These seven original questions follow the four lessons in the chapter. Answer in full sentences first, then open the model answer.
Questions
Question 1. State the building blocks of carbohydrates and of proteins.
Answer
Carbohydrates are built from simple sugars such as glucose. Proteins are built from amino acids.
Question 2. Name the element found in proteins but not in carbohydrates.
Answer
Nitrogen. Both contain carbon, hydrogen and oxygen, but proteins also contain nitrogen.
Question 3. State one function of lipids in the human body.
Answer
Lipids store energy. A layer of fat under the skin also insulates the body and reduces heat loss.
Question 4. Explain why cooked egg white does not turn back into a liquid when it cools.
Answer
Egg white is mostly protein. Heat changes the protein’s shape, which is denaturation.
The protein does not refold into its original shape on cooling, so the change is permanent.
Question 5. A food sample turns blue-black with iodine solution and stays blue with Benedict’s solution after heating. State the conclusions.
Answer
Starch is present. Reducing sugar is not shown.
The blue Benedict’s result does not rule out non-reducing sugars such as sucrose.
Question 6. A student adds biuret solution to a liquid and it turns purple. What does this show, and what would a blue result show?
Answer
Purple shows that protein is present. A blue result would show that protein is not shown in the sample.
Question 7. State two roles of water in living things and the job of DNA.
Answer
Water is a solvent that dissolves substances and a transport medium in blood. It also acts as the medium for chemical reactions in cells.
DNA stores the genetic information that carries the instructions for making proteins.
If you got these wrong
Questions 1 to 3 point to comparing carbohydrates, proteins and lipids. Question 4 uses relating molecular structure to function.
Questions 5 and 6 need interpreting food-test results conceptually. Question 7 comes from explaining the roles of water and nucleic acids.
Log each slip in the mistake log and paper-error review, then build a timed set with the timed original practice session builder.
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