Week 13: Glycogen Synthesis, Pentose Phosphate Pathway, Fatty Acid and Lipid Metabolism

Question 1

Why is it essential that the regulatory mechanisms that activate glycogen synthesis also deactivate glycogen phosphorylase?

Because these two processes occur in the _______ in the cell, this regulation makes the ______ more efficient.

Such a regulatory mechanism prevents the simultaneous ______ of glucose monomers, preventing unnecessary reactions.

Answer 1

same location, net process

addition and removal

Question 2

The free energy of formation of UDP-glucose from UTP and glucose-1-phosphate is close to zero. The pyrophosphate that is produced in this reaction, when hydrolyzed to two phosphate ions, ______ considerable energy. The coupling of these two reactions makes the net reaction ______.

The addition of glucose to glycogen as UDP-glucose is converted to UDP is approximately energy-neutral. Thus, the overall formation of glycogen is exergonic. The net effect is that some of the energy stored in the terminal phosphodiester bond of UTP and some of the energy stored in the phosphoester bond of glucose-1-phosphate is stored in glucose-glucose bonds in glycogen and some is lost in the hydrolysis of pyrophosphate.

Answer 2

releases, exergonic

Question 3

Increasing the level of ATP favors both ____ and ______.

Decreasing the level of fructose-1,6-bisphosphate tends to stimulate ______ rather than _______.

The level of fructose-6-phosphate does not have a marked regulatory effect on _______.

Answer 3

gluconeogenesis and glycogen synthesis

glycolysis, gluconeogenesis or glycogen synthesis

gluconeogenesis or glycogen synthesis

Question 4

Why is a different reducing agent (NADPH) is used in anabolic reactions rather than NADH, which is used in catabolic reactions?

This separation helps to untangle the two pathways so that the reactions are ______.

Answer 4

independently controllable

Anabolic and catabolic reactions must be regulated independently. Having two different redox species for the two pathways makes it much easier to regulate each pathway’s reactions without interfering with the other pathway’s reactions.

Question 5

What are reasons that a fatty acid is linked to coenzyme A for metabolic purposes?

Acyl-CoAs are _______ compounds. An acyl-CoA has sufficient ______ to initiate the _______ process. The CoA is also a tag indicating that the molecule is destined for oxidation.

Answer 5

high-energy, energy

β-oxidation

molecular tag

Question 6

Calculate the ATP yield for the complete oxidation of the 20-carbon saturated fatty acid arachidic acid.

(You should consider the β-oxidation steps, processing of acetyl-CoA through the citric acid cycle, and electron transport. Production of one GTP should be considered the equivalent of production of one ATP. Enter your answer to three significant figures.)

___ ATPs are gained for each arachidic acid oxidized

Answer 6

134

The 20-carbon arachidic acid will go through 9 rounds of β-oxidation. This will produce 9 FADH2s, 9 NADHs, and 10 acetyl-CoAs. These 10 acetyl-CoAs will each produce one FADH2, one GTP, and three NADHs in the citric acid cycle for a total of 10 FADH2s, 30 NADHs, and 10 GTPs from this cycle. There are thus a total of 39 NADHs and 19 FADH2s produced per arachidic acid.

Oxidation of one FADH2 via electron transport produces 1.5 ATPs while oxidation of one NADH via electron transport produces 2.5 ATPs. Thus, oxidation of the NADH produced in the metabolism of arachidic acid is responsible for the synthesis of 2.5 × 39 = 97.5 ATPs and oxidation of FADH2 is responsible for 1.5 × 19 = 28.5 ATPs.

The net production of ATP plus GTP is thus 10 + 97.5 + 28.5 = 136 per arachidic acid. A two ATP-equivalent is consumed in the initial activation step, so the overall net ATP gain is 134 ATPs per arachidic acid that is fully oxidized.

Question 7

Calculate the ATP yield for the complete oxidation of a 21-carbon saturated fatty acid.

(You should consider the β-oxidation steps, processing of acetyl-CoA through the citric acid cycle, and electron transport. Production of one GTP should be considered the equivalent of production of one ATP. Enter your answer to three significant figures.)

