NBE Sciences flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Cell theory

All living organisms are composed of one or more cells; the cell is the basic unit of life; and new cells arise from pre-existing cells through division.

Mitosis vs. meiosis

Mitosis produces two identical diploid cells for growth and repair; meiosis produces four genetically diverse haploid gametes, including crossing over in prophase I.

Enzyme function

Enzymes are proteins that lower activation energy, speeding up reactions without being consumed; activity depends on pH, temperature, substrate concentration, and inhibitors.

DNA replication

Semiconservative process in S phase where each parental DNA strand serves as a template for a new complementary strand, resulting in two identical double helices.

Ideal gas law

PV = nRT, where P is pressure, V is volume, n is moles, R is 0.08206 L·atm/(mol·K), and T is temperature in Kelvin; at STP, one mole occupies 22.4 L.

pH and pOH

pH = -log[H+] and pOH = -log[OH-]; at 25°C, pH + pOH = 14; acidic solutions have pH < 7, basic > 7.

Le Chatelier's principle

When a system at equilibrium is disturbed by changes in concentration, pressure, or temperature, the equilibrium shifts to counteract the disturbance and restore balance.

Molarity and dilution

Molarity (M) = moles of solute per liter of solution; dilution follows M1V1 = M2V2, where subscripts 1 and 2 represent initial and final states.

SN1 vs. SN2

SN1 is a two-step reaction via carbocation, favored by tertiary substrates and polar protic solvents, causing racemization; SN2 is concerted backside attack, favored by primary substrates and polar aprotic solvents, causing inversion.

Aromaticity (Hückel rule)

A cyclic, planar, fully conjugated molecule with 4n+2 π electrons is aromatic; benzene (6 π electrons) is aromatic, while cyclobutadiene (4 π electrons) is antiaromatic.

Functional group priority

For IUPAC naming, the suffix priority is carboxylic acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine > alkene/alkyne > alkane > ether > halide.

Electrophilic aromatic substitution

Activating groups (–OH, –NH2, –OR, alkyl) direct ortho/para; deactivating groups (–NO2, –CN, carbonyl) direct meta; halogens are deactivating but ortho/para directing.

Newton's second law

The net force acting on an object equals its mass times its acceleration (F = ma); force and acceleration are vectors in the same direction.

Ohm's law and power

V = IR, where V is voltage, I is current, and R is resistance; electrical power P = IV = I²R = V²/R; series resistors add, parallel resistors use reciprocal sum.

Snell's law

n1 sinθ1 = n2 sinθ2 describes refraction at an interface; total internal reflection occurs when light travels from higher to lower index and exceeds the critical angle θc = sin⁻¹(n2/n1).

Conservation of momentum

In an isolated system, total momentum (p = mv) remains constant; impulse J = FΔt = Δp; elastic collisions conserve kinetic energy, inelastic do not.

Anatomical position

Standing erect, face forward, arms at sides with palms forward; directional terms include anterior, posterior, superior, inferior, medial, lateral, proximal, and distal.

Body planes

Sagittal plane divides left and right; coronal (frontal) plane divides anterior and posterior; transverse (horizontal) plane divides superior and inferior.

Bone cells

Osteoblasts build bone matrix; osteocytes maintain matrix; osteoclasts resorb bone; osteons are structural units of compact bone.

Muscle types

Skeletal muscle is voluntary and striated; cardiac muscle is involuntary, striated, with intercalated discs; smooth muscle is involuntary and non-striated.

Resting membrane potential

The inside of a neuron is about -70 mV relative to the outside, maintained by the Na+/K+ ATPase pump (3 Na+ out, 2 K+ in) and K+ leak channels.

Action potential

Depolarization occurs via Na+ influx when threshold (~-55 mV) is reached; repolarization via K+ efflux; refractory periods prevent backward propagation.

Cardiac output

Cardiac output = heart rate × stroke volume; average resting output is about 5 L/min; regulated by autonomic tone, preload, afterload, and contractility.

Nephron function

The nephron filters blood at the glomerulus, reabsorbs glucose, amino acids, and water in tubules, secretes wastes, and excretes urine; ADH increases water reabsorption.

Necrosis types

Coagulative necrosis occurs in ischemia; liquefactive in brain infarcts and abscesses; caseous in tuberculosis; fat necrosis in pancreatitis; fibrinoid in vasculitis.

Virchow's triad

Thrombosis is promoted by endothelial injury, stasis or turbulence of blood flow, and hypercoagulability; an embolus is a thrombus that travels and lodges elsewhere.

Benign vs. malignant

Benign tumors are encapsulated, non-invasive, and well-differentiated; malignant tumors invade, metastasize, show anaplasia, and have high mitotic rates.

Tumor suppressor genes

Genes such as p53 and RB inhibit cell proliferation; loss of function (two-hit hypothesis) contributes to cancer; oncogenes like RAS and MYC promote proliferation.

Gram stain

Gram-positive bacteria retain crystal violet (purple) due to thick peptidoglycan; Gram-negative bacteria lose it and counterstain pink due to thin peptidoglycan and outer membrane.

Bacterial growth curve

Lag phase (adaptation), log phase (exponential growth), stationary phase (growth equals death), and death phase; generation time varies by species and conditions.

Sterilization vs. disinfection

Sterilization kills all microorganisms including spores; disinfection reduces pathogens on inanimate objects; antiseptics are applied to living tissue.

Dental amalgam

An alloy of silver, tin, copper, and mercury that sets by amalgamation; strong and durable but non-esthetic and not adhesively bonded.