2.1.2 structure of prokaryotic cells and viruses

What are the distinguishing feature of prokaryotic cells

• cytoplasm doesn’t contain membrane bound organelles

• So genetic material is not enclosed in a nucleus

Describe the general structure of prokaryotic cells (always present)

• cell surface membrane

• Cell wall: contains murein (glycoprotein)

• Cytoplasm

• Small ribosomes

• Circular DNA: free in cytoplasm, not associated with proteins

Describe the structure of prokaryotic cells (sometimes present)

• capsule

• Plasmids (small rings of DNA)

• Flagella

Eukaryotic or prokaryotic: membrane bound organelles vs no membrane bound organelles

• eukaryotic = membrane bound organelles

• Prokaryotic = no membrane bound organelles

Eukaryotic or prokaryotic: No nucleus vs nucleus

Eukaryotic = has nucleus

Prokaryotic = no nucleus, DNA is free in cytoplasm

Eukaryotic or prokaryotic: DNA is long+linear+associated with histones vs DNA is short+circular+not associated with histones

Eukaryotic = DNA is long, linear and associated with histones

Prokaryotic = DNA is short, circular and not associated with histones

Eukaryotic or prokaryotic: Larger 80s ribosomes, smaller 70s ribosomes

Eukaryotic = larger 80s ribosomes

Prokaryotic = smaller 70s ribosomes

Eukaryotic or prokaryotic: Cell wall in all cells, contains murein (glycoproteins) vs cell wall only in plant cells, contains cellulose or chitin

Eukaryotic = cell wall only in plant cells, contains cellulose or chitin

Prokaryotic = cell wall in all cells, contains murein (a glycoprotein)

Eukaryotic or prokaryotic: Plasmids/ capsule never present (sometimes flagella) vs plasmids, flagella and a capsule sometime present

Eukaryotic = plasmids/ capsule never present (sometimes flagella)

Prokaryotic = plasmids, flagella and a capsule sometimes present

Eukaryotic or prokaryotic: smaller overall size vs larger overall size

Eukaryotic = larger overall size

Prokaryotic = smaller overall size

Why are viruses described as acellular

As they are not made of cells, no membrane/ cytoplasm/ organelles

Why are viruses described as non-living

As they have no metabolism, so cannot independently move/ respire/ replicated/ excrete

Draw the structure of a virus particle

.

Describe the general structure of a virus particle

1. Nucleic acids surrounded by a capsid (protein coat)

2. Attachment proteins allow attachment to specific host cells

3. No cytoplasm, ribosomes, cell wall or cell surface membrane

4. Some also surrounded by a lipid envelope (e.g HIV)