How to pass your GCSE Science exam

These are topics you should know well in order to pass GCSE Science.

Tip 1 – Experiments involving enzymes

Each year in one form or another there is a question about an enzyme. A favourite is ‘catalase’ which breaks down hydrogen peroxide in cells. The questions, however, normally concern a property of all enzymes – and that is the range of temperatures in which enzymes can be active.

The body temperature of humans is about 36.8 degrees C because this is the optimal (best) temperature for enzymes to be active.

As the temperature climbs towards 40 degrees C and even higher the enzymes become less active. At very high temperatures they become ‘denatured’ – in other words ‘dead’.

As the temperature drops below the optimal value – below 20 degrees C and even lower – the enzymes again become less and less active. This is not because they become denatured but because as the body’s cells get colder and colder, there are less and less collisions with the molecules the enzymes are meant to act on.

Usually the exam question is all wrapped up in some type of experiment. But at the heart of the question is this general property of how temperature affects the activity of enzymes.

Tip 2 – Photosynthesis and respiration

You must be clear about the difference between these two processes in plants.

For photosynthesis to happen you must have light falling onto a plant’s leaves. So photosynthesis cannot occur at night.

Respiration is when every cell of the plant is involved with combining oxygen with glucose to give the plant the energy to grow and to live. So respiration must occur day and night otherwise the plant would die!

In other words all living plants continually respire, but only photosynthesize in light.

Questions concerning this difference sometimes have plants under a ‘black cover’ or in a ‘dark box’. But what they are testing is whether you understand the difference between these two processes?

Tip 3 – The heart

Another favourite question is testing if you understand which blood vessels are involved in a heart attack.

Most of you will first learn the names of the blood vessels that bring blood to the heart and which vessels carry blood away from the heart. But these are not usually the ones involved in a typical heart attack.

The heart is a pump. It is a beating muscle and, as such, it needs a good supply of blood bringing plenty of oxygen. The blood vessel that brings this blood to the muscle of the heart is called the coronary artery. It enters the heart’s muscle from the outside of the heart. It is not involved with the pumping of blood.

It is the coronary artery becoming blocked – thus restricting the supply of fresh blood to the heart muscle – that causes a heart attack.

Tip 4 – A chemical formula



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