Cell Structure

Cell Structure

A cell is the basic structural and functional unit of a living
organism.


Levels of Organization of Organisms
UNICELLULAR ORGANISMS
-> are made up of only one cell.
-> Examples: protists, bacteria, fungi, and some originally
aquatic plants (e.g., unicellular algae).


COLONIAL FORMS
-> groups of cells connected by cell walls or gelatinous coverings
-> represent an intermediate stage between unicellular and
multicellular organisms.
-> Examples: bacteria, protists, and some originally aquatic
plants.


MULTICELLULAR ORGANISMS ARE DIVIDED INTO:


THALLUS ORGANISMS
-> have a body that is poorly differentiated into tissues.
Examples: protists, fungi, and originally aquatic plants.

, Tissue Organisms
-> have a body clearly differentiated into tissues.
Examples: land plants and animals.


Cell Size




6:1 3:1

a:b a- surface area b- volume

The smaller the cell, the greater the surface area-to-volume
ratio. This makes the exchange of substances between the cell
and its environment more efficient.


Animal Cell
-> Nucleus – contains DNA, which is the genetic material
responsible for an organism's characteristics and their
inheritance.
-> Cell membrane – separates the inside of the cell from the
external environment.