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#pH

20 public questions tagged with this topic.

Cell Organelles

The hydrolytic enzymes of lysosomes function best at pH:

Lysosomal acid hydrolases number about sixty different enzymes covering proteolysis, glycoside cleavage, lipid hydrolysis, nuclease activity and sulfatase action, each evolutionarily tuned for acidic environments to maximize substrate turnover and simultaneously protect cell from uncontrolled proteolysis if leakage occurs. Most display pronounced pH optima between 4.5 and 5.0, precisely matching steady-state lumen acidity maintained by vacuolar H+ ATPase delivering protons and chloride counter-transport via ClC-7 Cl-/H+ antiporter that prevents excessive voltage buildup. At this acidic pH cata

Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 13: Lysosomal Acid Hydrolases – pH Optimum 4.5.

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Cell Organelles

Which pair of organelles have the same pH and ionic composition?

Ionic milieu of subcellular compartments reflects membrane permeability architecture and active pumping. The mitochondrial outer membrane contains abundant 19-stranded beta-barrel voltage-dependent anion channels, VDAC porins, present at high density allowing nonselective diffusion of solutes up to about 4 to 5 kilodaltons, including chloride, potassium, sodium, small metabolites, ATP, ADP, NADH and citrate. Because VDAC pores remain predominantly open under physiological low potentials, the intermembrane space equilibrates rapidly with cytosol via free diffusion, sharing near-identical pH aro

Ref: Nicholls & Ferguson, Bioenergetics, 4th ed., Chapter 3: Outer Membrane Permeability and Cytosol-Equilibrated Intermembrane Space.

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Acid-Base Theories - Arrhenius Bronsted-Lowry Lewis and Salts Hydrolysis

A weak acid HX has Ka = 2.5 × 10⁻⁶ . What is the pH of a solution made by mixing 0.1 M HX and 0.05 M NaX ?

Using Henderson-Hasselbalch: pH = pKa + log ([X-]/[HX]) , pKa = -log(2.5 × 10⁻⁶) ≈ 5.6 , ([X-]/[HX]) = (0.05/0.1) = 0.5 , pH = 5.6 + log 0.5 = 5.6 - 0.301 = 5.3 .

Ref: NCERT Class 11 Chemistry > Chapter 6: Equilibrium > Topic: Acid-Base Theories - Arrhenius Bronsted-Lowry Lewis and Salts Hydrolysis

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Water and Mole Concept

What is the pH of a neutral aqueous solution at 25°C?

7 accurately defines or describes the concept asked in this question. Within Water and Mole Concept, precise definitions and terminology are essential for clear scientific communication. The other options (0, 14, and 10) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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pH and Buffer

The buffering capacity is maximum when:

pH = pKa is the scientifically accurate answer to this question. Within the study of pH and Buffer, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of pH = pKa directly address what is being asked. Among the other options, pH = 7, pH > pKa, and pH < pKa do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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pH and Buffer

The pH of a 1M NaOH solution is approximately:

14 is the scientifically accurate answer to this question. Within the study of pH and Buffer, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of 14 directly address what is being asked. Among the other options, 10, 12, and 13 do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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pH and Buffer

What is the approximate pH of orange juice if it contains 0.1M citric acid (Ka = 7.4 × 10⁻⁴)?

2.07 accurately defines or describes the concept asked in this question. Within pH and Buffer, precise definitions and terminology are essential for clear scientific communication. The other options (4, 7, and 10) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2

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