Functional Groups
What is the formula for a hydroxyl group, and is it polar or nonpolar?
-OH; it is polar.
What covalent bond links monosaccharides together?
Glycosidic linkage
How do saturated and unsaturated fatty acid chains differ structurally?
Saturated fats have only single carbon-carbon bonds; unsaturated fats have one or more double carbon-carbon bonds (kinks).
What is the monomer of a protein, and which functional groups join to form a peptide bond?
Amino acid; formed between the carboxyl group (-COOH) of one and amino group (-NH2) of another.
What three components make up a nucleotide?
A 5-carbon sugar, a phosphate group, and a nitrogenous base.
Which functional group acts as an acid in water by donating H+ ions?
Carboxyl group (-COOH).
Alternate answer: phosphate group
How do alpha-glucose and beta-glucose differ in structure and function?
Alpha-glucose forms helical energy storage molecules (starch); beta-glucose forms rigid structural chains (cellulose).
Why are unsaturated fats liquid at room temperature while saturated fats are solid?
Double-bond kinks prevent unsaturated fatty acids from packing tightly together.
What is primary structure, and why is it important?
The sequence of amino acids; it dictates all higher levels of protein folding.
Give two structural differences between DNA and RNA.
DNA uses deoxyribose, thymine, and is double-stranded; RNA uses ribose, uracil, and is single-stranded.
Which functional group acts as a base in water by picking up H+ ions?
Amino group (-NH2).
How does the structure of cellulose help plant cell walls withstand water pressure?
Parallel, linear chains hydrogen-bond into rigid microfibrils.
Why do phospholipids spontaneously form a bilayer in water (think of their structure)?
Hydrophilic phosphate heads face water, while hydrophobic fatty acid tails hide on the inside.
What bonds stabilize secondary structure (alpha-helices and beta-sheets)?
Hydrogen bonds between atoms of the polypeptide backbone.
What does "antiparallel" mean in a DNA strand, and what defines the 5' and 3' ends?
Strands run in opposite directions; 5' ends with a phosphate, 3' ends with a hydroxyl group (-OH).
What role do sulfhydryl groups (-SH) play in tertiary protein structure?
They form strong covalent disulfide bridges between cysteine residues.
How do glycogen and starch differ in branching and purpose?
Glycogen is highly branched for quick glucose release in animals; starch is less branched for compact energy storage in plants.
Predict how do arctic fish modify their cell membranes to stay fluid in freezing water.
They increase the proportion of unsaturated fatty acids in their phospholipids.
Name three types of R-group interactions that maintain tertiary structure.
Hydrogen bonds, ionic bonds, hydrophobic interactions, or disulfide bridges.
To which end of a growing nucleic acid strand are new nucleotides added, and by what bond?
Added to the 3' -OH end via phosphodiester bonds.
Predict the change in pH and protein folding when a cell has an influx of methyl groups (-CH3), replacing carboxyl groups (-COOH) on amino acid side chains.
An increase in pH (due to the loss of acidic carboxyl groups) and a disruption in tertiary protein folding as nonpolar hydrophobic interactions replace polar or ionic interactions
If a plant cannot form glycosidic bonds, how are its cell walls and energy storage affected?
It cannot build cellulose for cell walls or starch for energy storage.
How do steroids and triglycerides differ in structure and biological function?
Steroids have 4 fused carbon rings (hormones/signaling); triglycerides have glycerol + 3 fatty acids (long-term energy storage).
Replacing a polar R-group with a nonpolar R-group on a protein's exterior has what effect on folding?
Hydrophobic interactions push the nonpolar group inward, misfolding the protein and lowering solubility.
If a double-stranded DNA sample is 22% Cytosine, what percentage is Thymine, AND what bonds hold complementary strands together?
What is 28% Thymine (since C=22%, G=22%, leaving 56% for A-T, so T=28%), stabilized by hydrogen bonds between bases?