Chapter 2 – Part 2Cell TheoryCell Types

The Cell Theory

1. All living things are made of one or more cells

2. Cells are the basic units of structure and function in all organisms

3. All cells arise from preexisting cells

Cell SizeThere are many types of cells in

our body, each with a different shape and function

Some cells, like human egg cells, can be seen with the naked eye

Other cells are very small, like sperm cells, and need a microscope to be seen

Cell Size

Cell SizeHumans have trillions of cells in

the body

Size of cells range from 5µm to 20µm in size

http://learn.genetics.utah.edu/content/begin/cells/scale/

Cell Size Continued…Small cells function more efficiently

than large cellsIf surface area to volume ratio is

too low, substances cannot enter and leave the cell well enough to meet the cell’s needs

Small cells have high surface area to volume ratio

Surface Area-to-Volume

Types of Cells

Prokaryote – “Before nuclei”

Eukaryote – “True nuclei”

ProkaryotesConsists of unicellular organisms

Ex: Bacteria and archea

Can live in many environmentsEx: extreme temperatures, pH,

and radiation

Prokaryotes

Some can make their own food

Grow and divide rapidly using asexual reproduction

Prokaryote Cells-Lacks a nucleus and most organelles-Much smaller than a eukaryote cell-One single circular strand of DNA found in the cytoplasm

Prokaryote Cells Continued…Plasmid: Circular strand of DNA

Flagella: Aids in movement

Pili: Helps bacteria attach to surfaces

Capsule: a polysaccharide barrier used for protection

EukaryotesConsists of unicellular and

multicellular organismsEx: Plants, animals, fungi,

protists…Organisms can asexually and

sexually reproduce

Eukaryote CellsContains a nucleus with DNA and

membrane-bound organelles

Larger, more complex cells

May have evolved from a prokaryotic cell

Types of Eukaryote CellsPlant Cells and Animal Cells