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SavannahYear 8
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ScienceGCSE biology: cells, organisation and bioenergetics30 min★★★ difficulty

Enzymes, digestion and the circulatory system

Organisation is the study of how cells build tissues, organs and systems that keep a large organism supplied.

Lesson overview

What you'll learn in this lesson

Explain cell structure, transport, enzyme action and bioenergetics at GCSE standard.

Key learning points

  • • Enzyme action
  • • The digestive system
  • • Heart, vessels and blood

This lesson at a glance

  • 30 minutes
  • 16 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

structuretransportenzymeactionbioenergetics

Scroll down — the lesson carries on below

Part 1 of 16 · Discover6%
1

Watch & discover

Part 1 of 16

Watch first

Enzymes, digestion and the circulatory system

An English teaching video on this topic from Cognito. Watch it, then scroll down for the lesson.

In a nutshell

Explain cell structure, transport, enzyme action and bioenergetics at GCSE standard.

2

Learning cycle

Part 2 of 16

Learning cycle 1 of 2

Part 1 · Enzyme action

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 16

Learn

Enzyme action

Enzymes are protein catalysts with an active site complementary to their substrate, described by the lock-and-key model. Rate increases with temperature until the enzyme denatures, and each enzyme has an optimum pH — pepsin in the acidic stomach, amylase in near-neutral saliva.

4

Explore the idea

Part 4 of 16

Learn

The digestive system

Carbohydrase, protease and lipase break large molecules into small soluble ones for absorption. Bile from the liver neutralises stomach acid and emulsifies fats to increase surface area. Food tests are examinable: Benedict's for sugars, iodine for starch, Biuret for protein and the emulsion test for lipids.

5

Quick check

Part 5 of 16

Quick check

An enzyme is denatured when

6

Quick check

Part 6 of 16

Quick check

Benedict's solution tests for

7

Reset break

Part 7 of 16

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
8

Learning cycle

Part 8 of 16

Learning cycle 2 of 2

Part 2 · Heart, vessels and blood

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 16

Learn

Heart, vessels and blood

The double circulatory system pumps blood to the lungs and separately to the body, maintaining higher pressure. Arteries have thick muscular walls, veins have valves and wide lumens, and capillaries are one cell thick for exchange. Blood carries red cells, white cells, platelets and plasma, each with a distinct role.

10

Quick check

Part 10 of 16

Quick check

Arteries have thick muscular walls because they

11

Quick check

Part 11 of 16

Quick check

A double circulatory system means blood passes through the heart

12

Explore the idea

Part 12 of 16

Worked example

Worked answer: explain the effect of increasing temperature on enzyme activity (4 marks)

As temperature rises, enzyme and substrate molecules gain kinetic energy and collide more often, so the rate of reaction increases (1). The rate is highest at the optimum temperature (1). Above this, the bonds holding the enzyme's shape break and the active site changes shape, so it is denatured (1). The substrate no longer fits the active site, so the rate falls sharply and the change is not reversible (1).

13

Challenge round

Part 13 of 16

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

14

Challenge round

Part 14 of 16

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

Rate increases with temperature until the ____ denatures, and each enzyme has an optimum pH — pepsin in the acidic stomach, amylase in near-neutral saliva.

15

Mastery quiz

Part 15 of 16

Marked quiz

End of lesson quiz: Enzymes, digestion and the circulatory system

4 questions, marked with the reasoning shown. No timer.

  1. 1. An enzyme is denatured when

  2. 2. Benedict's solution tests for

  3. 3. Arteries have thick muscular walls because they

  4. 4. A double circulatory system means blood passes through the heart

16

Lesson round-up

Part 16 of 16

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 16 · Watch & discover

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