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Course Structure
Unit 1: Organisms and Life Processes
Life Processes
The Variety of Living Organisms
Unit 2: Animal Physiology
Breathing and Gas Exchange
Food and Digestion
Blood and Circulation
Coordination
Chemical Coordination
Homeostasis and Excretion
Reproduction in Humans
Unit 3: Plant Physiology
Plants and Food
Transport in Plants
Chemical Coordination in Plants
Reproduction in Plants
Unit 4: Ecology and the Environment
Ecosystems
Human Influences on the Environment
Unit 5: Variation and Selection
Chromosomes, Genes and DNA
Cell Division
Genes and Inheritance
Natural Selection and Evolution
Selective Breeding
Unit 6: Microorganisms and Genetic Modification
Using Microorganisms
Genetic Modification
Appendices
Glossary
About This Book
This book is for students following the Edexcel International GCSE (9–1) Biology specification and the Edexcel International GCSE (9–1) Science Double Award specification.
The book indicates which content is in the Biology examinations and not in the Double Award specification.
To complete the Double Award course you will also need to study the Physics and Chemistry parts of the course.
Each unit of this book contains explanations, examples, and exercises to build confidence.
The book describes the methods for carrying out all of the required practicals.
The language throughout this textbook is graded for speakers of English as an additional language (EAL), with advanced Biology-specific terminology highlighted and defined in the glossary at the back of the book.
A list of command words, also at the back of the book, will help you to learn the language you will need in your examination.
Progression icons refer to Pearson's Progression scale.
Edexcel have developed a Skills grid showing the skills you will practise throughout your time on the course. The skills in the grid have been matched to questions in this book to help you see which skills you are developing.
Assessment Overview
The following tables give an overview of the assessment for this course.
We recommend that you study this information closely to help ensure that you are fully prepared for this course and know exactly what to expect in the assessment.
Paper 1
Specification: Biology, Science Double Award
Percentage: 61.1 \%
Mark: 110
Time: 2 hours
Availability: January and June examination series
First assessment: June 2019
Paper 2
Specification: Biology
Percentage: 38.9 \%
Mark: 70
Time: 1 hour 15 mins
Availability: January and June examination series
First assessment: June 2019
If you are studying Biology then you will take both Papers 1 and 2.
If you are studying Science Double Award then you will only need to take Paper 1 (along with Paper 1 for each of the Physics and Chemistry courses).
Assessment Objectives and Weightings
AO1: Knowledge and understanding of biology (38\% – 42\%)
AO2: Application of knowledge and understanding, analysis and evaluation of biology (38\% – 42\%)
AO3: Experimental skills, analysis and evaluation of data and methods in biology (19\% – 21\%)
In the assessment of experimental skills, students may be tested on their ability to:
Solve problems set in a practical context
Apply scientific knowledge and understanding in questions with a practical context
Devise and plan investigations, using scientific knowledge and understanding when selecting appropriate techniques
Demonstrate or describe appropriate experimental and investigative methods, including safe and skilful practical techniques
Make observations and measurements with appropriate precision, record these methodically and present them in appropriate ways
Identify independent, dependent and control variables
Use scientific knowledge and understanding to analyse and interpret data to draw conclusions from experimental activities that are consistent with the evidence
Communicate the findings from experimental activities, using appropriate technical language, relevant calculations and graphs
Assess the reliability of an experimental activity
Evaluate data and methods taking into account factors that affect accuracy and validity.
Calculators are permitted in the examinations, but those with QWERTY keyboards or that can retrieve text or formulae will not be allowed.
Unit 1: Organisms and Life Processes
All living organisms are composed of microscopic units known as cells.
Cells allow them to grow, reproduce, and generate more organisms.
Chapter 1 looks at the structure and function of cells, and the essential life processes that go on within them.
Chapter 2 looks at the diversity of living things and how we can classify them into groups on the basis of the features that they show.
