Download File

Quick Questions
1. Name two ways in which the food is broken
down in our body.
2. Name the enzymes involved in the
breakdown of the following: carbohydrates,
lipids, proteins.
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)
Enzymes and the digestive system
AO1
Digestion takes place in two stages:
1. Physical breakdown
2. 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.
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.
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
Enzymes and the digestive system
AO1
Carbohydrates - monosaccharides
Carbohydrates are polymers.
What is a polymer?
A monomer for carbohydrates is
sugar/saccharide.
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
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)
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.
Enzymes and the digestive system
AO1
Starch digestion
Amylase produced in mouth and pancreas
hydrolyses alternate glycosidic bonds, which
produces a disaccharide (maltose).
Maltose is then hydrolyses into glucose using
the enzyme maltase. Maltase is produced in
the lining of the intestine.
Enzymes and the digestive system
AO1
PAST EXAM QUESTIONS
Sucrose, maltose and lactose are disaccharides.
1. Sucrase is an enzyme. It hydrolyses sucrose
during digestion. Name the products of this
reaction. (2 marks)
Enzymes and the digestive system
AO2/3
(ii) Explain the results on the graph. (2 marks)