Micro ch 6 PRACTICE QUESTIONS

what is the maximum theoretical energy yield for oxidative phosphorylation in a prokaryotic cell?

6 ATP from glycolysis, 6 ATP from transition step, 22 ATP from TCA cycle, so there are 34 ATP for the total maximum yield

transition step of central metabolism

CO2 is first removed from pyruvate, a step called decarboxylation. Then, a redox reaction transfers electrons to NAD+, reducing it to NADH + H+. Finally, the remaining 2-carbon acetyl group is joined to coenzyme A to form acetyl-CoA.

Tricarboxylic acid cycle (TCA cycle)

Cyclic metabolic pathway that incorporates acetyl-CoA, ultimately generating ATP (or GTP), CO2, and reducing power; also called the Krebs cycle and the citric acid cycle

aerobic; anaerobic

E coli will preferentially use ___ respiration in the presence of O2, but when O2 is not available, it can switch to ____ respiration. if a suitable electron acceptor such as nitrate is present

a specific enzyme

Facilitates each step of a metabolic pathway. A molecule, usually a protein, that functions as a catalyst, speeding up a biological reaction. more than a thousand different ones exist in a cell

proton-motive force

Form of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient.

electron transport chain

Group [series] of membrane-embedded electron carriers (proteins) that pass electrons from one to another, and, in the process, create a proton motive force. [move protons across the membrane]

Non-competitive inhibition (by enzyme poisons)

Inhibitor PERMANENTLY changes the shape of the enzyme, making the enzyme non-functional. EX: Enzyme poisons such as mercury are used in certain antimicrobial compounds.

transition step

Step in metabolism that links glycolysis to the TCA cycle; Converts pyruvate to acetyl-CoA. Repeated twice, this produces 2 NADH + 2H+. six different precursor metabolites are made.

enzyme

function as biological catalysts speeding up a biological reaction; they are neither consumed nor permanently changed during a reaction.

reduce

gain of electrons

three central metabolic pathways

glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle (TCA cycle)

central metabolic pathways

glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle (TCA cycle); the transition step is often considered a part of the TCA cycle

cytoplasm, mitochondrial matrix

in eukaryotic cells, glycolysis and the pentose phosphate pathway take place in the ___. the transition step and TCA cycle take place in the ___.

Cytoplasm

in prokaryotic cells, all the central metabolic pathways occur in the ___.

Where is the electron transport chain located?

in the mitochondria

oxidized

loses electrons

glycolysis

metabolic pathway that splits and oxidizes glucose to two pyruvate molecules gradually, generating some ATP and reducing power plus six precursor metabolites

aerobic respiration

metabolic process in which electrons are transferred from the electron transport chain to molecular oxygen (O2) [uses O2 as a terminal electron acceptor]

electron carrier

molecules cells use to shuttle electrons; they readily accept and then donate electrons

in prokaryotes aerobic respiration yields______ energy than anaerobic respiration

more

cofactors

non-protein component required for the activity of some enzymes [enzymes sometimes act with the assistance of _____]

cofactor

non-protein component required for the activity of some enzymes. ex:Magnesium, zinc, copper, and other trace elements [book pic--enzyme with a _____ in the active site waiting for a substrate to join it]

energy source

oxidized to release its energy. compound that a cell oxidizes to harvest energy; also called an electron donor

Photosynthesis

pertaining to photosynthesis, the process of using [harvesting] the energy of [sun]light to [power the] synthesize organic compounds from CO2

antennae pigments

pigments of photosynthetic organisms that make up a complex that acts as a funnel, capturing [radiant] light energy and transferring it to reaction-center chlorophyll

light reactions

processes used by phototrophs to harvest energy from sunlight; the energy-gathering component of photosynthesis. [capture energy from light and convert it to chemical energy in the form of ATP. That energy is used for carbon fixation.]

exergonic

reactions release energy because the STARTING COMPOUND has MORE free energy than the PRODUCTS.

redox

reduce an electron carrier. transfer of electrons from one compound to another; one compound becomes reduced and the other becomes oxidized.

allosteric

refers to an enzyme or other protein that contains a site to which a small molecule can bind and change the protein's activity. Cells use this to adjust the activity of certain enzymes

metabolic pathway

series of sequential chemical reactions that are a part of metabolism

what happens to glucose inside a cell

some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis,, glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism,, some glucose might be oxidized to CO2, generating the maximum amount of ATP

energy

the capacity to do work

tricarboxylic acid cycle (TCA) (Krebs cycle, citric acid cycle)

the metabolic pathway that OXIDIZES a two carbon acetyl group to release two molecules of CO2 and generates the MOST reducing power of all the central metabolic pathways. [completes the oxidation of glucose; two "turns" produce 6 NADH + 6 H+, and 2 FADH2 in addition to 2 ATP. two intermediates are precursor metabolites]