1 Life Processes
All living organisms are composed of units called cells.
The simplest organisms are made from single cells, but more complex plants and animals are composed of millions of cells.
Multicellular organisms have many different types of cells with different structures, specialized to carry out particular functions.
Despite differences, cells share basic features.
There are eight life processes which take place in most living things.
Require nutrition
Respire
Excrete
Respond to stimuli
Move
Control their internal conditions
Reproduce
Grow and develop
Most cells contain certain parts such as the nucleus, cytoplasm and cell membrane.
Some cells have structures missing, for instance red blood cells are unusual in that they have no nucleus.
The living material that makes up a cell is called cytoplasm.
Organelles can be seen using an electron microscope.
The largest organelle in the cell is the nucleus.
Nearly all cells have a nucleus.
The nucleus controls the activities of the cell.
It contains chromosomes which carry the genetic material, or genes.
Genes control the activities in the cell by determining which proteins the cell can make.
The DNA remains in the nucleus, but the instructions for making proteins are carried out of the nucleus to the cytoplasm, where the proteins are assembled on tiny structures called ribosomes.
A cell contains thousands of ribosomes, but they are too small to be seen through a light microscope.
Enzymes control the chemical reactions that take place in the cytoplasm.
All cells are surrounded by a cell membrane, sometimes called the cell surface membrane to distinguish it from other membranes inside the cell.
The membrane is partially permeable.
The membrane can go further than this and actually control the movement of some substances – it is selectively permeable.
Mitochondrion carries out some of the reactions of respiration releasing energy that the cell can use.
Most structures are found in both animal and plant cells.
Some structures are only ever found in plant cells - the cell wall, a permanent vacuole and chloroplasts.
The cell wall is a layer of non-living material that is found outside the cell membrane of plant cells.
It is made mainly of a carbohydrate called cellulose, although other chemicals may be added to the wall in some cells.
Mature (fully grown) plant cells often have a large central space surrounded by a membrane, called a vacuole.
This vacuole is a permanent feature of the cell.
It is filled with a watery liquid called cell sap, which is a store of dissolved sugars, mineral ions and other solutes.
Cells of the green parts of plants contain another very important organelle, the chloroplast.
Chloroplasts absorb light energy to make food in the process of photosynthesis.
They contain a green pigment called chlorophyll.
Cells from the parts of a plant that are not green, such as the flowers, roots and woody stems, have no chloroplasts.
The chemical reactions that take place in a cell are controlled by a group of proteins called enzymes.
Enzymes are biological catalysts.
The molecule that an enzyme acts on is called its substrate.
Each enzyme has a small area on its surface called the active site.
The substrate attaches to the active site of the enzyme.
The reaction then takes place and products are formed.
The substrate fits into the active site of the enzyme like a key fitting into a lock.
Just as a key will only fit one lock, a substrate will only fit into the active site of a particular enzyme.
This is known as the lock and key model of enzyme action.
After an enzyme molecule has catalysed a reaction, the product is released from the active site, and the enzyme is free to act on more substrate molecules.
The rate of reaction may be increased by raising the concentration of the enzyme or the substrate.
Two other factors that affect enzymes are temperature and pH.
The graph shows a peak on the curve at this temperature, which is called the optimum temperature for the enzyme.
Enzymes are made of protein, and proteins are broken down by heat.
Denaturing changes the shape of the active site so that the substrate will no longer fit into it.
The pH around the enzyme is also important.
The pH at which the enzyme works best is called its optimum pH.
Biology Only Practical Activities
Activity 1: An Investigation into the Effect of Temperature on the Activity of Amylase
The digestive enzyme amylase breaks down starch into the sugar maltose.
If the speed at which the starch disappears is recorded, this is a measure of the activity of the amylase.
Activity 2: An Investigation into the Effect of pH on the Activity of Catalase
Buffer solutions are solutions of salts that resist changes in pH.
