NEET UG High-Yield Review (Biology, Physics, Chemistry) · Flashcards públicos

Pregunta 1: Which organelle is the primary site of aerobic ATP generation in eukaryotic cells?

Mostrar resposta

Respuesta

Mitochondria, containing the Krebs cycle enzymes in the matrix and the electron transport chain (ETC) in the cristae inner membrane.

Often termed the powerhouse of the cell, mitochondria possess their own circular DNA and 70S ribosomes following the endosymbiotic theory.

Pregunta 2: What is the expected phenotypic and genotypic ratio in a classic Mendelian monohybrid cross ( $Aa \times Aa$ )?

Mostrar resposta

Respuesta

Phenotypic ratio: $3:1$ (dominant : recessive); Genotypic ratio: $1:2:1$ ( $1\,AA : 2\,Aa : 1\,aa$ ).

This segregation of alleles into gametes demonstrates Mendel's Law of Segregation, occurring during Anaphase I of meiosis.

Pregunta 3: How does the countercurrent multiplier mechanism in the loop of Henle conserve water in mammalian kidneys?

Mostrar resposta

Respuesta

The descending limb is permeable to water but not salt; the ascending limb actively pumps $\text{NaCl}$ into the medullary interstitium, creating a hyperosmotic gradient.

This enables the collecting duct to reabsorb water via aquaporins regulated by Antidiuretic Hormone (ADH / Vasopressin).

Pregunta 4: What is Lindeman's 10% law of ecological trophic efficiency?

Mostrar resposta

Respuesta

Only approximately $10\%$ of the chemical energy stored in biomass at one trophic level is transferred to the next higher trophic level.

The remaining $90\%$ is dissipated as metabolic heat during respiration or lost through unconsumed biomass and excretion.

Pregunta 5: What is the formula for Coulomb's Law of electrostatic force between two point charges $q_1$ and $q_2$ in vacuum?

Mostrar resposta

Respuesta

$F = \frac{1}{4\pi\varepsilon_0} \frac{|q_1 q_2|}{r^2}$ , where $\frac{1}{4\pi\varepsilon_0} \approx 8.99 \times 10^9\text{ N}\cdot\text{m}^2/\text{C}^2$ .

Like charges repel and opposite charges attract along the line connecting their centers, obeying Newton's third law ( $F_{12} = -F_{21}$ ).

Pregunta 6: What is the equivalent resistance for two resistors $R_1$ and $R_2$ in parallel?

Mostrar resposta

Respuesta

$\frac{1}{R_{\text{eq}}} = \frac{1}{R_1} + \frac{1}{R_2} \implies R_{\text{eq}} = \frac{R_1 R_2}{R_1 + R_2}$ .

In parallel connections, voltage across both branches is identical, and total current is the sum of branch currents ( $I = I_1 + I_2$ ).

Pregunta 7: What is the efficiency $\eta$ of an ideal Carnot heat engine operating between temperatures $T_H$ and $T_C$ in Kelvin?

Mostrar resposta

Respuesta

$\eta = 1 - \frac{T_C}{T_H} = \frac{T_H - T_C}{T_H}$ .

No real engine operating between the two reservoirs can exceed the Carnot efficiency limit stipulated by the Second Law of Thermodynamics.

Pregunta 8: What is Snell's Law of refraction at the boundary between two optical media?

Mostrar resposta

Respuesta

$n_1 \sin(\theta_1) = n_2 \sin(\theta_2)$ , where $n$ is the refractive index and $\theta$ is the angle with the normal.

Total internal reflection occurs when light travels from a denser to rarer medium ( $n_1 > n_2$ ) at an incident angle exceeding the critical angle $\sin(\theta_c) = \frac{n_2}{n_1}$ .

Pregunta 9: What is the pH formula and the relation between pH and pOH at $25^\circ\text{C}$ ?

Mostrar resposta

Respuesta

$\text{pH} = -\log_{10}[\text{H}^+]$ and $\text{pH} + \text{pOH} = 14$ (since $K_w = [\text{H}^+][\text{OH}^-] = 1.0 \times 10^{-14}$ ).

A neutral solution at $25^\circ\text{C}$ has $\text{pH} = 7$ ; acidic solutions have $\text{pH} < 7$ and basic solutions have $\text{pH} > 7$ .

Pregunta 10: What does Gibbs Free Energy change $\Delta G = \Delta H - T\Delta S$ indicate regarding reaction spontaneity?