_____ ATPs are gained for each 21-carbon fatty acid oxidized

Answer 7

129

The 21-carbon fatty acid will go through 9 rounds of β-oxidation. This will produce 9 FADH2s, 9 NADHs, 9 acetyl-CoAs, and one proprionyl-CoA. The 9 acetyl-CoAs will each produce one FADH2, one GTP, and three NADHs in the citric acid cycle for a total of 9 FADH2s, 27 NADHs, and 9 GTPs from this cycle. The proprionyl-CoA will produce one NADH and one FADH2 via the citric acid cycle along with one GTP. There are thus a total of 37 NADHs and 19 FADH2s produced per 21-carbon fatty acid.

Oxidation of one FADH2 via electron transport produces 1.5 ATPs while oxidation of one NADH via electron transport produces 2.5 ATPs. Thus, oxidation of the NADH produced in the metabolism of the 21-carbon fatty acid is responsible for the synthesis of 2.5 × 37 = 92.5 ATPs and oxidation of FADH2 is responsible for 1.5 × 19 = 28.5 ATPs.

The net production of ATP plus GTP is thus 9 + 1 + 92.5 + 28.5 = 131 per fatty acid. A two ATP-equivalent is consumed in the initial activation step for the original fatty acid and one ATP-equivalent is used in the conversion of proprionyl-CoA to succinyl-CoA, so the overall net ATP gain is 128 ATPs per 21-carbon fatty acid that is fully oxidized.

Question 8

Calculate the ATP yield for the complete oxidation of the 20-carbon unsaturated fatty acid gadoleic acid (a 20:1-Δ9 fatty acid).

(You should consider the β-oxidation steps, processing of acetyl-CoA through the citric acid cycle, and electron transport. Production of one GTP should be considered the equivalent of production of one ATP. Enter your answer to three significant figures.)

_____ ATPs are gained for each gadoleic acid oxidized

Answer 8

133

The 20-carbon gadoleic acid will go through 9 rounds of β-oxidation. This will produce 8 FADH2s, 9 NADHs, and 10 acetyl-CoAs. (If the fatty acid had been saturated, 9 FADH2s would have been produced in the β-oxidation cycles. One less is produced here because one of the oxidation steps catalyzed by acyl-CoA dehydrogenase is not needed due to the presence of the C=C double bond in the original fatty acid.)

The 10 acetyl-CoAs from above will each produce one FADH2, one GTP, and three NADHs in the citric acid cycle for a total of 10 FADH2s, 30 NADHs, and 10 GTPs from this cycle. There are thus a total of 39 NADHs and 18 FADH2s produced per gadoleic acid.

Oxidation of one FADH2 via electron transport produces 1.5 ATPs, while oxidation of one NADH via electron transport produces 2.5 ATPs. Thus, oxidation of the NADH produced in the metabolism of gadoleic acid is responsible for the synthesis of 2.5 × 39 = 97.5 ATPs and oxidation of FADH2 is responsible for 1.5 × 18 = 27.0 ATPs.

The net production of ATP plus GTP is thus 10 + 97.5 + 27.0 = 135 per gadoleic acid. A two ATP-equivalent is consumed in the initial activation step, so the overall net ATP gain is 133 ATPs per gadoleic acid that is fully oxidized.

Question 9

When oxaloacetate is in insufficient supply, as under starvation conditions, the ______ produced in β-oxidation cannot enter the ______ but rather is used to form ______.

Answer 9

acetyl-CoA

citric acid cycle

ketone bodies

Question 10

Ketone bodies are produced when ______ lags behind _______.

Ketone bodies are produced when ______ is in insufficient supply.

Answer 10

carbohydrate metabolism
lipid metabolism

oxaloacetate

Question 11

There are many differences in the pathways of fatty-acid breakdown and fatty-acid synthesis. Similarities include the use of ______ as a carrier, the use of ______ linkages, and a _____ unit that is fundamental to both pathways.

Answer 11

coenzyme A
thioester
two-carbon

Question 12

The source of the glycerol in triacylglycerol synthesis is from _______ derived from _______

Answer 12

glycerol-3-phosphate
glycolysis

Glycerol comes from the degradation of acylglycerols or from the glycerol-3-phosphate derived from the glycolysis pathway.

Question 13

_____ and _______ have cholesterol as a synthetic precursor.

Answer 13

Bile acids, steroid hormones (estradiol)

Question 14

Why must cholesterol be packaged for transport rather than occurring freely in the bloodstream?

Cholesterol is _____ and will not readily _____ in the aqueous bloodstream.

