CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES

1. CHAPTER 5 THE STRUCTURE AND FUNCTION OF MACROMOLECULES Polymer principles And Macromolecules Page 62

2. Polymers principles • Cells join تربط smaller organic molecules (Monomers) together to form larger molecules (macromolecules) (Polymers), which may be composed of thousands of atoms. • The four major classes of macromolecules are: • -Carbohydrates, • -Lipids, • -Proteins, • -Nucleic acids (will be studied later)

3. Monomers are connected by covalent bonds bya dehydration reaction تفاعل نزع الماء. • One monomer provides a hydroxyl group and the other provides a hydrogen to form water. • This process requires energy and is aided by enzymes. • The covalent bonds connecting monomers in a polymer are disassembledتـُكسَــر by hydrolysis (hydration) reaction تفاعلإضافة الماء. • In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. • Hydrolysis reactions dominate the digestive process, guided by specific enzymes. Fig. 5.2a & b, Page 63

4. أحادى عديد ثنائى (Carbohydrates, Lipids, Proteins and nucleic acids) Mono-mer Di-mer Poly-mer Polymer is a long molecule consists of a chain of similar building molecules (monomers) covalently bounded together. Page 62 – 63, Fig. 5.2

5. 1- Carbohydrates Fuel and BuildingMaterial (مادة الطاقة و البناء ) • Monosaccharides, are the simplest carbohydrates (simple sugars). • Disaccharides, double sugars, consist of two monosaccharides joined by dehydration. • Polysaccharides, are polymers of many monosaccharides.

6. Aldehyde sugars Aldose Aldose H O H O C C Glucose C Galactose H OH C H OH C6H12O6 C6H12O6 C OH H C OH H C H OH C OH H C H OH Asymmetric C C H OH Asymmetric C C H OH C H OH H H 1- Monosaccharides Page 64, Fig. 5.3

7. Triose Sugar Pentose Sugar Hexose Sugar H H OH H O C C H O Ketose C C O Fructose C H OH C6H12O6 C C H OH OH H C H OH C H OH C H OH C H OH H C H OH C H OH C H OH H Glyceraldehyde H Ribose Ketone sugar Page 64, Fig. 5.3

8. Monosaccharides are classified as following :- A- Based on the location of C=O Aldoses: are the monosaccharides of carbonyle group (C=O) at the end of C chain (e.g. Glucose). Ketoses: are the monosaccharides of C=O carbonyle group within داخل the C chain (e.g. Fructose). B- Based on the number of C in the skeleton Triose (3C): e.g. Glyceraldehyde. Pentose (5C): e.g. Ribose. Hexose (6C): e.g. Glucose, Fructose and Galactose.

9. 2- Disaccharides السكر الثنائى Consisted of 2 monosaccharide molecules during a dehydration reaction تفاعل نزع الماء. Sucrose (table sugar): consists of Glucose + Fructose. Fig. 5.5, Page 65 FIG. 5.5a, Page 65

10. 3- Polysaccharides السكر العديد Consisted of few hundreds to few thousands of monosaccharides. They are two types: 1- Storageتخزينية. Provide sugar for cell by hydrolysis إضافة ماء. 2- Structural تركيبية. Serve as building materials for the organism.

11. A)- Storage نخزينية Polysaccharides I- Starch (in plants) النشا A storage polysaccharide of plants (within plastids). It is consisted of thousands of glucose molecules. Thus, it gives glucose when hydrolysed بإضافة الماءby special enzymes in human. Potatoes and grains are the major source of starch. Fig. 5.7, Page 67

12. II- Glycogen (in animals)الجليكوﭽـين Stored in animal cells (e.g. liver and muscle cells in Human). It is consisted of thousands of glucose molecules. Thus, it gives glucose when hydrolysed. Fig. 5.7, Page 66

13. B)- Structural تركيبية Polysaccharides I- Cellulose It is the building material of plants (cell wall). Forms the micro-fibrils and cell wall in plants. It is consisted of thousands of βglucose molecules. Human cannot digest it, but some bacteria and protozoa can (e.g. in Termites and Cows stomach). Fig. 5.7c, Page 67

14. II- Chitin الكيتين It is the building material of the cuticleالجُـلَيدin insects. It is consisted of thousands of glucose molecules with a N atom in one end. It is used to manufacture the surgical threads. Fig. 5.9, Page 68

