GCSE · Biology · AQA · Spec 8461

Control of blood glucose and diabetes

Something in your body keeps a constant eye on the glucose in your blood and steps in whenever it drifts. What is it, and what happens when it stops doing its job?

Rebuild it, then break it

The blood glucose loop

3 stages are missing. Use the rest of the loop to work out which goes where.

  1. Stage 1: Blood glucose concentration rises

    The pancreas monitors blood glucose concentration, so it detects the change.

  3. Stage 3: Glucose moves from the blood into cells

    Insulin causes this. Glucose leaves the blood and goes into the body's cells.

  5. Stage 5: Blood glucose concentration falls

    Glucose has left the blood, so there is less of it there and the concentration comes down.

  7. Stage 7: Glycogen is converted to glucose and released into the blood (Higher)

    Glucagon causes this. The stored glycogen becomes glucose again, the glucose goes back into the blood, and the concentration rises: round to stage 1.

…and stage 7 leads back to stage 1.

Exam line: Name the trigger AND the response: 'blood glucose is too high, so the pancreas produces insulin, which causes glucose to move from the blood into the cells.'

Four words that look alike

Which is which?

Tick every description that is true for each word. Then check your grid.

Glucose
Insulin
Glucagon (Higher)
Glycogen

Exam line: Spell it out every time: glucaGON is a hormone; glycoGEN is the store.

Without diabetes: the rise comes back down

02468036912TimeBlood glucose concentration(4, 4.6)

Time: 4. Blood glucose concentration: 4.6

Drag the point along the curve. Find where the concentration starts to rise, where it peaks, and where it's back to its starting level.

Exam line: Describe the shape, then explain it: 'the concentration rises, then falls back to its starting level, because the pancreas produces insulin, which causes glucose to move from the blood into cells.'
Watch out: The numbers here are an illustrative relative scale, not real measurements. What matters is the shape: up, then back down to where it started.

Type 1 diabetes: the rise stays high

02468036912TimeBlood glucose concentration(4, 10.3)

Time: 4. Blood glucose concentration: 10.3

Now drag along this one and compare. Does it start at the same level as before? How high does it climb? Does it ever come back down?

Exam line: Comparing two graphs? Quote the difference: 'without diabetes the concentration returns to its starting level; with Type 1 diabetes it stays high.'
Watch out: Same illustrative scale as the graph above, so you can compare the two shapes directly. Don't treat the numbers as real readings.

Type 1 vs Type 2

Type 1 diabetesvsType 2 diabetes

Read the first row first. Everything else follows from it.

Focus

What goes wrong

Type 1 diabetes

The pancreas fails to produce enough insulin.

Type 2 diabetes

The pancreas still produces insulin, but the body cells no longer respond to it.

The insight

The quickest way to tell them apart: in Type 1 the insulin is missing; in Type 2 the insulin is there, but the cells ignore it.

Where the loop breaks

Type 1 diabetes

At stage 2: the pancreas producing insulin.

Type 2 diabetes

At stage 3: glucose moving from the blood into cells.

Usual treatment

Type 1 diabetes

Normally treated with insulin injections.

Type 2 diabetes

A carbohydrate-controlled diet and an exercise regime are common treatments.

Risk factor to know

Type 1 diabetes

None to learn for this topic.

Type 2 diabetes

Obesity is a risk factor.

Your turn

Write it, then mark it

Explain how insulin controls blood glucose concentration when it is too high. Higher: also explain how glucagon works with insulin to keep blood glucose constant. [6 marks]

0 words · your answer stays on this page and is not sent anywhere.

Exam line: Every step needs its own sentence: too high, pancreas, insulin, into cells, glycogen. A missing link is a missing mark.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Your pancreas keeps watch on the glucose in your blood and steps in when it rises too high. Learn that loop once, and diabetes stops being a separate topic: it's the same loop with one part broken.

