UVAS DVM Admission Test Biology Flashcards

24 sample cards from the Biology deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. How many amino acids commonly occur in proteins and how are they classified?

   There are 20 standard amino acids. They are classified as essential (must be obtained from diet) and non-essential (synthesized by the body).

2. What is the general structure of an amino acid?

   A central (alpha) carbon bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable R-group (side chain).

3. What is a peptide bond and how is it formed?

   A covalent bond between the carboxyl group of one amino acid and the amino group of another, formed by a condensation reaction releasing water.

4. Name the four levels of protein structure.

   Primary (amino acid sequence), secondary (alpha-helix and beta-pleated sheet from hydrogen bonding), tertiary (overall 3D folding), and quaternary (assembly of multiple polypeptide chains).

5. What are lipids and what are their main functions?

   Lipids are nonpolar (hydrophobic) biomolecules including fats, oils, waxes, and steroids; they serve in long-term energy storage, insulation, membrane structure, and as hormones.

6. What is the structure of a triglyceride (fat)?

   One glycerol molecule joined to three fatty acid chains by ester bonds (formed via condensation).

7. What is the difference between saturated and unsaturated fatty acids?

   Saturated fatty acids have no carbon-carbon double bonds (solid fats, mostly animal). Unsaturated fatty acids have one or more double bonds (liquid oils, mostly plant).

8. What is a phospholipid and why is it important in cell membranes?

   A lipid with two fatty acids and a phosphate group attached to glycerol; its hydrophilic head and hydrophobic tails form the bilayer basis of cell membranes.

9. What are nucleic acids and their monomer units?

   Nucleic acids (DNA and RNA) are polymers of nucleotides; each nucleotide consists of a pentose sugar, a phosphate group, and a nitrogenous base.

10. What are the structural differences between DNA and RNA?

    DNA is double-stranded, contains deoxyribose sugar, and the base thymine. RNA is single-stranded, contains ribose sugar, and the base uracil instead of thymine.

11. What are the nitrogenous bases of DNA and how do they pair?

    Purines: adenine (A) and guanine (G); pyrimidines: cytosine (C) and thymine (T). Base pairing: A pairs with T (2 H-bonds), G pairs with C (3 H-bonds).

12. What is a conjugated molecule? Give examples.

    A conjugated molecule is a biomolecule combined with a non-protein/non-carbohydrate group. Examples: glycoproteins (protein + carbohydrate), lipoproteins (lipid + protein), glycolipids (lipid + carbohydrate), and nucleoproteins (nucleic acid + protein).

13. What are enzymes and what is their chemical nature?

    Enzymes are biological catalysts, mostly globular proteins, that speed up biochemical reactions by lowering the activation energy without being consumed.

14. List four key properties/characteristics of enzymes.

    They are specific to a substrate, highly efficient, required in small amounts (catalytic), sensitive to temperature and pH, and not consumed or permanently changed by the reaction.

15. What is the active site of an enzyme?

    A specific region on the enzyme, with a particular shape, where the substrate binds and the catalytic reaction takes place.

16. Compare the lock-and-key and induced-fit models of enzyme action.

    In the lock-and-key model the substrate fits exactly into a rigid active site. In the induced-fit model the active site changes shape slightly to mould around the substrate for a better fit.

17. What is an enzyme-substrate complex?

    The temporary intermediate formed when the substrate binds to the active site of the enzyme, where the substrate is converted into products before being released.

18. How does temperature affect enzyme activity?

    Activity increases with temperature up to an optimum (about 37°C in humans); beyond this the enzyme denatures, loses its shape, and activity falls sharply.

19. How does pH affect enzyme activity?

    Each enzyme has an optimum pH at which activity is maximal; extreme pH changes the enzyme's shape (denaturation) and reduces activity (e.g. pepsin works best at acidic pH ~2).

20. What is the difference between competitive and non-competitive enzyme inhibitors?

    A competitive inhibitor resembles the substrate and binds to the active site, blocking the substrate. A non-competitive inhibitor binds to a site other than the active site (allosteric), changing the enzyme's shape so the substrate cannot react.

21. What is a cofactor and a coenzyme?

    A cofactor is a non-protein helper required for enzyme activity; inorganic cofactors are metal ions (e.g. Mg2+, Zn2+), while organic cofactors are coenzymes (e.g. NAD, FAD, vitamins).

22. List four key differences between prokaryotic and eukaryotic cells.

    Prokaryotes lack a true membrane-bound nucleus and membrane-bound organelles, have a single circular DNA, and 70S ribosomes. Eukaryotes have a true nucleus, membrane-bound organelles, linear DNA in chromosomes, and 80S ribosomes.

23. Give examples of prokaryotic and eukaryotic organisms.

    Prokaryotes: bacteria and cyanobacteria (blue-green algae). Eukaryotes: protists, fungi, plants, and animals.

24. Why are viruses not classified as either prokaryotic or eukaryotic cells?

    Because viruses are acellular (non-cellular), lacking cytoplasm, organelles, and the machinery for independent metabolism or reproduction; they replicate only inside a host cell.

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