Why can the same amino acid behave as an acid in one solution and a base in another? The answer begins with two functional groups in one molecule: a carboxylic acid group capable of donating a proton and an amino group capable of accepting one. In a suitable environment, an amino acid such as aminoethanoic acid can exist as a zwitterion containing both positive and negative centres. JC2 H2 Chemistry students who understand the proton transfers can predict the forms present in acidic and alkaline conditions instead of memorising three unexplained drawings.
For students seeking a JC2 Chemistry tutor in Hougang, H2 A-Level amino acids, peptide bonds and protein hydrolysis bring together acid–base theory, organic structure and conservation of atoms. The revised Singapore–Cambridge H2 Chemistry syllabus 9476 explicitly covers acid/base properties of amino acids, formation of proteins from α-amino acids and hydrolysis of peptide linkages. A student needs to know which structures and reactions are examinable; advanced electrophoresis or exact isoelectric-point calculations should not be confused with the stated mandatory scope.
I will use aminoethanoic acid and short dipeptides as transparent working examples, then show how to test a changed structure and write the correct ionic form. My aim is independent molecular reasoning that supports university-level curiosity without pretending JC2 Chemistry is already a biochemistry degree. eduKateSG’s three-student lessons are based at 8 Fourth Avenue near Sixth Avenue MRT, not in Hougang.
What the H2 Chemistry 9476 syllabus says
The 2027 official SEAB 9476 syllabus treats amino acids within nitrogen compounds, exemplified by aminoethanoic acid, and asks students to describe their acid–base properties. Its polymers section treats proteins as condensation polymers of α-amino acids, linked by peptide or amide bonds, and their hydrolysis using aqueous acid or alkali with heat. These are rich enough to support demanding structural deductions without requiring every detail of professional protein chemistry.
This scope matters because some revision sites add sophisticated isoelectric-point calculations, electrophoresis experiments and named biological structures. They can be stimulating enrichment, but their absence from the particular 9476 learning outcomes means a JC2 student should not assume they are compulsory direct-recall tasks. Begin with what the official syllabus requires, then explore the wider scientific context when time and readiness permit.
An amino acid contains two acid–base sites
A simple α-amino acid can be represented generically as H₂N–CH(R)–COOH, with amino and carboxyl groups attached to the same central carbon. The carboxyl group can lose H⁺, while the nitrogen lone pair on the amino group can accept H⁺. These are distinct transformations governed by Brønsted–Lowry acid–base reasoning, and the same molecule contains both sites. That is the molecular basis of its amphoteric behaviour.
Students often learn ‘amino acids are amphoteric’ as an isolated definition but cannot name the groups responsible. Require them to circle the –NH₂ and –COOH groups on a structural formula, draw a proton donated from one and another proton accepted by the other, and check resulting charges. This physical explanation is more durable than a memorised label.
Aminoethanoic acid is the simplest worked example
Aminoethanoic acid, also called glycine, has the connectivity H₂N–CH₂–COOH in its uncharged molecular representation and molecular formula C₂H₅NO₂. Its central carbon carries two hydrogen atoms, making it a useful example without additional side-chain acid–base behaviour. The molecular formula should not change when the same amino acid is redrawn in its zwitterionic form; a proton has changed location, not been added or removed from the whole system.
If students produce H₂N–CH₃–COOH without checking carbon valence, the structure is incorrect. Carbon must have four bonds and the proper number of hydrogen atoms. A good tutor asks for the atom inventory first, then moves to acid–base forms. Structural accuracy is the foundation for every later inference.
What a zwitterion means
A zwitterion contains at least one formally positively charged and one formally negatively charged group within the same overall molecule, with possible zero net charge. In the familiar aminoethanoic acid form, H₃N⁺–CH₂–COO⁻, nitrogen bears a positive charge and the carboxylate group a negative charge. The two charges balance, but the structure is not identical to a molecule with no charged centres. This representation is especially useful for reasoning about amino acids in suitable condensed-phase conditions.
Do not say that a zwitterion contains both a free external ammonium ion and a free carboxylate ion separated in solution. The charged groups belong to the same molecular framework. That difference helps explain some physical properties such as strong intermolecular electrostatic interactions in the solid state. A chemical drawing should keep the groups connected.
Proton transfer can occur within the amino acid framework
The neutral structural representation H₂N–CH₂–COOH and the zwitterionic representation H₃N⁺–CH₂–COO⁻ illustrate proton transfer from the acidic carboxyl group toward the basic amino group. Under appropriate aqueous or solid-state conditions the ionic representation can be particularly useful. However, this does not mean every amino acid exists exclusively as a single form at every possible pH or solvent condition.
