A complete comprehensive details of functions and functional anatomy of prokaryotic cells and eukaryotic cells according to microbiology, biotechnology and pharmacy medicine

1. Functional Anatomy of
Prokaryotic and Eukaryotic Cells

2. Structures Internal to the Cell Wall
The Plasma (Cytoplasmic) Membrane:
– Thin structure inside of cell wall that surrounds the cytoplasm
– Phospholipid bilayer with proteins (Fluid mosaic model)
• Integral membrane proteins: Penetrate membrane completely
• Peripheral membrane proteins: On inner or outer membrane surface
– Lack sterols and are less rigid than eukaryotic membranes.
• Exception: Mycoplasmas

3. Plasma Membrane

4. Functions of the Plasma Membrane
• Selective barrier to regulate passage of materials in & out of cell
– Impermeable to large proteins, ions, and most polar molecules
– Permeable to H2O, O2, CO2, simple sugars, & small nonpolar substances
• Nutrient breakdown and energy (ATP) production:
– Site of cellular respiration
• Synthesis of cell wall components
• Assists with DNA replication
• Site of photosynthesis:
– Photosynthetic bacteria have membrane extensions called thylakoids,
where photosynthesis occurs
• Contains basal bodies of flagella
• Responds to chemical substances in environment

5. Destruction of the Plasma Membrane
• Several antimicrobial agents damage the integrity of
the plasma membrane.
• They commonly cause leakage of intracellular
contents and cell death:
1. Alcohols
2. Quaternary ammonium compounds
3. Antibiotics (Polymyxins)

6. Movement of Materials Across Membranes
• Can either be a passive or an active process
• Passive Transport Processes:
– Substances move spontaneously from an area of
high concentration to one of low concentration.
– Do not require energy expenditure (ATP) by the cell.
– Include the following processes:
• Simple diffusion
• Facilitated Diffusion
• Osmosis

7. Simple Diffusion
• Net movement of molecules or ions from an area of
high concentration to one of low concentration.
• Equilibrium: Net movement stops when molecules
are evenly distributed.
• Used by cells to transport small molecules (oxygen,
carbon dioxide) across their membranes.
• Example:
– Diffusion of perfume into the air after the bottle is opened.

8. Facilitated diffusion
• Net movement of molecules or ions
from an area of high concentration to
one of low concentration.
• Substance to be transported combines
with a carrier protein in plasma
membrane.
• Extracellular enzymes may be used to
break down large substances before
they can be moved into the cell by
facilitated diffusion.

9. Osmosis
• Net movement of water (solvent)
molecules across a semipermeable
membrane from an area of high
conc. to one of low conc. of water.
• Osmotic Pressure: Pressure
required to prevent the movement
of pure water into a solution.

10. Osmosis (Cont.)
Bacterial cells can be subjected to three different types of osmotic solutions:
– Isotonic: Concentration of solutes (and water) are equal on both sides of a
cell membrane (e.g.: 0.9% NaCl, 5% glucose)
• Result: No net movement of water into or out of the cell
– Hypotonic: Solute concentration is lower outside the cell (e.g.: pure water)
• Result: Net movement of water into the cell
• Most bacteria live in hypotonic environments. Cell wall protects them from lysis.
– Hypertonic: Solute concentration is higher outside the cell
• Result: Net movement of water out of the cell

11. Osmosis (Cont.)

12. Active Processes
• Substances are moved from an area of low conc. to high conc.
• Require energy expenditure (ATP) by the cell.
• Active transport:
– Requires carrier proteins or pumps in plasma membrane.
• Group translocation:
– Like active transport, but substance transported is chemically altered during process.
– After modification, the substance cannot leave the cell.
– Glucose is phosphorylated during group translocation in bacterial cells.
– Note: Endocytosis (phagocytosis, pinocytosis, etc.) does not occur in prokaryotes.

13. Structures Internal to the Cell Wall: (Cytoplasm)
• Substance inside the cell membrane.
– Thick, aqueous, semitransparent, and elastic
• The major structures in the cytoplasm of prokaryotes
– nucleoid (containing DNA)
– ribosomes
– reserve deposits called inclusions
• Contains:
– 80% water
– Proteins, carbohydrates, lipids
– Inorganic ions and low molecular weight compounds
• Lacks a cytoskeleton and cytoplasmic streaming