Hydrogen peroxide (H2O2) is a product of metabolism.
Hydrogen peroxide is toxic (poisonous), so it must not be allowed to build up in cells.
The enzyme catalase protects cells by breaking down hydrogen peroxide into the harmless products water and oxygen: 2H2O2 \rightarrow 2H2O + O2
How The Cell Gets Its Energy
A cell needs a source of energy in order to be able to carry out all the processes needed for life.
It gets this energy by breaking down food molecules to release the stored chemical energy that they contain.
This process is called respiration.
Respiration happens in all the cells of our body.
Oxygen is used to oxidise food, and carbon dioxide (and water) are released as waste products.
The main food oxidised is a sugar called glucose.
The energy stored in the ATP molecules can then be used for a variety of purposes, such as:
contraction of muscle cells, producing movement
active transport of molecules and ions
building large molecules, such as proteins
cell division.
The energy released as heat is also used to maintain a constant body temperature in mammals and birds.
The overall reaction for respiration is:
glucose + oxygen → carbon dioxide + water (+ energy)
C6H{12}O6 + 6O2 → 6CO2 + 6H2O (+ energy)
This is called aerobic respiration, because it uses oxygen.
Aerobic respiration happens in the cells of humans and those of animals, plants and many other organisms.
The later steps in the process are the aerobic ones, and these release the most energy.
They happen in the mitochondria of the cell.
ATP
Cells have a way of passing the energy from respiration to the other processes that need it.
They do this using a chemical called adenosine triphosphate or ATP.
ATP is present in all living cells.
ATP is composed of an organic molecule called adenosine attached to three phosphate groups.
Anaerobic Respiration
There are some situations where cells can respire without using oxygen.
This is called anaerobic respiration.
In anaerobic respiration, glucose is not completely broken down, so less energy is released.
The advantage of anaerobic respiration is that it can occur in situations where oxygen is in short supply.
Two important examples of this are in yeast cells and muscle cells.
The glucose is partly broken down into ethanol (alcohol) and carbon dioxide:
glucose → ethanol + carbon dioxide (+ some energy)
Muscle cells can also respire anaerobically when they are short of oxygen.
This time the glucose is broken down into a substance called lactate:
glucose → lactate (+ some energy)
The volume of oxygen needed to completely oxidise the lactate that builds up in the body during anaerobic respiration is called the oxygen debt.
Practical Activities
Activity 3: Demonstration of the Production of Carbon Dioxide by Small Living Organisms
Hydrogen carbonate indicator solution is normally orange, but turns yellow if carbon dioxide is added to it.
Activity 4: Demonstration that Heat is Produced by Respiration
Movement Of Materials In and Out Of Cells
Cell respiration shows the need for cells to be able to take in certain substances from their surroundings, such as glucose and oxygen, and get rid of others, such as carbon dioxide and water.
The cell surface membrane can control which chemicals can pass in and out – it is described as selectively permeable.
There are three main ways that molecules and ions can move through the membrane. They are diffusion, active transport and osmosis.
Diffusion happens when a substance is more concentrated in one place than another.
This difference in concentration is called a concentration gradient.
Diffusion is the net movement of particles (molecules or ions) from a region of high concentration to a region of low concentration, ie. down a concentration gradient.
The rate of diffusion is affected by various factors.
The concentration gradient.
The surface area to volume ratio.
The distance.
The temperature.
Diffusion In A Jelly
Agar is a jelly that is used for growing cultures of bacteria.
It has a consistency similar to the cytoplasm of a cell.
It has a high water content.
Agar can be used to show how substances diffuse through a cell.
Active transport
During active transport a cell uses energy from respiration to take up substances against a concentration gradient.
The pumps are large protein molecules located in the cell membrane, and they are driven by the breakdown of ATP.
Osmosis
Osmosis happens when the total concentrations of all dissolved substances inside and outside the cell are different.
