Sexually transmitted infections
Cambridge IGCSE Biology (0610) · Unit 16: Reproduction · 9 flashcards
Sexually transmitted infections is topic 16.6 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 16 — Reproduction , alongside Asexual reproduction, Sexual reproduction and Sexual reproduction in plants. In one line: An STI is an infection that is transmitted through sexual contact, including vaginal, anal, and oral sex. Examples include HIV, chlamydia, and gonorrhea.
This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 record 2 explicit questions on this topic — though the concept underpins many adjacent topics, so it is tested far more often than that figure suggests.
The deck below contains 9 flashcards — 3 definitions, 3 key concepts, 2 process cards and 1 application card — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
A sexually transmitted infection (STI)
An STI is an infection that is transmitted through sexual contact, including vaginal, anal, and oral sex. Examples include HIV, chlamydia, and gonorrhea.
What the Cambridge 0610 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Describe Describe a sexually transmitted infection (STI) as an infection that is transmitted through sexual contact
- State State that human immunodeficiency virus (HIV) is a pathogen that causes an STI
- State State that HIV infection may lead to AIDS
- Describe Describe the methods of transmission of HIV
- Explain Explain how the spread of STIs is controlled
What is a sexually transmitted infection (STI)?
An STI is an infection that is transmitted through sexual contact, including vaginal, anal, and oral sex. Examples include HIV, chlamydia, and gonorrhea.
What type of pathogen is HIV?
HIV (human immunodeficiency virus) is a virus. Viruses are non-cellular pathogens that replicate inside host cells, causing damage. HIV specifically attacks immune cells.
What disease can HIV infection lead to?
HIV infection can lead to AIDS (acquired immunodeficiency syndrome). AIDS weakens the immune system, making individuals vulnerable to opportunistic infections and cancers.
Describe three methods of HIV transmission.
HIV is transmitted through unprotected sexual contact (vaginal, anal, oral), sharing needles or syringes, and from mother to child during pregnancy, childbirth, or breastfeeding. It's found in bodily fluids like blood, semen, and breast milk.
How can the spread of STIs be controlled?
STI spread can be controlled through practicing safe sex (using condoms), regular STI testing, partner notification and treatment, abstinence, and vaccination (for some STIs like HPV). Public health campaigns also play a role.
Explain the role of condoms in preventing STI transmission.
Condoms act as a physical barrier preventing the exchange of bodily fluids (semen, vaginal fluids) during sexual contact. This reduces the risk of STI transmission, as many pathogens are transmitted through these fluids.
Why is early detection and treatment important for controlling STIs?
Early detection and treatment prevent the STI from progressing and causing more severe health complications. Treatment also reduces the likelihood of transmission to other individuals, thus controlling the spread.
Outline the effects of HIV on the immune system.
HIV specifically targets and destroys immune cells called helper T cells (CD4 cells). This weakens the immune system, making the infected individual more susceptible to opportunistic infections such as pneumonia and tuberculosis.
What is meant by the term 'opportunistic infection' in the context of AIDS?
An opportunistic infection is an infection caused by a pathogen that does not usually cause disease in a person with a healthy immune system. In AIDS patients, the weakened immune system allows these pathogens to cause serious illness.
Key Questions: Sexually transmitted infections
What is a sexually transmitted infection (STI)?
An STI is an infection that is transmitted through sexual contact, including vaginal, anal, and oral sex. Examples include HIV, chlamydia, and gonorrhea.
What type of pathogen is HIV?
HIV (human immunodeficiency virus) is a virus. Viruses are non-cellular pathogens that replicate inside host cells, causing damage. HIV specifically attacks immune cells.
What is meant by the term 'opportunistic infection' in the context of AIDS?
An opportunistic infection is an infection caused by a pathogen that does not usually cause disease in a person with a healthy immune system. In AIDS patients, the weakened immune system allows these pathogens to cause serious illness.
Tips to avoid common mistakes in Sexually transmitted infections
- ● Note that phloem vessels transport sucrose (soluble), not starch (insoluble storage molecule).
- ● Always align the number of points you give with the mark allocation for the question, especially if it's three marks.
- ● Connect the increase in temperature to the increased rate of water molecule evaporation and loss.
- ● Recite the sequence of transpiration: water evaporates from mesophyll cells and then diffuses out of the leaf.
- ● Picture the spongy mesophyll as a vast evaporative surface during transpiration.
More topics in Unit 16 — Reproduction
Sexually transmitted infections sits alongside these Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Sexually transmitted infections deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
Related Biology guides
Long-read articles that go beyond the deck — cover the whole subject's common mistakes, high-yield content and revision pacing.
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