Cytology is the study of cells. Anton van Leeuwenhoek first observed cells using microscopy in the 1600s. Robert Hooke coined the term "cell" after observing plant cells in 1665. The cell theory, developed in the mid-1800s, states that all living things are made of cells, cells are the basic unit of structure and function, and new cells are produced from existing cells. Cells come in two main types - prokaryotes which lack nuclei and organelles, and eukaryotes which have nuclei and organelles. All cells share common structures like the cell membrane, cytoplasm, and in eukaryotes, the nucleus, but they also contain specialized structures called organelles that perform

1. Cytology

2. Cytology
is the “study of cells”
• Cyto = cell, ology = study of

3. The Cell Theory and its
Development

4. Anton van Leeuwenhoek (1632-1723) was the first to
adapt lenses to the study of living organisms.
He discovered microorganisms.

5. 1665 – Robert Hooke
Observed chambers, dead plant
cells, in cork.
• Coined the term "cells” in 1665.
Cork Cells

6. 1833 - Robert Brown
• Studied the nucleus. Do all living cells
have a nucleus?
Nucleus
Human Cheek Cell

7. 1838 - M.J. Schleiden
• Botanist….
Discovered plants are
made of cells.
Elodea….Typical Plant Cell

8. 1839 - T. Schwann
• Zoologist….discovered
animals are made of
cells.
Nerve Cells

9. 1855 - Rudolph Virchow
• “Omnis cellula e cellula”
“All cells are from other
pre-existing cells.”
Discovered while
researching cancer cells.

10. The Cell Theory
1. All living organisms are composed of one or more cells.
2. Cells are organisms' basic units of structure and function.
3. Cells come only from pre-existing cells.

11. How do you measure cells?
Cells are measured using “microns”.
A micron is another casual name for a
micrometer.
Note: 1.0 µ m = one millionth of a meter

12. What limits the size of a cell?
• Cell volume to surface area ratios favor
small size... an efficient amount of
materials must enter and leave the cell.
• Nucleus’ ability to control the cell is
limited by the size of the cell.

13. Types of Cells

14. Prokaryotes
•
Lack a nucleus and other
membrane bound
organelle.
First appeared 3.5 BYA
include bacteria
and cyanobacteria.
E. coli

15. Eukaryotes
Have a nucleus and membrane
bound organelle.
First appeared 2.0 BYA
include protists, fungi, plants
and animals.

16. Basic Cell Organization
• Cell (Plasma) Membrane
• Nucleus (eukaryotes only)
• Cytoplasm (an area!!)
• Organelles (structures with specialized functions)

17. Animal
Cell

18. Plant Cell

19. The Cell Membrane
AKA: Plasma Membrane
• Separates the cell from the
environment.
• Is “semi-permeable”…… regulates
the movement of materials in/out of
a cell.
• ALL cells have a plasma membrane

21. The Cytoplasm
• The Cytoplasm is an Area (not stuff)
between the plasma membrane and
the nuclear envelope. The cytoplasm
contains the cytosol, nucleus (if
present) and cell organelles.

22. Cytosol
• Semi-fluid portion of the cytoplasm (the
gooey stuff inside the cell)….
Composed mostly of water, nutrients.
nutrients

23. Nucleus
• Most conspicuous organelle.
• usually spherical, but can be lobed or
irregular in shape.
• Typically found near the center of a
eukaryotic cell…..prokaryotes do not have a
nucleus.
• Control center for the cell.
• Contains the genetic instructions.

25. Nuclear Envelope
… the outer boundary of the
nucleus which gives the
shape to the nucleus.

26. Nucleolus
• Dark area in the nucleus.
• 0 - 4 per nucleus.
• Storage area for ribosomes.

27. Chromatin
• DNA and Protein in a “loose” format
(stringy form of DNA) Will eventually
form the cell’s chromosomes. The DNA
holds the cell’s genetic information.
• Found in the nucleus of eukaryotes and
in the center region of prokaryotes.

28. The Cell Organelle
• Term means "small organ” Formed
body in a cell with a specialized
function.
• Keeps various enzymes separated in
space.
(bags of enzymes)

29. Ribosomes
• Structure: made up of protein and RNA
• No membrane.
• Function: site of protein synthesis.

30. Ribosome Locations
• Free in the cytosol…..make proteins for
use in cytosol.
• Attached to the Endoplasmic
Reticulum….. make proteins that are
exported from the cell.

