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# Chapter 1: The chemistry of life

## 1.1 Overview (ESG42)

### Introduction (ESG43)

In this first chapter, learners will be introduced to the main 'building blocks' of life. This section should draw on their basic understanding from 'Matter and Materials' in Natural Sciences. Learners will study the molecular structure and biological functions of key molecules important to life. They will study the chemistry of proteins, carbohydrates, lipids, vitamins and nucleic acids and will learn the role of each nutrient class in plant and animal life. They will also learn how their diet allows them to obtain sufficient quantities of each of these nutrients. There are a variety of practicals and investigations in this section, which provide an opportunity for learners to practice applying the scientific method.

In this chapter we will study the molecular structure and biological functions of key molecules important to life. We will study the chemistry of proteins, carbohydrates, lipids, vitamins and nucleic acids and will learn the role of each nutrient class in plant and animal life. We will also learn how our diet allows us to obtain sufficient quantities of each of these nutrients. There are a variety of practicals and investigations in this section, which provide an opportunity for you to practice applying the scientific method.

• Organic molecules always contain carbon (C), and usually also contain hydrogen (H) and oxygen (O) atoms. Some important organic molecules also contain nitrogen (N), phosphorous (P), sulfur (S), iron (Fe) and other elements.
• Water ($$\text{H}_{2}\text{O}$$) is an inorganic compound made up of two H atoms and one O atom. Water helps with temperature regulation, form and support, transport and lubrication and is a medium for chemical reactions.
• Minerals are required as part of a healthy diet. A deficit in essential minerals results in deficiency diseases in plants and animals.
• Fertilisers are a way that essential nutrients can be added to the soil to improve plant growth.
• Carbohydrates are made up of C, H and O. They can be in the form of monosaccharides (single sugars), disaccharides (double sugars) or polysaccharides (many sugars), and are an important energy source for plants and animals.
• Lipids are made up of C, H and O. Triglycerides are a type of lipid that contains glycerol and three fatty acid chains. Cholesterol, another type of lipid, can increase the risk of heart disease.
• Proteins are made up of C, H, O, N, and some have P, S and Fe. Proteins consist of a long chain of amino acids that fold into a very specific three-dimensional structure. Proteins are an important building block in plants and animals and play a role in the immune system and in cell communication.
• Enzymes are a type of protein that act as a biological catalyst to speed up reactions. They work by a "lock and key" mechanism and are affected by temperature and pH.
• Nucleic acids such as DNA and RNA are made of C, H, O, N and P. DNA contains the genetic information for heredity, and RNA has the instructions on how to make protein.
• Vitamins are important organic molecules that must be obtained in the diet. They often help enzymes to work properly, or act in growth or differentiation.

In order to understand the chemistry of living systems, it is important to understand how all living systems are arranged from the smallest unit (atomic scale) to the largest unit (ecosystems). A simple way to describe the levels of organisation of livings things can be given as follows:

atom $$\rightarrow$$molecule$$\rightarrow$$cell$$\rightarrow$$tissue$$\rightarrow$$organ$$\rightarrow$$system$$\rightarrow$$organism$$\rightarrow$$ecosystem