1. Cells
The cell is the basic structural and functional unit of all known living organisms. It is
the smallest unit of life that is classified as a living thing. Some organisms, such as most
bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are
multi-celled
Robert Hocke discovered the cell when he was watching the cork in the microscopy.
There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually
independent, while eukaryotic cells are often found in complex organisms. In all cells
we can differentiate three parts: the cell membrane, the cytoplasm and the genetic
material.
Prokaryotic cells
The prokaryotic cell is simpler, and therefore smaller, than a eukaryote cell. The genetic
material is dispersed in the cytoplasm. Bacteria are typical prokaryotic cells.
A prokaryotic cell has:
•On the outside, flagella and pili project from the cell's surface. These are structures
that (not present in all prokaryotes) facilitate movement and communication
between cells.
•Inside the cell is the cytoplasm that contains the cell genome (DNA), ribosome and
other structures.
•The cell wall is another typical structure of prokaryotic cell.

2. Eukaryotic cells
This is a type of cell which makes up more complex organisms, that is, protozoa, plants,
animals, algae and fungi.
Diagram of a typical animal (eukaryotic) cell, showing subcellular components.
Organelles:
(1) nucleolus
(2) nucleus
(3) ribosome
(4) vesicle
(5) rough endoplasmic reticulum (RER)
(6) Golgi apparatus
(7) Cytoskeleton
(8) smooth endoplasmic reticulum
(9) mitochondria
(10) vacuole
(11) cytoplasm
(12) lysosome
(13) centrioles
The principal difference between prokaryotes and eukaryotes is that eukaryotic cells
contain membrane-bound compartments in which specific metabolic activities take
place. Most important among these is the presence of a cell nucleus, a membrane-
delineated compartment where the genetic material is found.
Plant cells have a cell wall and chloroplasts where photosynthesis happens.
Animal cells have different forms and they don´t have chloroplasts or cell walls
©Wikipedia and natural science (Pearson Longman)

3. 1-Answer the following questions:
What are organisms that are made of several cells?
What are the main parts of the cell?
What is the difference between a eukaryotic and a prokaryotic cell?
What is the difference between an animal cell and a plant cell?
2-Draw an animal cell and write the principal structures.
3-Look for information on the INTERNET about: mitochondrion, chloroplast and
cell wall. In http://www.ibiblio.org/virtualcell/tour/cell/cell.htm you have a
pronunciation guide.
©Maribel Gordillo Rivera2010 &Maggie Nowicki