Structure of prokaryotic cells and of viruses

Question 1

what do prokaryotic cells not contain?

Answer 1

■ do not contain a nucleus or a nuclear envelope
■ do not contain any membrane-bound organelles, such as mitochondria, chloroplasts, endoplasmic reticulum, lysosomes or Golgi apparatus

Question 2

what do prokaryotic cells contain?

Answer 2

■ have a cell wall surrounding the cell-surface membrane, but it is made of a glycoprotein called murein
■ have ribosomes that synthesise proteins, but these are smaller than the ribosomes in eukaryotic cells
■ have a single circular piece of DNA that is not complexed with proteins; this carries the cell’s genetic information

Question 3

in addition what do some prokaryotic cells contain?

Answer 3

■ contain plasmids, which are small, circular pieces of DNA that carry genes
additional to those in the main piece of circular DNA
■ have one or more flagella, that enable the cell to move
■ have a slimy capsule surrounding the cell, which stops the cell drying out, helps to protect the cell from being engulfed by white blood cells, and stores toxins

Question 4

describe the structure and function of a virus? 3 marks

Answer 4

■ Viruses are acellular and non-living
■ Virus particles contain genetic material, surrounded by a capsid
■They have an attachment protein on their surface to help them enter host cells