T Level Health and Science: The Underpinning Science

The science underneath health and laboratory work is examined in small, exact pieces, and this practice is made of them. Two questions about cells ask not what an organelle is called but what it does, which is where the nucleus catches people out: it holds the instructions for a protein and does not assemble it. One asks which system carries oxygen from the lungs onward, and offers the respiratory system as the tempting answer, since that is where the oxygen arrives — but moving it to the tissues is transport, and transport is the circulatory system's job. One asks why heat stops an enzyme, where the wrong answer worth thinking about is that the enzyme is used up: it is a catalyst, released unchanged after every reaction, which is why so little of it goes so far. Then three calculations, each worked through in the explanation rather than merely answered: a concentration in grams per litre from a volume that is not a litre, a dilution where the amount of salt never changes and only the volume does, and a conversion between grams and milligrams. The set closes with what a control experiment establishes and why a balance is checked against a known mass before anyone trusts what it says. Zestly is an independent study tool. It is not affiliated with any exam board and it is not an exam centre.

• Say what mitochondria and ribosomes do, and why the nucleus is not where a protein is assembled
• Identify the circulatory system as transport, distinct from where oxygen enters the body
• Explain enzyme denaturing in terms of the active site, and why a catalyst is not used up
• Classify a substance as an element, a compound or a mixture and justify it
• Calculate a concentration in grams per litre from a volume given in millilitres
• Work out the effect of a dilution on concentration
• Convert between grams and milligrams
• State what a control experiment establishes and why equipment is calibrated

A technician dissolves 5 grams of a salt in water to make 250 millilitres of solution. What is the concentration in grams per litre? — 20. 250 millilitres is a quarter of a litre, so the same salt in a full litre would be four times as much.