IB Biology Review

Topic 3: Chemistry of Life

Vocabulary

Macromoleculeterm used to describe large molecules such as carbohydrates, lipids, proteins, and nucleic acids

Monomerthe repeating unit molecules of polymers

Polymera long chainlike molecule consisting of repeating building-block molecules linked by covalent bondsincludes proteins, carbohydrates, and nucleic acids

What are the four groups of macromolecules?

Carbohydrates

Lipids

Proteins

Nucleic Acids

Examples of Monomers

What are the monomers ofCarbohydrates

Simple sugars (monosaccharides) like glucose and fructose make polysaccharides

Proteins20 different amino acids form polypeptides

Nucleic AcidsNucleotides (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 bondAnabolic 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. hydrolysisB. denaturationC. condensationD. 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 molecules2. Bases are towards center (A/T) (G/C)3. Hydrogen bond connects adjacent base pairs4. Double helix structure (twisted ladder of polynucleotides)

12

3

4

DNA Nucleotide Structure

Deoxyribose (sugar) molecule binds to phosphate at the Carbon III and V positions

Single nucleotide subunit

MC-2. What is the composition of the backbone of DNA?

A. alternating sugar and phosphate molecules

B. complementary base pairsC. alternating sugar and base

moleculesD. a polysaccharide

Correct answer: A

Structure of Ribose and Glucose

Ribose has five carbon moleculesGlucose has six carbon molecules

Be able to draw these structures!

IB Required Monosaccharides

IB wants you to be able to list the following monosaccharides

GlucoseRiboseFructoseGlyceraldehydeGalactose

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) table sugarLactose (glucose and galactose) milk sugarMaltose (glucose and glucose) starch in seeds

IB Required Polysaccharides

IB wants you to be able to list the following polysaccharides

Cellulose cell wallsGlycogen energy storage in animalsStarch 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 AcidsHave no double carbon bonds in any of three tailsUsually solid at room temperature Example: butter

Unsaturated Fatty AcidsHave at least one double carbon bond in tailsUsually liquid at room temperatureExample: 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 supplyHormone productionCushioning / protectionInsulationConstituent 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 cholesterolAthersclerosis / narrowing of (lumen of) arteriesHypertension / high blood pressureObesity / overweight

Amino Acid Structure

Twenty different amino acidsAll share the same base:

What differs in each amino acid is “R” or the side chain

Protein StructurePrimary Structure

The unique sequence of amino acids, each linked together by a peptide bond

Secondary StructureThe Beta-pleated sheets and Alpha-helix structures

Tertiary Structurein globular proteins involves the folding of polypeptides. This folding pattern is stabilized by several types of bonds including hydrogen bonds and ionic bonds

Quaternary Structureof proteins is the linking together of two or more polypeptide subunits. An example of this is hemoglobin which has 4 subunitsExample: Hemoglobin has four subunits

Protein Function

A protein’s shape is the key to its functionKnow at least four functions and an example

Hormones: Insulin helps regulate blood sugarEnzymes: Catalase catalyzes breakdown of hydrogen peroxide waste in bloodTransport Proteins: Ion channels and proton pumps for active transport in cell membraneStructural Proteins: Collagen, keratin, tubulin, fibroinDefense: Antibodies are proteinsReceptors: Hormone receptor or neurotransmitter receptor on cell surface

MC-3. Which is not a primary function of protein molecules?

A. hormonesB. energy storageC. transportD. structure

Correct answer: B

MC- 4. Which of the following are connected by a hydrogen

bond?

A. the hydrogen and oxygen atoms of a water molecule

B. base pairs of a DNA moleculeC. two amino acid molecules of a

dipeptideD. two glucose molecules in a

disaccharide

Answer: B

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. I and VB. III and VC. II and IIID. 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)

IB Exam Question

OR

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 [1] 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 – opsinactive 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)

IB Exam Question

Chapter Five Quiz

Excellent multiple choice quiz on Campbell Biology textbook CD or websiteGo to Chapter 5: The Structure and Function of Macromolecules -> Activities Quiz

Use this to study!