Back to Topic 3.1 — Enzymes and metabolism
3.1.6Biology SL12 flashcards

Intracellular and extracellular enzymes

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Card 1 of 123.1.6
3.1.6
Question

What is an intracellular enzyme?

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All 12 Flashcards — Intracellular and extracellular enzymes

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Card 1definition

Question

What is an intracellular enzyme?

Answer

An enzyme that catalyses a reaction **inside** the cell that produced it (e.g. a **respiration** enzyme).

Card 2definition

Question

What is an extracellular enzyme?

Answer

An enzyme that is **secreted** and catalyses a reaction **outside** the cell (e.g. a **digestive** enzyme).

Card 3definition

Question

What does it mean to 'secrete' an enzyme?

Answer

To **release** the enzyme out of the cell, through the membrane, into the surroundings.

Card 4concept

Question

Give an example of an intracellular enzyme.

Answer

A **respiration** enzyme (or catalase breaking down hydrogen peroxide inside the cell).

Card 5concept

Question

Give an example of an extracellular enzyme.

Answer

A **digestive** enzyme such as **amylase, protease or lipase** — or the enzymes a decomposer secretes onto dead matter.

Card 6concept

Question

Why does a cell secrete a digestive enzyme instead of keeping it inside?

Answer

Because a large food molecule (e.g. starch, protein) is **too big to cross the cell membrane**; it must be broken into small soluble subunits first.

Card 7concept

Question

What does an extracellular digestive enzyme do to a large food molecule?

Answer

It **hydrolyses** it into **small, soluble subunits** (e.g. starch → maltose/glucose) that **can be absorbed**.

Card 8concept

Question

How do decomposers (saprotrophs) feed?

Answer

They **secrete extracellular enzymes** onto dead matter, digest it **externally**, then **absorb** the small soluble products.

Card 9concept

Question

Does being secreted change how an enzyme works?

Answer

**No** — both intracellular and extracellular enzymes are globular proteins that **lower activation energy**, are **specific** and are **reusable**. Only the location differs.

Card 10concept

Question

In a data question, what tells you an enzyme is extracellular?

Answer

Its **activity appears outside the cell** (e.g. in the surrounding liquid / culture medium), acting on a substrate the cell has not absorbed.

Card 11definition

Question

What is a metabolic pathway?

Answer

A linked series of enzyme-controlled reactions where the **product of one reaction is the substrate of the next** — run by intracellular enzymes.

Card 12concept

Question

What do 'intra-' and 'extra-' mean?

Answer

**Intra** = inside; **extra** = outside — so intracellular acts **inside** the cell and extracellular acts **outside** it.

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