______, which effective solubilize cholesterol, are needed to transport cholesterol in the blood.

Answer 14

nonpolar, dissolve

Carrier proteins

Question 15

The pentose phosphate pathway can make both NADPH and pentose phosphates in roughly equimolar amounts by using only ______ reactions.

The pentose phosphate pathway can make mostly NADPH by using the _____reactions, the _______ reactions, and ______.

The pentose phosphate pathway can make mostly pentose phosphates by using _____ and the ______ reactions in reverse.

Answer 15

oxidative

oxidative, transaldolase and transketolase, gluconeogenesis

glycolysis, transaldolase and transketolase

Question 16

UDP-glucose is used to ______ the glycogen chain
in synthesis.

Answer 16

extend

Question 17

______ is the key regulatory enzyme in glycogen synthesis
* transfers a glucose moiety from ______ to the C-4 terminal residue of a glycogen chain to form an _______.
* requires an oligosaccharide of glucose residues as a primer.

• Glycogenin
• a small protein homodimer that synthesizes the ______.
• Each subunit of glycogenin generates an oligosaccharide of glucose residues ______ glucosyl units long.
• _______ then extends this primer.

Answer 17

Glycogen synthase
UDP-glucose, α-1,4-glycosidic bond

primer, 10–20

Glycogen synthase

Question 18

Glycogen synthase adds to ______ ends, builds ______

Answer 18

non-reducing, straight chain

Question 19

Branching enzyme in branching reaction cleaves _______ linkages off chains that are at least _____ long and clips of ______.

Answer 19

a-1,4 linkages, 11 units, 7-8 units

Question 20

Glycogen synthase has:

• Phosphorylated ____ form (usually _____) and unphosphorylated _____ form (more _____)
• Note that phosphorylation has ______ effects on glycogen synthase than on glycogen phosphorylase
• T (_____ active) and R (_____ active) forms

Answer 20

b, inactive
a, active
Unphosphorylated form more active
opposite

less, more

Question 21

Regulatory processes for glycogen synthase:
* Allosteric regulation: Binding of glucose 6-phosphate converts ____ form to ____ form. This conformational change favors ______ by protein phosphatase 1 (PP1).

• Covalent regulation:
• Insulin promotes ______ of glycogen synthase
• Glucagon and epinephrine promote ________.

Answer 21

T, R
dephosphorylation
Glucose-6-phosphate is a positive affector of glycogen synthase

desphosphorylation
phosphorylation

Question 22

• Glycogen breakdown:
• ______ is the regulatory enzyme.
• Most active when ______.
• Glycogen synthesis:
  *_______ is regulatory enzyme.
• Most _____ when phosphorylated.

Answer 22

Phosphorylase, phosphorylated

Glycogen synthase
inactive

Question 23

Phosphorylation of glycogen synthase by _____ to form glycogen synthase b _____ glycogen synthesis

Answer 23

protein kinase A
inhibits

Question 24

Protein phosphatase 1 (PP1) shifts glycogen metabolism from the ______ mode to the ______ mode.

Answer 24

degradation
synthesis

Question 25

Protein phosphatase 1 (PP1) _____ phosphoryl groups from phosphorylase kinase and phosphorylase a, inhibiting ________

Answer 25

removes
glycogen degradation

Question 26

PP1 removes phosphoryl groups from glycogen synthase ____, converting it into the more active ____ form.

Answer 26

b, a

Question 27

Insulin also helps in regulation of these pathways,

insulin inactivates _______ by ______ it

Answer 27

glycogen synthase kinase
phosphorylating

Question 28

Glycogen synthase kinase is an enzyme that ______ a _____ to glycogen synthase

Answer 28

adds, phosphate

Question 29

PPP Yields ______ and _____

• ______ is typically carrier for ______ pathways (______
  movement of electrons generally use ______)
• _____ are pre-cursors for ______
  2. Glycolysis and PPP are ______ controlled.

Answer 29

NADPH, 5-C sugars

NADPH, biosynthetic (building/synthesizing)
Catabolic (breaking down), NADH

5-C sugars, nucleotides

coordinately (control tied together) because G-6-P has multiple pathways

Question 30

The first phase of the pentose phosphate pathway is the ______ generation of ______. Has ____ enzymatic steps

The second phase is the _______ interconversion of a variety of sugars.

Answer 30

oxidative, NADPH, 3 enzymatic steps

nonoxidative

Question 31

The first reaction of the pentose phosphate pathway, the ________ of ________ by _______, is the _______ step of the pathway.

