Biochemistry Basics - Study Notes

Biochemistry: Core Concepts and Terminology

• What is Biochemistry?

  • Defined as the “Chemistry of life” – the study of the chemical composition of living matter and the physico-chemical processes underlying the phenomenon of life. It bridges biology and chemistry, exploring the molecules and reactions essential for life, such as metabolism, heredity, and disease.

• Phenomenon of Life (key processes):

  • Digestion

    • The intricate process of breaking down food into smaller, absorbable nutrient molecules. This involves both:

      • Mechanical digestion: Physical breakdown (e.g., chewing).

      • Chemical digestion: Enzymatic breakdown of complex macromolecules (carbohydrates, proteins, fats) into simpler components (monosaccharides, amino acids, fatty acids).

    • Ingestion is the first stage, involving the intake of food.

  • Absorption

    • The uptake of digested nutrients from the gastrointestinal tract (primarily the small intestine) into the bloodstream or lymphatic system, making them available for cellular use.

  • Metabolic Process / Metabolism

    • The sum of all life-sustaining chemical reactions that occur within organisms. Metabolism is broadly divided into two categories:

      • Catabolism: Breaking down complex molecules into simpler ones, releasing energy (e.g., cellular respiration, yielding ATP).

      • Anabolism: Building complex molecules from simpler ones, requiring energy input (e.g., protein synthesis).

  • Growth

    • Encompasses increases in body size and complexity, driven by nutrient assimilation, cellular proliferation, and differentiation. It includes development and maturation, leading to functional and physiological changes that maintain body activity and health.

  • Reproduction

    • The fundamental biological process by which new individuals (offspring) are produced from parents, ensuring the continuation of a species. It can be asexual (genetically identical offspring) or sexual (offspring with genetic material from two parents).

• Chemical Reactions in Living Matter

  • Oxidation

    • A chemical reaction that involves the loss of electrons by a molecule, atom, or ion. It often involves the gain of oxygen or loss of hydrogen. In biological systems, it's crucial for energy production (e.g., electron transport chain).

  • Reduction

    • A chemical reaction that involves the gain of electrons by a molecule, atom, or ion. It often involves the loss of oxygen or gain of hydrogen. Oxidation and reduction always occur together in redox reactions.

  • Concentration (chemical combination context)

    • This term, often used broadly, specifically refers to the union of simple fragments or monomers to form more complex compounds, such as in polymerization or condensation reactions, where smaller molecules combine to create larger ones (e.g., amino acids forming proteins).

    • Example: The formation of hydrogen sulfate ($H<em>2SO</em>4$) from hydrogen ($H<em>2$), sulfur (S), and oxygen ($O</em>2$) involves the combination of simpler elements.

  • Hydrolysis

    • A chemical reaction in which a water molecule (H₂O) is added to a substance, causing it to break down into two or more simpler compounds. It literally means “splitting with water.” This process is vital in digestion for breaking down polymers.

    • Example: The breakdown of a disaccharide (like sucrose) into two monosaccharides (glucose and fructose) via the addition of a water molecule.

  • Tautomerism / Isomeric transformation

    • A type of structural isomerism where compounds rapidly interconvert between two or more isomeric forms by the migration of a hydrogen atom and a change in the position of a double bond. This rearrangement of atoms within molecules forms a substance with different chemical properties, crucial in processes like DNA replication and mutagenesis.

  • Demethylation / Methylation

    • Methylation is the addition of a methyl group ( $-CH_3$ ) to a substrate molecule. It's significant in epigenetics (gene expression regulation), protein function, and neurotransmitter synthesis.

    • Demethylation is the removal of a methyl group from a molecule, often reversing the effects of methylation.

  • Deamination / Amination

    • Amination is the addition of an ammonia ($NH<em>3$) or an amino group ($-NH</em>2$) to a molecule.

    • Deamination is the removal of an amino group from a compound, a key step in amino acid metabolism and detoxification (e.g., conversion of amino acids to urea).

  • Decarboxylation / Carboxylation

    • Carboxylation is the addition of a carboxyl group ( $-COOH$ ) to a molecule, important in photosynthesis (CO₂ fixation) and fatty acid synthesis.

