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Quizzes > Science > Chemistry

Master Dipeptide Structure & Definition - Take the Quiz Now!

Put your dipeptide definition and structure of dipeptide knowledge to the test!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style dipeptide structure diagram and quiz title on sky blue background

Are you ready to dive into the structure of a dipeptide and boost your peptide chemistry skills? In this free scored quiz, put your dipeptide definition into action as you explore how two amino acids bond to form this fundamental unit. You'll review peptide bond formation, reinforce dipeptide def nuances, and confirm you've nailed the precise arrangement in the structure of dipeptide pairs. You'll also see how these units become the building blocks of larger proteins. For extra help, check out define oligopeptides or explore the peptide bond condensation reaction . Ready to shine? Take the quiz now and prove you're a peptide pro!

What is a dipeptide?
A molecule formed by two amino acids linked by a peptide bond
A molecule formed by three amino acids linked by peptide bonds
A sequence of two peptides linked together
Two amino acids interacting without a covalent bond
A dipeptide consists of exactly two amino acids joined by a single peptide bond formed between the carboxyl group of one and the amino group of the other. This linkage results from a condensation reaction where water is released. It is the simplest peptide after amino acids themselves. https://en.wikipedia.org/wiki/Peptide
Which molecule is released during the formation of a dipeptide?
Water
Carbon dioxide
Ammonia
Hydrochloric acid
Dipeptide formation is a condensation reaction in which the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water. This dehydration step is key to forming the peptide bond. https://en.wikipedia.org/wiki/Condensation_reaction
The reaction that joins two amino acids to form a dipeptide is called:
Dehydration synthesis
Hydrolysis
Oxidation
Reduction
The formation of a dipeptide from two amino acids involves dehydration synthesis, where a water molecule is removed. Hydrolysis is the reverse process where water breaks the peptide bond. Oxidation and reduction are not involved in peptide bond formation. https://en.wikipedia.org/wiki/Condensation_reaction
A peptide bond in a dipeptide forms between which functional groups?
The carboxyl group of one amino acid and the amino group of another
The carboxyl groups of both amino acids
The amino groups of both amino acids
The side chains of the amino acids
Peptide bonds form when the carboxyl (�COOH) group of one amino acid reacts with the amino (�NH2) group of the next. This bond is covalent and specifically links the carbon of the carboxyl to the nitrogen of the amino group. Side chains are not directly involved in peptide bond formation. https://en.wikipedia.org/wiki/Peptide_bond
How many water molecules are released when forming one dipeptide from two amino acids?
1
2
0
3
When two amino acids condense to form a dipeptide, exactly one molecule of water is released. Each additional peptide bond formed in longer peptides similarly releases one water molecule. https://en.wikipedia.org/wiki/Peptide_bond
Which end of a dipeptide is referred to as the N-terminus?
The end with the free amino group
The end with the free carboxyl group
The side chain of the first amino acid
The peptide bond
The N-terminus is defined by the free (unlinked) amino group of the first amino acid in the peptide chain. The opposite end, with the free carboxyl group, is called the C-terminus. https://en.wikipedia.org/wiki/Protein_terminus
At physiological pH (~7.4), what is the net charge of a dipeptide composed of two neutral side-chain amino acids?
0
+2
-1
+1
At physiological pH, the amino terminus is positively charged (+1) and the carboxyl terminus is negatively charged (�1), resulting in a net charge of zero for a dipeptide of neutral side chains. https://en.wikipedia.org/wiki/Isoelectric_point
How is the dipeptide composed of N-terminal serine and C-terminal leucine correctly named?
L-seryl-L-leucine
L-leucyl-L-serine
Serineleucine
Leucineserine
Peptide nomenclature lists the N-terminal residue first with the suffix '-yl' and the C-terminal residue as its full amino acid name, both with L-configuration if applicable. Thus, serine (N-term) becomes seryl and leucine (C-term) remains leucine. https://www.ncbi.nlm.nih.gov/books/NBK22326/
Which bond angle in the backbone of a dipeptide is referred to as the phi (?) angle?
The angle around the N�C? bond
The angle around the C?�C bond
The angle around the peptide bond (C�N)
The angle between side-chain atoms
The phi (?) angle describes rotation about the bond between the nitrogen and the ?-carbon in the peptide backbone. Psi (?) refers to the C?�C bond, and omega (?) to the peptide bond itself. https://en.wikipedia.org/wiki/Protein_dihedral_angles
Complete hydrolysis of a dipeptide yields:
Two free amino acids
One free amino acid and one peptide
A tripeptide
A single amino acid
Hydrolysis of a dipeptide cleaves the peptide bond and uses water to yield exactly two free amino acids. Partial hydrolysis can yield mixtures of peptides and amino acids. https://en.wikipedia.org/wiki/Hydrolysis
What is the typical dihedral angle ? (omega) around the peptide bond in a dipeptide?
180� (trans)
0� (cis)
90�
60�
Due to partial double-bond character from resonance, the peptide bond is planar and strongly favors the trans configuration with an ? angle of about 180�. The cis form (? ? 0�) is sterically disfavored. https://en.wikipedia.org/wiki/Peptide_bond#Planarity
Which method sequentially removes the N-terminal amino acid to determine the sequence of a dipeptide?
Edman degradation
Mass spectrometry
X-ray crystallography
NMR spectroscopy
Edman degradation chemically cleaves the N-terminal amino acid one at a time for sequence analysis, making it ideal for short peptides like dipeptides. Mass spectrometry can also sequence peptides but does not use sequential removal. https://en.wikipedia.org/wiki/Edman_degradation
In which UV wavelength range does the peptide bond show strong absorption?
190�230 nm
260�280 nm
300�320 nm
350�370 nm
The peptide bond exhibits strong ???* and n??* electronic transitions in the far-UV region, typically around 190�230 nm. This property is used in circular dichroism and protein quantification assays. https://en.wikipedia.org/wiki/Peptide_bond#UV_absorption
How many chiral centers are present in a dipeptide composed of alanine and valine?
2
3
1
4
Both alanine and valine have one chiral ?-carbon each, so a dipeptide composed of these two amino acids has two chiral centers in total. The peptide bond and side chains do not introduce additional chiral centers. https://en.wikipedia.org/wiki/Chirality_(chemistry)
Given a dipeptide Gly�Glu with pKa values: ??COOH = 2.34, side?chain COOH = 4.25, ??NH3+ = 9.60, what is its approximate isoelectric point (pI)?
3.30
5.15
7.00
6.20
The isoelectric point for a peptide with two acidic groups is the average of the two carboxyl pKa values (2.34 and 4.25), since the neutral species loses protons from these groups. Thus, pI ? (2.34 + 4.25)/2 ? 3.30. https://en.wikipedia.org/wiki/Isoelectric_point
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Study Outcomes

