CAPE Biology Unit 1 cheat sheet

Prokaryotic cells lack membrane-bound organelles and a true nucleus; their DNA is a circular chromosome in a nucleoid region, and they may carry plasmids, 70S ribosomes, and a peptidoglycan wall.

Eukaryotic organelles: nucleus (chromatin, nucleolus), rough ER (ribosome-studded, protein synthesis), smooth ER (lipid synthesis, detoxification), Golgi (modification and packaging), lysosomes (hydrolytic enzymes), mitochondria (aerobic respiration), chloroplasts (photosynthesis).

Endosymbiotic theory evidence: mitochondria and chloroplasts have double membranes, circular DNA, 70S ribosomes, and divide independently of the cell.

Magnification = image size / actual size; keep units consistent (convert µm to mm by multiplying by 1000).

Resolution is the ability to distinguish two close points; electron microscopes have higher resolution than light microscopes because of shorter electron wavelength.

Diffusion is passive movement down a concentration gradient; rate increases with steeper gradient, higher temperature, larger surface area, and shorter distance.

Osmosis is diffusion of water across a selectively permeable membrane from higher to lower water potential; water potential of pure water at atmospheric pressure is 0 kPa.

Active transport moves substances against a concentration gradient using ATP and carrier proteins; it is saturable and inhibited by metabolic poisons.

Fluid mosaic model: phospholipid bilayer with embedded proteins, cholesterol, and glycoproteins; membrane fluidity depends on phospholipid tail saturation and cholesterol content.

Carbohydrates: monosaccharides (glucose, fructose), disaccharides (maltose, sucrose, lactose) joined by glycosidic bonds, polysaccharides (starch, glycogen, cellulose) joined by glycosidic bonds.

Starch is a storage polysaccharide of alpha-glucose (amylose unbranched, amylopectin branched); glycogen is more highly branched for rapid glucose release; cellulose is beta-glucose chains with 1,4 bonds forming microfibrils.

Proteins are polymers of amino acids joined by peptide bonds; primary structure is amino acid sequence, secondary is alpha-helix or beta-pleated sheet held by hydrogen bonds, tertiary is 3D folding via ionic, hydrogen, disulfide, and hydrophobic interactions, quaternary is multiple polypeptide chains.

Lipids: triglycerides are glycerol plus three fatty acids joined by ester bonds; saturated fatty acids lack double bonds, unsaturated have C=C double bonds; phospholipids are amphipathic with a hydrophilic head and hydrophobic tails.

Benedict's test: reducing sugars give a brick-red precipitate on heating; non-reducing sugars require prior acid hydrolysis and neutralisation.

Biuret test: proteins give a purple colour; iodine test: starch gives blue-black; emulsion test: lipids give a cloudy white emulsion with ethanol and water.

Enzymes are biological catalysts that lower activation energy; they are specific to their substrate at the active site.

Factors affecting enzyme activity: temperature (denaturation above optimum), pH (changes ionisation of active site), substrate concentration (rate plateaus at Vmax), enzyme concentration, and inhibitors.

Competitive inhibitors bind the active site and are overcome by increasing substrate concentration; non-competitive inhibitors bind elsewhere and change enzyme shape, so they are not overcome by more substrate.

DNA is a double helix of nucleotides (deoxyribose, phosphate, nitrogenous base); adenine pairs with thymine (two hydrogen bonds), guanine with cytosine (three hydrogen bonds).

DNA replication is semi-conservative: helicase unwinds, each strand acts as template, DNA polymerase adds complementary nucleotides, and each daughter molecule has one old and one new strand.

Transcription produces mRNA from a DNA template in the nucleus; translation at ribosomes uses tRNA anticodons to add amino acids in the sequence specified by mRNA codons.

The genetic code is triplet, degenerate (multiple codons per amino acid), non-overlapping, and universal.

Mitosis produces two genetically identical diploid daughter cells for growth and repair; meiosis produces four genetically varied haploid cells for gamete formation.

Meiosis variation sources: independent assortment of homologous chromosomes in meiosis I and crossing over between non-sister chromatids.

Monohybrid cross ratios: F2 from heterozygous parents gives 3:1 phenotype and 1:2:1 genotype; test cross with a recessive homozygote reveals unknown genotype.

Codominance and incomplete dominance modify expected ratios; sex-linked traits show different inheritance patterns in males and females.

Classification hierarchy: domain, kingdom, phylum, class, order, family, genus, species; binomial nomenclature uses genus and species names in italics.