Biological Molecules
Overview
Every living thing is built from a small set of molecules: carbohydrates, fats and proteins, plus the information molecule DNA. The clever part is that giant molecules are assembled from simple repeating units, like words built from a few letters, which gives living tissue its huge variety from just a handful of building blocks.
In this lesson you will learn which elements make up each food group, the small units they are built from, and the chemical tests that reveal starch, sugars, proteins, fats and vitamin C. At Extended level you will also meet the double-helix structure of DNA and its base-pairing rule.
Objectives
- List the chemical elements that make up: carbohydrates, fats and proteins
- State that large molecules are made from smaller molecules, limited to: (a) starch, glycogen and cellulose from glucose (b) proteins from amino acids (c) fats and oils from fatty acids and glycerol
- Describe the use of: (a) iodine solution test for starch (b) Benedict’s solution test for reducing sugars (c) biuret test for proteins (d) ethanol emulsion test for fats and oils (e) DCPIP test for vitamin C
- [Supplement] Describe the structure of a DNA molecule: (a) two strands coiled together to form a double helix (b) each strand contains chemicals called bases (c) bonds between pairs of bases hold the strands together (d) the bases always pair up in the same way: A with T, and C with G (full names are not required)
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Lesson Evaluation
Congratulations on completing the lesson on Biological Molecules. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Carbohydrates contain only carbon, hydrogen and oxygen. Which further element is always present in proteins as well? A. nitrogen B. phosphorus C. calcium D. chlorine Answer: A
- The reagent used to test for starch is: A. Benedict's solution B. iodine solution C. biuret reagent D. DCPIP Answer: B
- A positive Benedict's test (after heating) gives a final colour of: A. blue B. purple C. brick-red/orange D. green only Answer: C
- Proteins are built from sub-units called: A. glucose B. amino acids C. fatty acids D. glycerol Answer: B
- In a DNA molecule, adenine on one strand always forms a base pair with which base on the opposite strand? A. cytosine B. guanine C. thymine D. uracil Answer: C
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