CHEMISTRY Lesson 1 – Mendeleev and the first periodic table Lesson purpose: To understand how the periodic table was developed. The periodic table You probably know that the periodic table contains all of the known elements, but what you may not appreciate is the genius of the way it is organised, in fact it is so clever that it actually helps us to understand not just the properties of each element but the structure of the atoms themselves. The first modern periodic table was published in 1869 by the Russian chemist Dmitri Mendeleev (pronounced ‘Men-de-lay-ev’) long before we knew about the existence of subatomic particles such as protons, neutrons and electrons. For some time before this, chemists had tried to make their own tables of elements by placing them in order of increasing atomic mass. They found that this worked most of the time and often ended up creating columns of elements with similar properties (called groups), for example fluorine, chlorine and bromine were in the same group and do many of the same reactions. However, sometimes this didn’t work: the metal tellurium was also in this group despite being very different to fluorine, chlorine and bromine. Mendeleev’s great idea was to use not just the atomic mass to order the elements but also the chemical properties (such as the formula of its oxide, and its reaction with acids) and physical properties (such as melting point and density), and if he found that something ended up in the wrong group based on just its mass, he swapped its position to match up with the other properties. This did mean that his periodic table had some gaps, but he thought this was OK as it meant there was actually an element that belonged in the gap that just hadn’t been discovered yet. Comprehension 1 (in your book):

a) What was wrong with early periodic tables that just put elements in order of increasing mass?

b) Who developed the first modern periodic table, where was he from, and when was it published?

c) What did Mendeleev do to decide the order of elements in his periodic table? d) Name two physical and two chemical properties used by Mendeleev. e) Why did Mendeleev sometimes leave gaps in his periodic table? f) How did Mendeleev explain the gaps in his periodic table? g) Challenge: Compare Mendeleev’s periodic table with the current one.

Predictive power What made Mendeleev’s periodic table so special was its power to make predictions: a key feature of all scientific theories. The gaps in Mendeleev’s table were predictions because he said that they belonged to elements that hadn’t been discovered yet. For example, one of the gaps on his periodic table was in group III below aluminium. Using what he knew of the patterns in the chemical and physical properties of group III, Mendeleev predicted that there would be an element (which he called eka-aluminium, Ea) that would have a mass of 68, a density of 6.0 g/cm3, and an oxide with a formula of Ea2O3 and density of 5.5 g/cm3. In 1875 a new element called Gallium was discovered which had a mass of 70, a density of 5.9 g/cm3 and an oxide with a formula of Ga2O3 and density of 5.88 g/cm3. These properties were very close to the properties predicted by Mendeleev and provided a lot of evidence that Mendeleev’s ideas were correct. Mendeleev had similar success predicting the properties of other previously unknown elements such as scandium, germanium and polonium which fitted neatly into some of the other gaps he had left. Comprehension 2 (in your book):

h) What is a key feature of all good scientific theories? i) What did Mendeleev call the element that he thought belonged in the empty gap

below aluminium, and what do we call it now? j) How did the discovery of new elements prove Mendeleev’s ideas correct? k) Challenge: What roles did prediction and evidence play in the success of

Mendeleev’s ideas?

Chemistry Lesson 1b - The Modern Periodic Table Lesson purpose: To understand how the final structure of the periodic table was developed. Problems with the periodic table Whilst a brilliant start, Mendeleev’s periodic table was far from complete, and new elements continued to be discovered. A particularly interesting group of new elements was found in the late 1800s by collaboration between the Scottish scientist William Ramsay and the English scientist Lord Rayleigh. They discovered the noble gases: argon, and then neon, krypton, xenon and helium (this had been seen in the sun before, but never isolated on Earth). The noble gases were special because they were very unreactive. Mendeleev had not predicted the existence of these and had to create a new group – group 0 – for them. The existence of the noble gases was difficult to explain, as were other mysteries such as so called ‘pair reversals’ Most of the elements in the periodic table went up in order of mass, but pair reversals didn’t, for example potassium with a mass of 39 comes after argon with a mass of 40. When evidence is found that can’t be explained by a scientific theory (such as the pair reversals on the periodic table), this is usually a sign that the theory is incomplete, and that there is still more to discover. Comprehension 1 (in your book):

a) Who discovered the noble gases? b) What are the noble gases and what is special about them? c) What is a pair reversal? d) What was the problem with pair reversals? e) What did the existence of pair reversals suggest about the periodic table? f) Challenge: Study the periodic table. How many other pair reversals can you find.