The rate of the oxidative phase of the pentose phosphate pathway is controlled by the _______

_______ is the most important regulatory factor.

Answer 31

dehydrogenation
glucose 6-phosphate
glucose 6-phosphate dehydrogenase
rate-limiting

concentration of NADP+

[NADP+]

Question 32

When ribose 5-phosphate needs exceed the needs for NADPH

_____ will occur to get to G-3-P and ______ phase of PPP will occur to get ribose-5-phosphate

Answer 32

Glycolysis, non-oxidative

Question 33

When NADPH and ribose 5-phosphate needs are balanced:

the ______ phases of PPP occur and it stops after that

Answer 33

oxidative
(ex. when cells are rapidly dividing)

Question 34

When more NADPH is needed than ribose-5-phosphate:

the _____ phase of PPP occurs, then the ribose-t-phosphate created is recycled back to make starting G-C-P through _____ phase

Answer 34

oxidative
non-oxidative
(ex. liver cells synthesizing fatty acids)

Question 35

When both NADPH and ATP are required:

____ phase of PPP occurs and the ribose-5-phosphate created will undergo ______ phase to get metabolites to then make ATP through ______

Answer 35

oxidative
non-oxidative
glycolysis

Question 36

_______ is the enzyme that controls the pentose phosphate pathway

Answer 36

Glucose-6-phosphate dehydrogenase

Question 37

Fatty acid degradation, the activation and transfer of the ______ into the ______ and the _____ repetitive enzymatic steps of the _______ pathway.

Answer 37

acyl chain
mitochondria
four
beta oxidation

Question 38

Chylomicron particles are 98% _______ with ______ and ______ on the surface

Answer 38

triacylglycerols
proteins, phospholipids

Triacylglycerols need to be packaged into chylomicron to enter the bloodstream as they are NOT water soluble

Question 39

Triacylglycerols in adipose tissue are converted into ______. This happens in response to hormonal signals that result in a series of ______ that activate the _____.

Answer 39

free fatty acids
phosphorylations
lipases

Question 40

Lipase adds ______ to break ester linkages stepwise until it makes three fatty acids and ______.

Answer 40

water, glycerol

Question 41

Glycerol is soluble in _____, carried to liver and converted to ______, which can enter ______ or ______

Answer 41

blood
DHAP
glycolysis, gluconeogenesis

Question 42

Fatty acids are then transported out of fat cell into ______ and carried on a protein called ______

Answer 42

blood plasma
albumin

Question 43

The fatty acids incorporated into triacylglycerols in adipose tissue are made accessible in three stages.

1._______ to ______ fatty acids and glycerol into the blood for transport to energy-requiring tissues

2. ______ of the fatty acids and transport into the ______ for ______
3. _______ of the ______ to acetyl CoA for processing by the citric acid cycle

Answer 43

Degradation of TAG, release

Activation, mitochondria, oxidation

Degradation, fatty acids, acetyl CoA

Question 44

Fatty acid activation by acyl CoA synthetase

______ and ______
Driven by hydrolysis of _________

Answer 44

spontaneous
irreversible
pyrophosphate

Question 45

Activated Fatty Acid must be _____ into mitochondria

Answer 45

ported
Turned into acyl carnitine to go through mitochondria

Question 46

Describe the repetitive steps of β oxidation

Answer 46

1) Oxidation (resulting in DB)
2) Hydration (Adding water, resulting in an -OH group)
3) Oxidation (C=O)
4) Thiolysis (adding CoA)

Question 47

Enzymes for the repetitive steps of β oxidation

Answer 47

1) Oxidation (resulting in DB) - Acyl CoA dehydrogenase
2) Hydration (Adding water, resulting in an -OH group) - Enoyl CoA hydrotase
3) Oxidation (C=O) - 3-hydroxyacyl CoA dehydrogenase
4) Thiolysis (adding CoA) - Thiolase

Question 48

The process is called β oxidation because its the ______ carbon that is being oxidized.

Answer 48

beta (second carbon away from carbonyl carbon)

Question 49

Degradation of an unsaturated fatty acid requires one less _____ step because it already has that _______ that an ______ moves to put into the ______ configuration needed

Answer 49

oxidation
double bond
isomerase
trans

Question 50

• β Oxidation of fatty acids with odd numbers of carbons generates _______ in the last ______ reaction.
• _______, a ______ enzyme, adds a ______ to propionyl CoA to form ________.
• Succinyl CoA, a citric acid cycle component, is subsequently formed from methylmalonyl CoA by ________, a vitamin B12 -requiring enzyme.