The correct model depends on the environment. In a strongly acidic solution, protonated forms are favoured; in strongly alkaline solution, deprotonated forms become important. Rather than draw one permanently fixed charge assignment, ask which sites can accept or lose a proton and how the stated acid–base conditions affect that equilibrium.
A strongly acidic environment favours a cationic form
In the simple acid–base description of glycine under sufficiently acidic conditions, the amino group is protonated and the carboxyl group can remain as –COOH. The species is H₃N⁺–CH₂–COOH with net charge +1. This is a cation rather than a neutral zwitterion. The precise distribution of forms is governed by acid dissociation equilibria and actual pH, but the limiting strongly acidic form follows straightforward proton-transfer logic.
Students sometimes write both H₃N⁺ and COO⁻ under every condition because that diagram appears on the textbook’s opening page. A correct exam response must use the acid conditions as part of the evidence. Ask which group is protonated and verify the total charge on the drawn species before describing it as positive.
A strongly alkaline environment favours an anionic form
In sufficiently alkaline conditions, the carboxyl group of glycine is deprotonated as COO⁻, while the ammonium group can lose H⁺ to give –NH₂. The simple limiting anionic representation is H₂N–CH₂–COO⁻ with net charge −1. It is not correct to preserve –NH₃⁺ automatically if the problem describes strongly basic conditions and asks for the dominant limiting species.
The important conceptual movement is proton donation from the ammonium site to a base, or proton acceptance by the amino group under opposite conditions. Mark the starting and ending charges. A student who can derive these forms from the two functional groups no longer needs to guess which textbook sketch matches the pH prompt.
The intermediate zwitterionic representation
Between strongly acidic and strongly basic limits, H₃N⁺–CH₂–COO⁻ is an important representation of glycine under appropriate conditions. It has overall zero charge but two charged groups. A diagram of this form must show nitrogen with four bonds when protonated and the correct negative carboxylate charge. It should not be confused with a completely neutral uncharged formula merely because their net charges are both zero.
The actual equilibrium mixture depends on acid dissociation constants, solvent and pH, so an exam answer should not claim the zwitterionic form has exactly 100% abundance under every intermediate condition. The syllabus-level goal is to recognise acid–base behaviour and write chemically valid structures.
Amphoteric is not the same as always neutral
An amphoteric species is able to behave as an acid or base in suitable reactions. That is a behavioural classification, not a promise that its net electric charge remains zero. Glycine illustrates the point: it can have a cationic form in strongly acidic solution, a zwitterionic form under appropriate conditions, and an anionic form in strongly alkaline solution. The capability to donate and accept protons remains relevant across these environments.
Students who say ‘amphoteric means it is neither an acid nor a base’ have reversed the concept. It means the material can display both types of acid–base behaviour. The correct response identifies the functional group that donates a proton in one reaction and the group that accepts one in another.
Brønsted–Lowry acid and base roles
When an amino acid’s carboxyl group loses H⁺, it acts as a Brønsted acid at that site. When the nitrogen lone pair accepts H⁺, it acts as a Brønsted base at the amino site. These processes can be represented with conjugate acid–base relationships. Proton transfer, not merely a colour change in solution, is the chemical event defining the roles.
Students can practise by drawing the three simple glycine forms and adding arrows labelled ‘gain one H⁺’ or ‘lose one H⁺’ in the appropriate direction. Then check changes in overall charge. The correct logic can be transferred to other α-amino acids with different side groups, while recognising that additional ionisable side chains may complicate their full acid–base behaviour.
Zwitterions and physical properties
In a solid amino acid, the existence of ionic centres can help explain relatively strong interactions between neighbouring particles, and hence physical properties that differ from those of a small neutral organic molecule of similar relative molecular mass. Such an explanation should refer to the actual charge distribution and intermolecular electrostatic effects, not simply the presence of the word protein.
Do not claim that every amino acid must have an identical melting point or dissolve to exactly the same extent. Side groups and crystal structures matter. A scientifically careful comparison specifies which amino acids are being considered and what property is measured. The zwitterionic model supports an explanation, but it does not uniquely determine all bulk properties.
How peptide bonds form
Amino acids can form amide or peptide linkages through condensation involving a carboxyl group on one unit and an amino group on another. In an idealised direct condensation, a water molecule is removed and an –C(=O)–NH– link connects the residues. Repeating such connections forms polypeptides and proteins. The important chemical event is the formation of the amide bond, not simply two molecules touching.