What you need to know

  • The pancreas monitors blood glucose. Too high: it produces insulin, which causes glucose to move from the blood into cells.
  • Liver and muscle cells convert excess glucose into glycogen, a store. Glycogen is not a hormone.
  • (Higher) Too low: the pancreas produces glucagon, which turns glycogen back into glucose and releases it into the blood.
  • Type 1: the pancreas fails to produce enough insulin. Type 2: the body cells no longer respond to insulin.

The big picture

The pancreas monitors and controls blood glucose concentration. Too high, and it produces insulin, which causes glucose to move from the blood into cells; liver and muscle cells store the excess as glycogen. (Higher) Too low, and it produces glucagon, which converts glycogen back into glucose and releases it into the blood: the two hormones form a negative feedback cycle. In Type 1 diabetes the pancreas fails to produce enough insulin (normally treated with insulin injections). In Type 2 the body cells no longer respond to insulin (commonly treated with a carbohydrate-controlled diet and exercise; obesity is a risk factor).

Key points

1Blood glucose concentration is monitored and controlled by the pancreas, and the hormone insulin helps to keep blood sugar level constant.
2If blood glucose concentration is too high, the pancreas produces insulin. Insulin causes glucose to move from the blood into the cells.
3In liver and muscle cells, excess glucose is converted to glycogen for storage.
4(Higher) If blood glucose concentration is too low, the pancreas produces glucagon. Glucagon causes glycogen to be converted into glucose and released into the blood.
5(Higher) Insulin and glucagon work in a negative feedback cycle: too high triggers insulin, too low triggers glucagon, and each response reverses the change that triggered it.
6Type 1 diabetes: the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections.
7Type 2 diabetes: the body cells no longer respond to the insulin the pancreas produces. A carbohydrate-controlled diet and an exercise regime are common treatments, and obesity is a risk factor.

Worked example

Problem

A person with Type 1 diabetes has a high blood glucose concentration that isn't coming back down. Explain why it stays high, and why an insulin injection helps.

⚠ Watch out

Mixing up glucagon and glycogen. Glucagon is a hormone the pancreas produces when blood glucose is too low (Higher). Glycogen is the store that liver and muscle cells make from excess glucose. They're only a few letters apart but do completely different jobs, so check which one you've written.

🧠

Memory hook

INsulin sends glucose INto cells. GlucaGON is called up when glucose has GONE too low. GlycoGEN is the store. And diabetes? Type 1: insulin missing. Type 2: insulin ignored.

✓

Check yourself

Without looking back: blood glucose is too high. Say each stage of what happens next, in order. Then say which stage breaks in Type 1 diabetes and which breaks in Type 2.

Flashcards

(13)
Which organ monitors and controls blood glucose concentration?
The pancreas.
Blood glucose is too high. Which hormone does the pancreas respond with?
Insulin.
What does insulin cause glucose to do?
Move from the blood into the cells.
What happens to excess glucose in liver and muscle cells?
It's converted to glycogen for storage.
Is glycogen a hormone?
No. Glycogen is a store, made from excess glucose in liver and muscle cells. The hormones here are insulin and glucagon.
(Higher) What does the pancreas produce when blood glucose concentration is too low?
The hormone glucagon.
(Higher) What does glucagon cause?
Glycogen to be converted into glucose and released into the blood.
(Higher) Why is blood glucose control called negative feedback?
Each change triggers the response that reverses it: too high triggers insulin, too low triggers glucagon.
What goes wrong in Type 1 diabetes?
The pancreas fails to produce enough insulin, so blood glucose levels are uncontrolled and high.
How is Type 1 diabetes normally treated?
With insulin injections.
What goes wrong in Type 2 diabetes?
The body cells no longer respond to the insulin the pancreas produces.
What are common treatments for Type 2 diabetes?
A carbohydrate-controlled diet and an exercise regime.
Name a risk factor for Type 2 diabetes.
Obesity.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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