OCR A Level Biology: Foundations in Biology — Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Foundations in Biology study guide | Foundations in Biology revision notes

Note: these written questions assess Module 2 content only. Practical competence itself is assessed separately, through the non-exam Practical Endorsement across the twelve Practical Activity Groups (PAGs), which does not contribute marks to the three written papers.

In OCR’s H420 papers, Biological processes (H420/01) and Biological diversity (H420/02), each 100 marks, open with a Section A of multiple-choice questions worth 15 marks, followed by a Section B of short-answer and extended-response questions worth 85 marks; Unified biology (H420/03, 70 marks) has no multiple-choice section. The multiple-choice sample below is scoped to this topic (Foundations in Biology) only, and is not a reproduction of a full paper’s Section A.

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Section A — Multiple choice (topic sample)

1. Which statement correctly defines resolution in microscopy? A) The degree to which an image is enlarged compared with the real object B) The minimum distance between two points at which they can still be distinguished as separate C) The total magnification achieved by combining eyepiece and objective lenses D) The wavelength of the illuminating source [1]

2. Which of the following is a key difference between a transmission electron microscope (TEM) and a scanning electron microscope (SEM)? A) A TEM produces a 3D image of a sample’s surface, while an SEM produces a 2D image of internal structure B) A TEM passes electrons through a thin sample to reveal internal structure, while an SEM scans electrons across a sample’s surface to produce a 3D-like image C) A TEM uses light, while an SEM uses electrons D) A TEM has lower resolution than a light microscope, while an SEM has higher resolution [1]

3. Which type of bond joins two amino acids together in a polypeptide chain? A) Glycosidic bond B) Ester bond C) Peptide bond D) Phosphodiester bond [1]

4. Which organelle contains a single circular strand of DNA and 70S ribosomes, providing evidence for the endosymbiotic theory? A) Nucleus B) Golgi apparatus C) Mitochondria D) Rough endoplasmic reticulum [1]

5. Which property of water is due to hydrogen bonding between water molecules themselves, rather than to water acting as a solvent? A) High specific heat capacity, which allows water to buffer temperature changes B) Ability to dissolve ionic substances such as sodium chloride C) Ability to dissolve polar molecules such as glucose D) Acting as a medium in which metabolic reactions take place [1]

6. Which type of bond joins monosaccharides together to form a disaccharide or polysaccharide? A) Peptide bond B) Ester bond C) Glycosidic bond D) Phosphodiester bond [1]

7. A triglyceride is formed from which combination of molecules, joined by which type of bond? A) One glycerol and three fatty acids, joined by ester bonds B) Three glycerol molecules and one fatty acid, joined by glycosidic bonds C) One glycerol and three fatty acids, joined by peptide bonds D) Two fatty acids and one phosphate group, joined by ester bonds [1]

8. A competitive enzyme inhibitor reduces reaction rate by which mechanism? A) Binding permanently to the active site, destroying the enzyme B) Binding to a site other than the active site, changing the active site’s shape C) Binding reversibly to the active site, blocking the substrate from binding there D) Increasing the activation energy of the reaction without binding the enzyme at all [1]

9. The fluid mosaic model describes the structure of the cell-surface membrane. What are the two main components referred to by “fluid” and “mosaic”? A) A rigid layer of cellulose (fluid) with scattered pores (mosaic) B) A bilayer of phospholipids that can move (fluid) with proteins scattered throughout it (mosaic) C) A single layer of protein (fluid) with fixed channels of lipid (mosaic) D) A layer of water (fluid) surrounding a solid core of protein (mosaic) [1]

10. Which statement correctly defines osmosis? A) The net movement of water molecules from a region of lower water potential to higher water potential across a partially permeable membrane B) The net movement of water molecules from a region of higher water potential to lower water potential across a partially permeable membrane C) The movement of solute particles from a region of high to low concentration, requiring no membrane D) The active movement of water molecules against a concentration gradient, using ATP [1]

11. DNA replication is described as “semi-conservative.” What does this mean? A) Each new DNA molecule is made entirely of new nucleotides B) Each new DNA molecule contains one original (template) strand and one newly synthesised strand C) Only half of the original DNA molecule is replicated at a time D) DNA is replicated only in half of a cell’s chromosomes during each division [1]

12. What happens when a molecule of ATP is hydrolysed to ADP and inorganic phosphate? A) Energy is absorbed, which is stored for later use B) Energy is released, which can be used to drive cellular processes C) A new phosphate bond is formed, using energy from respiration D) ATP is converted directly into a nucleic acid [1]

