Chapter 4: Prokaryotic and Eukaryotic cells

Question 1

Q: What are the structural differences between prokaryotes and eukaryotes?

Answer 1

Prokaryote
• No membrane bound nucleus
• One circular chromosome, not in
a membrane
• No histones
• No organelles
• Bacteria: peptidoglycan cell
walls
• Archaea: pseudomurein cell
walls
• Divides by binary fission

Eukaryote
• Paired chromosomes,
in nuclear membrane
• Histones
• Organelles
• Polysaccharide cell walls, when
present
• Divides by mitosis

Question 2

Q: What are the basic bacterial shapes and arrangements?

Answer 2

A:
* Shapes: Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral), stars, rectangular
Arrangements: Strepto- (chains), Staphylo- (clusters), Diplo- (pairs), Tetrads (groups of four), and Sarcinae(Cubelike groups of 8)

Question 3

Q: What are the prokaryotic structures and their functions?

Answer 3

1. Glycocalyx: Protective outer coating; aids in attachment and prevents dehydration.
   
   2. Flagella: Enables motility.
   3. Cell wall: Provides shape and protects against osmotic pressure.
   4. Fimbriae: Hair-like structures for attachment to surfaces.
   5. Pili: Involved in DNA transfer and motility.
   6. Endospores: Dormant, resistant cells for survival in harsh conditions.
   7. Cytoplasm: Site of metabolic activity.
   8. Nucleoid: Region containing DNA.
   9. Ribosomes: Protein synthesis.
   10. Inclusions: Storage of nutrients or materials.

Question 4

Q: How do Gram-positive and Gram-negative cells differ?

Answer 4

A:
* Gram-positive: Thick peptidoglycan layer, teichoic acids, stains purple.
* Teichoic acids
– Lipoteichoic acid spans peptidoglycan layer and
linked to plasma membrane
– Wall teichoic acid linked to the peptidoglycan
– Carry a negative charge
– Regulate movement of cations
* Polysaccharides and teichoic acids provide antigenic
specificity

*	Gram-negative: Thin peptidoglycan layer, outer membrane with lipopolysaccharides, stains pink.
*	 Periplasm between the outer membrane and the plasma membrane contains peptidoglycan * Outer membrane made of polysaccharides, lipoproteins, and phospholipids Having a Gram (-) outer membrane gives bacteria protection from phagocytes, complement, and a barrier to detergents, antibiotics etc

Question 5

Q: What are the eukaryotic structures and their functions?

Answer 5

1. Plasma membrane: Regulates entry/exit of substances.
   
   2. Cell wall: Provides structure (in plants, fungi).
   3. Glycocalyx: Protection and cell recognition.
   4. Cytoplasm: Site of metabolic reactions.
   5. Ribosomes: Protein synthesis.
   6. Nucleus: Stores DNA.
   7. ER: Protein (rough ER) and lipid (smooth ER) synthesis.
   8. Golgi complex: Modifies, sorts, packages proteins/lipids.
   9. Lysosomes: Digests macromolecules and pathogens.
   10. Vacuoles: Storage and maintaining cell turgor.
   11. Mitochondria: ATP production.
   12. Chloroplasts: Photosynthesis.
   13. Peroxisome: Breaks down fatty acids and hydrogen peroxide.
   14. Centrosome: Organizes microtubules during cell division.

Question 6

Q: What is an endospore, and why does it form?

Answer 6

A: An endospore is a dormant, tough, and non-reproductive structure that forms to ensure survival in harsh conditions.