Biological Molecules | Edexcel A-Level Biology B (9BI0)

Biological Molecules

256 questions
19 subtopics
Topics 1 to 4, examined on all three papers
Paper 1, Paper 2 and Paper 3

The first topic and the chemical foundation of the rest of the course: carbohydrates, lipids and proteins, the structure of DNA and RNA and how a gene becomes a protein, how enzymes work and what alters their rate, and the roles of inorganic ions and water..

It covers monosaccharides, disaccharides and polysaccharides, glycosidic bonds and condensation reactions, starch, glycogen and cellulose structure, triglycerides and phospholipids, saturated and unsaturated fats and lipid properties, amino acid structure and the peptide bond, primary, secondary, tertiary and quaternary structure, fibrous and globular proteins, the structure of DNA, dNA replication and gene mutations, the structure of RNA, transcription and translation, enzymes as globular proteins, factors affecting enzyme activity, measuring the rate of enzyme activity, units, uncertainty and experimental error, enzyme inhibition, inorganic ions and the properties of water.

Sample questions from Biological Molecules

Answer each one closed book first, then open the answer.

Monosaccharides, disaccharides and polysaccharides

How does the position of the hydroxyl group on carbon-1 in beta glucose differ from alpha glucose?

Show the answer
In beta glucose, the hydroxyl group on carbon-1 is positioned above the plane of the ring.
Starch, glycogen and cellulose structure

How does the helical structure of amylose contribute to its storage function?

Show the answer
The helical structure makes amylose compact, allowing efficient storage.
Saturated and unsaturated fats and lipid properties

Why are saturated lipids typically solid at room temperature?

Show the answer
Their straight fatty acid chains pack closely together, increasing intermolecular forces.
Primary, secondary, tertiary and quaternary structure

How do ionic bonds form in proteins and what is their role?

Show the answer
Ionic bonds form between oppositely charged R groups (e.g., between positively and negatively charged side chains) and help stabilise protein structure.
The structure of DNA

How many hydrogen bonds link guanine to cytosine in DNA?

Show the answer
Three hydrogen bonds.
The structure of RNA

Which nitrogenous bases can be found in mRNA nucleotides?

Show the answer
Adenine, guanine, cytosine, or uracil.
Enzymes as globular proteins

After the enzyme-substrate complex forms, what happens during catalysis according to the induced fit model?

Show the answer
Catalysis occurs, converting the substrate into product(s).
Measuring the rate of enzyme activity

How is pH controlled in enzyme investigations?

Show the answer
By using a buffer solution.

The 19 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Monosaccharides, disaccharides and polysaccharides	Recall questions on monosaccharides, glucose as a hexose and ribose as a pentose, alpha and beta glucose, hydrolysis of glycosidic bonds, the structure of amylose, and why glucose and branched amylopectin suit rapid energy release.	9
Glycosidic bonds and condensation reactions	Recall questions on disaccharides and polysaccharides, condensation and the glycosidic bond, the monosaccharides in sucrose, lactose and maltose, the amylose and amylopectin in starch, 1,4 and 1,6 links, and glycogen branching.	9
Starch, glycogen and cellulose structure	Recall questions on amylose and amylopectin, the branching of glycogen, and how the beta linkage in cellulose produces its strength.	8
Triglycerides and phospholipids	Recall questions on glycerol, fatty acids and the ester bond formed by condensation in a triglyceride, the phosphate group of a phospholipid, its hydrophilic head and hydrophobic tails, how phospholipids form a bilayer, and what bilayer fluidity allows.	20
Saturated and unsaturated fats and lipid properties	Recall questions on saturated and unsaturated fatty acids, how double bonds and kinks affect packing and whether a lipid is solid or liquid, why lipids release more energy per gram, and their insolubility, waterproofing and insulation.	10
Amino acid structure and the peptide bond	Recall questions on the general structure of an amino acid, the R group, and how a peptide bond forms.	9
Primary, secondary, tertiary and quaternary structure	Recall questions on primary structure and why it determines folding, the alpha helix and beta pleated sheet, the ionic, disulfide and hydrogen bonds that stabilise tertiary structure, and what holds quaternary structure together.	10
Fibrous and globular proteins	Recall questions on fibrous and globular proteins, collagen's glycine-rich triple helix, its hydrogen bonds, cross-links and tensile strength, and haemoglobin's alpha and beta chains, haem groups, solubility and cooperative binding.	15
The structure of DNA	Recall questions on the nucleotide, complementary base pairing, the antiparallel double helix, and the bonds that hold it.	12
DNA replication and gene mutations	Recall questions on helicase, DNA ligase and DNA polymerase in semi-conservative replication, then gene mutations: deletions, insertions, substitutions and frameshifts, and the base change behind sickle cell anaemia and its effect on red blood cells.	13
The structure of RNA	Recall questions on the phosphodiester bond, the ribose, phosphate and bases of an mRNA nucleotide, the single-stranded structure of mRNA, the cloverleaf shape of tRNA, anticodons, and how a tRNA carries its amino acid.	9
Transcription and translation	Recall questions on the gene as a sequence coding for a polypeptide, non-coding DNA, transcription of the antisense strand by RNA polymerase in the nucleus, translation at the ribosome, and the triplet, degenerate and non-overlapping genetic code with its start and stop codons.	15
Enzymes as globular proteins	Recall questions on enzymes as globular proteins and biological catalysts, the induced fit model and the enzyme-substrate complex, activation energy, the active site and specificity, and intracellular and extracellular enzymes.	13
Factors affecting enzyme activity	Recall questions on how temperature and pH affect rate and cause denaturation, the effect of substrate and enzyme concentration, Vmax, why initial rate matters, and using proportionality, y = mx + c and gradients to predict rates.	14
Measuring the rate of enzyme activity	Recall questions on measuring product formed or substrate used, drawing a tangent to find initial rate, and controlling the variables.	18
Units, uncertainty and experimental error	Recall questions on converting between nanometres, micrometres and millimetres, uncertainty and resolution, calculating and combining percentage error in enzyme experiments, accuracy and precision, random and systematic errors, and using uncertainty to evaluate conclusions.	17
Enzyme inhibition	Recall questions on competitive and non-competitive inhibitors, where each binds, why only competitive inhibition is overcome by adding more substrate, and end-product inhibition as negative feedback.	10
Inorganic ions	Recall questions on why plants need nitrate ions for DNA and amino acids, calcium ions for calcium pectate in the middle lamella, magnesium ions for chlorophyll and phosphate ions for ADP and ATP, and the deficiency symptoms of each.	19
The properties of water	Recall questions on the polarity of water and hydrogen bonding, its high specific heat capacity, its solvent properties, surface tension, incompressibility and hydrostatic support, maximum density at 4 °C, and why floating ice protects aquatic life.	26

Biological Molecules is 256 of the 2,073 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.