Nature of Science and Cell Biology

Nature of Science

• The scientific method follows a process of observation, hypothesis formation, experimentation, data collection, and conclusion.
• A theory is a well-supported explanation, distinguishing it from a testable prediction, or hypothesis.
• Errors in experiments are systematic inaccuracies; mistakes are unintended actions.
• Mean represents the average; mode is the most frequent value; median is the middle value.
• Standard deviation quantifies data variability, depicted visually by error bars on graphs.

Cell Biology

• Cells are small to maximize surface area-to-volume ratios for efficient exchange.
• Prokaryotic cells lack a nucleus, while eukaryotic cells have membrane-bound organelles.
• Key life functions include metabolism, growth, reproduction, response, and homeostasis.
• Major organelles include the nucleus (DNA storage), ribosomes (protein synthesis), mitochondria (energy production), and Golgi apparatus (protein modification).
• Cholesterol stabilizes cell membranes; amphipathic phospholipids form bilayers.
• Osmosis involves water movement from lower to higher solute concentration; potatoes in hypotonic solutions gain mass; those in hypertonic solutions lose mass.
• Passive transport (diffusion, osmosis) requires no energy; active transport (Na+/K+ pump) requires energy.
• Hypertonic solution: higher solute concentration; hypotonic solution: lower solute concentration; isotonic solution: equal solute concentration

Molecular Biology

• Water's dipolarity facilitates cohesion, adhesion, and surface tension.
• Carbon's versatility enables the formation of diverse macromolecules.
• Four main macromolecules are proteins, carbohydrates, lipids, and nucleic acids, built from specific monomers forming polymers.
• Anabolism builds molecules (e.g. photosynthesis); catabolism breaks molecules down (e.g., respiration).
• Saturated fats are solid at room temperature; unsaturated fats are generally healthier.
• Proteins denature under extreme conditions, losing their shape and function.
• Enzymes act on substrates to form products, being reusable.

Cellular Respiration and Photosynthesis

• Cellular respiration equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.
• Aerobic respiration yields more ATP than anaerobic respiration.
• Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
• Light wavelength influences photosynthesis; red and blue light are most effective.

DNA and RNA

• DNA uses deoxyribose, while RNA uses ribose.
• DNA is double-stranded, RNA is single-stranded; both are nucleic acids.
• Covalent bonds form the sugar-phosphate backbone; hydrogen bonds link base pairs.
• Replication (DNA → DNA), transcription (DNA → RNA), and translation (RNA → protein) occur in the nucleus and cytoplasm.
• Codons (mRNA triplets) pair with anticodons (tRNA) to form proteins.

Genetic Code

• The codon chart matches RNA codons to amino acids.
• AUG is the start codon (methionine); UAA, UAG, and UGA are stop codons.
• Example: DNA sequence TAC CCC ACG → mRNA AUG GGG UGC → Amino acids: Met-Gly-Cys.

Digestive System

• Major organs include the mouth (mechanical digestion), esophagus (food transport), stomach (protein digestion), and intestines (nutrient absorption).
• Accessory organs are the liver (bile production) and pancreas (enzyme secretion).