Download Cell - Capital High School

Cell Theory
Prokaryote vs. Eukaryote
Organelles, and
Cell Size
What is a Cell?

Cell – Basic unit of living things.
Organisms are either:
 Unicellular – made of one cell such as
bacteria and amoebas.
OR
 Multicellular – made of many cells
such as plants and animals.
Scientists to Remember

Robert Hooke (1665) – Observed “cells” in cork
Cell Theory
Confirmed discoveries that all scientists believe to be true
about cells:
1. Cells are the basic unit of life.
2. All living things are made of cells.
3. New cells are produced from existing cells.
Two Types of Cells:
before
nucleus
true
nucleus
Prokaryotes
1.
2.
3.
4.
5.
6.
7.
NO nucleus
NO membrane bound organelles
(just ribosomes)
ALL are unicellular
Smaller than eukaryotic cells
Forerunner to eukaryotic cells (smaller and more simple)
DNA – single strand and circular
Ex: ALL Bacteria
Eukaryotes
1.
2.
3.
4.
5.
6.
Has a nucleus with a nuclear envelope
Bigger and more complex than prokaryotes
Have membrane bound Organelles
(golgi, ER, lysosomes…etc)
DNA – double-stranded and forms
chromosomes (highly organized)
Can be uni- OR multicellular organisms
Ex: animals, plants, fungi
1
2
Control Center:
Holds DNA
2
Controls what goes
in and out of cell;
Protects Cell
3
Jelly Like
Substance that
holds organelles
4
5
Site of Protein
Synthesis
Protein and lipid
synthesis; transport
of proteins
5
1
3
4
6
7
6
7
Cell Membrane 1. Regulates what enters and leaves the cell.
 Selectively permeable
Structure
2. Protects and supports the cell.
http://www.youtube.com/watch?v=LKN5sq5dtW4

Lipid bilayer
http://www.youtube.com/watch?v=LKN5sq5dt
W4
Cell Size
Surface area : Volume
Are whale cells the same size as sea stars cells?
Yes!
What limits the size of cells?
Surface Area to Volume Ratio - How much space is on the outside (cell
membrane) compared to the space on the inside of the cell.
As the surface area of something increases, it’s volume increases faster
Surface area = L x W x # of sides (cm2) the surface of an object. The
outside covering of a cell. (cell membrane)
Volume = L x W x H (cm3)
The space inside the cell
A small object has a high surface area to volume ratio
A large object has a small surface area to volume ratio
Large Cell
It takes more time for the nutrients
to reach the center of this cell
& DNA would not be able to keep up
with demands of the cell
Small Cell
It takes less time for the
nutrients to reach the
center of this cell
Conclusion
 As cell size increases, the surface area to volume
ratio Decreases (small surface area to volume
ratio), which can lead to death of a cell.
 Having a large surface area to volume ratio is
important to the functioning of cells since it gets
materials, nutrients, O2, & wastes into & out of it
faster.
 Cells divide before they get too big!