IB Biology Review Topic 3: Chemistry of Life Vocabulary Macromolecule term used to describe large molecules such as carbohydrates, lipids, proteins, and nucleic acids Monomer the repeating unit molecules of polymers Polymer a long chainlike molecule consisting of repeating building-block molecules linked by covalent bonds includes proteins, carbohydrates, and nucleic acids What are the four groups of macromolecules? Carbohydrates Lipids Proteins Nucleic Acids Examples of Monomers What are the monomers of Carbohydrates Simple sugars (monosaccharides) like glucose and fructose make polysaccharides Proteins 20 different amino acids form polypeptides Nucleic Acids Nucleotides (A, T, G, C, and U) form DNA and RNA How are monomers linked and unlinked? Linked by condensation/dehydration reaction A molecule of water is removed to form a bond Anabolic reaction • Unlinked by hydrolysis reaction – – A molecule of water is added to break a bond Catabolic reaction Two Types of Covalent Bonds that Join Monomers Saccharide bonds join two adjacent monosaccharides Peptide bonds join two adjacent amino acids MC-1.Which of the following reactions occurs when a dipeptide is formed from amino acids? A. B. C. D. hydrolysis denaturation condensation oxidation Correct answer: C Special Types of Bonds Two monosaccharides are joined by a saccharide bond • Two amino acids are joined by a – peptide bond DNA Structure 1. Alternating sugar and phosphate molecules 2. Bases are towards center (A/T) (G/C) 3. Hydrogen bond connects adjacent base pairs 2 4. Double helix 1 structure (twisted ladder of polynucleotides) 4 3 DNA Nucleotide Structure Single nucleotide subunit Deoxyribose (sugar) molecule binds to phosphate at the Carbon III and V positions MC-2. What is the composition of the backbone of DNA? A. B. C. D. alternating sugar and phosphate molecules complementary base pairs alternating sugar and base molecules a polysaccharide Correct answer: A Structure of Ribose and Glucose Ribose has five carbon molecules Glucose has six carbon molecules Be able to draw these structures! IB Required Monosaccharides IB wants you to be able to list the following monosaccharides Glucose Ribose Fructose Glyceraldehyde Galactose Monosaccharides always have a 1:2:1 carbon: hydrogen: oxygen ratio Example: Glucose is C6H12O6 IB Required Disaccharides IB wants you to be able to list the following disaccharides Sucrose (glucose and fructose) Lactose (glucose and galactose) Maltose (glucose and glucose) table sugar milk sugar starch in seeds IB Required Polysaccharides IB wants you to be able to list the following polysaccharides Cellulose Glycogen Starch cell walls energy storage in animals energy storage in plants Structure of Fatty Acids IB needs you to know this structure: Where n stands for the different number of carbon molecules that can be added or removed to change the length of the chain Structure of Fatty Acids Saturated Fatty Acids Have no double carbon bonds in any of three tails Usually solid at room temperature Example: butter Unsaturated Fatty Acids Have at least one double carbon bond in tails Usually liquid at room temperature Example: cooking oil Which is better for you? Unsaturated fatty acids Phospholipid Structure Molecules in the phospholipid bilayer in cell membrane Lipid Function Energy storage / energy supply Hormone production Cushioning / protection Insulation Constituent of cell membrane (part of phospholipid bilayer) Energy Storage Carbohydrates – – – Stored as glycogen in animals (in liver) Stored as starch in plants (in roots) More easily digested than lipids so energy can be released more quickly Lipids – – – Stored as fat in animals Long-term energy storage More energy per gram than carbohydrates Health Risks of Lipids Saturated fatty acids cause high cholesterol Athersclerosis / narrowing of (lumen of) arteries Hypertension / high blood pressure Obesity / overweight Amino Acid Structure Twenty different amino acids All share the same base: What differs in each amino acid is “R” or the side chain Protein Structure Primary Structure The unique sequence of amino acids, each linked together by a peptide bond Secondary Structure The Beta-pleated sheets and Alpha-helix structures Tertiary Structure in globular proteins involves the folding of polypeptides. This folding pattern is stabilized by several types of bonds including hydrogen bonds and ionic bonds Quaternary Structure of proteins is the linking together of two or more polypeptide subunits. An example of this is hemoglobin which has 4 subunits Example: Hemoglobin has four subunits Protein Function A protein’s shape is the key to its function Know at least four functions and an example Hormones: Insulin helps regulate blood sugar Enzymes: Catalase catalyzes breakdown of hydrogen peroxide waste in blood Transport Proteins: Ion channels and proton pumps for active transport in cell membrane Structural Proteins: Collagen, keratin, tubulin, fibroin Defense: Antibodies are proteins Receptors: Hormone receptor or neurotransmitter receptor on cell surface MC-3. Which is not a primary function of protein molecules? A. B. C. D. hormones energy storage transport structure Correct answer: B MC- 4. Which of the following are connected by a hydrogen bond? A. B. C. D. the