Exam 4 - Chp. 22 - Metabolism Flashcards
that break down large, complex molecules to provide energy and smaller molecules.
catabolic reactions
that use ATP energy to build larger molecules.
anabolic reactions
Digestion and hydrolysis break down large molecules to smaller ones that enter the bloodstream
Stage 1 Catabolic reactions
Within the cells, degradation breaks down molecules to two- and three-carbon compounds
Stage 2 Catabolic reactions
Oxidation of small molecules in the citric acid cycle and electron transport provides ATP energy.
Stage 3 Catabolic reaction
In the three stages of catabolism, large molecules from foods are digested and degraded to provide smaller molecules that can be ___ to produce energy.
oxidized
Cells in plants and animals are known as ___ cells, which have a nucleus that contains DNA.
eukaryotic
a cell membrane separates the materials inside the cell from the aqueous environment surrounding the cell.
the cell nucleus contains the genes that control DNA replication and protein synthesis.
the cytosol, or fluid part of the cell, contains electrolytes and enzymes that catalyze chemical reactions in the cell.
Animal cells
The ATP molecule, composed of ___, hydrolyzes to form ADP and AMP along with a release of energy.
the base adenine, a ribose sugar, and three phosphate groups
The hydrolysis of ATP to ADP releases __ kcal (31 kJ) per mole
7.3
The hydrolysis of ADP to AMP releases __ kcal (31 kJ) per mole
7.3
When ATP __, the energy released can be used to drive an energy-requiring reaction
hydrolyzes
used in anabolic reactions
the energy-storage molecule
combined with energy-requiring reactions
ATP
hydrolysis products
ADP + Pi
Coenzyme A (CoA) is made up of several components: pantothenic acid (vitamin B5), phosphorylated ADP, and ___
aminoethanethiol
Metabolic reactions that extract energy from food involve both ___ reactions
oxidation and reduction
involves the loss of hydrogen or electrons by a substance or an increase in the number of bonds to oxygen
Oxidation
gain of hydrogen ions and electrons or a decrease in the number of bonds to oxygen
Reduction
In both types of reactions, coenzymes are required to carry the ___ and electrons from or to the reacting substrate.
hydrogen ions
A coenzyme that gains hydrogen ions and electrons is __, whereas a coenzyme that loses hydrogen ions and electrons to a substrate is __
reduced
oxidized
an important coenzyme in which the vitamin niacin provides the nicotinamide group, which is bonded to ribose and the nucleotide adenosine diphosphate (ADP).
NAD+, nicotinamide adenine dinucleotide,
required in dehydrogenation reactions that produce carbon–oxygen double bonds, such as the oxidation of alcohols to aldehydes and ketones
NAD+, nicotinamide adenine dinucleotide
The ___ form of NAD+ undergoes reduction when a carbon atom in the nicotinamide ring reacts with 2H (two hydrogen ions and two electrons), leaving one H+.
oxidized
used in anabolic reactions, such as lipid and nucleic acid synthesis
NADP+, nicotinamide adenine dinucleotide phosphate
similar to NAD+ except that a 2′ OH group is replaced by a phosphate group
NADP+, nicotinamide adenine dinucleotide phosphate
reduced to form NADPH
NADP+, nicotinamide adenine dinucleotide phosphate
contains ADP and riboflavin (vitamin B2).
FAD, flavin adenine dinucleotide,
undergoes reduction when the two nitrogen atoms in the flavin part of the FAD coenzyme react with two hydrogen atoms (2H+ + 2 e−), reducing it to FADH2.
FAD, flavin adenine dinucleotide
The coenzyme FAD (flavin adenine dinucleotide) made from riboflavin (vitamin B2) and adenosine diphosphate is reduced to FADH2 by adding ____
two hydrogen atoms.
participates in reactions that produce a carbon-carbon double bond.
