The Cell Types of cells Eukaryotic Prokaryotic All other forms of life Cellulae (Small room) The Organism’s Basic Unit of Structure and Function Types of cells Eukaryotic Prokaryotic All other forms of life Micro-organisms

Cell Theory 1- All organisms are composed of one or more of cells. 2- Cell is the basic unit of life. 3- The new cell arises only from pre- existing cell.

1). Prokaryotic and eukaryotic cells differ in size and complexity Similarities All cells are surrounded by a plasma membrane. The semi-fluid substance within the cell is called “cytosol”, containing the cell organelles. All cells contain chromosomes which have genes in the form of DNA. All cells have tiny organelles called “Ribosomes” that make proteins.

1). Prokaryotic and eukaryotic cells differ in size and complexity Differences A major difference between prokaryotic and eukaryotic cells is the location of chromosomes. In an eukaryotic cell, chromosomes are contained in a true nucleus ). In a prokaryotic cell, the DNA is concentrated in the nucleoid) without a membrane separating it from the rest of the cell. In prokaryotic cell, DNA is a single strand or double strand DNA. But in eukaryotic cell, DNA is double strand.

Prokaryotic and eukaryotic cells differ in size and complexity All cells are surrounded by a plasma membrane. The semifluid substance within the membrane is the cytosol, containing the organelles. All cells contain chromosomes which have genes in the form of DNA. All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes.

A major difference between prokaryotic and eukaryotic cells is the location of chromosomes. In an eukaryotic cell, chromosomes are contained in a membrane-enclosed organelle, the nucleus. In a prokaryotic cell, the DNA is concentrated in the nucleoid without a membrane separating it from the rest of the cell.

(A)- Prokaryotes Micro-organisms

Prokaryotes Bacteria Archaea Types of Prokaryotes - Exist in extreme environments (hot and salty) - Exist in most environments They are differing in some other structural, biochemical and physiological characteristics

Fig. 7.4 The prokaryotic cell is much simpler in structure, lacking a nucleus and the other membrane-enclosed organelles of the eukaryotic cell.

In eukaryote cells, the chromosomes are contained within a membranous nuclear envelope. The region between the nucleus and the plasma membrane is the cytoplasm. All the material within the plasma membrane of a prokaryotic cell is cytoplasm. Within the cytoplasm of a eukaryotic cell is a variety of membrane-bounded organelles of specialized form and function. These membrane-bounded organelles are absent in prokaryotes.

Eukaryotic cells are generally much bigger than prokaryotic cells.

B- Eukaryotic Cell

Internal membranes compartmentalize the functions of a eukaryotic cell An eukaryotic cell has internal membranes, which partition the cell into compartments . These membranes also participate in metabolism as many enzymes are built into membranes. The general structure of a biological membrane is a double layer of phospholipids and diverse proteins. Each type of membrane has a unique combination of lipids and proteins for its specific functions. For example, those in the membranes of mitochondria function in cellular respiration.

B- Eukaryotic Cell Plant Cell Animal Cell Eu: True Karyon: Nucleus Plant Cell Animal Cell What are the functions of cell organelles ? Compare between Animal and Plant cell?

Euokaryotes: Euo = true karyot = nucleus Euokaryotes: Euo = true karyot = nucleus . Plant and animals have real nucleus, surrounded with nuclear membrane. -The Bacteria and the virus’s have no real nucleus they contain nucleiod region (no nuclear membrane) were the very simple genetic material (DNA or chromosome) -The prokaryotic cells (bacteria and viruses) also have a very simples cell structure cell wall, cell membrane, cytoplasm, ribosome’s and nucleiod area for a very simple genetic material (DNA or RNA) and cilia or flagella. The euokayotic cells have a very complex structure and many cell organelles (Look at the book page 112. 6th ed.)

Prokaryotes “Prokaryote” means “before a nucleus” No internal membrane-bound organelles – just one little bag of cytoplasm No nucleus Usually single-celled (may form simple colonies) May or may not require oxygen for survival. Earliest types of cells on Earth Cell type of all bacteria and Archaea

Much tougher than eukaryotes Can survive almost anywhere – and do! Have much greater genetic diversity than eukaryotes Have a cell wall surrounding the cell membrane (different chemistry from plant cell wall)