State the elements and their masses for each one. Atomic Number As scientists came to accept the ordering of the elements in the periodic table, even with its pair reversals and noble gases, they gave each of the element a number: 1 for hydrogen, 2 for helium and so on. This was called the atomic number, Z. An English scientist called Henry Mosely was studying the elements by firing high energy electrons at them and measuring the x-rays that this produced. He found that the energy of the x-rays increased in direct proportion with the atomic number, which led him to conclude that the atomic number represented the number of positive charges in the atom. Other scientists came to realise that the positive charge was coming from a particle – which they called protons – and that the number of protons was equal to the atomic number. The modern periodic table is now arranged in order of increasing atomic number rather than increasing atomic mass. During Mosely’s time, elements were known from hydrogen (atomic number = 1) to uranium (atomic number = 92). However, only 85 elements had been discovered, and analysis of Mosely’s x-ray graph showed that there were seven elements yet to be discovered. Over the next few years, all seven of these gaps were filled, and the modern periodic table was complete. New elements continue to be discovered, although most are very unstable and only exist for fractions of a second, but all can be placed in the periodic table. Comprehension 2 (in your book):

g) What was the atomic number (when it was first developed)? h) Describe the experiment that Henry Mosely did. i) Describe the results of Mosely’s experiment. j) What was the name given to the positive particles that Mosely’s work pointed to? k) What is atomic number now? l) Challenge: Summarise each paragraph from this lesson in 12 words or less.

CHEMISTRY Lesson 2: Periodicity – Patterns in the Periodic Table Lesson Purpose: Describe how the properties of elements change in the periodic table

Recap 1. What is an element? 2. Who made the periodic table and how is it organised?

What is a property? (A) In science, a property is a characteristic that is used to describe how an element/chemical behaves

or reacts. Properties can be observed or measured through chemical reactions. Engineers must

consider which materials have the most suitable properties before they begin a construction project.

Physical properties describe how a substance appears or how it looks, common physical

properties that are used to describe a substance include: Colour, smell, sonorous, freezing

point, melting point, boiling point, attraction to magnets, opacity, viscosity, density,

conductivity (of heat and/or electricity), strength,

Chemical properties describe how a substance reacts (changes during chemical reactions),

common examples of chemical properties include: Toxicity, bonding, flammability, acidity,

stability.

Comprehension questions

1. State what is meant by the term ‘property’ in science (A) 2. Describe three properties of metals (A) 3. Define the terms melting point and boiling point (A) 4. Define the term sonorous (A) 5. Challenge: Compare and contrast the properties of carbon dioxide and oxygen

What is periodicity? (B) The periodic table is organised firstly by the atomic number. It is then further organised so elements with similar properties are located near each other on the periodic table. Periodicity is the tendency of elements to have similar properties when organised by their atomic number. Most of the known elements are metals, these are located on the left hand side (and middle) of the periodic table, non-metal elements are located on the right hand side of the periodic table.

Elements that have similar chemical and physical properties are organised into vertical columns known as groups. Important Groups in the Periodic Table (C) The periodic table has several groups of elements that have very distinctive properties, these are:

The Alkali Metals – All elements in Group 1 are soft, reactive metals – so soft they can be

cut with a knife. They react violently with water, to form hydrogen gas and a hydroxide – an

alkaline solution (hence the name Alkali Metal). The ferocity of these reactions increases

gradually down the group, with lithium having the smallest reaction with water to francium

having the most violent reaction. Compared to other metals the alkali metals have low

melting and boiling points and are not very dense (lithium, sodium and potassium float on

water).

The Transition Metals – This is an area of the periodic table located between groups 2 and

3. Most commonly used metals are located here. All these metals are dense, produce

colourful compounds when they react, can be hammered into shape, have high melting

points (except mercury) and are good conductors of heat and electricity.

The Halogens – Group 7 – All halogens are non-metals and poor conductors of electricity

and heat. This group has a wide range of colours that get darker as you go down the group

(Fluorine – pale yellow, chlorine – yellow/green, bromine red/brown, iodine – black/purple).

