Prokaryotic Cells

Question 1

Cell wall support

Answer 1

Content of bacterial cell are usually hypertonic to medium around them,

Cell wall prevent the cell from bursting and swelling

Maintains the shape of the bacterium and give support and protection of the cell

Bacterial cell wall have layer of peptidoglycan that consists of many parallel polysaccharide chains with short peptide cross-linkage producing an enormous molecule with a net-like structure

Question 2

Pilli

Answer 2

Attachment to a host cell and for sexual reproduction

—> bacteriophage can use pilli as an entry point to the cell

Question 3

Flagella

Answer 3

Moves bacterium by rapid rotation

Question 4

Plasmid

Answer 4

Small circular pieces of DNA that codes for specific aspects of the bacterial phenotype

Plasmid can reproduce themselves independently of the nucleotid - transferred from one bacterium to another in form of sexual reproduction using the pilli

Question 5

Nucleoid

Answer 5

The area in a bacterium containing the single circular loop of coiled DNA - not attached to any histones proteins

Question 6

Cell surface membrane

Answer 6

Mesosomes are inward folds in the plasma membrane

• cellular processes (respiration)
• artifacts produced when the cells are being prepared for viewing with an electron microscope

Question 7

How can bacterial cell walls contains peptidoglycan differentiate between two different types

Answer 7

Gran staining

Question 8

Why is it valuable to differentiate?

Answer 8

Different types of disease-causing bacteria are vulnerable to different types of antibiotics and type of cell wall

Question 9

Properties of gram positive bacteria

Answer 9

• thick layers of peptidoglycocan contains teichoic acid within the net like structure.

Crystal violet/ iodine complex in the gram stain is trapped in the thick peptidoglycan layer resists decolouring when the bacteria are dehydrated using alcohol.

—> bacteria don’t pick up the red safranin counterstain and appear purple/blue when viewed in a light microscope

Question 10

Properties Gram negative bacteria

Answer 10

• thin layer of peptidoglycan with no tie choice acid between the two layers of membranes

Outer membrane is made up of lipopolysaccharides- this layer is dissolved when bacteria are dehydrated in ethanol

Exposes the thin peptidoglycan layers and crystal purple/blue complex is washed out

—> peptiglycocan takes up the red safranin counterstain - cells appear red when viewed in a light microscope

Question 11

Other ways to identify bacteria and why

Answer 11

Gram stains don’t classify different types and by their shapes

Question 12

Shapes of bacteria

Answer 12

Spherical - cocci
Rod-shaped - bacilli
Twisted- spirilla
Comma-shaped - vibrios

Question 13

Other bacteria grouped by

Answer 13

Grouped by respiratory requirements

Obligate aerobes - organism that need oxygen for respiration

Facultative anaerobes - organism that use oxygen if it is available but can respire and survive without it

Obligate anaerobes- organism that can only respire in the absence of oxygen and are killed by oxygen

Question 14

Mitosis

Answer 14

Process which a cell divide to produce two genetically identical daughter

Question 15

Asexual reproduction

Answer 15

The production of genetically identical offspring from a single parents or organism

Question 16

MIRGAS

Answer 16

M - mitosis
R- repair
G- growth
A- asexual reproduction

Question 17

Prokaryotes

Answer 17

No nucleus

Loop of coiled DNA

Non membrane bound organelles

Smaller ribosome (70s )

Respiration cell surface membrane

Peptidoglycan cell wall