1. Cell Structure and Function
Hail University
Faculty of Sciences
Department of Biology
Practical Biology Biol 101 Lab 3
Cell Structure and Function

2. The cell is the structural and functional unit of all living organisms.
Robert hooke was the first scientist who look at cells under a microscope by viewing and describing the box – like structures of cork.
Researches had formulated the cell theory that has three principles:
All organisms are composed of one or more cells.
The cell is the basic functional unit of living organisms.
All cells arise by division of pre-existing cells

3. All cells share four structural features: Plasma membrane
Delineate the border of the cell
Function in regulate the passage of materials into and out of the cell.
Deoxyribonucleic acid (DNA)
Function as the genetic instructions for the cell.
Plasma membrane
Genetic material DNA

4. Function as a site of protein synthesis Cytoplasm
Plasma membrane
Ribosomes
Function as a site of protein synthesis
Cytoplasm
Components enclosed by the plasma membrane by which the rest of organelles are floating.
Ribosome
Cytoplasm
Genetic material DNA

5. Cells vary in:
Size
Function
Organization
With respect to internal organization there are two major types of cells according to the presence of nucleus.
Nucleus is the spherical organelle within the cytoplasm, which contain the genetic materials (DNA) and controls cell metabolism and division.

6. Prokaryotic (before the nucleus)
Eukaryotic (true nucleus)

7. Prokaryotic
Eukaryotic
Unicellular
unicellular ex. Protists
multicellular ex. Animal, plants and fungi
Small cell size (0.5 – 5 µm)
Large cell size (5 – 200 µm)
Don’t have organized nucleus surrounded by nuclear membrane and the DNA found free in the cytoplasm
Have organized nucleus enclosed by a nuclear membrane, the DNA found within the nucleus
Don’t have membrane bound organelles
Have membrane bound organelles ex. mitochondria
In this lab. We will examine a prepared slides of different bacterial cell shapes
In this lab. We will examine and describe cells of humans (animals) and onions (plants)

8. Basic shapes of bacterial cells
Spheres (cocci)

9. Rods (bacilli)

10. Spirals

11. Human cheek epithelial cells
The cells that line the inner check (inside the mouth) called epithelial cells, easily removed by:
With a clean toothpick, gently scrape the inside of your cheek several times.
Roll the scraping into a drop of water on a clean microscope slide.
Add a small drop of methylene blue.
Cover with coverslip gently.
Discard the used toothpick.
Examine under microscope and notice:

12. The cell appear as pentagons
The cells are flat
The nucleus will be blue
The cytoplasm will stain light blue
The cell membrane

13. Onion epidermal cells
Prepare a wet mount of onion epidermal tissue according to the steps
Cut an onion bulb into quarters.
Remove one of the fleshy scale leaves

14. Fold the leaf backward to produce a ragged piece of epidermis.
Peel back a small piece of epidermis.

15. Observe under microscope and notice
Spread the epidermis in a drop of water on a slide
Add a small drop of Lugol’s solution, gently cover it by cover slip to avoid air bubbles
Add a small drop of Lugol’s solution, gently cover it by cover slip to avoid air bubbles
Observe under microscope and notice

16. The shape of onion cells
The nucleus
The cell wall
Cytoplasm

17. Plant cell Cell wall Cell membrane Golgi apparatus Ribosome
Chloroplast
Smooth ER
Nucleus
Rough ER
Large central vacuole
Mitochondrion
Cytoplasm

18. Animal cell Mitochondrion Lysosome Golgi apparatus Rough ER Nucleus
Smooth ER
Cell membrane
Cytoplasm
Ribosome

19. Animal cells compared with plant cells
Chloroplast -
Cell wall
Central vacuole

20. Thank You