All halogens are diatomic (atoms exist in pairs). Their melting points increase as you go down

the group.

The Noble Gases – Group 0 – This group of elements are all very unreactive, colourless gases

at room temperature – for this reason they were very hard to discover. They are all non

metals.

Comprehension questions

1. State the meaning of the term ‘periodicity’ (B) 2. State where metals are found on the periodic table (B) 3. List the names and symbols of the elements known as the alkali metals 4. List the names and symbols of the elements known as the halogens 5. List the names and symbols of the elements known as the noble gases 6. Draw a table to summarise the key properties of the groups mentioned in section C (alkali

metals, transition metals, halogens and noble gases). 7. Describe the meaning of the term ‘diatomic’ with examples 8. Using named properties, suggest why copper is used to make electrical wiring 9. Fluorine is a gas at room temperature, bromine is a liquid at room temperature. Suggest

what state astatine is at room temperature and give reasons for your answer. Ext – Suggest how Mendeleev could have confirmed he had the correct order for the periodic table using experiments.

CHEMISTRY Lesson 3: Atoms, Elements and Compounds Lesson Purpose: To differentiate between atoms, elements and compounds Recap

3. What is an element? 4. What does an atom look like? 5. What is a sub atomic particle?

Bonds (A) A bond is an invisible force between two or more atoms holding them together. For ease, scientists

often show atoms as circles and bonds as a stick or line holding the circles (atoms) together. There

are many different types of bond, these include metallic bonds (bonds between two metal atoms),

covalent bonds (bonds between two non-metal atoms) or ionic bonds (bonds between metal and

non-metal atoms). The number of bonds an atom can form depends on its subatomic particles.

Comprehension questions

6. Draw a bond between two atoms. Label the atoms and the bond. (A) 7. What is a bond? 8. Describe when an ionic bond will form (A) 9. Describe when a covalent bond will form (A) 10. Suggest what kind of bond holds atoms of iron together in the leg of a chair.

Atoms and Elements (B) The words ‘atom’ and ‘element’ are often used in place of one another, but they do not mean the same thing. An atom is the smallest whole particle that can take part in a chemical reaction, it often means just one whole atom. An element can be more than one atom, as the word element means ‘made of only one type of atom’ – but it does not say how many. Some elements are diatomic – they exist in pairs, not as single atoms. This is because they are too unstable by themselves. For example the element oxygen is diatomic, it exists as O2, two oxygen atoms bonded together. Compounds, Mixtures and Molecules (C) A compound is two or more different atoms that have chemically bonded together. Oxygen (O2) is

not a compound as it is two of the same element bonded together. Carbon dioxide (CO2) is a

compound, as it is two or more different atoms that have bonded together – one carbon atom and

two oxygen atoms bonded together. When atoms combine and a new compound has been made,

we call it a molecule e.g. a molecule of carbon dioxide.

Comprehension questions

10. State the meaning of the term ‘diatomic’ (B) 11. Write a list of diatomic elements and their symbols (B) 12. State the meaning of the term atom (B) 13. State the meaning of the term element (B) 14. State the meaning of the term compound (C) 15. Draw a molecule of water. Label the elements and the bonds. 16. Explain why oxygen (O2) is not a compound (C) 17. Give two reasons why the following statement is wrong ‘An atom of water is held together

by ionic bonds’ (A, C) 18. Suggest the type of bonding found in carbon dioxide (A)

Using Molymods 1. What is used to represent a bond? 2. What colours are used to represent a) hydrogen, b) oxygen, c) carbon and d) nitrogen? 3. How many bonds can each element form a) hydrogen, b) oxygen, c) carbon and d)

nitrogen? Ext – Suggest why scientists attempt to use models to represent atoms and compounds? Ext – Evaluate the use of molymods to represent bonding. [Use page 193 Problems with Bonding Models of the Combined Science textbook to assist you].

CHEMISTRY Lesson 4: Compounds and Mixtures

Lesson Purpose: To understand why a chemical is classified as a mixture or a compound. Recap

1. Where have we discussed mixtures and compounds before? 2. What might the key difference be between these two? 3. Why do you think it can be useful to know the difference between mixtures and

compounds?

