Biological Molecules

• What are the four main carbon-based molecules common to all life?

Carbohydrates, lipids, proteins, and nucleic acids

• Which two types of biological molecules act as the main stores of energy

Carbohydrates and lipids

• What are the units of a polymer called?

Monomers

• What is the name of the reaction that builds polymers?

Condensation reaction

• What is the name of the reaction that breaks down polymers?

Hydrolysis reaction

• What are the Monomers of disaccharide sucrose

Glucose and fructose

• What is an anion? Give an example

A negatively charged ion; such as chloride ions

• Which type of biological molecule forms the major part of plasma membranes?

Phospholipids

• Give three named examples of globular proteins

Insulin, enzyme, and hemoglobin

• How can the presence of reducing sugars be measure quaantitively?

Benedict's reagent test strip and colorimetry

• Which isomer of glucose makes up glycogen?

Alpha-glucose

• What are the three groups of lipds?

• Which bands form between glycerol and fatty acids?

Ester bonds

• What is the test for lipds?

Emulsion Test

• Which molecules are Triglycerides made of?

Glycerol and three fatty acid chains

• Which three elements are common to biological molecules

Carbon, hydrogen, and oxygen

• What makes a lipid unsaturated

One or more carbon–carbon double bonds in its fatty‑acid chain.

• Which chemical is used in the biochemical test for starch

Iodine Solution

• What is the test for proteins

• What is th test for reducing sugars

• What is the test for non-reducing sugars(e.g. sucrose)?

• What is the test for lipids?

• Bonds in primary structure proteins

Peptide bonds (amide bonds)

• Bonds in secondary structure of proteins

Hydrogen bonds between the backbone N–H and C=O groups (forming α‑helices and β‑sheets)

• Bonds in tertiary structure of proteins

Hydrogen bonds, disulfide (covalent) bonds, ionic (salt bridge) interactions, hydrophobic packing.

• Bonds in Quaternary structure of proteins

• Same as tertiary structure

• Separate twisted or folded polypeptides linked together.

• Can have prosthetic groups

• What is a polymer?

A large molecule made from many repeating monomers

• Why are condensation reactions important in biology?

They form covalent bonds between monomers to build macromolecules

• Why is water released during condensation?

Because an –OH and –H are removed to form the bond

• Why is hydrolysis important in digestion?

It breaks polymers into monomers so they can be absorbed

• What type of bond joins monosaccharides together?

Glycosidic bond

• What is the difference between alpha- and beta-glucose?

Position of the –OH group on carbon 1

• Why is starch suitable for energy storage?

It is compact, insoluble, and easily hydrolysed

• Why is cellulose strong?

Beta-glucose chains form hydrogen bonds between parallel chains

• What are the three groups of lipids?

Triglycerides, phospholipids, steroids

• What is the structure of a triglyceride?

One glycerol molecule bonded to three fatty acids

• What is the structure of a phospholipid?

Glycerol, two fatty acids, and a phosphate group

• What makes a phospholipid amphipathic?

It has a hydrophilic head and hydrophobic tails

• Why are phospholipids ideal for membranes?

They form bilayers with hydrophobic cores

• What is cholesterol?

A lipid-based steroid molecule

• What is the role of cholesterol in membranes?

Maintains membrane stability and fluidity

• Why do lipids have high energy content?

They contain many C–H bonds

• Why are triglycerides insoluble in water?

They are non-polar and hydrophobic

• What elements are found in all amino acids?

Carbon, hydrogen, oxygen, nitrogen

• What additional element may be present in some amino acids?

Sulfur

• What is the general structure of an amino acid?

Central carbon with amino group, carboxyl group, hydrogen, and R group

• What determines the properties of an amino acid?

The R (side chain) group

• What type of bond joins amino acids together?

Peptide bond

• What is a dipeptide?

Two amino acids joined by a peptide bond

• What is a polypeptide?

A chain of many amino acids

• What determines the primary structure of a protein?

The sequence of amino acids

• What causes secondary protein structure?

Hydrogen bonding along the polypeptide backbone

• What maintains tertiary protein structure?

Interactions between R groups

• Why are disulfide bonds important?

They provide strong covalent links for stability

• What causes quaternary protein structure?

Association of multiple polypeptide chains

• Why are globular proteins soluble?

Their hydrophilic R groups face outwards

• Why are fibrous proteins insoluble?

Their hydrophobic R groups dominate

• What is the function of haemoglobin?

Transport of oxygen in red blood cells

• Why is haemoglobin described as conjugated?

It contains a prosthetic haem group

• What is the function of enzymes?

Catalyse biochemical reactions

• Why are enzymes specific?

Their active site is complementary to the substrate

• Why are calcium ions important?

Muscle contraction, neurotransmission, blood clotting

• What is the role of hydrogen ions?

Control pH and enzyme activity

• Why are sodium and potassium ions important?

Nerve impulse transmission

• What is the role of phosphate ions?

ATP production and DNA structure

• Why are nitrate ions important in plants?

Amino acid and protein synthesis

• What colour change indicates a positive biuret test?

Blue to lilac

• What colour change indicates reducing sugars with Benedict’s test?

Blue to green/yellow/orange/brick-red

• Why must non-reducing sugars be hydrolysed first?

They lack a free aldehyde or ketone group

• What colour change indicates starch with iodine?

Brown to blue-black

• What result indicates lipids in the emulsion test?

White cloudy emulsion

• Why is colorimetry used?

To measure concentration using light absorption

• What is absorbance proportional to?

Concentration of the solution

• What is chromatography used for?

Separating and identifying biological molecules

• What is the stationary phase in paper chromatography?

The paper

• What is the mobile phase in chromatography?

The solvent

• What does Rf value represent?

How far a substance travels relative to the solvent

• Why do different molecules have different Rf values?

Different solubilities and affinities for the paper

-