31. Ribosomes

32. Endoplasmic Reticulum
• Often referred to as ER.
• Stacks of flattened stacks involved in
the production and transportation of
proteins, sugars, fats,…..etc

33. Rough ER
• Endoplasmic
reticulum with
attached
ribosomes.
The attached
ribosomes
create proteins

34. Smooth ER
• Endoplasmic
Reticulum without
Ribosomes…..
Responsible for
producing lipids
and hormones,
especially in cells
that export these
substances from
the cell. In liver
cells, the smooth
ER breaks down
toxins and drugs.

36. Golgi Apparatus
AKA Golgi bodies or Golgi Complex
• Structure: flattened sacs arranged in a
stack. (looks like a stack of Pita bread)
• 3 to 20 per cell.
• The Golgi Apparatus package and modify
proteins and lipids into vesicles (small,
spherical shaped sacs that bud from the
Golgi apparatus). The vesicles often merge
with the plasma membrane to release
contents to the outside of the cell.

39. Lysosome
• Vesicles from the Golgi apparatus
that contain digestive enzymes.
They breakdown food, cellular
debris and foreign invaders such
as bacteria.
• Assist with cell death.
• Not present in plant cells.

41. Peroxisomes
• Organelles that breakdown various
substances. During digestion
0xygen is produced and combines
with H2O to form Hydrogen
Peroxide…. a toxin. Peroxisomes
break down Hydrogen Peroxide.

42. Mitochondria
• Function: Site of Cellular Respiration – Cellular
Respiration is the release of energy from food to
form ATP…. All cells use ATP as their energy
source.
• “Powerhouse” of the cell.
• Found in the cytosol.
• Have their own DNA. Can reproduce themselves.

44. Chloroplasts
• Function: Site of Photosynthesis - chloroplasts
use of light energy to make food, sugars, from
carbon dioxide and water.
• Contain the green pigment chlorophyll.
• Found in the Cytosol
• Have their own DNA. Can reproduce themselves.

45. Chloroplasts

46. Enzymes in a
crystal

47. Chromoplasts
Function: store plant pigments such as
chlorophyll (green) and carotene (orange, red).
• Found in plants only.
• Classified (named) by color….example:
• “Chloro” means green, therefore a
chloroplast is a green plastid that stores
chlorophyll
• “Leuco” means white, therefore
Leucoplasts (AKA Amyloplasts) are
white plastids that store starch.

48. Cytoskeleton
• Network of protein fibers and in the cytoplasm.
Functions
• Give Cells structure and shape.
• Involved in Cell movement.
• Cytoskeleton is composed of 2 different types of
fibers, which are organized in deceasing
diameter….they are:
1. Microtubules
2. Microfilaments

49. Microtubule Function
Maintenance of cell shape.
Hold organelles in place.

50. Microfilaments
Function
• Responsible for Muscle contractions.
• Cytoplasmic streaming in plants, like
Elodea.
• Maintenance and changes in a cell’s shape.

53. Cilia and Flagella
Classified by their lengths and numbers
• Function - to move cells or to sweep
materials past a cell.
• Cilia - short, but numerous.
• Flagella - long, but few (usually only one).

55. Centrioles
• Usually one pair per cell, located close
to the nucleus.
• Found in animal cells only.
• Help in cell division.

56. Basal Bodies
• Same structure as a centriole.
• Found at the base of the cilia and
flagella.
flagella

57. Basal Body

58. Plant Cell Walls
• All plant cells have a Primary Cell Wall.
• Some cells will develop a Secondary Cell
Wall.

59. Cell Walls
• Plant cell walls are made of cellulose
( a polysaccharide made of β -glucose).
• Fungi cell walls are made of chitin (a
polysaccharide)
• Function as the cell's exoskeleton for support and
protection.

60. Middle Lamella
• Thin layer rich in pectin (used to make
jelly) found between adjacent plant
cells.
• Glues cells together.

62. Vacuoles and Vesicles
Fluid-filled, membrane-bound bodies
3 Types of Vacuoles and Vesicles
• Food vacuoles
• Central water vacuoles
• Contractile vacuoles

63. The function of the vacuole depends
on the organism.
In Protists
single-cell organisms …….“Food” vacuoles
store newly ingested food until the
lysosomes can digest it.
• “Contractile” vacuoles pump out excess
water.

64. Contractile Vacuole
Contractile Vacuole
Food Vacuoles

65. Central Water Vacuole
• Large single water containing vacuole
making up to 90% of the cell's volume.
• Stores Water
• Helps the cells maintain their shapes.

66. Central Water Vacuole

67. Comparing Plant Cells and
Animal Cells
Plant Cells
Have cell walls,
chloroplasts, and a
central water vacuole…
animal cells do not!!
Animal Cells
Have lysosomes and
centrioles…. Plant
cells do not!!