15. Triose (3C) Glyceraldehyde Pentose (5C) Ribose Hexose (6C) Glucose Monosaccharides Polysaccharides Disaccharides Glucose & Fructose Maltose & Sucrose Location of Carbonyl Group Storage Structural Starch (inplants) & Glycogen (inanimals) Cellulose (inplants) & Chitin (ininsects) Aldose Ketose C=O on top C=O in chain Carbohydrates No. of C atoms No. of sugar molecules

16. H O H C C N OH R Amino group Carboxyl group H Side chain 2-Proteins - Protein is a polymer of amino acids (constructed from 20 amino acids) (to form Polypeptides). - These components include ahydrogen atom, a carboxyl group, an amino group, and a variable متغيرةR group (or side chain). General Formula of the Amino Acid: - The side chainR links with ترتبط بـ different compounds - Differences in R groups produce the 20 different amino acids.

17. Amino acids الأحماض الأمينية • Hydrophobic: the amino acids that have hydrophobic R groups (non-polar). 2- Hydrophilic: the amino acids that have polar R groups, making them hydrophilic. 3- Ionized: the amino acids with functional groups that are charged (ionized) at cellular pH (7). So, some R groups are bases, others are acids. Fig. 5.15, Page 72

18. H H O N C C OH R Peptide bond Amino acids Peptide Polypeptide (Protein) The Peptide Bondالرابطة البيبتيدية Peptide bond formed between the carboxyl group of one amino acid and the amino group of the other by dehydration. O H H N C C H OH H R Dehydrationنزع الماء Page 73, Fig. 5.16

19. Amino acids are joined together when a dehydration reaction removes a hydroxyl group from the carboxyl end of one amino acid and a hydrogen from the amino group of another. The resulting covalent bond is called a peptide bond. • The repeated sequence (N-C-C) is the polypeptide backbone. • Attached to the backbone are the various R groups. • Polypeptides range in size from a few monomers to thousands. Fig. 5.16, Page 73

20. Polypeptides Proteins Peptide ponds Peptides Dehydration Hydrophobic (non-polar R group) Amino acids Hydrophilic (polar R group) Ionized (charged functional groups)

21. 3-Lipids; • 1.Fats store large amounts of energy • Phospholipids are major components of cell membranes • Steroids include cholesterol and certain hormones Pages 69-71

22. O H C H C C C C C H C C H OH H C OH H H H H H H H H H H H Glycerol Fatty Acid OH H O Ester link Dehydration In a fat, three fatty acids are joined to glycerol by an ester linkage, رابطة إستيريةcreating a triacylglycerol. Fig. 5.10, Page 69

23. A)- Saturated Fatsالدهون المشبعة The Fatty acid components are saturated (there is no double bonds between the carbons. All C are linked with H. Thus, it is saturated with H. Most animal fats are saturated. They are solid at room temperature. Saturated fats-rich diet results in Atherosclerosisالتصلب الشريانى. B)- Un-saturated Fatsالغيرمشبعةالدهون These double bonds are formed by the removal of H atoms. Most vegetable fats (oils)and fish fats are unsaturated. They are liquid at room temperature. They can be synthetically converted to saturated (solid) by adding H (Hydrogenation الهَدْرَﭽـَة).

24. Phospholipids;Are major components of cell membranes • Phospholipids have two fatty acids attached to glycerol and a phosphate group at the third position. • The phosphate group carries a negativecharge. • The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilichead. • Thus, it is amphipathic Fig. 5.12, Page 70

25. At the surface of a cell, phospholipids are arranged as a bilayer طبقة مزدوجة. • Again, the hydrophilic heads are on the outside in contact with the aqueous solution المحلول المائى and the hydrophobic tails from the core المركز. • The phospholipid bilayer طبقة مزدوجةforms a barrier حاجز between the cell and the external environment البيئة الخارجية. • They are the major component of cell membranes.

26. Hydrogenation هَـدْرَﭽـَــــــــة F a t s (Composed of Lipids) Saturated Unsaturated Phospholipids Steroids Animal Fats Vegetable Fats Bi-layer of cell membrane Sex Hormones & Cholesterol