Science
The Science domain samples basic biology, human anatomy and physiology, chemistry, and physics, plus scientific reasoning. It is not a full premedical exam; it rewards core principles and the ability to apply them to short scenarios.
Biology and body systems
- Cell membrane: selectively permeable. Diffusion moves solutes from high to low concentration; osmosis moves water toward the higher solute concentration.
- Organelles: mitochondria produce ATP, ribosomes make protein, rough ER transports it, the Golgi packages it, lysosomes digest waste.
- Genetics: DNA → mRNA → protein. Mitosis produces identical body cells; meiosis produces gametes with half the chromosome number.
- Homeostasis: negative feedback reverses change. Insulin lowers blood glucose; glucagon raises it.
- Circulation: right heart → lungs → left heart → body. Arteries carry blood away from the heart; veins return it. Gas exchange occurs in alveoli.
Chemistry and physics
- pH below 7 is acidic, above 7 is basic; each unit is a tenfold change.
- Covalent bonds share electrons; ionic bonds transfer them.
- Force = mass × acceleration; pressure = force ÷ area; energy is conserved but can change form.
Worked example
A red blood cell is placed in distilled water. Distilled water has essentially no dissolved solute, while the cytoplasm contains salts and proteins. Water moves by osmosis into the cell, which swells and may hemolyze. The solutes cannot cross freely, but water can, so the concentration gradient drives water inward.
Traps that cost marks
- Saying oxygen-rich blood travels in the pulmonary artery; it returns to the left heart through pulmonary veins.
- Confusing solute diffusion with water osmosis.
- Treating a lower pH as less acidic.
- Assuming correlation proves causation in an experiment description.