FAD, flavin adenine dinucleotide,
reduced to FADH2 with the aide of enzyme succinate dehydrogenase
FAD, flavin adenine dinucleotide,
____ is derived from a phosphorylated ADP and pantothenic acid bonded by an amide bond to aminoethanethiol, which contains the —SH reactive part of the molecule.
Coenzyme A
preparation of small acyl groups such as acetyl for reactions with enzymes.
Important functions of coenzyme A include
production of the energy-rich thioester acetyl CoA.
Important functions of coenzyme A include
coenzyme used in oxidation of carbon-oxygen bonds
NAD+
reduced form of flavin adenine dinucleotide
FADH2
used to transfer acetyl groups
coenzyme A
contains riboflavin
FAD, FADH2
the coenzyme after C = O bond formation
NADH + H+
Carbohydrate digestion begins in the mouth, where ___ breaks down polysaccharides into smaller polysaccharides (dextrins), maltose, and some glucose
salivary amylase
In the stomach, the partially digested starches enter the acidic environment, where the ___ stops further carbohydrate digestion
low pH
In the small intestine where the pH is about 8,
enzymes produced in the pancreas ____ the remaining dextrins to maltose and glucose
hydrolyze
In the small intestine where the pH is about 8, enzymes produced in the mucosal cells that line the small intestine ___ maltose, lactose, and sucrose
hydrolyze
In the small intestine where the pH is about 8, the resulting ___ are absorbed through the intestinal wall into the bloodstream
monosaccharides
In the liver, hexoses fructose and galactose are converted to ___, the primary energy source for muscle contractions, red blood cells, and the brain.
glucose
Glucose in the bloodstream enters our cells, where it undergoes ___ in a pathway called glycolysis.
degradation
Glucose obtained from the digestion of polysaccharides is degraded in glycolysis to ___.
pyruvate
takes place in the cytosol of the cell.
is a metabolic pathway that uses glucose, a digestion product.
degrades six-carbon glucose molecules to three-carbon pyruvate molecules
Glycolysis
energy is required to add phosphate groups to glucose.
glucose is converted to two three-carbon molecules
Reactions 1–5 of glycolysis
energy is obtained from the hydrolysis of the energy-rich phosphate compounds.
four ATP molecules are synthesized
reactions 6–10 of glycolysis
a phosphate group is transferred from ATP to glucose.
glucose-6-phosphate and ADP are produced.
the enzyme hexokinase catalyzes the reaction
reaction 1, phosphorylation
glucose-6-phosphate, the aldose from reaction 1, is converted to fructose-6-phosphate.
the isomerization is catalyzed by the enzyme phosphoglucose isomerase
reaction 2, isomerization,
hydrolysis of another ATP provides a second phosphate group.
the phosphate group is transferred to fructose-6-phosphate, producing fructose-1,6-bisphosphate.
a second kinase enzyme called phosphofructokinase catalyzes the reaction.
reaction 3, phosphorylation
fructose-1,6-bisphosphate is split into two three-carbon phosphate isomers.
the enzyme aldolase produces dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.
reaction 4, cleavage
dihydroxyacetone phosphate undergoes isomerization catalyzed by triose phosphate isomerase.
a second molecule of glyceraldehyde-3-phosphate is produced, which can be oxidized.
all six carbon atoms from glucose are contained in two identical triose phosphates
reaction 5, isomerization
In reaction 5, isomerization,
_____ undergoes isomerization catalyzed by triose phosphate isomerase.
a second molecule of ____ is produced, which can be oxidized.
all six carbon atoms from glucose are contained in two identical ____.
dihydroxyacetone phosphate
glyceraldehyde-3-phosphate
triose phosphates
the aldehyde group of each glyceraldehyde-3-phosphate is oxidized to a carboxyl group.
NAD+ is reduced to NADH and H+.
a phosphate group is transferred to each of the new carboxyl groups, forming two molecules of 1,3-bisphosphoglycerate.
