Chapter 2: Biological Molecules

Question 1

Test For Starch

Answer 1

Iodine Solution, Turns from Brown -> Blue/ Black.

Question 2

Test For Proteins

Answer 2

Biuret Reagent, Turns from Blue -> Purple if protein is present.

Question 3

Test For Reducing Sugars

Answer 3

Add Benedicts Reagent to sample, heat it up, if colour change from blue to brick red, reducing sugar is present. Colour may vary from red (highest conc) to orange to yellow to green to blue (lowest conc).

Question 4

Test For Lipids

Answer 4

Ethanol Emulsion Test, Add ethanol to sample and mix it up. If cloudy white emulsion forms, lipids are present.

Question 5

Test For Non Reducing Sugars

Answer 5

Add Dilute HCl to sample to hydrolyze the non reducing sugar, then heat up and then add Na2CO3 to neutralize. Add Benedicts Reagent, Heat up and observe colour change.

Question 6

α-glucose and β-glucose
Structural Isomers

Answer 6

The difference is the position of the hydroxyl group at the first carbon atom. In α-glucose the OH is below the ring, in β-glucose, the OH is above the ring.

Question 7

Monomer

Answer 7

A monomer is a small, single unit or molecule that can join together with other similar or different molecules to form a larger structure, called a polymer.

Question 8

Polymer

Answer 8

A polymer is a large molecule composed of many repeated subunits (monomers) linked together through covalent bonds.

Question 9

Macromolecule

Answer 9

A macromolecule is a very large molecule, typically composed of thousands of atoms, formed by the polymerization of smaller units (monomers)

Question 10

Monosaccharide

Answer 10

A monosaccharide is the simplest form of carbohydrate and consists of a single sugar unit. It cannot be hydrolyzed into simpler sugars.

Question 11

Disaccharide

Answer 11

A disaccharide is a carbohydrate composed of two monosaccharide units joined together by a glycosidic bond

Question 12

Polysaccharide

Answer 12

A polysaccharide is a carbohydrate made up of many monosaccharide units linked together, forming long chains.

Question 13

Condensation Polymerisation

Answer 13

A chemical reaction where two or more monomers combine to form a larger polymer, releasing a small molecule (often water) as a byproduct.

Question 14

Hydrolysis

Answer 14

A chemical reaction where water is used to break down a compound into smaller units, reversing condensation polymerization.

Question 15

Reducing Sugar Examples

Answer 15

Glucose, Fructose, & Maltose

Question 16

Reducing Sugar Example

Answer 16

Sucrose

Question 17

Glycosidic Bond

Answer 17

A covalent bond formed between two monosaccharides through a condensation reaction, resulting in the release of water.

Example :
Sucrose (glucose + fructose) has an α-1,2-glycosidic bond.
Maltose (glucose + glucose) has an α-1,4-glycosidic bond.

Structure : (- O -)

Question 18

Molecular Structure of Starch

Answer 18

Starch consists of two components: Amylose, a linear polymer of α-glucose with α-1,4-glycosidic bonds, and Amylopectin, a branched polymer with both α-1,4 and α-1,6-glycosidic bonds.

Question 19

Function of Starch

Answer 19

Serves as the primary energy storage polysaccharide in plants, allowing for compact storage and easy breakdown of glucose when energy is needed.

Question 20

Molecular Structure of Glycogen

Answer 20

A highly branched polymer similar to amylopectin, consisting of α-glucose units linked by α-1,4 and α-1,6-glycosidic bonds, with branches occurring every 8-12 glucose units.

Question 21

Function of Glycogen

Answer 21

Found in Liver : Primary energy storage polysaccharide in animals, allowing for rapid mobilization of glucose for quick energy needs, such as during exercise.

Question 22

Molecular Structure of Cellulose

Answer 22

A linear polymer of β-glucose linked by β-1,4-glycosidic bonds, forming strong hydrogen bonds with adjacent chains to create microfibrils.

Question 23

Function of Cellulose

Answer 23

Provides structural support to plant cell walls, maintaining cell shape and integrity, and contributing to the strength of plant tissues.

