ch 10 bacterial metabolism

Question 1

aspects of metabolism common to all organisms

Answer 1

• life obeys the laws of thermodynamics
• the energy cells obtain from their environment is most often conserved as ATP
• oxidation-reduction (redox) reactions play a critical role in energy conservation
• the chemical reactions that occur in cells are organized into pathways
• each reaction of a pathway is catalyzed by an enzyme or a ribozyme
• the functioning of biochemical pathways is regulated

Question 2

three major types of work

Answer 2

chemical work - synthesis of complex molecules
transport work - take up of nutrients, eliminate wastes, and maintain ion balances
mechanical work - cell motility and movement of structures within cells

Question 3

substrate level phosphorylation

Answer 3

mechanisms for making ATP using molecules such a phosphoenolpyruvate (PEP) as a source of the phosphoryl group

Question 4

phosphate transfer potential

Answer 4

anility to donate a phosphoryl group to other molecules
- ATP is high

Question 5

electron transport chain (ETC)

Answer 5

system of electron carriers membrane-bound and organized

Question 6

electron carriers

Answer 6

located in plasma membranes and intracytoplasmic membranes of bacterial and archaeal cells
localized in the internal membranes of mitochondria and chloroplasts in eukaryotic cells
- NAD, NADP, FAD, FMN, CoQ, cytochromes, nonheme iron proteins, ferredoxin

Question 7

biochemical pathways

Answer 7

sets of chemical reactions performed by organisms that convert a starting substrate into one or more products
can be linear, cyclic, branching

Question 8

metabolite flux

Answer 8

rate of turnover of a metabolite (rate at which a metabolite is formed and then used)

Question 9

apoenzyme

Answer 9

protein component of an enzyme

Question 10

cofactor

Answer 10

nonprotein component of an enzyme

Question 11

holoenzyme

Answer 11

the complete enzyme consisting of the apoenzyme and its cofactor

Question 12

prosthetic group

Answer 12

if the cofactor is tightly or covalently attached to the apoenzyme

Question 13

coenzyme

Answer 13

if the cofactor is loosely attaching and can dissociate from the apoenzyme after products have been formed

Question 14

six classes of enzymes

Answer 14

• oxidoreductase: oxidation-reduction reactions
• transferase: reactions involving the transfer of chemical groups btw molecules
• hydrolase: hydrolysis (break down) of molecules
• lyase: breaking of C-C, C-O, C-N and other bonds by a means other than hydrolysis
• isomerase: rearranges molecules to isomer form
• ligase: joining of two molecules using ATP (or the energy of other nucleoside triphosphates)

Question 15

enzyme activity is significantly impacted by:

Answer 15

• substrate conc
• pH
• temp

Question 16

competitive inhibitor

Answer 16

directly competes with binding of substrate to catalytic site and prevents the enzyme from forming product

Question 17

noncompetitive inhibitor

Answer 17

binds enzyme at site other than active site
changes enzyme’s shape so that it becomes inactive or less active

Question 18

ribozymes

Answer 18

catalytic RNA molecules
functions:
- splicing of pre-rRNA
- splicing of mitochondrial rRNA and mRNA
- splicing of chloroplast tRNA, rRNA and mRNA
- splicing of viral mRNA

Question 19

metabolism

Answer 19

important for conservation of energy and materials
maintenance of metabolic balance despite changes in environment
3 major mechanisms:
- metabolic channeling
- regulation of the synthesis of a particular enzyme
- direct controlling of the activity of enzymes

Question 20

metabolic channeling

Answer 20

influences pathway activity by localizing metabolites and enzymes to specific parts of a cell
uses compartmentation - the distribution of enzymes and metabolites among separate cell structures or organelles

Question 21

posttranslational regulation

Answer 21

direct stimulation or inhibition of the activity of critical enzymes rapidly alters pathway activity, occurs after the enzyme has been synthesized
irreversible (cleavage) and reversible (allosteric regulation, covalent modification)

Question 22

allosteric enzymes

Answer 22

an enzyme whose activity is altered by the noncovalent binding of a small molecule (allosteric effector) at a regulatory site separate from the catalytic site; effector binding prompts a conformational change in the enzyme’s catalytic site, causing enzyme activation or inhibition

Question 23

covalent modification of enzymes

Answer 23

reversible on and off switch, usually occurs through the addition or removal of a particular chemical group
advantages:
- respond to more stimuli in varied/sophisticated ways
- regulation of enzymes that catalyze covalent modification adds second level of regulation

Question 24

feedback inhibition/end product inhibition

Answer 24

ensures balanced production of a pathway end product
pacemaker enzyme - catalyzes the slowest or rate-limiting reaction in the pathway
- each end product regulates its own branch of the pathway
- each end product regulates the initial pacemaker enzyme
isoenzymes - different forms of an enzyme that catalyze the same reaction