cell size, cell shape, cell structure

1. University of Duhok
College of Health Sciences
Dep. of Medical Laboratories
Biology/1st Stage
Lecture 2
Dr: Shameeran S. Ismael
BVM & S, M.Sc Medical Microbiology(Parasitology),
PhD Molecular Parasitology

2. Size of cell
• Cells vary in size. Most cells are very small
(microscopic), some may be very large
(macroscopic).
• The unit used to measure size of a cell is
micrometer:
1 µm = 1/1000 millimeter

3. Smallest cell is Mycoplasma
it is size: 0.1 µm
Largest cell is Ostrich egg it
is size: 18 cm

4. Size of Cells in Humans

5. Shape of cell
• Cells vary in shape.
• Variation depends mainly upon the function of
cells.
• Some cells like Euglena and Amoeba can
change their shape, but most cells have a fixed
shape.

6. • Human RBCs are circular
biconcave for easy passage
through human capillaries.
• Nerve cells are branched to
conduct impulses from one
point to another.
• Human WBCs can change
their shape to engulf the
microorganisms that enter
the body.

7. Cell types:

10. 10
Eukaryotes
• Cells that have a nucleus and
membrane-bound organelles
• Includes protists, fungi, plants, and
animals
• More complex type of cells

11. 11
Eukaryotic Cell
Contain 3 basic cell structures:
1. Cell Membrane
2. Nucleus
3. Cytoplasm with organelles

12. 12
Two Main Types of Eukaryotic
Cells
Plant Cell Animal Cell

13. 13
1.Cell or Plasma Membrane
Outside
of cell
Inside
of cell
(cytoplasm)
Cell
membrane
Proteins
Protein
channel Lipid bilayer
Carbohydrate
chains
• Composed of double layer of phospholipids and proteins
• Surrounds outside of all cells
• Controls what enters or leaves the cell
• Living layer

14. Functions:
• Maintains shape & size of the cell
• Separates cell from outside
• Protects internal contents of the cell
• Recognizes signals from other cells
• allows communication between cells
• Regulates entry and exit of substances in and
out of the cell (O2, CO2, food, H2O, nutrients
And waste)

15. Cell Membrane
lipid “tail”
phosphate
“head”

16. cell membrane
cell boundary
controls movement
of materials in & out
recognizes signals
cytoplasm
jelly-like material holding
organelles in place

17. 17
Phospholipids
• Heads contain glycerol & phosphate
and are hydrophilic (attract water)
• Tails are made of fatty acids and are
hydrophobic (repel water)
• Make up a bilayer where tails point
inward toward each other
• Can move laterally to allow small
molecules (O2, CO2, & H2O to enter)

18. 18
The Cell Membrane is Fluid
Molecules in cell membranes are constantly
moving and changing

19. 19
Cell Membrane Proteins
• Proteins help move large molecules or aid in
cell recognition
• Peripheral proteins are attached on the
surface (inner or outer)
• Integral proteins are embedded completely
through the membrane

20. Cell wall
• Non-living layer
• Found outside of the cell membrane
• Supports and protects cell
• Found in plants, fungi, & bacteria
• Rigid and sometimes flexible
• Made up of cellulose, hemicellulose and
pectin
• May be thin or thick, multilayered structure

21. 21
Cell wallCell Wall

22. 2. Nucleus
• Dense spherical body located near the centre
of the cell. Is a Control center of the cell
• Present in all cells except red blood cells and
sieve tube cells
• Most of the cells are uninucleated (having only
one nucleus)
• Few types of cells have more than one nucleus
(skeletal muscle cells)

23. Surrounded by a double membrane called the
nuclear membrane or nuclear envelope.
Nuclear envelope has thousands of pores
which allow material to move into and out of
the nucleus.

24. • Contains DNA which contains the coded
instructions for making proteins which are the
molecules that do “everything”.
• There are thread-like material in the nucleus is
called chromatin which is DNA wrapped around
protein.
• Usually looks like this but as a cell prepares to
divide, chromatin condenses to form
chromosomes.

25. Chromosomes

26. Nucleolus
Small dense region within
the nucleus
Produces the ribosomes

27. 27
• Jelly-like substance
enclosed by cell
membrane
• Provides a medium for
chemical reactions to
take place
3.Cytoplasm of a Cell
cytoplasm

28. Cytoplasm: is everything inside the cell
membrane, except the nucleus. Contains
organelles to carry out specific jobs
Organelles: means little organ
Cytosol: or the intracellular fluid is the liquid
found inside cells

29. Cytoplasmic organelles:
1. Endoplasmic reticulum (rough and smooth)
2. Ribosomes
3. Golgi complex
4. Vesicles
5. Lysosomes
6. Perioxisomes
7. Mitochondria
8. Vacuole
9. Centriole

30. 1.Endoplasmic Reticulum (ER):
• The internal membrane system of the cell
• It is a large network of membrane that builds
cell material.
• It looks like long tubules or bags.
• It encloses fluid filled lumen
• Helps move substances within cells

31. There are two types:
1.Rough endoplasmic reticulum:
• It has ribosomes attached to its surface
• That functions in protein synthesis
2.Smooth endoplasmic reticulum::
• It doesn't have ribosomes attached to its
surface.
• That function in lipid synthesis

33. RER VS SER

34. Function of Endoplasmic Reticulum
• It is associated with synthesis, storage and
transport of metabolic products
• It gives internal support to the colloidal matrix
• It helps in the formation of new cell
membrane
• Rough endoplasmic reticulum: It is concerned
with the protein synthesis
• Smooth endoplasmic reticulum: It is concerned
with enzymes and lipid formation

35. Ribosomes
• Ribosomes are dense spherical granular
particle which move freely in the matrix. site
of protein synthesis
• They are present in the cytoplasm as well as
inside the nucleus
• Ribosomes is made up of numerous proteins
and RNA
• Found either free or bound to endoplasmic
reticulum

36. Function of Ribosomes
• They play an important role in protein
synthesis.
• It helps in storage modification and packaging
of products in the vesicles.
• It involves in the synthesis of lysosomes.

37. Ribosomes

38. Thanks for attention,,