Ch 22 Bio Exam 4 Flashcards
Coenzyme A (CoA) is made up of several components:
- pantothenic acid (vitamin B5)
- phosphorylated ADP
- aminoethanethiol
_______ is 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
____ is 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 oxidized form of NAD+ undergoes _____ when a carbon atom in the nicotinamide ring reacts with 2H (two hydrogen ions and two electrons), leaving one H+.
- reduction
_______ is used in anabolic reactions, such as lipid and nucleic acid synthesis.
- NADP+, nicotinamide adenine dinucleotide phosphate
is similar to NAD+ except that a 2′ OH group is replaced by a phosphate group
- 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 ________ made from riboflavin (vitamin B2) and adenosine diphosphate is reduced to FADH2 by adding two hydrogen atoms.
- coenzyme FAD (flavin adenine dinucleotide)
______ participates in reactions that produce a carbon-carbon double bond.
- FAD, flavin adenine dinucleotide
FAD, flavin adenine dinucleotide is reduced to FADH2 with the aide of enzyme ______.
- succinate dehydrogenase
Important functions of ______ include
preparation of small acyl groups such as acetyl for reactions with enzymes and production of the energy-rich thioester acetyl CoA.
- coenzyme A
Glycolysis Reaction 1
- Phosphorylation (ATP - ADP)
- a phosphate group is transferred from ATP to glucose.
- glucose-6-phosphate and ADP are produced.
- the enzyme hexokinase catalyzes the reaction.
Glycolysis Reaction 2
- Isomerization ( G6P and F6P are isomers)
- glucose-6-phosphate, the aldose from reaction 1, is converted to fructose-6-phosphate.
- the isomerization is catalyzed by the enzyme phosphoglucose isomerase
Glycolysis Reaction 3
- phosphorylation
- 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.
Glycolysis Reaction 4
- cleavage,
- fructose-1,6-bisphosphate is split into two three-carbon phosphate isomers.
- the enzyme aldolase produces dihydroxyacetone phosphate and glyceraldehyde-3-phosphate.
Glycolysis Reaction 5
- isomerization,
- 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.
Glycolysis Reaction 6
- oxidation and phosphorylation,
- 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.
Where are NADH molecules produced during Glycolysis?
- # 2 NADH in reaction 6 of glycolysis
Where are ATP molecules produced during Glycolysis?
- # 2 in reaction 7 of glycolysis
- # 2 in reaction 10 of glycolysis
Creating a net gain of 2 ATP overall
Glycolysis Reaction 7
- phosphate transfer
- 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.
Glycolysis Reaction 8
- isomerization
- 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.
Glycolysis Reaction 9
- dehydration
- each phosphoglycerate molecule undergoes dehydration by the enzyme enolase.
- two high-energy phosphoenolpyruvate molecules are produced.
Glycolysis Reaction 10
- phosphate transfer
- 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 muscles and kidneys, the intermediate monosaccharide fructose is phosphorylated to fructose-6-phosphate, which enters glycolysis in _____.
- reaction 3
Intermediate monosaccharide Galactose reacts with ATP to yield glucose-1-phosphate, which is converted to _______, which then enters glycolysis at ______.
- glucose-6-phosphate
- reaction 2
Glycolysis is regulated by three enzymes.
In reaction 1, _____ is inhibited by high levels of glucose-6-phosphate, which prevents the phosphorylation of glucose.
In reaction 3,______, an allosteric enzyme, is inhibited by high levels of ATP and activated by high levels of ADP and AMP.
In reaction 10, ______, another allosteric enzyme, is inhibited by high levels of ATP or acetyl CoA.
- hexokinase
- phosphofructokinase
- pyruvate kinase
______, is an important coenzyme required in the anabolic pathways, including the biosynthesis of nucleic acids, cholesterol, and fatty acids in the liver and fat cells.
- NADPH, the reduced form of NADP+
The ______ is an alternative pathway for the oxidation of glucose and produces the coenzyme NADPH and five-carbon pentoses.
- pentose phosphate pathway
The pentose phosphate pathway begins with glucose-6-phosphate from reaction 1 in glycolysis, which is converted to ____ and requires two NADP+.
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.
In a series of reactions, three ribose-5-phosphate molecules are converted to two hexose molecules and one triose molecule.
- ribulose-5-phosphate
- phosphopentose isomerase
- 2 Fructose-6-phosphate + glyceraldhyde-3-phosphate
Under aerobic conditions (oxygen present), where is pyruvate oxidized?
What coenzyme oxidizes it?
What other enzyme is involved in the final form of the reaction?
- moves from the cytosol into the mitochondria to be oxidized further.
- is oxidized when a carbon atom is removed as CO2 as the coenzyme NAD+ is reduced to NADH.
- Pyruvate dehydrogenase, resulting two-carbon acetyl group is attached to CoA, producing acetyl CoA, an important intermediate in many metabolic pathways.
How is pyruvate reduced to lactate under anaerobic conditions?
- pyruvate is reduced to lactate and NAD+ by lactate dehydrogenase.
- occurs in anaerobic microorganisms, such as yeast.
- decarboxylates pyruvate to acetaldehyde, which is then reduced to ethanol, regenerating NAD+.
- Fermentation
During glycogenesis what enzyme converts glucose 6 p to glucose 1 p in reaction one?
- the enzyme phosphoglucomutase catalyzing the shift of a phosphate group between carbon atoms.
During reaction 2 of glycogenesis, g1p is converted to ____ by what enzyme?
- UDP - glucose
- pyrophosphorylase and the addition of UMP.
During reaction 3 of glycogenesis, what happens to UDP - glucose?
- 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.
- glucose molecules are removed from the glycogen chain.
- glucose molecules are phosphorylated by glycogen phosphorylase to yield glucose-1-phosphate.
- glycogenolysis, reaction 1
- glycogen phosphorylase 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.
- glycogenolysis, reaction 2
- isomerization, the glucose-1-phosphate molecules are converted to glucose-6-phosphate molecules that enter the glycolysis pathway at reaction 2.
- glycogenolysis, reaction 3
- dephosphorylation, cells in the liver and kidneys have a glucose-6-phosphatase that hydrolyzes the glucose-6-phosphate to yield free glucose.
- glycogenolysis, reaction 4
To protect the brain, hormones with opposing actions control blood glucose levels such as
- glucagon,
- insulin, and
- epinephrine.
