Chapter 7: Metabolism Flashcards
- all chemical reactions that take place in cells to break down or build molecules
metabolism
two types of metabolic process
- anabolic
- catabolic
- a series of linked reactions, each catalyzed by a specific enzyme.
- produce energy and cellular compounds.
Metabolic Pathway
When we eat food, the polysaccharides, lipids, and proteins are digested to smaller molecules that can be absorbed into the cells of our body. As the glucose, fatty acids, and amino acids are broken down further, energy is __.
released
Because we do not use all the energy from our foods at one time, we store energy in the cells as high-energy __, ATP. – later broken down obtain energy to do work in our bodies: (4)
- adenosine triphosphate
- contracting muscles
- synthesizing large molecules,
- sending nerve impulses
- moving substances across cell membranes
break down large, complex molecules to provide energy and smaller molecules.
catabolic reactions
use ATP energy to build larger molecules.
anabolic reactions
anabolic reactions (__) - muscle contraction, transport, and synthesis of cellular compounds
–> __ + __ (__)
–> catabolic reactions (__) - oxidation of carbohydrates, fats, and proteins
~~> __ + __ + __
–> __ (__)
- energy requiring
- ADP + Pi (energy used)
- energy producing
- CO2 + H2O + NH3 (ammonia)
- ATP (energy stored)
Stages of Metabolism
Catabolic reactions are organized as:
Stage 1: Digestion and hydrolysis
Stage 2: Degradation
Stage 3: Oxidation
Stage 1 of catabolic reaction
Digestion and hydrolysis break down large molecules to smaller ones that enter the bloodstream.
Stage 2 of catabolic reaction
Degradation breaks down molecules to two- and three-carbon compounds.
Stage 3 of catabolic reaction
Oxidation of small molecules in the citric acid cycle and electron transport provide ATP energy (electrons are carried by NADH and FADH2)
Stage 3: As long as the cells have oxygen, the __ and __ from the reduced coenzymes are transferred to electron transport to synthesize ATP.
- hydrogen ions
- electrons
Separates the contents of a cell from the external environment and contains structures that communicate with other cells
cell membrane
Consists of the cellular contents between the cell membrane and nucleus
cytoplasm
Fluid part of the cytoplasm that contains enzymes for many of the cell’s chemical reactions
cytosol
Contains the structures for the synthesis of ATP from energy-releasing reactions
mitochondrion
Contains genetic information for the replication of DNA and the synthesis of protein
nucleus
Site of protein synthesis using mRNA templates
Ribosome
rough type processes proteins for secretion and synthesizes phospholipids; smooth type synthesizes fats and steroids
endoplasmic reticulum
modifies and secretes proteins from the endoplasmic reticulum and synthesizes glycoproteins and cell membranes
Golgi complex
contain hydrolytic enzymes that digest and recycle old cell structures
lysosomes
▪ Is the energy form stored in cells.
▪ Is obtained from the oxidation of food.
Adenosine triphosphate (ATP)
ATP consists of:
adenine (nitrogen base), a ribose sugar, and three phosphate groups.
ATP requires __ to convert __
- 7.3 kcal/mol (or 31 kJ/mol)
- ADP + Pi to ATP
The hydrolysis of ATP to ADP releases __. Give formula
- 7.3 kcal (31 kJ)/mole
- ATP → ADP + Pi + 7.3 kcal/mol (31 kJ/mol)
The hydrolysis of ADP to AMP releases __. Give formula
- 7.3 kcal (31 kJ)/mole
- ADP → AMP + Pi + 7.3 kcal/mol (31 kJ/mol)
low energy bond
phosphate ester bond
(found between ribose and first phosphate)
high energy bond
phospho anhydride bonds
(found in second and third phosphate)
the energy-storage molecule, links energy- producing reactions in the cells
ATP
Used in anabolic reactions.
ATP
The energy-storage molecule.
ATP
Coupled with energy-requiring reactions.
ATP
Hydrolysis products of ATP
ADP + Pi
- Several metabolic reactions that extract energy from our food involve __.
- In chemistry, __ is often associated with the loss of H atoms, whereas __ is associated with the gain of H atoms. Often, we represent two H atoms as two hydrogen ions (2H+) and two electrons (2 e̶ ).
- oxidation and reduction reactions
- oxidation
- reduction
In both oxidation and reduction, __ are required to carry the hydrogen ions and electrons from or to the reacting substrate.
- coenzymes
characteristics of oxidation
- loss of electrons (e-)
- loss of hydrogen (H or H+ and e-)
- gain of oxygen
- release of energy
characteristics of reduction
- gain of electrions (e-)
- gain of hydrogen (H or H+ and e-)
- loss of oxygen
- input of energy
NAD+
nicotinamide adenine dinucleotide
- participates in reactions that produce a carbon-oxygen double bond (C=O)
- Is reduced when an oxidation provides 2H+ and 2e-
NAD+ (nicotinamide adenine dinucleotide)
NAD+ participates in reactions that produce a __
carbon-oxygen double bond (C=O)
NAD+ is reduced when an oxidation provides __ and __
- 2H+
- 2e-
NAD+ contains
ADP, ribose, and nicotinamide
NAD+ reduces to __ when the nicotinamide group accepts H+ and 2e-.
NADH
Coenzyme FAD
flavin adenine dinucleotide
▪ Participates in reactions that produce a carbon-carbon double bond (C=C).
▪ Is reduced to FADH2
FAD (flavin adenine dinucleotide)
Oxidation of FAD
—CH2—CH2— –>
—CH=CH— + 2H+ + 2e-
Oxidation of NAD+
CH3—CH2—OH –>
O
II
CH3—C—H + 2H+ + 2e-
Reduction of NAD+
NAD+ + 2H+ + 2e- –>
NADH + H+
Reduction of FAD
FAD + 2H+ + 2e- –>
FADH2
Coenzyme FAD contains
ADP and riboflavin (vitamin B2)
undergoes reduction when the 2 nitrogens in the flavin part react with two hydrogen atoms (2H+ + 2e-)
Coenzyme FAD
Coenzyme FAD undergoes reduction when the __ in the __ part react with two hydrogen atoms (2H+ + 2e-)
- 2 nitrogens
- flavin
▪ Consists of pantothenic acid (vitamin B5), phosphorylated ADP, and amino ethanethiol
Coenzyme A
▪ Activates acyl groups such as the two-carbon acetyl group for transfer.
