MODULE 3 MICROBIO

Differences Between Prokaryotic and Eukaryotic Cells:

● Prokaryotic Cells:

○ Lack a nucleus; their genetic material is located in a region called the nucleoid.

○ Generally smaller (0.2-2 μm).

○ Lack membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum).

○ Have a simple structure with a cell membrane, ribosomes, and cell wall (in

most).

○ Include bacteria and archaea.

● Eukaryotic Cells:

○ Have a true nucleus containing genetic material (DNA).

○ Larger (10-100 μm).

○ Contain membrane-bound organelles (e.g., mitochondria, chloroplasts, Golgi

apparatus).

○ Includes cells from plants, animals, fungi, and protists.

2. Basic Bacterial Shapes and Arrangements:

● Shapes:

○ Cocci: Spherical (e.g., Staphylococcus).

○ Bacilli: Rod-shaped (e.g., Escherichia coli).

○ Spirilla: Spiral-shaped (e.g., Helicobacter pylori).

○ Vibrio: Comma-shaped (e.g., Vibrio cholerae).

● Arrangements:

○ Diplococci: Pairs of cocci (e.g., Neisseria).

○ Streptococci: Chains of cocci (e.g., Streptococcus).

○ Staphylococci: Clusters of cocci (e.g., Staphylococcus).

○ Tetrads: Groups of four cocci (e.g., Micrococcus).

○ Sarcinae: Cubic packets of eight cocci.

○ Streptobacilli: Chains of bacilli.

3. Prokaryotic and Eukaryotic Cell Structures and Functions:

● Prokaryotic Cell Structures:

○ Cell membrane: Regulates transport of substances in and out of the cell.

○ Ribosomes: Sites of protein synthesis (smaller in prokaryotes compared to

eukaryotes).

○ Cell wall: Provides structure and protection. Composed of peptidoglycan in most

bacteria.

○ Nucleoid: Region containing the cell’s DNA, no membrane surrounding it.

○ Flagella: Provides motility (when present).

○ Pili: Used for attachment or transfer of genetic material (conjugation).

○ Capsule: Protective outer layer that helps prevent desiccation and aids in evading

the immune system.

● Eukaryotic Cell Structures:

○ Nucleus: Contains the cell’s genetic material (DNA).

○ Mitochondria: Produce energy (ATP) through cellular respiration.

○ Endoplasmic reticulum (ER): Synthesizes proteins (rough ER) and lipids

(smooth ER).

○ Golgi apparatus: Modifies, sorts, and packages proteins and lipids.

○ Ribosomes: Protein synthesis, but larger than prokaryotic ribosomes.

○ Lysosomes: Contain enzymes for digestion.

○ Cytoskeleton: Provides structural support and enables movement.

4. Comparison of Cell Walls in Gram-Positive, Gram-Negative, and Acid-Fast Bacteria:

● Gram-Positive Bacteria:

○ Thick peptidoglycan layer.

○ Contain teichoic acids.

○ Stain purple in the Gram stain.

○ Examples: Staphylococcus, Streptococcus.

● Gram-Negative Bacteria:

○ Thin peptidoglycan layer.

○ Outer lipopolysaccharide (LPS) layer.

○ Stain pink/red in the Gram stain.

○ Examples: Escherichia coli, Pseudomonas.

● Acid-Fast Bacteria:

○ Have a waxy lipid layer (mycolic acid).

○ Do not stain well with Gram stain.

○ Stain red with the acid-fast stain.

○ Example: Mycobacterium (e.g., tuberculosis).

5. O and H Antigens:

● O Antigens: Found on the lipopolysaccharide (LPS) of Gram-negative bacteria, useful

in identifying bacterial strains (e.g., Salmonella).

● H Antigens: Found on the flagella of motile bacteria, used to differentiate strains based

on flagellar proteins.

Clinical Applications: O and H antigens help identify bacterial strains and are important in

diagnosing and tracking infections.

6. Comparison of Simple Diffusion, Facilitated Diffusion, Osmosis, and Active Transport:

● Simple Diffusion: Movement of molecules from high to low concentration, no energy

required.

● Facilitated Diffusion: Movement of molecules across the membrane via a transport

protein, no energy required.

● Osmosis: Diffusion of water across a semi-permeable membrane from an area of low

solute concentration to high solute concentration.

● Active Transport: Movement of molecules against their concentration gradient,

requiring energy (ATP) and a transport protein.

