breakdown of food in the digestive system. digestive enzymes digestive enzymes are produced by...
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Breakdown of food in the digestive system
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Digestive enzymes
• Digestive enzymes are produced by specialised cells in glands and in the lining of the gut.
• The enzymes then pass out of the cells into the gut where they come into contact with food molecules.
• They catalyse the breakdown of large molecules into smaller molecules.
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Starch molecules – large and branched
Amylase – digestive enzyme
Amylase breaks down starch into glucose and fructose
Readily absorbed.
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Digesting carbohydrates
• Enzymes which breakdown carbohydrates are called carbohydrases.
• Amylase catalyses the breakdown of starch into glucose and fructose.
• Amylase is produced in the salivary glands, pancreas and small intestine.
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Amino acid
Amino acid Amino
acid
Breaks down proteins into amino acids.
Still too big!
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Proteins – large and branched
Amino acid
Amino acid
Amino acid
Amino acid
Amino acid
Amino acid
Protease enzymes from the small intestine
Amino acid
Amino acid
Amino acid
Amino acid
Amino acid
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mino acid
Amino acid
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Digesting proteins
• The breakdown of protein is catalysed by protease enzymes.
• Proteases are produced in the stomach, pancreas and small intestine.
• Breakdown of proteins into amino acids takes place in the stomach and small intestine.
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Bile from the liver mixes with the ‘fat’ to make an emulsion
Lipase from the pancreas breaks down the fats to...
Fatty acids and glycerol which is easily absorbed.
Fats & Oils
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Digesting lipids
• Lipids are broken down into fatty acids and glycerol in your small intestine.
• Reaction is catalysed by lipase enzymes.
• Lipase enzymes are produced by the pancreas and the small intestine.
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Breakdown of food in the digestive system
Objectives1. Understand the uses of digested
food.2. Be able to explain digestion in the
stomach.3. Be able to explain the role of bile in
digestion.
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Using the digested food
• Glucose– Respiration
• Fatty acids and glycerol– Source of energy– Build cell membranes– Make hormones – Fat stores
• Amino acids– Protein synthesis
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What factors affect enzyme activity?
substrate concentration
temperature
pH
enzyme concentration
surface area
pressure
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Digestion in the stomach
oesophagus
duodenum
mucus cells
parietal cells(acid-producing)
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• The stomach produces hydrochloric acid. – It kills many harmful microorganisms
that might have been swallowed along with the food.
– The enzymes in the stomach work best in acidic conditions (pH2).
Enzymes in the stomach
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Digestion in the small intestine
Digestive enzymes found in the small intestine are damaged by a strongly
acidic pH.
How does the body avoid this problem?
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Digestion in the small intestine
gallbladder
duodenum bile duct
pancreas
hepaticduct
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• The liver produces bile (an alkali)– Stored in the gall bladder – Released into the small intestine.
• Bile neutralizes the acidic contents coming from the stomach.
• Provides alkaline environment for the enzymes in the small intestine.
Digestion in the small intestine
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Altering the surface area
• Bile emulsifies the fats in your food. – This means it physically breaks up large
drops of fats into smaller droplets.
– What effect will the increase in surface area have on the rate of fat digestion by lipase?
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Match each enzyme to its reactant
Amylase
Lipase
Protease
Carbohydrase
Protein
Starch
Carbohydrate
Fat
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Where are they broken down and what are they
broken down into???
Starch
Proteins
Fats
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What are the two roles of bile?