Human Diet & Digestion (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

Fig. 1 is a diagram of the alimentary canal and associated organs.

Some parts are identified by letters.

Fig. 1

Complete Table 1 by inserting the letter from Fig. 1 which identifies the part that carries out the function described. 

Table 1

State two ways in which the body can defend itself against pathogens. 

Extended Tier Only

The reactions of chemical digestion are catalysed by enzymes.

Fig. 1 shows the stages of an enzyme-catalysed reaction.

Fig. 1

State the names of A to D in Fig. 1.

Explain the importance of chemical digestion.

Fig. 2 shows the human alimentary canal and associated organs.

The functions of some of these parts of the body are given in Table 1.

Fig. 2

Complete Table 1. One row has been done for you. 

Table 1

A man is overweight.

Fig. 1 shows his diet. He consumes 15 000 kJ a day.

Fig. 1

Suggest why the diet shown in Fig. 1 is not considered to be a balanced diet.

[2]

Suggest and explain how the man could reduce his weight.

The following sentences describe the importance of some foods.

Choose words from the list to complete the sentences.

Oranges and lemons are fruits which are a good source of ............................................... and help to prevent ............................................... .

Foods made from milk are important for making healthy bones and ............................................... because they are a good source of ............................................... .

Fibre is important because it helps to prevent ............................................... .

Explain how a woman’s dietary needs will change when she is pregnant.

Two functions of the alimentary canal are mechanical digestion and chemical digestion.

Outline where and how mechanical digestion occurs in the alimentary canal.

Extended Tier Only

Enzymes catalyse the reactions of chemical digestion. Table 1 gives information about chemical digestion in three parts of the alimentary canal.

Complete Table 1.

Table 1

Fig. 1 shows some parts of the human body.

Fig. 1

Use Fig. 1 to complete Table 1.

State the letter and the name of the part responsible for each function.

Table 1

[4]

State the letter of the part of the body where egestion occurs.

[1]

State the function of hydrochloric acid in the body.

[1]

Define the term chemical digestion.

Extended Tier Only

A student investigated the activity of the digestive enzyme pepsin. Fig. 1 shows the apparatus used in the investigation.

Fig. 1

The appearance of the four test-tubes was recorded at 0 and 5 minutes.

The protein in the egg white solution gives the solution a cloudy appearance.

The cloudy appearance clears when the protein in the egg white solution breaks down.

Table 1 shows the results.

Table 1

[5]

Explain the purpose of test-tube 4.

State the name of the organ in the body that produces pepsin.

[1]

Fig. 1

Identify organ X in Fig. 1.

[1]

Describe the function of organ X in digestion.

[4]

Extended Tier Only

Protease enzymes chemically break down protein molecules.

Explain why protease enzymes cannot break down any other type of molecule.

Extended Tier Only

The stomach produces gastric juice which contains hydrochloric acid.

Explain the importance of hydrochloric acid in the stomach.

Extended Tier Only

Normally the epithelial cells in the lining of the stomach are protected from the effects of gastric juice by a layer of mucus secreted by goblet cells found in the stomach lining.

Sometimes a type of bacteria called Helicobacter pylori can penetrate the mucus layer and cause damage to the goblet cells. This leads to the formation of a peptic ulcer.

Fig. 1 compares a healthy stomach lining with one that has been infected by H. pylori.

Fig. 1

Based on the information in Fig. 1, suggest how H. pylori may lead to the formation of a peptic ulcer.

Extended Tier Only

Patients suffering from peptic ulcers may receive treatment with substances called proton pump inhibitors (PPI's). These substances will suppress the cells in the lining of the stomach that produce hydrochloric acid.

Explain how PPI's could act as a treatment for peptic ulcers.

Extended Tier Only

Based on the information from part (c), suggest the effect the PPI's could have on digestion in the stomach.

Extended Tier Only

A group of students investigated the effect of pH on the activity of amylase.

Their results are shown in Fig. 1.

Fig. 1

Identify the optimum pH of amylase from Fig. 1.

[1]

Explain your answer from part (i).

[2]

Extended Tier Only

Calculate the percentage decrease in the time taken to digest starch between pH 5 and 7. Show your working.

Extended Tier Only

Describe and explain the shape of the graph between pH 7 and 8.

Extended Tier Only

Fig. 1 shows the location of the gallbladder in the human digestive system.

Fig. 1

Explain the purpose of the gallbladder.

Extended Tier Only

The gallbladder may become inflamed or blocked by gallstones, which may cause much pain. In such cases, it is best to surgically remove the gallbladder. Doctors may recommend that patients with no gallbladder follow a low fat diet after surgery.

Suggest a possible reason for this recommendation.

Extended Tier Only

Certain vitamins are known as fat soluble vitamins. They are often found in food with a high fat content and are best absorbed into the blood along with digested lipids.

Based on the information provided in part (b) and (c), explain why people without gallbladders may develop deficiencies in these vitamins.

Vitamin D is an example of a fat soluble vitamin. In some cases, children may need to have their gallbladders removed due to inflammation. In most cases, this will not have a significant impact on their long term health, but in some extreme cases, it might.

Suggest a possible impact that this may have on their health.