Explain the role of digestion

Hi,
Alisha's reply is slightly but crucially incorrect - it should read "so they are easier to absorb", simply because you cannot "digest" twice!

A bit more detail would also probs help OP. DIGESTION IS THE PROCESS THAT BREAKS DOWN LARGE MOLECULES OF FOOD INTO SMALLER MOLECULES. Large carbohydrate molecules like starch (from plant food) and glycogen (from animal food) are broken down into e.g. maltose [= malt sugar](a combination of two glucose molecules = a disaccharide) then into glucose [= simple sugar](a monosaccharide - (I know what you are thinking right now - C.......A.........D...........B. ...........B..................U. ...................R............ ...........Y.................... ............S chocolate - yummy! but don't rush to your mum's fridge just yet! - ok that contains sucrose [= cane sugar] [=another disacchardide, made by combining [again] two monosaccharides, but this time one glucose and one fructose [= fruit sugar]]).

Similarly, proteins are broken down into amino acids.

You are happy with the fact that glucose & amino acids are smaller molecules than starch and protein, respectively, yeah? Ok good cool! So the cell membrane of the cells of the inner layer of the small intestine (called endothelium) has pores that are small so only let small molecules to go through them into the blood. Still with me?....................Good!

Now I can see you are beginning to smile as you are thinking "On yeah - I got it now!" - yes well done!, the small glucose and amino acids can now get into your blood, which the large proteins and starch could not. Happy?

NOW you are laughing out loud (!) - easy peasy lemon squeezy, yeah?

M (specialist biology tutor)