Coenzyme A
Coenzyme A contains
- pantothenic acid (vitamin B5)
- phosphorylated ADP
- aminoethanethiol
Coenzyme A activates acyl groups such as the __ for transfer.
two-carbon acetyl group
formulation of acyl group formula
acetyl group + coenzyme A –> acetyl coA (thioester)
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+
the main energy source for the brain, skeletal muscles, and red blood cells.
Glucose
Stages in the digestion of carbohydrates
Stage 1: the digestion of carbohydrates
Stage 2: Glycolysis
Stage 3: Citric acid cycle
Begins in the mouth where salivary amylase breaks down polysaccharides to smaller polysaccharides (dextrins), maltose, and some glucose
digestion of carbohydrates (stage 1)
Stage 1, digestion of carbohydrates continues in the small intestine where __ hydrolyzes __ to __ and __.
- pancreatic amylase
- dextrins
- maltose; glucose
Hydrolyzes __, __, and __ to monosaccharides, mostly glucose, which enter the __ for transport to the cells.
- maltose; lactose; sucrose
- bloodstream
enzymes produced in the __ that line the small intestine hydrolyze maltose as well as lactose and sucrose.
- mucosal cells
The __ carries the monosaccharides to the liver, where fructose and galactose are converted to __.
- bloodstream
- glucose
▪ Is a metabolic pathway that uses glucose, a digestion product.
▪ Degrades glucose (6C) molecules to pyruvate (3C) molecules.
▪ Is an anaerobic (no oxygen) process.
glycolysis
two phases of glycolysis
- energy-investing phase
- energy-generating phase
▪ Energy is required to add phosphate groups to glucose.
▪ Glucose is converted to two three-carbon molecules.
reactions 1-5 of glycolysis
reaction 1-5 of glycolysis:
glucose –(___)–> (ATP to ADP)
glucose-6-phosphate –(__)–>
fructose-6-phosphate –(__)–> (ATP to ADP)
fructose-1,6-bisphosphate –(__)–>
–> dihydroxyacetone phosphate
(___)
–> glyceraldehyde-3-phosphate
- hexokinase
- phospholucoisomerase
- phosphofructokinase
- fructose-1,6-bisphosphate aldolase
- triosephosphate isomerase
The fourth step in glycolysis:
__ catalyzes the reversible conversion of the six-carbon glycolytic enzyme fructose 1,6-bisphosphate into two three-carbon intermediates __ and __
- fructose 1,6-bisphosphate aldolase (FBA)
- glyceraldehyde 3-phosphate (G3P)
- dihydroxyacetone phosphate (DHAP)
▪ Sugar phosphates are cleaved to triose phosphates.
▪ Four ATP molecules are produced.
reactions 6-10 of glycolysis
reactions 1-6 of glycolysis:
glyceraldehyde-3-phosphate –(__)–>
(__ + __ to __+__)
2 - 1,3-bisphosphoglycerate –(__)–> (ADP to ATP)
2 - 3-phosphoglycerate –(__)–>
2 - 2-phosphoglycerate –(__)–> (H2O released)
phosphoenolpyruvate –(__)–> (ADP to ATP)
2 - pyruvate
- glyceraldehyde-3-phosphate-dehydrogenase
(2 Pi + 2NAD+ to 2NADH+ 2H+) - phosphoglycerate kinase
- phosphoglycerate mutase
- enolase
- pyruvate kinase
Energy-Investing Reactions 1 to 5. Name each reaction
Reaction 1 Phosphorylation
Reaction 2 Isomerization
Reaction 3 Phosphorylation
Reaction 4 Cleavage
Reaction 5 Isomerization
Energy-Generating Reactions 6 to 10. Name each reaction
Reaction 6 Oxidation and Phosphorylation
Reaction 7 Phosphate Transfer
Reaction 8 Isomerization
Reaction 9 Dehydration
Reaction 10 Phosphate Transfer
What reaction? In the initial reaction, a phosphate group from ATP is added to glucose to form glucose-6-phosphate and ADP
Reaction 1 Phosphorylation
What reaction? The glucose-6-phosphate, the aldose, undergoes reaction to fructose-6-phosphate, which is a ketose.
Reaction 2 Isomerization
What reaction? The hydrolysis of another ATP provides a second phosphate group, which converts fructose-6 phosphate to fructose-1,6-bisphosphate. The word bisphosphate shows that the two phosphate groups are on different carbons in fructose and are not connected.
Reaction 3 Phosphorylation
What reaction? Fructose-1,6-bisphosphate is split into two three-carbon phosphate isomers: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
Reaction 4 Cleavage
What reaction? Because dihydroxyacetone phosphate is a ketone, it cannot undergo further oxidation. However, it undergoes reaction to provide a second molecule of glyceraldehyde 3-phosphate, which can be oxidized. Now all six carbon atoms from glucose are contained in two identical triose phosphates.
Reaction 5 Isomerization
What reaction? The aldehyde group of each glyceraldehyde-3-phosphate is oxidized to a carboxyl group, while the coenzyme NAD+ is reduced to NADH and H+. A phosphate group (Pi) adds to each of the new carboxyl groups to form two molecules of the high-energy compound 1,3-bisphosphoglycerate.
Reaction 6 Oxidation and Phosphorylation
What reaction? A phosphate group from each 1,3-bisphosphoglycerate is transferred to two ADP molecules, yielding two molecules of the high-energy compound ATP. At this point in glycolysis, two ATP are produced, which balance the two ATP consumed in reactions 1 and 3.
Reaction 7 Phosphate Transfer
What reaction? Two 3-phosphoglycerate molecules undergo a reaction, which moves the phosphate group from carbon 3 to carbon 2, yielding two molecules of 2-phosphoglycerate.
