1 - Cell biology

Question 1

Prokaryotic Cells

Answer 1

• developed 3.5 billion years ago.
• do not have a membrane bound nucleus
• most abundant type on earth today
• simple in structure but biochemically diverse
• Eukaryotic cells developed from prokaryotic cells around 2 billion years ago (maybe earlier) and have a membrane bound nucleus

Question 2

2 domains of prokaryotes

Answer 2

Bacteria + Archaea
• Archaea often live in very extreme environments
• Bacteria have enormous medical and economic importance.

Question 3

Nucleoid region

Answer 3

contains circular DNA, no nuclear membrane

Question 4

What do prokaryotes have instead of a nucleus ?

Answer 4

A nucleoid region which containing circular DNA and also have loops of DNA named plasmids

Question 5

What are the main 3 shapes and their classified names?

Answer 5

Spherical - cocci

Rod shaped - bacilli

Helical - Spirochetes

Question 6

What are flagella and what are they composed of?

Answer 6

Projections which aid the movement of the bacteria, made of the protein flagellin.

Question 7

What are pili and what are they composed of?

Answer 7

Projections which help bacteria stick to their substrate, made of the protein pilin.

Question 8

What is the capsule secreted by bacteria made up of?

Answer 8

polysaccharides

Question 9

Do prokaryotes have a cell wall or a cell membrane?

Answer 9

They have a cell membrane known as the plasma membrane or the cytoplasmic membrane.
They also have a cell wall, usually composed of peptidoglycan or murein.

Question 10

What is the function of the prokaryote cell wall in bacteria?

Answer 10

The cell wall protects the bacterial cell from mechanical and osmotic shocks

Question 11

How are bacteria classified based on their cell wall? (e.g. what are the 2 types and their cell wall structure?)

Answer 11

Bacteria can be Gram positive or Gram-negative.
Gram-positive bacteria have a thick 40nm layer of peptidoglycan in their cell wall.
Gram-negative have a thin cell wall with a much more complex structure

Question 12

Which type of bacteria are more dangerous to humans , gram positive or gram negative?

Answer 12

Gram negative - they are also harder to kill

Question 13

How is bacteria useful in biotechnology? Use examples

Answer 13

Bacteria can be used to produce large quantities of proteins relatively cheaply.
For example, insulin for diabetic patients is now produced using bacteria instead of taking it from dead animals.

Question 14

What modes of nutrition exist amongst prokaryotes?

Answer 14

photoautotrophs
chemoautotrophs
photoheterotrophs
chemoheterotrophs

Question 15

Photoautotrophs

Answer 15

Photosynthetic organisms which use light to synthesize organic compounds from Carbon Dioxide

Question 16

Chemoautotrophs

Answer 16

Use carbon dioxide as a carbon source and obtain their energy by oxidizing inorganic substances
e.g. from hydrogen sulphide, ferrous ions e.g. Sulpobolus oxidise sulphur.
This mode of nutrition is unique to certain prokaryotes

Question 17

Photoheterotrophs

Answer 17

Use light to generate ATP but must obtain their carbon in an organic form. This type of nutrition is unique to certain prokaryotes

Question 18

Chemoheterotrophs

Answer 18

Use organic molecules to supply both carbon and energy

Question 19

Why are viruses not considered to be alive?

Answer 19

They cannot self repair and do not have an energy transduction system.

Question 20

Why were viruses only discovered relatively recently?

Answer 20

They are only visible with an electron microscope

Question 21

4 groups viruses can be classified into

Answer 21

Filamentous
Spheroid
Tailed spheroid
Enveloped

Question 22

Filamentous viruses

Answer 22

The nucleic acid is arranged in a helix , with the protein sub-units surrounding and stabilizing it. An example is Tobacco mosaic virus

Question 23

Spheroid viruses

Answer 23

The nucleic acid is condensed inside a protein envelope which is usually
organized into a multisided geometric shape.
An example are adenovirus different types cause illness ranging from Gastroenteritis to keratoconjunctivitis.

Question 24

Tailed spheroid virus

Answer 24

This is basically a spheroid virus with a tail. An example is the lambda phage

Question 25

Enveloped viruses

Answer 25

Have lipid envelopes includes the influenza and coronaviruses viruses

Question 26

Examples of pathogenic gram negative bacteria

Answer 26

• Chlamydia trachomatis
• Vibrio cholerae (cholera)
• Yersinia pestis (plague)

Question 27

Examples of pathogenic gram positive bacteria

Answer 27

• Clostridium botulinum (botulism)

- Streptococcus pneumoniae (pneumonia)

Question 28

How are flagellum powered?

Answer 28

A motor in the plasma membrane which powers a hook which causes movement.

Question 29

Which domains of life has a circular chromosome present?

Answer 29

Bacteria and archaea

Question 30

Which domains of life has histones present?

Answer 30

Archaea and Eukarya

Question 31

What is each domain of life’s response to antibiotics, streptomycin and chloramphenicol?

Answer 31

bacteria = growth inhibited

Archaea and Eukarya = growth not inhibited

Question 32

Are introns present or absent in which domains of life?

Answer 32

Absent = bacteria
Present in some genes = archaea
Present = Eukarya

Question 33

Which initiator amino acid does each domain of life have?

Answer 33

Methionine= archaea and eukarya
Formyl-methionine = bacteria

Question 34

Which hydrocarbons are present in which domains of life?

Answer 34

Unbranched = bacteria and eukarya

Some branched = archaea

Question 35

Which domain of life only have one kind of RNA polymerase?

Answer 35

Bacteria