1. The Cell
The basic unit of life

2. The Cell Theory The cell is the basic unit of life.
All living things are composed of cells.
New cells come from existing cells.

3. Who? When? Antonie von Leeuwenhoek, from Holland has long been
given credit for inventing
the first microscope.
When?
He used a microscope in
1673!

4. Who? When? However, Robert Hooke, from Britain, is credited
with viewing with a
microscope much earlier.
When?
His work was recorded
in 1665.

5. What? Robert Hooke viewed the cells of cork wood,
while Antonie von Leeuwenhoek viewed
living microscopic organisms under the
microscope.

6. This is a sketch of the cork cells,
which Hooke drew in his notes.
These are actual cork cells
as viewed through a
microscope.

7. Leeuwenhoek viewed “bee mouth parts and stings” as well as fungus and human louse. He also viewed bacteria, such as the ones pictured below.

8. Early discoveries about cells:
1838 Schleiden announced that all plant tissue is composed
of cells.
1839 Schwann describes animal cells as being similar to
plant cells.
1840 Virchow determined that cells come only from existing cells.

9. There are many different kinds of cells:
Bacteria
Red Blood Cells
Single Celled Animals
Plant Cells
Skin Cells

10. Out of all these kinds of cells, there
are actually only two types of cells:
Prokaryotes and Eukaryotes

11. Characteristics of the two types of cells:
Prokaryotes Eukaryotes
Capsule
Single circular chromosome
No membrane bound nucleus
No organelles
Small (0.25mm-3mm)
Cell division by fission*
Plasma membrane
Linear molecule chromosomes Well defined nucleus
Membrane-bound organelles
Larger (4.6mm+)*
Cell division by mitosis*
Example: Everything else!
(plants, animals, protists, fungi)
Example: Bacteria

12. Prokaryote means:
Pro = before
Karyon = nucleus

13. Eukaryote means:
Eu = true
Karyon =
“Kernel” or nucleus

14. Prokaryote Cells:

15. Eukaryotic Cells:

16. There are two types of Eukaryotic Cells:
Animal Cells and Plant Cells

17. Cell Growth Does the adult bear have larger cells than the bear cub?
…Or does the adult bear have more cells than the baby bear?

18. On average, the adult animal’s cells are no larger than the
baby’s. The adult just has more cells than the baby.
The same thing is true for any living organism!
Including this huge
oak tree and this
tiny oak sapling!

19. Why do cells stay small?
As cells grow, the surface area to volume ratio decreases.
(This means that there will be less surface area per unit of
volume inside the cell. )

20. Why does this matter?
Because the surface of cells are covered with signaling
proteins, which communicate between the inside of the cell
and the outside of the cell. These proteins tell the
membrane what can come into the cell and what can go out
of the cell.

21. Animal Cells: Nucleolus Nucleus 8. Smooth Endoplasmic Reticulum
Ribosome
Vesicle
Rough Endoplasmic Reticulum
Golgi Body
Microtubule
8. Smooth Endoplasmic Reticulum
9. Mitochondria
10. Lysosome
11. Cytoplasm
12. Peroxisome
13. Centriole

22. Animal cells have cell membranes:
Fluid mosaic model of the
cell membrane
Lipid Bilayer

23. Inside the nucleus of an animal cell:

24. Electron micrograph
of the nucleus:
nucleolus

25. Organelles of the animal cell:
The “E.R.” – The smooth endoplasmic reticulum
functions in synthesis of lipids and phospholipids.
Proteins are synthesized by ribosomes which are on the
rough E.R.

26. Golgi Apparatus- or complex, functions in
storage, modification, and packaging of protein products,
especially secretory products. These vesicles may add
complex carbohydrates to protein molecules. These
vesicles bud off the “maturing face” of the complex.
(ex. lysosomes)

27. The Golgi works with the E.R.

28. Mitochondria – enzymes located on the cristae
carry out energy-yielding steps of aerobic metabolism.

30. Cytoskeleton – this is the structural part of
the cell. It provides support and a means of
locomotion of organelles within the cell.
The cytoskeleton is made up of several kinds of
tubules and filaments:
Microtubules – These are composed of a protein
called tubulin.
Microfilaments - These are made up of proteins
called actin and myosin
Intermediate filaments – There are five
Biochemically distinct types. They vary based on
what type of cell in which they are found.

32. The Centrisome – this is made up of two
centrioles at right angles to each other.
Microtubules radiating from here are called the aster. This is the microtubule organizing center.
centrisome
centriole

33. Cell surfaces and their specializations:
Cilia – motile extensions of the cell surface that
sweep materials past the surface of the cells.
(Usually short and numerous like many fine hairs.)
Flagella – also motile extensions. (Usually long and
single or only two or three.)
Both cilia and flagella are similar in internal
structure. They are composed of a long cylinder of
nine pairs of microtubules enclosing a central pair.
At the base of each cilium or flagella is a basal body,
Which is identical in structure to a centriole.

34. cilia

35. flagella

36. Microvilli – these are fingerlike projections which increase the surface area of the cell for absorption.

37. Methods of cell locomotion:
Cilia and flagella are able to propel single-
celled or small creatures.
Amoeboid movement – single-celled organisms use
extensions of the cytoplasm as “false feet,” or
Pseudopodia. The cytoplasm streams and the action
of the microfilaments contracting moves the cell.
pseudopodia

38. Cell membranes – function to communicate
between neighboring cells. They also serve as
a selectively permeable barrier. It functions in
cellular metabolism.

39. Ways materials can pass through the cell membrane:
Diffusion – movement of particles from an area of
high concentration to an area of lower concentration.
(Concentration gradient – when a difference exists
between the concentration inside and outside the cell.)
Osmosis – water molecules move through a selectively permeable barrier across a concentration gradient.
Mediated transport – special proteins called transporters or permeases move biologically important molecules into and out of the cell. (These are usually macromolecules.)

40. Two kinds of mediated transfer:
Facilitated diffusion – permease assists a molecule
permeate a membrane that it would not normally be
able to penetrate.
Active transport – energy is supplied to the transporter system to transport molecules in the direction opposite the concentration gradient.

41. Endocytosis – the ingestion of material by
cells.
(Ex. 1 Phagocytosis – “cell eating.” Common among protozoa. Ex. 2 Potocytosis – small areas of the surface membrane are invaginated to form tiny vesicles called caveolae. Ex 3 Pinocytosis = cell drinking.)
Exocytosis - membranes of vesicles within the
cell fuse with the plasma membrane in order to let
wastes exit the cell.

42. Plant Cells

43. Plant cells differ from animal cells:
cellulose
cell walls
Plant cells have cell walls made of cellulose.

44. Plant cells have pores for transport
between cells:

45. Plants have a large storage vacuole:

46. Plant cells have chloroplasts used for photosynthesis.
These convert light energy into chemical bond energy.
This is how plants manufacture their own food.

47. Chloroplasts visible in real plant cells:

48. Cells can be differentiated to perform different
functions within the same organism:
For example, in an eight week old fetus, there are:
heart cells
fat cells
muscle cells
bone cells
skin cells
bone marrow cells
All are cells, but they all do different things!

49. What is the largest cell on Earth?
Answer : An unfertilized Ostrich egg!

50. The End