Water will move across the membrane from the more dilute solution to the more concentrated one.
Specialised Exchange Surfaces
All cells exchange substances with their surroundings, but some parts of animals or plants are specially adapted for the exchange of materials because they have a very large surface area in proportion to their volume.
In animals, two examples are the alveoli (air sacs) of the lungs and the villi of the small intestine.
The alveoli allow the exchange of oxygen and carbon dioxide to take place between the air and the blood during breathing.
The villi of the small intestine provide a large surface area for the absorption of digested food.
In plants, exchange surfaces are also adapted by having a large surface area, such as the spongy mesophyll of the leaf and the root hairs.
Biology Only
Multicellular organisms like animals and plants begin life as a single fertilised egg cell, called a zygote.
This divides into two cells, then four, then eight and so on, until the adult body contains countless millions of cells.
This type of cell division is called mitosis and is under the control of the genes.
First of all the chromosomes in the nucleus are copied, then the nucleus splits into two, so that the genetic information is shared equally between the two ‘daughter’ cells.
The cytoplasm then divides (or in plant cells a new cell wall develops) forming two smaller cells.
Cells, Tissues and Organs
Cells with a similar function are grouped together as tissues.
A collection of several tissues carrying out a particular function is called an organ. The main organs of the human body are noted.
Plants also have tissues and organs. Leaves, roots, stems and flowers are all plant organs.
In animals, jobs are usually carried out by several different organs working together.
This is called an organ system.
There are seven main systems in the human body.
digestive system
gas exchange system
circulatory system
excretory system
nervous system
endocrine system
reproductive system
Stem Cells
A stem cell is a cell that has the ability to divide many times by mitosis while remaining undifferentiated.
Later, it can differentiate into specialised cells such as muscle or nerve cells.
In humans there are two main types of stem cells:
Embryonic stem cells
Adult stem cells
Scientists are able to isolate and culture embryonic stem cells. These are obtained from fertility clinics where parents choose to donate their unused embryos for research.
Stem cell research can also present problems. Many people object morally to using cells from embryos for medical purposes despite the fact that they might one day be used to cure many diseases.
Looking Ahead – Membranes In Cells
Electron micrographs allow us to see cells at a much greater magnification than by using a light microscope.
Resolution is the ability to distinguish two points in an image as being separate.
Electron microscopy reveals that much of the cytoplasm is made up of membranes.
As well as the cell surface membrane, there are membranes around organelles such as the nucleus, mitochondria and chloroplasts.
In addition, there is an extensive system of membranes running throughout the cytoplasm, called the endoplasmic reticulum (ER).
Some ER is covered in ribosomes, and is called rough ER.
A key function of a cell membrane is to separate cell functions into different compartments so they don’t take place together.
2 The Variety of Living Organisms
Biologists put organisms into groups according to their structure and function.
The five major groups of living organisms are plants, animals, fungi, protoctists and bacteria.
Plants
All plants are multicellular
Their cells contain chloroplasts and they carry out photosynthesis
All plants have cell walls made of cellulose.
Plants can make many other organic compounds as a result of photosynthesis
Animals
Animals are also multicellular organisms
Their cells never contain chloroplasts, so they are unable to carry out photosynthesis
Animal cells also lack cell walls allowing their cells to change shape.
Fungi
Fungi include mushrooms and toadstools, as well as moulds.
These groups of fungi are multicellular.
Another group of fungi is the yeasts, which are unicellular
The cells of fungi never contain chloroplasts, so they cannot photosynthesise.
Their cells have cell walls, but they are not composed of cellulose.
When an organism feeds on dead organic material in this way, and digestion takes place outside of the organism, this is called saprotrophic nutrition.
Protoctists
Protoctists are sometimes called the ‘dustbin kingdom’, because they are a mixed group of organisms that don’t fit into the plants, animals or fungi.