Reaction 8 Isomerization
What reaction? Each of the phosphoglycerate molecules undergoes a reaction (loss of water), producing two molecules of phosphoenolpyruvate, a high-energy compound.
Reaction 9 Dehydration
What reaction? In a second direct phosphorylation, phosphate groups from two phosphoenolpyruvate molecules are transferred to two ADP to form two pyruvate and two ATP.
Reaction 10 Phosphate Transfer
A phosphate group is transferred to ADP to form ATP
phosphorylation
3-Phosphoglycerate is converted to 2-phosphoglycerate.
isomerization
Water is removed from 2-phosphoglycerate.
dehydration
Summary: In glycolysis,
▪ __ add phosphate to glucose and fructose-6-phosphate (Steps 1 and 3).
▪ __ are formed in energy-generation by direct transfers of phosphate groups to four ADP (Steps 7 and 10; formation of 3 phosphoglycerate and pyruvate).
▪ There is a net gain of __ and __.
- Two ATP
- Four ATP
- 2 ATP
- 2 NADH
Regulation in glycolysis
Glycolysis has three key regulatory steps (1, 3, and 10) catalyzed by __, __, and __. These have large __ values and are essential to drive the overall flux to pyruvate. These regulatory steps are essentially __.
- hexokinase
- phosphofructokinase
- pyruvate kinase
- negative ΔG
- irreversible
Glycolysis is regulated by three enzymes:
- Hexokinase
- Phosphofructokinase
- Pyruvate kinase
Glycolysis: Reaction 1 Hexokinase is inhibited by __, which prevents the phosphorylation of glucose.
- high levels of glucose-6-phosphate
Glycolysis: Reaction 3 Phosphofructokinase, an allosteric enzyme, is inhibited by __ and activated by high levels of ADP and AMP. If cells have plenty of ATP, glycolysis slows down.
- high levels of ATP
Glycolysis: Reaction 10 Pyruvate kinase, another allosteric enzyme is inhibited by __.
high levels of ATP or acetyl CoA
In glycolysis, what compounds provide phosphate groups for the production of ATP?
- In reaction 7, phosphate groups from two 1,3-bisphosphoglycerate molecules are transferred to ADP to form two ATP.
- In reaction 10, phosphate groups from two phosphoenolpyruvate molecules are used to form two more ATP.
readily taken up in the muscle and liver
fructose
In the muscles, fructose is converted to __, entering glycolysis at step 3.
- fructose-6-phosphate
In the liver, fructose is converted to the __ used in step 5.
trioses
Fructose that enters a cell flows from reaction __ to __.
5 to 10
Fructose uptake by the cells is not regulated by __: all fructose in the bloodstream is forced into __.
- insulin
- catabolism
Glycolysis is regulated at step __. The triose products created in the liver provide an excess of reactants that create excess __ and __ that, if not required for energy by the cells, is converted to __.
- 3
- pyruvate
- acetyl CoA
- fat
pathways for pyruvate: conditions
- aerobic conditions (in humans, animals , and some microorganisms) - Acetyl CoA
- anaerobic conditions (in humans, animals, and some microorganisms) - Lactate
- anaerobic conditions (in some microorganisms) - ethanol
under what condition?
▪ Three-carbon pyruvate is decarboxylated.
▪ Two-carbon acetyl CoA and CO2 are produced.
▪ Occurs in the mitochondria
Under aerobic conditions (oxygen present)
Pyruvate is converted to __ and __ under aerobic conditions when oxygen is plentiful. The __ is oxidized back to __ to allow glycolysis to continue.
- acetyl CoA
- NADH
- NADH
- NAD+
under what condition?
▪ Pyruvate is reduced to lactate.
▪ NAD+ is produced and is used to oxidize more glyceraldehyde-3-phosphate in the glycolysis pathway, which produces a small but needed amount of ATP.
▪ Occurs in the cytosol
Under anaerobic conditions (without oxygen)
Lactate in muscles, during strenuous exercise: what happens (4)
▪ Oxygen in the muscles is depleted.
▪ Anaerobic conditions are produced.
▪ Lactate accumulates.
▪ Muscles tire and become painful.
anaerobic lactate formation allows for “__” of NAD+, providing the NAD+ needed for __ of glycolysis
- recycling
- step 6
▪ Occurs in anaerobic microorganisms such as yeast.
▪ Decarboxylates pyruvate to acetaldehyde, which is reduced to ethanol.
▪ Regenerates NAD+ to continue glycolysis.
Fermentation
Fermentation occurs in __ such as yeast.
▪ Decarboxylates pyruvate to __, which is
reduced to __.
▪ Regenerates __ to continue glycolysis.
- anaerobic microorganisms
- acetaldehyde
- ethanol
- NAD+
Fermentation: The first step in the conversion of pyruvate to ethanol is a __ reaction to produce __.
- decarboxylation
- acetaldehyde
Fermentation: The second step involves __ to produce ethanol.
acetaldehyde reduction
Produced during anaerobic conditions.
Lactate
Reaction series that converts glucose to pyruvate.
Glycolysis
Metabolic reactions that break down large molecules to smaller molecules energy.
Catabolic reactions
Substances that remove or add H atoms in oxidation and reduction reactions.
Coenzymes
What stage in the pathway for pyruvate?
▪ Operates under aerobic conditions only.
▪ Oxidizes the two-carbon acetyl group in acetyl CoA to 2CO2.
▪ Produces reduced coenzymes NADH and FADH2 and one ATP directly.
citric acid cycle (stage 3)
What does the citric acid cycle oxidize?
two-carbon acetyl group in acetyl CoA to 2CO2.
What does the citric acid cycle produce?
reduced coenzymes NADH and FADH2 and one ATP.
In the citric acid cycle,
▪ Acetyl (2C) bonds to oxaloacetate (4C) to form __.
▪ Oxidation and decarboxylation reactions convert citrate to __.
▪ Oxaloacetate bonds with another acetyl to repeat the cycle.
- citrate (6C).
- oxaloacetate
In the citric acid cycle,
▪ __ bonds to __ to form citrate (6C).
▪ __ and __
reactions convert citrate to oxaloacetate.
▪ __ bonds with another acetyl to repeat the cycle.
