Biological molecules

What is the definition of a polymer?

A large molecule made from a large number of monomers joined together.

Name the reaction that joins two molecules together with the formation of a chemical bond and the elimination of a molecule of water.

Condensation reaction.

Which process involves breaking a chemical bond between two molecules using a water molecule?

Hydrolysis.

Identify the specific chemical bond formed between two monosaccharides during a condensation reaction.

Glycosidic bond.

What term describes molecules with the same chemical formula but different structural arrangements, such as $\alpha$-glucose and $\beta$-glucose?

Isomers.

Which two monosaccharides condense to form the disaccharide maltose?

Two glucose molecules.

Which two monosaccharides condense to form the disaccharide sucrose?

Glucose and fructose.

Which two monosaccharides condense to form the disaccharide lactose?

Glucose and galactose.

Describe the orientation of adjacent monomers in a cellulose molecule.

Alternate glucose monomers are rotated (flipped) 180 degrees relative to each other.

How does the structural shape of a cellulose molecule differ from that of starch?

Cellulose forms straight, unbranched chains, whereas starch is coiled or branched.

Identify the two types of polysaccharide molecules that make up starch.

Amylose and amylopectin.

Explain why the highly branched structure of glycogen is beneficial for its function in animals.

It provides a large surface area for rapid hydrolysis to release glucose for respiration.

In the Benedict's test, what causes the formation of a red precipitate in the presence of a reducing sugar?

The reduction of copper(II) ions to copper(I) oxide.

Before testing for non-reducing sugars with Benedict's reagent, what must be added to the sample first?

Dilute hydrochloric acid to hydrolyse the disaccharide into monosaccharides.

What reagent is used to test for the presence of starch, and what is the positive result?

Iodine in potassium iodide solution, which turns from orange-brown to blue-black.

Name the components of a triglyceride molecule.

One molecule of glycerol and three fatty acids.

Identify the bond formed between a glycerol molecule and a fatty acid.

Ester bond.

What is the structural difference between a saturated fatty acid and an unsaturated fatty acid?

Saturated fatty acids have no C=C double bonds, while unsaturated fatty acids have at least one.

How does the structure of a phospholipid differ from a triglyceride?

One fatty acid is replaced by a phosphate-containing group.

Describe the positive result of an emulsion test for lipids.

The formation of a milky-white cloudy layer.

What are the monomers that make up proteins?

Amino acids.

Identify the bond formed between two amino acids in a condensation reaction.

Peptide bond.

Define the primary structure of a protein.

The specific sequence of amino acids in the polypeptide chain.

Which reagent is used to detect proteins, and what colour indicates a positive result?

Biuret reagent, which turns from blue to purple (lilac/mauve).

Explain the role of an enzyme in terms of activation energy.

Enzymes increase the rate of reaction by lowering the activation energy.

Describe the induced-fit model of enzyme action.

The active site changes shape slightly as the substrate binds to form a complementary fit.

How does the tertiary structure of an enzyme's active site determine its specificity?

The active site has a specific shape that is complementary only to one specific substrate.

How does a non-competitive inhibitor reduce the rate of an enzyme-controlled reaction?

It binds to an allosteric site, changing the shape of the active site so the substrate can no longer bind.

List the three components of a DNA nucleotide.

Deoxyribose, a phosphate group, and a nitrogen-containing organic base.

Identify the four organic bases found in DNA.

Adenine, Cytosine, Guanine, and Thymine.

Which nitrogenous base is found in RNA but not in DNA?

Uracil.

Identify the bond formed between two nucleotides in a condensation reaction.

Phosphodiester bond.

What is the function of DNA helicase during semi-conservative replication?

It breaks the hydrogen bonds between complementary base pairs to unwind the double helix.

State the role of DNA polymerase in DNA replication.

It joins adjacent nucleotides together by forming phosphodiester bonds in a condensation reaction.

Describe the components of an ATP molecule.

Ribose, adenine, and three phosphate groups.

Which enzyme catalyses the hydrolysis of ATP to ADP and P_i?

ATP hydrolase.

Why is the high latent heat of vaporisation of water significant for living organisms?

It provides a cooling effect through evaporation with little loss of water.

What does the term 'semi-conservative' mean in the context of DNA replication?

Each new DNA molecule contains one original (template) strand and one newly synthesised strand.

In a plant's mass flow system, what causes the lowering of water potential in the phloem?

The active transport of sucrose into the sieve tube elements.

Explain why amylase cannot digest galacto-oligosaccharides (GOS).

The tertiary structure of the amylase active site is not complementary to GOS.

What biological process do bacteria use galactose for to increase their population size?

Binary fission.

Name the enzyme that hydrolyses maltose into glucose.

Maltase.

Identify the property of starch that makes it an excellent storage molecule because it does not affect water potential.

It is insoluble.

What term describes the attraction between water molecules due to hydrogen bonding?

Cohesion.

How does the presence of double bonds in a fatty acid affect its melting point?

Increasing the number of double bonds decreases the melting point.

Name the specific cells that assist in the transport of sucrose into phloem sieve tubes.

Companion cells (or transfer cells).

What is the effect of an increased concentration of solutes on the water potential of a solution?

It lowers the water potential (makes it more negative).

In DNA replication, to which end of the new DNA strand does DNA polymerase add nucleotides?

The $3'$ end.

Identify the structural feature of cellulose that provides high tensile strength to plant cell walls.

The formation of microfibrils through hydrogen bonding between parallel chains.

Define quaternary structure in proteins.

The arrangement and interaction of multiple polypeptide chains in a single protein.

Which enzyme is required to synthesise ATP from ADP and inorganic phosphate?

ATP synthase.

Explain why water is described as a metabolite.

It is directly involved in chemical reactions, such as hydrolysis and condensation.

What is the function of lignin in xylem vessels?

It strengthens the walls and keeps the vessels open as continuous tubes for water transport.

In colorimetry, what is the relationship between reducing sugar concentration and light transmission?

Higher sugar concentration results in lower light transmission (higher absorbance).

What is the primary role of DNA polymerase in semi-conservative replication?

Joining free nucleotides together via phosphodiester bonds.

Identify the pentose sugar found in RNA nucleotides.

Ribose.

How many ester bonds are found in a single phospholipid molecule?

Two.