Immunity, Infection and Forensics | Edexcel A-Level Biology A (Salters-Nuffield) (9BN0)

Immunity, Infection and Forensics

180 questions
15 subtopics
Topics 5 and 6, examined on Paper 1 and Paper 3
Paper 1 and Paper 3

Covers how the body is invaded and defended, and how biology is used in forensic work: estimating time of death, DNA profiling, the structure of bacteria and viruses, the immune response, immunity and vaccination, and antibiotic resistance..

It covers decomposition, succession and forensic entomology, body cooling and rigor mortis, dNA profiling and the polymerase chain reaction, gel electrophoresis, the structure of bacteria and viruses, decomposition, and how pathogens enter the body, the body's barriers, and modelling bacterial growth, tuberculosis and HIV, the non-specific immune response, antigens, antibodies and B cells, t cells and cell-mediated immunity, active and passive immunity, natural and artificial, the evolutionary race and pathogen evasion, antibiotics and testing their effectiveness and hospital acquired infections and their control.

Sample questions from Immunity, Infection and Forensics

Answer each one closed book first, then open the answer.

Decomposition, succession and forensic entomology

Describe the advanced decay stage of decomposition.

Show the answer
Most soft tissue has been removed; decomposition slows significantly and remaining tissue dries out.
Body cooling and rigor mortis

When does rigor mortis reach maximum stiffness?

Show the answer
Approximately 12–24 hours after death.
Gel electrophoresis

Explain why shorter DNA fragments travel further through the gel than longer fragments.

Show the answer
Shorter fragments move faster and further because they can pass more easily through the pores in the gel matrix.
The structure of bacteria and viruses

Compare the typical size of bacteria and viruses.

Show the answer
Bacteria are typically 1–5 μm in diameter, whereas viruses are much smaller at 20–300 nm.
The body's barriers, and modelling bacterial growth

What antimicrobial substances can gut flora produce to protect against infection?

Show the answer
Gut flora can produce antimicrobial substances such as bacteriocins and organic acids that inhibit or kill pathogenic micro-organisms.
Tuberculosis and HIV

What happens to the DNA produced by HIV's reverse transcriptase?

Show the answer
It integrates into the host cell genome.
Antigens, antibodies and B cells

Which cells produce antibodies?

Show the answer
Plasma cells.
T cells and cell-mediated immunity

How do T killer cells destroy infected host cells?

Show the answer
By releasing perforin and granzymes.

The 15 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Decomposition, succession and forensic entomology	Recall questions on the stages of decomposition, the succession of insects on a corpse, and how blowfly larvae are used to estimate time since death.	14
Body cooling and rigor mortis	Recall questions on algor mortis and what changes its rate, and on the biochemical cause and time course of rigor mortis.	12
DNA profiling and the polymerase chain reaction	Recall questions on what a DNA profile can establish, and on denaturation, annealing and extension in PCR.	14
Gel electrophoresis	Recall questions on why fragments move towards the positive electrode, why shorter fragments travel further, and how the results are read.	9
The structure of bacteria and viruses	Recall questions on the bacterial cell wall, plasmids, flagella and capsule, the viral capsid and envelope, and why viruses are acellular.	17
Decomposition, and how pathogens enter the body	Recall questions on saprotrophic nutrition and the role of decomposers, and on the routes by which pathogens get in.	10
The body's barriers, and modelling bacterial growth	Recall questions on the skin, stomach acid and gut and skin flora, and on using exponential and logarithmic scales for bacterial growth.	9
Tuberculosis and HIV	Recall questions on how each is transmitted, which cells each infects, how each evades the immune system, and how the infection progresses.	13
The non-specific immune response	Recall questions on inflammation, lysozyme, interferons, and the stages of phagocytosis.	11
Antigens, antibodies and B cells	Recall questions on antibody structure and how antibodies work, opsonisation, and the roles of plasma and memory B cells.	13
T cells and cell-mediated immunity	Recall questions on where T cells mature, MHC presentation, and the roles of helper, killer and memory T cells.	11
Active and passive immunity, natural and artificial	Recall questions on the four combinations, how vaccination works, and why active immunity lasts while passive does not.	17
The evolutionary race and pathogen evasion	Recall questions on antigenic variation and other evasion mechanisms, and on what the evolutionary race theory proposes.	8
Antibiotics and testing their effectiveness	Recall questions on bacteriostatic against bactericidal antibiotics, and on measuring the zone of inhibition.	11
Hospital acquired infections and their control	Recall questions on the causes of hospital acquired infection, codes of practice for prescribing, and infection control measures.	11

Immunity, Infection and Forensics is 180 of the 1,892 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.