exam 2 study set

According to the second law of thermodynamics, what must happen with each chemical reaction in an organism?

Each chemical reaction in an organism must increase the total entropy of the universe.

Catabolism is to anabolism as is to .

Exergonic is to endergonic.

Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, where is most of the bound cyanide likely to be localized?

Mitochondria.

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

Signal molecule.

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

Paracrine signaling.

Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released.

3, 1, 5, 2, 4

In a metabolic pathway, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect of malonic acid. What role does malonic acid play with respect to succinate dehydrogenase?

Malonic acid is a competitive inhibitor.

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because…

Intracellular receptors are present only in target cells.

Which of the following are found in plant, animal, and bacterial cells?

Ribosomes.

Which of the following would likely diffuse through the lipid bilayer of a plasma membrane most rapidly?

O2

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of substances on opposite sides of the membrane?

Ligand-gated ion channel.

A cell with a predominance of rough endoplasmic reticulum is most likely…

Producing large quantities of proteins for secretion.

What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?

The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.

The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and, therefore, abundant in liver cells?

Smooth endoplasmic reticulum.

Which of the following statements describes a key component of the induced fit hypothesis of enzyme catalysis?

Binding of substrate to the active site changes the shape of the active site of an enzyme.

Which of the following statements about enzyme function is true?

Enzymes increase the rate of chemical reactions by lowering activation energy barriers.

Which domains of life are classified as prokaryotes?

Bacteria and Archaea.

For a protein to be an integral membrane protein, it would have to be…

Amphipathic, with at least one hydrophobic region.

Which of the following statements is an important consequence of the first law of thermodynamics for a living organism?

An organism ultimately must obtain all of the necessary energy for life from its environment.

For living organisms, which of the following statements is an important consequence of the first law of thermodynamics?

The organism must ultimately obtain all the necessary energy for life from its environment.

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. Which of the following conditions is required for the target organ to respond to a particular hormone?

The target organ must have receptors that recognize and bind the hormone molecule.

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

Aggregation of bacteria that can cause cavities.

Which of the following statements describes the events of apoptosis?

The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells.

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

Ligand-gated ion channel.

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to…

Add more of the enzyme.

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?

Small ions.

A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. With respect to the enzyme that converts X to Y, substance A functions as…

An allosteric inhibitor.

What is a primary function of transcription factors?

They control gene expression.

Which of the following is an example of potential rather than kinetic energy?

A molecule of glucose.

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

It is lost to the environment.

What kinds of molecules pass through a cell membrane most easily?

Small and hydrophobic.

Which curves on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?

Curves 3 and 5.

Which of the following would be most appropriate method to observe and measure the size of ribosomes in a eukaryotic cell?

Transmission electron microscopy.

What force drives simple diffusion, and what is the energy source for active transport?

The force driving simple diffusion is a concentration gradient, while the energy source for active transport is ATP hydrolysis.

Which of the following statements is true for all exergonic reactions?

The reaction proceeds with a net release of free energy.

Which of the following statements is true of metabolism in its entirety in all organisms?

Metabolism consists of all the energy transformation reactions in an organism.

What process do white blood cells use to engulf bacteria?

Phagocytosis

If side A has 2M sucrose and 1M glucose and side B has 1M sucrose and 2M glucose, what will occur when equilibrium is reached?

The water level will be higher in side A than in side B.

What process is most likely involved in the evolution of eukaryotic cells?

Endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria

What is a regulatory mechanism in which the end product inhibits an enzyme that catalyzes an early step?

Feedback inhibition

Which process includes all the others: passive transport, transport of an ion down its electrochemical gradient, diffusion of a solute across a membrane, or osmosis?

Passive transport

Which organelle is the primary site of ATP synthesis in eukaryotic cells?

Mitochondrion

What is a major difference between prokaryotic and eukaryotic cells?

Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.

Why do unsaturated fatty acids help keep a membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

Which types of reactions would decrease entropy within a cell?

Anabolic reactions

Which line represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C

What represents the activation energy required for the enzyme-catalyzed reaction in the figure?

b

Apoptosis involves all but which of the following: lysis of the cell, cell-signaling pathways, fragmentation of the DNA, or digestion of cellular contents by scavenger cells?

Lysis of the cell

What do the dots in the space between the two structures represent?

Neurotransmitters

Which structure is common to plant and animal cells?

Mitochondrion

Which condition may be overcome by increasing the substrate concentration in an enzymatic reaction with a fixed amount of enzyme?

Competitive inhibition

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?

By binding to an allosteric site, thus changing the shape of the active site of the enzyme

Which cell would be best for studying lysosomes?

Phagocytic white blood cell

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Which structure is not part of the endomembrane system?

Chloroplast

A cell with a predominance of smooth endoplasmic reticulum is likely specialized to do what?

Synthesize large quantities of lipids

If zinc is present in the active site of an enzyme, the zinc most likely functions as what?

A cofactor necessary for enzyme activity

Which type of molecule is hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

Peripheral membrane proteins

A newly discovered unicellular organism isolated from acidic mine drainage is found to contain a cell wall, a plasma membrane, two flagella, and peroxisomes, the organism is most likely what?

A motile eukaryote