A common drawing error is to connect the two central α-carbon atoms directly while leaving both functional groups unchanged. That gives the wrong polymer backbone. Show exactly where the carbonyl carbon and amino nitrogen become connected, then check the atoms removed as water.
Worked example: a glycine dipeptide
Two glycine molecules can form the simple dipeptide H₂N–CH₂–C(=O)–NH–CH₂–COOH through condensation with loss of one H₂O in the corresponding idealised reaction. Starting from two C₂H₅NO₂ units gives C₄H₁₀N₂O₄ before condensation; subtracting H₂O yields the dipeptide formula C₄H₈N₂O₃. The arithmetic checks the drawn structure.
Do not assume the final peptide contains no functional groups at its ends. The illustrated dipeptide retains a terminal amino group and a terminal carboxyl group that can have acid–base behaviour. The internal –CONH– linkage is an amide and should not be mistaken for an unbound amine nitrogen of the same basicity.
How two different amino acids create directional sequences
When two different α-amino acids are linked, the direction and order of residues can matter. A dipeptide composed of residue A followed by residue B need not be the same sequence as B followed by A, even if the overall molecular formula is identical. The backbone has a direction from the amino terminus toward the carboxyl terminus under the customary representation.
For a school-level task, label the terminal –NH₂ and –COOH groups and circle the peptide bond. Then change the order of two distinct side groups and ask whether connectivity is identical. The exercise shows why a protein cannot be fully understood from the list of amino acid ingredients alone; sequence is part of the molecular structure.
Peptide bond versus amine nitrogen
The nitrogen in a peptide bond belongs to an amide group. Its lone pair is delocalised in relation to the neighbouring carbonyl, making its acid–base behaviour different from that of an ordinary amine nitrogen. A student who treats every N atom in a polypeptide as an equally available base will overgeneralise. The chemical neighbourhood of the nitrogen determines its electron-pair availability.
This distinction also links the polymers syllabus to the H2 nitrogen-compound chapter, which discusses amide neutrality and the effect of lone-pair delocalisation. The learner should identify the –C(=O)–NH– fragment before assigning its properties, rather than classify atoms by element name alone.
Hydrolysis reverses a peptide linkage
Under appropriate acidic or alkaline aqueous conditions with heat, peptide or amide bonds can be hydrolysed. Water-related species participate in breaking the bond and restoring amino-acid-derived functional groups. The final protonation states depend on the medium: strongly acidic hydrolysis can produce protonated amino groups, whereas alkaline hydrolysis commonly yields carboxylate salts. A diagram that ignores the specified reagent may have the right carbon skeleton but the wrong ionic products.
The core H2 task is to recognise which bond is broken and which fragments are obtained. Do not treat peptide hydrolysis as destruction of the entire carbon skeleton or as simple physical dissolving. It is a chemical transformation of the amide linkage under suitable conditions.
Acid hydrolysis: pay attention to ammonium groups
When an amide or peptide is hydrolysed in an acidic environment, proton transfer can affect the amine-containing fragments. A simple carboxylic acid product may appear in its protonated form, and amino groups can be represented as ammonium species under sufficiently acidic conditions. The exact structural answer should match the problem’s specified reagent and whether neutralisation has subsequently been performed.
To practise, take a short glycine dipeptide and mark the amide bond to be cleaved. Then write the derived glycine units and choose their acid–base form using the stated environment. The chemistry is a combination of hydrolysis and protonation, not a blind rule that all products must be completely uncharged.
Alkaline hydrolysis: carboxylates matter
Under hot aqueous alkali, hydrolysis of suitable amide linkages produces carboxylate-containing products under the relevant conditions. The –COOH group may therefore be represented as –COO⁻ with a corresponding counter-ion rather than only the free acid. Students who repeatedly draw the acid after specifying excess NaOH have ignored acid–base chemistry even if the peptide bond was correctly cut.
A useful follow-up changes the final step: acidify the alkaline hydrolysis mixture and consider how the ionic representation changes. This tests whether the learner understands the effect of treatment conditions, rather than memorises a fixed product drawing.
Proteins are macromolecules, not just big amino acids
A protein is a polypeptide or assembly of polypeptides with many amino-acid residues linked through peptide bonds and capable of complex structures and biological functions. H2 9476 treats proteins as condensation polymers of α-amino acids and their hydrolysis. It does not require a full university treatment of every level of protein folding to explain the basic condensation chemistry.