What are mixtures and compounds? (A)

A mixture is something which contains more than one type of substance, where these substances do

not react chemically. This means it is possible to separate the substances from each other using

techniques such as chromatography, distillation, or filtration. The air around us is a mixture: it

contains many different gases, such as: oxygen, nitrogen, argon, carbon dioxide, and water vapour.

A compound is like a mixture, because it contains different types of matter, but in a compound they

are chemically joined, or bonded, which means they have reacted with each other. This can

completely change the behaviour of the substance. For example, if you have mixture of oxygen and

hydrogen, you will have two gases, which can be separated physically, as they are not chemically

bonded. If these react with each other (by providing some energy with a match or a Bunsen burner),

the hydrogen and oxygen will combine to form water, a liquid.

What types of compounds are there? (B)

There are two types of compounds: ionic compounds, and covalent compounds. These are

determined by the types of bonds in the compound.

Ionic compounds are made when a metal bonds to a non-metal, for example sodium and

chlorine. Ionic compounds involve ions, which are similar to atoms, but with a charge (atoms

do not have a charge). The metal will have a positive charge, and the non-metal will have a

negative charge. Like opposite poles on a magnet, these will attract, and join to form a

compound, such as sodium chloride.

Covalent compounds are formed when two non-metals join. Instead of forming ions (as ionic

compounds do), the two non-metals simply share their electrons with each other, which

forms a bond between them. Hydrogen and oxygen are two non-metals, which form the

covalent compound, water.

Comprehension questions

11. State the meaning of “mixture”. (A) 12. Describe the difference between a mixture and a compound. (A) 13. What do mixtures and compounds have in common? (A) 14. Explain how ionic compounds are formed. (B) 15. Explain how covalent compounds are formed. (B) 16. What determines which type of compound is formed? (B) 17. Challenge: suggest why metals and non-metals form different types of ions (hint: look at

their placement on the periodic table).

What are the properties of compounds? (C)

It is not just the state of compounds which might by different when compared to a mixture.

Chemically joining two elements can produce a new material which appears completely unrelated to

the original reactants. Sodium is a very reactive metal, which will bubble violently when placed in

water. Chlorine is a highly poisonous gas. Combining these two in a chemical reaction produces the

compound sodium chloride- which is the salt we use in cooking! Changing the number of each type

of atom in a compound can also change its behaviour. If we combine 1 carbon atom (C) with 1

oxygen (O) atom, we produce carbon monoxide (CO). If we add an extra oxygen (1 carbon and 2

oxygen atoms), we produce carbon dioxide (CO2). CO is a dangerous, poisonous gas, whereas CO2 is

only dangerous to us in high concentrations, and is produced naturally by many living things

(including us).

Comprehension questions

19. Describe how a compound behaves compared to the individual chemicals inside it. (C) 20. Compare the structure and properties of carbon dioxide and carbon monoxide (C) 21. Write a word equation for the formation of: sodium chloride, carbon monoxide, and carbon

dioxide. 22. Challenge: oxygen atoms come in pairs as O2, an oxygen molecule. How many carbon atoms

are needed to form carbon monoxide with no leftover atoms? Explain your answer.

CHEMISTRY Lesson 5: Naming Compounds Lesson Purpose: To be able to name compounds, and interpret compound names to suggest the elements it contains. How do compounds get their names? (A)

Many compounds, which we know contain more than one type of atom (or element), have names

which give you a clue about which atoms it is made of, and how many. Of course, there are

exceptions to the rules, and some names of compounds cannot be split up to work out the

components: ammonia is a compound containing 1 nitrogen atom and 3 hydrogen atoms (NH3)

There are 4 general rules for naming compounds:

If the compound includes a metal, the metal name will normally come first (sodium in

sodium chloride);

The name normally ends in “–ide”, when there are just 2 elements involved (iron and

sulphur produces iron sulphide. Magnesium and oxygen produces magnesium oxide);

When there are 3 or more elements in a compound, and one of them is oxygen, the

compound will end in “–ate” (copper, sulfur, and oxygen produce copper sulfate; calcium,

carbon and oxygen produce calcium carbonate);

Prefixes can tell you how many of a certain atom there are in a compound: di- means two

(carbon dioxide, nitrogen dioxide); mono- means one (carbon monoxide).

