Lesson 2

Digestion & Absorption

Absorption & the Structure of Villi

🥣

→ABSORPTION

🩸⚡ INTO BLOOD ⚡

Today you become an
absorption engineer.Discover how digested food gets into every cell.

Learning Objective:

2.32 – Understand how the small intestine is adapted for absorption, including the structure of a villus.

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Teacher Print Tools – Lesson 2

Arrival Task

Arrival Task – Recall from Last Week (Enzymes & Bile)

Instructions: Answer from memory. Q1–3 recall last week. Q4 leads into today.

1. Enzymes (Recall)

Name the enzyme that breaks starch into maltose.

Amylase.

2. Lipids (Recall)

What two products does lipase make from lipids?

Fatty acids and glycerol.

3. Bile (Recall)

Where is bile produced and where is it stored?

Produced in the liver. Stored in the gallbladder.

4. Lead-in: Absorption

Once food is digested into small molecules, where does it enter the blood?

The small intestine (specifically the ileum).

1. Enzymes (Recall)

Complete: Starch → ______ by amylase → ______ by maltase.

Maltose, then glucose.

2. Proteases (Recall)

Name the protease from the stomach and the one from the pancreas.

Pepsin (stomach), trypsin (pancreas).

3. Bile (Recall)

Explain the two roles of bile in digestion.

1) Neutralises stomach acid for alkaline conditions. 2) Emulsifies fats, increasing SA:V for lipase.

4. Lead-in: Absorption

Digested food passes into the bloodstream. What is this process called, and in which part of the small intestine?

Absorption. In the ileum.

1. Enzymes (Recall)

Explain why starch digestion requires two separate enzymes.

Amylase breaks starch to maltose. Maltase breaks maltose to glucose. Each enzyme is specific to one substrate.

2. Bile (Recall)

Explain why bile must neutralise stomach acid before intestinal enzymes can work.

Intestinal enzymes have alkaline optimum pH. Acid would denature them by changing active site shape.

3. Emulsification (Recall)

Explain how emulsification increases digestion rate. Use SA:V.

Breaks large fat droplets into smaller ones, increasing SA:V. More surface for lipase to bind, so more fat digested per second.

4. Lead-in: Absorption

The ileum must maximise surface area and minimise diffusion distance. Suggest why.

More SA = more nutrients absorbed at once. Short distance = faster crossing. Both maximise absorption rate.

Starter

Starter: Recap from Lesson 1

Instructions: Answer from memory – no notes! This checks what you remember from last lesson.

1. Name the enzyme that breaks starch into maltose.

2. What does lipase break lipids into? (Two products)

3. Where is bile produced? Where is it stored?

4. What does bile do to fat droplets? (What is this process called?)

5. Predict: Once food is digested into small soluble molecules, how do you think these molecules get from the gut into the blood?

Q5: think about the wall of the small intestine. It's THIN and has BLOOD nearby. So the food can pass through... how?

Key Words: amylase, maltase, protease, lipase, bile, liver, gallbladder, emulsification, SA:V

I Do

I Do: What is Absorption? (Spec 2.32)

Key Idea: Once food is digested into small soluble molecules, it must be absorbed into the blood. This happens in the ileum.

What is absorption?

Absorption = digested food molecules passing through the wall of the ileum (small intestine) into the bloodstream.

Only small, soluble molecules can be absorbed – that’s why digestion must happen first!

Two absorption methods:

1. Diffusion – passive, no energy needed. Molecules move from high concentration (gut) to low concentration (blood).

2. Active transport – uses energy (ATP) to move molecules against the gradient, ensuring maximum absorption even when concentrations equalise.

Absorption in the Ileum

🧠 Memory Trick: "Diffusion is free (passive). Active transport costs energy." Think of diffusion as rolling downhill, active transport as pushing uphill – you need ATP fuel!

🔬 Inside a Villus — Live View

⬇ Gut side (HIGH) Blood side (LOW)

VILLUSfinger-shaped

Glucose

Amino Acid

Fatty Acid

🟡 Microvilli sparkle = ↑ SA 🔵 Glucose + amino acid → capillary🟢 Fatty acid → lacteal

⚠️ Diffusion vs Active Transport

Diffusion

Free — high → low
(no ATP)

Active Transport

⚡

Costs ATP — uphill
(against gradient)

Memory trick: "Downhill = free. Uphill = ATP."

We Do

We Do: Absorption Process Sort

Instructions: Sort each fact into Diffusion or Active Transport.

