unifying themes of life
Which of the following correctly orders the levels of biological organization from LARGEST to SMALLEST?
A. Ecosystem → Community → Cells → Organelles
B. Community → Ecosystem → Organism → Population
C. Organism → Population → Community → Ecosystem
D. Ecosystem → Population → Community → Tissue
A. Ecosystem → Community → Cells → Organelles
Why is water considered a polar molecule?
A. Oxygen and hydrogen share electrons equally.
B. Hydrogen completely transfers its electrons to oxygen.
C. Oxygen is more electronegative and pulls the shared electrons closer to itself.
D. Oxygen and hydrogen form nonpolar covalent bonds.
C. Oxygen is more electronegative and pulls the shared electrons closer to itself.
Which statement correctly describes the relationship between monomers and polymers?
A. Polymers are used to break monomers apart.
B. Monomers are repeating units that can be joined to form polymers.
C. Monomers are always larger than polymers.
D. Polymers cannot be broken into smaller molecules.
B. Monomers are repeating units that can be joined to form polymers.
Which structure distinguishes eukaryotic cells from prokaryotic cells?
A. Ribosomes
B. Plasma membrane
C. Organelles
D. Cytoplasm
C. Organelles
Identify and briefly describe each of the five unifying themes of life discussed in lecture.
What is the smallest unit of organization that can perform all activities required for life?
A. Cell
B. Organ
C. Organelle
D. Organism
A. Cell
Two molecules are placed in water:
Which prediction is most accurate?
A. X and Y will both interact equally with water.
B. X will interact more strongly with water because its hydroxyl groups can participate in hydrogen bonding.
C. Y will interact more strongly because C–H bonds are highly polar.
D. Neither molecule can interact with water because both contain carbon.
B. X will interact more strongly with water because its hydroxyl groups can participate in hydrogen bonding.
When a polymer is synthesized, a _____ reaction occurs and a _____ molecule is formed.
A. Hydrolysis, water
B. Hydrolysis, carbon dioxide
C. Dehydration, water
D. Dehydration, carbon dioxide
C. Dehydration, water
Which organelle contains hydrolytic enzymes that break down damaged organelles into smaller molecules?
A. Golgi apparatus
B. Lysosome
C. Mitochondrion
D. Smooth ER
B. Lysosome
Explain the difference between condensation/dehydration and hydrolysis
A condensation reaction joins smaller molecules together to form a larger molecule by forming a covalent bond and releasing water. Hydrolysis does the opposite: it uses/adds water to break a covalent bond, breaking a larger molecule into smaller molecules.
A population of zebras and a population of elephants live and interact in the same area. Together, the zebras and elephants represent which level of biological organization?
A. Population
B. Community
C. Ecosystem
D. Biosphere
B. Community
A molecule contains a long hydrocarbon chain and a phosphate group. When placed in water, the phosphate-containing region interacts with water while the hydrocarbon region avoids water. Why?
A. The phosphate group is nonpolar, while the hydrocarbon region is polar.
B. The phosphate group contains negative charges that can interact with polar water, while the hydrocarbon region contains nonpolar C–H bonds.
C. The hydrocarbon region forms hydrogen bonds with water, while the phosphate group cannot.
D. The phosphate group forms nonpolar covalent bonds with water, while the hydrocarbon region forms ionic bonds.
B. The phosphate group contains negative charges that can interact with polar water, while the hydrocarbon region contains nonpolar C–H bonds.
Two amino acids are joined together during protein synthesis. Which statement correctly describes this process?
A. Water is added and a peptide bond is broken.
B. Water is lost and a peptide bond is formed.
C. Water is lost and a glycosidic bond is formed.
D. Water is added and an ester linkage is formed.
B. Water is lost and a peptide bond is formed.
Researchers discover that a cell has lost its ability to properly oxidize fatty acids. Which organelle is MOST likely malfunctioning?
A. Lysosome
B. Peroxisome
C. Golgi apparatus
D. Rough endoplasmic reticulum
B. Peroxisome
A biological molecule contains a long hydrocarbon region made mostly of C–H bonds and a region containing a phosphate group. Predict how each region will behave when the molecule is placed in water. Explain your answer using polarity, charge, and interactions with water.