    • Decarboxylation is the removal of a carboxyl group, releasing carbon dioxide ($CO_2$). This reaction is central to several metabolic pathways, such as the citric acid cycle.

• Law of Mass Action (fundamental principle in reaction kinetics)

  • Statement: At a constant temperature, the rate of a chemical reaction is directly proportional to the product of the molar concentrations of the reacting substances, each raised to the power of its stoichiometric coefficient in the balanced chemical equation.

  • For a generic reversible reaction: $aA + bB ightleftharpoons cC + dD$

    • Velocity: The forward reaction velocity ($v<em>f$) depends on the product of the concentrations of reactants: $v</em>f = k<em>f[A]^a[B]^b$, where $k</em>f$ is the forward rate constant.

    • The reverse reaction velocity ($v<em>r$) depends on the product of the concentrations of products: $v</em>r = k<em>r[C]^c[D]^d$, where $k</em>r$ is the reverse rate constant.

  • Equilibrium: A state where the forward reaction speed ($v<em>f$) equals the reverse reaction speed ($v</em>r$), meaning the net change in concentrations of reactants and products is zero. At equilibrium, $K<em>{eq} = \frac{k</em>f}{k_r} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$.

  • Practical implication: Changes in the concentration of reactants or products, temperature, or pressure will cause the system to shift its equilibrium position to counteract the disturbance, as described by Le Chatelier's Principle.

• Hydrogen and Hydroxyl Ion Concentration (acidity and alkalinity)

  • The concentration of free $H^+$ (hydrogen ions, often referred to as protons) or $OH^-$ (hydroxyl ions) fundamentally determines the acidity or alkalinity of an aqueous solution.

  • Hydrogen ion ($H^+$) and hydroxyl ion ($OH^-$) are central to acid-base chemistry in biochemistry, influencing enzyme activity, protein structure, and cellular processes.

  • Acid Solution

    • Contains an excess concentration of hydrogen ions ([H^+] > [OH^-]). Acids are substances that donate protons ($H^+$) in solution (Brønsted-Lowry definition).

  • Alkaline (Basic) Solution

    • Contains a lower concentration of hydrogen ions ([H^+] < [OH^-]), meaning an excess of hydroxyl ions. Bases are substances that accept protons ($H^+$) in solution.

  • pH value

    • The strength of an acid or base is dependent on its chemical structure, its ability to ionize or dissociate in a given solvent, and the solvent itself.

    • Strong acids/bases dissociate almost completely in water, while weak acids/bases only partially dissociate, establishing an equilibrium. The degree of ionization is quantified by acid dissociation constant ($K<em>a$) or base dissociation constant ($K</em>b$), often expressed as $pK<em>a$ or $pK</em>b$.

• pH (potential of Hydrogen)

  • A logarithmic measure of the hydrogen ion concentration in a solution, indicating its acidity or alkalinity defined as $pH = -log_{10}[H^+]$.

  • Neutral solution has $pH = 7$ (where $[H^+] = [OH^-] = 10^{-7} M$ at $25^\circ C$).

  • pH > 7: alkaline (basic) solution, indicating a lower $[H^+]$ concentration.

  • pH < 7: acidic solution, indicating a higher $[H^+]$ concentration.

  • Biological systems maintain a narrow physiological pH range (e.g., blood pH typically $7.35-7.45$).

  • Isoelectric pH (pI)

    • The specific pH at which a molecule (especially an amino acid, peptide, or protein) carries no net electrical charge; that is, its overall charge is zero. At this state, the substance is amphoteric and exists predominantly as a zwitterion (containing both positive and negative charges internally).

    • At its pI, the solubility of proteins is typically minimal, and they tend to precipitate.

• Buffers

  • Buffers are aqueous solutions that conspicuously resist changes in pH upon the addition of small amounts of strong acid or strong base. They are crucial for maintaining a relatively constant hydrogen ion concentration.

  • Composition: Typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid.

  • Mechanism: They counteract shifts in $[H^+]$ by neutralizing added acids or bases. When an acid is added, the conjugate base component of the buffer system neutralizes it; when a base is added, the weak acid component neutralizes it. The effective buffering range is generally within one pH unit of the $pK<em>a$ of the weak acid component, described by the Henderson-Hasselbalch equation: $pH = pK</em>a + log\frac{['conjugate\ base']}{['weak\ acid']}$.

