Prokaryotic cells and virus structure

Give the function of capsule in prokaryotes.

It prevents desiccation(loss of water) and protects cell from antibiotics and viruses.

Give the function of ribosomes in prokaryotes.

They are smaller than eukaryotic ones, they produce proteins.

How is DNA structured In prokaryotes?

It is in a single circular loop, not associated with proteins - no nucleus and doesn’t form chromosomes.

What are plasmids in prokaryotes?

They are smaller loops of DNA which can be shared between cells usually they contain useful genes, e.g. antibiotic resistance.

What are cell walls made of in prokaryotes?

They are made of murein, a polysaccharide and peptide mix (glycoprotein).

What is flagellum used for in prokaryotes?

It is used for locomotion, helps them with movement.

What are the membrane infolds in prokaryotes?

They are called mesosome, it increases the surface area for respiration or photosynthesis to take place.

What is the cell division in prokaryotes?

Binary fission, this cell division does not produce genetically identical cells to parent cell.

What are the 4 steps of binary fission?

Step 1: DNA and plasmids replicate. Plasmids can be replicated many times.

Step 2: Cell elongates and DNA moves to opposite poles of cell.

Step 3: Cytoplasm begins to divide and new cell walls begin to form.

Step 4: Cytoplasm divides to produce two daughter cells. Each contain an identical DNA loop but can contain different number of plasmid copies.

What are features of viruses?

• Viruses are neither prokaryotic or eukaryotic.

• They are acellular non-living particles.

• They are 1000x smaller than bacteria.

• They consist of RNA that are protected by a protein coat called capsid. May also be enclosed in lipid envelope. Capsid or lipid envelope will have attachment proteins/antigens to help recognise a host.

What do viruses not contain?

They have no ribosomes and no cytoplasm. They are not considered real cells.

What acronym classifies something as living?

MRS GREN.

What does the acronym “MRS GREN” stand for?

M- movement G- growing

R- reproduce R- respiration

S- sensitivity E- excretion

N- nutrition

What enzyme can viruses contain?

Reverse transcriptase. It converts the RNA genome carried in the retrovirus into DNA that can integrate into its host's genome.

How does virus replication work?

Viruses require the aid of a living cell to reproduce.

Step 1: virus detects host cell by recognising protein marker on membrane, virus attaches to cell using attachment proteins. Step 2: virus injects genetic material into the cell. Step 3: cell reproduces the genetic material and reads it creating new viral proteins. Step 4: virus leaves cell using some of the cells own membrane to form itself.

How large are bacteria cells?

1-5 micrometers

How large are virus cells?

If they are 1000x smaller, they are 1-5nm.