Many motile organisms exhibit “fight or flight” responses in order to survive and reproduce. Aggressive posturing and combative behavior are important for the reproductive success and the formation of pack hierarchies of some species. Submissive actions and retreats permit other species the ability to evade capture or danger and enhance survival capabilities. Scientists have debated about the mechanics and moderation of these behaviors within organisms. Two studies regarding this behavior were performed.

Study 1

Researchers decided to study crayfish, a type of freshwater arthropod, in an aquarium. They placed two crayfish opposing one another in an enclosed space. The crayfish were divided by an opaque screen that inhibited their ability to notice one another. The screen was lifted and the crayfish were permitted to interact with one another. The scientists observed their interactions and noted the crayfish's submissive and aggressive behaviors. The scientists noticed that more dominant and aggressive behaviors correlated with larger sized individuals. Their observations indicate that large size and aggression are traits actively selected for within the crayfish population and are necessary for survivorship and reproductive success.

Study 2

Researchers in this study suggest that aggressive behaviors are linked to chemical messengers. They attempted to alter the crayfish’s lateral giant escape reaction through chemical manipulation. They injected crayfish with serotonin, an aggression stimulant, and octopamine, a natural facilitator of the flight response. They monitored and recorded the crayfish’s response to aggressive stimuli (see Figure 1). The researchers concluded that the crayfish escape response is significantly different in the chemical trials in comparison to the control trial that observed the injection of an inert saline solution into the arthropods.

In Study 2, what time interval does the effect of serotonin begin to wear off?

Many motile organisms exhibit “fight or flight” responses in order to survive and reproduce. Aggressive posturing and combative behavior are important for the reproductive success and the formation of pack hierarchies of some species. Submissive actions and retreats permit other species the ability to evade capture or danger and enhance survival capabilities. Scientists have debated about the mechanics and moderation of these behaviors within organisms. Two studies regarding this behavior were performed.

Study 1

Researchers decided to study crayfish, a type of freshwater arthropod, in an aquarium. They placed two crayfish opposing one another in an enclosed space. The crayfish were divided by an opaque screen that inhibited their ability to notice one another. The screen was lifted and the crayfish were permitted to interact with one another. The scientists observed their interactions and noted the crayfish's submissive and aggressive behaviors. The scientists noticed that more dominant and aggressive behaviors correlated with larger sized individuals. Their observations indicate that large size and aggression are traits actively selected for within the crayfish population and are necessary for survivorship and reproductive success.

Study 2

Researchers in this study suggest that aggressive behaviors are linked to chemical messengers. They attempted to alter the crayfish’s lateral giant escape reaction through chemical manipulation. They injected crayfish with serotonin, an aggression stimulant, and octopamine, a natural facilitator of the flight response. They monitored and recorded the crayfish’s response to aggressive stimuli (see Figure 1). The researchers concluded that the crayfish escape response is significantly different in the chemical trials in comparison to the control trial that observed the injection of an inert saline solution into the arthropods.

Figure 1

In Study 2, what time interval does the effect of octopamine begin to wear off?

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria. 

Figure 1

A doctor prescribes that a patient take penicillin for five days in order to control his E. coli infection. Is the doctor correct in his logic? 

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria. 

Figure 1

In Study 2, what was the general trend in bacterial population for the bacteria exposed to ampicillin?

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria. 

Figure 1

In Study 2, which bacterial culture developed resistance to the antibiotic it was administered over the 15-day trial?

Bacterial resistance is a common issue encountered in various infections. Scientists have attributed this phenomenon to the overuse of anti-bacterial sanitizers and prescription antibiotics. Two groups of researchers performed studies to test bacterial resistance.

Study 1

Researchers in this study state that bacterial resistance is the result of bacterial plasmid translocation. Bacteria carry their genes on circular rings of bacterial DNA and on small, physically separate molecules known as plasmids. Plasmids are unique because they are replicons that are capable of replication autonomously within a suitable host. Researchers radioactively marked plasmids in bacterial specimens and noted that they could be easily transmitted from one bacterium to another via horizontal gene transfer. They then observed that the genes transferred from the plasmid could be incorporated into the bacteria’s genetic makeup. These genetic alterations enhanced survivorship within the environment and promoted resistance to antibiotics. They concluded that plasmids carry genes important for survival and facilitate bacterial resistance to antibiotics.

