GCSE · Biology · Edexcel · Spec 1BI0

Insulin control of blood glucose

You've just finished a sugary snack. Where does all that sugar go, and who tells the body what to do with it?

Biology · Blood glucose

Follow a sugary snack round the loop

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

Stage 1: You eat or drink something sugary
Foods and drinks containing sugar or carbohydrates make blood glucose concentration rise.
Stage 3: The pancreas secretes insulin
The pancreas is a gland, and insulin is one of the hormones it secretes.
Stage 6: Blood glucose falls back to normal
Until the next meal raises it again, and the loop starts over.

…and stage 6 leads back to stage 1.

Exam line: Say the stages in order: rise, detection by the pancreas, insulin secreted, carried in the plasma, absorbed and stored as glycogen, level back to normal.

Exercise

Reason it through

Why does blood glucose concentration fall when you exercise?

Link 1 of 4

First link · your turn

What are your muscles doing when you exercise?

Locked — reveal the link above first

Biology · Blood glucose

Which idea is closest to yours?

You've had a sugary snack, your blood glucose has risen, and the pancreas has secreted insulin.

Which is closest to what you think insulin does?

Insulin breaks the glucose down, so it's destroyed.Insulin makes cells absorb glucose, and the liver turns the excess into glycogen.Glycogen is a hormone that the pancreas secretes.Glycogen and glucagon are the same thing.

How sure are you?

I'm sureI think soI'm guessing

Insulin breaks the glucose down, so it's destroyed.

This is a common misconception

It's a tempting picture, because the level does fall. But nothing is destroyed. Insulin makes cells absorb more glucose from the blood and makes the liver turn the excess into glycogen. The glucose has been moved and stored.

Insulin makes cells absorb glucose, and the liver turns the excess into glycogen.

This matches the evidence

Exactly. Absorbed by cells, stored as glycogen, and that is why the blood glucose level falls back to normal.

Glycogen is a hormone that the pancreas secretes.

This is a common misconception

The pancreas does secrete hormones, but glycogen isn't one. Glycogen is a stored form of glucose, found in liver and muscle cells. The pancreas secretes insulin and glucagon.

Glycogen and glucagon are the same thing.

This is a common misconception

One letter apart, which is why they get mixed up. Glycogen is the store of glucose in liver and muscle cells. Glucagon is a hormone: insulin's partner hormone from the pancreas.

Glucose is the sugar in the blood, insulin is the instruction, glycogen is the store, and glucagon is insulin's partner hormone.

Why the range is narrow

Blood glucose too highvsBlood glucose too low

Same organ, two directions.

Focus

What the pancreas detects

Blood glucose too high

An increase in blood glucose concentration

Blood glucose too low

A decrease in blood glucose concentration

The insight

It's the same organ doing the detecting, just reading two different directions.

Hormone secreted

Blood glucose too high

Insulin

Blood glucose too low

Glucagon, insulin's partner hormone

Aim

Blood glucose too high

Bring the level back down to normal

Blood glucose too low

Bring the level back up to normal

Danger if it isn't controlled

Blood glucose too high

If it stays high for a long time, organs can stop functioning properly

Blood glucose too low

A person could fall into a coma, which can be fatal

Biology · Blood glucose

Write it, then mark it

Explain how insulin returns a high blood glucose concentration to normal. [4 marks]

Your answer

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

The mark scheme

The pancreas detects the rise in blood glucose concentration (and secretes insulin) (1 mark)
Insulin travels in the blood plasma to its target cells in the liver and muscles (1 mark)
Insulin causes cells to absorb more glucose from the blood (1 mark)
Insulin causes the liver to turn excess glucose into glycogen, which is stored in liver and muscle cells (1 mark)

Model answer

The pancreas detects that blood glucose concentration is too high and secretes insulin. Insulin travels in the blood plasma to its target cells in the liver and muscles. It causes cells to absorb more glucose from the blood, and it causes the liver to turn excess glucose into glycogen, which is stored in liver and muscle cells. As a result, the blood glucose level falls back to normal.

Four steps to name: detect, travel, absorb, store.

Exam line: Don't jump from 'insulin' to 'glucose goes down'. Name detection, transport, absorption and storage in order.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Insulin doesn't destroy glucose. It moves it.

