The document discusses the history and development of cell theory from early microscopists in the 1600s-1800s to modern electron microscopy techniques. It covers key contributors like Van Leeuwenhoek, Hooke, Brown, Schleiden, Schwann, Virchow and Weismann and how their findings built upon each other to establish the core principles of cell theory. The document then provides details on the structures and functions of plant and animal cells as well as their organelles like the cell wall, cell membrane, nucleus, mitochondria, chloroplasts, vacuole and more.

1. Unit : cells – the basic units of
life
Created BY: Ms Mwelase

2. HOW to study cells.
The study of cells and micro organisms has changed over
time with the change in technology.
These were studied in the beginning with hand lenses,
single lens microscope, light microscope
Today we have electron microscopes.
Two types of electron microscopes are used today: SEM –
Scanning electron microscope and TEM – Transmission
electron microscope.

3. 1632-1723
ANTON VAN LEEUWENHOEK
 Developed a microscope
with one lens.
 Discovered
- bacteria
- blood cells
- spermatozoa
- protozoa

4. 1662 – ROBERT HOOK
 Uses the concept cell
for the first time.
 He used it when he
looked at the
microscopic structure
of cork cells.

5. 1831 – ROBERT BROWN
(Botanist)
Describes the nucleus of a cell

6. 1838-1839
MATTHIAS SCHLEIDEN (Botanist)
THEODOR SCHWANN (Zoologist
Developed the cell theory:
- Plants and animals are made of groups
of cells.
- The cell is the basic unit of living
organisms

7. 1855 – RUDOLPH VIRCHOW
 Expanded the cell theory:
 He said that new cells formed by the
division of existing cells

8. 1880 – AUGUST WEISMANN
 Expanded the cell
theory more:
 He said that all cells
can be traced to their
origin

9. Schleiden, Schwann and Virchow
compiled the cell theory
All living organisms are made out of cells
New cells are formed by the division of existing cells
The cell houses genes, which are the blueprint for
growth, functioning and development of cells
The cell is the functional unit of life because all
chemical reactions of life take place inside the cell

10.  A cell is the basic unit of structure
and function in organisms.
 Cells differ in size, shape and in
function.
 A cell consist of smaller structures
called organelles.

11. Two types of cells
Prokaryotic or Eukaryotic cells.
Only organisms of the domains Bacteria
and Archaea consist of prokaryotic cells –
cells without a membrane bound nucleus.
Protists, fungi, animals and plants all
consist of eukaryotic cells – cell with a
membrane bound nucleus.

12. General structure of an animal cell as
seen under a light microscope (called a
micrograph)

13. Line diagram of a general animal cell

14. Micrograph of a general plant cell

15. Line diagram of a general plant cell

16. DIFFERENCES BETWEEN PLANT- AND
ANIMAL CELL
PLANT CELL ANIMAL CELL

17. STRUCTURE AND FUNCTIONS OF
THE DIFFERENT ORGANELLS OF
CELLS
Chapter 6 p. 98 – 131

18. CELL WALL
(ONLY IN PLANT CELLS)
Porous
Varies in thickness
Consist of pectin (elasticity), cellulose fibrils held together
with non-cellulose substances (hardens the cell when
mature) and lignin (adds strength to cell especially in woody
plants)
Cell wall is permeable and protects the inside of the cell.
Middle lamella (layer of adhesive substances) – holds the
cells together
Plasmodesmata (pores) that connects the cytoplasm of the
connecting cells – selectively permeable

19. CELL WALL WITH PLASMODESMATA AND
INTERCELLULAR SPACES

20. CELL MEMBRANE/PLASMA- (ANIMAL-
AND PLANT CELLS)
Consist of 2
phospholipid layers and
proteins in between.
The phospholipid layers
are part hydrophillic
and part hydrophobic

21. NUCLEUS
+/- 5µm, largest organelle in cell.
Enclosed by a nucleomembrane with
nuclear pores. Function: Protection and
add to selective permeability.
Filled with nucleoplasma, a nucleolus
and chromatin. Function of chromatin:
carries genetic material in the form of
chromosomes.
Function of nucleolus: Produce r-RNA

22. MITOCHONDRION
Consist of 2 membranes: Outer – and
a highly convoluted inner membrane-
These folds are called cristae – they
increase the surface area.
Filled with matrix called stroma that
contains DNA and ribosomes.
Function: Produce energy in the form
of ATP by means of cellular
respiration

23. CHLOROPLAST
(PLANT CELL ONLY)
Enclosed by a double membrane
Filled with stroma and thylakoids
filled with chlorophyll arranged
in groups called grana.
Ribosomes and starch grains in
stroma.
Function: Photosynthesis

24. VACUOLE
(Large in plant-, small in animal-)
Membranous sac
Filled with cell sap.
Causes turgor pressure in the
vacuole.
Function: Stores various
substances, including waste.
Helps with osmotic potential of
cell.

25. OTHER SMALLER ORGANELLES
Endoplasmic Reticulum – Transport
system in cell
Ribosomes – Protein synthesis
Golgi-apparatus – Make lysosomes and
acts as transport system.
Lysosomes – Intracellular digestion.
Plastids e.g.– Leucoplasts – Stores
starch
- Chromoplast – gives colour
to flowers and fruit.
* Centrioli – Mitosis in animal cells

26. PERMEABILITY OF THE CELL
MEMBRANE
The cell membrane has the ability to
regulate transport molecules across its
structure.
This function is essential to the cell’s
existence.
The fluid mosaic model helps to
explain how membranes regulate the
cell’s molecular traffic.

27. Permeability of the lipid bilayer
Hydrocarbons, carbon dioxide and oxygen
– non-polar
So they can dissolve in the lipid bilayer of
the membrane.
They can cross the membrane without the
aid of membrane proteins.
Polar molecules like, water and glucose
move slowly across the membrane and
need the aid of proteins to get across the
membrane.

28. TRANSPORT PROTEINS
Hydrophyllic substances can avoid
contact with the hydrophobic lipid bilayer
by passing through transport proteins that
span the membrane.
Channel proteins – tunnel for polar
molecules to pass through membrane
Aquaporins – channel proteins for the
transport of water

29. Carrier protein: Hold onto solutes that want
to move across the membrane and changes
shape as it moves through the membrane.
Each carrier protein is specific to what it
transports.

30. 1. If the Golgi-apparatus of a cell is destroyed, that cell would
_____________
stop releasing cellular products.
become a dictyosome.
release digestive enzymes in the cytoplasm for self-digestion.
behave normally.
2. Which of the following characteristics does not apply to
mitochondria?
Double unit membrane.
Connected to the ER.
Inner membrane is folded.
Larger than ribosomes.

31. 1. Which is not a key point in the cell theory?
All living cells consist of one or more cells.
The cell is the basic unit of life.
No cell can exist unless at least one other cell is present.
New cells arise only from cells that already exist.
2. The main constituent of most cell walls in plants is_____.
glucose.
glycogen.
proteins and phospholipids.
Cellulose.
3. Which of the following is found in both plant and animal cells?
Chromosomes
Chromoplasts
Chondrocytes
Leucoplast

32. Part of the nucleus that mainly consist of RNA.
The inner plasma membrane in the cell surrounding the
vacuole.
Organelles in living cells that contain enzymes,
Give 2 functions of the plasma membrane.
What is Archaea?