Lecture 4 (Prokaryotes)

Question 1

What is the total number of bacterial cells on earth?

Answer 1

5X10^30

Question 2

How many forms of bacteria life are there?

Answer 2

10^-19

Question 3

What is the bacteria’s cell wall made of ?

Answer 3

Peptidoglycan

Question 4

What is the function of the bacteria’s cell wall?

Answer 4

1. To provide a rigid macromolecular layer that provides strength to the cell
2. Prevents osmotic lysis
3. Confers the cell shape

Question 5

What is the structure of peptidoglycan like?

Answer 5

Large mesh-like structure

Question 6

What are the key components of peptidoglycan?

Answer 6

Carbohydrate backbone
Peptide cross bridges
Peptide side chains

Question 7

How are the peptide side chains joined together?

Answer 7

Transpeptidase catalyses these the formation of the cross bridges.

Question 8

Structure of a Gram-Positive bacteria cell wall

Answer 8

Thick peptidoglycan layer

1 layer of plasma membrane

Question 9

Structure of a Gram-Negative bacteria cell wall

Answer 9

Outer plasma membrane
Thin layer of peptidoglycan
Inner plasma membrane

Question 10

What are the initial steps in identifying Gram-Positive Gram-Negative bacteria?

Answer 10

Add crystal violet to each of the cell walls

Then add alcohol to remove the crystal violet.

Question 11

Which type bacteria should have the crystal violet left over?

Answer 11

Gram-Positive

Question 12

Function of the Flagella

Answer 12

To enable the cell to move through a liquid medium

Question 13

What do flagella look like?

Answer 13

Long flexible hair-like structures

Question 14

What are the three major sections of the flagella structure?

Answer 14

Long Filament
Hook
Basal Body

Question 15

What are the respective functions of each major sections of the flagella?

Answer 15

Long Filament - the propeller
Hook - Curved section connecting the filament to the cell surface
Basal body - anchoring the flagellum by plates or rings

Question 16

What is the tactic response shown by bacteria?

Answer 16

Chemotaxis

Question 17

Definition of chemotaxis

Answer 17

Where bacteria move along a concentration gradient either towards or away a chemical attractant.

Question 18

What will CCW rotation of the flagellum cause and the position of the flagellum?

Answer 18

Running and Swimming, Bundled flagella

Question 19

What will CW rotation of the flagellum cause and the position of the flagellum?

Answer 19

Tumbling, Flagella is pushed apart.

Question 20

How do bacteria sense changes in concentration?

Answer 20

Temporal gradients

Question 21

What are temporal gradients

Answer 21

Varying concentrations in different locations over time with chemoreceptors.

Question 22

Why can’t they sense the location of the chemical attractant?

Answer 22

They are too small to sense spatial gradients

Question 23

Function of Fimbriae

Answer 23

Structures with adhesive properties that can cause them to stick to surfaces

Question 24

Why do not all bacteria possess Fimbriae?

Answer 24

Because it is an inherited trait

Question 25

What are some substructures on the Fimbriae? What do they do?

Answer 25

Adhesins - the binding bit of the fimbriae to specific cell receptors Fimbrins - protein subunits that form the pore down the centre.

Question 26

What are capsules and slime layers made from?

Answer 26

Glycocalyx

Question 27

What is the structure of Glycocalyx in Capsules?

Answer 27

Defined, attached firmly to the cell wall

Question 28

What is the structure of Glycocalyx in Slime layers?

Answer 28

Disorganised, attached loosely to the cell wall

Question 29

Functions of Capsules/Slime layers

Answer 29

1. Protects cells from being engulfed 2. Helps with bacteria's adhesion properties 3. Provides a layer of nutrients 4. Prevents cell from drying out

Question 30

What are bacteria endospores?

Answer 30

Highly differentiated cells that are resistant to harsh conditions which lay dormant.

Question 31

Why are bacterial endospores forms?

Answer 31

They are formed under unfavourable growth conditions, protects cells form stress.

Question 32

Types fo bacterial endospores?

Answer 32

Terminal Subterminal Central

Question 33

What are the different layers of a bacteria endospore? (From superficial to deep)

Answer 33

``` Exosporium Spore Coat Core Wall Cortex DNA ```

Question 34

Properties of endospores

Answer 34

Heat and Radiation resistant Water content is low High in Ca2+ Dormant