukaryotic Cells Eukaryotic cells contain organelles, a word that literally means “little organ”. Organelles have specific functions that they employ throughout the cell. There are approximately a dozen different organelles! Animal Cell

1. Nucleus What is it? a large, central membrane-bound organelle which contains D.N.A. Where is it found? All eukaryotic cells! (BOTH plant and animal cells have a nucleus). What does it do? Protects the DNA!

2. Nuclear envelope What is it? A porous membrane that encases the nucleus. These “nuclear pores” allow certain substances to pass into and out of the nucleus. Where is it found? In all eukaryotic cells; BOTH plant and animal. What does it do? The nuclear envelope protects the nucleus.

3. Nucleolus What is it? A structure contained within the nucleus. Where is it found? Inside the nucleus of eukaryotic cells. What does it do? It is responsible for making ribosomes.

4. Endoplasmic Reticulum What is it? A tunnel-like network of membranes. Where is it found? Connected to the nucleus and branching out into the cytoplasm of all eukaryotic cells.

Endoplasmic Reticulum con’t What does it do? Transfers substances within the cell, as well as many different chemical reactions including protein modification and distribution. ER is like the highway system of the cell! Smooth E.R. (free of ribosomes) TW O TYPES Rough E.R. (contains ribosomes)

5. Golgi body (sometimes called the “Golgi apparatus”) What is it? A membrane-bound organelle, which processes and packages proteins. Where is it found? The cytoplasm of all eukaryotic cells.

Golgi Body con’t What does it do? Acts like a post office by packaging proteins in vesicles and delivering them to other parts of the cell. Vesicles containing proteins exit the Golgi body and are sent to parts of the cell that need them.

6. Lysosomes What are they? Vesicles that contain powerful digestive enzymes. Where are they found? In all eukaryotic cells. What do they do? Break down old cell parts and fight off invading bacteria. *Peroxisomes are identical to lysosomes, except they contain hydrogen peroxide.

7. Mitochondria What is it? A unique, double membrane-bound organelle, which contains its own DNA. Where is it found? All eukaryotic cells. www.cellsalive.com

Mitochondria con’t. What does it do? Generates A.T.P. (cellular energy) *Think “Power House” Mitochondria have two membranes; an inner and an outer. Unique because these organelles have their own DNA (known as Eve’s DNA).

8. Vacuoles (vak-u-oles) Vacuoles differ among plant and animal cells. PLANT CELLS ANIMAL CELLS There is ONE, LARGE central vacuole. The central vacuole of plants stores water and nutrients, and also aids in cellular digestion. There are multiple, small vacuoles. The vacuoles of animal cells do not store water or nutrients, but rather waste as they aid in cellular digestion. www.cellsalive.com

9. Vesicles What are they? Small membrane bound sacs. Where are they found? Eukaryotic Cells What do they do? Transport various items around the cell.

10. The Cytoskeleton of Eukaryotic Cells Cytoskeleton: A network of protein fibers which help the organelles and cell move, and assist in cell division. The cytoskeleton maintains cell shape, as the name implies.

Cytoskeleton continued The main components of the cytoskeleton: -microtubules -actin filaments (or microfilaments) -intermediate fibers

11. Microtubules Help move proteins and vesicles throughout the cell. What are they? Small tubular structures made up of protein filaments; part of the cytoskeleton. Where are they found? All eukaryotic cells. What do they do? Help move proteins and vesicles throughout the cell. www.cellsalive.com

12. Centrioles What are they? Nine triplets of microtubules. Where are they found? IN ANIMAL CELLS ONLY! What do they do? Assist during nuclear division.

13. Chloroplasts What are they? Membrane-bound organelles that contain light-absorbing pigments. Where are they found? PLANT cells only! What do they do? Harvest energy from the sun for photosynthesis.

14. Cell Wall Where is it found? What is it? A structure consisting of cellulose that surrounds the cell membrane. Where is it found? Within eukaryotes the cell wall is ONLY found in plant cells, however all prokary- otes also have a cell wall. What does it do? Protects the cell and maintains homeostasis.

15. Cell Membrane AKA: Plasma Membrane Controls what enters or leaves the cell Made of a phospholipid bilayer and proteins Surrounds outside of ALL cells Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

16. Cytoplasm Jelly-like or watery substance that holds the organelles Enclosed by the cell membrane