• Buffers (summary note)

  • Buffers are absolutely essential for maintaining stable physiological pH in biological systems (e.g., the bicarbonate buffer system in blood) by dampening fluctuations in hydrogen ion concentration, thus preserving cellular function and enzyme activity.

Colloids and Colloidal Systems

• Colloids definition

  • Colloids are mixtures in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. These particles are larger than molecules in true solutions but smaller than particles in suspensions, typically having a size range of $1 nm$ to $1000 nm$ (or $1 ext{ extmu}m$).

  • They do not pass through semipermeable membranes (like parchment or cellophane).

• Colloids classification

  • Lyophilic Colloids (Emulsoids)

    • "Solvent-loving" systems where the dispersed phase has a strong affinity for the dispersion medium. They are generally more stable due to a protective hydration shell around the particles.

    • Examples: starch, egg albumin, blood proteins (like hemoglobin), soap solutions, gelatin.

  • Lyophobic Colloids (Suspensoids)

    • "Solvent-hating" systems where the dispersed phase has little or no affinity for the dispersion medium. They are less stable and often require stabilizing agents to prevent coagulation.

    • Examples: gold sol, silver sol, platinum sol (metal particles dispersed in water).

• Diffusion through membranes

  • While crystalloids (substances in true solutions) readily diffuse through semipermeable membranes, colloids do not easily pass through such membranes due to their larger particle size. This property is exploited in dialysis, a process used to separate colloids from crystalloids.

• Colloid vs. Crystalloid distinction

  • The primary distinction lies in particle size. Colloids have particle sizes between those of true solutions (crystalloids) and suspensions. While the terms are often used to differentiate, it's also possible for some substances to exist as colloids under certain conditions and crystalloids under others (e.g., soap). The size of the solute particles is the most useful differentiating criterion.

Differences: Solutions, Colloids, and Suspensions

• TRUE SOLUTION (Homogeneous Mixture)

  1. Particles are individual molecules or ions, typically with a size of < 1 nm ($10^{-3} ext{ extmu}m$).

  2. Will pass freely through both filters and semipermeable membranes.

  3. Particles are invisible to the naked eye and even under an ultramicroscope.

  4. Exhibit molecular movement (fast, random Brownian motion at a microscopic scale, but the solution appears stable).

  5. Exhibit high osmotic pressure due to the large number of individual solute particles (van 't Hoff factor is relevant).

  6. Transparent and do not scatter light (no Tyndall effect).

  7. Do not require dialysis for separation from solvent, as components freely pass through membranes.

  8. Contain a large number of particles per given volume, contributing to colligative properties.

  9. Represent the smallest particle size category among the three.

• COLLOIDAL SOLUTION (Heterogeneous Mixture / Colloidal Dispersion)

  1. Molecular aggregates or macromolecules with particle sizes ranging from approx. $1 nm - 1000 nm$ ($10^{-3} ext{ extmu}m - 1 ext{ extmu}m$).

  2. Will pass through ordinary filters but not through semipermeable membranes.

  3. Particles are ultramicroscopic; not visible to the naked eye but can be observed with an ultramicroscope using light scattering.

  4. Exhibit Brownian movement (random zigzag motion of particles), which helps in their stability against sedimentation.

  5. Exhibit low osmotic pressure compared to true solutions of similar mass concentration, as there are fewer individual entities.

  6. Exhibit the Tyndall phenomenon (scatter light, making the beam visible through the solution) due to particle size.

  7. Can be purified by dialysis (separation from crystalloids using a semipermeable membrane).

  8. Contain a moderate number of particles compared to true solutions, leading to specific optical properties (light scattering).

  9. Intermediate in particle size.

• SUSPENSION (Heterogeneous Mixture)

  1. Large molecular aggregates visible to the naked eye, with particle sizes typically > 1000 nm (> 1 ext{ extmu}m).

  2. Particles will not pass through either filters or semipermeable membranes.

  3. Macroscopic - particles are visible to the naked eye upon standing.

  4. Exhibit slow gravitational movement; particles tend to settle out over time due to gravity, often with some limited Brownian motion before settling.