13. Which colour change indicates a positive biuret test for protein? A) Blue to brick-red precipitate B) Blue to purple/lilac C) Orange to green D) Colourless to blue-black [1]

14. Which term describes a stem cell capable of differentiating into any cell type, including extra-embryonic tissue such as the placenta? A) Pluripotent B) Multipotent C) Totipotent D) Unipotent [1]

15. Which of these is a defining feature of active transport across a cell membrane? A) It requires ATP and moves substances against their concentration gradient using carrier proteins B) It requires no energy input and moves substances down their concentration gradient C) It moves only water molecules, always down a water potential gradient D) It occurs only through protein channels, never through carrier proteins [1]

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Section B — Short answer and extended questions

16. Define magnification and resolution, and explain why an electron microscope reveals detail invisible under a light microscope. [3]

17. State two ways in which a prokaryotic cell differs from a eukaryotic cell. [2]

18. A mitochondrion appears 4.5 cm wide in a photomicrograph taken at a magnification of 15,000×.

(a) Calculate the real width of the mitochondrion, giving your answer in micrometres. [3] (b) State one structural feature of a mitochondrion visible only with electron, not light, microscopy. [1]

19. For each organelle, state its function: (a) rough endoplasmic reticulum (b) Golgi apparatus (c) lysosome. [3]

20. Explain, in terms of hydrogen bonding, why water is an effective solvent for polar and ionic substances. [3]

21. Distinguish between a condensation reaction and a hydrolysis reaction, using the formation and breakdown of a polymer as your example. [4]

22. Describe the sequence of organelles involved in producing and secreting a protein. [3]

23. State the monomer of DNA and RNA, and explain one structural difference between the two nucleic acids. [2]

Answers

1. B) Resolution is the ability to distinguish two close points as separate rather than as one blurred point; option A describes magnification, and neither total magnification nor the illuminating wavelength alone defines resolution [1].

2. B) A TEM passes a beam of electrons through a thin, stained section to reveal internal ultrastructure, while an SEM scans electrons across the surface of a (often whole) specimen to build up a 3D-like surface image; both use electrons, not light, and both have far higher resolution than a light microscope [1].

3. C) A peptide bond joins two amino acids; a glycosidic bond joins monosaccharides, an ester bond joins glycerol and a fatty acid, and a phosphodiester bond joins nucleotides [1].

4. C) Mitochondria contain their own small circular loop of DNA and 70S ribosomes, similar to those of prokaryotes, which is evidence that mitochondria evolved from free-living prokaryotic organisms engulfed by an ancestral cell (the endosymbiotic theory) [1].

5. A) High specific heat capacity arises because hydrogen bonds between water molecules must be broken for temperature to rise, which is a property of water interacting with itself; dissolving ionic and polar substances, and acting as a reaction medium, instead reflect water’s role as a solvent [1].

6. C) A glycosidic bond joins monosaccharides together to form disaccharides and polysaccharides; a peptide bond joins amino acids, an ester bond joins glycerol and fatty acids, and a phosphodiester bond joins nucleotides [1].

7. A) A triglyceride is formed from one glycerol molecule and three fatty acid molecules, joined by ester bonds formed in condensation reactions; glycosidic and peptide bonds join different classes of monomer entirely [1].

8. C) A competitive inhibitor has a shape similar to the substrate and binds reversibly to the active site itself, physically blocking the substrate from binding; a non-competitive inhibitor, not a competitive one, binds elsewhere and changes the active site’s shape [1].

9. B) “Fluid” refers to the phospholipid bilayer, whose molecules can move relative to one another, and “mosaic” refers to the scattered, varied arrangement of proteins embedded within and across it [1].

10. B) Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential, across a partially permeable membrane; option A reverses the direction, and osmosis is passive, not active, and does require a membrane [1].

11. B) Semi-conservative replication means each new DNA molecule is made of one original template strand and one newly synthesised strand, rather than being entirely new or only partially replicated [1].

12. B) Hydrolysing the bond between the second and third phosphate groups of ATP releases energy that can be used to drive cellular processes such as active transport or biosynthesis, forming ADP and inorganic phosphate; forming this bond (the reverse reaction) requires energy input rather than releasing it [1].

13. B) A positive biuret test for protein turns the solution from blue to purple/lilac; blue to brick-red describes a positive Benedict’s test for reducing sugar, and colourless to blue-black describes the iodine test for starch [1].

