SECTION 9 NUTRITION IN HUMANS

Introduction Humans and other mammals are adapted for feeding and digestion. We use the essential molecules from food to provide energy for the cells in our bodies. We use the essential molecules from food to provide energy for the cells in our bodies. Foods at the supermarket are usually grouped into dairy, meat, fruit and vegetables etc. In Biology foods are grouped according to their chemical composition. Foods at the supermarket are usually grouped into dairy, meat, fruit and vegetables etc. In Biology foods are grouped according to their chemical composition.

Introduction Any one food may be a complex mixture of substances, these can be classified according to their chemical structure.

Food Groups Humans eat a range of different foods which supply energy, allow growth and repair in the body. Common foods such as milk, bread or potatoes each contain a mixture of different food groups. Common foods such as milk, bread or potatoes each contain a mixture of different food groups.

Food Groups starch and sugars cellulose

Notes Read pages 222 to 225 in the text book. Copy the names of the 5 main food groups. Name the food groups most plentiful in cow’s milk. Name the different types of carbohydrate found in food.

Content of Nutrients in Milk AnimalFatProteinCarbohydrateCalciumPhosphorousVitaminC Cow Goat Human Sheep …2.46 Content per 100 grams of whole milk (or whey)

Composition of Different Foods You are familiar with the composition of different types of milk. Other foods contain different food groups in different proportions. Other foods contain different food groups in different proportions. Use the table on page 225 to find the 3 foods richest in carbohydrate, fat and protein – copy and complete the table. Use the table on page 225 to find the 3 foods richest in carbohydrate, fat and protein – copy and complete the table.

Chemical Structure Carbohydrate, protein and fat contain large, complex molecules. These large molecules are made up of smaller molecules joined together. These large molecules are made up of smaller molecules joined together. The small molecular units are made up of atoms of just a few chemical elements. The small molecular units are made up of atoms of just a few chemical elements.

Notes Collect a “Food Molecules” hand-out and fill in the missing words, glue into your jotter. Use the information to answer the think box questions – discuss these with the person next to you. Complete the Check-Test. If you finish – copy the vitamin and nutrient tables into your jotter.

Alimentary Canal The food we eat passes from the mouth into a long tube called the alimentary canal (or gut). This tube runs down the body to the anus, as food passes through it is processed in various ways. Processing involves muscular action and various juices which the alimentary canal and associated organs secrete.

Parts of the Alimentary Canal The alimentary canal (or gut) is the tube within the body through which food passes and is processed in various ways. There are several different organs that are not part of the canal but are joined to it. These are the associated organs, they provide various substances that are used to digest food in the alimentary canal.

Notes The meaning of the term “alimentary canal”. The labelled and coloured diagram. A list stating the associated organs of the alimentary canal.

Role of the Mouth The mouth is the opening at the start of the alimentary canal. This is where food first enters the canal and also where the processing of the food starts. Chewing (or mastication) stimulates saliva production which will act as a lubricant to condense food into a bolus.

Role of the Mouth Saliva contains starch-digesting enzymes which will start the breakdown of the food. As the food stays in the mouth for only a short time, there is very little or no breakdown of the starch.

Muscles of the Alimentary Canal Food has to be kept moving along the alimentary canal while at the same time being mixed with various juices. These actions are produced by muscles in the walls of the canal - a person has little or no conscious control over this. These actions are produced by muscles in the walls of the canal - a person has little or no conscious control over this.

Muscles of the Alimentary Canal The fibres of these muscles run along the length of the canal and are called longitudinal muscles. Other muscle fibres occur in rings around the canal and are called circular muscles. Other muscle fibres occur in rings around the canal and are called circular muscles. The 2 types of muscles work together in a squeezing motion that pushes food along the alimentary canal, this is called peristalsis. The 2 types of muscles work together in a squeezing motion that pushes food along the alimentary canal, this is called peristalsis.