  5. Exhibit virtually no osmotic pressure solely from the suspended particles, as they are too large to significantly influence solvent movement across membranes.

  6. Opaque or cloudy and scatter light very strongly.

  7. Do not require dialysis for particle separation, as gravity or simple filtration can separate them.

  8. Contain relatively few particles (in terms of number density) compared to colloids or true solutions.

  9. Represent the largest particle size category.

Laboratory Equipment: Burettes

• Types of burette used in the lab

  • Volumetric burette (glass)

    • The traditional, most common type made of glass, featuring a long, graduated tube with a stopcock at the bottom. Used for highly precise delivery of variable volumes of liquid, primarily in titrations. Available in various classes (e.g., Class A, Class B) denoting different levels of accuracy.

  • Piston / Digital burette

    • Operates similarly to a syringe but with much higher precision. It uses a plunger (piston) to dispense liquid accurately, with the volume displayed digitally. This type minimizes human error in reading the meniscus and is often attached to a reservoir bottle.

  • Electric / Electronic burette

    • An advanced version of the digital burette, often motorized to control the piston movement, allowing for even more precise and repeatable dispensing rates. These burettes can often be programmed for automated titrations and are valued for their accuracy and ease of use in high-throughput or sensitive applications.

Other Connected Information

• Enzymes

  • Enzymes are highly specific biological catalysts, typically proteins, that significantly accelerate the rate of biochemical reactions without being consumed in the process. They are crucial in all life processes, including digestion, where they break down complex food molecules.

• Oxygen

  • An indispensable element in biochemistry, primarily because it is vital for aerobic respiration, the metabolic process that generates the majority of ATP (energy) in living organisms. It acts as the final electron acceptor in the electron transport chain and participates in numerous other oxidation reactions.

• DE- prefix

  • The prefix "DE-" consistently denotes the removal, separation, or loss of a substance or group in chemical nomenclature and biological processes (e.g., deamination, decarboxylation, dehydration

Biochemistry: Core Concepts and Terminology

• What is Biochemistry?

  • Defined as the “Chemistry of life” – the study of the chemical composition of living matter and the physico-chemical processes underlying the phenomenon of life. It bridges biology and chemistry, exploring the molecules and reactions essential for life, such as metabolism, heredity, and disease.

• Phenomenon of Life (key processes):

  • Digestion

    • The intricate process of breaking down food into smaller, absorbable nutrient molecules. This involves both:

      • Mechanical digestion: Physical breakdown (e.g., chewing).

      • Chemical digestion: Enzymatic breakdown of complex macromolecules (carbohydrates, proteins, fats) into simpler components (monosaccharides, amino acids, fatty acids).

    • Ingestion is the first stage, involving the intake of food.

  • Absorption

    • The uptake of digested nutrients from the gastrointestinal tract (primarily the small intestine) into the bloodstream or lymphatic system, making them available for cellular use.

  • Metabolic Process / Metabolism

    • The sum of all life-sustaining chemical reactions that occur within organisms. Metabolism is broadly divided into two categories:

      • Catabolism: Breaking down complex molecules into simpler ones, releasing energy (e.g., cellular respiration, yielding ATP).

      • Anabolism: Building complex molecules from simpler ones, requiring energy input (e.g., protein synthesis).

  • Growth

    • Encompasses increases in body size and complexity, driven by nutrient assimilation, cellular proliferation, and differentiation. It includes development and maturation, leading to functional and physiological changes that maintain body activity and health.

  • Reproduction

    • The fundamental biological process by which new individuals (offspring) are produced from parents, ensuring the continuation of a species. It can be asexual (genetically identical offspring) or sexual (offspring with genetic material from two parents).

• Chemical Reactions in Living Matter

  • Oxidation

    • A chemical reaction that involves the loss of electrons by a molecule, atom, or ion. It often involves the gain of oxygen or loss of hydrogen. In biological systems, it's crucial for energy production (e.g., electron transport chain).

  • Reduction

    • A chemical reaction that involves the gain of electrons by a molecule, atom, or ion. It often involves the loss of oxygen or gain of hydrogen. Oxidation and reduction always occur together in redox reactions.