- Acetyl (2C)
- oxaloacetate (4C)
- Oxidation
- decarboxylation
- Oxaloacetate
the cictric acid cycle
acetyl CoA ->
PART 1 __ (CO2) ->
__ (CO2) ->
PART 2 __ -> __ (cycle repeats)
- citrate
- α-ketoglutarate
- Succinyl CoA
- oxaloacetate
8 reactions in the citric acid cycle (in order)
- condensation (Acetyl CoA to citrate)
- isomeration (Citrate to isocitrate)
- oxidative decarboxylation (isocitrate to α-ketoglutarate)
- oxidative decarboxylation (α-ketoglutarate to succinyl CoA)
- phosphorylation (Succinyl CoA to succinate)
- oxidation (succinate to fumarate)
- hydration (fumarate to malate)
- oxidation (oxacelate to acetyl CoA)
Citric Acid Acid
1. condensation (__ to __)
2. isomeration (__ to __)
3. oxidative decarboxylation (__ to __)
4. oxidative decarboxylation (__ to __)
5. phosphorylation (__ to __)
6. oxidation (__ to __)
7. hydration (__ to __)
8. oxidation (__ to __)
- Acetyl CoA to citrate
- Citrate to isocitrate
- isocitrate to α-ketoglutarate
- α-ketoglutarate to succinyl CoA
- Succinyl CoA to succinate
- succinate to fumarate
- fumarate to malate
- oxacelate to acetyl CoA
Enzymes in the citric acid cycle per steps:
1. condensation:
2. isomeration:
3. oxidative decarboxylation:
4. oxidative decarboxylation:
5. phosphorylation:
6. oxidation:
7. hydration:
8. oxidation:
- citrate synthase
- Aconitase
- isocitrate dehydrogenase
- α-ketoglutarate dehydrogenase complex
- sucinyl CoA synthetase
- succinate dehydrogenase
- fumarase
- malate dehydrogenase
Citric acid cycle: Reaction 1: formation of citrate (condensation)
▪ Combines with the two-carbon acetyl group to form citrate.
oxaloacetate
Citric acid cycle: Reaction 2: Isomerization to Isocitrate
▪ Isomerizes to isocitrate.
▪ Has a tertiary —OH group converted to a secondary —OH in isocitrate that can be oxidized.
citrate
Reaction 3: Oxidative Decarboxylation
▪ Undergoes decarboxylation (carbon removed as CO2).
▪ Oxidizes the —OH to a ketone releasing H+ and 2e−.
▪ Provides H to reduce coenzyme NAD+ to NADH.
Isocitrate
Reaction 4: Oxidative Decarboxylation
▪ Undergoes decarboxylation to form succinyl CoA.
▪ Produces a 4-carbon compound that bonds to CoA.
▪ Provides H+ and 2e− to reduce NAD+to NADH.
a-Ketoglutarate
Reaction 5: Hydrolysis
▪ Undergoes breaking of the thioester bond.
▪ Provides energy to add phosphate to GDP and form GTP, a high-energy compound.
Succinyl CoA
Reaction 6: Dehydrogenation
▪ Undergoes dehydrogenation.
▪ Loses two H and forms a double bond.
▪ Provides 2H to reduce FAD to FADH2
Succinate
Reaction 7: Hydration
▪ Undergoes hydration.
▪ Adds water to the double bond.
▪ Is converted to malate.
Fumarate
Reaction 8: Dehydrogenation
▪ Undergoes dehydrogenation.
▪ Forms oxaloacetate with a C=O double bond.
▪ Provides 2H that reduce NAD+ to NADH + H+
Malate
In the citric acid cycle,
▪ An acetyl group bonds with oxaloacetate to form __.
▪ two __ remove two carbons as 2CO2.
▪ four __ provide hydrogen for three
(3) NADH and one (1) FADH2.
▪ A direct phosphorylation forms __(__).
- citrate
- decarboxylations
- oxidations
- GTP (ATP).
What does one turn of the citric acid cycle produce:
2 CO2
1 GTP (1ATP)
3 NADH
1 HS-CoA
1 FADH2
The reaction rate for the citric acid cycle
▪ Increases when low levels of ATP or NAD+
activate __.
isocitrate dehydrogenase
The reaction rate for the citric acid cycle
▪ Decreases when high levels of ATP or NADH
inhibit __(first step in cycle).
citrate synthetase
oxidized and reduced as hydrogen and/or electrons are transferred from one carrier to the next.
electron carriers
Enumerate the electron carriers in order
- FMN (Flavin Mononucleotide)
- Fe-S clusters (Iron-Sulfur Clusters)
- Coenzyme Q (Ubiquinone)
- cytochromes
Electron carriers
▪ Accept __ and __ from the reduced coenzymes.
▪ Are oxidized and reduced to provide energy for the __.
- hydrogen
- electrons
- synthesis of ATP
▪ Contains flavin, ribitol, and phosphate.
▪ Accepts 2H+ + 2e- to form reduced coenzyme FMNH2.
FMN (Flavin mononucleotide)
What contains FMN (Flavin mononucleotide)
- flavin
- ribitol
- phosphate
▪ Are groups of proteins containing iron ions and sulfide.
▪ Accept electrons to reduce Fe3+ to Fe2+, and lose electrons to re-oxidize Fe2+ to Fe3+.
Iron-Sulfur (Fe-S) Clusters
▪ A mobile electron carrier derived from quinone.
▪ Reduced when the keto groups accept 2H+ and 2e-.
Coenzyme Q (Q or CoQ)
▪ Proteins containing
heme groups with
iron ions.
Fe3+ + 1e- -> <- Fe2+
▪ Abbreviated as cyt a, cyt a3, cyt b, cyt c, and cyt c1.
Cytochromes (cyt)
Reduced form of coenzyme Q
CoQH2 or QH2
Oxidized form of flavin mononucleotide
FMN
Reduced form of cytochrome c.
Cyt c (Fe2+)
▪ Uses electron carriers.
▪ Transfers hydrogen ions and electrons from NADH and FADH2 until they combine with oxygen.
▪ Forms H2O.
▪ Produces ATP energy.