In reaction 6, oxidation and phosphorylation
In reaction 6, oxidation and phosphorylation, the aldehyde group of each ____ is oxidized to a carboxyl group.
NAD+ is reduced to NADH and H+.
a phosphate group is transferred to each of the new carboxyl groups, forming two molecules of _____
glyceraldehyde-3-phosphate
1,3-bisphosphoglycerate
a phosphate group from each 1,3-bisphosphoglycerate is transferred to two ADP molecules by phosphoglycerate kinase.
two molecules of the high-energy compound ATP are produced.
reaction 7, phosphate transfer
reaction 7, phosphate transfer, a phosphate group from each ____ is transferred to two ADP molecules by phosphoglycerate kinase.
two molecules of the high-energy compound ATP are produced.
1,3-bisphosphoglycerate
two 3-phosphoglycerate molecules undergo isomerization by phosphoglycerate mutase.
the phosphate group is moved from carbon 3 to carbon 2, yielding two molecules of 2-phosphoglycerate.
reaction 8, isomerization
In reaction 8, isomerization, two 3-phosphoglycerate molecules undergo isomerization by ___.
the phosphate group is moved from carbon 3 to carbon 2, yielding two molecules of 2-phosphoglycerate.
phosphoglycerate mutase
each phosphoglycerate molecule undergoes dehydration by the enzyme enolase.
two high-energy phosphoenolpyruvate molecules are produced
reaction 9, dehydration
In reaction 9, dehydration, each ___ molecule undergoes dehydration by the enzyme enolase.
two high-energy phosphoenolpyruvate molecules are produced.
phosphoglycerate
phosphate groups from two phosphoenolpyruvate molecules are transferred by pyruvate kinase to two ADPs, to yield two pyruvates, and two ATPs.
a fourth kinase enzyme transfers a phosphate with ATP production.
In reaction 10, phosphate transfer,
In reaction 10, phosphate transfer, phosphate groups from two ___molecules are transferred by pyruvate kinase to two ADPs, to yield two pyruvates, and two ATPs.
a fourth kinase enzyme transfers a phosphate with ATP production.
phosphoenolpyruvate
two ATP molecules add phosphate to glucose and fructose-6-phosphate.
four ATP molecules are formed in energy generation by direct transfers of phosphate groups to four ADP.
there is a net gain of two ATPs and two NADHs.
glycolysis
Other monosaccharides, such as ___, can enter glycolysis after they are converted to intermediates.
fructose and galactose
In muscles and kidneys, fructose is phosphorylated to ___, which enters glycolysis in reaction 3
fructose-6-phosphate
Galactose reacts with ATP to yield ___, which is converted to glucose-6-phosphate, which then enters glycolysis at reaction 2.
galactose-1-phosphate
In glycolysis reaction 1, __ is inhibited by high levels of glucose-6-phosphate, which prevents the phosphorylation of glucose.
hexokinase
In glycolysis reaction 3, ___, an allosteric enzyme, is inhibited by high levels of ATP and activated by high levels of ADP and AMP
phosphofructokinase
In glycolysis reaction 10, ___, another allosteric enzyme, is inhibited by high levels of ATP or acetyl CoA
pyruvate kinase
In glycolysis reaction 7, phosphate groups from two
____ molecules are transferred to ADP to form two ATPs
1,3-bisphosphoglycerate
In glycolysis reaction 10, phosphate groups from two ____ molecules are used to form two more ATPs.
phosphoenolpyruvate
an alternative pathway for the oxidation of glucose.
produces the coenzyme NADPH and five-carbon pentoses
pentose phosphate pathway
NADPH, the reduced form of NADP+, is an important ___ required in the anabolic pathways, including the biosynthesis of nucleic acids, cholesterol, and fatty acids in the liver and fat cells.
coenzyme
pentose phosphate pathway begins with glucose-6-phosphate from reaction 1 in glycolysis, which is converted to ___ and requires two NADP+.
ribulose-5-phosphate
Ribulose-5-phosphate is isomerized by the catalyst ___ to ribose-5-phosphate, an important component of nucleotides such as ATP, GTP, UTP, NAD+, FAD, and RNA
phosphopentose isomerase
In a series of reactions, three ___ molecules are converted to two hexose molecules and one triose molecule
ribose-5-phosphate
The pentose phosphate pathway converts glucose-6-P to ___, which is needed for the synthesis of DNA and RNA
ribose-5-P
Ribose-5-P can also return to glycolysis as needed.
