Cellular Basis of Life

The cell was discovered by Robert Hooke in 1665. He examined (under a coarse, compound

microscope) very thin slices of cork and saw a multitude of tiny pores that he remarked looked like

the walled compartments a monk would live in. Because of this association, Hooke called them

cells, the name they still bear. However, Hooke did not know their real structure or function. [1]Hooke's description of these cells (which were actually non-living cell walls) was published in Micrographic.[2]

 His cell observations gave no indication of the nucleus and other organelles found in most living

cells.

Credit for developing cell theory is usually given to three scientists: Theodor Schwann, Matthias Schleiden, and Rudolf Virchow. In 1839, Schwann and Schleiden suggested that cells were the basic unit of life. Their theory accepted the first two tenets of modern cell theory (see next section, below). However, the cell theory of Schleiden differed from modern cell theory in that it proposed a method of spontaneous crystallization that he called "free cell formation

In 1855, Rudolf Virchow concluded that all cells come from pre-existing cells, thus completing the classical cell theory. (Note that the idea that all cells come from pre-existing cells had in fact already been proposed by Robert Remak; it has been suggested that Virchow plagiarised Remake.)[9

The observations of Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow, and others led to the development of the cell theory. The cell theory is a widely accepted explanation of the relationship between cells and living things. The cell theory states:

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, and is often called the building block of life.

Organisms can be classified as unicellular ( single cell; including most bacteria) or multicellular (including plants and animals).

Humans contain about 10 trillion cells.

What does the Cellular Basis of Life Mean?

The Cell Theory states: All living organisms are composed of cells.

They may be unicellular or multicellular. The cell is the basic unit of life. Cells arise from pre-existing cells.

Cell Theory

The modern version of the Cell Theory includes the ideas that:

Energy flow occurs within cells. Heredity information (DNA) is passed on

from cell to cell. All cells have the same basic chemical

composition.

Cell Theory

Prokaryotic vs. Eukaryotic Cells

DNA Plasma membrane Cytoplasm Ribosomes

Common Features of Prokaryotic and Eukaryotic Cells

Prokaryotic cells are fundamentally different in their internal organization from eukaryotic cells. Notably, prokaryotic cells lack a nucleus and membranous organelles.

Features of Prokaryotic Cells

Eukaryotic cells contain a membrane-bound nucleus and numerous membrane-enclosed organelles (e.g., mitochondria, lysosomes, Golgi apparatus) not found in prokaryotes.

Features of Eukaryotic Cells

Nucleus Large Oval body near the centre of the cell. The control centre for all activity. Surrounded by a nuclear membrane.

Cell Structures and their Functions

The outer boundary of the cell. It separates the cell from other cells. It is porous which allows molecules to pass

through.

Cell Membrane

Non living structure that surrounds the plant cell.

Protects and supports the cell. Made up of a tough fibre called cellulose.

Cell Wall ( Plant Cells Only )

Cell material outside the nucleus but within the cell membrane.

Clear thick fluid. Contains structures called organelles.

Cytoplasm

Are clear fluid sacs that act as storage areas for food, minerals, and waste.

In plant cell the vacuoles are large and mostly filled with water. This gives the plant support.

In animal cells the vacuoles are much smaller.

Vacuoles

Power house of the cell. Centre of respiration of the cell. They release energy for cell functions.

Mitochondria

Contains a green pigment known as chlorophyll which is important for photosynthesis.

Chloroplasts ( Plant cells only )

Tiny spherical bodies that help make proteins.

Found in the cyto plasm or attached to the endo plasmic reticulum.

Ribosomes

Systems of membranes throughout the cyto plasm.

It connects the nuclear membrane to the cell membrane.

Passageway for material moving though the cell.

Endoplasmic Reticulum ( ER )

Tube like structures that have tiny sacs at their ends.

They help package protein.

Golgi Bodies

Also called the" suicide sacs " Small structures that contain enzymes

which are used in digestion. If a lysosome were to burst it could destroy

the cell.

Lysosomes

Nutrition - The process by which materials from the environment are taken into an organism and changed into usable forms.

Transport - All the processes by which substances pass into or out of cells and circulate within the organism.

Respiration - The process by which orangisms obtain the energy they need by releasing chemical energy stored in nutrients.

Cellular Processes

Synthesis - A process in which simple substances are conbined chemically to form more complex substances.

Assimilation - The incorporation of materials into the body of an oragnism.

Growth - The process by which living organisms increase regulates the opening and closing of the stomates.

Excretion - The process by which the wastes of cellular metabolism are removed from an organism.

Cellular Processes

Regulation - The processes by which an organism maintains a stable internal environment in a constantly changing external environment.

Reproduction - The process by which living things produce new organisms of their own kind.

Metabolism - All the chemical reactions of the life processes of an organism.

Cellular Processes

http://suite101.com/article/prokaryotic-and-eukaryotic-cells-a32332

http://www.cod.edu/people/faculty/fancher/prokeuk.htm

http://animals.about.com/od/animalswildlife101/a/diffprokareukar.htm

http://jgimp.tripod.com/cells.html http://fig.cox.miami.edu/~cmallery/150/

unity/cell.text.htm

References