unit 5 LC&MB

d) endergonic

A chemical reaction that has a positive ΔG is best described as _____. a) spontaneous b) exergonic c) enthalpic d) endergonic

an allosteric inhibitor

A series of enzymes catalyze the reaction 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 _____.

as

A series of enzymes catalyze the reaction 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. What is substance X?

radiation

A woman standing and watching the stars on a cool, calm night will lose most of her body heat by _____.

the binding of the substrate changes the shape of the enzyme's active site

According to the induced fit hypothesis of enzyme catalysis, _____.

most of their cells in contact with an aqueous medium

All animals, whether large or small, have _____.

an enzyme with more than one subunit

Allosteric enzyme regulation is usually associated with _____.

rabbits, horses, and herbivorous bears

An enlarged cecum is typical of _____.

more branching or folds

As the size of some animals has evolved to greater sizes, the effectiveness of their adaptations that promote exchanges with the environment have also increased. For example, in many larger organisms, evolution has favored lungs and a digestive tract with _____.

b) both pathogens and mutualists

Bacteria in the human gut are which of the following? a) all mutualists b) both pathogens and mutualists c) all pathogens

enzymatic hydrolysis

Because the foods eaten by animals are often composed largely of macromolecules, animals need to have mechanisms for _____.

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

Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law?

these animals are not able to synthesize these nutrients

Certain nutrients are considered "essential" in the diets of some animals because _____.

c) exergonic; endergonic

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _____ is to _____. a) work; energy b) free energy; entropy c) exergonic; endergonic d) exergonic; spontaneous

less surface area per unit of volume

Compared with a smaller cell, a larger cell of the same shape has _____.

The stomach lining secretes mucus, a mixture of glycoproteins, cells, salts, and water. Submit

Consider the interior surface of the human stomach and its secretions, shown in the figure. Why doesn't gastric juice, composed of hydrochloric acid and a protease called pepsin, digest the cells that line the stomach?

stomach

Digestive secretions with a pH of 2 are characteristic of the _____.

-20 kcal/mol

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the G for the new reaction?

folic acid deprivation is associated with neural tube abnormalities in a fetus

Folic acid supplements have become especially important for pregnant women because _____.

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

For living organisms, which of the following is an important consequence of the first law of thermodynamics? a) The energy content of an organism is constant. b) Organisms grow by converting energy into organic matter. c) The organism ultimately must obtain all of the necessary energy for life from its environment. d) The entropy of an organism decreases with time as the organism grows in complexity.

They burrow under the mucus layer that covers the stomach epithelium.

Helicobacter pylori is a bacterial organism that causes ulcers and digestive disturbances. How might they survive the acid pH of the stomach?

screening for H. pylori infections

Historically inaccurate diagnosis of acid reflux disorders and gastric ulcers has been improved by _____.

Cells use the cycle to recycle ADP and phosphate.

How do cells use the ATP cycle shown in the figure?

Endotherms and ectotherms differ in the means by which they regulate their body temperature.

How do endotherms and ectotherms differ?

An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.

How does an enzyme increase the rate of the chemical reaction it catalyzes?

a) Ulcers are caused by the acid-tolerant bacterium Helicobacter pylori.

Identify the roles played by human gut bacteria. a) Ulcers are caused by the acid-tolerant bacterium Helicobacter pylori. b) The human appendix houses mutualistic bacteria that digest cellulose. c) Human gut bacteria synthesize all essential vitamins required by humans.

maintain a healthy weight, eat a balanced direct, and exercise

If there is a strong genetic link for type II diabetes mellitus in your family, how might you minimize your risk of developing the disorder?

flesh of another animal

If you found a vertebrate skull in the woods and the teeth were sharp and scissor-like, what type of food would you expect this animal to eat?

liver glycogen and muscle glycogen

If you were to jog one kilometer a few hours after lunch, which stored fuel would you probably tap?

c) Succinate is the substrate, and fumarate is the product in the reaction.

