Human Digestive System (Cambridge O Level Biology)

Fig. 1

Identify organ X in Fig. 1.

[1]

Describe the function of organ X in digestion.

[4]

Chewing on a piece of bread will result in a sweet taste developing in the mouth after a while.

Explain the reason for this.

Protease enzymes chemically break down protein molecules.

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

The stomach produces gastric juice which contains hydrochloric acid.

Explain the importance of hydrochloric acid in the stomach.

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.

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.

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

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]

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

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

Outline the process of starch digestion in the human body.

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

Fig. 1

Explain the purpose of the gallbladder.

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.

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.

Fig. 1 shows a section through a tooth.

Fig. 1

State the names of structures F, G and H.

State two functions of teeth.

[2]

Describe the importance of teeth in the digestion of food.

[2]

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.

Extended Only

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

Fig. 1 shows the four different types of human teeth. 

Fig. 1

Fig. 2 shows a diagram of the position of the different types of teeth in the mouth.

Fig. 2

Complete Table 1 by writing the names, positions and functions of the different types of teeth in the mouth shown in Fig. 2.

Table 1

Red pandas, Ailurus fulgens, and humans have a similar arrangement of teeth.

Fig. 1 shows a section through one tooth of a red panda. Fig. 2 shows the side view of the lower jaw of a red panda.

                    Fig. 1                                                      Fig. 2

State the names of the structures labelled A to F in Fig. 1 and Fig. 2.

[3]

State the type of digestion that breaks down large pieces of food.

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

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

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

Substances that are absorbed from the alimentary canal may enter cells and become part of the cells. 

State the storage carbohydrate made from glucose in liver cells.

[1]

State the type of protein used in the immune system that is produced from amino acids by lymphocytes.

[1]

Fat is produced from fatty acids and glycerol by cells in the fatty tissue beneath the skin.

State one function of this layer of fat.

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]

Digestion in the human digestive system is carried out by the action of enzymes.

The diagrams each represent the action of a specific enzyme to break down a substrate into one or more end products.

Fig. 1.1 has been completed for you.

Complete Fig. 1.2 and Fig. 1.3.

Amino acids are the end products of protein digestion.

Describe what happens to these amino acids after digestion until they reach the liver.

The diagram shows part of the human alimentary canal and its associated organs. 

Complete the three labels on the diagram by naming the structures.

Describe the functions of the structure labelled F.

Name structure H and describe its role in homeostasis.