Chapter 8 - Cellular Energetics

Quantum mechanics

________ established that light, a form of electromagnetic radiation, has properties of both waves and particles.

NAD

________ is exclusively a two- electron carrier: it accepts or releases a pair of electrons at a time.

QH2

The quinone then binds two protons from the cytosol, forming the reduced quinone (________), which is released from the reaction center Chloroplasts Contain Two Functionally and Spatially Distinct Photosystems.

phosphate transporter

The ________ catalyzes the import of one HPO4 2 coupled to the export of one OH.

Phosphofructokinase-1

________ is allosterically inhibited by ATP and allosterically activated by AMP.

photosynthetic process

The ________ in plants can be divided into four stages, each localized to a defined area of the chloroplast,

heme component

Like the ________ of cytochromes, chlorophylls consist of a porphyrin ring attached to a long hydrocarbon side chain.

Environmental conditions

________ regulate the amount of thermogenin in brown- fat mitochondria.

photosynthetic algae

When ________ are exposed to a brief pulse of 14C- labeled CO2 and the cells are then quickly disrupted, 3- phosphoglycerate is radiolabeled most rapidly, and all the radioactivity is found in the carboxyl group Synthesis of Sucrose Incorporating Fixed CO2 Is Completed in the Cytosol.

F0F1

Protons move down their concentration gradient from the thylakoid lumen to the stroma through the ________ complex (ATP synthase), which couples proton movement to the synthesis of ATP from ADP and Pi.

glycolysis

Since ________ of one glucose molecule generates two acetyl CoA molecules, the reactions in the glycolytic pathway and citric acid cycle produce six CO2 molecules, ten NADH molecules, and two FADH2 molecules per glucose molecule.

relative contribution

The ________ of the two components to the total pmf depends on the permeability of the membrane to ions other than H+.

ATP

Synthesis of most of the ________ generated in aerobic oxidation is coupled to the reoxidation of NADH and FADH2 by O2 in a stepwise process involving the respiratory chain, also called the electron transport chain.

Calvin cycle

The ________ enzymes that catalyze CO2 fixation are rapidly inactivated in the dark, thereby conserving ATP that is generated in the dark for other synthetic reactions, such as lipid and amino acid biosynthesis.

Photosynthesis

________ is always accompanied by photorespiration-- a process that takes place in light, consumes O2, and converts ribulose 1, 5- bisphosphate in part to CO2.

Coenzyme Q

________ (CoQ), also called ubiquinone, is the only electron carrier in the respiratory chain that is not a protein- bound prosthetic group.

major energy

They are released into the blood are taken up and oxidized by most other cells, constituting the ________ source for many tissues, particularly heart muscle.

free energy

Most of the ________ released during the oxidation of glucose to CO2 is retained in the reduced coenzymes NADH and FADH2 generated during glycolysis and the citric acid cycle.

inner membrane

The ________ of brown- fat mitochondria contains thermogenin, a protein that functions as a natural uncoupler of oxidative phosphorylation.

Q cycle

In the ________, two molecules of CoQH2 are oxidized to CoQ at the Qo site and release a total of four protons into the intermembrane space, but one molecule of CoQH2 is regenerated from CoQ at the Qi site 8.3- Harnessing the Proton- Motive Force for Energy- Requiring Process Bacterial Plasma- Membrane Proteins Catalyze Electron Transport and Coupled ATP Synthesis.

aspartate residue

A(n) ________, Asp61, in the center of one of these helices is thought to participate in proton movement ATP- ADP Exchange Across the Inner Mitochondrial Membrane Is Powered by the Proton- Motive Force.

facultative anaerobes

In the absence of oxygen, ________ convert glucose to one or more two- or three- carbon compounds, which are generally released into the surrounding medium.

O2

As with NADH generated in the mitochondrial matrix, electrons from cytosolic NADH are ultimately transferred to ________ via the respiratory chain, concomitant with the generation of a proton- motive force.

glycolytic enzymes

The three ________ that are regulated by allosteric molecules catalyze reactions with large negative △Go, values- reactions that are essentially irreversible under ordinary conditions.

