We have learnt…
Post on 24-Feb-2016
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We have learnt…
• What are the 4 stages of nutrition?• Why must we digest our food?• What are the two types of digestion?• What is the structure and function of:
– Mouth– Oesophagus
Question 1
What is the enzyme that is produced by the mouth?
(A)Protease(B) Lipase(C) Amylase(D)Cellulase
Question 2
What is the process of moving food down the oesophagus
(A)By gravity(B) Absorption(C) Excretion(D)Peristalsis
Question 3
Digestion is present in the oesophagus.
True/False
Question 4
Which of the following is not one of the stages of holozoic nutrition?(A)Absorption(B) Egestion(C) Ingestion(D)Digestion
Lesson Objective
• Describe the structure and the main functions of the stomach in relation to digestion.
• Holiday Assignment
The Stomach
Stomach : Structure• Thick muscular bag with
thick muscle walls
• At the end of the stomach, there is a muscular valve called pyloric sphincter
• Controls the entry of food from the stomach into the intestines
• Mechanical Digestion• Peristalsis in the stomach helps to mix and churn the food• Digestion of proteins.• Storage of food, where the partly digested food particles becomes
liquefied chyme .
Stomach : Functions
Stomach : FunctionsProtein digestion begins in the stomach
• Proteins polypeptides
• Protein digestion in the stomach requires the gastric juice
• Food in the stomach stimulates the gastric glands to secrete gastric juice
Gastric Juice• Gastric juice is a dilute solution of:
– Hydrochloric acid (~pH 2)– Pepsin – Rennin
Gastric Juice
Functions of dilute HCl:
• Denatures salivary amylase
• Activates inactive enzyme, Pepsin
• Provide slightly acidic for action of gastric enzymes
• Kills potentially harmful microorganisms
Stomach : Functions
Stomach : Functions
Pepsin (protease)
• Digest proteins into polypeptides
proteins polypeptidespepsin
Pepsin does not digest proteins to amino acids!
• Function of Rennin (for your information):
Rennin curdles milk proteins
– converts the soluble caseinogen found in milk to insoluble casein
– caseinogen (soluble) casein (insoluble)– this process requires Ca2+
• This allows the insoluble casein to remain in the stomach long enough for digestion by pepsin.
Stomach : Functions
Summary• Stomach
– Structure– Functions
Mechanical DigestionChemical Digestion
• Hydrochloric acid (~pH 2)• Pepsin • Rennin
Remember your job application?
Let us assess without you will get the job!
Mouth
Applying for job : Digestion of StarchCondition: pH 7Skills: • Tongue• Teeth • Saliva
Stomach
• Applying for job: Digestion of protein• Condition: pH2 • Skills:• Mechanical Digestion• Chemical Digestion (Gastric Juice)• Hydrochloric acid• Pepsin• Rennin
Holiday Assignment
1. Ten Years Series Questions2. Watch animation and complete the
worksheet
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