AKU BScN Admission Test Biology Syllabus

What happens to an enzyme at temperatures above its optimum?

Excess heat breaks bonds in the tertiary structure, denaturing the enzyme; the active site loses its shape and the enzyme can no longer bind substrate.

What is the difference between competitive and non-competitive enzyme inhibition?

A competitive inhibitor binds the active site and competes with the substrate; a non-competitive inhibitor binds elsewhere (allosteric site), changing the active site's shape.

Write the overall word equation for aerobic respiration.

Glucose + oxygen -> carbon dioxide + water + energy (ATP). Balanced: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP.

Name the four stages of aerobic respiration and where each occurs.

Glycolysis (cytoplasm), link reaction and Krebs cycle (mitochondrial matrix), and oxidative phosphorylation/electron transport chain (inner mitochondrial membrane).

What is ATP and why is it called the energy currency of the cell?

Adenosine triphosphate; it stores energy in high-energy phosphate bonds and releases it when hydrolyzed to ADP + Pi, powering cellular processes.

How many net ATP molecules are produced per glucose in aerobic respiration versus glycolysis alone?

Aerobic respiration yields about 36-38 ATP per glucose, while glycolysis alone yields a net of 2 ATP.

What are the products of anaerobic respiration in humans and in yeast?

In humans: lactic acid (lactate) + 2 ATP; in yeast: ethanol + carbon dioxide + 2 ATP (fermentation).

Write the overall word equation for photosynthesis.

Carbon dioxide + water -> glucose + oxygen (in the presence of light and chlorophyll). Balanced: 6CO2 + 6H2O -> C6H12O6 + 6O2.

What are the two stages of photosynthesis and where does each occur?

The light-dependent reactions (in the thylakoid membranes) and the light-independent reactions/Calvin cycle (in the stroma of the chloroplast).

What are the products of the light-dependent reactions of photosynthesis?

ATP, NADPH (reduced NADP), and oxygen (from the photolysis of water).

Describe the structure of DNA according to Watson and Crick.

A double helix of two antiparallel polynucleotide strands held by hydrogen bonds between complementary base pairs, with a sugar-phosphate backbone.

State the base-pairing rules in DNA.

Adenine pairs with thymine (A-T) via two hydrogen bonds, and cytosine pairs with guanine (C-G) via three hydrogen bonds.

Why is DNA replication described as semi-conservative?

Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand, so half of the original is conserved.

What is the role of DNA helicase and DNA polymerase in replication?

Helicase unwinds and unzips the double helix by breaking hydrogen bonds; DNA polymerase adds complementary nucleotides to form the new strand.

What is transcription and where does it occur in eukaryotes?

Transcription is the synthesis of mRNA from a DNA template by RNA polymerase; it occurs in the nucleus.

What is translation and where does it occur?

Translation is the synthesis of a polypeptide from the mRNA codon sequence; it occurs on ribosomes in the cytoplasm.

What is a codon and what is an anticodon?

A codon is a triplet of bases on mRNA coding for one amino acid; an anticodon is the complementary triplet on tRNA that pairs with the codon.

List the three main differences between DNA and RNA.

DNA is double-stranded, contains deoxyribose, and uses thymine; RNA is single-stranded, contains ribose, and uses uracil instead of thymine.

State Mendel's Law of Segregation.

The two alleles of a gene separate during gamete formation so that each gamete carries only one allele for each trait.

State Mendel's Law of Independent Assortment.

Alleles of different genes are distributed to gametes independently of one another (applies to genes on different chromosomes).

In a monohybrid cross between two heterozygotes (Tt x Tt), what is the genotypic and phenotypic ratio?

Genotypic ratio 1 TT : 2 Tt : 1 tt; phenotypic ratio 3 dominant : 1 recessive.

Define homozygous, heterozygous, genotype, and phenotype.

Homozygous: two identical alleles; heterozygous: two different alleles; genotype: genetic makeup; phenotype: observable physical characteristics.

What is the expected phenotypic ratio of a dihybrid cross between two heterozygotes (e.g., RrYy x RrYy)?

9 : 3 : 3 : 1.

What is a gene mutation, and name its three point-mutation types.

A change in the DNA base sequence; the three substitution/point types are silent (no change), missense (different amino acid), and nonsense (premature stop codon).

What is the difference between a frameshift mutation and a substitution mutation?

A frameshift (insertion or deletion of bases) shifts the reading frame, altering every downstream codon; a substitution changes only one base/codon.

Distinguish between continuous and discontinuous variation.

Continuous variation shows a range of phenotypes (e.g., height) controlled by many genes; discontinuous variation shows distinct categories (e.g., blood group) controlled by one or few genes.

What is recombinant DNA, and what enzymes are used to make it?

Recombinant DNA is DNA combining genetic material from two different sources; restriction endonucleases cut DNA and DNA ligase joins the fragments.

What is a restriction enzyme and what are sticky ends?

A restriction enzyme cuts DNA at specific recognition sequences; sticky ends are the short, single-stranded overhangs left after a staggered cut that allow complementary fragments to join.

What is a vector in genetic engineering, and give two common examples?

A vector is a carrier that transfers a gene into a host cell; common examples are plasmids and bacteriophages (viruses).

Give two applications of genetic engineering in medicine and agriculture.

Medicine: production of human insulin and growth hormone by bacteria, and gene therapy; Agriculture: pest-resistant and improved-yield genetically modified (GM) crops.