Questions and Answers
What type of bonds are two hydrogen atoms bonded to a single oxygen atom in a water molecule?
polar covalent bonds
What is the attraction called between the slight negative charge at one end of one water molecule and the slight positive charge of another water molecule?
a hydrogen bond
Why does the partial negative charge in a water molecule occur?
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
What is the main consequence of liquid water's high specific heat?
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Why does ice float in liquid water?
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What happens to a strong acid like HCl in an aqueous solution?
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What element is present in all organic molecules?
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How many electron pairs does carbon share to complete its valence shell?
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Why are hydrocarbons insoluble in water?
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What determines the configuration of a carbon atom's covalent bonds?
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A compound containing predominant hydroxyl groups should dissolve in water.
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Which statement best summarizes the relationship between dehydration reactions and hydrolysis?
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What makes one amino acid different from another?
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What is required for the bonding of two amino acid molecules to form a larger molecule?
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Which statement about the 5' end of a polynucleotide strand of DNA is correct?
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Which of the following are nitrogenous bases of the pyrimidine type?
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Which of the following are nitrogenous bases of the purine type?
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If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', what would the sequence of the other complementary strand be?
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Study Notes
Water and Its Properties
- Water molecules consist of two hydrogen atoms bonded to one oxygen atom through polar covalent bonds.
- Each water molecule exhibits a slight negative charge on the oxygen end, creating an attraction to the slight positive charge of neighboring water molecules, forming hydrogen bonds.
- Electrons in water are unevenly distributed, leading to a partial negative charge around the oxygen due to electrons spending more time near the oxygen nucleus.
Physical Properties of Water
- Liquid water has a high specific heat, primarily due to the energy required to break and form hydrogen bonds.
- Ice floats in liquid water because hydrogen bonds keep ice molecules spaced further apart than in liquid water, resulting in lower density.
Acids and Organic Molecules
- Strong acids, such as hydrochloric acid (HCl), fully ionize in water, releasing protons.
- Carbon is the fundamental element found in all organic molecules, enabling diverse bonding patterns.
- Carbon shares four electron pairs to complete its valence shell.
Hydrocarbons and Their Properties
- Hydrocarbons are insoluble in water due to the predominance of nonpolar covalent carbon-to-hydrogen bonds.
Carbon Bonding Configuration
- The bonding shape around carbon atoms can be tetrahedral or planar, depending on the presence of double bonds with other atoms.
Functional Groups and Solubility
- Compounds with predominant hydroxyl groups are typically soluble in water due to their ability to form hydrogen bonds with water molecules.
Macromolecule Reactions
- Dehydration reactions synthesize polymers by removing water, while hydrolysis breaks polymers down by adding water.
- There are 20 unique amino acids, differentiated by the various side chains (R groups) linked to an α carbon.
Amino Acids and Peptide Bonds
- Forming a larger molecule from two amino acids necessitates the removal of a water molecule.
Nucleic Acids Structure
- The 5' end of a DNA polynucleotide strand is characterized by a phosphate group attached to the fifth carbon of ribose.
- Pyrimidine nitrogenous bases include cytosine and uracil,
- Purine nitrogenous bases include guanine and adenine.
DNA Base Pairing
- In a DNA molecule, if one strand has the sequence 5'ATTGCA3', the complementary strand will read 5'TAACGT3'.
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