Unit 1 Flashcards
What is a covalent bond?
The sharing of a pair of valence electrons by two atoms, which can be of the same or different elements. In a covalent bond, the shared electrons count as part of each atom’s valence shell. In nonpolar covalent bonds, electrons are shared equally since the electronegativity of the atoms is similar. In polar covalent bonds, electrons are drawn toward the more electronegative atom, resulting in dipoles.
What is a hydrogen bond?
A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (only Nitrogen, Oxygen, and Fluorine).
What are Van der Waals Interactions?
Electrons are not evenly distributed, and they may accumulate by chance in one part of a molecule based on their random movement, resulting in dipoles.
Van der Waals interactions are attractions between molecules that are close together as a result of these charges.
What are the four emergent properties of water?
cohesion, moderating temperature, expansion upon freezing, and solvent versatility
How does hydrogen bonding contribute to cohesion? What are the benefits of cohesion?
Hydrogen bonding holds H2O together through the attractions of opposite dipoles. Hydrogen bonds are constantly broken and reformed, so many molecules could be linked through them, which makes this liquid more structured. This gives a strong surface tension since, at the border between air and water, the surface of the water is hydrogen-bonded together but not to the air, resulting in asymmetry. The surface tension allows plants and animals to float and cohesion allows for the transfer of nutrients and water in plants.
How does hydrogen bonding contribute to moderating temperature?
Water is able to absorb heat from warm air and can release heat to cold air without a large change in the water temperature. This is because of water’s high specific heat caused by hydrogen bonding. Absorbing heat initially breaks hydrogen bonds, resulting in a low change in temperature. Since the energy is first used to break bonds before H2O moves faster and increases its thermal energy.
What are the benefits of water moderating temperature?
Water’s high specific heat allows coastal land to be heated at night and cooled during the day. The heat of vaporization allows for tropical seas to absorb heat via evaporation. This water then goes to the poles and releases heat when it condenses to rain. Evaporative cooling means that as the liquid evaporates, the surface of a liquid that remains is cool because the hottest molecules with higher KE already evaporated, which prevents overheating (sweating). This is why animals are mostly water.
How does hydrogen bonding contribute to expansion upon freezing? What are the benefits of this?
At 0 C H2O forms lattice structures that keep hydrogen bonds and molecules far enough to be less dense than H2O. If ice sank, then bodies of water could potentially freeze over. Ice also helps insulate the water underneath and keeps organisms there alive.
How does hydrogen bonding contribute to solvent versatility?
Water is a very polar molecular, which makes it a great solvent. Its charged dipoles attract the solutes and shield their polar/ionic attractions.
Describe, and rank by force of attraction, the following intermolecular bonds and forces:
Ionic
Hydrogen bonds
London forces
Ionic bonds are an attraction between a cation and anion. These bonds are formed as a result of the ions’ charges not just due to the act of a highly electronegative atom stealing electrons. Ionic bonds are the strongest of the three forces because their attractions are based on set oppositely charged ions rather than partial charges. Hydrogen bonds are the next strongest because the partial charges are not random but as a result of the electronegativities of the atoms, which allows for some consistencies. London dispersion forces are based on the random movement of electrons that may result in a temporary high density of electrons in one area that forms a dipole.
Identify and draw the following functional groups Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Methyl
Hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate are all reactive. Of these, only sulfhydryl is not hydrophilic. Methyl is used as a recognizable tag on biological molecules.
Identify the four categories of biological macromolecules.
carbohydrates, proteins, nucleic acids, and lipids
What are carbohydrates?
These include sugars and polymers of sugars.
What are monosaccharides?
the simplest carbs that builds more complex ones. These are usually a multiple of CH2O. Its trademarks are carbonyls and multiple OH groups. The size is usually 3-7 carbons long. In aqueous solution 5-6 C sugars form rings since they are the most stable. Ex. glucose
What is a disaccharide?
2 monosaccharides joined by a glycosidic linkage. These molecules must be broken down into monosaccharides to be used for energy. Ex. maltose/sucrose
What is a glycosidic linkage?
a covalent bond formed between two monosaccharides by a dehydration reaction
What are polysaccharides?
macromolecules; polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages. These serve as storage material for energy later like starch in plants and glycogen in animals. They are also used as building protective structures like chitin in exoskeletons and cellulose in plants.
Illustrate the dehydration synthesis.
Dehydration synthesis is a type of condensation reaction that connects monomer to monomer or to a polymer with covalent bonds that results in the loss of a water molecule. This synthesis is found in carbon and protein polymer formation.
Illustrate hydrolysis.
Polymers are disassembled by hydrolysis, which breaks the bonds of monomers by adding water. An H is added to one monomer and an OH is added to the other. This occurs in digestion with enzymes.
Explain the biological significance of alpha vs beta glycosidic bonds and 1-4 vs 1-6 linkages in polysaccharides.
When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha (a) and beta
(b), respectively. In starch, all the glucose monomers are on the same orientation with 1-4 links (a) In contrast, the glucose monomers of cellulose are all in the b configuration, making every glucose monomer “upside down” with respect to its neighbors.
The differing glycosidic linkages in starch and cellulose give the two molecules distinct three-dimensional shapes and therefore different functions. Certain starch molecules are largely helical, fitting their function of efficiently storing glucose units. Conversely, a cellulose molecule is straight. Cellulose is never branched, and some hydroxyl groups on its glucose monomers are free to hydrogen-bond with the hydroxyls of other cellulose molecules lying parallel to it. These cable-like microfibrils are a strong building material for plants.
Enzymes that digest starch by hydrolyzing its a linkages are unable to hydrolyze the b linkages of cellulose due to the different shapes of these two molecules.
The alpha-1,4-glycosidic bond is the more common bond and it gives glycogen a helical structure that is suitable for energy storage. The alpha-1,6-glycosidic bond bonds are found about every ten or so sugars and these create branching points.
What is a protein?
a biologically functional molecule made up of 1 or more polypeptides, each folded and coiled into a specific 3D structure.
What are the functions of proteins?
enzymatic, defensive, storage, transport, hormonal, contractile and motor, structural, and receptor proteins
What are proteins made of and how are they formed?
Proteins are composed of amino acids as their building blocks. Bonds between amino acids are peptide bonds that form polypeptides, a polymer of amino acids. A peptide bond is a covalent bond formed when two amino acids are positioned so that one carboxyl is adjacent to the amino group of another, and they become joined via a dehydration reaction.
What determines the functions of proteins?
the R groups of amino acids have different physical and chemical properties that determine the characteristics of amino acids and thus the function of the polypeptide. The R groups also determine the protein’s structure, which is how it works since it needs to recognize and bind to other molecules
Define an amino acid.
an organic molecule with amino and a carboxyl group
How are the amino acids grouped?
Amino acids are group based on the R group.
nonpolar R group- hydrophobic; Ex. R group = CH3-R
polar R group- hydrophilic; Ex. R group = OH-CH2-R
acidic group- have R groups w/ (-) charge due to carboxyl group, which is ionized at cell pH; R has COOH
basic group- have R groups with (+) charge; R has NH3+ at 7 pH
Draw the generic structure of amino acids and peptide bonds.
amino acid:
R
|
H2N-C- C=O
| |
H OH
peptide bond:
R O
| ||
H2N-C-C-N-C-C=O
| | | |
H H H OH