Electron Transport

It produces a small amount of ATP and the three- carbon compound pyruvate 8.2- ________ and Generation of the Proton- Motive Force.

photosynthetic organisms

Found in all ________, both eukaryotic and prokaryotic, photosystems consist of two closely linked components: a reaction center, where the primary events of photosynthesis occur, and an antenna complex consisting of numerous protein complexes, termed light- harvesting complexes (LHCs), which capture light energy and transmit it to the reaction center Photoelectron Transport from Energized Reaction- Center Chlorophyll a Produces a Charge Separation.

contrast

In ________, white- fat tissue is specialized for the storage of fat and contains relatively few mitochondria.

photosynthetic reaction centers

The three- dimensional structures of the ________ from two purple bacteria have been determined, permitting scientists to trace the detailed paths of electrons during and after the absorption of light.

small molecules

Most enzymes and ________ involved in the citric acid cycle are soluble in an aqueous solution and are localized to the mitochondrial matrix.

thioredoxin

A stromal protein called ________ (Tx) also plays a role in controlling some Calvin cycle enzymes Photorespiration, Which Competes with Photosynthesis, Is Reduced in Plants That Fix CO2 by the C4 Pathway.

Photorespiration

________ is wasteful to the energy economy of the plant: it consumes ATP and O2, and it generates CO2.

significant voltage gradient

A(n) ________ can develop only if the membrane is poorly permeable to other cations and to anions, as is the inner mitochondrial membrane.

Succinate dehydrogenase

________ and- ketoglutarate dehydrogenase are integral proteins in the inner membrane, with their active sites facing the matrix.

Glucose metabolism

________ is controlled differently in various mammalian tissues to meet the metabolic needs of the organism as a whole.

oxidative phosphorylation

Although bacteria lack any internal membranes, aerobic bacteria nonetheless carry out ________ by the same processes that occur in eukaryotic mitochondria.

E coli

Mitochondria are among the larger organelles in the cell, each one being about the size of a(n) ________ bacterium Mitochondria Possess Two Structurally and Functionally Distinct Membranes.

mesophyll

Because of the transport of CO2 from ________ cells, the CO2 concentration in the bundle sheath cells of C4 plants is much higher than it is in the normal atmosphere.

Iron sulfur clusters

________ are nonheme, iron- containing prosthetic groups consisting of Fe atoms bonded both to inorganic S atoms and to S atoms on cysteine residues on a protein.

PSII

In order for ________ and PSI to act in sequence during linear electron flow, the amount of light energy delivered to the two reaction centers must be controlled so that each center activates the same number of electrons.

CoQ

________ and Cytochrome c as Mobile Electron Shuttles: The four electron- transport complexes just described are laterally mobile in the inner mitochondrial membrane; moreover, they are present in unequal amounts and do not form stable contacts with one another ________ and Three Electron- Transport Complexes Pump Protons Out of the Mitochondrial Matrix.

F0

The ________ component contains three types of integral membrane proteins, designated a, b, and c.

large multiprotein complexes

Each of the four ________ in the respiratory chain spans the inner mitochondrial membrane and contains several prosthetic groups that participate in moving electrons.

Initial Charge Separation

________: The mechanism of charge separation in the photosystem of purple bacteria is identical to that in plants outlined earlier; that is, energy from absorbed light is used to strip an electron from a reaction- center bacteriochlorophyll a molecule and transfer it.

Chloroplasts

________ are bounded by two membranes, which do not contain chlorophyll and do not participate directly in photosynthesis.

peroxisome

The ________ is now recognized as the principal organelle in which fatty acids are oxidized in most cell types.

Enzymes

________ that catalyze the reactions of both the glycolytic pathway and the citric acid cycle are present in the cytosol of bacteria.

Adult humans

________ have little brown fat, but human infants have a great deal 8.4- Photosynthetic Stages and Light- Absorbing Pigments Thylakoid Membranes Are the Sites of Photosynthesis in Plants.

Electron transfer

________ from NADH and FADH2 to O2, regenerating the oxidized electron carriers NAD and FAD.

Absorption of Light

________ The initial step in photosynthesis is the ________ by chlorophylls attached to proteins in the thylakoid membranes.

carrier of hydrogen

It is a(n) ________ atoms, that is, protons plus electrons.