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A Level H1 Biology Human Physiology Quiz

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Questions

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A-Level Biology H1 Quiz - Human Physiology

Name: __________________________
Class: __________________________
Date: __________________________
Score: ________ / 45

Duration: 45 minutes
Total Marks: 45
Instructions:

  1. Answer all questions.
  2. Write your answers in the spaces provided.
  3. The number of marks is given in brackets [ ] at the end of each question or part question.
  4. This quiz covers Section IV: Human Physiology (Immunity and Infectious Diseases).

Section A: Multiple Choice & Short Answer (Questions 1–5)

1. Which of the following best describes the role of lysozyme in the human body’s defense against pathogens?
A. It stimulates the production of antibodies by B-lymphocytes.
B. It breaks down the cell walls of bacteria in tears and saliva.
C. It engulfs pathogens via phagocytosis in the bloodstream.
D. It creates an acidic environment in the stomach to kill ingested microbes.
[1]

2. During an inflammatory response, histamine is released by mast cells. What is the primary effect of histamine on local blood vessels?
A. Vasoconstriction and decreased permeability
B. Vasoconstriction and increased permeability
C. Vasodilation and decreased permeability
D. Vasodilation and increased permeability
[1]

3. State the specific type of immunity acquired when a person receives a vaccine containing inactivated pathogens.
[1]

4. Distinguish between an antigen and an antibody.
[2]

5. Fig. 1.1 shows a schematic representation of an antibody molecule.

(Imagine a Y-shaped molecule with labels A, B, and C)

  • A: The tips of the Y arms
  • B: The stem of the Y
  • C: The hinge region

Identify the region labeled A and state its significance in immune response.
[2]
Region A: __________________________
Significance: ______________________________________________________________

Section B: Structured Questions (Questions 6–15)

6. Phagocytes are a key component of the non-specific immune response.
(a) Name two types of phagocytes found in human blood.
[1]

(b) Describe the process of phagocytosis of a bacterium by a phagocyte.
[3]

7. T-lymphocytes play a central role in the specific immune response.
(a) Differentiate between the roles of T-helper cells and T-killer (cytotoxic) cells.
[2]
T-helper cells: ___________________________________________________________

T-killer cells: ____________________________________________________________

(b) Explain why T-lymphocytes do not respond to free-floating antigens in the blood plasma.
[2]

8. Fig. 2.1 shows the change in antibody concentration in the blood of an individual over time after two separate exposures to the same antigen.

(Graph description: X-axis is Time (days). Y-axis is Antibody Concentration. First peak is low and slow (days 5-14). Second peak is high and rapid (days 2-7 after second exposure).)

(a) Identify the cells responsible for the rapid production of antibodies during the second exposure.
[1]

(b) Explain why the secondary immune response is faster and produces a higher concentration of antibodies than the primary response.
[3]

9. Monoclonal antibodies are widely used in diagnostic tests, such as pregnancy tests.
(a) Define the term monoclonal antibody.
[2]

(b) Explain why monoclonal antibodies are preferred over polyclonal antibodies for diagnostic precision.
[2]

10. HIV (Human Immunodeficiency Virus) targets specific cells in the immune system.
(a) Name the specific type of lymphocyte that HIV primarily infects.
[1]

(b) Explain how the destruction of these cells leads to the symptoms associated with AIDS (Acquired Immunodeficiency Syndrome).
[3]

11. Antibiotics are effective against bacterial infections but not viral infections.
(a) Explain why antibiotics do not kill viruses.
[2]

(b) Suggest one mechanism by which bacteria can become resistant to antibiotics.
[1]

12. Vaccination programs have successfully eradicated smallpox and reduced the incidence of polio.
(a) Explain the principle behind herd immunity.
[2]

(b) Suggest why it is more difficult to develop a vaccine for HIV compared to the measles virus.
[2]

13. Describe the structure of an antibody molecule and relate its structure to its function.
[4]

14. Autoimmune diseases occur when the immune system fails to distinguish self from non-self.
(a) Name one example of an autoimmune disease.
[1]

(b) Explain what happens at the cellular level in an autoimmune disease.
[2]

15. Memory cells are crucial for long-term immunity.
(a) State two differences between a memory B-cell and a plasma cell.
[2]

(b) Explain why memory cells remain in the body for many years after an infection has cleared.
[2]

Section C: Free Response / Data Analysis (Questions 16–20)

16. Fig. 3.1 shows the structure of the HIV virus.

(Diagram showing: Envelope with glycoproteins, Capsid, RNA, Reverse Transcriptase enzyme)

(a) Identify the enzyme labeled Reverse Transcriptase and describe its function during the early stages of HIV infection.
[2]

(b) Explain why the presence of an envelope makes HIV susceptible to disinfectants like alcohol, despite being a dangerous pathogen.
[2]

17. A new strain of influenza virus emerges.
(a) Explain how antigenic drift differs from antigenic shift.
[2]

(b) Suggest why antigenic shift is more likely to cause a pandemic than antigenic drift.
[2]

18. Discuss the role of cytokines in coordinating the immune response.
[3]

19. In the context of organ transplantation, explain why patients must take immunosuppressant drugs for the rest of their lives.
[3]

20. "Vaccines prevent disease, but they do not always prevent infection."
Evaluate this statement with reference to the mechanism of action of vaccines and the nature of the immune response.
[4]

[END OF QUIZ]

Answers

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A-Level Biology H1 Quiz - Human Physiology (Answer Key)

1. B
Lysozyme is an enzyme found in secretions like tears and saliva that hydrolyzes peptidoglycan in bacterial cell walls. [1]

2. D
Histamine causes vasodilation (increasing blood flow/redness) and increased permeability (allowing plasma/phagocytes to exit vessels). [1]

3. Artificial active immunity.
[1] (Must include both "Artificial" and "Active")

4.