  • Concentration (chemical combination context)

    • This term, often used broadly, specifically refers to the union of simple fragments or monomers to form more complex compounds, such as in polymerization or condensation reactions, where smaller molecules combine to create larger ones (e.g., amino acids forming proteins).

    • Example: The formation of hydrogen sulfate ($H<em>2SO</em>4$) from hydrogen ($H<em>2$), sulfur (S), and oxygen ($O</em>2$) involves the combination of simpler elements.

  • Hydrolysis

    • A chemical reaction in which a water molecule (H₂O) is added to a substance, causing it to break down into two or more simpler compounds. It literally means “splitting with water.” This process is vital in digestion for breaking down polymers.

    • Example: The breakdown of a disaccharide (like sucrose) into two monosaccharides (glucose and fructose) via the addition of a water molecule.

  • Tautomerism / Isomeric transformation

    • A type of structural isomerism where compounds rapidly interconvert between two or more isomeric forms by the migration of a hydrogen atom and a change in the position of a double bond. This rearrangement of atoms within molecules forms a substance with different chemical properties, crucial in processes like DNA replication and mutagenesis.

  • Demethylation / Methylation

    • Methylation is the addition of a methyl group ( $-CH_3$ ) to a substrate molecule. It's significant in epigenetics (gene expression regulation), protein function, and neurotransmitter synthesis.

    • Demethylation is the removal of a methyl group from a molecule, often reversing the effects of methylation.

  • Deamination / Amination

    • Amination is the addition of an ammonia ($NH<em>3$) or an amino group ($-NH</em>2$) to a molecule.

    • Deamination is the removal of an amino group from a compound, a key step in amino acid metabolism and detoxification (e.g., conversion of amino acids to urea).

  • Decarboxylation / Carboxylation

    • Carboxylation is the addition of a carboxyl group ( $-COOH$ ) to a molecule, important in photosynthesis (CO₂ fixation) and fatty acid synthesis.

    • Decarboxylation is the removal of a carboxyl group, releasing carbon dioxide ($CO_2$). This reaction is central to several metabolic pathways, such as the citric acid cycle.

• Law of Mass Action (fundamental principle in reaction kinetics)

  • Statement: At a constant temperature, the rate of a chemical reaction is directly proportional to the product of the molar concentrations of the reacting substances, each raised to the power of its stoichiometric coefficient in the balanced chemical equation.

  • For a generic reversible reaction: aA + bB ightleftharpoons cC + dD

    • Velocity: The forward reaction velocity ($v<em>f$) depends on the product of the concentrations of reactants: $v</em>f = k<em>f[A]^a[B]^b$, where $k</em>f$ is the forward rate constant.

    • The reverse reaction velocity ($v<em>r$) depends on the product of the concentrations of products: $v</em>r = k<em>r[C]^c[D]^d$, where $k</em>r$ is the reverse rate constant.

  • Equilibrium: A state where the forward reaction speed ($v<em>f$) equals the reverse reaction speed ($v</em>r$), meaning the net change in concentrations of reactants and products is zero. At equilibrium, $K<em>{eq} = \frac{k</em>f}{k_r} = \frac{[C]^c[D]^d}{[A]^a[B]^b}$.

  • Practical implication: Changes in the concentration of reactants or products, temperature, or pressure will cause the system to shift its equilibrium position to counteract the disturbance, as described by Le Chatelier's Principle.

• Hydrogen and Hydroxyl Ion Concentration (acidity and alkalinity)

  • The concentration of free $H^+$ (hydrogen ions, often referred to as protons) or $OH^-$ (hydroxyl ions) fundamentally determines the acidity or alkalinity of an aqueous solution.

  • Hydrogen ion ($H^+$) and hydroxyl ion ($OH^-$) are central to acid-base chemistry in biochemistry, influencing enzyme activity, protein structure, and cellular processes.

  • Acid Solution

    • Contains an excess concentration of hydrogen ions ([H^+] > [OH^-]). Acids are substances that donate protons ($H^+$) in solution (Brønsted-Lowry definition).

