Nutrition in mammal

Nutrition in mammals

By the end of this chapter, you will be able to:

(a) understand the role of enzymes in influencing life processes and appreciate that the working of enzymes may be affected by different factors

(b) conduct experiments on and explain the effects of pH and temperature on enzyme activity.

(c) understand the effect of pH and temperature on enzyme activity.

(d) know and identify different types of mammalian teeth, and relate their structure and position in the jaw to diet.

(e) understand the importance of oral hygiene and describe good practice in caring for teeth and gums in humans.

(f) appreciate the structure of the different parts of the mammalian alimentary canal and its role in the digestion of food.

(g) understand how the end product of digestion are absorbed and assimilated.

Introduction

Do you recall from Section 4.1 that animals are heterotrophs. They obtain their nutrients from existing plant or animal’s sources. In this Chapter you will find out about feeding in mammals as heterotrophic organisms.

5.1 Enzymes

Enzymes Enzymes are biological catalysts that are protein in nature. organism’s body. Reactions would take longer to complete.

This means they speed up chemical reactions in an if there were no enzymes. Enzyme are however specific in their actions and require specific conditions to work efficiently. In Activity 5.1 and 5.2, you are going to find out 1 more about enzymes.

Enzymes bring about many types of changes. Two of these changes are: 2 The breakdown of complex molecules to simpler ones like digestion and respiration. The building up of complex molecules from simple ones like proteins from amino acids, for this reason enzymes form an essential constituent of living cells.

Key question

What are the names and functions of the enzymes that work in the digestive system?

What you need

Biology textbooks

Computer with internet

Notebooks

Pens and pencils

What to do

1 In your group, research on and discuss the names and functions of enzymes that work in the human digestive system.

2 Produce a presentation to explain your findings to the rest of the class.

Enzymes are named following several systems, but the simplest rule is to add ‘ase’ to the words indicating the substance upon which the enzymes acts.

Thus enzymes acting on protein are proteases and those for maltose are maltases. Sometimes the word ‘ase’ is added to a word indicating the specific process for example those that breakdown complex substances by addition of water molecules are hydrolases. Some names however do not follow this scheme for example ptyalin, rennin, pepsin and trypsin.

Effect of pH and temperature on enzyme activity

Enzymes react differently to pH, some prefer an acid medium, some neutral while others prefer an alkaline one. pH is a unit or measure of acidity or alkalinity. The pH ranges from 1-14 where pH 7 is neutral.

Below pH7 is acidic and above pH, is alkaline. Enzyme activity affected by several factors including the pH of the solution and temperature.

The speed at which an enzyme acts therefore depends on these factors. In the next activity 5.3 you are going to find out the effect of pH on the rule of reaction.

Activity 5.1 Finding out names and functions of enzymes that work in the human digestive system

Key question

Carrying out experiments to determine the effect What is the effect of pH on enzyme activity?

What you need

Test tubes 2M

1% amylase

1% starch solution

Thermometer

Beaker

Hot water

Measuring cylinder (10ml)

what to do

2 Test tube A 1cm3 hydrochloric acid + 1cm3 of amylase + 1cm3 of starch solution.

Label four test tubes with letters A, B, C and D respectively.

3 B 1cm3 of sodium hydroride solution, 1cm3 of amylase + 1cm3 of starch.

4 C 1cm3 of distilled water + 1cm3 of amylase + 1cm3 of starch solution.

5 D 2cm3 distilled water + 1cm3 of starch solution.

6 Shake the contents of four test tubes to mix thoroughly and place in a water bath maintained at 37°C to 40°C. Observe for 40 minutes.

7 Record your observations.

8 Present your findings to the rest of class for discussion.

Questions

1 In which test tube was there change in colour?

2 Why do you think the colour changed in this test tube?

3 Which test tube is its control experiment?

Temperature affects enzyme activity by affecting the overall shape of the enzyme. High temperature in particular changes the shape of the enzyme molecules by deforming them.

are said to be denatured. Since the working of an enzyme as a catalyst depends on its shape, the enzyme activity is slowed down or even completely stopped.

Activity 5.2 Finding out the roles of enzymes in influencing life processes

 Key question

• How do enzymes work to influence life processes?

What you need.

• Biology textbooks
• Computer with internet
• Pens and pencils

What to do  

1. In your group research on and discuss the effects of enzymes on chemical reactions and list the properties of enzymes.
2. Present findings to rest of class.

Enzymes are named following several systems, but the simplest rule is to add ‘ ase ‘ to the words indicating the substance upon which the enzymes act. Thus enzymes acting on protein are proteases and those for maltose are maltases. Sometimes the word ‘ ase ‘ is added to a word indicating the specific process for example those that breakdown complex substances by addition of water molecules are hydrolases. Some names however do not follow this scheme for example ptyalin, rennin, pepsin and trypsin.

Effect of pH and temperature on enzyme activity

Enzymes react differently to pH; some prefer an acid medium, some neutral while others prefer an alkaline one. PH is a unit or measure of acidity or alkalinity. The pH ranges from 1-14 where pH 7 is neutral. Below pH7 is acidic and above pH, is alkaline.

Enzyme activity affected by several factors including the pH of the solution and temperature. The speed at which an enzyme acts therefore depends on these factors. In the next activity 5.3 you are going to find out the effect of pH on the rule of reaction.

