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
- 20 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 20
Visual introductionPicture this
Enzymes, digestion and the circulatory system
Organisation is the study of how cells build tissues, organs and systems that keep a large organism supplied.
In a nutshell
Explain cell structure, transport, enzyme action and bioenergetics at GCSE standard.
Learning cycle
Part 2 of 20
Learning cycle 1 of 2
Part 1 · Enzyme action
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 20
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.
Reset break
Part 4 of 20
Pause
That's sitting 1 of 5 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.
Explore the idea
Part 5 of 20
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.
Quick check
Part 6 of 20
Quick check
Part 7 of 20
Reset break
Part 8 of 20
Pause
That's sitting 2 of 5 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.
Learning cycle
Part 9 of 20
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.
Explore the idea
Part 10 of 20
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.
Quick check
Part 11 of 20
Reset break
Part 12 of 20
Pause
That's sitting 3 of 5 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.
Quick check
Part 13 of 20
Explore the idea
Part 14 of 20
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).
Challenge round
Part 15 of 20
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
Reset break
Part 16 of 20
Pause
That's sitting 4 of 5 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.
Challenge round
Part 17 of 20
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.
Challenge round
Part 18 of 20
Game · Recall cards
An enzyme is denatured when
Card 1 of 4
Mastery quiz
Part 19 of 20
Marked quiz
End of lesson quiz: Enzymes, digestion and the circulatory system
4 questions, marked with the reasoning shown. No timer.
1. An enzyme is denatured when
2. Benedict's solution tests for
3. Arteries have thick muscular walls because they
4. A double circulatory system means blood passes through the heart
Lesson round-up
Part 20 of 20
Lesson round-up
Ready when you are
Quiz score
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Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaPart 1 of 20 · Watch & discover