14. Structures Internal to the Cell Wall: (Cont.)
The Nuclear Area (Nucleoid):
• Contains a single chromosome, a long circular molecule
of double stranded DNA.
• The chromosome is attached to the plasma membrane.
• May occupy up to 20% of the intracellular volume.
• Plasmids:
• Small, circular, double stranded DNA molecules.
• Found in many bacterial cells in addition to
chromosomal DNA.
• May contain from 5 to 100 genes that are usually not
essential for survival.
• Antibiotic resistance genes and toxins

15. Structures Internal to the Cell Wall: (Cont.)
Ribosomes:
• The site of protein synthesis (translation).
• Found in all eukaryotic and prokaryotic cells.
• Made up of protein and ribosomal RNA (rRNA).
• Prokaryotic ribosomes (70S) are smaller and less
dense than eukaryotic ribosomes (80S).
• Prokaryotic ribosomes have two subunits:
– Small subunit: 30S
– Large subunit: 50S
• Several antibiotics work by inhibiting protein
synthesis by prokaryotic ribosomes, without
affecting eukaryotic ribosomes.

16. INCLUSIONS
• Reserve deposits in the cytoplasm of cells.
• Not found in all cell types:
1. Metachromatic Granules:
• Contain inorganic phosphate that can be used in the
synthesis of ATP.
• Found in bacteria, algae, protozoa, & fungi.
• Characteristic of Corynebacterium diphtheriae,
causative agent of diphtheria.
• Useful for identification purposes.
2. Polysaccharide Granules:
• Contain glycogen and starch.
• Stain blue or reddish brown with iodine.
3. Lipid Inclusions:
• Contain lipids, detected with fat soluble dyes.

17. INCLUSIONS
4. Sulfur Granules:
• Contain sulfur and sulfur containing compounds.
• “Sulfur bacteria” (Thiobacillus) obtain energy by oxidizing sulfur and its compounds.
5. Carboxysomes:
• Contain enzyme ribulose 1,5-diphosphate carboxylase, necessary for carbon
fixation during photosynthesis.
• Found in nitrifying bacteria, cyanobacteria, and Thiobacilli.
6. Gas Vacuoles:
• Hollow cavities found in many aquatic bacteria.
• Contain individual gas vesicles, hollow cylinders covered by protein.
• Used to regulate buoyancy so cells can remain at appropriate water depth.
7. Magnetosomes:
• Contain iron oxide (Fe2O3), which acts like a magnet.
• Formed by several aquatic Gram-negative bacteria.
• Enable bacteria to respond to magnetic fields (magnetotaxis).

18. Bacterial Spore
• A special resistant dormant structure
• Some Gram-positive can form endospores
• Clostridium and Bacillus
• Develop when essential nutrient are depleted
• Sporulation: Vegetative cell to endospore
– Each vegetative cell forms only one spore
• Germination: Endospore to vegetative cell
– Each endospore give rise to one vegetative cell
• Sporulation: Method of Reproduction or Preservation?

19. Sporulation or Sporogenesis
• Commences when growth ceases due to:
– Lack of nutrients
– Depletion of nitrogen or carbon source or both
• Spore septum:
– Newly replicated bacterial chromosome and a small portion
of cytoplasm are isolated by an ingrowth of cell membrane
• Forespore:
– The spore septum becomes a double-layered membrane
– Structure, entirely enclosed within the original cell
• Spore coat:
– The two spore membranes now engage in active synthesis of
various layers of the spore.
– The inner layer becomes the inner membrane
– Between the two layers is laid spore cortex
– Outer layer is transformed into spore coat
– In some species Exosporium
• Free endospore: Finally exosporium disintegrates
and the endospore is freed.

20. Components of Endospore
• Core:
– Spore protoplast
– Have normal cell structures but metabolically inactive
• Spore Wall:
– Inner most layer around core
– Have PDG and become CW during germination
• Cortex:
– Thickest layer of the spore envelope
– Cortex peptidoglycan is extremely sensitive to lysozyme
– Its autolysins plays a role in spore germination
• Spore coat:
– Cortex, in turn, is enclosed by fairly thick spore coat.
• Exosporium:
– Spores of some species have an additional,
– Loose covering known as the exosporium
– May have distinctive ridges and grooves

21. Spore Germination and Spore Types
Germination:
• Process of conversion of a spore into vegetative cell under suitable conditions
• Three Stages:
– Activation, initiation and outgrowth
• Size and Position of Spore:
– Spores may be central (equatorial)
– Subterminal (close to one end)
– Terminal
• The appearance
– Spherical, ovoid or elongated
– Bulging or non-bulging
• One of the most resistant forms of life
– Can remain viable for centuries
• Uses:
– Practical importance, Sterilization control, research