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Quick Questions

This lesson covers the process of food breakdown in our body and the enzymes responsible for the breakdown of carbohydrates, lipids, and proteins. It explains the terms hydrolysis and condensation in relation to carbohydrates and describes how starch digestion is completed in the small intestine. Additionally, it explores the increase in glucose concentration and the absorption and assimilation of broken down food molecules.

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Quick Questions

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  1. Quick Questions • Name two ways in which the food is broken down in our body. • Name the enzymes involved in the breakdown of the following: carbohydrates, lipids, proteins.

  2. 2: Enzymes and the digestive system Lesson Objectives: • Describe the terms hydrolysis and condensation in context of carbohydrates (AO1: E) • Explain how is starch digestion completed in the small intestine (AO2: D/C) • Apply your knowledge of sugar molecule to suggest the increase in the concentration of glucose (AO2 and AO3: A)

  3. Enzymes and the digestive system AO1 Digestion takes place in two stages: • Physical breakdown • Chemical digestion Physical breakdown – breakdown of food by teeth and muscles. Muscles in the stomach churn the food, physically breaking the food. Chemical digestion – Carried out by enzymes. All enzymes split up molecules by adding water to the chemical bonds, this is called hydrolysis. Such an enzyme is called a hydrolase. Once the large molecule has been hydrolysed it is further broken down by another enzyme/s.

  4. Enzymes and the digestive system AO1 Three main enzymes in the body: • Carbohydrase • Lipase • Protease Broken down food is absorbed in the body – Absorption. When these broken down molecules become a part of the tissue and muscles - Assimilation.

  5. Enzymes and the digestive system AO1 Key prefixes and suffixes Carbo – carbon molecules Hydrate – water Mono – single Saccharide – sugar Di – two Poly – many Mer – part Lysis – destruction or dissolution Ide – a group of related compounds, idic (adj.) Ate – presence of oxygen (when naming compounds) Ose - sugar

  6. Enzymes and the digestive system AO1 Carbohydrates - monosaccharides Carbohydrates are polymers. What is a polymer? A monomer for carbohydrates is sugar/saccharide.

  7. Enzymes and the digestive system AO1 Monosaccharides – sweet –tasting and soluble. General formula – (CH2O)n (n is number between 3 to 7) Disaccharides – monosaccharides as a pair make a disaccharide. Glucose linked to glucose – maltose Glucose linked to fructose – sucrose Glucose linked to galactose – lactose

  8. Enzymes and the digestive system AO1 Polysaccharides – Many monosaccharides combine to form a polysaccharide. Large molecule and insoluble, making it more suitable for storage. When hydrolysed they break into mono or disaccharides. • In which form is the food stored in the plants and why? Starch, which is made up many glucose molecules. Cellulose, which is used to give structural support to the plants as opposed to storage. • What do you understand by the term ‘hydrolysed’? (break the word – hydra and lysis)

  9. Enzymes and the digestive system AO1 When monosaccharides combine together to form a disaccharide a water molecule is removed. This reaction is called condensation reaction. The bond formed is called a glycosidic bond.

  10. Enzymes and the digestive system AO1 Starch digestion • Amylase produced in mouth and pancreas hydrolyses alternate glycosidicbonds, which produces a disaccharide (maltose). • Maltose is then hydrolyses into glucose using the enzyme maltase. Maltase is produced in the lining of the intestine.

  11. Enzymes and the digestive system AO1 PAST EXAM QUESTIONS Sucrose, maltose and lactose are disaccharides. • Sucrase is an enzyme. It hydrolyses sucrose during digestion. Name the products of this reaction. (2 marks)

  12. Enzymes and the digestive system AO2/3 (ii) Explain the results on the graph. (2 marks)

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