Nutrition

Question 1

2.27: What is the function of the mouth in the alimentary canal?

Answer 1

• Mechanical digestion occurs
• Large food is turned into a bolus to provide large surface area to volume ratio for salivary Amylase to break down Starch in food into Glucose
• Saliva lubricates bolus for easy swallow

Question 2

2.27: What is the function of the oesophagus in the alimentary canal?

Answer 2

• The oesophagus is a tube connecting Mouth to Stomach
• Peristalsis (wave-like contractions) occurs to push bolus down the tube towards Stomach

Question 3

2.27: What is the function of the stomach in the alimentary canal?

Answer 3

• Peristalsis continues mechanical digestion, and enzymes begin chemical digestion
• Hydrochloric acid maintains Optimum pH to increase rate of enzyme activity and metabolic reactions

Question 4

2.27: What is the function of the small intestine in the alimentary canal?

Answer 4

Lined with Villi to absorb digested soluble molecules into the circulatory system for use

Question 5

2.27: What is the function of the large intestine in the alimentary canal?

Answer 5

Absorbs Water from undigested food to produce faeces (stored in the Rectum and removed through the Anus)

Question 6

2.27: What is the function of the pancreas in the alimentary canal?

Answer 6

• Synthesises pancreatic enzymes (Amylase, Protease, and Lipase)
• Secretes pancreatic enzymes into the Stomach and Small intestine for digestion

Question 7

2.27: What is the alimentary canal?

Answer 7

Digestive tract from the mouth to the anus

Question 8

2.28: What is peristalsis?

Answer 8

• Wave-like muscle contractions that push food bolus down the Oesophagus from Mouth to Anus
• Occurs in Stomach and Gut

Question 9

2.28: What is the purpose of the circular muscles in peristalsis?

Answer 9

• Circular muscle changes the radius of the Oesophagus
• Contraction of Circular muscle behind the food bolus constricts the gut to prevent bolus from being pushed back towards the Mouth

Question 10

2.28: What is the purpose of the longitudinal muscles in peristalsis?

Answer 10

• Longitudinal muscle changes length of Oesophagus
• Contraction of Longitudinal muscle where food bolus is located moves it along the gut

Question 11

2.28: How does peristalsis help in digestion?

Answer 11

• As food bolus is pushed only a few centimetres at a time, progression through intestine is slow, allowing time for digestion
• This allows the churning of semi-digested food as they mix food bolus with enzymes, increasing rate of digestion

Question 12

2.30: What is bile?

Answer 12

• Alkaline substance produced in the Liver and stored in the Gall Bladder
• Bile emulsifies large Lipid molecules into droplets with larger surface area to volume ratio to increase the rate of digestion

Question 13

2.31: How does bile neutralize stomach acid?

Answer 13

• Bile will neutralise Hydrochloric acid to maintain Alkaline conditions, allowing optimum enzyme activity and increasing the rate of metabolic reactions
• Enzymes in Small intestine function optimally in Alkaline conditions (optimum pH of 8-14)
• However, churning of food in Stomach by Hydrochloric acid creates Acidic environment

Question 14

2.31: How does bile emulsify liquids?

Answer 14

• As the breakdown and digestion of Lipid molecules require a long period of time, Bile is used to emulsify large Lipid molecules into small droplets
• Lipid droplets will have a larger surface area to volume ratio, allowing faster breakdown by Lipase into Fatty acids and Glycerol, hence increasing the rate of lipid digestion

Question 15

2.32: What are the adaptations of the small intestine for absorption?

Answer 15

• Thin cell wall
• Large surface-to-volume ratio
• Dense capillary network
• Lacteal

Question 16

2.32: How does a thin cell wall in the small intestine aid absorption?

Answer 16

Thin cell wall (one cell thick) to minimise distance of diffusion of digested soluble molecules, therefore increasing the rate of absorption.

Question 17

2.32: What is the villus?

Answer 17

Small finger-like projections lining the Intestine wall that absorb digested soluble food molecules

Question 18

2.32: Why is a large surface area to volume ratio important in the small intestine?

Answer 18

Folded to increase surface area to volume ratio for diffusion of digested soluble molecules, therefore increasing the rate fo absorption

Question 19

2.32: What is the role of the dense capillary network in the small intestine?

Answer 19

Dense capillary network nearby to provide rich blood supply, creating a strong concentration gradient for the diffusion of digested soluble molecules, therefore increasing the rate of absorption

Question 20

2.32: What does the lacteal do in the small intestine?

Answer 20

Lacteal absorbs and transports Fatty acids and Glycerol from Intestine to Lymphatic system