Study 2

Researchers in this study state that resistance is the result of the misuse of antibiotics. Researchers administered various antibiotics to a culture of E. coli and studied their effects over time (Figure 1). They concluded that bacterial resistance is the result of natural selection. In other words, the strongest bacteria survive antibiotics and reproduce, which produces anitbiotic-resistant offspring bacteria. 

Figure 1

How many bacteria were present at the start of each trial in Study 2?

Amino acids, when strung together in extensive chains, serve as the building blocks of muscles and proteins. At around 37ºC, these amino acid chains allow the body to carry out both macroscopic processes, like moving arms and legs, and microscopic processes, like increasing the rate of chemical reactions. A special class of proteins called enzymes assists in combining reactants to produce products by speeding up the rate of a reaction in one of three ways.

The first way enzymes increase reaction rate is by lowering the activation energy of a reaction. This is done by balancing positively charged amino acids with negatively charged amino acids, creating an electrically neutral environment. This process is called electrostatic interaction. Another way enzymes increase reaction rate is through the use of non-charged amino acids, such as valine and isoleucine, in a process called Van der Waals interactions. In Van der Waals interactions, the non-charged amino acids become temporarily polarized, similar to the permanent polarity of positively and negatively charged amino acids. This interaction brings non-charged amino acids together to stabilize the reactants. The final way enzymes increase reaction rates is by sharing the electrons in its hydrogen atoms with nitrogen, oxygen, or fluorine on the reactant molecules to trap them at the active site. The active site is the part of an enzyme where molecules bind and undergo a chemical reaction.

Enzymes are designed to work in specific parts of the body depending on their functions. For example, an enzyme in the stomach responsible for breaking down food would work most effectively at low pH while an enzyme in the small intestine responsible for absorbing food would work most effectively at high pH. Some enzymes, such as those that function in the blood, work best at intermediate pH. Some enzymes function better at lower temperatures while others require higher temperatures. All enzymes have exponential relationships between their rates of reactions and both pH and temperature, meaning that they function best in narrow pH and temperature windows. Graphs of four enzymes and their rates of reaction at various pH levels and temperature are presented below.

Glycine is a small amino acid with no positive or negative charge, no potential to be temporarily polarized, and does not contain chemical side chains with excess hydrogens. Glycine could participate as an effective enzyme by the process of __________.

Amino acids, when strung together in extensive chains, serve as the building blocks of muscles and proteins. At around 37ºC, these amino acid chains allow the body to carry out both macroscopic processes, like moving arms and legs, and microscopic processes, like increasing the rate of chemical reactions. A special class of proteins called enzymes assists in combining reactants to produce products by speeding up the rate of a reaction in one of three ways.

The first way enzymes increase reaction rate is by lowering the activation energy of a reaction. This is done by balancing positively charged amino acids with negatively charged amino acids, creating an electrically neutral environment. This process is called electrostatic interaction. Another way enzymes increase reaction rate is through the use of non-charged amino acids, such as valine and isoleucine, in a process called Van der Waals interactions. In Van der Waals interactions, the non-charged amino acids become temporarily polarized, similar to the permanent polarity of positively and negatively charged amino acids. This interaction brings non-charged amino acids together to stabilize the reactants. The final way enzymes increase reaction rates is by sharing the electrons in its hydrogen atoms with nitrogen, oxygen, or fluorine on the reactant molecules to trap them at the active site. The active site is the part of an enzyme where molecules bind and undergo a chemical reaction.