Lactate is transported to the liver, where it is converted back into
pyruvate.
Under aerobic conditions, oxygen is available to convert ___ to acetyl coenzyme A (acetyl CoA) and CO2.
pyruvate
When oxygen levels are low, pyruvate is reduced to
lactate
Under aerobic conditions (oxygen present), pyruvate
moves from the __into the mitochondria to be oxidized further
cytosol
Under aerobic conditions (oxygen present), ___ is oxidized when a carbon atom is removed as CO2 as the coenzyme NAD+ is reduced
pyruvate
The resulting two-carbon acetyl group is attached to CoA, producing ____, an important intermediate in many metabolic pathways.
acetyl CoA,
Under anaerobic conditions (without oxygen),
pyruvate is reduced to lactate and NAD+ by lactate dehydrogenase.
NAD+ is used to oxidize ___ in the glycolysis pathway, producing a small amount of ATP.
glyceraldehyde-3-phosphate
The accumulation of ___ causes the muscles to tire and become sore. Lactate is subsequently transported to the liver and converted back to pyruvate.
lactate
Under anaerobic conditions, the only ATP production in glycolysis occurs during the steps that ___ ADP directly giving a net gain of only two ATP.
phosphorylate
occurs in anaerobic microorganisms, such as yeast.
decarboxylates pyruvate to acetaldehyde, which is then reduced to ethanol, regenerating NAD+.
Fermentation
During fermentation, enzymes in the yeast convert sugars to glucose and then to ___ and CO2 gas
ethanol
produced during anaerobic conditions
lactate
reaction series that converts glucose to pyruvate
glycolysis
metabolic reactions that break down large molecules to smaller molecules + energy reactions
catabolic
substances that remove or add H atoms in oxidation and reduction reactions
coenzymes
Glycogen storage diseases (GSDs) occur when a defective ___ is involved in a pathway for glycogen storage or degradation.
enzyme
is a polymer of glucose with α(1 -> 4)-glycosidic bonds and multiple branches attached by α(1 -> 6)-glycosidic bonds.
Glycogen
is formed when high levels of glucose-6-phosphate are formed in the first reaction of glycolysis.
Glycogen
not formed when energy stores (glycogen) are full, which means that additional glucose is converted to triacylglycerols and stored as body fat.
Glycogen
metabolic process of converting glucose molecules into glycogen.
Glycogenesis
produces glucose-6-phosphate in reaction 1 of glycolysis.
Glycogenesis
the conversion of glucose-6-phosphate to the isomer glucose-1-phosphate.
the enzyme phosphoglucomutase catalyzing the shift of a phosphate group between carbon atoms.
Glycogenesis: Reaction 1
glucose-1-phosphate is activated before addition to the glycogen chain.
energy is released when pyrophosphorylase catalyzes the reaction.
the high-energy compound UTP transfers UMP to glucose-1-phosphate to give UDP-glucose and pyrophosphate, PPi.
Glycogenesis: Reaction 2
Glycogenesis: Reaction 2, glucose-1-phosphate is activated before addition to the glycogen chain.
energy is released when pyrophosphorylase catalyzes the reaction.
the high-energy compound UTP transfers UMP to glucose-1-phosphate to give ___
UDP-glucose and pyrophosphate, PPi
glycogen synthase catalyzes breaking of the phosphate bond to glucose in UDP-glucose.
glucose is released, forming an α(1 -> 4) glycosidic bond with the end of a glycogen chain.
