Podcast Beta
Questions and Answers
Which of the following are nitrogenous bases found in DNA?
What type of bond connects nucleotides in DNA?
What is the sugar molecule found in DNA?
Deoxyribose
Thymine is a purine base found in DNA.
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Nucleotides are linked together by ______ bonds.
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Which of the following statements about hydrogen bonds in DNA is true?
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Study Notes
DNA Structure and Replication
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Forces that Determine Macromolecular Structure
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Covalent bonds:
- Strong single and double bonds
- Short bond length (C–C = 1.54Å)
- Involve shared electrons
- High bond strength (85-175 kcal/mol)
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Non-covalent bonds:
- Weaker than covalent bonds (1–50 kcal/mol)
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Electrostatic interactions:
- Strength depends on distance and dielectric constant (polarity of the medium around the molecules)
- "Salt bridges" refer to non-covalent interactions between oppositely charged groups
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Hydrogen bonds:
- Relatively weak (1–5 kcal/mol)
- Bond length is longer than covalent bonds (around 2Å)
- Highly directional - donor is a positively charged group (like hydroxyl) and acceptor is a negatively charged group (like oxygen)
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Van der Waals interactions:
- Very weak attraction (0.5–1 kcal/mol)
- Occur due to temporary, induced dipoles (charge separation) due to fluctuating electron clouds
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The Hydrophobic Effect:
- A thermodynamic driving force
- Water is disordered, so hydrophobic surfaces make water ordered around them.
- This ordering is unfavorable, so hydrophobic surfaces tend to bury themselves together to avoid making water ordered.
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Covalent bonds:
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DNA Components
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Four nitrogenous bases:
- Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
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Five-carbon sugar (deoxyribose):
- Has a hydroxyl group on the 3' carbon
- Contains a phosphate group attached to the 5' carbon
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Phosphate group:
- At pH 7, the phosphates are negatively charged
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Four nitrogenous bases:
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Sugars:
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Deoxyribose:
- Four-carbon ring (not planar)
- Lacks an oxygen on carbon 2 (deoxy indicates the absence of oxygen)
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Deoxyribose:
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Bases:
- Purines: Adenine and guanine - have two rings
- Pyrimidines: Cytosine and thymine (DNA) - have one ring
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Nucleosides (RNA):
- A nucleoside is a nitrogenous base attached to a sugar via a glycosidic bond
- Examples:
- adenosine (A)
- guanosine (G)
- cytidine (C)
- thymidine (T)
- uridine (U)
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Nucleotides (DNA):
- Nucleotides are nucleosides with a phosphate group attached
- DNA nucleotides are called deoxynucleotides
- Phosphate group on the 5' carbon
- 3'-5' phosphodiester links:
- Connect nucleotides in a DNA strand
- Each phosphate group only has one charge in the backbone, making it less acidic.
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Description
This quiz covers the fundamental aspects of DNA structure and the replication process. It explores the forces that influence macromolecular structure, including covalent and non-covalent bonds. Test your understanding of hydrogen bonds, electrostatic interactions, and the importance of these forces in DNA's stability and function.
