Chapter 5

During contraction of a muscle, calcium ions bind to a the actin myofilament. b the troponin molecule. c the tropomyosin molecule. d the sarcoplasmic reticulum. e the sarcolemma.

b the troponin molecule

Energy is released when Multiple Choice a. ADP is broken down into ATP and phosphate. b. ATP is broken down into ADP and phosphate. c. ADP and phosphate combine to form ATP. d. ATP and phosphate combine to form ADP. e. AMP and two phosphates combine to form ATP.

b. ATP is broken down into ADP and phosphate.

Enzymes are __________. a. lipids b. proteins c. carbohydrates d. nucleic acids

b. proteins

Which statement most accurately describes the second law of thermodynamics? a. Energy cannot be created or destroyed, but it can be changed from one form to another. b. Energy can be created or destroyed. c. Energy can be recycled within an ecosystem. d. Energy cannot be changed from one form to another without a loss of usable energy. e. One usable form of energy can be completely converted into another usable form.

Energy cannot be changed from one form to another without a loss of usable energy. Explanation The second law of thermodynamics tells us energy cannot be changed from one form to another without a loss of usable energy.

Which of the following will pass through a cell membrane most easily? a. CO2, a small nonpolar molecule b. proteins, large polar molecules c. water, a small polar molecule d. both CO2 and water will easily pass through e. All of the answer choices are correct.

a. CO2, a small nonpolar molecule

Factors that may affect the passage of materials across cell membranes include a. all of the above answers. b. charge. c. time. d. size. e. concentration.

a. all of the above answers. Explanation The plasma membrane is selectively permeable to molecules and ions. Their size, concentration (number), and time are all able to influence the degree to which they pass or do not pass across the membrane

The bond between the actin and myosin head is broken when a. an ATP molecule binds to the myosin head. b. an ATP molecule binds to the actin molecule. c. an ATP molecule breaks down on the myosin head. d. an ATP molecule breaks down on the actin molecule. e. ADP and phosphate bind to the myosin head.

a. an ATP molecule binds to the myosin head.

Diffusion is defined as the movement of Multiple Choice a. molecules from areas of higher concentration to areas of lower concentration. b. molecules from areas of lower concentration to areas of higher concentration. c. water molecules across a membrane. d. gas molecules across a membrane. e. gas or water molecules across a membrane.

a. molecules from areas of higher concentration to areas of lower concentration.

Which of these words should be classified separately from the others? a. osmosis b. diffusion c. active transport d. facilitated diffusion e. passive transport

c. active transport Explanation Active transport moves materials from low to high concentration requiring the addition of ATP energy to carry this out. Osmosis, diffusion, and passive transport are all mechanisms moving molecules from high to low concentration.

Which form of passive transport allows small noncharged molecules, such as oxygen, to cross the cell membrane? a. pinocytosis b. osmosis c. diffusion d. plasmolysis e. phagocytosis

c. diffusion Explanation In cells, diffusion may occur across a plasma membrane. Some small noncharged molecules, such as oxygen and carbon dioxide, are able to slip between the phospholipid molecules making up the plasma membrane.

A red blood cell placed in a hypertonic medium will a. gain water. b. gain solute. c. lose water. d. lose solute. e. become a white blood cell.

c. lose water.

The biosynthesis of an amino acid is carried out in a specific sequence of reaction called a/an __________. a. enzyme b. substrate c. inhibition d. biochemical pathway

d. biochemical pathway

Enzymes speed up chemical reactions by a. increasing the amount of reactants available. b. raising the energy of activation required. c. increasing the temperature of the reaction. d. lowering the energy of activation required.

d. lowering the energy of activation required.

A tube with a membrane covering the bottom is placed in a beaker. The membrane allows water to flow through but not salt or glucose. The tube contains an aqueous solution with 4% salt and 20% glucose and the beaker contains an aqueous solution with 12% salt and 6% glucose. How could you describe the solution in the beaker compared to the solution in the tube? a. The beaker solution is hypertonic to the tube solution. b. The beaker contents and the tube contents will not change. c. The beaker and tube solutions are isotonic to each other. d. The beaker solution is sweeter than the tube solution. e. The beaker solution is hypotonic to the tube solution.

e. The beaker solution is hypotonic to the tube solution. . Explanation The beaker solution has less solute than the tube solution. This makes the beaker solution hypotonic relative to the tube solution.

Water will move from areas of ________ concentration to areas of _______ concentration in order to reach equilibrium.

greater, lesser

The diffusion of water across semipermeable membranes is called ______. The ______(dissolved salt) cannot cross membranes.

osmosis, solute

For example, if a cell containing 5% salt was placed in an environment containing 15% salt, water would move ______the cell because there is a ________ concentration of water inside the cell compared to its environment.

out of, greater

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

The second law of thermodynamics states that all energy transformations result in an increase in entropy (disorder). If so, how does photosynthesis, which is an energy transformation, create order rather than disorder? a. The tree takes in small disordered molecules like carbon dioxide from the air and water from the earth and using solar energy produce highly ordered sugar molecules like glucose. b. Photosynthesis does not actually create order. c. Plants take highly ordered molecules like glucose and break them into smaller disordered molecules like carbon dioxide and water. d. Plants do not have mitochondria like animals and therefore cannot create disorder. e. Plants do not obey the second law of thermodynamics.

a. The tree takes in small disordered molecules like carbon dioxide from the air and water from the earth and using solar energy produce highly ordered sugar molecules like glucose. Explanation The second law of thermodynamics refers to chemical reactions that release energy when they break apart substances. Photosynthesis utilizes solar energy in order to build organic molecules which creates highly structured ordered molecules.