hydrogen and oxygen atoms of a water molecule base pairs of a DNA molecule two amino acid molecules of a dipeptide two glucose molecules in a disaccharide Answer: B IB Exam Question 1. Draw a diagram of the molecular structure of a portion of DNA. (4 marks) sugar-phosphate backbone; bases toward centre; A—T, G—C base pair; hydrogen bonds labelled; twisted ladder; two polynucleotides (two strands shown); IB Exam Question 2. To which parts of the deoxyribose molecule do phosphates bind in DNA? (1 mark) A. B. C. D. I and V III and V II and III III and IV Correct answer: B IB Exam Question 3. Which molecules represents ribose? (1 mark) Correct answer: D IB Exam Question 4. Outline how monosaccharides are converted into polysaccharides. (2 marks) condensation; involves the removal of water to join monosaccharides together catalysed by enzymes; consists of many monosaccharides linked (glycosidic) to make polysaccharide; IB Exam Question 5. Describe the use of carbohydrates and lipids for energy storage in animals. (5 marks) Answers must discuss both carbohydrates and lipids to receive full marks. carbohydrates: stored as glycogen (in liver); short-term energy storage; more easily digested than lipids so energy can be released more quickly; more soluble in water for easier transport; lipids: stored as fat in animals; long-term energy storage; more energy per gram than carbohydrates; lipids are insoluble in water less osmotic effect IB Exam Question 6. Draw the structure of a fatty acid. (1 mark) OR IB Exam Question 7. Correct answer: D IB Exam Question 8. Outline the production of a dipeptide by a condensation reaction. Include the structure of a generalized dipeptide in your answer. (5 marks) carboxyl / COOH group of one amino acid reacts with amine / NH2 group of another; water / H2O is eliminated; These steps can be shown diagrammatically, e.g. peptide / covalent bond is produced; diagram of dipeptide, with peptide bond shown; e.g. Award  if the two amino acids forming the dipeptide are shown correctly. The radicals can be shown as R or H. Award the second mark if the C-N bond is labeled as peptide bond or dipeptide bond. The label can include the H bonded to the N and the O double bonded to the C. IB Exam Question 9. List four functions of proteins, giving an example of each. (4 marks) Name of function and named protein must both be correct for the mark. storage – zeatin (in corn seeds) / casein (in milk); transport – hemoglobin / lipoproteins (in blood); hormones – insulin / growth hormone / TSH / FSH / LH; receptors – hormone receptor / neurotransmitter receptor / receptor in chemoreceptor cell; movement – actin / myosin; defence – antibodies / immunoglobin; enzymes – catalase / RuBP carboxylase; structure – collagen / keratin / tubulin / fibroin; electron carriers – cytochromes; pigments – opsin active transport – sodium pumps / calcium pumps; facilitated diffusion – sodium channels / aquaporins; IB Exam Question 10. Explain the significance of polar and non-polar amino acids. (5 marks) • Non-polar amino acids have non-polar (neutrally charged) R groups. \ • Polar amino acids have R chains with polar groups (charged either positive or negative). • Proteins with a lot of polar amino acids make the proteins hydrophyllic and therefore able to dissolve in water. • Proteins with many non-polar amino acids are more hydrophobic and are less soluble in water. • With these abilities, proteins fold themselves so that the hydrophilic ones are on the inner side and allows hydrophilic molecules and ions to pass in and out of the cells through the channels they form. • These channels are vital passages for many substances in and out of the cell. IB Exam Question 11. Outline the difference between fibrous and globular proteins, with reference to examples of each protein type. (4 marks) • Fibrous proteins are in their secondary structure, which could be in the alpha helix or beta pleated forms. • They are made of a repeated sequence of amino acids that can be coiled tightly around in a pattern that makes it a very strong structure. • Two examples are keratin (in hair and skin) and collagen (in tendons, cartilage, and bones). • Globular proteins are in their tertiary or quaternary structure, which is folded, creating a globular, three-dimensional shape. • An example of globular proteins are all enzymes IB Exam Question 12. State one function of glucose and glycogen in animals, and cellulose and starch in plants. ( 4 marks) • Glucose: Energy for Cellular respiration • Glycogen: Energy from this polysaccharides is stored in the liver of animals • Cellulose: Provides strength to cell walls • Starch: Energy from this polysaccharide is stored in roots of plants IB Exam Question 13. List several examples each of monosaccharides, disaccharides and polysaccharides ( 6 marks) • Monosaccharides: Glucose, Fructose (fruit sugar) , Lactose (milk sugar), Ribose (in RNA) • Dissacharides: Sucrose (Glucose and Fructose), Maltose (Glucose and Glucose) • Polysacchrides: Starch (plants) , Glycogen (animals), and Cellulose (plants) Chapter Five Quiz Excellent multiple choice quiz on Campbell Biology textbook CD or website Go to Chapter 5: The Structure and Function of Macromolecules -> Activities Quiz Use this to study!