Question 24

Triglycerides

Answer 24

Non-polar and hydrophobic molecules. Composed of one glycerol molecule and three fatty acids. Formed through a condensation reaction where each fatty acid forms an ester bond with the glycerol.

Question 25

Saturated & Unsaturated

Answer 25

Fatty acids can be saturated (single bonds between carbon atoms) or unsaturated (one or more double bonds).

Question 26

Molecular Structure of Phospholipids

Answer 26

Composed of one glycerol, two fatty acid tails, and a phosphate head. The phosphate head is hydrophilic (polar), while the fatty acid tails are hydrophobic (non-polar).

Question 26

Functions of Triglycerides

Answer 26

Serve as a major energy storage form, provide insulation, protect vital organs, and are important for cell membrane structure.

Question 27

Function of Phospholipids

Answer 27

Form the bilayer structure of cell membranes, creating a barrier that separates the interior of the cell from the external environment, allowing for selective permeability.

Question 28

General Structure of an Amino Acid

Answer 28

An amino acid consists of a central carbon atom (C) bonded to an amino group (–NH₂), a carboxyl group (–COOH), a hydrogen atom (–H), and a variable R group (side chain).

Question 29

Peptide Bond

Answer 29

A peptide bond forms between the amino group of one amino acid and the carboxyl group of another, releasing a molecule of water (condensation reaction).

Question 30

Primary Structure of Proteins

Answer 30

The sequence of amino acids in a polypeptide chain, linked by peptide bonds. Linear & 2D

Question 31

Secondary Structure of Proteins

Answer 31

The folding or coiling of the polypeptide chain into alpha-helixes or beta-pleated sheets due to hydrogen bonding between amino acids.

Question 32

Tertiary Structure of Proteins

Answer 32

The overall three-dimensional shape of a protein, formed by interactions between R groups, including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bonds.

Question 33

Quaternary Structure of Proteins

Answer 33

The assembly of multiple polypeptide chains into a single functional protein complex.

Question 34

Bonding Types & Ranked from Weakest to Strongest

Answer 34

Hydrophobic Interactions: Non-polar R groups aggregate to avoid contact with water, stabilizing the protein structure.

Hydrogen Bonding: Weak interactions between hydrogen atoms covalently bonded to electronegative atoms (like O or N) and other electronegative atoms.

Ionic Bonding: Attraction between positively and negatively charged R groups within a protein.

Disulfide Bonding: Strong bonds formed between atoms formed between cysteine residues, stabilizing protein structure.

Question 35

Globular vs. Fibrous Proteins

Answer 35

Globular proteins are soluble and serve physiological roles, while fibrous proteins are generally insoluble and provide structural support.

Question 36

Structure & Function of Hemoglobin

Answer 36

Hemoglobin is a globular protein made of four polypeptide chains: two alpha (α) chains and two beta (β) chains, each containing a haem group.

Hemoglobin’s quaternary structure allows for efficient oxygen transport; iron in the haem group binds oxygen molecules for delivery to tissues.

Question 37

Structure & Function of Collagen

Answer 37

Collagen is a fibrous protein composed of three polypeptide chains that form a triple helix, providing tensile strength and structural support.

Collagen fibers provide strength and support in connective tissues, such as skin, bones, and cartilage, allowing for flexibility and durability.

Question 38

Hydrogen Bonding in Water

Answer 38

Hydrogen bonding occurs when the partially positive hydrogen atoms of one water molecule are attracted to the partially negative oxygen atoms of another water molecule, creating a network of weak bonds.

Question 39

Polarity of Water Molecules

Answer 39

Water is a polar molecule, meaning it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom, leading to hydrogen bonding between molecules

Question 40

Solvent Action of Water

Answer 40

Water’s polarity allows it to dissolve many ionic and polar substances (like salts and sugars), making it an excellent solvent for biochemical reactions in living organisms.

Question 41

High Specific Heat Capacity

Answer 41

Water has a high specific heat capacity, meaning it can absorb a large amount of heat before its temperature rises significantly.

Question 42

Latent Heat of Vaporisation

Answer 42

Water requires a significant amount of energy to change from liquid to vapor (latent heat of vaporization).