Lesson 6.2.1

6.2.1 Structure of bacteria and viruses compared Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.2.1, Structure of bacteria and viruses compared: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 6: Immunity, Infection and Forensics, written with Revision Ninja.

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The 20 questions

  1. Which feature is present in bacteria but absent from viruses?

    • An outer envelope containing glycoproteins that help the particle attach to host cells
    • A cytoplasm surrounded by a cell membrane, with ribosomes that synthesise proteins
    • A nucleic acid genome that carries the instructions for making new virus particles
    • A protein capsid that encloses the genetic material in a regular shape

  2. Bacterial DNA is typically described as:

    • A single circular chromosome, not enclosed in a nuclear envelope, often with small plasmids
    • Single-stranded RNA that is found free in the capsid without any associated proteins
    • Multiple linear chromosomes enclosed within a double membrane in the nucleus
    • A double-stranded linear chromosome bound to histone proteins inside a nucleolus

  3. The cell wall of most bacteria is made of:

    • Chitin, a polymer of nitrogen-containing sugars that forms the walls of fungal cells
    • Cellulose, a polymer of glucose that is found in the walls of plant and fungal cells
    • Peptidoglycan, a polymer of sugars and amino acids that is not found in viruses or in plant cell walls
    • Lipopolysaccharide only, a lipid-sugar mixture that forms the surface of every human cell

  4. Which best describes the size of a typical bacterium compared with a typical virus?

    • A bacterium is typically around 1 millimetre, which is about 1,000 times larger than a virus
    • A bacterium is typically around 1 to 5 micrometres
    • A bacterium is typically around 20 to 300 nanometres, which is the same size as a virus
    • A bacterium and a virus are both typically around 10 nanometres and cannot be told apart by size

  5. A viral particle is best described as having:

    • A nucleic acid genome enclosed in a protein capsid
    • A cell wall of peptidoglycan that protects the genetic material from damage
    • A cell membrane, a cytoplasm and a nucleus containing linear chromosomes
    • Ribosomes and mitochondria, which allow the particle to make its own energy

  6. Where are viruses able to replicate?

    • They can replicate independently in soil and water using their own ribosomes
    • They carry out aerobic respiration in their own mitochondria to release energy
    • They can only replicate inside a living host cell, using its ribosomes and enzymes
    • They divide by binary fission, which produces two identical virus particles

  7. Which structure in bacteria is the site of protein synthesis?

    • The nucleus, which contains the bacterial chromosome and controls protein synthesis
    • Chloroplasts, which carry out photosynthesis in the cytoplasm of bacteria
    • Mitochondria, which are the sites of aerobic respiration in bacterial cells
    • Ribosomes, which are smaller 70S ribosomes in the cytoplasm

  8. Which feature is found in some viruses but not bacteria, and helps them attach to host cells?

    • A peptidoglycan cell wall that binds to the surface of the host cell through sugar chains
    • A flagellum that rotates to propel the virus through the blood of the host organism
    • An outer lipid envelope with glycoproteins that bind to receptors on the host cell surface
    • A nucleus that holds the genetic material and attaches to the membrane of the host cell

  9. Antibiotics are effective against bacteria but not viruses because:

    • Antibiotics are broken down by the capsid of every virus, so they cannot reach the genome
    • Antibiotics only work on Gram-negative bacteria, which have no cell wall at all
    • Viruses are too large for antibiotics to enter, but bacteria are small enough to be affected
    • Antibiotics target structures such as the bacterial cell wall or 70S ribosomes

  10. Which statement compares the genetic material of bacteria and viruses correctly?

    • Bacteria always carry DNA, but viruses may carry either DNA or RNA as their genetic material
    • Bacteria carry RNA only, but viruses always carry double-stranded DNA as their genetic material
    • Both bacteria and viruses carry only DNA in a linear form, enclosed in a nuclear membrane
    • Neither bacteria nor viruses carry any genetic material and rely on the host for all instructions

  11. Why are bacteria described as prokaryotic?

    • Because they are multicellular and have specialised tissues with nuclei in each cell
    • Because they are formed from a capsid and an envelope with no cytoplasm inside
    • Because they contain a large number of membrane-bound organelles including mitochondria
    • Because they lack a membrane-bound nucleus and other membrane-bound organelles

  12. A student compares a bacterium and a virus under an electron microscope. Which observation would show that the specimen is the bacterium?

    • A single layer of glycoprotein spikes on the surface and no internal structures visible
    • A lipid envelope with no internal organisation and a small bundle of nucleic acid
    • A cytoplasm containing ribosomes, surrounded by a plasma membrane and a cell wall
    • A protein coat arranged in a regular geometric shape with no internal cytoplasm

  13. Which statement evaluates the claim that viruses are living organisms?

    • The claim is contested, because viruses have genetic material and evolve but cannot replicate or metabolise outside a host cell
    • The claim is true only for enveloped viruses, because they can photosynthesise in sunlight
    • The claim is certainly false, because viruses are made of DNA and so cannot evolve by natural selection
    • The claim is certainly true, because viruses carry out respiration and grow in size as all living things do

  14. Which structure is present in both a bacterial cell and a human cell?

    • A nucleus, which contains the linear chromosomes that carry the genetic information
    • A peptidoglycan cell wall, which provides support and prevents bursting in every cell
    • Chloroplasts, which absorb light energy and convert it into chemical energy in the cytoplasm
    • A cell membrane, which controls movement of substances into and out of the cell

  15. A bacterium is 2 micrometres long and a virus is 100 nanometres long. How many times longer is the bacterium?

    • 1,000 times, since one micrometre is always 1,000 times longer than one nanometre
    • 20 times, since 2 micrometres equals 2,000 nanometres and 2,000 divided by 100 is 20
    • 200 times, since 2 micrometres equals 200 nanometres and 200 divided by 1 is 200
    • 2 times, since 2 micrometres and 100 nanometres differ by a factor of two only

  16. Which feature distinguishes a bacterial plasmid from the main bacterial chromosome?

    • A plasmid is a small, extra circular DNA molecule that is not essential for basic cell survival
    • A plasmid is a membrane-bound nucleus that stores genetic information separately in the cell
    • A plasmid is a protein coat around the bacterium that protects it from antibiotics
    • A plasmid is a linear chromosome that is always larger than the main bacterial chromosome

  17. Which statement about the capsid is accurate?

    • The capsid is a protein coat that protects the viral genome and may help it attach to host cells
    • The capsid is a peptidoglycan wall that gives the virus its shape and rigidity
    • The capsid is a membrane of phospholipid that controls the movement of molecules into the virus
    • The capsid is a ribosome that synthesises the proteins needed to make new virus particles

  18. Which property is shared by bacteria and viruses?

    • Both have a nucleus that contains linear chromosomes separated from the cytoplasm
    • Both respire aerobically using mitochondria located inside the cell membrane
    • Both carry genetic material that can mutate
    • Both build their own ribosomes in a nucleolus before making any proteins

  19. A student applies the Gram stain to bacteria. What does the stain reveal about the bacteria?

    • The number of ribosomes present in the cytoplasm of each bacterium on the slide
    • Whether a virus particle has a capsid or an envelope around its genetic material
    • The presence or absence of a nucleus, which separates eukaryotes from prokaryotes
    • Differences in peptidoglycan wall structure

  20. Which feature allows bacteria to grow and reproduce without a host cell?

    • Dependence on host ribosomes for the synthesis of every protein they need to survive
    • A glycoprotein envelope that fuses with host membranes to deliver the genome into cells
    • A capsid that releases nucleic acid into a host cell once it attaches to the surface
    • Their own ribosomes and metabolic enzymes

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