When a car burns gasoline, much of the energy is released in the form of heat. Which of the following best describes this process in relation to the first law of thermodynamics? a. energy can be changed from one form to another b. energy is conserved c. energy is often destroyed d. energy is always used up in reactions e. all energy comes from the sun

a. energy can be changed from one form to another Explanation The first law of thermodynamics states that energy cannot be created or destroyed but can be changed from one form of energy to another. Some of the potential energy stored in the gasoline is changed to heat as the car converts it into the kinetic energy of motion.

The opposite of a turgid plant cell is a a. plasmolyzed plant cell. b. hypertonic plant cell. c. isotonic plant cell. d. osmotic plant cell. e. ruptured plant cell.

a. plasmolyzed plant cell. Explanation Turgid is a term that applies when a plant cell is placed in a hypotonic solution. In this type of environment, the vacuole gains water and the plasma membrane pushes against the cell wall. In a cell that is exposed to a hypertonic solution, the plasma membrane pulls away from the cell wall as the vacuole loses water.

The special carrier molecules form a. protein channels. b. lipid channels. c. carbohydrate channels. d. enzymes. e. inhibitors.

a. protein channels.

The energy of activation is best described as a. the energy threshold that must be reached before a reaction can proceed and products may be formed. b. the speed at which a reaction proceeds to form products. c. a protein that speeds up a chemical reaction. d. None of the answer choices is correct.

a. the energy threshold that must be reached before a reaction can proceed and products may be formed.

A white blood cell surrounds and engulfs a worn-out red blood cell. This process is called a. facilitated diffusion. b. pinocytosis. c. phagocytosis d. active transport. e. exocytosis..

c. phagocytosis Explanation Certain human cells are able to engulf worn-out cells or bacteria by a process known as phagocytosis.

Which of the following binds to the active site of an enzyme? a. water b. product c. substrate d. any other enzyme

c. substrate

Simple diffusion across a plasma membrane is called passive transport because it a. moves molecules from low to high concentration. b. requires energy from the cell. c. does not require the presence of an enzyme. d. does not require control by the nucleus. e. does not require energy from the cell.

e. does not require energy from the cell. Explanation Simple diffusion is passive because a cell does not need to expend energy for it to happen. Small, non-charged molecules, such as oxygen and carbon dioxide, are able to slip between the phospholipid molecules making up the plasma membrane.

Which of the following is best associated with a coupled reaction? a. The breakdown of ATP generally releases more energy (and heat) than is needed to power the metabolic reaction. b. ATP consumes energy from another metabolic reaction. c. ADP is used up in the metabolic reaction. d. ADP often transfers a phosphate to the reactant. e. ATP gains a phosphate group during the metabolic reaction.

Explanation ATP stores energy that can be used in a coupled biological reaction that requires energy. To do this ATP loses the last phosphate group converting the molecule to ADP & P. The phosphate group is often transferred to some reactant that allows it to carry out some biological process. The breakdown of ATP generally releases more energy (and heat) than the amount consumed by the energy-requiring reaction.

Enzymes are able to speed up the rate of a reaction by a. lowering the energy needed for the reaction to proceed. b. producing more substrates. c. producing more enzymes. d. transferring electrons from one substance to another. e. binding substrates to a membrane.

a. lowering the energy needed for the reaction to proceed. Explanation Enzymes are able to overcome the energy needed to start a reaction, called the energy of activation. By doing this, they make reactions happen more readily

In a biochemical pathway, the product of the first reaction becomes the _______ for the second enzyme. a. substrate b. enzyme c. product d. inhibitor

a. substrate

ATP is a good source of energy for a cell because a. it provides excess energy for cellular reactions. b. it takes no energy to make it. c. its breakdown is coupled with energy-requiring reactions. d. it is not reusable. e. it is able to be used in only one type of reaction.

c. its breakdown is coupled with energy-requiring reactions. Explanation Adenosine triphosphate contains the energy used by cells. It is versatile and can be used in many types of reactions occurring inside cells. The energy it releases is usually just sufficient for a biological purpose and does not waste more energy than needed. Its ability to break down and regenerate make it a reusable energy form that is easily coupled to an energy requiring reaction

Which of the following statements correctly describes an energy transformation in living organisms? a. Chloroplasts produce CO2 and H2O during photosynthesis. b. Mitochondria convert ATP molecules into glucose. c. Chloroplasts burn glucose into ATP molecules during cell respiration. d. Chloroplasts convert solar energy to the chemical energy of nutrient molecules. e. Mitochondria capture solar energy and convert it to oxygen.

d. Chloroplasts convert solar energy to the chemical energy of nutrient molecules. Explanation Chloroplasts use solar energy to convert carbon dioxide and water into the chemical energy of nutrient molecules such as glucose. Mitochondria convert this chemical energy into ATP molecules, which cells use to perform chemical, transport, and mechanical work.

