In this slide I have described basic molecular biology of cell. I have discussed cell theory. Formation of cell theory and it's working. Moreover briefly discussed cell structure and organelles with their functions.

1. “in the name of Allah the most beneficent, the most merciful.”

2. Lecture by:
Saba Mahmood
Cell Structure and
Function

3. The Cell
 From Latin –Cella, meaning “Small room”
The cell is the basic structural and functional unit of all known living
organisms (building blocks of life)
Plant
Stem
Red
Blood
Cell
Amoeba
Proteus
Bacteria
Nerve
cell

4. Cell theory
1. All living things are made up
of 1 or more cells.
2. Cells are the smallest
working units of all living
things.
3. All cells come from pre-
existing cells through cell
division.

5. Cell theory timeline

8. Protoplasm
o Different substances that make a cell are collectively called Protoplasm
o Protoplasm is composed of:
1) Water 70-80% water present in cell
2) Carbohydrates
3) Lipids
4) Proteins
5) Electrolyte-Sodium (Na+), Potassium (K+), Magnesium (Mg2+), Calcium
(Ca2+), Phosphate, Chloride (Cl-) and Bicarbonate (HCO3-)

9. Unicellular Organisms
• An organism that is made up of only one cell is called as unicellular
organisms

10. Multicellular organisms
• An organisms that is made up of more than one cell is called as
multicellular organism.

11. Prokaryotic cells
• Prokaryotes :do not
have a nucleus or
organelles (bacteria)
• Cell size ranges from 0.1
to 0.5 µm in diameter
• Examples: Bacteria and
blue green algae

12. Eukaryotic cells
• Eukaryotes have a well-
developed nucleus and
membrane-bound
organelles Size of cell
ranges between 5–100
µm in diameter
• Examples: plants, fungi,
animals and protists

13. Cell organelles
• Cell structures that have a specific function and are
surrounded by a membrane that are found in eukaryotes
• Major structure present in cells are:-
oCell membrane
oCytoplasm and its organelles
oNucleus

14. The Animal Cell

15. The Plant Cell

16. Cell Wall
o Non-living and outermost covering of a cell (Pant & Bacteria)
o Can be tough, rigid and sometimes flexible
o Made up of cellulose, hemicellulose and pectin
o Maybe thin, thick or multilayered structure
Functions:
• Provides definite shape, strength and rigidity
• Prevent drying up (desiccation) of cell
• Help in controlling cell expansion
• Protect cell from external pathogen

17. Cell or Plasma membrane
• Protective sheath enveloping cell body separates the fluid
outside the cell called extracellular fluid (ECF) and the fluid
inside the cell called intracellular fluid (ICF).
• Extremely delicate, thin, elastic, living and semipermeable
membrane
• Made up of two layer of lipid molecule in which protein
molecules are floating
• Thickness varies from 75-110A
• In plants and bacteria, this is within the cell wall.

19. Function
Protects internal contents of cell
Selective permeability
Regulates entry and exit of substances in and out of cell
Maintains homeostasis
Exchange of gases
Maintenance of shape and size of cell

20. Cytoplasm
• Jelly-like material formed by 80% of
water
• Present between the plasma
membrane and nuclear membrane
• Contains a liquid portion called
cytosol and various particles
• Particles are protein, carbohydrates,
nucleic acid, lipids and inorganic
ions
• Contains cell structure that carry
out specific functions ex.
Mitochondrion, nucleus
• Provides a medium for chemical
reactions to take place
• It is made up of two zones

21. Endoplasmic Reticulum
• Network of tubular and vesicular structures which are interconnected with
one another
• Some parts are connected with nuclear envelop while other are connected
to cell membrane
• Two types: smooth (lack ribosomes) and rough (stubbed with ribososmes)
Functions:
• Gives internal support to cytoplasm
• Internal delivery system of the cell.
• RER manufactures, pro- cesses, and transports secretory and membrane
proteins for export from cell
• SER synthesize lipids, steroids, involved in carbohydrate metabolism and
detoxification of drugs and proteins.

