1. Cell Theory, Microscopy, Prokaryotes
CELLS
Cell Theory, Microscopy, Prokaryotes

2. CELL THEORY All living things are composed of cells and cell products.
New cells are formed only by the division of existing cells.
The cell contains inherited information (genes) that are used as instructions for growth, functioning and development.

3. CELL THEORY, continued
The cell is the functioning unit of life; the chemical reactions of life take place within cells.

4. Possible Exceptions to the Cell Theory

5. The structure of skeletal muscle
Bundle of muscle fibers
Single muscle fiber
(cell)
Plasma membrane
Myofibril
Light band
Dark band
Z line
Sarcomere
TEM
0.5 m
I band
A band
M line
Thick filaments (myosin)
Thin filaments (actin)
H zone
Nuclei
Muscle consists of bundles of long cells called fibers.
Each fiber has a membrane around the outside like a single cell
But each fiber has hundreds of nuclei.

6. Figure 31.2: Structure of a multicellular fungus
Reproductive structure. The mushroom produces tiny cells called spores.
Hyphae. The mushroom and its subterranean mycelium are a continuous network of hyphae.
Spore-producing structures
20 m
Mycelium

7. Figure 31.3: Structure of fungal hyphae
Cell wall
Cell wall
Nuclei
Pore
Septum
Nuclei
(a) Septate hypha
(b) Coenocytic hypha

8. SOME (but not most!) biologists consider unicellular organisms to be acellular.
Examples: Amoeba and Acetabularia
instead of separate cells for separate functions, cytoplasm must carry out all vital functions
usually much larger than typical cells
Amoeba proteus ~ µm
Acetabularia > 7 cm in length

11. The animal cell

12. The plant cell

13. Cell differentiation

16. Task
Look at the diagram and list similarities and differences between the two cells.

17. Prokaryotic Cells

18. Prokaryotic Cells
Pro – before
Karyon – nucleus
Comprise domains Bacteria and Archaea (Archaebacteria)

19. Electron microscope views of prokaryotic cells

22. Functions of the parts of a prokaryotic cell
Cell wall – forms protective outer layer which prevents damage from outside and bursting if internal pressure is high
Plasma membrane – controls entry and exit of substances, pumping some in by active transport

23. Functions of the parts of a prokaryotic cell, cont’d.
Mesosome – increases the area of membrane for ATP production; may move DNA to poles during cell division
Cytoplasm – contains enzymes that catalyze chemical reactions of metabolism; also contains cell’s DNA, in region known as nucleoid

24. Functions of the parts of a prokaryotic cell, cont’d.
Ribosomes – synthesize proteins by translating mRNA; some proteins remain in cell and others are exported
Naked DNA – stores genetic information that controls cell and is passed onto daughter cells.

25. Metabolic activities in prokaryotes
Photosynthesis – carried out by Cyanobacteria (sometimes called blue-green “algae”)

26. Metabolic activities in prokaryotes, cont’d.
Nitrogen fixation – nitrogen fixing bacteria convert nitrogen gas from the air into nitrogen compounds
some are free-living bacteria
some live in symbiosis with plants, such as Rhizobium, forming root nodules on legumes

27. Metabolic activities in prokaryotes, cont’d.
Fermentation - process by which an sugar is broken and energy released.
occurs during times of low oxygen supply and is therefore known as a type of anaerobic respiration