Biology I: Introduction to Biology and the Chemical Basis of Life
❦
The NIE Biology syllabus (implemented from 2017) has nine units: Introduction to Biology (5 periods); Chemical and Cellular Basis of Life (80); Evolution and Diversity of Organisms (60); Plant Form and Function (80); Animal Form and Function (195); Genetics (25); Molecular Biology and Recombinant DNA Technology (40); Environmental Biology (40); and Microbiology (50) (NIE, n.d.-a). A proposal to restructure it into 14 units has been circulated, so check the current version (NIE, n.d.-c).
The Nature of Biology
- Characteristics of life: organization, metabolism, growth and development, reproduction, response to stimuli, homeostasis, adaptation, and evolution.
- Levels of organization: molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
- The scientific method: observation, question, hypothesis, prediction, experiment (with controls), data analysis, conclusion, and communication. Good experiments change one variable at a time and use replicates.
- Branches: botany, zoology, microbiology, cell biology, genetics, ecology, physiology, biochemistry, and more. Biology contributes to solving human problems in health, food, and the environment.
- Ethics: respect for life, animal welfare in experiments, informed consent in human studies, and the responsible use of biotechnology.
Elements and Water
The main elements of living things are C, H, O, N, P, S (and the minerals Ca, K, Na, Mg, Fe, Cl). Water is essential because of its properties: it is a polar solvent; has cohesion and adhesion (capillary movement in plants); a high specific heat capacity and high latent heat of vaporization (temperature stability and cooling by sweating or transpiration); and ice is less dense than liquid water (aquatic life survives under ice).
Biomolecules
| Molecule | Building blocks | Key features and functions |
|---|---|---|
| Carbohydrates | Monosaccharides (glucose, fructose, galactose) | Disaccharides: sucrose (glucose + fructose), maltose (glucose + glucose), lactose (glucose + galactose). Polysaccharides: starch (plant energy store; amylose and amylopectin), glycogen (animal store), cellulose (β-1,4 linkages; structural), chitin |
| Lipids | Glycerol + fatty acids | Triglycerides (energy storage, insulation); phospholipids (membranes); steroids such as cholesterol; saturated versus unsaturated fatty acids |
| Proteins | 20 amino acids joined by peptide bonds | Four levels of structure: primary (sequence), secondary (α-helix, β-sheet), tertiary (folding), quaternary (several chains). Functions: enzymes, transport, structure, defence, hormones, movement. Denaturation changes shape and destroys function |
| Nucleic acids | Nucleotides (pentose sugar + phosphate + base) | DNA (A pairs with T by two hydrogen bonds; G with C by three); RNA (uracil replaces thymine); store and express genetic information |
Know the food tests: Benedict's (reducing sugars, brick-red), iodine (starch, blue-black), biuret (protein, purple), and the ethanol emulsion test (lipids, cloudy white).
Enzymes
Enzymes are biological catalysts, mostly proteins, that lower the activation energy of reactions. Substrates bind to the active site (the induced-fit model refines the lock-and-key model). The rate depends on temperature (increasing up to an optimum, then denaturation), pH, substrate concentration (reaching V_max when saturated, with a Michaelis constant K_m), and enzyme concentration. Inhibitors can be competitive (compete for the active site) or non-competitive (bind elsewhere). Cofactors and coenzymes (many vitamins) assist enzymes. Medical relevance: many drugs are enzyme inhibitors, and enzyme levels in blood help diagnose disease (Berg et al., 2019; Nelson & Cox, 2021).
Common Mistakes
- Confusing the polysaccharides' structures and functions.
- Saying enzymes are "used up" or "killed" (they are denatured, not killed).
- Forgetting that low temperature slows enzymes but does not denature them.
CHAPTER 4