Answer 50

propionyl CoA (3 carbon), thiolysis

Propionyl CoA carboxylase, biotin, carbon, methylmalonyl CoA

methylmalonyl CoA mutase

Question 51

Formation of ketone bodies (______)
Alternative route for _______ when have _____ glucose
Occurs when excess buildup of _______ and not enough glucose to meet the energy needs of the organism
Occurs in _____

Answer 51

ketogenesis
acetyl CoA, low
acetyl CoA
liver mitochondria

Question 52

3 primary products of ketogenesis:

Answer 52

Acetoacetate
D-3-Hydroxybutyrate
Acetone

Question 53

Second step of ketogenesis is the control step, with the enzyme __________ that makes the 6-carbon structure

Glucagon (low blood sugar) makes it _____
Insulin (high blood sugar) makes it _______

Answer 53

hydroxy methyl glutoryl CoA synthase

speeds up
slows down

Question 54

Products of ketogenesis:

D-3-Hydroxybutyrate is formed upon the _______ of acetoacetate. Acetone is generated by the spontaneous ________ of acetoacetate.

Answer 54

reduction
decarboxylation

Question 55

D-3-hydroxybutyrate can be considered a superior ketone body compared to acetoacetate because…

Answer 55

not only does it produce acetyl CoAs, it also makes NADH

Question 56

_____ is the predominant fuel for the brain.

• During starvation, ________ is initially the source of carbons for ________ in the liver. The glucose is then released into the blood for the brain to use.
• After several days of fasting, the brain begins to use _______ as a fuel.

Answer 56

Glucose
protein degradation, gluconeogenesis
ketone bodies

Question 57

Fatty acids represent a ______ energy source than carbohydrates because they generally yield more ______

Answer 57

richer
ATP

Question 58

Energy Yield from Oxidation of Fatty Acids
* Each cycle of β-oxidation
* 1 mole FADH2
* 1 mole NADH
* Total: _______

Answer 58

(1.5 ATP)
(2.5 ATP)
Both can donate electrons to electron transport chain

• Total: 4 ATP

Question 59

• Acetyl-CoA enters citric acid cycle
• 3 mole NADH (7.5 ATP)
• 1 mole FADH2 (1.5 ATP)
• 1 mole GTP (1 ATP)
• Total: _______

Answer 59

10 ATP

Question 60

Energy Yield from Oxidation of Stearic Acid
* 8 rounds of β-oxidation
* 8 x 4 ATP = 32 ATP
* 9 moles acetyl-CoA
* 9 x 10 ATP = 90 ATP
* _________ of ATP to activate
* Total: 32 + 90 – 2 = 120 ATP yield

Answer 60

-2 moles

Question 61

1.The first stage of fatty acid synthesis is transfer of ______ out of the ______ into the ______. Citrate is transported into the cytoplasm and cleaved into oxaloacetate and acetyl CoA.

2. The second stage is the activation of _____ to form _______.
3. The third stage is the repetitive addition and reduction of _______ units to synthesize C 16 fatty acid. Synthesis occurs on an __________, a molecular scaffold.

Answer 61

acetyl CoA, mitochondria, cytoplasm

acetyl CoA, malonyl CoA

two carbon units, acyl carrier protein

Question 62

Stage 2: The Formation of ______ Is the Committed Step in Fatty Acid Synthesis

Malonyl CoA is synthesized from acetyl CoA by ______________, a biotin-requiring enzyme.

The formation of malonyl CoA occurs in two steps

Answer 62

Malonyl CoA
acetyl CoA carboxylase 1

Question 63

________, a complex of enzymes, catalyzes the formation of fatty acids

Fatty acid synthesis occurs on the _______, a polypeptide linked to the ________ group

_______ and _______ attach substrates to the ______

Answer 63

Fatty acid synthase
acyl carrier protein (ACP)
phosphopantetheine group (Vit B5)
Acetyl transacylase, malonyl transacylase

Question 64

Acyl carrier protein is similar in structure to coenzyme A, but differs by having a _____ residue instead of _____

Answer 64

serine
AMP

Question 65

Fatty acid synthesis enzymes:
1)
2)
3)
4)