14. C) A totipotent stem cell can differentiate into any cell type, including extra-embryonic tissue such as the placenta; a pluripotent stem cell can become almost any body cell type but not extra-embryonic tissue, and multipotent and unipotent cells have progressively more restricted potential [1].

15. A) Active transport uses ATP and carrier proteins to move substances against their concentration gradient, distinguishing it from diffusion (passive, down a gradient) and osmosis (passive, water only) [1].

16. Magnification is how much bigger an image appears compared with the real object [1]; resolution is the ability to distinguish two close points as separate rather than as one blurred point [1]. An electron microscope reveals detail invisible under a light microscope because it achieves far higher resolution, not simply because it magnifies more [1].

17. Any two: a prokaryotic cell lacks a membrane-bound nucleus, whereas a eukaryotic cell has one [1]; a prokaryotic cell lacks membrane-bound organelles such as mitochondria, whereas a eukaryotic cell has them [1]; a prokaryotic cell is typically much smaller than a eukaryotic cell [1].

18. (a) Convert image size to consistent units: 4.5 cm = 45,000 μm [1]; rearranging magnification = image size ÷ object size gives object size = image size ÷ magnification [1]; object size = 45,000 ÷ 15,000 = 3 μm [1]. (b) Any one: the internal folded membrane (cristae), or the double membrane structure [1].

19. (a) Rough endoplasmic reticulum — processes and folds proteins synthesised by the ribosomes attached to its surface [1]. (b) Golgi apparatus — modifies, packages and sorts proteins (and lipids) for transport, often into secretory vesicles [1]. (c) Lysosome — contains digestive enzymes that break down waste material, old organelles or invading pathogens [1].

20. Water is a polar molecule, with a slightly negative oxygen end and slightly positive hydrogen ends [1], which allows it to form hydrogen bonds with other polar or charged particles [1]. This lets water molecules surround and separate the ions or polar molecules of a solute, drawing them into solution [1].

21. A condensation reaction joins two monomers together to form a polymer, releasing a molecule of water in the process [2]. A hydrolysis reaction breaks a polymer back down into its constituent monomers, using a molecule of water to do so [2] — the two reactions are the reverse of each other, with water released in one and consumed in the other.

22. Proteins are synthesised by ribosomes attached to the rough endoplasmic reticulum, which processes and folds them [1]; the proteins are then transported, often in vesicles, to the Golgi apparatus, which modifies and packages them [1]; the Golgi apparatus then buds off secretory vesicles that move to and fuse with the plasma membrane, releasing the protein outside the cell [1].

23. The monomer of both DNA and RNA is a nucleotide [1]. One structural difference: DNA is typically double-stranded, while RNA is typically single-stranded [1] (also accept: DNA contains deoxyribose sugar and the base thymine, while RNA contains ribose sugar and the base uracil in place of thymine).

A note on the magnification formula

Question 18 tests the version of the magnification formula that students most often find unfamiliar: rearranging to find object size, rather than calculating magnification itself. The formula magnification = image size ÷ object size can be rearranged for any one of its three variables, and exam questions deliberately vary which one is missing to test genuine algebraic fluency rather than memorised substitution. The step most commonly skipped, and the one most likely to cost marks, is converting the image size and object size to the same unit before dividing — a mismatch of even one order of magnitude (millimetres against micrometres, for instance) produces an answer that is a power of ten out, which is easy to miss if the final figure is not sanity-checked against a realistic cell or organelle size.

Where marks are usually lost

• Describing electron microscopes as revealing more detail because they “magnify more,” rather than because they achieve higher resolution.
• Failing to convert image size and object size to the same unit before applying the magnification formula.
• Naming an organelle without stating its function, when questions consistently ask for both together.
• Confusing the roles of the rough endoplasmic reticulum and the Golgi apparatus in the secretory pathway.
• Listing water’s properties as unconnected facts rather than explicitly linking them back to hydrogen bonding and polarity.

Approaching foundations in biology questions

Before attempting any magnification calculation, identify which of the three quantities — image size, object size, or magnification — is missing, and rearrange the formula for that variable before substituting numbers, converting both given measurements to the same unit as the very first step. For questions on organelles, always pair a named structure with its function in the same sentence, since OCR mark schemes typically award separate marks for each and a correct name alone earns only partial credit. When a question asks about biological molecules, look for an opportunity to trace the answer back to a more fundamental principle — hydrogen bonding for water’s properties, or the condensation/hydrolysis pair for how monomers and polymers interconvert — since this kind of explanatory depth is what distinguishes full-mark answers from ones that only state a fact without justifying it.