Absorption and Transport of Nutrients — Revision notes

Absorption

When small, soluble food molecules pass through the wall of the small intestine and into the blood

Digestion

The mechanical and chemical processes that break large pieces of food down into small ones

Insoluble

Describes a substance that won't dissolve and is too large to pass through the intestine wall

Soluble

Describes a substance that dissolves and is small enough to move through the intestine wall

Small intestine

The long, narrow tube where most digestion and almost all absorption of nutrients take place

Villi

Tiny finger-like folds lining the small intestine that massively increase its surface area

Surface area

The total area of a surface; increasing it increases the rate of absorption

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration

Concentration gradient

The difference in concentration between two areas that causes particles to diffuse

Circulatory system

The heart and network of blood vessels that carries blood around the body

Plasma

The straw-coloured liquid part of blood that nutrients and waste products dissolve into

Glucose

A soluble nutrient absorbed into the blood and used mainly for energy

Amino acids

Soluble nutrients absorbed into the blood and rebuilt into proteins for growth and repair

Fatty acids

Soluble nutrients absorbed into the blood, released from digested fats

Glycerol

A soluble nutrient absorbed alongside fatty acids from digested fats

Fibre

A substance that's never digested into small soluble nutrients, so it never reaches the blood

Red blood cells

Cells carried in the plasma that pick up oxygen and carry it around the body

White blood cells

Cells carried in the plasma that fight infection

Platelets

Tiny cell fragments carried in the plasma that help blood clot

What this lesson covers

How well do you know each one? Be honest: red means go back over it.

• Explain why food must be broken into small soluble molecules before absorptionNot yetSort ofGot it
• Explain the difference between soluble and insoluble nutrientsNot yetSort ofGot it
• Describe how villi are adapted to absorb nutrientsNot yetSort ofGot it
• Explain how diffusion moves nutrients from the small intestine into the bloodNot yetSort ofGot it
• Explain what a concentration gradient is and why it matters for absorptionNot yetSort ofGot it
• Trace a nutrient's journey from food to a body cell via the circulatory systemNot yetSort ofGot it

Test yourself

Cover the answer, say it out loud, then check the full quiz on the lesson page.

• What are the tiny folds in the lining of the small intestine called?
• Nutrients diffuse into the blood because blood has what, compared to the gut?
• Which one of these is not dissolved in your blood plasma?

Topic quiz

13 questions on this topic only — not mixed with anything else, one at a time.

Spelling challenge

Read the definition, then type the correct spelling of the term. Uses the same terms as above.