Activity 5.3 Carrying out experiments to determine the effect of pH on enzyme activity

Key question

• What is the effect of pH on enzyme activity?

 What you need

• 1 % amylase.
• 1 % starch solution
• Test tubes
• 2M HCL, 2M NaoH
• Distilled water

 What to do

1. Label four test tubes with letters A, B, C and D respectively.
2. Test tube a 1cm hydrochloric acid + 1cm³? Of amylase + 1cm³ of starch solution.
3. B 1cm³ of sodium hydroride solution, 1cm³ of amylase + 1cm³ 3 of starch solution.
4. C 1cm³ of distilled water + 1cm³ of amylase + 1cm³ of starch solution.
5. D 2cm³ distilled water + 1cm³ of starch solution.
6. Shake the contents of four test tubes to mix thoroughly and place in a water bath maintained at 37 ° C to 40 ° C. Observe for 40 minutes .
7. Record your observations.
8. Present your findings to the rest of class for discussion.

Questions

1. In which test tube was there change in color?
2. Why do you think the color changed in this test tube?
3. Which test tube is its control experiment?

Temperature affects enzyme activity by affecting the overall shape of the enzyme. High temperature in particular changes the shape of the enzyme molecules by deforming them. They are said to be denatured. Since the working of an enzyme as a catalyst depends on its shape, the enzyme activity is slowed down or even completely stopped.

Activity 5.4 Finding out roles of enzymes in influencing life processes

Key question

What is the effect of temperature on enzyme activity?

What you need

Test tubes •

@1% starch solution

1% amylase •

Thermometer

Beaker

Hot water

Benedict’s solution

Measuring cylinder (10ml)

What to do

1 Label 6 test tubes with letters A, B, C, D, E, and F respectively.

2 Half fill each test tube with starch solution.

3 Add 1cm3 of enzyme solution to each test tube except F.

4 Place the test tubes in a water bath as follows:

Tube A at room temperature – Take a record of this temperature

B at 30°C D at 50°C C at 40°C

E at 60°C

5 Test the contents of each test tube for reducing sugar using solution following the procedure used in Table 3.1.

6 Record the colour changes in the table below:

Questions

1 In which test tube are the reducing sugar in highest concentration?

2 What effect did the change in temperature have on the rate of the reaction?

3. Which test tube is its control experiment?

5.2 Mammalian teeth

Teeth are the white structures in the mouth of a mammal that are fixed in the jaws. The teeth are used during feeding to cut, tear, crush or grind food.

They are distinguished according to shape, size and position on the jaw. Food is obtained by mammals using their teeth, lips and tongue.

These structures vary from one type of mammal to another. However the teeth have a common structure that can be used to identify them and to tell their functions.

In this activity you are going to study mammalian teeth for their structure and function.

Activity 5.5 Finding out different types of mammalian teeth and how they are adapted to their function

Key question

what are the different types of mammalian teeth. how are they adapted to their function.

What you need

Molar tooth

Premolar tooth

Incisor tooth

Canine tooth

What to do

In pairs, observe a molar, canine, premolar and incisor tooth and identify:

the common structural features of each of the tooth in a mammal.

the adaptations of each type of tooth to its function.

the position of the tooth on the jaw bone.

2 Suggest from the structure of the tooth and its position on the jaw what it is used for during feeding.

3 Make an accurate labeled drawing of each tooth and state the magnification.

4 Present your findings to the rest of the class.

5.3 Oral hygiene

Oral hygiene refers to the maintenance of a clean surface and interior of the mouth especially the teeth, tongue and gums. This is necessary to prevent bacteria from causing tooth decay and gum disease in addition to bad breath.

Some people have lost their teeth due to tooth decay and poor oral hygiene (care of the area in and around the mouth).

In this activity you are going to discuss ways of maintaining oral hygiene. NOTE You can also observe each other’s teeth

Activity 5.6 Finding out how oral hygiene can be maintained

Key question

Why is it necessary to maintain oral hygiene?

What you need

Biology textbooks

Computer with internet Notebooks

What to do

In pairs, share experience and research on reasons for, and methods of ensuring dental hygiene as well as consequences of poor hygiene.

Produce a short good practice guide for maintaining oral hygiene.

Share your findings with the rest of the class.

5.4 Dental formulae in relation to diet

The teeth in the mouth of mammals are found in a single row on the jaw bone. Teeth of the same type lie next to each other for effective functioning; they also differ in their number, size and structure.

In this activity you are to observe the teeth on the jaw bones, identify them, count them and write down the dental formulae. The dental formula is a formula showing the number of each type of teeth according to their arrangement on the jaw.

The letters used in the formulae are i for incisors, c for canines. pm for premolar and m for molar. Generally it shows the number of each type of teeth in half the upper jaw and half the lower jaw. The human dental formula is therefore;

Chapter summary

In this chapter, you have learnt that:

• Enzymes influence the rate of life processes since they are biological catalysts.
• The working of enzymes may be affected by different factors like pH, temperature.
• Mammalian teeth have different parts: crown, neck and root which differ among the incisors, canines, premolars and molars.
• Oral hygiene is the maintenance of a clean mouth: teeth, gums, tongue and lips.
• It is necessary for one’s health.
• The mammalian alimentary canal plays the role of digestion and absorption of food.
• End products of digestion are: amino acids, fatty acids and glycerol and glucose.
• They are absorbed into the blood stream and then assimilated in the body cells.

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