Week 3: Biology of Cells 4: Introduction to Microbiology & Bacterial Cell Structure

Eukaryote (Animal) chromosomes, cell wall, size, organelles, ribosomes and nucleus:

Multiple Linear Chromosomes, No Cell Wall, Larger, Has Nucleus, and 80S Ribosomes

Eukaryote (Plants) chromosomes, cell wall, size, organelles, ribosomes and nucleus:

Multiple Linear chromosomes, Present cell wall, Larger, 80S Ribosomes and Has Nucleus.

Prokaryote (Bacterial Cells)

Single Circular Chromosomes, Has cell wall, Smaller, 70S Ribosomes and no nucleus.

Viruses, bacteria and eukaryotes by size, from the smallest to largest:

Bacteria, Virus, Eukaryotes

Four ways bacteria can be classified into species.

Visible Properties, Physiological Properties, Characteristic Surface Macromolecules, Temperature Requirements

Gram negative (G-ve) bacteria Colour

Red

Gram positive (G+ve) bacteria Colour

Blue

Visible Properties for classifying bacteria:

Size, Shape, Staining

Physiological Factors for bacteria classification:

Metabolic end-products and Nutrition

Streptococci Bacteria Shape:

Spherical

Streptococcus:

Chain of cocci

Staphylococcus:

Cluster of cocci

Bacilli Bacteria Shape:

Cylindrical

Bacillus:

Single Rod

Streptobacillus:

Chain of Rods

What is a capsule and give one advantage it provides to bacteria

Polysaccharide produced outside cell wall. Acts as a protective immunity layer.

Slime Layer:

Loosely Packed Capsule.

What structure allows certain bacteria to move towards nutrients or favourable environmental conditions?

Flagellae allows for co-ordinated motion.

Fimbrae (pili) are involved in what two processes:

Surface Attachment and transferring DNA to female cells, allowing for genetic population variation.

What is the main function of the rigid cell wall found in bacteria:

Acts as an extremely strong structure providing cell strength, and allowing for cell division and attachment.

What are the differences (peptidoglycan and structure) in the cell walls between G+ve and G-ve bacteria:

G+ve Bacteria has a thicker peptidoglycan layer while G-ve Bacteria has a thinner peptidoglycan layer and an outer membrane.

Describe the structure of peptidoglycan and how antibiotics such as penicillin target its structure:

Peptidoglycan is a structural polysaccharide that forms bacterial cell walls. It is made up of glycosaminoglycans linked by peptide bonds. Penicillin targets enzymes which make peptide bridges in the cell wall. If broken, cell wall will swell and burst in hypotonic solutions.

What are teichoic acids and what type of bacteria (G+ve or G-ve) contains them?

Teichoic acids are linear polymers of either glycerol or ribitol. It is attached to the NAM (a sugar derivative) of peptidoglycan. Only G+ve bacteria have these acids.

Two main components of lipopolysaccharide. What bacteria (G+ve or G-ve) contains LPS?

Complex Lipid A and Polysaccharides. Only G-ve bacteria contain LPS.

What role do granules play in bacterial cells?

Granules act as a cellular storage for materials such as carbohydrates.

Describe in general what an endospore is and what advantage it provides:

Endospore is a Tough structure produced by bacteria to be resistant to heat, dryness and chemical agents.

Why are penicillin antibiotics more effective against Gram positive bacteria in general?

G+ve bacteria have a thicker peptidoglycan wall which isn’t covered by a cell wall, making it more accessible for penicillin antibiotics.