Explaining the effect of different substrates on the rate of cellular respiration | Combined science

Starter quiz

This apparatus is used to measure the rate of cellular respiration of immobilised yeast. Which gas will be collected in the measuring cylinder?

'carbon dioxide' ✓
This apparatus is used to measure the rate of cellular respiration of immobilised yeast with different substrates. Put the method into the correct order.

1

⇔

Add the substrate to the conical flask.

2

⇔

Add water to the conical flask and swirl.

3

⇔

Add the alginate beads containing yeast.

4

⇔

Place the bung and delivery tube into the top of the conical flask.

5

⇔

Place the conical flask in the water bath.

6

⇔

Wait 5 minutes for the conical flask/contents to get to water bath temperature.
Match the type of respiration to its correct equation.

Aerobic respiration

⇔

glucose + oxygen --> water + carbon dioxide ✓

Anaerobic respiration (animals)

⇔

glucose --> lactic acid ✓

Anaerobic respiration (plants)

⇔

glucose --> carbon dioxide + ethanol ✓
Enzymes are catalysts. They speed up reactions because ...

they increase the reaction temperature.

they increase the substrate collision rate.

they are permanently changed by the reaction.

they provide a site for the reaction to take place. ✓
Which statement is true only for aerobic cellular respiration?

It takes place in the cytoplasm.

It takes place in the nucleus.

It takes place in the mitochondria. ✓

It is endothermic.

It is exothermic.
The glucose used in all types of respiration is produced by plants or other organisms that have chlorophyll. What process produces the glucose?

'photosynthesis' ✓

Exit quiz

Match each word to its correct meaning.

Active site

⇔

the part of an enzyme’s structure where the substrate binds ✓

Enzyme

⇔

biological catalyst ✓

Lock and key

⇔

a model used to explain why each enzyme can only catalyse one reaction ✓

Substrate

⇔

a substance that binds to the active site of an enzyme ✓

Rate

⇔

a measure of change over time ✓
This apparatus is used to measure the volume of gas produced by cellular respiration. Air is trapped at the top when it is set up, before it is used. This will cause ______ error in the results.

'random' ✓
The volume of gas produced by respiration in 5 minutes was measured. The starting volume was 3 cm $^3$ . The final volume was 28 cm $^3$ . What is the rate of respiration in cm $^3$ /min?

'5' ✓
Which statement best compares the rate of respiration for these substrates?

Each substrate is respired at a different rate.

Some substrates can be respired faster than others.

The respiration rates are similar for each substrate.

The rate of respiration is higher for glucose than the other substrates. ✓

The rate of respiration is lowest for maltose.
Which statement about the data is true?

The rate for glucose is 5 times greater than for sucrose.

The rate for glucose is 4 times greater than for sucrose.

The rate for glucose is twice that for maltose. ✓

The rate for maltose is less than twice that for glucose.
Maltose is made of two glucose molecules joined together. What has to happen to maltose before it can be used for cellular respiration?

Maltose has to be split into two glucose molecules by an enzyme. ✓

A new enzyme has to be made to respire maltose.

Maltose molecules have to be changed in shape.

Two maltose molecules have to be joined together to make glucose.

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Lesson Details

Key learning points

Process data to calculate the volume of gas collected in the measuring cylinder, and the mean of repeat measurements.
Calculate the rate of respiration by dividing the volume of gas collected in the measuring cylinder by the time.
Use appropriate units for the rate of cellular respiration.
Compare the rate of respiration in yeast given different substrates, and describe trends in the data.
Use ideas about enzymes and active sites to explain the effect of different substrates on the rate of respiration.

Common misconception

Thinking that each enzyme can act on many different substrates.

This lesson reinforces understanding that each enzyme has a specific substrate, because only that substrate will fit into they enzyme's active site.

Keywords

Rate - A measure of how much change occurs per unit of time.
Cellular respiration - An exothermic chemical process that transfers energy for life processes, using glucose as fuel.
Substrate - The substance that fits into an enzyme’s active site.
Enzyme - A biological catalyst.
Active site - The part of an enzyme where the substrate binds.