23. Ribosomes
• Organelles that direct the synthesis of proteins using genetic
instructions in the form of messenger RNA
• Sites of protein synthesis
• Usually exist in large number in living cells

24. Free ribosomes
 Suspended in cytosol
 Synthesize proteins that function
in cytosol
Bound ribosomes
 Attached to endoplasmic
reticulum
 Synthesize proteins for export or
for membranes
 Proteins work within
endomembrane system or
outside cell

25. Golgi Apparatus
o Discovered by Camillo Golgi
o Formed by stacks of 5-8 membranous sacs
o Sacs are usually flattened called cisternae
o Has two ends: cis face situated near the endoplasmic
reticulum and trans face situated near the cell membrane
Functions:
o Modifies, sorts and package materials synthesized in the cell
o Deliver synthesized materials to various targets inside the cell
and outside the cell
o Enclose digestive enzyme into membrane to form vacuoles

26. Molecule transport via GA

27. Endomembrane system

28. Lysosomes
o Small, spherical, single membrane sac
o Found throughout the cytoplasm
o Filled with hydrolytic enzymes
o Occur in few animal cells and few in plant cells
Functions
o Help in digestion of protein, fats, and carbohydrates
o Digestive enzyme breakdown of cellular waste and debris
o Protects cells by destroying foreign invaders like bacteria and viruses
o In dead cells perform autolysis

29. Mitochondria
o Small, rod shaped organelles (Site of cellular respiration) bounded by
two membranes-inner and outer
o Outer membrane is smooth and enclose the contents of mitochondria
o Inner membrane folded in the form of shelf like inward projections
called cristae
o Inner cavity is filled with matrix which contains many enzymes
o Contains their own DNA which are responsible for many enzymatic
actions

30. Functions:
• Power generating unit of cell
• Synthesize energy-rich compounds(use glucose to produce cell energy,
ATP)
• Important to maintain proper concentration of calcium ions within
various compartment of cells
• Energy transduction through respiration
• Responsible for thermogenesis

32. Vacuoles
• Single membrane sac filled with liquid or sap (water, sugar and ions)
• In animal cell, vacuoles are temporary, small in size and few in number
• In plant cell, vacuoles are large and more in number
• Maybe contractile or non-contractile
Functions:
• Store various substances including waste products
• Maintain osmotic pressure of cell
• Store food particles and nutrients in plant and amoeba cell
• Provides turgidity and rigidity to plant cell

34. Chloroplasts
o Double membrane-bound organelles found mainly in plant cells
o Usually spherical or discoidal in shape
o Shows two distinct regions-grana and stroma
o Grana are stacks of thylakoids
o Thylakoids contain chlorophyl molecule which are responsible for
photosynthesis
Functions:
o Convert light energy into chemical energy in the form of food
o Provide green colour to leave, stem and vegetables

36. Centrosome
• Membrane-bound organelles present near the nucleus
• Consist of two structures called centrioles
• Centrioles are hollow, cylindrical structures made up of microtubules
• Centrioles are arranged at right angle to each other
Functions:
 Form spindle fibers which helps in the movement of chromosomes
during cell division
 Help in the movement of cilia and flagella

38. Cytoskeleton
• Cellular organelles present throughout the cytoplasm
• Complex structural networks of protein tubules and tracks
 Microtubules (hollow tubules made up of protein tubulin)
 Intermediate filaments (network around nucleus formed by rope like polymer-
fibrous protein-keratin)
 Microfilaments (rod shaped thin filaments made up of protein called actin)
Functions:
o Determines shape of cell
o Give structural strength of cell
o Resist mechanical stress or external pressure
o Processes that move secretion granules in cell

40. Nucleus

41. Nucleus
• Dense spherical body located near the centre of cell
• Diameter varies from 10-25μm
• Nucleus has double layer covering called nuclear membrane
• Colourless dense sap present inside nucleus known as nucleoplasm
• Nucleoplasm contains round shaped nucleolus and network of
chromatin fibres
• Fibres are composed of deoxyribonucleic acid (DNA) and protein
histone
• These fibres condense to form chromosomes during cell-division
• Chromosomes contains stretches of DNA called genes
• Genes transfer the hereditary information from one generation to

43. Function
o Control all the cell activities like metabolism, protein synthesis,
growth and cell division
o Nucleolus synthesize ribonucleic acid (RNA) to constitute
ribosomes
o Sending genetic instruction to cytoplasm for protein synthesis
through messenger RNA (mRNA)
o Storage of hereditary information (in genes) and transformation
of this information from one generation of species to the next

44. Summary

45. General function of Cell
Provides support and structure
Facilitate growth via mitosis and miosis
Allows transport of substance
Energy production
Aids in reproduction