Most protoctists are microscopic single-celled organisms
Some look like animal cells, such as Amoeba, which lives in pond water.
These are known as protozoa.
Other protoctists have chloroplasts and carry out photosynthesis, so are more like plants.
Eukaryotic and Prokaryotic organisms
All the organisms described so far are composed of eukaryotic cells and are known as eukaryotic organisms.
‘Eukaryotic’ means ‘having a nucleus’ – their cells contain a nucleus surrounded by a membrane, along with other membrane bound organelles, such as mitochondria and chloroplasts.
There are also organisms made of simpler cells, which have no nucleus, mitochondria or chloroplasts.
These are called prokaryotic cells.
The main forms of prokaryotic organisms are the bacteria.
Bacteria
Bacteria are small single-celled organisms.
Their cells are much smaller than those of eukaryotic organisms and have a much simpler structure.
To give you some idea of their size, a typical animal cell might be 10 to 50 µm in diameter (1 µm, or one micrometre, is a millionth of a metre).
Compared with this, a typical bacterium is only 1 to 5 µm in length and its volume is thousands of times smaller than that of the animal cell.
There are three basic shapes of bacteria: spheres, rods and spirals, but they all have a similar internal structure.
All bacteria are surrounded by a cell wall, which protects the bacterium and keeps the shape of the cell.
Bacterial cell walls are not made of cellulose but a complex compound of sugars and proteins called peptidoglycan.
Some species have another layer outside this wall, called a capsule or slime layer.
Both give the bacterium extra protection. Underneath the cell wall is the cell membrane, as in other cells.
The middle of the cell is made of cytoplasm.
Bacterium has no nucleus. Instead, its genetic material (DNA) is in a single chromosome, loose in the cytoplasm, forming a circular loop. Some bacteria can swim, and are propelled through water by corkscrew-like movements of structures called flagella.
Viruses
All viruses are parasites, and can only reproduce inside living cells.
The cell in which the virus lives is called the host.
There are many different types of viruses.
Some live in the cells of animals or plants, and there are even viruses which infect bacteria.
Viruses are much smaller than bacterial cells: most are between 0.01 and 0.1 µm in diameter Viruses are not made of cells.
A virus particle is very simple, it has no nucleus or cytoplasm, and is composed of a core of genetic material surrounded by a protein coat.
The genetic material can be either DNA, or a similar chemical called RNA.
Viruses do not feed, respire, excrete, move, grow or respond to their surroundings.
They do not carry out any of the normal ‘characteristics’ of living things except reproduction, and they can only do this parasitically.
This is why biologists do not consider viruses to be living organisms.
A virus reproduces by entering the host cell and taking over the host’s genetic machinery to make more virus particles.
Chapter 3 Breathing and Gas Exchange
Cells get their energy by oxidizing foods such as glucose, during the process called respiration.
If cells are to respire aerobically, they need a continuous supply of oxygen from the blood.
In addition, carbon dioxide from respiration needs to be removed from the body.
In humans, these gases are exchanged between the blood and the air in the lungs.
Respiration is the oxidation reaction that releases energy from foods such as glucose.
Breathing is the mechanism that moves air into and out of the lungs, allowing gas exchange to take place.
The lungs are enclosed in the chest or thorax by the ribcage and a muscular sheet of tissue called the diaphragm.
Joining each rib to the next are two sets of muscles called intercostal muscles.
The diaphragm separates the contents of the thorax from the abdomen.
The air passages of the lungs form a highly branching network.
This is why it is sometimes called the bronchial tree.
When we breathe in, air enters our nose or mouth and passes down the windpipe or trachea.
The trachea splits into two tubes called the bronchi, one leading to each lung.
Each bronchus divides into smaller and smaller tubes called bronchioles, eventually ending at microscopic air sacs, called alveoli. It is here that gas exchange with the blood takes place.
The inside of the thorax is separated from the lungs by two thin, moist membranes called the pleural membranes.
