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The Cell – Notes #15
Cell Theory (notes)
1. Cells are the basic unit of life.
2. All living things are made of cells.
3. All cells come from other cells.
Cell History (not notes)
• Cells were first discovered by Robert Hooke
in 1665
• The term “cell” is from how the first cells
looked under a microscope
• Hooke was looking at cork
• Under the microscope it looked like a lot of
little rooms
• So he called them “cells”, like in a monastery or
prison
He’s staring into your soul…or at least your cells
Cork under 100x magnification
#1 Cells are the basic unit of life (notes)
• Cells are defined as the smallest unit of life which can perform all of
the necessary functions.
• A general list of life functions:
•
•
•
•
•
Obtain and use energy
Grow and develop
Reproduce
Respond to environment
Adapt to environment
HeLa cells
Organelles (not notes)
• In order to perform these functions, cells
have parts called “organelles”
• Basically you can think of them like the
cell’s organs
• And just like your organs, they have
functions that keep it running
Organs vs. organelles (not notes)
Organelles are made of “proteins” (not notes)
• Proteins are large molecules which make up the organelles of cells
• They are also the machines that do the work in the cell
Protein
Organelle
Cell
Organ
#2 All living things are made of cells (notes)
• Cells are the building blocks that life is made out of
• Microorganisms are only a single cell, while larger organisms such as
trees and humans are made up of many cells
Amoeba
Bacteria
Cells in Humans (not notes)
• As a rough estimate an adult human is made of about 37.2 trillion
(37,200,000,000,000) cells. Each person is different.
• However, there are only about 200 types of cells.
Muscle Cells
Nerve Cells
#3 Cells come from cells (notes)
• Cells create new cells by
dividing in half
• A “mother” cell splits into
two “daughter” cells
Where did the first cells
come from? That is a topic
for another day!
Growth (not notes)
• Things grow by making more cells
• Bigger organisms DO NOT have bigger cells; they just have more cells
Viruses (notes)
• Viruses are NOT made of cells
• Viruses cannot make more of themselves without taking over a cell
Viruses continued (not notes)
• Viruses exist only to make more copies of themselves
• There is no other “why”: they
do what they do because it
is possible
• Viruses are the ultimate
parasites
Are viruses alive? (not notes)
• Viruses are in the grey area between being alive and not alive. They
are both similar and different to living things.
Similarities
Differences
• Made of the same atoms as life
• Cannot process energy
• Seem to act with a “purpose”
• Cannot move on their own
• Are capable of evolving
• Cannot reproduce on their own
In summary (not notes)
• Cells are the smallest thing we
consider “alive”
• All living things are made of one
or more cells
• Cells are made of organelles which
are made of proteins (large
molecules)
• Viruses are not cells
Protein