These Q Cards are important facts on AQA Biology AS.


2.1- Enzymes & Digestion

Digestive System

  • food goes into mouth, teeth chews and breaks it into pieces.
  • Salivary glands contains enzymes; - amylase breaks starch- maltose
  • Oesophagus (thick muscular wall) carries food from mouth-stomach. Muscular contractions help bring the food down to stomach.
  • Cardiac sphincter- (oesophagus-stomach). Allows food to go into stomach but back up.
  • Stomach- (muscular sac) produces enzymes/ stores/break food into liquidy mixture; down S.I
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2.1- Enzymes & Digestion

Digestive System

  • Small intestine/Illeum- (muscular tube) breaks down food/ absorbs carbohydrates, proteins, minerals, vitamins and fats.
  • Pancreas- makes juices which help body digest fats/proteins
  • Gallbladder- stores BILE when the body needs it.
  • Liver- Bile helps absorb fats into the bloodstream/ nutrient-rich blood gets processed/ filters harmful substances/waste. 
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2.1- Enzymes & Digestion

Digestive System

  • Large intestine- Absorbs water/ food in L.I. becomes drier/thicker and becomes faeces. (Colon-absorbs water/minerals into blood)/(appendix-tiny tube with a closed end coming off it)
  • Large intestine pushes faeces into the rectum
  • Rectum- stores poo/waste products
  • Until it goes into the anus and is pushed out through egestion.
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2.1- Enzymes & Digestion

What is Digestion? 

Diegstion takes place in two stages;

  • Physical
  • Chemical  
  • Physical

If food is large, broken down into small pieces. Makes it possible to ingest food but also provides large surface area for chemical digestion.

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2.1- Enzymes & Digestion


Breaks down large, insouble molecules into smaller, soubles one.

Carried out by enzymes. All digestive enzymes function by Hydrolysis. (splitting up molecules by adding water to chemical bonds that hold them together) Enzymes= Hydrolases

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2.1- Enzymes & Digestion

Different types of digestive enzymes;

  • Carbohydrases break carbohydrates into monosaccharides.
  • Lipases break lipids (fats/oil) into glycerol/ fatty acids.
  • Proteases break proteins into amino acids.

Once hydolysed, they are absorbed by small intestines into the blood.

  • Absorption- (taking souble molecules into the body)
  • Assimilation-(incorparating absorbed molecules into body tissues)
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2.2- Carbohydrates- monosaccarides

Carbohyrates- carbon molecules (carbo) + water (hydrate). Some are small while others are large.

  • Large molecules often contain carbon as they are readily link to another to form a chain. 
  • General name for individual molecules- Monomers.
  • General name for molecules that is made up of many similar repeating units are called Polymers.
  • Single mono- monosaccharide
  • Monomers combined- disaccharides
  • Many monosaccharides in large numbers form polysaccharides.
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2.2- Carbohydrates- monosaccarides


  • Sweet-tasting, souble subtances/ general formula (CnH2nOn), n= any number from 3-7. Atoms form ring form.
  • Examples; Glyceraldehyde (3C), Triose, Ribose, Deoxyribose(5C), Pentose, Glucose, Fructose(6C), Hexose,etc.
  • Benedict's reagent turns red with a reducing sugar because sugar donates electrons that reduce blue copper sulfate- orange copper oxide.
  • Concerntration-  none= blue high= red
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2.3- Carbohydrates- Disaccharides/ Polysaccharides


When in pairs, monosaccharides form a disaccarides;

  • Glucose + Glucose= Maltose
  • Glucose + Fructose= Sucrose
  • Glucose + Galatose= Lactose

When monosaccharides join, molecule of water is removed.- Condensation reaction. Bond formed= Glycosidic bond.

When water is added to Disaccharides under suitable conditions, it breaks the glycosidic bond releasing monosaccharides.- Hydrolysis (Addition of water/causes breakdown)

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Test for reducing sugars

Some disaccharides (maltose) are reducing sugar. Benedict's test used to detect this.

Other disaccharides (sucrose) are non-reducing sugar because they don't change colour of Benedict's when heated with it.

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