They make up a continuous envelope around the lungs, forming an airtight seal.
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The trachea and larger airways are lined with a layer of cells that have an important role in keeping the airways clean.
Some cells in this lining secrete a sticky liquid called mucus, which traps particles of dirt or bacteria that are breathed in.
Other cells are covered with tiny hair-like structures called cilia.
The cilia beat backwards and forwards, sweeping the mucus and trapped particles out towards the mouth.
Ventilation Of The Lungs
Ventilation means moving air in and out of the lungs.
This requires a difference in air pressure – the air moves from a place where the pressure is high to one where it is low.
Ventilation depends on the fact that the thorax is an airtight cavity.
When we breathe, we change the volume of our thorax, which alters the pressure inside it.
This causes air to move in or out of the lungs.
If you push the pump handle, the air in the pump is squashed, its pressure rises and it is forced out of the pump.
If you pull on the handle, the air pressure inside the pump falls a little, and air is drawn in from outside. This is similar to what happens in the lungs.
Gas exchange in the alveoli
Exhaled air is also warmer than atmospheric air, and is saturated with water vapor.
When deoxygenated blood from the heart pumps through the capillaries, the blood and the air concentration have different amounts of oxygen.
Oxygen diffuses from the air, across the wall of the alveolus and into the blood.
Carbon dioxide in the blood has a higher concentration than the air in the lungs, flowing from the blood into the alveolus.
Oxygenated blood leaves the capillaries and flows back to the heart. The heart then pumps the oxygenated blood around the body again, to supply the respiring cells.
Practical Activities
Activity 1: Comparing the carbon dioxide content of inhaled and exhaled air.
Activity 2: An investigation into the effect of exercise on breathing rate.
The Effects of Smoking
In order for the lungs to exchange gases properly, the air passages need to be clear, the alveoli need to be free from dirt particles and bacteria, and they must have as big a surface area as possible in contact with the blood.
In the trachea and bronchi of a smoker, the cilia are destroyed by the chemicals in cigarette smoke causing bacteria to block the air passages.
The reduced numbers of cilia mean that the mucus is not swept away from the lungs, but remains to block the air passages, causing a smoker’s cough, the lungs being infected from the bacteria in the mucus, and the possibility for the lung disease bronchitis.
Emphysema
Emphysema is a lung disease when smoke damages the walls of the alveoli, which break down and fuse together again, forming enlarged, irregular air spaces.
Gas exchange becomes very inefficient, and the blood of a person contains less oxygen.
There is no cure for emphysema.
Lung Cancer
Cigarette smoke contains over 7000 chemicals, more than 60 of which are known to cause cancer. These chemicals are called carcinogens, and are contained in the tar that collects in a smoker’s lungs.
After a time of quitting smoking, a person improves their chance of survival. After a few years, the likelihood of your dying from a smoking-related disease is almost back to the level of a non-smoker.
Carbon Monoxide In Smoke
One of the harmful chemicals in cigarette smoke is the poisonous gas carbon monoxide.
People who smoke during pregnancy are depriving the unborn fetus of oxygen which leads to lower mass of the baby at birth.
There are over 1 billion smokers worldwide, where about 6 million people are killed by tobacco-related illnesses.
Giving Up Smoking
The nicotine in tobacco is a very addictive drug, and causes withdrawal symptoms when people stop smoking.
To help smokers give up their habit a method include, “vaping” involving inhaling vapor containing nicotine from electronic cigarettes, and Nicotine patches or chewing gum can also be used. all providing a source of nicotine without the harmful tar.
Chapter 4 Food and Digestion
Food is essential for life.
The nutrients obtained from it are used in many different ways by the body.
Food should:
supply us with a ‘fuel’ for energy
provide materials for growth and repair of tissues
help fight disease and keep our bodies healthy.
Carbohydrates, lipids, proteins, minerals, vitamins, dietary fibre and water provide enough substances and in the correct proportions to keep you healthy.