Electron transport
Electron transport
▪ Uses __.
▪ Transfers hydrogen ions and electrons from __ and __ until they combine with __.
▪ Forms __.
▪ Produces __.
- electron carriers
- NADH; FADH2
- oxygen
- H2O
- ATP energy
In the electron transport system,
▪ The electron carriers are attached to the __ of the mitochondrion
inner membrane
There are four protein complexes in the electron transport system:
Complex I NADH dehydrogenase
Complex II Succinate dehydrogenase
Complex III CoQ-Cytochrome c reductase
Complex IV Cytochrome c oxidase
Complex II Succinate Dehydrogenase
At Complex I,
1. Hydrogen and electrons are transferred from NADH to FMN. Give the formula
NADH + H+ + FMN –> NAD+ + FMNH2
Complex II Succinate Dehydrogenase
At Complex I.
2. FMNH2 transfers hydrogen to Fe-S clusters and then to coenzyme Q reducing Q and regenerating FMN. Give the formula
Q + FMNH2 –> QH2 + FMN
Complex II Succinate Dehydrogenase
At Complex I,
▪ The overall reaction is
Give the formula.
NADH + H+ + Q –> QH2 + NAD+
Complex II Succinate Dehydrogenase
At Complex 1,
▪ __, a mobile carrier, transfers hydrogen to
Complex III.
QH2
Complex III: CoQ-Cytochrome c reductase
At Complex III,
1. Electrons are transferred from __ to two __.
2. Each Cyt b (Fe3+) is reduced to __(__).
- QH2
- Cyt b
- Cyt b (Fe2+).
Complex III: CoQ-Cytochrome c reductase
At Complex III, Q is regenerated. Give the formula
2Cyt b (Fe3+) + QH2 –> 2Cyt b (Fe2+) + Q + 2H+
Complex III: CoQ-Cytochrome c reductase
At Complex III,
* Electrons are transferred from __ to __, to __, and to __, the second mobile carrier.
2Cyt c (Fe3+) + 2Cyt b (Fe2+) –>
2Cyt c (Fe2+) + 2Cyt b (Fe3+)
- Cyt b to Fe-S clusters
- Cyt c1
- Cyt c
Complex IV: Cytochrome c Oxidase
At Complex IV, electrons are transferred from:
▪ __ to __.
2Cyt c (Fe2+) + 2Cyt a (Fe3+) –> 2Cyt a (Fe2+) + 2Cyt c (Fe3+)
▪ __ to __
2Cyt a (Fe2+) + 2Cyt a3 (Fe3+) –> 2Cyt a (Fe3+) + 2Cyt a3 (Fe2+)
- Cyt c to Cyt a
- Cyt a to Cyt a3
Accepts H and electrons from NADH + H+
FMN
A mobile carrier between Complex II and III.
Cyt c
Carries electrons from Complex I and II to Complex III.
Q
Accepts H and electrons from FADH2
Q
Classify each as a product of the
1) Citric acid cycle 2) Electron transport chain
A. CO2
B. FADH2
C. NAD+
D. NADH
E. H2O
A. 1 CO2
B. 1 FADH2
C. 2 NAD+
D. 1 NADH
E. 2 H2O
▪ Complexes I, III, and IV pump protons into the intermembrane space creating a proton gradient.
▪ Protons pass through ATP synthase to return to the matrix.
▪ The flow of protons through ATP synthase provides the energy for ATP synthesis (oxidative
phosphorylation)
chemiosmotic model
In the chemiosmotic model
▪ Complexes I, III, and IV pump protons into the __ creating a __.
▪ Protons pass through __ to return to the __.
▪ The flow of protons through ATP synthase provides the energy for ATP synthesis (__):
__ + __ + __ -> __
- intermembrane space
- proton gradient
- ATP synthase
- matrix
- oxidative phosphorylation
- ADP + Pi + Energy -> ATP
In __,
▪ Protons flow back to the matrix through a channel in the F0 complex.
▪ Proton flow provides the energy that drives ATP synthesis by the F1 complex.
ATP synthase
In synthase,
▪ Protons flow back to the matrix through a channel in the __.
▪ Proton flow provides the energy that drives ATP synthesis by the __.
- F0 complex
- F1 complex
In the F1 complex of ATP synthase,
▪ A center subunit (γ) is surrounded by three protein subunits:
- loose (L)
- tight (T)
- open (O).
In the F1 complex of ATP synthase,
▪ Energy from the proton flow through __ turns the __.
▪ The shape (conformation) of the three subunits changes.
- F0
- center subunit (γ).
ATP Synthesis in F1
During ATP synthesis,
▪ ADP and Pi enter the __.
▪ The center subunit turns changing the __ to a __.
▪ ATP is formed in the __ where it remains strongly bound.
▪ The center subunit turns changing the __ to __, which releases the ATP.
- loose L site
- L site; tight T conformation
- T site
- T site; an open O site
Oxidative Phosphorylation and ATP:
Contains subunits for ATP synthesis.
F1 Complex
Oxidative Phosphorylation and ATP:
Contains the channel for proton flow.
F0 Complex
Oxidative Phosphorylation and ATP:
The subunit in F1 that binds ADP and Pi.
L site
Oxidative Phosphorylation and ATP:
The subunit in F1 that releases ATP.
O site
Oxidative Phosphorylation and ATP:
The subunit in F1 where ATP forms.
T site
In electron transport, the energy level decreases for electrons,
▪ From NADH (Complex I) provides sufficient energy for 3ATPs. Give formula.
NADH + 3ADP + 3Pi –> NAD+ + 3ATP
In electron transport, the energy level decreases for electrons,
▪ From FADH2 (Complex II) provides sufficient energy for 2ATPs. Give formula.
FADH2 + 2ADP + 2Pi –> FAD + 2ATP
The electron transport system is regulated by
▪ Low levels of __, __, __, and __ that decrease electron transport activity.
▪ High levels of __ that activate electron transport.
