B4 quiz: enzymes
Ten think-time questions on enzymes: catalysts, the active site, specificity, temperature, pH and the amylase practical. Below the video: written workbook questions with model answers.
Practice
- B4 Enzymes: workbook questions – Eight written questions with model answers: write your answer, check it, and tick the marks you earned. Vietnamese help for every question.
Transcript
Ten quick questions on enzymes. Listen, think, then check your answer.
Question one. Enzymes are made of: A, carbohydrate. B, protein. Or C, fat.
The answer is B, protein. Enzymes are proteins that work as biological catalysts.
Question two. A biological catalyst is a substance that: A, speeds up a reaction and is not used up. B, gives energy to a reaction. Or C, is used up in the reaction.
The answer is A. A catalyst speeds up a reaction, and it is not used up, so it can work again.
Question three. What is the substrate? A, the molecule that the enzyme changes. B, the new molecule that is made. Or C, the part of the enzyme where it fits.
The answer is A. The enzyme changes the substrate. The new molecules are the products, and the place where it fits is the active site.
Question four. Where does the substrate fit on an enzyme? A, the product. B, the active site. Or C, the cell membrane.
The answer is B, the active site. The enzyme and the substrate together form the enzyme substrate complex.
Question five. Why does amylase break down starch but not protein? A, the active site is complementary to starch only. B, amylase is not a protein. Or C, protein molecules are too big.
The answer is A. Only the right shape fits the active site, so each enzyme is specific.
Question six. As the temperature rises towards the optimum, the rate increases because molecules have more: A, kinetic energy. B, mass. Or C, active sites.
The answer is A, kinetic energy. The molecules move faster, so there are more effective collisions.
Question seven. What happens to an enzyme at a very high temperature? A, it works faster. B, its shape changes, and it is denatured. Or C, it makes more products.
The answer is B. The active site changes shape, so the substrate no longer fits.
Question eight. What is the optimum temperature for most human enzymes? A, four degrees Celsius. B, thirty seven degrees Celsius. Or C, eighty degrees Celsius.
The answer is B. About thirty seven degrees Celsius, which is normal body temperature.
Question nine. Pepsin works in the acid stomach. Its optimum P H is most likely: A, P H two. B, P H seven. Or C, P H twelve.
The answer is A, P H two. Pepsin works best in acid. Amylase in saliva prefers P H seven.
Question ten. In the amylase experiment, which colour shows that starch is still present? A, orange brown. B, blue black. Or C, colourless.
The answer is B, blue black. Iodine turns blue black with starch. Orange brown means no starch is left.
Quiz complete. Review any topic you missed, and watch the video again.
More in this series
5:53B4 Enzymes: key vocabulary
Twelve key words for IGCSE Co-ordinated Sciences topic B4, with the Vietnamese meaning, how to say each word, a picture and an example. Ends with a test section, and a typing trainer on the site.
1:41What are enzymes?
Why the body needs catalysts, what a catalyst does, and why enzymes are proteins that work as biological catalysts. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
1:40How enzymes work
The active site, the substrate, the enzyme-substrate complex and the products; why complementary shapes make an enzyme specific. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
2:14Enzymes: temperature and pH
Why a higher temperature speeds up an enzyme, what the optimum is, and how heat or the wrong pH changes the shape of the active site (denaturation). With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
2:16Investigating enzymes: temperature and pH
A practical with amylase, starch and iodine on a spotting tile: how to test the effect of temperature and pH, keep it a fair test and read the results. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.