ATP yield during aerobic respiration

the theoretical maximum ___ is 38 ATP

competitive inhibition

type of enzyme inhibitor that occurs when the inhibitor competes with the NORMAL substrate for binding to the active site. EX: sulfa drugs [picture--takes active site because similar chemical structure as paba] are used as antibacterial medications

non-competitive inhibition

type of enzyme inhibitor that results from a molecule binding to the enzyme at a site OTHER than the active site. produced by cells to regulate the activity of that cell's enzymes [occurs when the inhibitor and the substrate act at different sites on the enzyme]

Chloryphylls

used to capture radiant energy. the primary light-absorbing pigments used in photosynthesis

bacteriochlorophylls

used to capture radiant energy. type of chlorophyll used by purple and green bacteria; absorbs wavelengths of light that penetrate to greater depths and are not used by other photosynthetic organisms.

the terminal electron acceptors used in anaerobic respiration have lower electron affinities than O2.

why does anaerobic respiration yield less energy than aerobic respiration?

Non-competitive inhibition (by regulatory molecules)

Inhibitor changes the shape of the enzyme, so that the substrate can no longer bind the active site. This is a REVERSIBLE action that cells use to control the activity of allosteric enzymes.

precursor metabolites

Metabolic intermediates that can be either used to make the subunits of macromolecules or oxidized to generate ATP. [Five intermediates of glycolysis as well as the end product, pyruvate, are precursor metabolites used by E. coli]

Pentose Phosphate Pathway

Metabolic pathway that starts the degradation (breakdown) of glucose, generating reducing power in the form of (primary role is production of NADPH) NADPH, and two precursor metabolites for use in biosynthesis [also, 6 H+]

cellular respiration

Metabolic process that [uses the reducing power accumulated in the central metabolic pathways] transfers electrons stripped from a chemical energy source to an electron transport chain, generating a proton motive force that is then used to synthesize ATP. [by oxidative phosphorylation]

Catabolism

Metabolic processes that harvest [capture and store] energy released during the breakdown of compounds [complex molecules] such as glucose, using it to synthesize ATP. A set of chemical reactions that degrade compounds, releasing their energy.

Anabolism

Metabolic processes that synthesize and assemble the subunits of macromolecules [building blocks of cells], using energy of ATP; BIOSYNTHESIS.

Chemoorganotrophs

Organisms that obtain [harvest] energy by oxidizing [contained in] organic compounds such as glucose.

Glycolysis

[converts one molecule of glucose] the pathway SPLITS GLUCOSE and OXIDIZES it to form two molecules of pyruvate. the pathway provides the cell with a SMALL AMOUNT OF ATP, [2 ATP] some REDUCING power [2 NADH + H+], and SIX precursor metabolites

Calvin Cycle

[most common] metabolic pathway used by many autotrophs to incorporate CO2 into an organic form; also called the Calvin-Benson cycle

ATP synthase

[protein complex] permits protons to flow back across the membrane, harvesting the energy released to fuel the synthesis of ATP

Endergonic

[reactions use energy] requires a net input of energy because the products have more free energy than the starting compounds

anaerobic respiration

[uses a molecule other than O2 as a terminal electron acceptor] metabolic process in which electrons are transferred from the electron transport chain to a terminal electron acceptor other than O2

Fermentation

[uses pyruvate or a derivative electron acceptor; this recycles the reduced electron carrier NADH] Metabolic process that stops short of oxidizing glucose or other organic compounds completely, using an organic intermediate as a terminal electron acceptor.

coenzymes

a subset of cofactors, non-protein organic compounds that assist some enzymes. they act as a loosely bound carrier of small molecules or electrons. Include the electron carriers FAD, NAD+, and NADP+ (play an important role in enzyme-catalyzed oxidation-reduction reactions) some come from organic necessary vitamins

active site

a substrate binds to an _______ forming an enzyme-substrate complex that lowers the activation energy of the reaction. [on the surface of an enzyme; aka the catalytic site. a relatively small crevice. critical site to which a substrate binds by weak forces]

FAD/FADH2

abbreviations for the oxidized/reduced forms of flavin adenine dinucleotide, an electron carrier

NADP+/NADPH

abbreviations for the oxidized/reduced forms of nicotinamide adenine dinucleotide phosphate, an electron carrier

NAD+/NADH

abbreviations for the oxidized/reduced forms of nicotinamide adenine dinucleotide, an electron carrier

ATP

energy currency of the cell. hydrolysis of its unstable phosphate bonds can be used to power endergonic [energy -consuming] reactions.

non competitive regulation

cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversibly and distort them. this control of enzymes is called _______

enzyme inhibitors

competitive and noncompetitive

reaction-center pigments

electron donors in the photosynthetic process; an example is chlorophyll.