A-Level Biology (Edexcel) > 2: Immune System > Flashcards

2: Immune System Flashcards

Describe immune responses including antigen recognition and antibody production. (36 cards)

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1
Q

How does the immune system distinguish between different types of cells in the body?

A

Specific surface molecules

Cells have unique proteins and glycoproteins on their membranes that allow recognition by immune cells.

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2
Q

What is the name given to a molecule that can trigger an immune response when recognised as foreign?

A

Antigen

Antigens are usually proteins or glycoproteins on the surface of pathogens or abnormal cells.

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3
Q

Why does high variability in pathogen antigens make disease prevention more difficult?

A

Immune evasion

Changes in antigen structure prevent immune memory cells or vaccines from recognising the pathogen effectively.

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4
Q

Which immune process involves engulfing and digesting pathogens?

A

Phagocytosis

Carried out by phagocytes such as macrophages and neutrophils.

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5
Q

What enzymes inside phagocytes break down pathogens after they are engulfed?

A

Hydrolytic enzymes

Hydrolytic enzymes are contained in lysosomes that fuse with the phagocytic vesicle.

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6
Q

Which type of immune cell displays pathogen antigens on its surface after phagocytosis?

A

Antigen-presenting cell

Macrophages and dendritic cells present antigens to activate lymphocytes.

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7
Q

Which type of T lymphocyte activates other immune cells after recognising an antigen on an antigen-presenting cell?

A

Helper T cells

Helper T cells release cytokines that stimulate B cells, cytotoxic T cells and phagocytes.

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8
Q

Which type of T lymphocyte destroys infected body cells by releasing toxic substances?

A

Cytotoxic T cells

Cytotoxic T cells induce apoptosis in infected or abnormal cells.

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9
Q

Which immune cells produce antibodies after being activated by helper T cells?

A

B lymphocytes

B cells differentiate into plasma cells that secrete antibodies.

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10
Q

What process ensures that only B cells with complementary receptors to an antigen are stimulated to divide?

A

Clonal selection

The selected B cell rapidly divides to produce many identical clones.

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11
Q

What is the name given to proteins produced by B cells that specifically bind to antigens?

A

Antibody

Antibodies are also known as immunoglobulins.

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12
Q

What general shape do antibodies have due to their arrangement of polypeptide chains?

A

Y-shaped

Antibodies consist of two heavy chains and two light chains linked by disulfide bonds.

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13
Q

Fill in the blank:

Antibodies bind to pathogens forming an ______–antibody complex.

A

antigen

The binding occurs at the specific antigen-binding site of the antibody.

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14
Q

Which immune process occurs when antibodies cause pathogens to clump together, making them easier for phagocytes to engulf?

A

Agglutination

Agglutination increases the efficiency of phagocytosis.

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15
Q

True or False:

Plasma cells are responsible for long-term immune memory.

A

False

Plasma cells produce large quantities of antibodies; memory cells provide long-term immunity.

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16
Q

Which cells remain in the body after infection and allow a faster response if the same pathogen is encountered again?

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A

Memory cells

Memory cells are responsible for the secondary immune response.

17
Q

What is the term for the rapid and stronger immune reaction when a previously encountered antigen enters the body again?

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A

Secondary immune response

This response produces antibodies more quickly and in larger quantities.

18
Q

What biological preparation containing antigen material is used to stimulate immunity without causing disease?

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A

Vaccine

Vaccines trigger an immune response and memory cell formation.

19
Q

What term describes the protection provided to unvaccinated individuals when a high proportion of the population is immune?

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A

Herd immunity

It reduces the spread of pathogens within a population.

20
Q

What type of immunity occurs when the body produces its own antibodies after exposure to an antigen?

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A

Active immunity

Can occur naturally through infection or artificially through vaccination.

21
Q

What type of immunity results from receiving antibodies produced by another organism?

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A

Passive immunity

Provides immediate protection but is usually short-lived because memory cells are not formed.

22
Q

A virus that infects helper T cells and leads to the development of AIDS is known as what?

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A

Human immunodeficiency virus

(HIV)

HIV is a retrovirus that targets helper T lymphocytes, weakening the immune system over time.

23
Q

Which type of white blood cell is primarily infected and destroyed by HIV?

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A

Helper T cells

These cells coordinate immune responses by activating other immune cells such as B cells and cytotoxic T cells.

24
Q

What enzyme allows HIV to convert its RNA genome into DNA inside a host cell?

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A

Reverse transcriptase

This enzyme synthesises DNA from the viral RNA template, allowing integration into the host genome.

25
After **HIV DNA integrates** into the DNA of a **helper T cell**, what happens to viral gene expression?
**Viral proteins** are produced using host cell machinery. ## Footnote The host cell transcribes and translates viral genes, producing components for new viruses.
26
How does **HIV infection** ultimately lead to the **symptoms associated with AIDS**?
Progressive destruction of **helper T cells** ## Footnote Loss of helper T cells prevents effective immune responses, leaving the body vulnerable to opportunistic infections.
27
# True or False: **Antibiotics** are effective treatments for infections caused by **viruses** such as HIV.
False ## Footnote Antibiotics target bacterial structures or metabolic pathways that viruses do not possess.
28
Why are **antibiotics ineffective** against **viruses**?
Viruses replicate inside **host cells** and lack cellular structures targeted by antibiotics. ## Footnote Antibiotics typically act on bacterial cell walls, ribosomes or metabolic pathways absent in viruses.
29
What type of **laboratory-produced antibodies** are designed to bind to **one specific antigen**?
Monoclonal antibodies ## Footnote They are identical antibodies produced from a single clone of cells and recognise a single antigen.
30
How can **monoclonal antibodies** be used to **deliver drugs to specific cell types** in the body?
By attaching a **therapeutic drug** to the antibody. ## Footnote The antibody binds to specific antigens on target cells, directing the drug precisely to those cells.
31
How are **monoclonal antibodies** useful in **medical diagnosis**?
They bind specifically to **particular antigens**. ## Footnote This allows detection of substances such as hormones, pathogens or tumour markers.
32
Which **immunological test** uses **antibodies linked to enzymes** to detect the presence of antigens or antibodies in a sample?
ELISA ## Footnote Enzyme-Linked Immunosorbent Assay produces a colour change when the target molecule is present.
33
# Fill in the blank: In the **ELISA test**, the presence of the target molecule is often indicated by a \_\_\_\_\_\_ change.
colour ## Footnote The enzyme linked to the antibody catalyses a reaction producing a visible colour change.
34
# True or False: **Vaccination programmes** can raise **ethical issues** related to individual choice and public health protection.
True ## Footnote Debates often involve mandatory vaccination, safety concerns and balancing personal freedom with community protection.
35
What **ethical concern** may arise from the use of **monoclonal antibodies** in medicine?
Use of animals or animal-derived cells. ## Footnote Some production methods historically involved mice, raising animal welfare concerns.
36
What key **skill** should students develop when studying **vaccines and monoclonal antibodies** in biology?
Evaluating methodology, evidence and data. ## Footnote Students should assess the reliability of studies and interpret data on effectiveness and safety.
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