Answer 65

1) ketoacyl synthase (site for condensation, also has a docking site)
2) ketoacyl reductase
3) 3 hydroxyl dehydratase (water being removed, makes DB)
4) enoyl reductase (reduces the DB)

Question 66

The ______ group is passed to the docking site of _______, allowing ACP to pick up _______

Answer 66

acetyl
ketoacyl synthase
malonyl group

Question 67

_____ is the acyl group carrier for fatty acid oxidative degradation.

______ is the carrier for fatty acid synthesis

Answer 67

Coenzyme A
Acyl carrier protein (ACP)

Question 68

Mammals lack the enzymes that introduce double bonds from carbon _____, these need to be obtained in the ______

Answer 68

9 from the carbonyl
diet

Question 69

What Enzyme Regulates Fatty Acid Synthesis and Degradation?
* Main regulation: _______
* Regulates both synthesis and beta-oxidation
* ACC adds _______ group to acetyl CoA.
* Forms activated starting material, _______
.
* There are two isozymes of ACC:
* Cytosolic (ACC1) – where ______ occurs
* Mitochondrial (ACC2) – where _______ occurs
* Both do same thing – synthesize malonyl CoA from acetyl CoA and bicarbonate

Answer 69

Acetyl CoA carboxylase (ACC)
carboxylate
malonyl CoA

synthesis
degradation

Question 70

For each of these situations, would you want ACC1 (cystolic ACC) to be active?

1. The blood stream has a large concentration of fatty acyl-CoA (fatty acids bound to CoA)
2. High levels of insulin
3. The body has a large concentration of AMP
4. The body has build up of citrate

Answer 70

1. Slow synthesis, negative affector of ACC1
2. Indicates high blood glucose, activates ACC1
3. Indicates that body has energy needs, negative effector of ACC1
4. Means energy needs met, want ACC1 active, positive effector of synthesis

Question 71

• When energy needs high:
• glucagon and AMP high
• Do not want to be ________ in this situation
• High AMP activates AMPK active both inside and outside of mitochondria
• AMPK acts on both ACC1 and ACC2 (phosphorylates them), which deactivates them.
• When deactivated, shuts down synthesis of malonyl CoA both inside and outside the mitochondria
• In cytosol: This means we shut down fatty acid synthesis (______ synthesis)
• In matrix this means we can now transport fatty acids into the matrix for degradation, so beta-oxidation can begin to happen. (_______ degradation)

Answer 71

synthesizing fatty acids

inhibits
stimulates

Question 72

Cholesterol has a complicated synthetic pathway (MANY steps)
The regulatory enzyme of cholesterol synthesis is ____

Answer 72

HMG CoA Reductase

Question 73

• Cholesterol and triacylglycerols are transported in the blood in the form of ______ particles.
• Lipoprotein particles consist of a protein(s) component and various lipids, depending on the type of particle.
• The protein(s) serve to _______ the lipids and to direct the particles to specific targets.
• Lipoprotein particles are classified according to density: the greater proportion of lipid, the _____ dense the particle.
• _______ is the major carrier of cholesterol in the blood.
• High-density lipoprotein (HDL) carries cholesterol released into the blood back to the liver, a process called reverse cholesterol transport.

Answer 73

lipoprotein

solubilize

less (more TAG, less dense)

Low-density lipoprotein (LDL)

Question 74

Low-density lipoproteins deliver cholesterol to peripheral tissues. At the tissues, cholesterol enters the cell by receptor-mediated _______.

Answer 74

endocytosis

Question 75

• Familial hypercholesterolemia:
• genetic disease that results from the absence of the functional
  _______.
• Studies of this disease have shed light on other, more common
  situation of _____ levels of cholesterol.

Answer 75

LDL receptor
high

No LDL receptor to pull cholesterol out of bloodstream, causing excess cholesterol to collect in various tissues of the body

Question 76

Why is it essential that the mechanisms that activate glycogen synthesis also deactivate glycogen phosphorylase?

Answer 76

These two pathways occur in the same cellular compartment

Question 77

It is advantageous that breakdown of glycogen gives rise to glucose-6-phosphate rather than to glucose because glucose-6-phosphate is already ______. This saves _____ equivalent in the early stages of glycolysis.

Answer 77

phosphorylated
one ATP

Question 78

Briefly outline the role of UDPG in glycogen biosynthesis.

Each glucose residue is added to the growing glycogen molecule by transfer from ______.