Students sometimes draw a protein by simply placing amino acid molecules side by side with gaps. The backbone must show covalent peptide connections; its repeat-like structure carries side groups. The essential skill is recognising the chemical link and what happens when it is formed or hydrolysed.
Why the side group R matters
In the general α-amino acid structure H₂N–CH(R)–COOH, R identifies the side chain. Glycine has R=H, while another amino acid might contain an alkyl or an additional functional group. Side groups affect physical properties, interactions and sometimes acid–base chemistry. This means the simple three-form glycine diagram is an excellent introductory model but does not exhaust the chemistry of every amino acid.
For an unfamiliar structure, locate the common amino and carboxyl groups first, then check whether the side group itself contains an additional acidic or basic site. Avoid assigning the same net charge solely because both examples are called amino acids. The question’s exact molecular structure remains authoritative.
Glycine and optical activity
Glycine’s α-carbon carries two hydrogen atoms, so it is not a stereogenic centre of the usual tetrahedral carbon type. Many other α-amino acids have four different substituents at their α-carbon and can be chiral, but not all. This distinction can connect amino-acid drawings with the H2 organic structure and stereoisomerism chapter where relevant.
Do not declare that all amino acids are optically active. Count the actual substituents around the candidate carbon. If any two are identical, that centre is not chiral by the usual four-different-groups criterion. A chemically correct answer can make this determination from the supplied structure without memorising a list of named biological molecules.
What isoelectric point means—and its syllabus boundary
In broader biochemistry, the isoelectric point is associated with conditions where the average net electric charge of an amphoteric molecule is zero. This helps explain certain separations and solution behaviours. However, the H2 9476 stated learning outcome focuses on the acid–base properties of amino acids; students should not assume a full quantitative isoelectric-point calculation or electrophoresis treatment is required merely because those topics appear in an enrichment resource.
If the exam supplies relevant equilibrium information, a student can reason from that data using syllabus principles. But the final-year revision priority is drawing valid acidic, zwitterionic and alkaline forms, justifying proton transfers and understanding condensation or hydrolysis. A clear boundary protects students from overloading their timetable.
A complete three-form checking exercise
Write three labels—strongly acidic, suitable intermediate conditions and strongly alkaline—above three blank boxes. Ask the student to draw glycine in each box and calculate its net charge. The expected limiting structures are H₃N⁺–CH₂–COOH (+1), H₃N⁺–CH₂–COO⁻ (0) and H₂N–CH₂–COO⁻ (−1), with the caveat that actual species proportions depend on equilibrium and pH.
After the drawings are checked, change the central side group and ask whether any additional proton-transfer sites appear. This exercise combines structural accuracy, ionic charge and chemical judgement. A student who can rebuild all three without notes has a stronger foundation than one who merely recognises them when printed.
How to interpret acid–base tests without running home experiments
A question might describe adding a small amount of acid to a solution containing an amino acid and ask which site is protonated. Another might specify strong alkali and ask for the structural form. These can be solved by drawing the species and tracking H⁺ transfer. There is no educational need to improvise experiments with concentrated reagents at home.
Where hands-on practical work is relevant, it belongs in a properly supervised laboratory. Paper-based tutorials can help with balanced equations, expected observations, interpretation and assessment planning, but they do not substitute for safe experimental technique. Parents should know what practical support a tuition programme actually provides.
A parent-friendly learning progress check
Ask the student to draw glycine in acidic and alkaline conditions and explain where the proton goes. Then ask them to show the peptide bond connecting two amino-acid residues and identify which bond hydrolysis would break. This takes only a few minutes and tests two important domains: acid–base behaviour and condensation chemistry. The student should provide reasons, not simply point to memorised structures.
If a learner succeeds after the tutor’s explanation but cannot reproduce the drawing a week later, the topic needs delayed retrieval practice. A useful tutor records the exact error and assigns a changed molecule. Progress is a skill retained independently, not a claim that the chapter was ‘completed’.
How a net-zero charge can hide two charged centres
The zwitterionic glycine representation H₃N⁺–CH₂–COO⁻ has one positive formal charge on nitrogen and one negative charge associated with the carboxylate group. Their algebraic sum is zero. But a neutral net charge does not mean the atoms all lack local formal charge, nor that the molecule behaves like a non-polar hydrocarbon. The distribution of charge influences intermolecular interactions and how the molecule responds to acidic or alkaline surroundings.
