Cell Biology and Biochemistry
What to know
This domain spans macromolecules (carbohydrates, lipids, proteins, nucleic acids), enzymes, membrane structure and transport, organelles, cellular respiration, photosynthesis, and the cell cycle. Know the four macromolecule classes and their monomers and functions. Understand enzyme catalysis, the effect of temperature and pH, and the lock-and-key/induced-fit ideas. For membranes, distinguish diffusion, facilitated diffusion, osmosis, and active transport (which requires energy). Know organelle functions: mitochondria (ATP), chloroplasts (photosynthesis), ribosomes (protein synthesis), ER and Golgi (processing and transport), lysosomes (digestion), nucleus (DNA). Compare prokaryotic and eukaryotic cells. Understand the inputs and outputs of respiration and photosynthesis and where each occurs.
Traps
Questions mix up the location of processes (glycolysis in cytoplasm, Krebs cycle and electron transport in mitochondria; light reactions in thylakoids, Calvin cycle in stroma). Watch for confusion between osmosis (water movement) and diffusion of solutes, and between passive and active transport. A frequent trap is asking which direction water moves across a membrane: water moves toward the higher solute concentration. Another is confusing the products of photosynthesis and respiration.
Worked example
A cell is placed in a hypertonic solution. Because the outside has a higher solute concentration, water leaves the cell by osmosis and the cell shrinks. Rule of thumb: water always moves from lower solute concentration to higher solute concentration across a semipermeable membrane.
Rule of thumb
Match each process to its organelle or compartment before answering; location questions are common.