DNA and cells - PROKARYOTES AND VIRUSES

Question 1

List the features of a generalised bacterial cell

Answer 1

• Flagellum
• Genetic material
• Cytoplasm
• Ribosomes
• Plasmid
• Cell surface membrane
• Cell wall
• Capsule

Question 2

What is the flagellum important for?

Answer 2

Locomotion, or cell movement

Question 3

What is the genetic material?

Answer 3

A large circle of DNA

Question 4

Why is the cytoplasm important?

Answer 4

• Contains enzymes
• Site of cellular reactions
• Where aerobic respiration occurs

Question 5

Compare the ribosomes in eukaryotes vs prokaryotes

Answer 5

• Ribosome in eukaryotes are 80s; in prokaryotes they are slightly smaller, 70s

Question 6

What is the plasmid?

Answer 6

A small, circular piece of DNA

Question 7

What is the slime capsule and why is it important?

Answer 7

• A mucilaginous layer of slime
• Important for cell protection; hides cell markers

Question 8

What is the prokaryotic cell wall made from?

Answer 8

Murein; a glycoprotein

Question 9

Describe the features of a ‘Gram-positive’ bacterial cell wall

Answer 9

• Lipoteichoic acid (lipids)
• Peptidoglycan cell wall; very thick
• Plasma membrane

Question 10

Describe the features of a ‘Gram-negative’ cell wall

Answer 10

• Outer lipid membrane
• Peptidoglycan cell wall
• Plasma membrane

Question 11

Explain why the different colouring occurs in gram negative and gram positive bacteria staining expt?

Answer 11

• Gram positive bacteria; Thick peptidoglycan layer traps dye, staining it purple
• Gram negative bacteria; Dye is first held in the cell wall. Then, the ethanol weakens the membrane hence the dye is lost. Safranin then stains the colourless cells red

Question 12

What other features could be used to help you to identify the specific strain of bacteria you have cultured?

Answer 12

• Cell shape
• Arrangement of cells
• Cocci? Spiral?

Question 13

Suggest other methods of identifying the specific strain of bacteria you have cultured

Answer 13

• Genetic sequencing
• Biochemical testing
• Oxidation reactions

Question 14

What is the name of cell division in prokaryotes?

Answer 14

Binary fission

Question 15

What occurs during binary fission?

Answer 15

• Circular DNA replicates, attaching to cell membrane
• Plasmids replicate
• Cell membrane elongates
• Cytoplasm divides and a new cell wall is formed; 2 identical daughter cells are made

Question 16

Give two ways in which the structure of bacteria is different from the structure of cells lining the alveoli of a human lung (PPQ)

Answer 16

• Bacterium cell has flagellum, whereas the cells lining the alveoli do not
• Bacterium cell has mesosome; a folding of the cell membrane

Question 17

What is a virus?

Answer 17

• Acellular
• Non living

Question 18

Give the 3 main features of a virus

Answer 18

• Genetic material (RNA or DNA)
• Protein capsid
• Lipid envelope

Question 19

Features of a bacteriophage

Answer 19

• Protein coat
• Nucleic acid
• DNA
• Sheath
• Tail fibres

Question 20

Features of influenza

Answer 20

• Protein coat
• Nucleic acid
• RNA
• Lipid membrane envelope

Question 21

Give the steps of virus replication

Answer 21

• Virus injects host cell with its nucleic acid
• Injected host cell replicates the virus particles

Question 22

Steps of virus replication (HIGHER)

Answer 22

• Host cell engulfs virus by endocytosis
• Viral contents are released, entering the nucleus where it is replicated
• Viral mRNA is used to make viral proteins
• New viral particles are made and released