  • Antigen: A molecule (usually protein/polysaccharide) on the surface of a pathogen or foreign cell that triggers an immune response. [1]
  • Antibody: A specific protein (immunoglobulin) produced by B-lymphocytes/plasma cells that binds to a specific antigen. [1]

5.

  • Region A: Antigen-binding site / Variable region. [1]
  • Significance: It has a specific tertiary structure complementary to a specific antigen, allowing specific binding. [1]

6.
(a) Neutrophils and Monocytes (or Macrophages). [1]
(b)

  1. Pathogen binds to receptors on phagocyte surface. [1]
  2. Phagocyte engulfs pathogen via endocytosis, forming a phagosome. [1]
  3. Lysosomes fuse with phagosome to form phagolysosome; enzymes digest the pathogen. [1]

7.
(a)

  • T-helper cells: Secrete cytokines to stimulate B-cells and T-killer cells; activate macrophages. [1]
  • T-killer cells: Destroy infected host cells by inducing apoptosis or releasing perforins. [1]
    (b)
  1. T-lymphocytes have receptors that only recognize antigens presented on MHC (Major Histocompatibility Complex) molecules. [1]
  2. Free-floating antigens are not presented on MHC molecules, so T-cells cannot bind/recognize them directly. [1]

8.
(a) Memory B-cells. [1]
(b)

  1. Memory B-cells formed during primary response remain in the body. [1]
  2. Upon second exposure, they recognize the antigen immediately and undergo rapid clonal selection/expansion. [1]
  3. They differentiate into plasma cells faster, producing a higher concentration of antibodies in a shorter time. [1]

9.
(a) Antibodies produced by a clone of identical hybridoma cells, specific to a single epitope/antigen. [2]
(b)

  1. They are highly specific to one binding site/epitope. [1]
  2. This reduces cross-reactivity with other molecules, ensuring accurate diagnosis. [1]

10.
(a) T-helper cells (CD4+ T cells). [1]
(b)

  1. Loss of T-helper cells means B-cells and T-killer cells are not activated/stimulated. [1]
  2. The specific immune response is severely compromised/failed. [1]
  3. The body cannot fight off opportunistic infections or cancers. [1]

11.
(a)

  1. Viruses lack metabolic machinery/cell walls that antibiotics target. [1]
  2. Viruses replicate inside host cells using host machinery, making them inaccessible to many antibiotics. [1]
    (b) Mutation (changing the target site) OR Acquisition of plasmids carrying resistance genes. [1]

12.
(a)

  1. When a high percentage of the population is immune, the pathogen cannot spread easily. [1]
  2. This protects vulnerable/unvaccinated individuals by breaking the chain of transmission. [1]
    (b)
  3. HIV has a high mutation rate (due to error-prone reverse transcriptase). [1]
  4. This leads to rapid changes in surface antigens, making it difficult for vaccines to target a stable antigen. [1]

13.

  1. Y-shaped quaternary structure made of 4 polypeptide chains (2 heavy, 2 light). [1]
  2. Held together by disulfide bridges. [1]
  3. Variable regions at the tips allow specific binding to antigens. [1]
  4. Constant region allows binding to phagocytes/complement proteins (effector function). [1]

14.
(a) Rheumatoid arthritis / Type 1 Diabetes / Lupus / Multiple Sclerosis. [1]
(b)

  1. T-cells/B-cells fail to recognize self-antigens as "self". [1]
  2. They attack and destroy the body’s own healthy tissues/cells. [1]

15.
(a)

  1. Plasma cells secrete antibodies; Memory cells do not. [1]
  2. Plasma cells are short-lived; Memory cells are long-lived. [1]
    (b)
  3. To provide long-term immunity against reinfection. [1]
  4. They persist in the blood/lymph to respond rapidly if the same pathogen enters the body again. [1]

16.
(a)

  1. Reverse Transcriptase. [1]
  2. It converts viral single-stranded RNA into double-stranded DNA, which can then integrate into the host genome. [1]
    (b)
  3. The envelope is derived from the host cell membrane (lipid bilayer). [1]
  4. Alcohol/disinfectants dissolve lipids, disrupting the envelope and rendering the virus non-infectious. [1]

17.
(a)

  • Drift: Small, gradual mutations in surface antigens. [1]
  • Shift: Sudden, major change in antigens due to reassortment of genetic material (e.g., between different strains). [1]
    (b)
  1. Antigenic shift creates a completely new strain to which the population has no existing immunity/memory cells. [1]
  2. This allows rapid, widespread transmission across the globe (pandemic). [1]

18.

  1. Cytokines are chemical messengers secreted by T-helper cells/macrophages. [1]
  2. They stimulate the division/differentiation of B-cells and T-cells (clonal expansion). [1]
  3. They attract phagocytes to the site of infection (chemotaxis) and increase inflammation. [1]

19.

  1. The donor organ has different MHC/antigens on its cell surfaces. [1]
  2. The recipient’s immune system recognizes these as foreign/non-self. [1]
  3. Without suppression, T-cells would attack and reject the organ; drugs suppress this specific immune response. [1]

20.

  1. Vaccines stimulate the production of memory cells and antibodies before exposure. [1]
  2. If infection occurs, the secondary response is so rapid that the pathogen is cleared before it causes significant damage/symptoms. [1]
  3. However, the pathogen may still enter and replicate briefly (infection) before the immune system eliminates it. [1]
  4. Some vaccines (sterilizing immunity) prevent infection entirely, but many only prevent disease severity. [1]