Ask the student to write +1 and −1 directly beside the two charged groups, then add them. This one-minute exercise is a useful remedy for a learner who identifies a zwitterion as ‘a neutral molecule with no ions’. Next, change the pH context and see whether adding or removing a proton changes the sum exactly as expected.
Amino acids and hydrochloric acid
In a strongly acidic environment, the amino group can accept a proton. For a simple neutral molecular representation of glycine, a convenient symbolic relationship is H₂N–CH₂–COOH + H⁺ → H₃N⁺–CH₂–COOH. With chloride present as a counter-ion, the product can be described as an amino-acid hydrochloride salt under suitable conditions. The important Brønsted–Lowry event is proton transfer to nitrogen.
A student who claims the amino acid acts only as an acid because it contains COOH has overlooked the basic site. Track the nitrogen lone pair and the new N–H bond. If the question supplies hydrochloric acid concentration or asks for the ionic formula, make sure the counter-ion is represented appropriately rather than leaving an electrically unbalanced salt formula.
Amino acids and sodium hydroxide
In a strongly alkaline environment, a carboxylic acid group can be deprotonated, producing a carboxylate. A simplified molecular-form reaction is H₂N–CH₂–COOH + OH⁻ → H₂N–CH₂–COO⁻ + H₂O. In an aqueous ionic environment the actual starting form may be the zwitterion, but the net effect of sufficiently strong base is still removal of the appropriate proton to form a negatively charged amino-acid-derived species.
The exam skill is to recognise which site loses H⁺ and how many hydroxide ions are consumed in the specified simplified reaction. Avoid showing hydroxide attacking a carbonyl carbon as though every acid–base question were automatically a nucleophilic acyl substitution. Name the proton transfer when that is what the question actually asks.
Strong acid and strong base are not the only possible contexts
At intermediate pH, more than one ionic form of an amino acid may coexist according to equilibrium. The dominant form depends on the relevant acid dissociation tendencies. A reader should therefore distinguish the limiting drawings used for strongly acidic and strongly alkaline conditions from the true species distribution in a real aqueous solution. The school-level diagrams are models with stated conditions, not universal pictures of a molecule at all times.
This is especially important when students overinterpret a colour indicator or a supplied pH. Unless the question provides the acid–base constants or assumptions needed for a quantitative distribution, do not invent exact percentages of protonated and deprotonated forms. It is scientifically stronger to make a justified qualitative prediction and state what further information would be required.
Counting peptide bonds from the number of residues
A linear, unbranched peptide containing n amino-acid residues has n−1 peptide bonds, assuming a single continuous chain and no additional cross-links. Thus a dipeptide has one bond, a tripeptide has two, and a linear chain of four residues has three. In an idealised condensation from free amino acids, each new peptide bond corresponds to removal of one water molecule, so the same n−1 count applies to the water molecules lost.
Students should check the chain geometry instead of memorising the formula without conditions. Branched or cyclic systems can require different accounting, and cross-links introduce further complications. The H2 teaching example is a simple linear chain. Ask the learner to draw four linked residues and circle the three –CONH– segments; the relationship then becomes obvious.
A formula check using glycine and alanine
Glycine has molecular formula C₂H₅NO₂, while alanine has formula C₃H₇NO₂. Combining one molecule of each through an idealised single peptide-bond condensation subtracts H₂O from their formula sum. The resulting dipeptide has C₅H₁₀N₂O₃. The same molecular formula applies to the two sequence orders, but their connectivities differ when glycine and alanine occupy opposite ends.
This calculation illustrates how atom conservation and organic structure reinforce one another. If the student obtains C₅H₁₂N₂O₄, they have added monomer formulas without accounting for condensation. If they remove two waters for a dipeptide, they have counted an extra bond. A short formula check is often easier than correcting an elaborate but chemically invalid structural diagram.
How to read a peptide from its N-terminus
Protein and peptide sequences are conventionally read from the amino or N-terminus toward the carboxyl or C-terminus. In a simplified two-residue structure H₂N–CH(R₁)–C(=O)–NH–CH(R₂)–COOH, R₁ belongs to the first residue and R₂ to the second. Interchanging the R groups while preserving the termini changes the sequence for two distinct residues.
A school question may ask which amino acids form the shown dipeptide and in what sequence. Do not report only the two ingredients when their order is part of the requested answer. Mark the ends before cutting the peptide bond conceptually, then identify each side-chain group with its residue. This is an accessible first lesson in why molecular connectivity matters.