In a biological reaction, 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 if malonic acid. Select the correct identification of the molecules described in the reaction. a) Succinate dehydrogenase is the enzyme, and fumarate is the substrate in the reaction. b) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate in the reaction. c) Succinate is the substrate, and fumarate is the product in the reaction. d) Fumarate is the product, and malonic acid is a noncompetitive inhibitor in the reaction.

insulin; glucagon

In a healthy person, after a large meal, the production of _____ will increase. After fasting, the production of _____ will increase.

competitive inhibition

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

c) Small mammals have lower BMR, but use more calories per kilogram than large mammals.

Look at the graphs and choose the correct statement describing the relationship between BMR (basal metabolic rate) and body mass of mammals. (Look carefully at the quantity being displayed on the y-axis of each figure.) a) Large mammals have lower basal metabolic rates than small mammals. b) BMR is roughly proportional to body mass squared. c) Small mammals have lower BMR, but use more calories per kilogram than large mammals.

In ancestral hunter-gatherer communities, individuals with a tendency to gorge on such foods when available would have had a selective advantage.

Many people have a tendency to gorge on rich, fatty foods. How could such a preference have evolved?

temperature is usually uniform throughout a cell

Most cells cannot harness heat to perform work because _____.

d) parietal cells

Over-the-counter medications for acid reflux or heartburn block the production of stomach acid. Which of the following cells are directly affected by this medication? a) smooth muscle cells b) goblet cells c) chief cells d) parietal cells

They can more readily encounter and phosphorylate other membrane proteins.

Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?

activation energy

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____.

a) Light energy is converted to chemical energy during photosynthesis.

Select the correct statement about chemical energy, a term used by biologists to refer to potential energy available for release in a chemical reaction. a) Light energy is converted to chemical energy during photosynthesis. b) A photosynthetic cell within a plant leaf produces chemical energy, stored within glucose molecules. c) When a glucose molecule is catabolized to CO2 and H2O, chemical energy is lost.

a) Essential nutrients must be obtained from diet.

Select the correct statement about essential nutrients. a) Essential nutrients must be obtained from diet. b) All animals require an identical set of essential nutrients. c) Due to their biochemical sophistication, humans have to ingest fewer essential nutrients than do other animals.

b) An animal may be a regulator for one environmental variable but a conformer for another.

Select the correct statement describing feedback control in animals. a) Positive feedback loops contribute to homeostasis. b) An animal may be a regulator for one environmental variable but a conformer for another. c) Ectotherms are regulators with respect to temperature.

c) more active in summer because it can gain body heat by conduction

Snake behavior in Wisconsin changes throughout the year. For example, a snake is _____. a) more active in summer because that is the period for mating b) less active in winter because the food supply is decreased c) more active in summer because it can gain body heat by conduction d) less active in winter because it does not need to avoid predators

a thick, mucous secretion and active mitosis of epithelial cells

Stomach cells are moderately well adapted to the acidity and protein-digesting activities in the stomach by having _____.

evaporation

Sweating allows a person to lose heat through the process of _____.

most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood

The absorption of fats differs from that of carbohydrates in that _____.

is involved in the catalytic reaction of the enzyme

The active site of an enzyme is the region that _____.

homeostasis

The body's automatic tendency to maintain a constant and optimal internal environment is termed _____.

have more surface area for chemical digestion than do larger pieces of food.

The function of mechanical digestion is to break down large chunks of food into smaller pieces. Why is this important? Smaller pieces of food _____.

binding to their substrate

The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.

d) ΔG is the change in free energy.

The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is correct? a) T is the temperature in degrees Celsius. b) ΔH is the change in entropy, the energy available to do work. c) ΔS is the change in enthalpy, a measure of randomness. d) ΔG is the change in free energy.

warmer arterial blood transfers heat to the cooler venous blood

The thin horizontal arrows in the figure above show that the _____.

The free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi may vary considerably with variations in pH, temperature, atmospheric pressure, and concentrations of reactants and products.