Remember, if there are multiple atoms joined, but they are all the same type (the same element),

then they do not count as a compound- they are a molecule (for example: two hydrogen atoms

joined is H2- a molecule).

Comprehension questions (A)

1. State the meaning of the “-ide” suffix. Name an example. 2. State the meaning of the “-ate” suffix. Name an example. 3. If a compound contains a metal, where does this go in the compound’s name? 4. Does the name of a compound always describe what is found in it? Name an example. 5. Describe how a compound’s name can tell us how many of a certain atom it contains. 6. Challenge: Explain the difference between a compound and a molecule, using examples. 7. Challenge 2: Write word equations for the formation of the compounds named in part A.

Exceptions to the rules. (B)

There are several compounds which are not named according to the rules above. These must be

memorised, as they are commonly used in science:

Water: H2O

Hydrochloric acid: HCl

Sulfuric acid: H2SO4

Nitric acid: HNO3

Ammonia : NH3

Comprehension questions (B)

1. For each of the compounds above: a) State how many atoms are present. b) State how many different elements are present. c) Write a word equation for the formation of each.

2. Challenge: Write a chemical equation for the formation of each.

BIOLOGY Lesson 1: A Balanced Diet

Lesson Purpose: Describe the function of the different nutrients as part of a balanced diet

What is a balanced diet? (A) The food that we eat contains different nutrients. A balanced diet contains the different nutrients in the correct amounts to keep us healthy. Certain foods aren’t necessarily bad for us, but eating too much of them could be. The amount of each type of food needed depends on a lot of factors, such as age, gender and medical conditions. Generally speaking, the order of food types you should eat from most to least of is: rice and potatoes (also could be bread and cereals), fruit and vegetables, meat (and alternatives) then fats, oils, sugars and salts. Comprehension questions

a) State what a balanced diet is. (A) b) Describe factors that can affect the amount of different nutrients the body needs (A) c) Challenge: Produce a diagram that represents a balanced diet, using no words.

What are the different food nutrients? (B) There are five different nutrients that foods we eat contain. Each nutrient has a different function in our body.

Carbohydrates: Carbohydrates are found in foods such as cereals, rice, bread, pasta and potatoes. The function of carbohydrates is to provide energy for the body.

Protein: Proteins are found in meat, fish, eggs, beans, pulses and dairy products. Protein is used for growth and repair in the body.

Fats: Fats are found mainly in butter, oils and nuts. Fats have a few functions in the body, including being used for energy, storing energy and insulating the body against cold.

Minerals: Minerals are substances used to help maintain health in a body. Examples of minerals include calcium (which is used for healthy bones/ teeth), iron (which is used for making red blood cells) and salt.

Vitamins: Vitamins, like minerals, are substances that are used to help maintain health in the body. Vitamins are found in dairy foods, fruits and vegetables.

As well as the different nutrients, there are other important components of a healthy diet. It is also important that fibre is included in a balanced diet. Foods that are high in fibre include vegetables and bran. Fibre is insoluble, so the body can’t absorb it. Fibre’s main role is to provide roughage, which helps keep the food moving throughout the digestive system. Another important part of a balanced diet is water. Water is found in many different foods, as well as being taken as a drink. Water helps keep the body hydrated, and is needed for cells and body fluids. What affects what I should eat? (C) The amount of each different nutrient someone should eat can depend on many factors, such as gender, age, conditions and job. If you compared the diet of a growing child to an adult, the growing child would need more protein in their diet. Another example would be a professional athlete, who would need to eat more carbohydrates than someone who works in an office.

Comprehension questions

a) State the five different nutrients that our body needs from food (B) b) Describe the function of protein in our diet (B) c) State foods that contain carbohydrates (B) d) Describe the importance of fats in our diet (B) e) Explain why fibre doesn’t count as a nutrient (B) f) Suggest why a growing child’s diet should be higher in protein compared to a fully-

grown adult (C) g) Suggest why a professional athlete’s diet is different to an office worker’s diet (C) h) Challenge 1: Design a meal for a growing child, fully explaining all of your choices i) Challenge 2: Design a meal plan for a professional footballer, compared to a body

builders. j) Challenge 3: Glucoregulation is the term given to how the human body controls the

amount of sugar it carries in the blood. People with diabetes are unable to produce the hormones needed for glucoregulation. Suggest what a balanced diet would look like for a diabetic person.