Glycogenesis: Reaction 3
In glycogenolyis reaction 1, phosphorolysis,
glucose molecules are removed from the glycogen chain.
glucose molecules are phosphorylated by glycogen phosphorylase to yield __
glucose-1-phosphate.
In reaction 2, hydrolysis (α-1,6),
____ cleaves α(1 ,4)-links until only one glucose remains bonded to the main chain.
a debranching enzyme breaks α(1 , 6)-glycosidic bonds so branches of glucose molecules can be hydrolyzed by reaction 1.
glycogen phosphorylase
Glycogenolysis: Reaction 3, isomerization, the glucose-1-phosphate molecules are converted to ___ molecules that enter the glycolysis pathway at reaction 2
glucose-6-phosphate
In glycogenolysis reaction 4, dephosphorylation, cells in the liver and kidneys have a glucose-6-phosphatase that hydrolyzes the glucose-6-phosphate to yield
free glucose.
activated by low levels of blood glucose
converts glucose-1-phosphate to glucose-6-phosphate
glycogenolysis
activated by high levels of glucose-6-phosphate
glucose + UTP UDP-glucose + Ppi
glycogenesis
Glucose is synthesized in the tissues of the ___.
Tissues that use glucose as their main energy source are the brain, skeletal muscles, and red blood cells
liver and kidneys
If our glycogen stores are depleted,
liver cells synthesize glucose by ___.
Glucose is synthesized in the cytosol of the liver cells, and some is synthesized in the kidneys
gluconeogenesis
can supply us with about one day’s requirement of glucose.
is made from glucose, most of which is synthesized in the cytosol of liver cells
Glycogen
To begin gluconeogenesis, carbon atoms from ____ food sources are converted to pyruvate.
noncarbohydrate
To start the synthesis of glucose from pyruvate,
two catalyzed reactions are needed to replace reaction 10 in glycolysis.
_____ uses the energy of ATP hydrolysis to catalyze the addition of CO2 to pyruvate and produce oxaloacetate.
______ converts oxaloacetate to phosphoenolpyruvate.
phosphoenolpyruvate molecules now use enzymes to form fructose-1,6-bisphosphate.
pyruvate carboxylase
phosphoenolpyruvate carboxykinase
The second irreversible reaction in glycolysis is bypassed when ___ cleaves a phosphate group from fructose-1,6-bisphosphate.
fructose-1,6-bisphosphatase
The product fructose-6-phosphate undergoes the reversible reaction 2 of glycolysis to yield
glucose-6-phosphate
In the final irreversible reaction, the phosphate group of glucose-6-phosphate is hydrolyzed by a different enzyme, glucose-6-phosphatase, to form ___.
glucose
Gluconeogenese: The pathway consists of seven reversible reactions of glycolysis and four new reactions that replace the three irreversible reactions
Overall, glucose synthesis requires four ATPs, two GTPs, and two NADHs.
is the flow of lactate and glucose between the muscles and the liver.
occurs when anaerobic conditions occur in active muscle, and glycolysis produces lactate
Cori cycle
operates when lactate moves through the blood stream to the liver, where it is oxidized back to pyruvate.
converts pyruvate to glucose, which is carried back to the muscles
Cori cycle
not utilized when the diet is high in carbohydrates.
Gluconeogenesis
very active when the diet is low in carbohydrates.
Gluconeogenesis
When conditions in a cell favor glycolysis, there is no synthesis of
glucose
When the cell requires the synthesis of glucose, ___is turned off.
glycolysis
the synthesis of glucose from noncarbohydrates
gluconeogenesis
the breakdown of glycogen into glucose
glycogenolysis
the oxidation of glucose to two pyruvate
glycolysis
the synthesis of glycogen from glucose
glycogenesis
