Chapter 4 (Prokaryotic and Eukaryotic Cell).pdf

Structure and function of Prokaryotic and eukaryotic cells

1. CHAPTER 4
FUNCTIONAL ANATOMY OF PROKARYOTIC AND
EUKARYOTIC CELLS

2. INTRODUCTION TO CELLS
•ALL LIVING CELLS FALL INTO TWO MAIN GROUPS: PROKARYOTES AND
EUKARYOTES.
•EUKARYOTES INCLUDE PLANTS, ANIMALS, FUNGI, AND PROTOZOA.
•PROKARYOTES INCLUDE BACTERIA AND ARCHAEA.

3. COMPARISON BTW. PROKARYOTES &
EUKARYOTES
SIMILARITIES
•BOTH CONTAIN NUCLEIC ACIDS, PROTEINS, LIPIDS, AND CARBOHYDRATES.
•THEY USE SIMILAR CHEMICAL REACTIONS FOR METABOLISM.

4. KEY DIFFERENCES
Prokaryotes Eukaryotes
DNA is not in a membrane-enclosed nucleus (usually a
single, circular chromosome).
DNA is in a membrane-enclosed nucleus (multiple
chromosomes).
DNA is not associated with histones. DNA is associated with histones.
Generally, lack membrane-enclosed organelles.Have membrane-enclosed organelles (e.g.,
mitochondria, endoplasmic reticulum).
Cell walls almost always contain peptidoglycan.Cell walls (when present) are chemically simple and
do not contain peptidoglycan.
Divide by binary fission. Divide by binary mitosis.

5. THE PROKARYOTIC CELL
•Key Characteristics:
•DNA Is A Single, Circular Chromosome Not Enclosed By A Membrane.
•DNA Is Not Associated With Histones.
•Generally, Lack Membrane-bound Organelles.
•Cell Walls Almost Always Contain Peptidoglycan.
•Divide By Binary Fission.
•Bacteria Vs. Archaea:Look Similar But Have Different Chemical
Compositions.

6. SHAPES AND ARRANGEMENTS OF BACTERIA
THREE BASIC SHAPES:
1.COCCUS:SPHERICAL
2.BACILLUS:ROD-SHAPED
3.SPIRAL:HELICAL

7. COCCI ARRANGEMENT
The arrangement depends on the
plane of division.
•Diplococci:pairs (from dividing in one plane)
•Streptococci:chains
•Tetrads:groups of four
•Sarcinae:cubelike groups of eight
•Staphylococci:grapelike clusters

8. BACILLI
ARRANGEMENT
•Single bacilli:individual rods
•Diplobacilli:pairs after division
•Streptobacilli:chains after division
•Coccobacilli:oval-shaped rods,
resembling both cocci and bacilli.

9. SPIRAL BACTERIA
ARRANGEMENT
•Vibrios: Curved rods, like a
comma.
•Spirilla: Helical, rigid bodies that
move with flagella.
•Spirochetes: Helical, flexible
bodies, move corkscrew motion

10. STRUCTURE EXTERNAL TO CELL WALL
•Glycocalyx: A sticky sugar coat outside the cell.
•Capsule: organized, firmly attached; protects against phagocytosis
and increases virulence.
•Slime layer: unorganized, loosely attached.

11. FLAGELLA
Long, whip-like appendages responsible for motility.
Composed of three parts:
1.Filament – made of flagellin protein.
2.Hook – connects filament to the basal body.
3.Basal Body – anchors the flagellum to the cell wall and membrane,
enabling rotation.

12. ARRANGEMENT OF FLAGELLA
•MONO TRICHOUS: SINGLE FLAGELLUM AT ONE END (E.G.,
VIBRIO CHOLERAE).
•LOPHOTRICHOUS: TUFT OF FLAGELLA AT ONE END.
•AMPHITRICHOUS: FLAGELLA AT BOTH ENDS.
•PERITRICHOUS: FLAGELLA ALL OVER THE SURFACE (E.G.,
ESCHERICHIA COLI).

14. THE CELL WALL AND
PLASMA MEMBRANE
Cell wall: provides structural support,
maintains shape, and protects against
osmotic lysis.
•Made of peptidoglycan, a
repeating disaccharide of n-
acetylglucosamine (NAGA) and n-
acetylmuramic acid (NAMA).
•Units are linked by β-1,4 linkages.

15. Fimbriae
•Short, hair-like structures made of protein (pilin).
•Help in adhesion to surfaces, host cells, and biofilm formation (e.G., Neisseria
gonorrhoeae).
Pili (conjugation pili)
•Longer than fimbriae but fewer in number.
•Facilitate dna transfer during bacterial conjugation (e.G., E. Coli f-pilus).
S-layer (surface layer)
•Crystalline protein or glycoprotein layer found in some bacteria.
•Provides structural support and protection against environmental stress.