BIOLOGY Lesson 2: The Digestive System

Lesson Purpose: Describe the roles of the organs in the digestive system

What is digestion? (A) When we eat food the molecules inside the food are too large for our body to absorb. These molecules are insoluble, and need to be broken down into smaller soluble substances so they can be absorbed by our bodies. This is important as useful food molecules need to pass into the blood so it

can reach cells all around our bodies. The process by which the large insoluble substances break down in to small soluble substances is called digestion. Digestion is a combination of both physical and chemical processes. Comprehension questions

a) State what digestion is. (A) b) Describe what is meant by soluble and insoluble. (A) c) Explain why digestion is important. (A) d) Challenge: Summarise the above text in no more than 10 words.

How does our body digest food? (B) Digestion takes place in an organ system called the digestive system. The digestive system is made up of the alimentary canal, which is a continuous muscular tube that runs through from the mouth to the anus. There are several important parts of the digestive system that play an important part in the digestion of food.

Mouth: Food enters the body through the mouth. The food is broken up into smaller pieces by the teeth through a physical process known as chewing. This increases the surface area of the food so that enzymes (more on that in lesson 3) contained in the saliva can work on the food more effectively. The tongue forms a ball of food called a bolus, that gets coated in saliva. Saliva has two functions, it contains enzymes that helps digest the food chemically, and it is a lubricant, making the food easier the swallow.

Oesophagus: This is a muscular tube that connects the mouth to the stomach. Muscles contract in waves, which moves the food towards the stomach. This is called peristalsis.

Stomach: This is a muscular bag that digests food both physically and chemically. The stomach churns food in a mixture of acid and enzymes, known collectively as the gastric juices. The stomach acid (hydrochloric acid) has many functions, including chemical digestion and killing any potentially harmful microorganisms in the food.

Pancreas: The organ that produces digestive enzymes, and releases them into the first part of the small intestine.

Liver: Produces bile, helping in the digestion of fats.

Small intestine: A long, coiled muscular tube where most of the large insoluble food molecules are digested into smaller soluble molecules. The digested food molecules are absorbed into the blood here, through villi (finger-shaped folds in the small intestine). The folds in the intestine, as well as the long tube, allow for a large amount of food molecules to be absorbed.

Large intestine: Undigested food molecules pass into this intestine from the small intestine. It is a wide tube, where water is absorbed back into the blood, leaving waste minerals behind.

Anus: Where undigested food is passed out of the body. Comprehension questions

a) State what the alimentary canal is (B) b) State eight organs that make up the digestive system (B) c) Describe what a bolus is (B) d) Describe the role of saliva (B) e) Describe what peristalsis is (B) f) Describe what gastric juices are (B) g) Describe examples of both physical digestion and chemical digestion (B) h) Explain how the small intestine is adapted for its role (B)

i) Challenge 1: Why might we be able to digest food upside down? j) Challenge 2: Rank the different organs from the most important to the least important,

explaining your decision.

Lesson 3: Enzymes Lesson Purpose: Describe the role of enzymes in the digestive system What are enzymes? (A) Enzymes are proteins that act as biological catalysts. Enzymes are involved in many different reactions that happen in the body, they can be used in both the synthesis and decomposition of molecules. They play an important role in the digestion of food molecules. Enzymes convert large insoluble molecules into small soluble molecules that the small intestine can absorb. Three important classes of digestive enzymes are carbohydrase, lipases and proteases. Carbohydrase convert carbohydrates into simple sugars. Amylase, an example of a carbohydrase enzyme, breaks down starch into glucose molecules. Amylase can be found in the saliva, and in the small intestine. Lipase converts fats (lipids) into fatty acids and glycerol. Proteases convert proteins into amino acids. Examples of proteases are pepsin (which is found in the stomach) and trypsin (which is found in the small intestine). Carbohydrates and proteins are examples of polymers, as they are made up of many similar small particles (known as monomers). Comprehension questions

a) State 3 different types of enzymes. (A) b) Describe the roles of enzymes in a human body. (A) c) Describe how enzymes break down carbohydrates, proteins and fats. Include what they

are broken down into. (A) d) Describe what a polymer is. (A) e) Explain why enzymes are important for digestion. (A) f) Challenge: Summarise the above text in no more than 30 words.

