The term 'ACE2' is talked about in the context of

Updated 11 Apr 2026 · From UPSC Prelims GS Paper I 2021, Q96

Contents9
UPSC Prelims GS2021Science and Technology
  1. Agenes introduced in the genetically modified plants
  2. Bdevelopment of India's own satellite navigation system
  3. Cradio collars for wildlife tracking
  4. Dspread of viral diseases
Show answer

Answer: (D) spread of viral diseases

ACE2 (Angiotensin-Converting Enzyme 2) is an enzyme on the surface of human cells that became widely discussed during COVID-19.

The SARS-CoV-2 virus's spike protein binds to ACE2 receptors to enter cells, fuse with the cell surface, and inject its RNA.

The earlier SARS-CoV also used ACE2.

ACE2 is found in cells of the lungs, heart, kidneys, and intestines, explaining why COVID-19 affects multiple organs.

Answer: (d) — spread of viral diseases.

Why this was asked

ACE2 is the cell receptor that SARS-CoV-2 uses to enter human cells, making it central to understanding COVID-19 transmission and pathology.

COVID-19 dominated global discourse in 2020-21, making ACE2 a frequently discussed term in news and scientific literature during this exam cycle.

The question tests whether students can connect a technical biochemical term to its real-world disease context rather than getting distracted by unrelated technology options.

ACE2 Receptor & Viral Entry

Science And Technology ACE2

ACE2 Receptor: How Viruses Enter Human Cells

Must know

ACE2 = Angiotensin-Converting Enzyme 2, a receptor on human cell surfaces

SARS-CoV-2 and SARS-CoV both use ACE2 to enter cells

Found in lungs, heart, kidneys, intestines — explains multi-organ COVID-19 effects

Good to know

Virus spike protein binds to ACE2, then injects RNA into cell

What is ACE2?

ACE2 (Angiotensin-Converting Enzyme 2) is a protein receptor found on the surface of human cells. It became widely discussed during the COVID-19 pandemic because the SARS-CoV-2 virus uses ACE2 as its entry point into human cells.

Viral Entry Mechanism

%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
  s1["`**Virus Approach**
**SARS-CoV-2** virus approaches human cell with ACE2 receptors`"]
  s2["`**Spike Binding**
Virus **spike protein** binds to **ACE2 receptor** on cell surface`"]
  s3["`**Membrane Fusion**
Virus fuses with cell membrane after successful binding`"]
  s4["`**RNA Injection**
Virus injects its **RNA** into the cell to begin replication`"]
  s1 --> s2
  s2 --> s3
  s3 --> s4

ACE2 Distribution in Body

Organ System

ACE2 Presence

COVID-19 Impact

Lungs

High

Respiratory symptoms, pneumonia

Heart

Moderate

Cardiac complications, myocarditis

Kidneys

High

Acute kidney injury

Intestines

High

Gastrointestinal symptoms, diarrhea

SARS-CoV (2003 SARS outbreak) also used ACE2 receptors for cell entry

MERS-CoV uses a different receptor (DPP4), not ACE2

ACE2 binding affinity varies between virus strains, affecting transmission rates

Exam traps

Don't confuse ACE2 with ACE1 — ACE2 is the viral receptor, ACE1 is a different enzyme

Not all coronaviruses use ACE2 — MERS uses DPP4 receptor instead

ACE2 is not just in lungs — multi-organ presence explains diverse COVID symptoms

COVID-19 & SARS Coronaviruses

Science And Technology viral diseases spread of viral diseases

Major Coronaviruses: COVID-19, SARS & MERS Comparison

Must know

COVID-19 caused by SARS-CoV-2, declared pandemic in 2020

SARS (2003) and COVID-19 both use ACE2 receptors

Good to know

MERS (2012) uses different receptor, higher mortality but lower transmission

Major Coronavirus Outbreaks

Disease

Virus

Year

Receptor Used

Mortality Rate

Transmission

COVID-19

SARS-CoV-2

2020-ongoing

ACE2

~1-3%

High human-to-human

SARS

SARS-CoV

2003

ACE2

~10%

Limited human-to-human

MERS

MERS-CoV

2012-ongoing

DPP4

~35%

Limited human-to-human

Key Characteristics

Zoonotic origin: All three likely originated in bats before jumping to humans

Respiratory focus: Primary symptoms involve lungs, but multi-organ effects possible

Airborne transmission: Spread through respiratory droplets and aerosols

Incubation period: Typically 2-14 days from exposure to symptom onset

UPSC Connection

This question tests knowledge of ACE2's role in viral diseases, specifically COVID-19. The correct answer eliminates three unrelated distractors (genetic modification, satellite navigation, wildlife tracking) that have no connection to ACE2.

Exam traps

ACE2 ≠ satellite technology — completely different fields, option B is a distractor

Don't link ACE2 to genetic modification — it's a natural human receptor, not GM technology

Wildlife tracking uses GPS collars — no connection to ACE2 enzyme