Score: 0/6

Passive – no energy needed

Needs energy (ATP)

High to low concentration

Against the concentration gradient

Like rolling downhill

Like pushing uphill

✅ Diffusion

⚡ Active Transport

I Do

I Do: How Are Villi Adapted? (Spec 2.32)

Key Idea: The ileum wall is folded into millions of finger-like villi to massively increase surface area. Each villus has 5 key adaptations.

📏

1. Large SA – millions of villi increase surface area. More SA = more absorption at once.

🔬

2. Microvilli – tiny projections on each villus further increase SA.

🩸

3. Blood supply – dense capillary network carries nutrients away, maintaining a steep concentration gradient.

📄

4. One cell thick – short diffusion pathway so nutrients cross faster.

🥛

5. Lacteals – special vessels inside villi that absorb fats.

Structure of a Villus

Aspire: Why do villus epithelial cells need lots of mitochondria?

5 Adaptations — see them in action 🎬

📏

Large SA

Millions of villi

🔬

Microvilli

Tiny projections ↑ SA more

🩸

Blood supply

Steep gradient

📄

One cell thick

Short diffusion path

🥛

Lacteals

Absorb fats

Examiners love this phrase: "adapted by [feature] which [function] so that [absorption effect]"

Two link words = top marks: name the feature, state what it does, link to absorption rate.

We Do

We Do: Label the Villus & Match Adaptations

Instructions: As a class – Part A: Select a label, then click the correct spot on the diagram. Part B: Match each adaptation to why it helps.

Score: 0/10

Part A: Label the Villus

Microvilli

One cell thick

Blood capillary

Lacteal

Villus

✏️ Trace the pathway: Once labelled, draw the path of a glucose molecule (→ capillary) vs a fat molecule (→ lacteal). Use your whiteboard pen!

Part B: Match Adaptation → Reason

📏 Large SA

📄 One cell thick

🩸 Blood supply

🥛 Lacteals

⚡ Active transport

More nutrients absorbed at once

Short diffusion pathway

Maintains steep concentration gradient

Absorb fats from intestine

Moves nutrients against gradient using energy

Independent Work

Independent Work – Absorption & Villi

Instructions: Complete your Lesson 2 worksheet. Use your labelled villus diagram and knowledge organiser.

Independent Work Timer

08:00

Foundation (Grades U–1)

MCQ + short answer on villi adaptations and absorption.

Middle (Grades 2–3)

Table completion, short answer, and 4-mark exam questions.

Higher (Grades 3–5)

Extended response including a 6-mark coeliac disease question.

🔗 What if? A disease destroys all the mitochondria in the villi. Which type of absorption stops, and why? (Link back to Lesson 1.)

📋 Scaffolding

Labelled villus diagram, adaptation checklist, and key word glossary in your pack.

🏆 Success Criteria

Foundation (U–1): Name where absorption occurs, list 3 adaptations, state what lacteals do.

Middle (2–3): Explain how each adaptation helps, describe diffusion and active transport.

Higher (3–5): Link SA:V and gradients to rate, evaluate how damaged villi cause malnutrition.

Exit Ticket

Exit Ticket – Lesson 1–2 Cumulative

Instructions: 6 questions covering the Digestive System, Enzymes & Bile, and Absorption & Villi. No notes.

Digestive System

1) Name the muscular action that pushes food through the gut.

Peristalsis.

Digestive System

2) What does the large intestine absorb?

Water.

Enzymes

3) What does amylase break starch into?

Maltose.

Bile

4) Where is bile stored?

The gallbladder.

Enzymes

5) What does lipase produce?

Fatty acids and glycerol.

Villi

6) Name two adaptations of villi.

Any two: large SA, microvilli, one cell thick, blood supply, lacteals.

Knowledge Organiser (L1-L2): Digestion & Absorption

Concept	Details
Amylase	Starch → maltose. Salivary glands & pancreas.
Maltase	Maltose → glucose.
Protease	Proteins → amino acids. Pepsin (stomach), trypsin (pancreas).
Lipase	Lipids → fatty acids & glycerol. Pancreas.
Bile	Produced: liver. Stored: gallbladder. NOT an enzyme.
Bile Job 1	Neutralises stomach acid → alkaline pH for enzymes.
Bile Job 2	Emulsifies fats → increases SA:V for lipase.
Absorption	Food → blood in ileum. Diffusion + active transport.
Villi	Finger-like projections increasing SA for absorption.
Adaptations	Large SA, microvilli, one cell thick, blood supply, lacteals.
Lacteals	Vessels inside villi that absorb fats.