Answer 78

UDPG

Question 79

Glycogen synthase is subject to covalent modification and to allosteric control. The enzyme is _______ in its phosphorylated form and ______ when dephosphorylated. AMP is an allosteric ______ of glycogen synthase, whereas ATP and glucose-6-phosphate are allosteric ______.

Answer 79

active
inactive

inhibitor
activators

Question 80

There is a net gain of ______, rather than two, ATP when glycogen, not glucose, is the starting material of glycolysis.

Answer 80

three

Question 81

You are planning to go on a strenuous hike and are advised to eat plenty of high-carbohydrate foods, such as bread and pasta, for several days beforehand. Suggest a reason for the advice.

Eating high-carbohydrate foods for several days before strenuous activity is intended to build up _______ stores in the body. Glycogen will be available to supply required energy.

Answer 81

glycogen
supply

Question 82

What are four possible metabolic fates of glucose-6-phosphate?

Answer 82

Glucose-6-phosphate can be converted to glucose (gluconeogenesis), glycogen, pentose phosphates (pentose phosphate pathway), or pyruvate (glycolysis).

Question 83

If a cell needs NADPH, ______ the reactions of the pentose phosphate pathway take place. If a cell needs ribose-5-phosphate, the ______ portion of the pathway can be bypassed; only the _______ reshuffling reactions take place. The pentose phosphate pathway does not have a significant effect on the cell’s supply of _____.

Answer 83

all
oxidative, nonoxidative

ATP

Question 84

Acyl groups are esterified to ________ to cross the inner mitochondrial membrane.

Answer 84

carnitine

Question 85

Acyl-CoA dehydrogenase removes hydrogens from adjacent carbons, creating a _____ and using _____ as coenzyme.

β-Hydroxy-CoA dehydrogenase oxidizes an alcohol group to a ketone group and uses _____ as a coenzyme.

Answer 85

double bond, FAD

NAD+

Question 86

The oxidation of unsaturated fatty acids to acetyl-CoA requires a _______ and an epimerization, reactions that are not found in the oxidation of saturated fatty acids.

Answer 86

cis–trans isomerization

Question 87

What are the unique enzymes needed to β-oxidize a monounsaturated fatty acid?

For a monounsaturated fatty acid, an additional enzyme is needed, the __________.

Answer 87

enoyl-CoA isomerase

Question 88

How many cycles of β-oxidation are required to process a fatty acid with 17 carbons?

Answer 88

It would take seven cycles of β-oxidation to release 14 carbons as acetyl-CoA, with the last three being released as propionyl-CoA.

Question 89

Briefly outline the reactions involved in ketone production.

Answer 89

Two acetyl-CoA molecules combine to form acetoacetyl-CoA. This can then release coenzyme A to yield acetoacetate, which can be converted either to β–hydroxybutyrate or to acetone.

Question 90

What is the metabolic importance of malonyl-CoA?

It is a molecule that commits itself to fatty acid _______. It is also a potent inhibitor of carnitine acyltransferase I, thereby shutting down ________.

Answer 90

synthesis
β-oxidation

Question 91

How is ACP similar to coenzyme A? How is it different?

Both have a ________ group at the active end. In coenzyme A, this group is attached to _______; in ACP, it is attached to a _______ of a protein.

Answer 91

phosphopantetheine

-phospho-AMP
serine residue

Question 92

Carnitine functions as a ‘shuttle’ for our fatty acyl-CoA molecules to use in order to cross the mitochondrial membrane. The thioester bond on fatty acyls will be hydrolyzed to transfer the molecule onto the carnitine, which will then cross into the mitochondria where Coenzyme A will be ______ to the fatty acid to once again become ______ that can be subjected to _______.

Answer 92

re-attached
fatty acyl CoA
beta oxidation

Question 93

Acetyl-CoA Carboxylase I:
Malonyl-CoA is formed using biotin and ATP to fix ______ to ________, generating the _______ unit used to extend
the fatty acid chain.

Answer 93

HCO3-, Acetyl-CoA
3-carbon

Question 94

Transacylase:
An acetyl-CoA or growing fatty acid chain is transferred to the acyl carrier protein (ACP), which then transfers it to
______. Malonyl-CoA is then transferred to _____.

Answer 94

ketoacyl synthase
ACP

Question 95

Ketoacyl Synthase
Catalyzes a Claisen _______ between acetyl-CoA/FA chain and the malonyl group, releasing _____ in the process

Answer 95

condensation
CO2

Question 96

Ketoacyl Reductase
______ is used to reduce the carbonyl from the acetyl-CoA remnant to a hydroxyl group.

