Q11. Examine each of the monosaccharides below identified as hexoses.

Background

Topic: Carbohydrates – Monosaccharides

This question tests your understanding of the structure and properties of monosaccharides, specifically hexoses, and the concept of isomers in biological molecules.

Key Terms and Formulas:

• Monosaccharide: The simplest form of carbohydrate, consisting of a single sugar molecule.

• Hexose: A monosaccharide with six carbon atoms.

• Isomer: Molecules with the same molecular formula but different structural arrangements.

• Molecular formula for hexoses:

Step-by-Step Guidance

1. Observe the structural diagrams of glucose, fructose, and galactose. Notice that each has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

2. Write out the molecular formula for each monosaccharide based on the number of atoms present.

3. Compare the structures: even though the molecular formula is the same, the arrangement of atoms differs. This is the definition of isomers.

4. Consider why these molecules are called hexoses: count the carbon atoms in each structure.

5. To finish, summarize the molecular formula and explain the concept of isomers and hexoses.

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Q15. Identify the monosaccharide monomers in each molecule.

Background

Topic: Carbohydrates – Disaccharides

This question tests your ability to recognize the monosaccharide components that make up common disaccharides such as sucrose and lactose.

Key Terms and Formulas:

• Disaccharide: A carbohydrate formed by the joining of two monosaccharides.

• Monomer: A single molecule that can join with others to form a polymer.

• Sucrose: Common table sugar, made from glucose and fructose.

• Lactose: Milk sugar, made from glucose and galactose.

Step-by-Step Guidance

1. Look at the structural diagrams for sucrose and lactose. Identify the two monosaccharide units in each.

2. Recall that sucrose is formed from glucose and fructose, while lactose is formed from glucose and galactose.

3. Examine the bond connecting the two monosaccharides in each disaccharide. This is a glycosidic bond.

4. Label the monosaccharide monomers for each molecule based on their structure.

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Q27. On the images below, identify the cis and the trans fat.

Background

Topic: Lipids – Fatty Acids

This question tests your understanding of the structural differences between cis and trans unsaturated fatty acids and their biological significance.

Key Terms and Formulas:

• Cis fat: Unsaturated fatty acid with hydrogen atoms on the same side of the double bond, causing a bend in the molecule.

• Trans fat: Unsaturated fatty acid with hydrogen atoms on opposite sides of the double bond, resulting in a straighter molecule.

• Double bond: A chemical bond where two pairs of electrons are shared between atoms.

Step-by-Step Guidance

1. Examine the two fatty acid structures. Notice the position of the hydrogen atoms around the double bond.

2. Identify which structure is bent and which is straight. The bent structure is characteristic of cis fats, while the straight structure is typical of trans fats.

3. Label the left and right images as trans and cis fats, respectively, based on their structural features.

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Q50. Label the DNA molecule: A: phosphate, B: thymine, C: adenine, D: 5’, E: guanine, F: cytosine

Background

Topic: Nucleic Acids – DNA Structure

This question tests your ability to identify the components of a DNA molecule, including the phosphate group, nitrogenous bases, and the directionality of the DNA strand.

Key Terms and Formulas:

• Phosphate group: Part of the backbone of DNA.

• Nitrogenous bases: Thymine, adenine, guanine, cytosine.

• 5’ (five prime): Indicates the directionality of the DNA strand.

Step-by-Step Guidance

1. Examine the labeled diagram of the DNA molecule. Identify the phosphate group (A), the nitrogenous bases (B, C, E, F), and the 5’ end (D).

2. Match each label to its corresponding component in the DNA structure.

3. Recall the base pairing rules: adenine pairs with thymine, guanine pairs with cytosine.

4. Label each part based on its position and structure in the diagram.

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