A buffer is made with equal concentrations of acetic acid (pKa = 4.76) and sodium acetate. What is the pH of the buffer?
4.76 By the Henderson-Hasselbalch equation, pH = pKa + log([A⁻]/[HA]). When the acid and its conjugate base are equal, the ratio is 1 and log 1 = 0, so the pH equals the pKa: 4.76.
Which of the following lowers the activation energy of a chemical reaction?
Adding a catalyst A catalyst gives the reaction a different pathway with a lower activation energy, so more collisions have enough energy to react. It speeds up the forward and reverse reactions equally and is not used up.
A carboxylic acid is heated with an alcohol in the presence of a strong acid catalyst. Which functional group is formed?
An ester This is Fischer esterification. The alcohol attacks the carbonyl carbon of the acid, water is lost, and an ester (R-COO-R′) forms. The acid catalyst makes the carbonyl carbon more electrophilic.
Blood flows steadily through a vessel into a narrowed section whose cross-sectional area is half the original. Treating blood as an incompressible fluid, how does its speed in the narrowed section compare with its speed before?
It is twice as fast The continuity equation says A₁v₁ = A₂v₂ for an incompressible fluid in steady flow. If the area halves, the speed must double so the same volume passes each point every second.
Two 6 Ω resistors are connected in parallel across a battery. What is their equivalent resistance?
3 Ω For resistors in parallel, 1/R = 1/R₁ + 1/R₂ = 1/6 + 1/6 = 1/3, so R = 3 Ω. Adding a parallel path always lowers the total resistance.
Critics often dismiss translated poetry as a pale copy of the original. On this view, whatever is lost in moving from one language to another (rhythm, rhyme, the echo of one word inside another) is the poem itself, and the translator can offer only a summary. Yet this complaint assumes that a poem has one fixed form that can be preserved or destroyed. Readers of a poem in its first language already disagree about its sound and sense; each reading is, in a way, a translation. A good translator does not copy a poem but makes a new one that answers the old. Judged that way, translation is less a loss than a continuation.
The author’s main purpose in the passage is to:
argue that translated poems should be judged as new works that respond to the original. The author states the critics’ view, questions its assumption, and ends with their own claim: a good translation is a new poem that answers the old one, “less a loss than a continuation.” Everything builds toward that point.
Critics often dismiss translated poetry as a pale copy of the original. On this view, whatever is lost in moving from one language to another (rhythm, rhyme, the echo of one word inside another) is the poem itself, and the translator can offer only a summary. Yet this complaint assumes that a poem has one fixed form that can be preserved or destroyed. Readers of a poem in its first language already disagree about its sound and sense; each reading is, in a way, a translation. A good translator does not copy a poem but makes a new one that answers the old. Judged that way, translation is less a loss than a continuation.
Which of the following findings, if true, would most weaken the author’s argument?
Native readers of a poem almost always agree closely on how it should sound and what it means. The author’s case rests on the claim that native readers already disagree, so a poem has no single fixed form. If native readers nearly always agree, that support collapses, and the critics’ idea of one fixed original looks stronger.
Before the railways, every town kept its own time. Noon was when the sun stood highest over the local church, so a clock in one town might run several minutes ahead of a clock forty miles to the west. No one minded, because no one traveled fast enough to notice. The railways changed that. A timetable that listed dozens of local times invited missed trains and, worse, collisions on shared track. Railway companies began to run on a single standard time, and towns gradually followed. What had been a fact of nature, read from the sky, became a matter of agreement, set by people who needed their schedules to match.
According to the passage, towns kept different times before the railways because:
each town set noon by when the sun was highest over that town. The passage says noon was “when the sun stood highest over the local church.” The sun reaches its highest point at different moments in different places, so towns to the east and west kept slightly different times.
