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Leaving Cert Biology: Enzymes

How often Enzymes comes up on the Biology papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 8 of the last 10 Ordinary Level papers, most recently in 2026. most years

June 2027 is the first exam on the new Biology course. These come from the 2016–2026 papers, so read them as a guide.

Enzymes, Higher Level(6 marks)

Quick ones on Enzymes.

(a)Enzymes are made of?
  1. Carbohydrate
  2. Protein
  3. Lipid
(b)Region of an enzyme where the substrate binds?
  1. Allele
  2. Binding protein
  3. Active site
(c)Permanent loss of an enzyme's shape?
  1. Denaturation
  2. Inhibition
  3. Immobilisation
Show the answers

(a) Protein

(b) Active site

(c) Denaturation

Your turn: Higher Level questions on Enzymes.

Higher Level

Asked on 9 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q9
2025Q5, Q13
2024Q9, Q10, Q17
2023Q12
2022Not asked
2021Q4, Q9
2019Q12
2018Q12
2017Q8
2016Q7, Q9

Links open the State Examinations Commission’s paper for that year.

More Enzymes questions

Enzymes, 2 marks

What keeps pH constant in the enzyme pH experiment?

  1. Water bath
  2. Distilled water
  3. Buffer solution
Show the answer

Buffer solution

A buffer resists changes in pH. A different buffer is used for each pH tested, while the temperature is kept constant.

Enzymes, 2 marks

Solution alginate beads are formed in?

  1. Hydrogen peroxide
  2. Calcium chloride
  3. Sodium chloride
Show the answer

Calcium chloride

Calcium ions cross-link the alginate, setting each drop into a firm gel bead that traps the yeast (enzyme) inside.

Enzymes, 2 marks

Enzymes speed up reactions by lowering the?

  1. Activation energy
  2. Temperature
  3. pH
Show the answer

Activation energy

It's the energy needed to start a reaction. By lowering it, enzymes let reactions happen quickly at body temperature.

Ordinary Level

Asked on 8 of the last 10 Ordinary Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q9, Q13
2025Q9, Q16
2024Q6, Q9
2023Q13
2022Not asked
2021Q9, Q10
2019Not asked
2018Q3, Q8, Q9
2017Q5
2016Q8, Q9

Links open the State Examinations Commission’s paper for that year.

More Enzymes questions

Enzymes, 2 marks

Enzymes are made of which type of biomolecule?

  1. Fat
  2. Carbohydrate
  3. Protein
Show the answer

Protein

Every enzyme is a protein, which is why heat and extreme pH destroy them: they change the shape of the protein.

Enzymes, 3 marks

The substance an enzyme works on is called?

  1. The catalyst
  2. The substrate
  3. The product
Show the answer

The substrate

Substrate goes in, product comes out. The substrate fits into the active site like a key into a lock.

Enzymes, 3 marks

What happens to an enzyme at a very high temperature?

  1. It is denatured and stops working
  2. It works faster and faster
  3. It turns into a sugar
Show the answer

It is denatured and stops working

Heat changes the shape of the active site, so the substrate no longer fits. The change is permanent, unlike the effect of cold.

Other Biology topics

All of Leaving Cert Biology