2.1.2 Structure of prokaryotic cells and of viruses

What are the distinguishing features of prokaryotic cells?

cytoplasm lacking membrane-bound organelles so genetic material not enclosed in a nucleus.

Describe the general structure of prokaryotic cells. (always present)

Cell wall containing murein , a glycoprotein
Cell-surface membrane
cytoplasm
small ribosomes
circular DNA - free in cytoplasm, not associated with proteins

Describe the general structure of prokaryotic cells. (sometimes present)

Capsule, plasmids, flagella

Are eukaryotic cells larger or smaller than prokaryotic cells overall?

Larger

Does a prokaryotic cell have a nucleus?

No - DNA is free in cytoplasm

Features of DNA in eukaryotic cells

DNA is long and linear - associated with histone proteins

Features of DNA in prokaryotic cells

DNA is short and circular - not associated with proteins

Why are viruses described as acelluar non-living?

Acellular - not made of cells, no cell membrane/ cytoplasm/ organelles
Non-living - have no metabolism, cant independently move/ respire/ replicate/ excrete

Describe the general structure of a virus particle

Nucleic acids surrounded by a capsid (protein coat)
Attachment proteins allow attachment to specific host cells
Some are surrounded by a lipid envelope e.g. HIV
No cytoplasm/ other organelles