Mostrar resposta

Respuesta

If $\Delta G < 0$ , the process is spontaneous; if $\Delta G = 0$ , the system is in equilibrium; if $\Delta G > 0$ , the forward process is non-spontaneous.

An exothermic reaction ( $\Delta H < 0$ ) with positive entropy ( $\Delta S > 0$ ) is spontaneous at all temperatures.

Pregunta 11: What is Markovnikov's rule in electrophilic addition to unsymmetrical alkenes?

Mostrar resposta

Respuesta

The electrophilic hydrogen atom bonds to the double-bonded carbon with the greater number of hydrogen atoms, yielding the more stable carbocation intermediate.

Stability of carbocations follows tertiary ( $3^\circ$ ) > secondary ( $2^\circ$ ) > primary ( $1^\circ$ ) due to hyperconjugation and inductive electron donation.

Pregunta 12: What distinguishes an $\text{S}_\text{N}1$ reaction from an $\text{S}_\text{N}2$ nucleophilic substitution mechanism?

Mostrar resposta

Respuesta

$\text{S}_\text{N}1$ is unimolecular (two steps via planar carbocation, leading to racemization); $\text{S}_\text{N}2$ is bimolecular (one concerted step with backside attack, leading to Walden inversion).

$\text{S}_\text{N}1$ is favored by tertiary substrates and polar protic solvents, whereas $\text{S}_\text{N}2$ is favored by primary substrates and polar aprotic solvents.

Pregunta 13: What is the de Broglie wavelength formula for a particle of mass $m$ moving with velocity $v$ ?

Mostrar resposta

Respuesta

$\lambda = \frac{h}{p} = \frac{h}{mv} = \frac{h}{\sqrt{2mE_k}}$ .

This formula underpins wave-particle duality and the quantum mechanical model of atomic orbitals.

Pregunta 14: What is the function of Restriction Endonucleases (e.g., EcoRI) in recombinant DNA technology?

Mostrar resposta

Respuesta

They recognize specific palindromic nucleotide sequences in double-stranded DNA and cleave phosphodiester bonds, generating sticky or blunt ends.

Also known as molecular scissors, restriction enzymes allow target genes to be ligated into cloning vectors like plasmids (e.g., pBR322).

Pregunta 15: What are the stages of the cardiac cycle, and what do the P wave, QRS complex, and T wave represent on a normal ECG?

Mostrar resposta

Respuesta

P wave: atrial depolarization; QRS complex: ventricular depolarization; T wave: ventricular repolarization.

Atrial repolarization is masked inside the larger QRS ventricular depolarization signal.

Pregunta 16: What is the Lens Maker's Formula for a thin lens in air?

Mostrar resposta

Respuesta

$\frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$ , where $R_1$ and $R_2$ are the radii of curvature.

Convex lenses have positive focal lengths in air; concave lenses have negative focal lengths.

Pregunta 17: What is Faraday's law of electromagnetic induction?

Mostrar resposta

Respuesta

$\mathcal{E} = -\frac{d\Phi_B}{dt}$ , where the induced electromotive force equals the negative time rate of change of magnetic flux.

The negative sign represents Lenz's Law: the induced current flows in such a direction as to oppose the change in magnetic flux creating it.

Pregunta 18: What is the hybridization and molecular shape of a water molecule ( $\text{H}_2\text{O}$ )?

Mostrar resposta

Respuesta

$sp^3$ hybridization with a bent (V-shaped) geometry and a bond angle of approximately $104.5^\circ$ .

Oxygen has two bonding pairs and two lone pairs; lone pair-lone pair repulsion compresses the ideal tetrahedral $109.5^\circ$ angle to $104.5^\circ$ .

Pregunta 19: What hormone stimulates ovulation and the formation of the corpus luteum in human females?

Mostrar resposta

Respuesta

Luteinizing Hormone (LH), released in a massive mid-cycle surge from the anterior pituitary gland.

The resulting corpus luteum secretes high levels of progesterone to maintain the endometrial lining for prospective implantation.

Pregunta 20: What is the photoelectric equation formulated by Albert Einstein?

Mostrar resposta

Respuesta

$h\nu = \Phi + K_{\max} \implies K_{\max} = h\nu - h\nu_0$ , where $\Phi = h\nu_0$ is the work function of the metal.

Kinetic energy of photoelectrons depends on incident photon frequency $\nu$ , while the rate of photoelectron emission depends on light intensity.