- ADP
- Pi
- oxygen
- NADH
- ADP
The complete oxidation of glucose yields:
▪ 6 CO2
▪ 6 H2O
▪ 32 ATP
Reaction Pathway: ATP for One Glucose
ATP from Glycolysis (ATP produced or released)
Activation of glucose:
Oxidation of 2 NADH:
Direct ADP phosphorylation (two triose):
total: __
- -2 ATP
- 5 ATP
- 4 ATP
- 7 ATP
ATP Energy from glucose summary (formula)
C6H12O6 –> 2 pyruvate + 2H2O + 7 ATP
glucose
ATP from Two Pyruvate
Under aerobic conditions
▪ 2 pyruvate are __ to 2 acetyl CoA and 2 NADH.
▪ 2 NADH enters electron transport to provide __.
- oxidized
- 5 ATP
ATP from Two Pyruvate
Under aerobic conditions summary (formula)
2 Pyruvate –> 2 Acetyl CoA + 5 ATP
ATP from Citric Acid Cycle
One turn of the citric acid cycle provides:
* NADH
* FADH
* GTP
Give formula.
3 NADH x 2.5 ATP = 7.5 ATP
1 FADH2 x 1.5 ATP = 1.5 ATP
1 GTP x 1 ATP = 1 ATP
Total = 10 ATP
Acetyl CoA 2 CO2 + 10 ATP
ATP from Citric Acid Cycle
For two acetyl CoA from one glucose, two turns of the citric acid cycle produce __. Give formula.
- 20 ATP
- 2 Acetyl CoA 4 CO2 + 20 ATP
ATP from Citric Acid Cycle
Reaction Pathway ATP (One Glucose):
Oxidation of 2 isocitrate (2NADH): __
Oxidation of 2 a-ketoglutarate (2NADH): __
2 Direct substrate phosphorylations (2GTP): __
Oxidation of 2 succinate (2FADH2): __
Oxidation of 2 malates (2NADH): __
- 5 ATP
- 5 ATP
- 2 ATP
- 3 ATP
- 5 ATP
ATP from Citric Acid Cycle
Reaction Pathway ATP (One Glucose):
summary (formula)
2Acetyl CoA –> 4CO2 + 2H2O + 20 ATP
One glucose molecule undergoing complete oxidation provides how much ATP?
- From glycolysis:
- From 2 pyruvate:
- From 2 acetyl CoA:
- 7 ATP
- 5 ATP
- 20 ATP
Overall ATP Production for one glucose
(formula)
C6H12O6 + 6O2 + 36ADP + 36Pi
–> 6CO2 + 6H2O + 32 ATP
Indicate the ATP yield for each under aerobic conditions.
A. Complete oxidation of glucose
B. FADH2
C. Acetyl CoA in citric acid cycle
D. NADH
E. Pyruvate decarboxylation
A. 32 ATP
B. 1.5 ATP
C. 10 ATP
D. 2.5 ATP
E. 2.5 ATP
In the digestion of fats (triacylglycerols),
▪ __ break fat globules into smaller particles called micelles in the small intestine.
Bile salts
In the digestion of fats (triacylglycerols),
▪ __ hydrolyze ester bonds to form monoacylglycerols and fatty acids, which recombine in the intestinal lining.
Pancreatic lipases
In the digestion of fats (triacylglycerols),
▪ Fatty acids bind with proteins forming __ to transport triacylglycerols to the cells of the heart, muscle, and adipose tissues.
lipoproteins
In the digestion of fats (triacylglycerols),
▪ The __ transport the triacylglycerol to the cells of the heart, muscle, and adipose tissues. When energy is needed in the cells, enzymes hydrolyze the triacylglycerols to yield __ and __.
- chylomicrons
- glycerol; fatty acids
where in the body does this occur?
triacylglycerol –(pancreatic lipase)–> monoacylglycerol
small intestine
where in the body does this occur? and where will it travel?
monoacylglycerols + 2 fatty acids –> triacylglycerol –(protein)–> lipoproteins [chylomicrons]
intestinal cell (epithelial cells)
to the lymphatic system and bloodstream
cells: glycerol + fatty acids
▪ Breaks down triacylglycerols in adipose tissue.
▪ Forms fatty acids and glycerol.
▪ Hydrolyzes fatty acid initially from C1 or C3 of the fat.
fat mobilization
In fat mobilization,
▪ Breaks down triacylglycerols in __.
▪ Forms __ and __.
▪ Hydrolyzes fatty acid initially from __ or __ of the fat.
- adipose tissue
- fatty acids; glycerol
- C1; C3
Fat mobilization formula
triacylglycerols + 3 H2O –> glycerol + 3 fatty acids
Metabolism of __
__ from fat digestion
▪ Adds a phosphate from ATP to form glycerol-3-phosphate.
▪ Undergoes oxidation of the –OH group to dihydroxyacetone phosphate.
▪ Becomes an intermediate used in glycolysis and gluconeogenesis.
- Glycerol ; Glycerol
Metabolism of Glycerol
Glycerol from fat digestion
▪ Adds a phosphate from ATP to form __.
▪ Undergoes oxidation of the –OH group to __.
▪ Becomes an intermediate used in __ and __.
- glycerol-3-phosphate
- dihydroxyacetone phosphate
- glycolysis
- gluconeogenesis
Metabolism of glycerol
glycerol from fat digestion (formula)
Glycerol + ATP + NAD+ –> dihydroxyacetone phosphate + ADP + NADH + H+
oxidation of glycerol
glycerol –(__)–>
glycerol-3-phosphate –(__)–>
dihydroxyacetone phosphate –> glycolysis
- glycerol kinase
- glycerol phosphate dehydrogenase
Why are the triacylglycerols in the intestinal lining coated with proteins to form chylomicrons?
The proteins coat the triacylglycerols to make water-soluble chylomicrons that move into the lymph and bloodstream.
How is glycerol utilized?
Glycerol adds a phosphate and is oxidized to an intermediate of the glycolysis pathway.
▪ Allows the fatty acids in the cytosol to enter the mitochondria for oxidation.
▪ Combines a fatty acid with CoA to yield fatty acyl-CoA that combines with carnitine.
Fatty acid activation
Fatty acid activation
▪ Allows the fatty acids in the __ to enter the __ for oxidation.