  1. Define dipeptide principles -

    Clarify the dipeptide definition by identifying its constituent amino acids and the chemical bond that links them.

  2. Illustrate dipeptide structure -

    Recognize and sketch the key features of a dipeptide, including N-terminus, C-terminus, and the peptide bond.

  3. Analyze peptide bond formation -

    Break down the condensation reaction mechanism that forms a dipeptide, noting reactants, products, and water release.

  4. Predict dipeptide orientation -

    Determine the sequence directionality from N-terminus to C-terminus and explain its significance in peptide chemistry.

  5. Apply structure identification skills -

    Use your understanding of the structure of dipeptide models to correctly label functional groups and bonding interactions.

  6. Evaluate side chain influence -

    Assess how different amino acid side chains affect dipeptide shape and properties, enhancing comprehension of molecular diversity.

Cheat Sheet

  1. Basic Dipeptide Definition -

    A dipeptide is composed of two α-amino acids linked by a single amide (peptide) bond through a condensation reaction that releases H₂O. This fundamental structure of a dipeptide is outlined in biochemistry texts like Lehninger Principles of Biochemistry, reinforcing the dipeptide definition.

  2. Peptide Bond Chemistry -

    The peptide bond ( - CO - NH - ) has partial double-bond character due to resonance, restricting rotation and creating a planar amide, which influences overall stability and rigidity. Use the mnemonic "Resonance Rigidifies" to recall why peptide bonds are less flexible than single C - N bonds, as described by IUPAC guidelines.

  3. Backbone Atoms & Torsion Angles -

    The backbone of a dipeptide comprises the N-terminal amine, α-carbon, carbonyl carbon, and C-terminal carboxyl, with φ and ψ torsion angles defining its conformation. Refer to Ramachandran plots in Nature Reviews Molecular Cell Biology to visualize allowable φ/ψ combinations that dictate the structure of a dipeptide.

  4. Side Chain Positioning & R Groups -

    Each amino acid's side chain (R group) projects from the α-carbon, impacting dipeptide polarity, solubility, and reactivity; for example, glycine's minimal H side chain increases flexibility while proline's cyclic R group induces conformational kinks. Remember "Gly-Flex, Pro-Kink" to quickly recall their opposite effects on backbone flexibility.

  5. N- and C-Terminal Nomenclature -

    Dipeptides are named by listing the N-terminal residue first with suffix - yl, followed by the full name of the C-terminal residue (e.g., Ala - Gly for alanine - glycine). Follow standard IUPAC conventions and consult PubChem or UniProt resources for correct systematic naming of the structure of a dipeptide.

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