7. Impact on Bacterial Cells in Different Environments:

● Isotonic: Equal concentration of solute inside and outside the cell; no net movement of

water, cell remains stable.

● Hypertonic: Higher solute concentration outside the cell; water leaves the cell, causing it

to shrink (plasmolysis).

● Hypotonic: Lower solute concentration outside the cell; water enters the cell, potentially

causing it to burst (lysis).

● Lysozyme: Enzyme that breaks down the peptidoglycan in bacterial cell walls,

weakening the cell wall and potentially causing the bacteria to burst.

● β-lactam antibiotics (Penicillin): Inhibit cell wall synthesis, leading to weakened cell

walls and potential cell lysis.

8. Properties of Endospores Made by Bacillus and Clostridium Species:

● Endospores are dormant, highly resistant forms of bacteria.

● Formed under harsh conditions (e.g., heat, desiccation).

● Bacillus (e.g., Bacillus anthracis) and Clostridium (e.g., Clostridium tetani) produce

endospores for survival.

Terms

Certainly! Here are definitions for each of the terms you listed:

1. Glycocalyx: A fuzzy-appearing coating around the cell membrane, typically composed of

glycoproteins and glycolipids, that plays a role in protection, immunity, and cell

recognition.

2. Capsule: A well-organized and tightly bound layer of polysaccharides or proteins found

outside the cell wall of some bacteria, providing protection against desiccation and

immune system attacks.

3. Extracellular Polymeric Substance (EPS): A complex mixture of polysaccharides,

proteins, and nucleic acids secreted by cells into their external environment, forming a

protective layer around biofilms.

4. Flagella (Flagellum): Long, whip-like structures that protrude from the cell surface and

are used for locomotion in many prokaryotic and eukaryotic cells.

5. Fimbriae (Fimbria): Short, hair-like projections on the surface of some bacteria that

enable the bacteria to attach to surfaces and to other cells.

6. Pili (Pilus): Thin, protein filaments that allow for conjugation (DNA transfer between

bacteria) and adherence to surfaces; can also play a role in motility.

7. Axial Filaments: Specialized flagella located between the cell membrane and outer

membrane in spirochetes, allowing these bacteria to move in a corkscrew motion.

8. Peptidoglycan: A polymer composed of sugars and amino acids that forms the main

structural component of bacterial cell walls, providing rigidity and shape.

9. Porin Proteins: Channel proteins found in the outer membrane of gram-negative

bacteria, which allow the passage of small molecules like nutrients and waste products.

10. Teichoic Acids: Phosphorylated polyalcohols found in the cell wall of Gram-positive

bacteria, which contribute to the cell wall’s structural integrity and participate in cell

signaling.

11. Wall Teichoic Acids: Teichoic acids that are covalently linked to peptidoglycan in

Gram-positive bacteria, playing a role in cell wall maintenance and function.

12. Lipoteichoic Acids: Teichoic acids that are covalently bonded to lipids and found in the

cell membrane of Gram-positive bacteria, aiding in cell wall regulation.

13. Lipopolysaccharide (LPS): A large molecule found in the outer membrane of

Gram-negative bacteria, composed of lipids and polysaccharides, which plays a key role

in cell membrane stability and immune system recognition.

14. Lipid A: The lipid component of lipopolysaccharides that anchors LPS to the bacterial

outer membrane and is responsible for the endotoxin activity of Gram-negative bacteria.

15. Endotoxin: A toxic component of the outer membrane of Gram-negative bacteria,

primarily Lipid A, which can trigger strong immune responses and cause fever or shock.

16. Core Polysaccharide: The central part of a lipopolysaccharide, which is composed of

sugars and forms a structural component of the outer membrane of Gram-negative

bacteria.

17. O-Antigen: The polysaccharide portion of the lipopolysaccharide in Gram-negative

bacteria that varies between species and is used for serotyping and identification.

18. H-Antigen: An antigen associated with the flagella of bacteria that can vary among

bacterial strains and is used in serotyping for certain bacteria.

19. Lysozyme: An enzyme that breaks down the peptidoglycan in bacterial cell walls,

particularly effective against Gram-positive bacteria.

20. Sterols: Lipid molecules found in the cell membranes of eukaryotes and some

prokaryotes (such as Mycoplasma), which stabilize the membrane structure.

21. Phospholipids: Major components of biological membranes, consisting of a hydrophilic

head and hydrophobic tails that arrange in a bilayer to form the foundation of the cell

membrane.

22. Selective Permeability: The ability of the cell membrane to control what enters and

leaves the cell, allowing some substances to pass while blocking others.