Answer 96

NADPH

Question 97

Hydroxyacyldehydratase
Catalyzes the dehydration of water between carbons 2 and 3, forming a new ______

Answer 97

C=C double bond

Question 98

Enoyl Reductase
NADPH is used to reduce the ________ formed in the previous step to a single bond. At this point, the ______ has successfully been added to the growing chain.

Answer 98

carbon-carbon double-bond
acetyl-CoA

Question 99

Steps in the repeating fatty acid synthesis cycle:

Step 1 is a(n) _______, which results in a new, longer chain with two _______ bound to our ACP group.
Step 2 is a(n) ______, which results in a(n) ______ group.
Step 3 is a(n) ________, which results in a(n) _______ group.
Step 4 is a(n) _______, which results in a(n) (n+2 ) fatty acid chain

Answer 99

condensation, carbonyls

Reduction, hydroxyl

Dehydration, alkene (C=C)

Reduction

Question 100

Explain why the formation of UDP-glucose in your body is generally considered irreversible and occurs in the direction of UDP-Glucose formation?

The hydrolysis of ______ releases a _____ amount of free energy, which will drive the reaction forward enough to effectively make it irreversible.

Answer 100

pyrophosphate (PPi)
large

Question 101

What is the function of UDP-Glucose?
UDP-glucose is the residue that is added to a growing glycogen chain. Upon being added to glycogen, you will have a glycogen molecule with ____ residues and a free _____ molecule.

Answer 101

(n+1) glucose
UDP

Question 102

Which enzyme is the primary enzyme for regulating cholesterol synthesis?

Answer 102

HMG-CoA reductase. This enzyme catalyzes the creation of mevalonate from HMG-CoA. It uses 2 NADPH.

Question 103

HMG-CoA reductase is regulated at four levels:

Answer 103

1. Regulated at level of transcription: stimulating synthesis of mRNA needed to synthesize this protein
2. Regulated at level of translation: The rate of translation of the reductase mRNA is controlled by metabolites of mevalonate and dietary cholesterol.
3. Proteolytic degradation of the enzyme: Increases in cholesterol concentration result in the proteolytic degradation of the reductase.
4. Phosphorylation of the reductase by AMP-dependent kinase inactivates the enzyme.

Question 104

State one common class of drugs used to treat high cholesterol and state how it works.

Statins which are HMG-CoA reductase inhibitors. They are similar in structure to HMG-CoA and work to ______ inhibit HMG-CoA reductase by binding the enzyme at the active site.

Answer 104

competitively

Question 105

Describe how VLDL that is released by the liver becomes LDL as it moves through the bloodstream.

Answer 105

Lipases break down fatty acids located in the VLDLs to move fatty acids into the cells. As this occurs more and more, the TAG content of these carriers decreases which will shift its composition to resemble that of LDL.

Question 106

Describe the three steps of how LDL deliver cholesterol to peripheral tissues.

Answer 106

1) LDL will find and bind to an LDL receptor on a cell surface.
2) The LDL receptor will partake in endocytosis of the LDL molecule and bring this into the cell.
3) The LDL is hydrolyzed in lysosomes to release its content and the LDL receptor will float back to the cell surface
to accept another LDL.

Question 107

alpha-1,6-glucosidase releases ______

Answer 107

free glucose

Question 108

Glycogenin generates the ______ needed for chain elongation

Answer 108

primer

Question 109

Glycogen synthase catalyzes _______ of the glycogen chains

Answer 109

elongation

Question 110

Phosphoglucomutase converts _______ to _________

Answer 110

glucose 1-phosphate, glucose 6-phosphate

Question 111

Glycogen phosphorylase releases _______

Answer 111

glucose 1-phosphate

Question 112

Which of the following are the two domains in the debranching enzyme involved in glycogen breakdown?

Answer 112

Transferase and a-1,6-glucosidase

Question 113

Glucagon is associated with glycogen _______ and activates ______, which acts to ________ enzymes. Thus, in presence of glucagon, glycogen phosphorylase is ______ and _______, with the opposite being true of glycogen synthase.

Answer 113

breakdown, protein kinase A
phosphorylate
activated
phosphorylated

Question 114

The four repeated steps of fatty acid synthesis, in order, are _________.

Answer 114

condensation, reduction, dehydration, reduction