2. Understanding Cells
English scientist Robert Hooke first identified
cells over 300 years ago while looking at cork
under a microscope he built.
3. Understanding Cells
Cork is actually made of water-resistant cells that
separate the outer bark from the delicate interior bark.
4. Understanding Cells
• Cork has a unique set of properties not
found in any other naturally existing
material. It is:
• impermeable to gas and liquid
• rot resistant
• fire resistant
• termite resistant
5. Understanding Cells
• In the cork Hooke saw small openings similar
to a bee’s honeycomb. The openings
reminded him of the small rooms, called
cells, where monks lived.
• Hooke named these small structures cells.
6. Cell Theory
• Scientists made better microscopes than
• They looked for cells in places such as pond
water and blood.
• The newer microscopes made it possible for
scientists to see different structures inside cells.
7. Cell Theory
• A scientist named Matthias Schleiden
looked at plant cells.
• Another scientist, Theodore
studied animal cells.
• Later, Rudolf Virchow said all cells come
from cells that already exist.
• The observations made by these scientists
became known as the cell theory.
8. Cell Theory
The Cell Theory states:
1. All living things are made of one or more
2. The cell is the smallest unit of life.
3. All new cells come from pre-existing cells.
9. Basic Cell Substances
• The cell theory raised more questions for
scientists. Scientists began to look into what
cells are made of.
• Cells are made of smaller parts called
macromolecules that form when many
small molecules join together.
• Macromolecules cannot function without
one of the most important substances in
cells - water.
10. Basic Cell Substances
• The main ingredient in every cell is water.
Making up more than 70 percent of a cell.
• Water also surrounds cells, helping to
insulate your body. This helps your body
maintain a stable internal environment, or
• Water also is useful because it can dissolve
other substances, such as salt.
• For substances to move into and out of a
cell, they must be dissolved in a liquid.
11. Macromolecules in Cells
• All cells contain other substances besides
water that help cells do what they do.
• There are four types of macromolecules in
cells. They are nucleic acids, proteins,
lipids, and carbohydrates.
• Each type of macromolecule has its own
function in a cell. These functions range
from growth and communication to
movement and storage.
12. Macromolecules in Cells
• Both deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA) are nucleic acids.
• Nucleic acids are important because they
contain the genetic material of a cell. This
information is passed from parents to
• Nucleic acids are macromolecules formed
when long chains of molecules called
nucleotides join together.
13. Macromolecules in Cells
14. Macromolecules in Cells
15. Macromolecules in Cells
16. Macromolecules in Cells
17. Macromolecules in Cells
18. Macromolecules in Cells
19. Macromolecules in Cells
• DNA includes instructions for cell growth, for
cell reproduction, and for cell processes
that enable a cell to respond to its
• DNA is used to make RNA. RNA is used to
• The order of nucleotides in DNA and RNA is
important. A change in the order of the
nucleotides can change the information in
20. Macromolecules in Cells
• The macromolecules necessary for almost
everything cells do are proteins.
• A protein is a macromolecule made of
long chains of amino acid molecules.
• RNA contains instructions for joining amino
acids together to build the protein.
21. Macromolecules in Cells
22. Macromolecules in Cells
23. Macromolecules in Cells
24. Macromolecules in Cells
• A protein can contain 100 to 10,000’s
• Cells have hundreds of proteins.
• Each protein has its own function. For
• help cells communicate with other cells
• move substances around inside cells
• help to break down nutrients in food
• make up supporting structures (like hair,
horns, and feathers)
25. Macromolecules in Cells
• A lipid is a large macromolecule that does
not dissolve in water. Because lipids do not
dissolve in water, they protect cells.
• Lipids also are a large part of the cell
• Lipids store energy for cells and help with
• Cholesterol and vitamin A are lipids.
26. Macromolecules in Cells
27. Macromolecules in Cells
• One sugar molecule, two sugar molecules,
or a long chain of sugar molecules make
• Carbohydrates store energy, provide
structural support for cells, and help cells
28. Macromolecules in Cells
• Sugars and starches are carbohydrates that
store energy. Fruits contain sugars. Bread
and pasta are mostly starch.
• The energy stored in sugars and starches
can be released quickly through chemical
reactions in cells.
• Cellulose is a carbohydrate in the cell walls
29. Macromolecules in Cells
30. Macromolecules in Cells
Starch chain of glucose
31. Macromolecules in Cells
many chains of glucose