Chapter 2: Biological Molecules Flashcards
Test For Starch
Iodine Solution, Turns from Brown -> Blue/ Black.
Test For Proteins
Biuret Reagent, Turns from Blue -> Purple if protein is present.
Test For Reducing Sugars
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).
Test For Lipids
Ethanol Emulsion Test, Add ethanol to sample and mix it up. If cloudy white emulsion forms, lipids are present.
Test For Non Reducing Sugars
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.
α-glucose and β-glucose
Structural Isomers
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.
Monomer
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.
Polymer
A polymer is a large molecule composed of many repeated subunits (monomers) linked together through covalent bonds.
Macromolecule
A macromolecule is a very large molecule, typically composed of thousands of atoms, formed by the polymerization of smaller units (monomers)
Monosaccharide
A monosaccharide is the simplest form of carbohydrate and consists of a single sugar unit. It cannot be hydrolyzed into simpler sugars.
Disaccharide
A disaccharide is a carbohydrate composed of two monosaccharide units joined together by a glycosidic bond
Polysaccharide
A polysaccharide is a carbohydrate made up of many monosaccharide units linked together, forming long chains.
Condensation Polymerisation
A chemical reaction where two or more monomers combine to form a larger polymer, releasing a small molecule (often water) as a byproduct.
Hydrolysis
A chemical reaction where water is used to break down a compound into smaller units, reversing condensation polymerization.
Reducing Sugar Examples
Glucose, Fructose, & Maltose
Non Reducing Sugar Example
Sucrose
Glycosidic Bond
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 -)
Molecular Structure of Starch
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.
Function of Starch
Serves as the primary energy storage polysaccharide in plants, allowing for compact storage and easy breakdown of glucose when energy is needed.
Molecular Structure of Glycogen
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.
Function of Glycogen
Found in Liver : Primary energy storage polysaccharide in animals, allowing for rapid mobilization of glucose for quick energy needs, such as during exercise.
Molecular Structure of Cellulose
A linear polymer of β-glucose linked by β-1,4-glycosidic bonds, forming strong hydrogen bonds with adjacent chains to create microfibrils.
Function of Cellulose
Provides structural support to plant cell walls, maintaining cell shape and integrity, and contributing to the strength of plant tissues.
Triglycerides
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.
Saturated & Unsaturated
Fatty acids can be saturated (single bonds between carbon atoms) or unsaturated (one or more double bonds).
Molecular Structure of Phospholipids
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).
Functions of Triglycerides
Serve as a major energy storage form, provide insulation, protect vital organs, and are important for cell membrane structure.
Function of Phospholipids
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.
General Structure of an Amino Acid
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).
Peptide Bond
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).
Primary Structure of Proteins
The sequence of amino acids in a polypeptide chain, linked by peptide bonds. Linear & 2D
Secondary Structure of Proteins
The folding or coiling of the polypeptide chain into alpha-helixes or beta-pleated sheets due to hydrogen bonding between amino acids.
Tertiary Structure of Proteins
The overall three-dimensional shape of a protein, formed by interactions between R groups, including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bonds.
Quaternary Structure of Proteins
The assembly of multiple polypeptide chains into a single functional protein complex.
Bonding Types & Ranked from Weakest to Strongest
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.
Globular vs. Fibrous Proteins
Globular proteins are soluble and serve physiological roles, while fibrous proteins are generally insoluble and provide structural support.
Structure & Function of Hemoglobin
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.
Structure & Function of Collagen
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.
Hydrogen Bonding in Water
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.
Polarity of Water Molecules
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
Solvent Action of Water
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.
High Specific Heat Capacity
Water has a high specific heat capacity, meaning it can absorb a large amount of heat before its temperature rises significantly.
Latent Heat of Vaporisation
Water requires a significant amount of energy to change from liquid to vapor (latent heat of vaporization).