23. Fluid Mosaic Model: A model describing the structure of the cell membrane, where

lipids and proteins float in or on the fluid lipid bilayer like boats on a pond.

24. Passive Processes: Movement of substances across a cell membrane without energy

expenditure by the cell, including diffusion and osmosis.

25. Active Processes: Cellular mechanisms requiring energy (ATP) to move substances

against their concentration gradient, such as active transport.

26. Simple Diffusion: The movement of molecules from an area of higher concentration to

an area of lower concentration without the help of transport proteins.

27. Facilitated Diffusion: The process by which molecules move across a membrane

through a protein channel or carrier, down their concentration gradient, without energy

expenditure.

28. Cilia: Short, hair-like projections on the surface of eukaryotic cells, used for movement

or to move substances across the surface of the cell.

29. Osmosis: The diffusion of water molecules across a semipermeable membrane from an

area of lower solute concentration to an area of higher solute concentration.

30. Isotonic Solution: A solution with the same solute concentration as that inside a cell,

resulting in no net movement of water in or out of the cell.

31. Hypertonic Solution: A solution with a higher solute concentration than that inside a

cell, causing water to leave the cell and potentially leading to cell shrinkage.

32. Hypotonic Solution: A solution with a lower solute concentration than that inside a cell,

causing water to enter the cell and potentially leading to cell swelling or lysis.

33. Osmotic Lysis: The bursting of a cell due to excessive water intake in a hypotonic

solution, resulting in increased internal pressure.

34. Plasmolysis: The process where a plant cell's membrane pulls away from the cell wall

due to water loss in a hypertonic solution, causing the cell to shrink.

35. Active Transport: The movement of substances across a membrane against their

concentration gradient, requiring energy in the form of ATP.

36. Ribosomes: Cellular structures composed of RNA and protein that are responsible for

protein synthesis.

37. Cytoplasm: The jelly-like substance inside the cell, containing organelles, cytosol, and

other components, where most cellular activities occur.

38. Nucleoid: The region within a prokaryotic cell where the genetic material (DNA) is

located, not enclosed by a membrane.

39. Cytoplasmic Membrane: A semi-permeable membrane surrounding the cytoplasm of a

cell, regulating the entry and exit of substances.

40. Plasmids: Small, circular DNA molecules found in bacteria and some other organisms,

often carrying genes for antibiotic resistance.

41. Endospores: Highly resistant, dormant structures formed by certain bacteria to survive

harsh environmental conditions, such as heat and desiccation.

42. Endocytosis: A process by which cells engulf external substances, bringing them into the

cell in vesicles.

43. Phagocytosis: A type of endocytosis in which a cell engulfs large particles, such as

pathogens or dead cells, typically performed by white blood cells.

44. Pinocytosis: A type of endocytosis in which a cell engulfs extracellular fluid and its

dissolved solutes, often referred to as "cell drinking."

45. Receptor-mediated Endocytosis: A process where cells internalize specific molecules

through a receptor-mediated mechanism, usually involving the formation of

clathrin-coated vesicles.

46. Organelle: A membrane-bound structure within a eukaryotic cell that performs specific

functions (e.g., mitochondria, Golgi apparatus, nucleus).

47. Nucleus: The membrane-bound organelle in eukaryotic cells that contains the cell's

genetic material (DNA), controlling cellular activities.

48. Histones: Proteins that help package and organize DNA into a compact, organized

structure known as chromatin, present in eukaryotic cells.

49. Rough Endoplasmic Reticulum: A network of membrane-bound sacs in the cytoplasm

with ribosomes attached to its surface, involved in protein synthesis and processing.

50. Smooth Endoplasmic Reticulum: A network of membranes without ribosomes involved

in lipid synthesis, detoxification, and calcium storage.

51. Golgi Complex: A membrane-bound organelle that modifies, sorts, and packages

proteins and lipids for transport within or outside the cell.

52. Mitochondria (Mitochondrion): Membrane-bound organelles in eukaryotic cells

responsible for producing energy through cellular respiration.

53. Lysosome: A membrane-bound organelle containing enzymes that break down waste

materials and cellular debris.

54. Chloroplasts: Organelles found in plant cells and algae that contain chlorophyll and are

responsible for photosynthesis.

55. Endosymbiotic Theory: The theory that mitochondria and chloroplasts originated as

free-living bacteria that were engulfed by ancestral eukaryotic cells, forming a symbiotic

relationship.