  • Alkaline (Basic) Solution

    • Contains a lower concentration of hydrogen ions ([H^+] < [OH^-]), meaning an excess of hydroxyl ions. Bases are substances that accept protons ($H^+$) in solution.

  • pH value

    • The strength of an acid or base is dependent on its chemical structure, its ability to ionize or dissociate in a given solvent, and the solvent itself.

    • Strong acids/bases dissociate almost completely in water, while weak acids/bases only partially dissociate, establishing an equilibrium. The degree of ionization is quantified by acid dissociation constant ($K<em>a$) or base dissociation constant ($K</em>b$), often expressed as $pK<em>a$ or $pK</em>b$.

• pH (potential of Hydrogen)

  • A logarithmic measure of the hydrogen ion concentration in a solution, indicating its acidity or alkalinity defined as $pH = -log_{10}[H^+]$.

  • Neutral solution has $pH = 7$ (where $[H^+] = [OH^-] = 10^{-7} M$ at $25^\circ C$).

  • pH > 7: alkaline (basic) solution, indicating a lower $[H^+]$ concentration.

  • pH < 7: acidic solution, indicating a higher $[H^+]$ concentration.

  • Biological systems maintain a narrow physiological pH range (e.g., blood pH typically $7.35-7.45$).

  • Isoelectric pH (pI)

    • The specific pH at which a molecule (especially an amino acid, peptide, or protein) carries no net electrical charge; that is, its overall charge is zero. At this state, the substance is amphoteric and exists predominantly as a zwitterion (containing both positive and negative charges internally).

    • At its pI, the solubility of proteins is typically minimal, and they tend to precipitate.

• Buffers

  • Buffers are aqueous solutions that conspicuously resist changes in pH upon the addition of small amounts of strong acid or strong base. They are crucial for maintaining a relatively constant hydrogen ion concentration.

  • Composition: Typically consist of a weak acid and its conjugate base, or a weak base and its conjugate acid.

  • Mechanism: They counteract shifts in $[H^+]$ by neutralizing added acids or bases. When an acid is added, the conjugate base component of the buffer system neutralizes it; when a base is added, the weak acid component neutralizes it. The effective buffering range is generally within one pH unit of the $pK<em>a$ of the weak acid component, described by the Henderson-Hasselbalch equation: $pH = pK</em>a + log\frac{['conjugate\ base']}{['weak\ acid']}$.

• Buffers (summary note)

  • Buffers are absolutely essential for maintaining stable physiological pH in biological systems (e.g., the bicarbonate buffer system in blood) by dampening fluctuations in hydrogen ion concentration, thus preserving cellular function and enzyme activity.

Colloids and Colloidal Systems

• Colloids definition

  • Colloids are mixtures in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. These particles are larger than molecules in true solutions but smaller than particles in suspensions, typically having a size range of $1 nm$ to $1000 nm$ (or $1 ext{ extmu}m$).

  • They do not pass through semipermeable membranes (like parchment or cellophane).

• Colloids classification

  • Lyophilic Colloids (Emulsoids)

    • "Solvent-loving" systems where the dispersed phase has a strong affinity for the dispersion medium. They are generally more stable due to a protective hydration shell around the particles.

    • Examples: starch, egg albumin, blood proteins (like hemoglobin), soap solutions, gelatin.

  • Lyophobic Colloids (Suspensoids)

    • "Solvent-hating" systems where the dispersed phase has little or no affinity for the dispersion medium. They are less stable and often require stabilizing agents to prevent coagulation.

    • Examples: gold sol, silver sol, platinum sol (metal particles dispersed in water).

• Diffusion through membranes

  • While crystalloids (substances in true solutions) readily diffuse through semipermeable membranes, colloids do not easily pass through such membranes due to their larger particle size. This property is exploited in dialysis, a process used to separate colloids from crystalloids.

• Colloid vs. Crystalloid distinction

  • The primary distinction lies in particle size. Colloids have particle sizes between those of true solutions (crystalloids) and suspensions. While the terms are often used to differentiate, it's also possible for some substances to exist as colloids under certain conditions and crystalloids under others (e.g., soap). The size of the solute particles is the most useful differentiating criterion.