Enzymes are designed to work in specific parts of the body depending on their functions. For example, an enzyme in the stomach responsible for breaking down food would work most effectively at low pH while an enzyme in the small intestine responsible for absorbing food would work most effectively at high pH. Some enzymes, such as those that function in the blood, work best at intermediate pH. Some enzymes function better at lower temperatures while others require higher temperatures. All enzymes have exponential relationships between their rates of reactions and both pH and temperature, meaning that they function best in narrow pH and temperature windows. Graphs of four enzymes and their rates of reaction at various pH levels and temperature are presented below.

A positively charged arginine in the enzyme active site and a negatively charged aspartate on a reactant protein interact before a chemical reaction occurs. What process is stabilizing this interaction?

Amino acids, when strung together in extensive chains, serve as the building blocks of muscles and proteins. At around 37ºC, these amino acid chains allow the body to carry out both macroscopic processes, like moving arms and legs, and microscopic processes, like increasing the rate of chemical reactions. A special class of proteins called enzymes assists in combining reactants to produce products by speeding up the rate of a reaction in one of three ways.

The first way enzymes increase reaction rate is by lowering the activation energy of a reaction. This is done by balancing positively charged amino acids with negatively charged amino acids, creating an electrically neutral environment. This process is called electrostatic interaction. Another way enzymes increase reaction rate is through the use of non-charged amino acids, such as valine and isoleucine, in a process called Van der Waals interactions. In Van der Waals interactions, the non-charged amino acids become temporarily polarized, similar to the permanent polarity of positively and negatively charged amino acids. This interaction brings non-charged amino acids together to stabilize the reactants. The final way enzymes increase reaction rates is by sharing the electrons in its hydrogen atoms with nitrogen, oxygen, or fluorine on the reactant molecules to trap them at the active site. The active site is the part of an enzyme where molecules bind and undergo a chemical reaction.

Enzymes are designed to work in specific parts of the body depending on their functions. For example, an enzyme in the stomach responsible for breaking down food would work most effectively at low pH while an enzyme in the small intestine responsible for absorbing food would work most effectively at high pH. Some enzymes, such as those that function in the blood, work best at intermediate pH. Some enzymes function better at lower temperatures while others require higher temperatures. All enzymes have exponential relationships between their rates of reactions and both pH and temperature, meaning that they function best in narrow pH and temperature windows. Graphs of four enzymes and their rates of reaction at various pH levels and temperature are presented below.

The location in an enzyme where a chemical reaction takes place is called the __________.

Amino acids, when strung together in extensive chains, serve as the building blocks of muscles and proteins. At around 37ºC, these amino acid chains allow the body to carry out both macroscopic processes, like moving arms and legs, and microscopic processes, like increasing the rate of chemical reactions. A special class of proteins called enzymes assists in combining reactants to produce products by speeding up the rate of a reaction in one of three ways.

The first way enzymes increase reaction rate is by lowering the activation energy of a reaction. This is done by balancing positively charged amino acids with negatively charged amino acids, creating an electrically neutral environment. This process is called electrostatic interaction. Another way enzymes increase reaction rate is through the use of non-charged amino acids, such as valine and isoleucine, in a process called Van der Waals interactions. In Van der Waals interactions, the non-charged amino acids become temporarily polarized, similar to the permanent polarity of positively and negatively charged amino acids. This interaction brings non-charged amino acids together to stabilize the reactants. The final way enzymes increase reaction rates is by sharing the electrons in its hydrogen atoms with nitrogen, oxygen, or fluorine on the reactant molecules to trap them at the active site. The active site is the part of an enzyme where molecules bind and undergo a chemical reaction.

Enzymes are designed to work in specific parts of the body depending on their functions. For example, an enzyme in the stomach responsible for breaking down food would work most effectively at low pH while an enzyme in the small intestine responsible for absorbing food would work most effectively at high pH. Some enzymes, such as those that function in the blood, work best at intermediate pH. Some enzymes function better at lower temperatures while others require higher temperatures. All enzymes have exponential relationships between their rates of reactions and both pH and temperature, meaning that they function best in narrow pH and temperature windows. Graphs of four enzymes and their rates of reaction at various pH levels and temperature are presented below.

According to the passage, one way an enzyme increases the rate of reaction is by __________.