Macromolecules & Water
A researcher adds a nonpolar molecule to water and observes that it does not dissolve. Which property of water explains this result?
Water is polar and cannot form hydrogen bonds with nonpolar molecules.
Which organelle produces ATP in eukaryotic cells?
Mitochondria
Enzymes speed up reactions by
Lowering activation energy.
During which phase of mitosis do sister chromatids separate?
Anaphase
What would describes natural selection?
Individuals with advantageous traits reproduce more successfully.
A student analyzes an unknown molecule and finds carbon, hydrogen, oxygen, and nitrogen. Which macromolecule is MOST likely present?
Protein
A cell placed in a hypertonic solution will
Lose water and shrink
A toxin binds to an enzyme’s allosteric site. What type of inhibition is this?
Noncompetitive inhibition.
A heterozygous individual (Aa) produces gametes. What percent contain allele “a”?
50%
A population’s allele frequencies change after a hurricane. Which mechanism is this?
Genetic drift or known as the bottleneck effect
Bottleneck effect: a sharp reduction in population size that drastically reduces genetic diversity and alters allele frequencies in the surviving population.
A mutation replaces a hydrophobic amino acid with a hydrophilic one. What is the MOST likely effect on protein structure?
The protein folds differently because the new R group interacts with water.
Which process requires a membrane protein but no energy input?
Facilitated diffusion.
Which molecule is the final electron acceptor in cellular respiration?
Oxygen
A mutation prevents spindle fibers from attaching to kinetochores. Predict the result.
Chromosomes fail to separate properly → nondisjunction.
Two species share similar DNA sequences. What does this suggest?
They share a recent common ancestor.
A researcher heats a protein and observes that its function is lost, but peptide bonds remain intact. Which level of structure was MOST affected?
Tertiary structure (R‑group interactions disrupted, but primary structure intact).
A mutation prevents ribosomes from binding to the rough ER. Predict the effect on the cell.
Fewer proteins will be synthesized for secretion or membrane insertion.
A researcher increases substrate concentration and observes that reaction rate plateaus. What explains this?
Enzymes are saturated which means all active sites are occupied.
A researcher finds that a gene is expressed only when chromatin is loosely packed. Which modification increases expression?
Histone acetylation.
A population of birds evolves longer beaks after a drought. Which type of selection occurred?
Directional selection.
A scientist adds solute to water and measures a decrease in freezing point. Which hypothesis BEST explains this?
Solute disrupts hydrogen bonding, requiring a lower temperature for water to solidify.
A researcher blocks vesicle transport from the Golgi to the plasma membrane. Which process is directly disrupted?
Exocytosis of proteins such as hormones or neurotransmitters.
A scientist measures oxygen consumption in mitochondria. When ATP levels rise, oxygen consumption decreases. Which concept explains this?
Feedback inhibition because ATP inhibits earlier steps in respiration.
A scientist observes nondisjunction during meiosis II. Which gametes result?
Two normal gametes, one with an extra chromosome, one missing a chromosome.
Removing a top predator causes prey populations to increase dramatically. This is an example of:
A trophic cascade.