Biological Molecules Flashcards
What are the key molecules required for life?
Carbohydrates, Proteins, Lipids, Nucleic Acids, and Water.
Define monomers and polymers.
Monomers: Smaller units that join together to form larger molecules.
Polymers: Large molecules made of repeating monomer units.
What makes carbon essential to biological molecules?
Carbon can form four covalent bonds, making stable structures.
It bonds with elements like hydrogen, oxygen, nitrogen, and sulfur to form diverse molecules.
Carbon chains can be straight, branched, or cyclic, enabling structural variety.
What are carbohydrates?
Organic compounds containing carbon (C), hydrogen (H), and oxygen (O) in a Cx(H2O)y ratio.
Name the three types of carbohydrates and describe their roles.
Monosaccharides: Single sugar units (e.g., glucose).
Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides, used for storage or structure (e.g., starch, glycogen, cellulose).
What are monosaccharides, and how are they classified?
Single sugar units classified based on the number of carbon atoms:
- Glucose
- Galactose
- Fructose
Explain the two isomers of glucose.
Alpha (𝛼)
α) glucose: The -OH group on carbon 1 is below the plane of the ring.
Beta (𝛽)
β) glucose: The -OH group on carbon 1 is above the plane of the ring.
How are reducing and non-reducing sugars different?
Reducing sugars: Can donate electrons, reducing copper sulphate to form a brick-red precipitate in Benedict’s test (e.g., glucose, galactose).
Non-reducing sugars: Cannot donate electrons; must be hydrolysed to monosaccharides before testing (e.g., sucrose).
How are disaccharides formed, and what bond is involved?
Formed by condensation reactions between two monosaccharides, creating a glycosidic bond and releasing a water molecule.
Give examples of disaccharides and their monomers.
Maltose: Two
α-glucose molecules.
Sucrose:
α-glucose + fructose.
Lactose:
α-glucose + galactose.
How can you calculate the formula of a disaccharide?
Add the monomers’ formulas and subtract one water molecule (H20)
What are polysaccharides, and how are they classified?
Polymers of monosaccharides joined by glycosidic bonds:
Storage polysaccharides: E.g., Starch (plants), Glycogen (animals).
Structural polysaccharides: E.g., Cellulose (plant cell walls).
What are the components of starch?
Amylose: Unbranched, helical chain with
1,4 glycosidic bonds.
Amylopectin: Branched chain with 1,4 and
1,6 glycosidic bonds, allowing rapid energy release.
Why is starch an effective storage molecule?
Compact structure for storage.
Insoluble, preventing osmotic effects in cells.
What makes glycogen suitable for energy storage?
Highly branched structure allows rapid hydrolysis for glucose release, essential for animals’ high energy demands.
What gives cellulose its strength?
Long chains of
β-glucose with 180° rotation between molecules.
Extensive hydrogen bonding between chains, forming microfibrils.
What happens in condensation and hydrolysis reactions?
Condensation: Forms glycosidic bonds, removing water.
Hydrolysis: Breaks glycosidic bonds by adding water.
Give examples of biological processes involving these reactions.
Condensation: Formation of starch and glycogen.
Hydrolysis: Digestion of carbohydrates into monosaccharides.
How do you test for reducing sugars?
Add Benedict’s reagent and heat. A colour change from blue to brick-red indicates the presence of reducing sugars.
How do you test for non-reducing sugars?
Hydrolyse with dilute hydrochloric acid.
Neutralize with sodium hydrogen carbonate.
Perform Benedict’s test.
How is starch detected?
Add iodine in potassium iodide solution. A blue-black colour indicates starch.
What is chromatography used for in biology?
To separate mixtures (e.g., monosaccharides) based on their solubility in a mobile phase.
How is paper chromatography performed?
Place the sample on chromatography paper.
Suspend it in a solvent.
Analyse the distances travelled by components.
How can Benedict’s solution estimate glucose concentration?
Prepare standard glucose solutions using serial dilutions.
Compare the color change of unknown samples to these standards.
Use a colorimeter for precise absorbance measurements.
What are lipids, and what elements do they contain?
Lipids are macromolecules containing carbon, hydrogen, and oxygen, with a lower proportion of oxygen than carbohydrates. They are non-polar and hydrophobic (insoluble in water).
What are the two main types of lipids?
Triglycerides and Phospholipids.
What are the monomers of triglycerides?
Glycerol (an alcohol with hydroxyl groups) and fatty acids.
Describe the structure of fatty acids.
Contains a methyl group (-CH₃) at one end and a carboxyl group (-COOH) at the other.
The hydrocarbon chain (R group) is 4-24 carbons long.
Fatty acids are either saturated or unsaturated.
What is the difference between saturated and unsaturated fatty acids?
Saturated: No double bonds, straight chains, solid at room temperature (e.g., animal fats).
Unsaturated: One or more double bonds causing kinks, liquid at room temperature (e.g., vegetable oils).
