Cell as basic unit of life lesson 2 : lectures 3 and 4

Question 1

describe the structure of the bacterial cell.

Answer 1

is a type of prokaryotic cell.

1-10 micrometers

has primative nucleus that has no nuclear membrane (nucleiod)

no membrane bound cell organelles . instead they have plasma membrane mesosome

DNA is not associated with histone proteins

Question 2

if bacterial cells dont have any membrane bound organelles then how do the cell functions get carried out ?

Answer 2

bacterial cells have plasma membrane mesosomes that carry out cell functions

Question 3

describe the outer covering of the bacteria

Answer 3

o=composed of 3 main coverings 
-capsule 
-cell wall 
-plasma membrane 
(in that order from superficial to deep)

Question 4

inside the outer layer of bacteria we can see—-

Answer 4

cytoplasm and its constituents

Question 5

describe the structure and function of the capsule /

Answer 5

most bacteria have capsules .
it is composed of poly saccharide

the main function is a protective function

bacteria with capsule are more resistant than bacteria without capsule

Question 6

describe the structure and function of cell wall .

Answer 6

it is composed of lipids , proteins , and poly saccharides (capsule is only made out of poly saccharide)

it gives a firm and rigid shape to the bacteria cell. it is also important for protection

bacteria cannot survive without cell wall.

Question 7

what bacterial structure is used in gram staining ?

Answer 7

cell wall

Question 8

what type of stain is used in gram staining ?

Answer 8

crystal violet stain and iodine (which helps staining of violet)

Question 9

explain the process of gram staining .

Answer 9

bacteria are stained by crystal violet stain and iodine , which helps the staining of violet . it is then left for 2 minutes before ethyl alcohol is added . finally a counter stain (safarnin) is added ). if the bacteria succeeded in retaining violet color of crystal violet stain then it will be gram positive. if it was only stained by the safarnin and has a pinkish color then it is gram negative

Question 10

how are gram negative and gram positive bacteria different

Answer 10

if the bacteria succeeded in retaining violet color of crystal violet stain then it will be gram positive. if it was only stained by the safarnin and has a pinkish color then it is gram negative .

Question 11

how are the cell walls of gram positive and gram negative bacteria different?

Answer 11

gram positive bacteria cell walls have an excess of peptidoglycan on the surface . peptidoglycan is responsible for retaining the crystal violet stain . in gram negative peptidoglycan is alot less and is sandwiched between 2 layers lipopolysaccharide

Question 12

which type of bacteria is more toxic and more resistant to humans ?

Answer 12

gram negative

Question 13

what is the 3rd layer of the outer covering of bacteria and whats it formed of ?

Answer 13

plasma membrane and it is composed of lipoprotein

Question 14

describe the cytoplasm in bacteria

Answer 14

it is a dense jelly like structure

Question 15

what granules does the cytoplasm contain ?

Answer 15

glycogen , proteins , fats , and some polymers of glucose

Question 16

what type of ribosomes are present in bacterial cytoplasm?

Answer 16

70S ribosomes

Question 17

what does spedbergs unit of ribosomes mean?

Answer 17

it is the sedimentation rate (weight) and it is not accumulative

Question 18

bacteria contain more rna than eukaryotic

Answer 18

.

Question 19

what is the nuclear region ?

Answer 19

area where DNA floats around in cytopalsm (nucleuoid)

Question 20

what other type of DNA do bacteria have other than linear DNA?

Answer 20

plasmids which are circular DNA and it is responsible for antibiotic resistance .

Question 21

what is plasmid used for in labs ?

Answer 21

it is taken outside , interested part of DNA that we want to study is inserted into it , and the plasmid is insertedinto animal or human cell and the effects are studied.

Question 22

what is flagella made of ?

Answer 22

flagellin protein

Question 23

what is pilli made of ?

Answer 23

pillin protein

Question 24

what is the main structure of the cell wall?

Answer 24

peptidoglycan

Question 25

how does penicillin antibiotic work?

Answer 25

by destroying enzyme responsible for peptidoglycan crosslinking ( DD-transpeptidase ) disabling it from crosslinking and forming the cell wall ,causing the bacteria to die.

Question 26

what enzyme helps with peptidoglycan crosslinking in bacterial cell wall?

Answer 26

DD-transpeptidase / penicellin binding protein

Question 27

what type of bacteria is penecillin most active against?

Answer 27

gram positive bacteria

Question 28

why is the cell wall essential to the cells survival ?

Answer 28

because without it the bacteria is vulnerable to outside water and molecular pressure

Question 29

why is penicillin effective against gram positive but not gram negative bacteria ?

Answer 29

because gram positive has alot of peptidoglycan and breaking all of it down will destroy the cells defence . gram negative bacteria on the other hand dont have as much peptidoglycan and its cell walls are surrounded by a lipopolysaccharide layer that prevents antibiotic entry