17. GRAM STAINING MECHANISM
1.Crystal Violet (1 min) – Stain the smear purple.
2.Rinse with water (5 sec).
3.Iodine (1 min) – Acts as a mordant, forming a dye-iodine complex.
4.Rinse with water (5 sec).
5.Alcohol/Acetone (10–20 sec) – Decolorizer.
6.Gram-positive: stay purple (thick peptidoglycan holds dye).
7.Gram-negative: lose color (thin peptidoglycan, outer membrane disrupted).
8.Rinse with water (5 sec).
9.Safranin (1 min) – Counterstain, turns Gram-negative cells pink/red.
10.Final rinse with water (5 sec).
11.Blot dry and observe under microscope.

20. COME IN AND STAIN
C= CRYSTAL VIOLET
I= IODINE
A= ALCOHOL
S= SAFRANIN

21. THE ACID-FAST CELL WALL
Acid-fast Cell Wall (E.G., Mycobacterium)
•Composition: Thin Peptidoglycan Layer Plus A Thick, Waxy Coat Of
Mycolic Acid.
•Properties:
•Impermeable To Most Stains (Gram Stain Doesn’t Work).
•Resistant To Drying And Many Chemicals.
•Staining: Needs Acid-fast Stain (E.G., Ziehl–Neelsen).
•Clinical Significance: Provides Virulence And Resistance In Pathogens
Like Mycobacterium Tuberculosis (Tuberculosis).

22. Bright Red Rod-shaped Bacteria
(Mycobacterium Cells).
Background Is Stained Blue, Providing
Contrast, Non–acid-fast Cells Or Debris

23. INTERNAL STRUCTURES OF THE
PROKARYOTIC CELL

24. THE PLASMA MEMBRANE AND TRANSPORT MECHANISMS
Plasma Membrane: Inner Phospholipid Bilayer With Proteins, Enclosing The Cytoplasm. Acts As A
Selectively Permeable Barrier, Controlling Entry And Exit Of Substances.
•Passive Transport (No Energy, High → Low Concentration):
•Simple Diffusion: Small, Uncharged Molecules Move Directly Across.
•Facilitated Diffusion: Uses Transporter Proteins.
•Osmosis: Water Moves Across The Membrane.
•Active Transport (Requires ATP, Low → High Concentration):
•Uses Specific Transporter Proteins To Move Substances Against The Gradient.

26. Other Organelles

28. EUKARYOTIC CELL
Eukaryotes: Larger, more complex cells found in plants, animals, fungi, protozoa,
and algae.
•Key Feature: Have a membrane-bound nucleus and organelles.
•Fun Fact: “Eukaryote” means “true nucleus” (from Greek EU = true, karyon =
nucleus).

29. EXTERNAL STRUCTURES OF EUKARYOTIC CELLS
•Glycocalyx: Sticky Carbohydrate Layer For Protection And Cell Attachment.
•Flagella: Long, Whip-like Structures For Movement; Move In A Wavelike Motion.
•Cilia: Short, Numerous Projections That Beat In Coordination To Move The Cell Or
Materials Along Its Surface.

30. PLASMA MEMBRANE & CYTOPLASM
•Plasma Membrane: Phospholipid Bilayer With Proteins And Sterols (E.G.,
Cholesterol) For Rigidity; Selectively Controls Entry And Exit.
•Transport: Passive (Diffusion, Facilitated Diffusion, Osmosis) And Active
Mechanisms.
•Cytoplasm: Gel-like Interior With A Cytoskeleton For Support And
Movement; Shows Cytoplasmic Streaming (Active Flow Of Cytoplasm).

31. ENERGY-PRODUCING ORGANELLES
Mitochondria: The Cell’s “Powerhouses.”
•Structure: Double Membrane; Inner Folds (Cristae) Increase Surface Area.
•Function: Site Of Cellular Respiration; Produce ATP From Organic
Compounds.
•Unique Feature: Have Their Own Circular DNA And 70s Ribosomes →
Evidence For The Endosymbiotic Theory.

32. •Chloroplasts: In Plants And Algae; Double Membrane With Thylakoids (Grana).
Site Of Photosynthesis. Contain Their Own DNA And 70S Ribosomes.
•Peroxisomes: Contain Enzymes (E.G., Catalase) To Break Down Toxic Substances
Like Hydrogen Peroxide.
•Centrosomes: Present In Animals And Some Lower Plants; Organize Microtubules
And Form Spindle Fibers During Mitosis.

33. THE EVOLUTION OF EUKARYOTIC CELLS
The Endosymbiotic Theory States That Eukaryotic Cells Arose About 2
Billion Years Ago When Larger Prokaryotes Engulfed Smaller Ones,
Which Became Mitochondria And Chloroplasts. Evidence Includes Their
Circular DNA, 70S Ribosomes, And Replication By Binary Fission.