Within a population, individuals have different inherited traits. Individuals with traits better suited to their environment are more likely to survive, reproduce, and pass those traits to offspring. Which answer best explains this process?
A. It demonstrates interactions because organisms choose traits based on their environment.
B. It demonstrates evolution through natural selection because favorable inherited traits can become more common over generations.
C. It demonstrates information because all individuals within a population inherit the same traits.
D. It demonstrates organization because individual organisms evolve during their lifetimes.
B. It demonstrates evolution through natural selection because favorable inherited traits can become more common over generations.
Which of the following structures is an example of a true enantiomer?
B.
One strand of DNA has the following sequence:
5′–ACTGAAAGGCC–3′
Which sequence would be complementary to this strand?
A. 5′–TGACTTTCCGG–3′
B. 3′–TGACTTTCCGG–5′
C. 3′–ACTGAAAGGCC–5′
D. 3′–UGACUUUCCGG–5′
B. 3′–TGACTTTCCGG–5′
Researchers examine a cell with three abnormalities: it produces less ATP, cannot efficiently break down damaged organelles, and cannot properly detoxify certain substances. Which combination of organelles is MOST likely malfunctioning?
A. Mitochondria, lysosomes, and smooth ER
B. Ribosomes, Golgi apparatus, and rough ER
C. Nucleus, chloroplasts, and rough ER
D. Lysosomes, ribosomes, and Golgi apparatus
A. Mitochondria, lysosomes, and smooth ER
(ATP → mitochondria
breakdown of damaged organelles → lysosomes detoxification → smooth ER)
Briefly describe what happens at each of the four levels of protein structure: primary, secondary, tertiary, and quaternary.
Multiple neurons work together as nervous tissue, which contributes to an organism's ability to respond to its environment. Which answer correctly identifies both the levels of organization and themes represented?
A. Cell → tissue → organism; Organization and Interactions
B. Organelle → tissue → population; Information and Evolution
C. Molecule → cell → community; Energy and Matter
D. Cell → population → ecosystem; Organization and Evolution
A. Cell → tissue → organism; Organization and Interactions
A change in a biological molecule replaces a negatively charged phosphate group with a nonpolar methyl (–CH₃) group. How would this change MOST likely affect that region of the molecule when exposed to water?
A. It would interact more strongly with water because methyl groups form hydrogen bonds.
B. It would interact less strongly with water because the charged phosphate group is replaced by a nonpolar group that does not interact favorably with water.
C. It would interact equally with water because both phosphate and methyl groups contain covalent bonds.
D. It would interact less strongly with water because phosphate groups are hydrophobic and methyl groups are hydrophilic.
B. It would interact less strongly with water because the charged phosphate group is replaced by a nonpolar group that does not interact favorably with water.
In sickle cell disease, a mutation causes the amino acid glutamic acid to be replaced by valine in hemoglobin. Glutamic acid is charged/hydrophilic, while valine is nonpolar/hydrophobic. How does this substitution contribute to sickle cell disease?
A. Replacing a hydrophilic amino acid with a hydrophobic amino acid changes how hemoglobin interacts, affecting its structure and contributing to red blood cells developing a sickle shape.
B. Valine is polar, so it forms additional hydrogen bonds with water that cause red blood cells to swell into a sickle shape.
C. The substitution causes all peptide bonds in hemoglobin to break, preventing hemoglobin from forming.
D. Glutamic acid and valine have the same chemical properties, so the substitution only changes the DNA and does not affect the protein.
A. Replacing a hydrophilic amino acid with a hydrophobic amino acid changes how hemoglobin interacts, affecting its structure and contributing to red blood cells developing a sickle shape.
A cell can successfully translate a protein at the rough ER, but the protein never receives the additional modifications needed before being sent to its final destination. Which organelle is MOST likely malfunctioning?
A. Lysosome
B. Golgi apparatus
C. Mitochondrion
D. Smooth ER
B. Golgi apparatus
Methyl groups are added to cytosines within a region of DNA. Explain how this methylation affects the structure of chromatin and the expression of genes in that region.
Methylation causes the chromatin to become more compact/condensed, making the DNA less accessible to proteins needed for transcription. As a result, transcription decreases, which decreases gene expression.