The difference between a peptide bond and a hydrogen bond
A peptide bond is a covalent amide linkage –C(=O)–NH– formed during condensation. Hydrogen bonding is a non-covalent attraction that can involve suitable groups in different parts of a molecule or among molecules. Both may be important in protein chemistry, but they are not interchangeable. Hydrolysing a peptide bond involves chemical transformation; disrupting hydrogen bonds does not by itself cleave the peptide backbone.
Students sometimes say heating a protein means ‘breaking peptide bonds’ whenever it changes shape. This is not generally correct. Structural changes and covalent hydrolysis are distinct processes. The H2 core asks for protein formation and hydrolysis, so clarify exactly what reaction or condition the question states before asserting which bonds are broken.
How protonation affects a terminal group after hydrolysis
When a peptide is hydrolysed in acid, amino-bearing products may be represented in protonated ammonium forms. When hydrolysis occurs under alkaline conditions, carboxyl-bearing fragments may be shown as carboxylate salts. If the product is subsequently neutralised or isolated in another environment, its predominant acid–base form can change. The chemical skeleton produced by cleavage and the protonation state of its functional groups are related but separate questions.
An exam response can lose marks even when the correct residues are identified if the stated acid or alkali is ignored. Draw the hydrolysed fragments first and then account for the medium. Finally check charge, atoms and whether the question asks for free amino acids, salts or another specified form.
A short case study: three students, three different errors
Imagine Aisha correctly draws the zwitterion but labels it net +1 because she counts only the ammonium charge. Ben correctly names amphoteric behaviour yet cannot identify which functional group is acting as acid or base. Mira draws a good glycine dipeptide but leaves its peptide linkage as –COO–, confusing an ester with an amide. All three need targeted correction rather than another generic amino-acid summary.
Aisha should practise net-charge calculations, Ben proton-transfer diagrams, and Mira the contrast between ester and amide condensation. After feedback, each should solve a changed structure without hints and repeat the exercise after a few days. The important measure of tuition is independent transfer, not how many times the learner has listened to an explanation.
A biological chemistry connection without overreaching
Amino-acid chemistry is foundational to understanding proteins, enzymes and many biological materials. Changing a molecular side group can affect interactions in aqueous environments, while peptide bonds give a chain its covalent backbone. University biochemistry extends these ideas into folding, function, enzyme activity and regulation. Those topics are intellectually exciting, but not every specialist detail is part of the JC2 H2 examinable list.
Parents can help students explore degree programmes through current official university descriptions while keeping their immediate A-Level workload realistic. A meaningful scientific career starts with the habits visible in this chapter: naming functional groups accurately, conserving atoms, relating structure to behaviour and correcting a claim when new evidence appears.
A seven-session amino-acid revision route
Session one identifies amino and carboxyl groups; session two builds the acidic, zwitterionic and alkaline glycine representations. Session three practices net charges and proton transfer. Session four constructs dipeptides and checks molecular formulas. Session five considers sequence direction and peptide bond counting. Session six treats acid and alkaline hydrolysis products. Session seven mixes unfamiliar structures and explanation prompts without chapter labels.
The order is suggested, not compulsory, and can be spread over two weeks for students balancing other subjects. Every session should end with one changed question and a delayed retest. If the student understands the original glycine example but fails as soon as the side group changes, revisit the structural reasoning rather than adding another long reaction list.
Frequently asked questions about amino acids
Why are amino acids amphoteric? They contain sites that can donate and accept protons under suitable conditions. Is a zwitterion uncharged at every atom? No; it has opposing charged centres, even if its net charge is zero. What is glycine’s net charge in strongly acidic solution? The simple limiting protonated form is +1. What about strongly alkaline solution? The simple deprotonated form is −1.
What is a peptide bond? An amide link between amino-acid residues. Does hydrolysis merely dissolve a protein? No; it chemically cleaves peptide bonds under appropriate conditions. Do all amino acids have a chiral α-carbon? No; glycine is a counterexample. Must I learn detailed electrophoresis and isoelectric calculations for 9476? Do not infer that from enrichment notes; check the explicit syllabus outcomes.
Continue learning and ask about JC2 tutorials
For connected learning, read JC2 H2 nitrogen compounds and amino acids, polymers, proteins and hydrolysis, acid–base theories and the official 2027 H2 Chemistry 9476 syllabus. Together these connect molecular structure with quantitative and conceptual exam skills.
For JC2 H2 Chemistry group enquiries, contact eduKate Singapore or ask about current placements. Confirm fees, lesson times and travel. The worked structures and prompts are original teaching examples rather than official examination marking schemes.