▪ Combines a fatty acid with CoA to yield fatty __ that combines with __.
- cytosol
- mitochondria
- acyl-CoA
- carnitine
fatty acid activation in the
cytosol:
__ + __ + __ –> __ + __ + 2 Pi
intermembrane space:
__ + __ (__ is released) –> __
- fatty acid + CoA + ATP –> fatty acyl-CoA + AMP + 2 Pi
- fatty acyl-CoA + carnitine (CoA is released) –> fatty acyl-carnitine
Transport of Fatty Acyl CoA
▪ Fatty acyl-CoA forms __ that transports the fatty acyl group into the __.
▪ The fatty acyl group recombines with CoA for __.
- fatty acyl-carnitine
- matrix
- beta-oxidation
complex, but it regulates the degradation and synthesis of fatty acids.
fatty acid activation
Beta-Oxidation of Fatty Acids reactions
Reaction 1, Dehydrogenation.
Reaction 2, Hydration.
Reaction 3, Oxidation.
Reaction 4, Cleavage.
Beta-Oxidation of Fatty Acids:
Reaction 1, Dehydrogenation. The first reaction removes __ from the __ and __, and a __ is formed. These hydrogens are transferred to FAD to form __.
- one hydrogen
- alpha; beta carbons
- double bond
- FADH2
Beta-Oxidation of Fatty Acids:
Reaction 2, Hydration. In reaction 2, __ is added to the __ and __ as –H and –OH, respectively.
- water
- alpha; β carbon double bond
Beta-Oxidation of Fatty Acids:
Reaction 3, Oxidation. The __ formed on the __ is oxidized to a __. As we have seen before in the citric acid cycle, the hydrogen from the alcohol reduces NAD+ to __.
- alcohol
- β carbon
- ketone
- NADH
Beta-Oxidation of Fatty Acids:
Reaction 4, Cleavage. In the fourth reaction of the cycle, the bond between the alpha and β carbon is broken and a second __ is added, forming an __ and a __ shortened by __. The fatty acyl CoA can be run through the cycle again.
- CoA
- acetyl CoA
- fatty acyl CoA
- two carbons
reactions of beta-oxidation of fatty acids:
Water is added.
hydration
reactions of beta-oxidation of fatty acids:
FADH2 forms.
oxidation 1
reactions of beta-oxidation of fatty acids:
A two-carbon unit is removed.
acetyl CoA cleaved
reactions of beta-oxidation of fatty acids:
A hydroxyl group is oxidized.
oxidation 2
reactions of beta-oxidation of fatty acids:
NADH forms.
oxidation 2
Beta (β)-Oxidation of Myristic (C14) Acid stages
Reaction 1 Oxidation (dehydrogenation)
Reaction 2 hydration
Reaction 3 Oxidation (dehydrogenation)
Reaction 4 Cleavage (6 cycles) = 7acetyl CoA
▪ Determines the number of oxidations
▪ Determines the total number of acetyl CoA groups.
length of a fatty acid
How many acetyl CoA is produced with fatty acids with the following number of carbon atoms and how many oxidation cycles?
a. 12
b. 14
c. 16
d. 18
Acetyl CoA (#C/2)
a. 6
b. 7
c. 8
d. 9
bet-oxidation cycles (#C/2-1)
a. 5
b. 6
c. 7
d. 8
The number of acetyl CoA groups produced by the complete beta-oxidation of palmitic acid (C16 )
8
The number of oxidation cycles to completely oxidize palmitic acid (C16)
7
Activation of a fatty acid requires
2 ATP
One cycle of oxidation of a fatty acid produces
1 NADH –> 2.5 ATP
1 FADH2 –> 1.5 ATP
Acetyl CoA entering the citric acid cycle produces
1 Acetyl CoA –> 10 ATP
If carbohydrates are not available
▪ __ breaks down to meet energy needs.
▪ Keto compounds called __ form.
- Body fat
- ketone bodies
Ketone bodies are produced mostly in the __ and transported to cells in the __, __, and __, where small amounts of energy can be obtained by converting __ or __ back to __
- liver
- heart; brain; skeletal muscle
- acetoacetate; hydroxybutyrate
- acetyl CoA
In ketogenesis
▪ Large amounts of __ accumulate.
▪ Two __ molecules combine to form __.
▪ __ hydrolyzes to __, a ketone body.
▪ __ reduces to __ or loses CO2 to form __, both ketone bodies.
- acetyl CoA
- acetyl CoA
- acetoacetyl CoA
- Acetoacetyl CoA
- acetoacetate
- Acetoacetate
- beta-hydroxybutyrate
- acetone
▪ Large amounts of acetyl CoA accumulate.
▪ Two acetyl CoA molecules combine to form acetoacetyl CoA.
▪ Acetoacetyl CoA hydrolyzes to acetoacetate, a ketone body.
▪ Acetoacetate reduces to -hydroxybutyrate or loses CO2 to form acetone, both ketone bodies.
ketogenesis
__ occurs
▪ In diabetes, diets high in fat, and starvation.
▪ As ketone bodies accumulate.
▪ When acidic ketone bodies lower blood
pH below 7.4 (__).
Ketosis
- acidosis
In diabetes,
▪ __ does not function properly.
▪ __ are insufficient for energy needs.
▪ __are broken down to __.
▪ Ketogenesis produces __.
- Insulin
- Glucose levels
- Fats
- acetyl CoA
- ketone bodies
In all types of diabetes, insufficient amounts of glucose are available in the __, __, and __. As a result, liver cells synthesize glucose from __ (__) and break down __, elevating the acetyl CoA level. Excess acetyl CoA undergoes __, and __ accumulate in the blood. As the level of __ increases, its odor can be detected on the breath of a person with uncontrolled diabetes who is in __.
- muscle; liver; adipose tissue
- noncarbohydrate sources (gluconeogenesis)
- fat
- ketogenesis
- ketone bodies
- acetone
- ketosis
In ketogenesis, what type of reaction:
acetoacetate produces acetone
decarboxylation
In ketogenesis, what type of reaction:
acetoacetate produces β-hydroxybutyrate
reduction
The digestion of proteins (stage 1)
▪ Begins in the stomach where __ in stomach acid activates __ to hydrolyze peptide bonds.
