k) the similarities and differences in the structure and ultrastructure of prokaryotic and eukaryotic cells.

How do prokaryotic cells differ from eukaryotic cells in size?

• Prokaryotic cells: extremely small, <2 µm diameter
• Eukaryotic cells: larger, 10–100 µm diameter

How does the DNA structure differ between prokaryotes and eukaryotes?

• Prokaryotic DNA: circular, loops back on itself forming a ring
• Eukaryotic DNA: linear, with two distinct ends
• Tip: Linear DNA has two ends; circular DNA forms a complete ring

Do prokaryotes and eukaryotes have a nucleus?

• Prokaryotes: no nucleus, DNA free in cytoplasm
• Eukaryotes: nucleus present, DNA inside

How do cell walls differ in prokaryotes and eukaryotes?

• Prokaryotes: cell wall made of polysaccharide, not cellulose or chitin
• Eukaryotes: animals → no cell wall, plants → cellulose, fungi → chitin

How do organelles differ between prokaryotes and eukaryotes?

• Prokaryotes: few organelles, no membrane-bound organelles (e.g., no mitochondria)
• Eukaryotes: many organelles including mitochondria and others

How do flagella differ in prokaryotes vs eukaryotes?

• Prokaryotes: flagella made of protein flagellin, arranged in a helix
• Eukaryotes: flagella made of microtubules in 9+2 arrangement
• Tip: Flagella aren’t always present in prokaryotic cells

How do ribosomes differ between prokaryotes and eukaryotes?

• Prokaryotes: small ribosomes, 20 nm or less
• Eukaryotes: larger ribosomes, over 20 nm

Give examples of prokaryotic and eukaryotic cells.

• Prokaryotes: E. coli, Salmonella
• Eukaryotes: human liver cell, yeast, amoeba

What is a micrometre (µm)?

• One millionth of a metre
• 0.001 mm

Are prokaryotes single-celled or multicellular?

• Always single-celled
• Eukaryotes can be single-celled or multicellular
• Tip: Prokaryotes = always single-celled; eukaryotes = single or multicellular

Why can’t normal light microscopes easily see the internal structure of prokaryotes?

• Prokaryotes are roughly a tenth the size of eukaryotic cells → too small for light microscope resolution

What is shown in a bacterial cell under an electron microscope?

• Cell wall
• DNA (bacterial chromosome)
• Ribosomes
• Plasma (cell surface) membrane
• Flagellum (tail for propulsion)
• Plasmid (ring of DNA)
• Tip: Flagella and plasmids aren’t always present in prokaryotic cells