Energy in Living Systems Quiz

PDF page 291: As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we’ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in

PDF page 293: A living cell cannot store significant amounts of free energy. Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion that could damage and then destroy the cell. Rather, a cell must be able to handle that energy in a way that enables the cell to store energy safely and release it for use only as needed. Living cells accomplish this by using the compound adenosine triphosphate (ATP). ATP is often called the “energy currency” of the cell, and, like currency, this versatile compound can be used to fill any energy need of the cell. How? It functions similarly to a rechargeable battery. When ATP is broken down, usually by the removal of its terminal phosphate group, energy is released. The energy is used to do work by the cell, usually by the released phosphate binding to another molecule, activating it. For example, in the mechanical work of muscle contraction, ATP supplies the energy to move the contractile muscle proteins. Recall the active transport work of the sodium-potassium pump in cell membranes. ATP alters the structure of the integral protein that functions as the pump, changing its affinity for sodium and potassium. In this way, the cell performs work, pumping ions against their electrochemical gradients. ATP Structure and Function At the heart of ATP is a molecule of adenosine monophosphate (AMP), which is composed of an adenine molecule bonded to a ribose molecule and to a single phosphate group (Figure 7.3). The addition of a second phosphate group to this core molecule results in the formation of adenosine diphosphate (ADP); the addition of a third phosphate group forms adenosine triphosphate (ATP).

PDF page 291: As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we’ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in

PDF page 291: As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we’ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in

PDF page 291: As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we’ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in

PDF page 291: As we learned in previous chapters, living organisms require free energy to power life processes such as growth, reproduction, movement, and active transport. ATP (adenosine triphosphate) functions as the energy currency for cells. It allows the cells to store energy and transfer it within the cells to provide energy for cellular processes such as growth, movement and active transport. The ATP molecule consists of a ribose sugar and an adenine base with three phosphates attached. In the hydrolysis of ATP, free energy is supplied when a phosphate group or two are detached, and either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) is produced. Energy derived from the metabolism of glucose is used to convert ADP to ATP during cellular respiration. As we explore cellular respiration, we’ll learn that the two ways ATP is regenerated by the cell are called substrate-level phosphorylation and oxidative phosphorylation. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in

PDF page 293: resulting hydrogen atom (H ) and a hydroxyl group (OH ) are added to the larger molecule. The hydrolysis of ATP produces ADP, together with an inorganic phosphate ion (Pi), and the release of free energy. To carry out life processes, ATP is continuously broken down into ADP, and like a rechargeable battery, ADP is continuously regenerated into ATP by the reattachment of a third phosphate group. Water, which was broken down into its hydrogen atom and hydroxyl group during ATP hydrolysis, is regenerated when a third phosphate is added to the ADP molecule, reforming ATP. Obviously, energy must be infused into the system to regenerate ATP. Where does this energy come from? In nearly every living thing on earth, the energy comes from the metabolism of glucose. In this way, ATP is a direct link between the limited set of exergonic pathways of glucose catabolism and the multitude of endergonic pathways that power living cells. Phosphorylation Recall that, in some chemical reactions, enzymes may bind to several substrates that react with each other on the enzyme,

PDF page 291: The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. These questions address the following standards: [APLO 2.5][APLO 2.16] Energy production within a cell involves many coordinated chemical pathways. Most of these pathways are combinations of oxidation and reduction reactions. Oxidation and reduction occur in tandem. An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation

PDF page 291: The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. These questions address the following standards: [APLO 2.5][APLO 2.16] Energy production within a cell involves many coordinated chemical pathways. Most of these pathways are combinations of oxidation and reduction reactions. Oxidation and reduction occur in tandem. An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation

PDF page 292: and reduction usually occur together, these pairs of reactions are called oxidation reduction reactions, or redox reactions.

PDF page 292: The removal of an electron from a molecule, oxidizing it, results in a decrease in potential energy in the oxidized compound. The electron (sometimes as part of a hydrogen atom), does not remain unbonded, however, in the cytoplasm of a cell. Rather, the electron is shifted to a second compound, reducing the second compound. The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound). The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. The transfer of energy in the form of electrons allows the cell to transfer and use energy in an incremental fashion—in small packages rather than in a single, destructive burst. This chapter focuses on the extraction of energy from food; you will see that as you track the path of the transfers, you are tracking the path of electrons moving through metabolic pathways. Electron Carriers In living systems, a small class of compounds functions as electron shuttles: They bind and carry high-energy electrons between compounds in pathways. The principal electron carriers we will consider are derived from the B vitamin group and are derivatives of nucleotides. These compounds can be easily reduced (that is, they accept electrons) or oxidized (they

PDF page 292: The removal of an electron from a molecule, oxidizing it, results in a decrease in potential energy in the oxidized compound. The electron (sometimes as part of a hydrogen atom), does not remain unbonded, however, in the cytoplasm of a cell. Rather, the electron is shifted to a second compound, reducing the second compound. The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound). The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. The transfer of energy in the form of electrons allows the cell to transfer and use energy in an incremental fashion—in small packages rather than in a single, destructive burst. This chapter focuses on the extraction of energy from food; you will see that as you track the path of the transfers, you are tracking the path of electrons moving through metabolic pathways. Electron Carriers In living systems, a small class of compounds functions as electron shuttles: They bind and carry high-energy electrons between compounds in pathways. The principal electron carriers we will consider are derived from the B vitamin group and are derivatives of nucleotides. These compounds can be easily reduced (that is, they accept electrons) or oxidized (they

PDF page 292: The removal of an electron from a molecule, oxidizing it, results in a decrease in potential energy in the oxidized compound. The electron (sometimes as part of a hydrogen atom), does not remain unbonded, however, in the cytoplasm of a cell. Rather, the electron is shifted to a second compound, reducing the second compound. The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound). The transfer of electrons between molecules is important because most of the energy stored in atoms and used to fuel cell functions is in the form of high-energy electrons. The transfer of energy in the form of electrons allows the cell to transfer and use energy in an incremental fashion—in small packages rather than in a single, destructive burst. This chapter focuses on the extraction of energy from food; you will see that as you track the path of the transfers, you are tracking the path of electrons moving through metabolic pathways. Electron Carriers In living systems, a small class of compounds functions as electron shuttles: They bind and carry high-energy electrons between compounds in pathways. The principal electron carriers we will consider are derived from the B vitamin group and are derivatives of nucleotides. These compounds can be easily reduced (that is, they accept electrons) or oxidized (they

PDF page 292: lose electrons). Nicotinamide adenine dinucleotide (NAD) (Figure 7.2) is derived from vitamin B3, niacin. NAD is the oxidized form of the molecule; NADH is the reduced form of the molecule after it has accepted two electrons and a proton (which together are the equivalent of a hydrogen atom with an extra electron).

PDF page 292: lose electrons). Nicotinamide adenine dinucleotide (NAD) (Figure 7.2) is derived from vitamin B3, niacin. NAD is the oxidized form of the molecule; NADH is the reduced form of the molecule after it has accepted two electrons and a proton (which together are the equivalent of a hydrogen atom with an extra electron).