Cambodia Health Entrance Exam cheat sheet

Cell theory: all living things are made of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells by division.

Prokaryotes lack a membrane-bound nucleus and mitochondria; eukaryotes have a nucleus, mitochondria, and membrane-bound organelles.

Mitosis produces two genetically identical diploid daughter cells; meiosis produces four genetically distinct haploid gametes.

DNA base pairing: adenine pairs with thymine (two hydrogen bonds), guanine pairs with cytosine (three hydrogen bonds).

Human blood groups follow ABO inheritance: IA and IB are codominant, and both are dominant over i; O is the recessive ii genotype.

Photosynthesis: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2, occurring in chloroplast thylakoids and stroma.

Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP; glycolysis occurs in cytoplasm, the Krebs cycle and electron transport in mitochondria.

Enzymes are biological catalysts that lower activation energy; each has an active site whose shape determines substrate specificity.

In a human somatic cell there are 46 chromosomes (23 pairs); a gamete carries 23 chromosomes.

Mole concept: 1 mole = 6.022 × 10^23 particles (Avogadro's number); moles = mass in grams ÷ molar mass.

Molarity (M) = moles of solute ÷ liters of solution; dilution obeys M1V1 = M2V2.

Ideal gas law: PV = nRT, with R = 8.314 J/(mol·K) or 0.0821 L·atm/(mol·K); at STP 1 mole of gas occupies 22.4 L.

pH = −log[H+]; pH below 7 is acidic, 7 is neutral, above 7 is basic; pH + pOH = 14 at 25 °C.

Oxidation is loss of electrons and reduction is gain of electrons (OIL RIG); in a redox reaction the oxidizing agent is itself reduced.

Balancing equations conserves atoms and charge; coefficients give mole ratios used in stoichiometric calculations.

Periodic trends: atomic radius decreases across a period and increases down a group; electronegativity increases across a period and decreases down a group.

Ionic bonds form by electron transfer between metal and nonmetal; covalent bonds form by electron sharing between nonmetals.

Newton's second law: F = ma, where force is in newtons, mass in kilograms, acceleration in m/s².

Kinematics: v = u + at, s = ut + ½at², and v² = u² + 2as for constant acceleration.

Weight = mg, with g ≈ 9.8 m/s² near Earth's surface; mass is constant while weight depends on gravity.

Work = force × displacement × cos θ; power = work ÷ time; kinetic energy = ½mv²; gravitational potential energy = mgh.

Ohm's law: V = IR; electrical power P = VI = I²R = V²/R.

Series circuits share one current; parallel circuits share one voltage across branches.

Wave relation: v = fλ, where speed equals frequency times wavelength.

Pressure = force ÷ area (P = F/A); liquid pressure P = ρgh depends on density and depth, not on container shape.

Refraction follows Snell's law: n1 sin θ1 = n2 sin θ2; light bends toward the normal when entering a denser medium.

Quadratic formula: for ax² + bx + c = 0, x = [−b ± √(b² − 4ac)] ÷ 2a; the discriminant b² − 4ac gives two, one, or no real roots.

Slope of a line through (x1, y1) and (x2, y2) is (y2 − y1) ÷ (x2 − x1); parallel lines have equal slopes, perpendicular slopes multiply to −1.

Pythagorean theorem: a² + b² = c² for a right triangle, where c is the hypotenuse.

Area formulas: triangle ½bh, circle πr², trapezoid ½(a + b)h; circumference of a circle is 2πr.

Volume formulas: cylinder πr²h, cone ⅓πr²h, sphere (4/3)πr³.

Logarithm rules: log(ab) = log a + log b; log(a/b) = log a − log b; log(aⁿ) = n log a.

Arithmetic sequence: nth term a + (n − 1)d; sum of n terms = n/2 × [2a + (n − 1)d].

Probability of an event = favorable outcomes ÷ total equally likely outcomes; independent events multiply their probabilities.

Number series: check differences first, then ratios, then alternating or squared patterns before assuming a rule.

If all A are B and all B are C, then all A are C (valid syllogism); the converse of a true statement is not automatically true.

In a sequence of consecutive integers, the mean equals the median; for evenly spaced values, mean = (first + last) ÷ 2.

Average speed for equal distances at speeds a and b is the harmonic mean 2ab ÷ (a + b), not (a + b) ÷ 2.

Work-rate rule: if one worker finishes in x days and another in y days, together they finish in xy ÷ (x + y) days.

Percent change = (new − old) ÷ old × 100; a 20% increase followed by a 20% decrease leaves the value at 96% of the original.

Direction and seating puzzles: draw a diagram and fix one reference point rather than tracking positions mentally.

Clock angle: angle between hands = |30H − 5.5M|, where H is the hour and M the minute.

Khmer script descends from the Brahmi family; the modern alphabet has 33 consonants, with subscripts (coeng) used to form consonant clusters.

Khmer vowels are written as dependent signs attached above, below, before, or after a consonant; two vowel series (a-series and o-series) change the vowel sound.

The Reamker is the Khmer version of the Ramayana epic; it is central to Cambodian classical dance and shadow theatre (Sbek Thom).

Chbab (didactic poems) such as Chbab Srey and Chbab Proh are classical works giving moral instruction in verse.

Angkor Wat was built in the 12th century under King Suryavarman II and is depicted on the national flag of Cambodia.

The Khmer Empire's capital Yasodharapura was centered near Angkor; Jayavarman VII built the Bayon and Preah Khan.

Cambodia's Constitution (1993) establishes a constitutional monarchy with a Prime Minister as head of government.

Tonle Sap is the largest freshwater lake in Southeast Asia; its flow reverses seasonally with the Mekong's flood pulse.

Khmer New Year (Choul Chnam Thmey) is celebrated in mid-April and marks the end of the harvest season.