What is the free energy change (ΔG) of the hydrolysis of ATP to ADP?

Proteins serve a variety of functions, and the body does not store excess quantities of protein.

What is the importance of consuming an adequate amount of proteins in the diet?

It may be used to form a phosphorylated intermediate.

When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?

It is lost to the environment.

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

stored as glycogen in the liver and muscles

When the digestion and absorption of organic carbohydrates results in more energy-rich molecules than are immediately required by an animal, the excess is _____.

b) snake - bulk feeder

Which of the following animals is correctly paired with its feeding mechanism? a) baleen whale - fluid feeder b) snake - bulk feeder c) aphid - suspension feeder d) clam - substrate feeder

a) condensation reactions

Which of the following involves a decrease in entropy? a) condensation reactions b) depolymerization reactions c) hydrolysis reactions d) reactions that separate monomer

d) Small and large animals face different physiological challenges because an animal's body mass increases cubically while its surface area increases as a squared function.

Which of the following is a true statement about body size and physiology? a) The rate at which an animal uses nutrients and produces waste products is independent of its volume. b) The amount of food and oxygen an animal requires and the amount of heat and waste it produces are inversely proportional to its mass. c) The wastes produced by an animal double as its volume doubles and triple as its surface area triples. d) Small and large animals face different physiological challenges because an animal's body mass increases cubically while its surface area increases as a squared function

c) a molecule binding at one unit of a tetramer, allowing faster binding at each of the other three

Which of the following is an example of cooperativity? a) one enzyme in a metabolic pathway passing its product to act as a substrate for the next enzyme in the pathway b) the binding of an end product of a metabolic pathway to the first enzyme that acts in the pathway c) a molecule binding at one unit of a tetramer, allowing faster binding at each of the other three d) binding of an ATP molecule along with one of the substrate molecules in an active site

d) a molecule of glucose

Which of the following is an example of potential rather than kinetic energy? a) water rushing over Niagara Falls b) light flashes emitted by a firefly c) a crawling beetle foraging for food d) a molecule of glucose

d) The reaction proceeds with a net release of free energy.

Which of the following is true for all exergonic reactions? a) A net input of energy from the surroundings is required for the reactions to proceed. b) The products have more total energy than the reactants. c) The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. d) The reaction proceeds with a net release of free energy.

c) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

Which of the following is true of enzymes? a) Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered. b) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. c) Enzymes increase the rate of chemical reaction by lowering activation energy barriers. d) Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.

c) The catalyzed reaction will have the same Δ_G_.

Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst? a) The catalyzed reaction will have higher activation energy. b) The catalyzed reaction will consume all of the catalyst. c) The catalyzed reaction will have the same Δ_G_. d) The catalyzed reaction will be slower.

c) stomach - protein digestion

Which of the following organs is correctly paired with its function? a) small intestine - starch digestion b) large intestine - bile production c) stomach - protein digestion d) pancreas - starch digestion

b) The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule.

Which of the following statements about the role of ATP in cell metabolism is true? a) The free energy released by ATP hydrolysis has a much more negative ΔG value than the hydrolysis of phosphate groups from other phosphorylated molecules. b) The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule. c) The phosphate bonds of ATP are unusually strong bonds.

a) Ectotherms are more abundant and diverse than endotherms.

Which statement about endotherms and ectotherms is correct? a) Ectotherms are more abundant and diverse than endotherms. b) Endothermy is a more successful strategy for thermoregulation than ectothermy. c) Ectotherms are more primitive than endotherms.

a) When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape.

Which statement about the binding of enzymes and substrates is correct? a) When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape. b) Substrate molecules fit into the active site of an enzyme like a key fits into a lock. c) Substrate molecules bind to the active site of the enzyme only by weak bonds, such as hydrogen bonds or hydrophobic attraction.

curves 1 and 4

Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?

graph 3

You collect data on the effect of pH on the function of the enzyme catalase in human cells. Which of the following graphs would you expect?

a cofactor necessary for enzyme activity

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as _____.