CORE AREA 1 FOOD STUDIES Digestion of carbohydrates
During digestion water and enzymes break carbohydrate chains into monosaccharides. This process is called hydrolysis.
Mouth: food is chewed into small pieces by the teeth. The salivary glands secrete saliva containing the enzyme salivary amylase, which breaks down starch into maltose.
Pancreas: secretes pancreatic juice containing the enzyme amylase into the duodenum (the first part of the small intestine). This continues to break down starch into maltose.
Small intestine: the ileum (final section of the small intestine) secretes intestinal juice containing:
• the enzyme maltase, which breaks down maltose into glucose
• the enzyme sucrase, which breaks down sucrose into glucose and fructose
• the enzyme lactase, which breaks down lactose into glucose and galactose.
Mouth
Salivary glands Oesophagus
Liver
Duodenum Pancreas
Large intestine Ileum
Anus Digestive system
The monosaccharides glucose, fructose and galactose are now ready to be absorbed and utilised by the body.
Organ or gland
Salivary glands (mouth) Pancreas
Small intestine (ileum)
Secretion Enzymes Saliva
Pancreatic juice Amylase
Intestinal juice Maltase Sucrase Lactase
Salivary amylase Starch Starch
Substrate Product Maltose Maltose Glucose
Maltose Sucrose Lactose
Glucose and fructose Glucose and galactose
Absorption and utilisation of carbohydrates
After digestion the monosaccharides glucose, fructose and galactose are ready to be absorbed by the small intestine. They pass through the wall of the villi and into the bloodstream.
Next the hepatic portal vein transports the monosaccharides to the liver via the bloodstream.
HL
In the liver, fructose and galactose are converted to glucose. The glucose is then: • oxidised to produce heat and energy
• converted to glycogen and stored in the liver and muscles as a long-term energy reserve.
Excess glucose is converted to fat and stored as adipose tissue under the skin, insulating the body and acting as an energy reserve.
24 Complete Home Economics Intestine Villi and hepatic portal vein Villi