▪ Continues in the small intestine where __ and __ hydrolyze peptides to amino acids.
▪ Is complete as amino acids enter the __ for transport to cells.
- HCl
- pepsin
- trypsin
- chymotrypsin
- bloodstream
Proteins provide
▪ Amino acids for __.
▪ __ atoms for nitrogen-containing compounds.
▪ __ when carbohydrate and lipid resources are not available.
- protein synthesis
- Nitrogen
- Energy
In transamination
▪ Amino acids are degraded in the __.
▪ An amino group is transferred from an amino acid to an alpha-keto acid, usually __.
▪ The reaction is catalyzed by a __ or __.
▪ A new amino acid, usually __, and a new __ are formed.
- liver
- alpha ketoglutarate
- transaminase
- aminotransferase
- glutamate
- alpha-keto acid
▪ Removes the amino group as an ammonium ion from glutamate.
▪ Provides alpha-ketoglutarate for transamination.
Oxidative deamination
Oxidative deamination
▪ Removes the __ as an ammonium ion from __.
▪ Provides __ for transamination.
- amino group
- glutamate
- alpha-ketoglutarate
▪ Detoxifies ammonium ion from amino acid degradation.
▪ Converts ammonium ion to urea in the liver.
▪ Provides 25-30 g urea daily for urine formation in the kidneys.
urea cycle
urea cycle
▪ Detoxifies ammonium ion from __.
▪ Converts ammonium ion to __ in the __.
▪ Provides __ urea daily for urine formation in the __.
- amino acid degradation
- urea
- liver
- 25-30 g
- kidneys
__ is formed
▪ In the mitochondria, when ammonium ion reacts with CO2 from the citric acid cycle, 2 ATP, and water.
Carbamoyl phosphate
Reactions in the urea cycle
Reaction 1 Transfer of Carbamoyl Group
Reaction 2 Condensation with Aspartate
Reaction 3 Cleavage of Fumarate
Reaction 4 Hydrolysis Forms Urea
In reaction 1 of the urea cycle,
▪ The carbamoyl group is transferred to __ to form __.
▪ __ moves across the __ into the __.
- ornithine
- citrulline
- Citrulline
- mitochondrial membrane
- cytosol
In reaction 2 of the urea cycle,
▪ That takes place in the __, __ combines with __.
▪ Hydrolysis of __ to __ provides energy.
▪ The N in __ is part of urea.
- cytosol
- citrulline
- aspartate
- ATP; AMP
- aspartate
In reaction 3 of the urea cycle, fumarate
▪ Is cleaved from __.
▪ Enters the __.
- argininosuccinate
- citric acid cycle
In reaction 4 of the urea cycle,
▪ __ is hydrolyzed
▪ __ forms.
▪ __ returns to the mitochondrion to pick
up another __ to repeat the urea cycle.
- Arginine
- Urea
- Ornithine
- carbamoyl group
Summary of Urea Cycle
The urea cycle converts:
▪ Ammonium ion to __
▪ Aspartate to __
▪ 3ATP to __, __, __
- urea
- Fumarate
- 2ADP, AMP, 4Pi
Urea Cycle Formula
NH4+ + CO2 + 3ATP + aspartate + 2H2O
—> urea + 2ADP + AMP + 4Pi + fumarate
Identify the site for each as:
formation of urea
cytosol
Identify the site for each as:
formation of carbamoyl phosphate
mitochondrion
Aspartate combines with citrulline
cytosol
Identify the site for each as:
fumarate is cleaved
cytosol
Identify the site for each as:
citrulline forms
mitochondria
Carbon Atoms from Amino Acids:
When needed, carbon skeletons of amino acids are used to produce energy by forming intermediates of the __.
citric acid cycle
Carbon atoms from amino acids
▪ Three-carbon skeletons
alanine, serine, and cysteine –> pyruvate
Carbon atoms from amino acids
▪ Four-carbon skeletons
aspartate, asparagine –> oxaloacetate
Carbon atoms from amino acids
▪ Five-carbon skeletons
glutamine, glutamate, proline, arginine, histidine
–> glutamate
Amino acids are classified as
- Glucogenic
- Ketogenic
Amino acids that generate pyruvate or oxaloacetate, which can be used to synthesize glucose.
Glucogenic
Amino acids that generate acetoacetyl CoA or acetyl CoA, which can form ketone bodies or fatty acids.
Ketogenic
Amino Acid Pathways to Citric Acid Intermediates:
acetyl CoA <–>
acetoacetyl CoA –>
ketone bodies (ketogenesis)
acetyl CoA:
- Isoleucine
- Leucine
- Threonine
- Tryptophan
acetoacetyl CoA
- Leucine
- Lysine
- Phenylalanine
- Tyrosine
Amino Acid Pathways to Citric Acid Intermediates:
alpha-ketoglutarate
C-5 family
(glucogenic)
Arginine
glutamate
glutamine
histidine
proline
Amino Acid Pathways to Citric Acid Intermediates:
succinyl CoA
C-4 Family
(glucogenic)
Isoleucine
Methionine
Valine
Amino Acid Pathways to Citric Acid Intermediates:
Fumarate
C-4 Family
(glucogenic)
Aspartate
Tyrosine
Phenylalanine
Amino Acid Pathways to Citric Acid Intermediates:
Oxaloacetate
C-4 Family
(glucogenic)
Asparagine
Aspartate
intermediate with the amino acid that
provides its carbon skeleton: cysteine
pyruvate
intermediate with the amino acid that
provides its carbon skeleton: glutamate
alpha-ketoglutarate
intermediate with the amino acid that
provides its carbon skeleton: aspartate
fumarate
intermediate with the amino acid that
provides its carbon skeleton: serine
pyruvate
Overview of Metabolism
In metabolism
▪ __ determine which compounds are degraded to acetyl CoA to meet energy needs or converted to glycogen for storage.
▪ Excess glucose is converted to __.
▪ Some amino acids are produced by __.
- Branch points
- body fat
- transamination