Which of the following is the site of ATP binding and hydrolysis? a. troponin b. tropomysin c. actin d. myosin e. both troponin and tropomysin

d. myosin

Which of the following correctly lists the order in which energy flows through an ecosystem? a. chloroplast - mitochondria - solar energy b. solar energy - mitochondria - chloroplast c. chloroplast - solar energy - mitochondria d. solar energy - chloroplast - mitochondria e. mitochondria - solar energy - chloroplast

d. solar energy - chloroplast - mitochondria Explanation Chloroplasts convert solar energy to chemical energy of nutrient molecules. The mitochondria then convert this chemical energy to ATP molecules, which cells use to perform work.

What is the function of an enzyme? a. inhibits chemical reactions b. inhibits metabolism c. increases the energy of activation d. speeds up chemical reactions

d. speeds up chemical reactions

Both starch and cellulose are made by stringing together many glucose molecules, but starch is easily digested by humans, while cellulose is indigestible. The starch polysaccharide has every bond occurring below the sugar rings while the bonds in cellulose alternate between one bond above the ring and the next below the ring. How can you explain humans' inability to digest cellulose? a. Humans do not eat cellulose. b. Cellular respiration is only capable of breaking down specific bonds. c. The alternating bonds make the cellulose molecule too large and bulky to enter cells for digestion. d. The acidic molecules found in stomach acid cannot act on the bonds that are above the sugar rings in cellulose. e. The enzyme that breaks down starch can only fit the specific bond configuration of bonds below the ring.

e. The enzyme that breaks down starch can only fit the specific bond configuration of bonds below the ring. Explanation Enzymes have very specific three-dimensional shapes that allow them to fit one type of molecule only. Every enzyme has a specific substrate.

What process typically regulates the enzymes involved in metabolic reactions? a. substrate inhibition b. temperature levels c. pH change d. ATP blockage e. feedback inhibition

e. feedback inhibition Explanation Most enzymes are regulated by feedback inhibition. When a product is in abundance, it competes with the substrate for the enzyme's active site. As more product is made, the inhibition is increased. As the product is used up, inhibition is reduced and more product can be produced.

The rate of diffusion is affected by which of the following? a. temperature b. size of molecules c. steepness of the concentration gradient d. temperature and size of molecules e. temperature, size of molecules, and steepness of concentration gradient

e. temperature, size of molecules, and steepness of concentration gradient

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference. ATP required

What prevents a plant cell from bursting in a hypotonic solution? a. the presence of a cell wall b. the presence of chloroplasts c. water moving out of the cell d. transport proteins, which help pump the excess water out of the cell e. plasma membrane

a. the presence of a cell wall Explanation When a plant cell is placed in a hypotonic solution, the vacuole gains water and the plasma membrane pushes against the cell wall. The plant cell does not burst because the cell wall does not give way.

Facilitated diffusion requires a. enzymes. b. carrier proteins. c. lipid carriers. d. carbohydrate carriers. e. lipid or carbohydrate carriers.

b. carrier proteins.

Which of the following is a mechanism used to regulate enzyme activity? a. active transport b. feedback inhibition c. phagocytosis d. facilitated diffusion e. osmosis

b. feedback inhibition Explanation The only answer listed that regulates enzyme activity is feedback inhibition. All of the other answers describe ways things can move in and out of the cell.

If blood cells are placed in a hypertonic solution, the cells will a. be unaffected since they have a cell membrane to separate them from the solution. b. shrink due to water loss by the cell. c. burst due to active transport. d. swell due to diffusion. e. shrink due to the loss of solutes from the blood cell.

b. shrink due to water loss by the cell. Explanation In hypertonic solutions (like salt water) the concentration of solutes outside the cell are greater than inside the cell. The cell will lose water to this type of environment causing it to shrink.

When sugar is mixed with water, equilibrium is reached when a. molecules of sugar stop moving. b. water and sugar molecules are moving at the same speed. c. the dissolved sugar molecules are evenly distributed throughout the solution. d. there are the same number of water molecules as dissolved sugar molecules. e. two tablespoons of coffee are added.

c. the dissolved sugar molecules are evenly distributed throughout the solution.

When a biochemical pathway is functioning, the initial ________ is continually converted to the final product through the series of steps in the pathway. a. enzyme b. inhibitor c. energy d. substrate

d. substrate

Osmosis is best defined as the movement of a. molecules from an area of high concentration to an area of lower concentration. b. molecules from an area of low concentration to an area of higher concentration. c. water molecules across a membrane from an area of low concentration to an area of higher concentration. d. water molecules across a membrane from an area of high concentration to an area of lower concentration. e. water molecules inside a container.

d. water molecules across a membrane from an area of high concentration to an area of lower concentration.