This is all part of a balanced diet.
Carbohydrates
Carbohydrates are the body’s main ‘fuel’ for supplying cells with energy.
Glucose and other sugars belong to one group of carbohydrates.
Ordinary table sugar, the sort some people put in their tea or coffee, is called sucrose.
We can get all the sugar we need from natural foods such as fruits and vegetables, and from the digestion of starch.
Starch is a large, insoluble molecule.
Starch is a polymer of glucose – it is made of long chains of hundreds of glucose molecules joined together.
Animal cells sometimes contain a very similar carbohydrate called glycogen, glycogen is a polymer of glucose, and is found in tissues such as liver and muscle, where it acts as a store of energy for these organs.
Dietary fibre or ‘roughage’, keeps the gut contents moving, avoiding constipation and helping to prevent serious diseases of the intestine, such as colitis and bowel cancer.
Lipids (Fats and Oils)
Lipids contain the same three elements as carbohydrates – carbon, hydrogen and oxygen – but the proportion of oxygen in a lipid is much lower than in a carbohydrate.
Plant lipids are usually liquid at room temperature, and are called oils.
Vegetable oils include many types used for cooking, such as olive oil, corn oil and rapeseed oil, as well as products made from oils, such as margarine.
Lipids make up about 10% of our body’s mass.
They form an essential part of the structure of all cells, and fat is deposited in certain parts of the body as a long-term store of energy, for example under the skin and around the heart and kidneys.
The fat layer under the skin acts as insulation, reducing heat loss through the surface of the body.
The chemical ‘building blocks’ of lipids are two types of molecule called glycerol and fatty acids.
Although lipids are an essential part of our diet, too much lipid is unhealthy, especially a type called saturated fat, and a lipid compound called cholesterol.
Proteins
Proteins make up about 18% of the mass of the body.
All cells contain protein, so we need it for growth and repair of tissues, all foods contain some protein, but certain foods such as meat, fish, cheese and eggs are particularly rich in it.
Proteins are made from 20 different sub-units called amino acids.
All amino acids contain four chemical elements: carbon, hydrogen and oxygen, along with nitrogen.
Proteins are needed to make fibres of a material called connective tissue , the retina for the eye, and oxygen in blood.
Minerals
Our bodies contain many other elements that we get from our food as ‘minerals’ or ‘mineral ions’.
For example calcium, which is used for making teeth and bones.
Others are present in much smaller amounts, but still have essential jobs to do. For instance our bodies contain about 3g of iron, but without it our blood would not be able to carry oxygen.
If a person doesn’t get enough of a mineral from their diet, they will show the symptoms of a ‘mineral deficiency disease’.
A deficiency of vitamin, results in rickets, Anaemia, poor teeth, and deformed bones.
Vitamins
Experiments identified another class of food substances.
If they were fed on the same pure foods with a little added milk, they grew normally, Because the milk contained chemicals that the rats needed in small amounts to stay healthy called Vitamins.
The main Vitamins include vitamins A, C, D and the B group, for different functions.
Food Tests
It is possible to carry out simple chemical tests to find out if a food contains starch, glucose, protein or lipid.
A little starch is placed on a spotting tile. A drop of yellow-brown iodine solution is added to the starch. The iodine reacts with the starch, forming a very dark blue, or ‘blue-black’ colour.
A small spatula measure of glucose is placed in a test tube and a little water added (about 2 cm deep). The tube is shaken to dissolve the glucose. Several drops of Benedict’s solution are added to the tube, enough to colour the mixture blue.
A little protein, such as powdered egg white (albumen), is placed in a test tube and about 2 cm depth of water added. The tube is shaken to mix the powder with the water. An equal volume of dilute (5%) potassium hydroxide solution is added and the tube shaken again. Finally two drops of 1% copper sulfate solution are added. A purple colour develops.