Before the railways, every town kept its own time. Noon was when the sun stood highest over the local church, so a clock in one town might run several minutes ahead of a clock forty miles to the west. No one minded, because no one traveled fast enough to notice. The railways changed that. A timetable that listed dozens of local times invited missed trains and, worse, collisions on shared track. Railway companies began to run on a single standard time, and towns gradually followed. What had been a fact of nature, read from the sky, became a matter of agreement, set by people who needed their schedules to match.
The author’s statement that time became “a matter of agreement” most strongly suggests that:
the way people keep time can change when their practical needs change. The passage links the change in timekeeping to a new need: trains had to run on matching schedules. Calling time “a matter of agreement” stresses that people chose a shared standard because it served them.
Some of the most useful records in ecology were kept by people who were not scientists. Farmers noted the date of the first frost; birdwatchers wrote down when the swallows returned. None of them set out to study climate. But because they wrote the same thing in the same place year after year, their notebooks now let researchers see changes that no single season could show. The value of such records lies less in the skill of the observer than in the patience of the habit.
Based on the passage, which of the following would the author most likely consider the most valuable record?
A gardener’s notes on the day her lilac first blooms, kept every spring for forty years The author values records kept the same way, in the same place, over many years, more than expert skill. The gardener’s forty years of bloom dates match that description exactly.
A globular protein folds in water. Which amino acid side chain is most likely to be found buried in the protein’s interior?
Leucine Leucine has a nonpolar, hydrophobic side chain. In water, hydrophobic side chains cluster in the protein’s core, away from water, which is a major driving force of folding.
A competitive inhibitor is added to an enzyme-catalyzed reaction. Compared with the reaction without inhibitor, what happens to the apparent Km and Vmax?
Km increases; Vmax is unchanged A competitive inhibitor binds the active site and competes with the substrate. More substrate is needed to reach half of Vmax, so apparent Km rises. At very high substrate the inhibitor is outcompeted, so Vmax stays the same.
During DNA replication, to which end of a growing DNA strand does DNA polymerase add new nucleotides?
The 3′ end DNA polymerase can only add nucleotides to a free 3′-OH group, so new DNA is always built in the 5′ to 3′ direction. This is true on both the leading and the lagging strand.
After a high-carbohydrate meal, blood glucose rises. Which hormone released by the pancreas acts to bring blood glucose back down?
Insulin Beta cells of the pancreatic islets release insulin when blood glucose rises. Insulin helps cells such as muscle and fat take up glucose and promotes glycogen storage in the liver, lowering blood glucose.
Two parents are both carriers (heterozygous) for an autosomal recessive disorder. What is the probability that their first child will have the disorder?
1/4 Each parent is Aa. A Punnett square gives AA, Aa, Aa and aa. Only aa shows a recessive disorder, so the chance is 1 in 4.
A child gets a sticker each time she cleans her room, and over the next few weeks she cleans her room more often. Which learning process does this best show?
Positive reinforcement Something pleasant (a sticker) is added after the behavior, and the behavior becomes more frequent. In operant conditioning, adding a stimulus that increases a behavior is positive reinforcement.
In the human eye, where are the rods and cones that turn light into neural signals located?
The retina Rods and cones are photoreceptors in the retina, the layer at the back of the eye. They convert light into electrical signals that travel through the optic nerve to the brain.
A child watches water poured from a short, wide glass into a tall, thin one and correctly says the amount of water is the same. According to Piaget, the child has mastered:
conservation. Conservation is understanding that a quantity stays the same when its shape or appearance changes. Piaget linked it to the concrete operational stage, around ages 7 to 11.
Which term describes the lifelong process through which people learn the norms, values and behaviors expected in their society?
Socialization Socialization is how people learn and take on the norms, values and roles of their society. Family, schools, peers and media are common agents of socialization.
Which of the following is an example of upward intergenerational mobility?
A woman whose parents worked in a factory becomes a surgeon. Intergenerational mobility compares a person’s social position with their parents’. Moving from a working-class family to a high-status profession is upward mobility across generations.
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