The Cell

“Everything you'll ever need to know is within you; the secrets of the universe are imprinted

on the cells of your body.” Dan Millman

History of the Cell

• Robert Hooke- in mid 1600s, he used the newly invented microscope to examine a thin slice of cork. He was impressed by the microscopic compartments in the cork and they reminded him of rooms in a monastery, which are known as cells. He therefore referred to these units as cells.

• Anton Van Leeuwenhoek- Dutch merchant who made further observations of the cells of plants, animals and microorganisms.

History of Cell Continued

• Matthias Schleiden- in 1838, this German Botanist proposed that all plants are composed of cells.

• Theodore Schwann- a year later, this anatomist concluded that all animals are composed of cells.

• Rudolf Virchow- In 1858, he proposed all living things are made of cells

Cell theory

• The theory states that all organisms are composed of similar units of organization, called cells.

Aspects of the Cell Theory

•  1. all known living things are made up of cells. •   2. the cell is structural & functional unit of all living

things.•   3. all cells come from pre-existing cells by division.

(Spontaneous Generation does not occur). •   4. cells contains hereditary information which is

passed from cell to cell during cell division. •   5. All cells are basically the same in chemical

composition. •   6. all energy flow (metabolism & biochemistry) of life

occurs within cells.     *

• A Eukaryote cell is much more complex, as suggested by this generalized diagram showing its makeup

Prokaryotic vs. Eukaryotic

• Simpler than eukaryotes

• Lack a Nucleus• Lack internal

structural bodies (organelles)

• Bacteria and cyanobacteria

• More complex• Have a nucleus• Have internal

structural bodies• Protozoa, fungi,

plants, and animals.

Structure of the Cell

• Cytoplasm- gel like substance in which the cell is composed

• Plasma membrane- outermost surface of the cell which separates the cell from the external environment.

The Nucleus

• The nucleus has the following functions: to store genes, to produce messages that code for proteins, to produce ribosomes in the nucleolus, and to organize genes into chromosomes to use for cell division. The nucleolus produces ribsomes that are then sent out onto the rough endoplasmic reticulum where they are used in protein synthesizing. (information storing area of the cell).

Cytoplasm and Organelles

• Cytoplasm- essentially, it is the gel like material enclosed by the plasma membrane. Within the cytoplasm are a number of microscopic bodies called organelles. Various functions go on within these organelles.

Organelles: Endoplasmic reticulum or ER

• Site of Protein production (synthesis) of the cell. – Rough ER- studded

with submicroscopic bodies called ribosomes

– Smooth ER- no ribosomes

Ribosomes

• Ribosomes have the responsibility of assembling the proteins within a cell structure. They are found in two places, attached to the endoplasmic reticulum or in the cytosol.

Golgi Apparatus (Golgi Body)• sometimes considered the shipping

department for the cell's chemical products. It modifies proteins and lipids that have been created in the endoplasmic reticulum and prepares them for export outside of the cell or for transport to other locations in the cell. Proteins and lipids built in the smooth and rough endoplasmic reticulum leave in tiny vesicles that move through the cytoplasm until they reach the Golgi apparatus. The vesicles combine with the Golgi membranes and distribute their internally stored molecules into the organelle. The compounds are further processed by the Golgi apparatus. The final product is taken from the Golgi Apparatus in a vesicle and directed to its final destination inside or outside the cell. (Where proteins are modified and then shipped to specific location)

Lysosomes•

Lysosomes are membranes full of enzymes. They are made by the endoplasmic reticulum and Golgi apparatus. Lysosomes are believed to be formed by budding from the Golgi complex. They are involved in recycling the organic material in the cell and in the digestion of macromolecules. Lysosomes are also involved in cell death.

• Break down particles of food taken into the cell and make them available for use

• Also known as “Suicide Sacs”

Mitochondria

• Mitochondria are rice-shaped structures that play a big role in breaking down sugar to release energy for the cell to use. A mitochondria also contains small amounts of DNA that are used to direct the manufacture of proteins. Mutations in the mitochondria's protein  coding are the result of human diseases.

• Energy released is used to form ATP.

• “Powerhouse of the Cell”

Cell Wall

• Provide support and help cell resist mechanical pressure

• Not as selective as plasma membrane

• Many prokaryotes and eukaryotes contain this structure

• Almost all bacteria have cell wall

• Among eukaryotes, the fungi and plants have cell walls.

Cytoskeleton

• An interconnected system of fibers, threads, and interwoven molecules that give structure to the cell.

• Main components of cytoskeleton are the microtubules, microfilaments, and intermediate filaments.

• Another organelle called the centriole is a cylinderlike structure that occurs in pairs. It functions in cell division

The Cell All Together