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Introduction to the lesson
Building on your knowledge from the last lesson, we will now begin to explore carbohydrates in more detail. In this lesson, we will learn about one particular kind of monomer -- monossacharides -- which join together to form polysaccharides. We will study how they join together to make disaccharides and polysaccharides in the next lesson. Learn the structural formulae and ring structures of all these molecules well you will be expected to know them in the exam.
Introduction to monosaccharides
Read section under the heading "Monosaccharides" in your text book (p.29).
Learning Activity 1
Answer the following questions in your exercise book.
- Name the three elements that make up monosaccharides.
- Give the general formula of monosaccharides.
- What do the prefixes of monosaccharides indicate?
- Name three common hexoses.
- Name two common pentoses.
Molecular and structural formulae
Read the section under the heading "Molecular and structural formulae" in your text book (p.30).
Learning Activity 2
Answer the following questions in your exercise book.
- Write the molecular formula of a hexose.
- Draw the common structure of glucose. Take note of the five hydroxyl groups (OH) – see Figure 2.3 (p.30).
Ring structures
Read the section under the heading "Ring structures" in your text book (p.30).
Learning Activity 3
Answer the following questions in your exercise book.
- Draw an α-glucose (alpha-glucose) and a β-glucose (Beta-glucose) (cf. Fig.2.4, p.30). Learn these structures well – you may be required to draw them in the exams
- What is the difference between the two forms?
- Note that the same molecule can switch between these two forms
- What term is used to refer to different forms of the same chemical?
- Answer Question 2.1 on p.30
Roles of monosaccharides in living organisms
Read the section "Roles of monosaccharides in living organisms" in your text book (p.31).
Learning Activity 4
Answer the following questions in your exercise book.
- Explain the role of monosaccharides as a source of energy in respiration
- What is ATP and ADP?
- What is another role of monosaccharides?
Definitions and review
Definitions
- Monosaccharide
- Sugar
- Triose
- Pentose
- Hexose
- Molecular formula
- Structural formula
- Isomer
Mindmap
Add this section to your chapter two mindmap.