Differences: Solutions, Colloids, and Suspensions

• TRUE SOLUTION (Homogeneous Mixture)

  1. Particles are individual molecules or ions, typically with a size of < 1 nm ($10^{-3} ext{ extmu}m$).

  2. Will pass freely through both filters and semipermeable membranes.

  3. Particles are invisible to the naked eye and even under an ultramicroscope.

  4. Exhibit molecular movement (fast, random Brownian motion at a microscopic scale, but the solution appears stable).

  5. Exhibit high osmotic pressure due to the large number of individual solute particles (van 't Hoff factor is relevant).

  6. Transparent and do not scatter light (no Tyndall effect).

  7. Do not require dialysis for separation from solvent, as components freely pass through membranes.

  8. Contain a large number of particles per given volume, contributing to colligative properties.

  9. Represent the smallest particle size category among the three.

• COLLOIDAL SOLUTION (Heterogeneous Mixture / Colloidal Dispersion)

  1. Molecular aggregates or macromolecules with particle sizes ranging from approx. $1 nm - 1000 nm$ ($10^{-3} ext{ extmu}m - 1 ext{ extmu}m$).

  2. Will pass through ordinary filters but not through semipermeable membranes.

  3. Particles are ultramicroscopic; not visible to the naked eye but can be observed with an ultramicroscope using light scattering.

  4. Exhibit Brownian movement (random zigzag motion of particles), which helps in their stability against sedimentation.

  5. Exhibit low osmotic pressure compared to true solutions of similar mass concentration, as there are fewer individual entities.

  6. Exhibit the Tyndall phenomenon (scatter light, making the beam visible through the solution) due to particle size.

  7. Can be purified by dialysis (separation from crystalloids using a semipermeable membrane).

  8. Contain a moderate number of particles compared to true solutions, leading to specific optical properties (light scattering).

  9. Intermediate in particle size.

• SUSPENSION (Heterogeneous Mixture)

  1. Large molecular aggregates visible to the naked eye, with particle sizes typically > 1000 nm (> 1 ext{ extmu}m).

  2. Particles will not pass through either filters or semipermeable membranes.

  3. Macroscopic - particles are visible to the naked eye upon standing.

  4. Exhibit slow gravitational movement; particles tend to settle out over time due to gravity, often with some limited Brownian motion before settling.

  5. Exhibit virtually no osmotic pressure solely from the suspended particles, as they are too large to significantly influence solvent movement across membranes.

  6. Opaque or cloudy and scatter light very strongly.

  7. Do not require dialysis for particle separation, as gravity or simple filtration can separate them.

  8. Contain relatively few particles (in terms of number density) compared to colloids or true solutions.

  9. Represent the largest particle size category.

Laboratory Equipment: Burettes

• Types of burette used in the lab

  • Volumetric burette (glass)

    • The traditional, most common type made of glass, featuring a long, graduated tube with a stopcock at the bottom. Used for highly precise delivery of variable volumes of liquid, primarily in titrations. Available in various classes (e.g., Class A, Class B) denoting different levels of accuracy.

  • Piston / Digital burette

    • Operates similarly to a syringe but with much higher precision. It uses a plunger (piston) to dispense liquid accurately, with the volume displayed digitally. This type minimizes human error in reading the meniscus and is often attached to a reservoir bottle.

  • Electric / Electronic burette

    • An advanced version of the digital burette, often motorized to control the piston movement, allowing for even more precise and repeatable dispensing rates. These burettes can often be programmed for automated titrations and are valued for their accuracy and ease of use in high-throughput or sensitive applications.

Other Connected Information

• Enzymes

  • Enzymes are highly specific biological catalysts, typically proteins, that significantly accelerate the rate of biochemical reactions without being consumed in the process. They are crucial in all life processes, including digestion, where they break down complex food molecules.

• Oxygen

  • An indispensable element in biochemistry, primarily because it is vital for aerobic respiration, the metabolic process that generates the majority of ATP (energy) in living organisms. It acts as the final electron acceptor in the electron transport chain and participates in numerous other oxidation reactions.

• DE- prefix

  • The prefix "DE-" consistently denotes the removal, separation, or loss of a substance or group in chemical nomenclature and biological processes (e.g., deamination, decarboxylation, dehydration