How do enzymes work? (B) Enzymes are made up of protein. During an enzyme-catalysed reaction, the substrate molecule (the molecule an enzyme works on) binds to the active-site (a specific region) of the enzyme. This results in the formation of a substrate-enzyme complex. When the reaction is finished, the products are released from the active site. The enzyme is unchanged, so it can be used again. Enzymes are specific (only work on one type of molecule), because each different type of enzyme has a differently shaped active site, meaning that only one type of substrate can fit in. This means that a protease enzyme would not be able to work on a carbohydrate molecule, or a lipase enzyme would not be able to work on a protein molecule. We call the way an enzyme works the lock and key hypothesis. What effects how an enzyme works? (C) The rate of enzyme-catalysed reactions is mainly affected by three factors; pH, temperature and substrate concentration.

The concentration (amount) of substrate affects the rate at which a reaction happens. As the amount of substrate increases the speed of the reaction rapidly increases – we say the rate of the enzyme-catalysed reaction increases. This affect does not last forever, eventually it does not matter how much extra substrate is added – the reaction rate cannot increase any faster as all the enzyme is being used, so the rate (speed) of the reaction levels out and becomes constant.

When temperature is increased, the rate of the reaction initially increases. This happens until the enzyme reaches its optimum temperature (the temperature the enzyme works the best at). When the temperature increases above the optimum temperature, the rate of reaction decreases rapidly. This happens because at high temperatures the enzyme will denature. Denaturing is when an enzyme changes shape, so the substrate can no longer fit in the active site (you can say that less substrate-enzyme complexes are formed). This means that the reactions can no longer happen. Most of the enzymes in our body have the same optimum temperature (37oC).

Like temperature, enzymes have an optimum pH. At the optimum pH, enzyme-catalysed reactions happen at the fastest rate. At extremes of pH, the enzyme denatures, meaning that the rate of reaction either side of the optimum pH decreases. Enzymes inside your body will have different optimum pHs, depending on where they work (e.g. enzymes that work in your stomach will work best at acidic pHs)

Comprehension questions

a) State what enzymes are made up of (B) b) State the factors that affect the rate of an enzyme-catalysed reaction (C) c) Describe what a substrate-enzyme complex is (B) d) Describe what is meant by an enzyme being specific (B) e) Describe why a protease wouldn’t work on a carbohydrate molecule (B) f) Describe how substrate concentration, pH and temperature affects the rate of an

enzyme-catalysed reaction. (C) g) Describe what is meant by an enzyme denaturing (C) h) Explain why salivary amylase wouldn’t work in the stomach (C) i) Challenge 1: Produce a flowchart that explains the lock and key hypothesis. j) Challenge 2: Produce graphs that show the rate of enzyme-catalysed reactions vs.

substrate concentration, temperature and pH

Lesson 5: Bacteria in the Digestive System Lesson Purpose: Describe the importance of bacteria in the digestive system Why do we have bacteria in our digestive system? (A) Bacteria can be found inside our digestive system, more specifically the small intestine. Some of these bacteria could cause problems, but most provide health benefits. Bacteria in our small intestine are capable of breaking down food that our body isn’t capable of digesting, meaning that we can get more nutrients from our food than if the bacteria weren’t present. As well as this, the bacteria in our small intestine can protect us against disease-causing microorganisms. Comprehension questions

1. State where in our digestive system bacteria can be found in. (A) 2. Describe the role of bacteria in our digestive system (A) 3. Suggest why it is important to have bacteria in our digestive system (A) 4. Challenge: Summarise the information in 10 words

What are functional foods? (B) Functional foods are foods that claim to make you feel healthier. These functional foods can be split into three different groups:

Probiotics: Probiotics are foods that contain live bacteria, often advertised as “friendly” bacteria. These usually belong to two different groups of bacteria, Lactobacillus and

Bifidobacteria. The foods that contain probiotics tend to be special yogurts or yogurt drinks that claim to make you healthier by improving your digestive system, helping your body protect itself against disease and reducing allergies. These claims were later rejected by the European Food Safety Agency, and many advertising campaigns had to be changed because of this.

