Chapter 5:Sources of Energy

1. Higher Human Biology Unit 1: Cell Function and Inheritance Chapter 5:Sources of Energy Mrs Smith: Ch5 Sources of Energy.

2. Learning intentions. • To compare the differences between mono-, di- and poly-saccharides • To examine the structure of lipids and their various roles in cells and organisms • To study protein degradation and their use as an alternative respiratory substrate Mrs Smith: Ch5 Sources of Energy.

3. Carbohydrates. • Carbohydrates (e.g. Sugar, starch and glycogen) are compounds whose molecules all contain the chemical elements CARBON (C), HYDROGEN (H) and OXYGEN (O). Mrs Smith: Ch5 Sources of Energy.

4. Monosaccharides (single-sugar) • This is a simple sugar. • Made up of six-sided unit, galactose, glucose and fructose are examples of these • Monosaccharide's are soluble in water. • Described as reducing sugars. Mrs Smith: Ch5 Sources of Energy.

5. Disaccharides (double-sugar) • Made of two monosaccharides joined together. • Maltose and sucrose are examples of disaccharides. • Disaccharides are soluble in water. • Maltose has reducing properties. • Sucrose is a non-reducing sugar. Mrs Smith: Ch5 Sources of Energy.

6. Polysaccharides • A polysaccharide is a carbohydrate composed of many monosaccharide molecules joined together. • These molecules are all very large and insoluble in water. • ALL CARBOHYDRATES ARE RICH SOURCES OF ENERGY Mrs Smith: Ch5 Sources of Energy.

7. Starch • This polysaccharide consists of a long chain of glucose (>1000 monosaccharide units). • These molecules are all very large and insoluble in water. • Starch is the form in which plants store carbohydrate. Mrs Smith: Ch5 Sources of Energy.

8. Glycogen • This polysaccharide is very similar to a branched form of starch. • These molecules are also very large and insoluble in water. • This means glycogen cannot diffuse out of the cell and they do not affect the cells osmotic balance • This makes it an ideal storage material, particularly abundant in liver and muscle cells. Mrs Smith: Ch5 Sources of Energy.

9. ENERGY • ALL CARBOHYDRATES are a rich source of ENERGY. • Monosaccharide's can be used to release energy. (e.g. glucose can undergo glycolysis during respiration) • However disaccharides and polysaccharides must be broken down by enzymes before they can release their energy. Mrs Smith: Ch5 Sources of Energy.

10. Identifying unknown carbohydrates Mrs Smith: Ch5 Sources of Energy.

11. TASK • Testing your knowledge: Please complete Torrance pg38 Qu’s 1-3. Mrs Smith: Ch5 Sources of Energy.

12. Lipids • This is a diverse group of organic compounds including fats, oils, phospholipids and steroids. • Lipids contain the elements C, H and O. (but the proportion of oxygen in lipids is smaller than in carbohydrates). • LIPIDS ARE INSOLUBLE IN WATER Mrs Smith: Ch5 Sources of Energy.

13. Triglyceride (Simple lipid) • Fat (solid at rm temp) and oil (Liquid at rm temp) are examples of triglycerides. • Their molecular structure consists of a glycerol and 3 fatty acids. Mrs Smith: Ch5 Sources of Energy.

14. Phospholipids • A typical phospholipid contains two molecules of fatty acids linked to one glycerol, in addition it has one phosphate on the third position of the glycerol Mrs Smith: Ch5 Sources of Energy.

15. Phospholipids- different properties at each end! • The phosphate (‘head’) end of the molecule is hydrophilic (water loving) and is therefore soluble in water. • The fatty acid (‘tail’) end of the molecule is hydrophobic (water-hating) and is therefore insoluble in water. Mrs Smith: Ch5 Sources of Energy.

16. Phospholipid example. Mrs Smith: Ch5 Sources of Energy.

17. Steroids • Steroids are lipids, however their structure varies from simple and phospholipids. • Each molecule of a steroid has a basic structure composed of 3 6-carbon rings joined to a 5-carbon ring. • Cholesterol is an example of a steroid. It provides the basic molecular structure from which other steroids are formed (bile and sex hormones). Mrs Smith: Ch5 Sources of Energy.

18. Steroids Mrs Smith: Ch5 Sources of Energy.

19. Roles of Lipids • Energy store • Thermal and nerve insulation • Fat pads • Vitamin transport • Hormones • Major components of the plasma membrane Mrs Smith: Ch5 Sources of Energy.

20. Roles of Lipids: Energy store • Fat is deposited in fatty (adipose) tissue. • It is insoluble and compact making it an ideal form in which to store energy. • When energy is required, a fat molecule is broken down into glycerol and fatty acids which become available for use in aerobic respiration. • Fat liberates more than double the quantity of energy than the same mass of carbohydrate. Mrs Smith: Ch5 Sources of Energy.

21. Roles of Lipids: Thermal and nerve insulation. • The fat beneath the skin also serves as a INSULATOR to help conserve body heat. • The sheath around each nerve fibre consists of a fatty material called myelin, this insulated the nerve and increased the speed of the impulses. Mrs Smith: Ch5 Sources of Energy.

22. Roles of Lipids: Fat Pads • Pads of fat in the palms of the hands and soles of the feet protect the underlying structures by acting as cushions. • The kidneys are also protected by fat pads. Mrs Smith: Ch5 Sources of Energy.

23. Roles of Lipids: Plasma membrane • Phospholipids are one of the basic building blocks of cell membranes. • The steroid cholesterol is also an important components of membranes. Mrs Smith: Ch5 Sources of Energy.

24. Proteins • Proteins broken down into amino acids. • Excess amino acids cannot be stored in the body. • They are deaminated into urea and organic compounds. • These organic acids enter the respiratory pathway to produce some ATP Mrs Smith: Ch5 Sources of Energy.

25. Starvation • Tissue protein is used as a source of energy only during prolonged starvation when the reserves of glycogen and fat have become exhausted. • Skeletal muscle and other tissues rich in protein are used up to produce energy during the crisis. Mrs Smith: Ch5 Sources of Energy.

26. Marathon Running • In the first few minutes the body uses glucose from muscle glycogen. • Blood glucose mainly from liver glycogen is used for the next 30 minutes • As glucose supplies decrease fatty acids become the energy supply. Mrs Smith: Ch5 Sources of Energy.