The most basic level of hierarchy is the chemical level as the body contains different elements. The four main ones are oxygen, carbon, nitrogen and hydrogen which make up 96.2% of body weight/ The remaining 3.5% are elements like phosphate, chlorine, calcium etc. The remainder 0.1% are trace elements. This is followed up by the cellular level which makes up tissues. Tissues are an aggregation of cells that have similar structures and functions. These tissues subsequently make up organs which form an organ system.

• 1665- Hooke
• 1673- Luuwenhock
• 1838- Schleiden
• 1839- Schwann
• 1858- Rudolf

a) All organisms are made up of cells

(b) All cells are produced from preexisting cells

(c) Cell is the basic unit of life

a) The cell contains DNA passed from cell to cell during cell division

b) Cells are basically the same chemical composition and metabolic activity

c) All basic chemical and physiological functions are carried out within the cell

d) Cell activity depends on activities of its subcellular structures

Microscopes are generally divided into light microscropes and electron microscopes. The light microscope is used to view stained living organisms through the use of visible light. It can magnify up to 1000 X and resolve up to 0.2µm.

Electron microscopes  are of two types; scanning and transmission. The SEM uses electron beams to study the surface of liviing organisms. The TEM, however, transmits electron beams to study the inside of a cell. Therefore, it only works on dead organisms. The magnification of electron microscopes is up to 100,000X while the resolution is up to 2nm

It is a physiological process that regulates flactuations from the outside environment to maintain an internal stable environment. Regulation processes encompass blood volume, pH and temperature.

As a cell increases in size, its surface area to volume ratio decreases. This can effectively jeopradize the effeciency of diffusion in the cell and rates of chemical exchange. The cell must therefore remain small to maintain effeciency.

Cells manage to remain small as their microscopic size give it sufficient surface area for nutrient transport and waste removal. Bigger cells also require more proteins and have a higher metabolism; there DNA assures the cells remain small.

Cells remain small by either

(1) Formation of projections such as microvilli

(2) Flattening into discs such as red blood cells

(3) Cell death or division

A multicellular organisms starts as a single cell that reproduces my mitosis. The differences in cell sizes are accompanied by different signaling and different gene expressions. Hence, the new cells differentiate.

Which cells have a tendency to differentiate to different specific types of cells?

Embryonic Stem Cells

A) Prokaryotes: are simple cells that have no true nucleus and lack membrane bound organelles. Its DNA is circular.

B) Ekaryotes: are complex cells that are larger in size and contain encapsulated genetic material along with membrane bound organelles. Linear DNA associated with histones.

C) Compartmentalization: the separation of incompatible chemical and physical conditions within a cell.

- Structural support and protection

- Rigidity and strength

- Determines shape and size

- Prevents over expansion when water enters the cells

- Allows sustainable growth 

- Regulates movement in and out of the cell (cell communication)

- Acts as a filtration mechanism

a) Cellulose - 35% - 50%

b) Xylan - 20% - 35%

c) Lignin - 10% - 25%

1) They have specialized functions and can perform specialized functions.

2) Membrane bound organelles act as container that partition the cell into different compartments and thus allows the creation of different local environments with separate pH and such. An example is lysosomes; if they were not compartmentalized, it would kill the cell

3) Membranes can act as sites for chemical reactions as they are made of a unique combination of lipids and proteins. They also contain embedded enzymes and reaction centers.

1) protein synthesis

2) energy production

3) cell division

The nucleus; ribosomes; ER; golgi apparatus and vesicles

Is surrounded by a perforated two lipid bilayer called the nuclear envelope. The nuclear pores act as a connection of the interior of the nucleus with the rest of the cytoplasm.

The pore complex consists of eight large protein granules that surround each pore. RNA and proteins must pass through these in order to enter or leave the nucleus.