Lesson 2 Arrival Task

Foundation (U–1)

1. Enzymes (Recall)

Name the enzyme that breaks starch into maltose.

2. Lipids (Recall)

What two products does lipase make from lipids?

3. Bile (Recall)

Where is bile produced and where is it stored?

4. Lead-in: Absorption

Once food is digested into small molecules, where does it enter the blood?

Middle (2–3)

1. Enzymes

Complete: Starch → ______ by amylase → ______ by maltase.

2. Proteases

Name the protease from the stomach and the one from the pancreas.

3. Bile

Explain the two roles of bile in digestion.

4. Lead-in: Absorption

Digested food passes into the bloodstream. What is this process called, and in which part of the small intestine?

Higher (3–5)

1. Enzymes

Explain why starch digestion requires two separate enzymes.

2. Bile

Explain why bile must neutralise stomach acid before intestinal enzymes can work.

3. Emulsification

Explain how emulsification increases digestion rate. Use SA:V in your answer.

4. Lead-in: Absorption

The ileum must maximise surface area and minimise diffusion distance. Suggest why.

Lesson 2 Starter: Recap from Lesson 1

Answer from memory:

1) Name the enzyme that breaks starch into maltose.

2) What does lipase break lipids into?

3) Where is bile produced? Where is it stored?

4) What does bile do to fat droplets?

5) Predict: How do digested molecules get from gut to blood?

Lesson 2 We Do 1: Diffusion vs Active Transport

Write each fact in the correct column:

Diffusion	Active Transport

Lesson 2 We Do: Label & Match

Part A: Label these features on the villus diagram above (if not done already).

Part B: Match each adaptation to why it helps absorption:

Adaptation	Why it helps
Large surface area
One cell thick
Good blood supply
Lacteals
Active transport

Lesson 2 Scaffolding – Foundation (Grades U–1)

Villus Adaptations

1. Large SA – millions of villi.

2. Microvilli – further increase SA.

3. One cell thick – short diffusion pathway.

4. Blood supply – steep concentration gradient.

5. Lacteals – absorb fats.

Uses: diffusion + active transport.

Sentence Starters

Absorption happens in the...

Villi increase absorption because...

The wall is one cell thick so that...

Lesson 2 Scaffolding – Middle (Grades 2–3)

Key Facts

Absorption: ileum. Diffusion + active transport.

5 adaptations: SA, microvilli, thin wall, blood supply, lacteals.

Lesson 2 Scaffolding – Higher (Grades 3–5)

Key Terms

Absorption, villus, microvilli, lacteal, diffusion, active transport, concentration gradient, SA:V

Lesson 2 Independent Work – Foundation (Grades U–1)

Part A: Multiple Choice

1) Food is absorbed in the: A) Stomach B) Duodenum C) Ileum D) Colon

2) Lacteals absorb: A) Water B) Glucose C) Fats D) Amino acids

3) Villus wall thickness: A) 5 cells B) One cell C) 10 cells D) 3 cells

4) Absorption uses diffusion and: A) Osmosis B) Active transport C) Peristalsis D) Evaporation

Part B: Short Answer

5) Name three adaptations of villi.

6) What are microvilli?

7) Why is a good blood supply important?

Part C: Long Answer

8) Describe how food is absorbed in the small intestine. Name the structures and processes involved.

Part D: Exam Question [3 marks]

9) Explain why villi increase the rate of absorption. Include how they are adapted. [3]

Lesson 2 Independent Work – Middle (Grades 2–3)

Part A: Multiple Choice

1) Blood supply helps villi because it: A) Keeps them warm B) Maintains concentration gradient C) Makes enzymes D) Produces ATP

2) Active transport needs: A) Gravity B) Energy C) Sunlight D) Oxygen

3) The ileum is part of the: A) Stomach B) Large intestine C) Small intestine D) Liver

Part B: Short Answer

4) Complete this table:

Adaptation	How it helps
Villi
One cell thick
Blood supply
Lacteals

5) Explain the difference between diffusion and active transport.

Part C: Long Answer

6) Explain why both diffusion and active transport are needed for absorption in the ileum.