Plant stanol esters: These are oily substances that are found in plants. These substances are capable of stopping the small intestine absorbing cholesterol, lowering the levels of cholesterol in the blood. These are used in many yogurts, drinks and spreads, and there is clear scientific evidence that they have a positive effect on the human body.

Prebiotics: These are substances that the body can’t digest. They act as food for the “friendly” bacteria in the gut and encourage their growth. Common forms of prebiotic are oligosaccharides, that are found naturally in tomatoes, onions, bananas and asparagus. These can also be found in special dairy products. There is growing evidence that prebiotics have a positive effect on the digestive system.

Comprehension questions

1. State what a functional food is (B) 2. State the three different groups of functional foods (B) 3. Describe probiotics (B) 4. Describe plant stanol esters (B) 5. Describe prebiotics (B) 6. Explain why companies that produced probiotic foods had to change their advertising

campaigns (B) 7. Challenge: Rank the three different functional food groups, from the one you would

recommend the most to the one you would recommend the least. Include a full reason for your choice

8. Challenge: Suggest why you think that most probiotic foods are in the form of dairy products

Lesson 8: Nutrient Deficiency Lesson Purpose: Describe diseases that are caused by malnutrition Recap Questions

1. What do we use protein for? 2. Why do we need to have a source of calcium in our diet? 3. What would happen if we ate to much sugar in our diet?

What can happen if we don’t get enough of the nutrients we need? (A)

To grow healthily we need to have a diet that is balanced (contains the right amount of the

different nutrients). If our diet is unbalanced, either through not eating enough of a certain

nutrient or eating too much of another, then it can cause problems to our body.

Malnutrition is a disorder that is caused by either having too much of a certain nutrient

(over-nutrition) or not enough of a nutrient (under-nutrition).

Below is a table that contains information about different diseases caused by malnutrition:

Name Cause Symptoms

Obesity Excess of high energy foods (e.g. sugar, fats, carbohydrates)

Increase risk of heart disease and some cancers. Can lead to type 2 diabetes.

Kwashiorkor Lack of protein Swelling of stomach, feet, legs and hands. Wasted muscles and growth failure.

Scurvy Lack of vitamin C Bleeding around the gums of the teeth. Bruising and swelling of the bone joints.

Rickets Lack of vitamin D Causes bones to become soft and bow (bend).

Iron Anaemia Lack of iron Fatigue (very tired). Pale gums.

Comprehension questions

5. State what malnutrition is (A) 6. Describe the differences between over-nutrition and under-nutrition (A) 7. Describe the symptoms someone might show if they have too much fat in their diet (A) 8. Someone is suffering from swelling of their joints. Suggest what they should do to treat this

symptom. 9. Challenge: Iron is used by our bodies in the production of red blood cells. Suggest an

explanation of the symptoms shown by someone suffering from iron anaemia. What are the problems with obesity? (B)

Obesity is a disease that is caused by the consumption of excess high energy foods. It is

increasingly becoming a concern in the UK, with one in four British adults now being

classified as obese. As well as the problems shown in the table above, obesity is linked to

cardiovascular disease (CVD), which effects the ability of the circulatory system to function

properly. Signs of cardiovascular disease include high blood pressure, which can lead to

heart problems (from feeling pain to a heart attack). To work out if someone is classified as

obese, doctors measure their body mass index (BMI). This is done by using the equation

below:

BMI = mass (kg) ÷ height2 (m2)

An adult with a BMI above 30 is classified as being obese. Cardiovascular disease can be

treated, through either surgical methods or a change in lifestyle.

Comprehension questions

1. State how many adults in the UK are classified as obese (B) 2. State what CVD stands for (B) 3. State the equation used for calculating BMI (B) 4. Describe what CVD is (B) 5. GCSE style question:

In 2014, nearly 155 000 people died from cardiovascular disease in the UK.

Figure 6 shows information about the BMI and the lifestyle of two males, P and Q, who

have the same height and age.

Figure 6

(i) What measurements are used to calculate BMI? (1 mark)

(ii) Explain which male has a greater risk of developing cardiovascular disease. (3 marks)