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Metabolism
the sum of all the chemical processes carried out by living organisms
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anabolism
reactions that require energy to synthesize complex molecules from simpler ones
needed for growth, reproduction, and repair of cellular structures
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catabolism
reactions that release energy by breaking complex molecules into simpler ones that can then be reused as building blocks
provides an organism with energy for its life processes, including movement, transport, and the synthesis of complex molecules (anabolism)
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electron transfer
allows energy to be captured in high-energy bonds in ATP and similar molecules
found in all catabolic reactions
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oxidation
the loss or removal of electons
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reduction
the gain of electrons
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heterotrophy
other-feeding
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autotrophs
use carbon dioxide to synthesize organic molecules
photosynthesis
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photoautotrophs
obtain energy from light
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chemoautotrophs
obtain energy from oxidizing simple inorganic substances such as sulfides and nitrites
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heterotrophs
get their carbon from ready-made organic molecules, which they obtain from other organisms, living or dead
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photoheterotrophs
obtain chemical energy from light
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chemoheterotrophs
obtain chemical energy from breaking down ready-made organic compounds
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glycolysis
oxidation of glucose to pyruvic acid
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fermentation
conversion of pyruvic acid to ethyl alcohol, lactic acid, or other organic compounds
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aerobic respiration
oxidation of pyruvic acid to carbon dioxide and water
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glycolysis equation
C6H12O6 + 6O2 -----> 6CO2 + 6H2O + energy
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photosynthesis equation
6CO2 + 6H2O -------> C6H12O6 + 6O2
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metabollic pathway
a series of chemical reactions in which the product of one reaction serves as the substrate from the next
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Catabolic pathways
capture energy in a form cells can use
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Anabolic pathways
make the complex molecules that form the structure of cells, enzymes, and other molecules that control cells
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The links that couple catabolic catabolic and anabolic pathways
ATP molecules
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enzymes
act as catalysts in biochemical reactions
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activation energy
energy required to start a reaction
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Why lower activation energy in cells?
cells would raise the temperature enough to denature proteins and evaporate liquids
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substrate
the substance on which the enzyme acts
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The effect of enzymes on activation energy
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specificity
catalyze only one type of reaction, and most act on only one particular substrate
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endoenzymes
intracellular enzymes, act within the cell that produced them
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exoenzymes
extracellular enzymes, are synthesized in a cell but cross the cell membrane to act in the periplasmic space or in the cell's immediate environment
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apoenzyme
protein portion of an enzyme
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coenzyme
a nonprotein organic molecule bound to or loosely associated with an enzyme
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many coenzymes are synthesized from __________.
vitamins
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coenzyme A is made from _________.
pantothenic acid
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NAD is made from ____________.
niacin
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cofactor
usually an inorganic ion, such as magnesium, zinc, or manganese
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competitive inhibitor
competes with the substrate from the active site
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noncompetitive inhibitors
attach to the enzyme at an allosteric site,which is a site other than the active site
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feedback inhibition
a kind of reversible non-competitive inhibition that regulates the rate of many metabolic pathways
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factors that affect the rate of enzyme reactions:
- 1) Temperature
- 2) pH
- 3) concentrations of substrate, product, and enzyme
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enzyme activity
the rate at which an enzyme catalyzes a reaction
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four important events of glycolysis:
- 1) Substrate-level phosphorylation (the transfer of phosphte froups from ATPs to glucose)
- 2)Breaking of a six-carbon molecule (glucose) into two three-carbon molecules
- 3)The transfer of two electrons to the coenzyme NAD
- 4)The capture of energy in ATP
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phosphorylation
the addition of a phosphate group to a molecule, often from ATP
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end products of glycolysis
two molecules of pyruvic acid and two molecules of reduced NAD (NADH)
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metabolic pathway of Bacillus subtilis and E. coli:
pentose phosphate pathway
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fermentation
pyruvic acid is subsequently metabolized in the absence of oxygen
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homolactic acid fermentation
pyruvic acid is converted directly to lactic acid, using electrons from reduced NAD
used in making cheeses
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alcoholic fermentation
carbon dioxide is released from pyruvic acid to form the intermediate acetaldehyde, which is quickly reduced to ethyl alcohol by electrons from reduced NAD
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the Krebs cycle (citric acid cycle)
metabolizes two-carbon units called acetyl groups to CO2 and H2O
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pyruvic acid must be converted to __________ to enter the Krebs cycle
acetyl CoA
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Significate events of the Krebs cycle:
- -the oxidation of carbon
- -the transfer of electrons to coenzymes
- -the substrate-level energy capture
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electron transport
the process leading to the transfer from substrate to O2
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electron transport chain functions:
- 1) accepting electrons from an electron donor and transferring them to an electron acceptor
- 2) conserving for ATP synthesis some of the energy released during the electron transfer
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oxidative phosphorylation
energy is captured in high-energy bonds as Pi combines with ADP to form ATP
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chemiosmosis
ADP is converted to ATP by a large ATP-synthesizing complex called ATP synthase
a major contribution to the understanding of how ATP is formed during the electron transport
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ATP produced in oxidative phosphorylation
34 ATPs
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___________ as much energy is captured in aerobic metabolism as in fermentation.
19 times!
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light reactions
- Light strikes the freen pigment chlorophyll a in thylakoids of chloroplasts. Electrons in the chlorophyll become excited (raised to a higher energy level).
- Products= ATP and NADPH
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dark reactions (carbon fixation)
occurs in the stroma of chloroplasts
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amphibolic pathways
can yield enegy or building blocks for synthetic reactions
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porins
form channels through the outer membrane
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bioluminescence
the ability of an organism to emit light (appears to be a by-product of aerobic metabolism)
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