Part D: Exam Question [4 marks]

7) Describe how the structure of a villus makes it adapted for absorbing digested food. [4]

Lesson 2 Independent Work – Higher (Grades 3–5)

Part A: Multiple Choice

1) Active transport is needed because: A) Diffusion is too slow B) Diffusion stops at equilibrium C) Blood flows too fast D) Villi are too small

2) A patient with flattened villi would experience: A) Better absorption B) Reduced absorption C) No change D) More villi

Part B: Short Answer

3) Explain how blood supply maintains a steep concentration gradient.

4) Why do cells in the ileum wall need lots of mitochondria?

Part C: Long Answer

5) Explain why both diffusion and active transport are essential. What would happen if only one process was available?

Part D: Exam Question [6 marks]

6) A person with coeliac disease has flattened villi. Explain how this affects nutrient absorption and could cause malnutrition. Link to specific adaptations of healthy villi. [6]

Lesson 2 Exit Ticket – Cumulative (Foundation U–1)

Digestive System

1) Name the muscular action that pushes food through the gut.

Digestive System

2) What does the large intestine absorb?

Enzymes

3) What does amylase break starch into?

Bile

4) Where is bile stored?

Enzymes

5) What does lipase produce?

Villi

6) Name two adaptations of villi.

Lesson 2 Exit Ticket – Cumulative (Middle 2–3)

Digestive System

1) Name both parts of the small intestine and one function of each.

Enzymes

2) Starch → _____ → _____. Name both enzymes.

Enzymes

3) Name the protease from the stomach.

Bile

4) Explain one role of bile.

Villi

5) Why is a good blood supply important in villi?

Absorption

6) Name both absorption processes.

Lesson 2 Exit Ticket – Cumulative (Higher 3–5)

Digestive System

1) Why does peristalsis work upside down?

Enzymes

2) Why does starch need two enzymes?

Bile

3) How does emulsification increase digestion rate?

Absorption

4) Why is active transport needed alongside diffusion?

Villi

5) Why is "one cell thick" important for absorption?

Synthesis

6) Trace glucose from bread to the bloodstream.

TA Focus

Cold Call

Lesson 2 Complete!

Digestion & Absorption

Teacher Print Tools – Lesson 2

Arrival Task – Recall from Last Week (Enzymes & Bile)

1. Enzymes (Recall)

2. Lipids (Recall)

3. Bile (Recall)

4. Lead-in: Absorption

1. Enzymes (Recall)

2. Proteases (Recall)

3. Bile (Recall)

4. Lead-in: Absorption

1. Enzymes (Recall)

2. Bile (Recall)

3. Emulsification (Recall)

4. Lead-in: Absorption

Starter: Recap from Lesson 1

I Do: What is Absorption? (Spec 2.32)

What is absorption?

Two absorption methods:

Absorption in the Ileum

🔬 Inside a Villus — Live View

⚠️ Diffusion vs Active Transport

Diffusion

Active Transport

We Do: Absorption Process Sort

✅ Diffusion

⚡ Active Transport

I Do: How Are Villi Adapted? (Spec 2.32)

Structure of a Villus

5 Adaptations — see them in action 🎬

We Do: Label the Villus & Match Adaptations

🏆 Quick Wins (first to finish)

Independent Work – Absorption & Villi

Foundation (Grades U–1)

Middle (Grades 2–3)

Higher (Grades 3–5)

📋 Scaffolding

🏆 Success Criteria

Exit Ticket – Lesson 1–2 Cumulative

Knowledge Organiser (L1-L2): Digestion & Absorption

Lesson 2 Arrival Task

Foundation (U–1)

Middle (2–3)

Higher (3–5)

Lesson 2 Starter: Recap from Lesson 1

Lesson 2 We Do 1: Diffusion vs Active Transport

Lesson 2 We Do: Label & Match

Lesson 2 Scaffolding – Foundation (Grades U–1)

Villus Adaptations

Sentence Starters

Lesson 2 Scaffolding – Middle (Grades 2–3)

Key Facts

Lesson 2 Scaffolding – Higher (Grades 3–5)

Key Terms

Lesson 2 Independent Work – Foundation (Grades U–1)

Lesson 2 Independent Work – Middle (Grades 2–3)

Lesson 2 Independent Work – Higher (Grades 3–5)

Lesson 2 Exit Ticket – Cumulative (Foundation U–1)

Lesson 2 Exit Ticket – Cumulative (Middle 2–3)

Lesson 2 Exit Ticket – Cumulative (Higher 3–5)

We Do – Class Evidence