What you need to know

Glucose is a sugar carried in the blood plasma to your cells, which use it for respiration, even when you're resting.
Homeostasis is regulating internal conditions so enzymes and cells work at their best. Blood glucose concentration is one of them.
Blood glucose rises after you eat or drink something sugary or carbohydrate-rich. It falls during fasting and during exercise.
Have a goYour mate Jo says a can of fizzy drink will make your blood glucose fall. Back her up, or put her right?
Put her right: it makes blood glucose rise.
Drinks and foods containing sugar or carbohydrates raise blood glucose concentration. Fasting and exercise are what lower it.
The pancreas is the organ that detects changes in blood glucose. It's a gland that secretes the hormones insulin and glucagon.
When blood glucose is too high, the pancreas secretes insulin. It travels in the blood plasma to target cells in the liver and muscles.
Have a goInsulin is secreted by the pancreas but acts somewhere else. Which target cells does it travel to: liver and muscles, or brain and lungs?
Liver and muscles, carried in the blood plasma.
Those are the target cells for insulin, so that is where it has its effect.
Insulin makes cells absorb more glucose from the blood and makes the liver turn excess glucose into glycogen. The level falls back to normal.
Have a goInsulin has done its job and the blood level is back to normal. Was the extra glucose destroyed, or moved?
Moved: absorbed by cells, with the excess turned into glycogen by the liver.
Insulin doesn't break glucose down. It causes absorption and storage, which is why the blood level falls.
Glycogen is a stored form of glucose, found in liver and muscle cells. It is not a hormone.
The pancreas also detects falls and secretes glucagon, insulin's partner hormone. Together they keep blood glucose within an ideal range.
Too low, and a person could fall into a coma, which can be fatal.
Stays high for a long time, and organs can stop functioning properly.

The big picture

After you eat, blood glucose concentration rises. The pancreas detects the rise and secretes insulin, which travels in the blood plasma to target cells in the liver and muscles. Insulin makes cells absorb glucose and makes the liver turn excess glucose into glycogen, so the level falls back to normal. Keeping blood glucose within narrow limits matters because too low or too high for too long is dangerous.

Key points

1The pancreas detects changes in blood glucose concentration and secretes insulin when it is too high.

2Insulin travels in the blood plasma to target cells in the liver and muscles.

3Insulin causes cells to absorb more glucose, and causes the liver to turn excess glucose into glycogen, so the level falls back to normal.

4Glycogen is a stored form of glucose in liver and muscle cells. Glucagon is insulin's partner hormone.

5Keeping blood glucose within narrow limits matters: too low risks a coma, and high for a long time can stop organs functioning properly.

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Worked example

Problem

A question says: 'The pancreas does not secrete insulin after a meal. Explain what happens to blood glucose.' Plan your answer.

⚠ Watch out

Saying insulin 'breaks down' or 'destroys' glucose. It makes cells absorb glucose and makes the liver turn the excess into glycogen. Also don't mix up glycogen (the store) with glucagon (the partner hormone).

🧠

Memory hook

Insulin is the instruction to bank the glucose: cells absorb it, and the liver stores the excess as glycogen.

✓

Check yourself

Without looking back: which organ detects a rise in blood glucose, and what two things does insulin then cause?

Flashcards

(12)

What is glucose, and what do cells use it for?

A sugar that travels in the blood plasma and is delivered to cells for respiration.

Why do cells need a constant supply of glucose, even at rest?

They need it for respiration all the time.

What is homeostasis?

Regulating internal conditions to maintain optimum conditions for enzyme action and all cell functions.

Name two things that make blood glucose fall.

Fasting and exercise.

What makes blood glucose concentration rise?

Eating or drinking foods containing sugar or carbohydrates.

Which organ detects changes in blood glucose concentration?

The pancreas, a gland that secretes the hormones insulin and glucagon.

What is glycogen, and where is it found?

A stored form of glucose, found in liver and muscle cells.

What does the pancreas secrete when blood glucose is too high, and where does it go?

Insulin, which travels in the blood plasma to target cells in the liver and muscles.

What does insulin cause cells and the liver to do?

Cells absorb more glucose from the blood, and the liver turns excess glucose into glycogen.

Does insulin break glucose down?

No. It causes absorption and storage as glycogen, so the blood glucose level falls back to normal.

What is glucagon?

Insulin's partner hormone, also secreted by the pancreas.

Why must blood glucose stay within narrow limits?

Too low and a person could fall into a coma, which can be fatal. High for a long time and organs can stop functioning properly.

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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Follow a sugary snack round the loop

Which idea is closest to yours?

Write it, then mark it

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