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Biochemistry (aka hell) > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

lipolysis

A

fatty acid degradation via B- oxidation

  • TG cycle
  • peroxisomes
  • ketone bodies
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2
Q

fatty acid biosynthesis

A
  • regulation
  • membrane lipid metabolism
  • isoprenoid metabolism
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3
Q

what are 3 sources of fatty acids in animals

A
  • dietary triacylglycerois –>chylomicrons
  • triacylglycerols stored in adipose tissue and released in response to hormones (glucagon, eprinephrine) –> fatty acids –>albumin
  • triacylglycerols synthesized in the liver from carbohydrates and exported –> VLDL particles
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4
Q

“Digestion and aborption of triacylglycerols in small intestine”

fatty acids are important and efficient energy source for many cells

after triacylglycerol molecules are ingested, they are mixed with ____________

A

bile salts

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5
Q

digestion and absorption of triacylglycerols in the small intestine _____________pathway

A

exogenous

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6
Q

The ____________ is a mechanism that regulates the level of fatty acids available to the body for energy generation

A

triacylglycerol cycle

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7
Q

triglycerides

-triglycerides are a highly concentrated store of energy

A
  • 9kcal/g vs 4 kcal/g of glycogen

- glycogen is also highly hydrated, 2 g H2O/g

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8
Q

Depending on the animals current metabolic needs, fatty acids may be:

A
  • converted to triacylglycerols
  • degraded to generate energy
  • used for membrane synthesis
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9
Q

dietary triacylglycerols must be broken down before being absorbed by the intestines

_____, which act as detergents, are used to solubilize the triacylglycerols

A

bile salts

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10
Q

______________: hydrolyze the ester bond of the triacylglycerols while in the micelles

A

pancreatic lipases

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11
Q

in the intestinal mucosal cells, the fatty acids and monoacylglycerides are resynthesize into triacylglycerides and packed into ________________

A

chylomicrons

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12
Q

glycerol-3- phosphate or dihydroxyacetone phosphate reacts sequentially with three molecules of _________. Acyl-CoA molecules are fatty acid esters of CoASH

A

acyl CoA

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13
Q

_______________ is an abbreviated version of gluconeogeneis. This is where glycerol-3-phosphate is synthesized from substrates other than glucose or glycerol

A

glyceroneogenesis

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14
Q

when energy reserves are low, the body fat stores are mobilized in a process termed _____________.

  • this occurs in adipose tissue during fasting, during vigorous exercise, and in response to stress
  • fatty acid binding proteins are responsible for transporting the fatty acids into target organelles
A

lipolysis

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15
Q

lipid –>degration

A

triacylglyceride (use of lipase) —> glycerol –> fatty acids

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16
Q

lipolysis generates ____________ and _______

A

fatty acids and glycerol

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17
Q

Breakdown of triacylglycerols

-the glycerol is absorbed by the liver and converted to ______ intermediates

A

glycoytic

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18
Q

upon entering the cell cytoplasm, fatty acids are activated by attachment of _________

A

coenzyme A

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19
Q

transport into mitochondrial matrix via carnitine linkage

A
  1. acyl-CoA converted into acylcarnitine
  2. carrier protein transfers acylcarnitine into matrix
  3. acyl-CoA regenerated
  4. Carnitine recycled to intermembrane space
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20
Q

_________ is responsible for transporting acyl carnitine into the inner membrane of the mitochondria

A

acyl carnitine translocase

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21
Q

what are the four steps of fatty acid degradation that are repeated?

A
  1. OXIDATION of B carbon, catalyzed by ACYL COA DEHYDROGENASE
  2. HYDRATION of trans-2-enoyl CoA by ENOYL COA HYDRATASE
  3. OXIDATION of L-2-hydroxyacyl CoA by L-3-HYDROXYACYL DEHYDROGENASE
  4. CLEAVAGE of the 3-ketoacyl CoA by THIOLASE forms acytl-CoA and a fatty acid chain two carbons shorter
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22
Q

fatty acid degradation is also called ____________

A

B- oxidation

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23
Q

The reaction for one round of B-oxidation is?

where NADHx2.5
where FADHx1.5

A

make 31 NADH total
Makes 15 FADH2 total
takes 2 ATP to do

106 ATP total generated

processing of the products of the complete reaction by cellular respiration would generate 106 molecules of ATP

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24
Q

When does the generation of H2O occur?

A

it occurs when O2 is reduced in electron transport as well as formation of H2O in ATP synthesis reaction of oxidative phosphorylation

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25
Q

the degradation of MONOUNSATURATED fatty acid occurs with what enyzme?

A

cis-delta- enoyl CoA isomerase

26
Q

POLYUNSATURATED fatty acid require isomerase and reductase. Which ones

A 
Forexample Linoleoyl CoA 
uses:
- cis-delta-enoyl coA isomerase
-cis-delta-enoyl coA isomerase
-2,4- dienoyl coA reductase
27
Q

odd-chain fatty acids yield ______ in the final thiolysis step.

_______________ a biotin enzyme, adds a carbon to propionyl CoA to for methylmalonyl CoA

Succinyl CoA, a citric acid cycle component, is subsequently formed from methylmalonyl CoA by __________ a vitamen B12 requiring enzyme

A

propionyl CoA

propionyl carboxylase

methylmalonyl CoA mutase

28
Q

alpha oxidation

degradation of branched - chain fatty acids, takes place in the _________-

A

peroxisomes

29
Q

Ketone bodies are another fuel source derived from fats.

Ketone bodiy synthesis takes place in the liver

A

ketone bodies-acetoacetate, 3-hydroxybutrate, and acetone-are synthesized from acetyl CoA in liver mitochondria and secreted into the blood for used as fuel b some tissues such as heart muscle

30
Q

the formation of ketone bodies involves what enzymes?

A

Enzymes:

  • thiolase
  • HMG CoA synthase
  • HMG CoA lyase
  • d-3-hydroxybutyrate dehydrogenase.
  • Acetoacetate spontaneously decarboxylates to form acetone.
31
Q

Ketone bodies

acetoacetate breaks down into what components?

A

D-3- hydroxy butyrate

acetone

32
Q

The uilization of D-3-hydroxybutyrate and acetoacetate as a fuel uses what enzymes?

A

dehydrogenase

CoA transferase

Thiolase

To finally yield –> 2 acetyl CoA

33
Q

Why can’t Acteyl CoA be used to generate glucose in citric acid cycle?

A

Pyruvate (3 chain carbon) is the end product of glycolsysis, pyruvate later get converted to a Acetyl CoA (2 chain carbon) through an enzyme called pyruvatedehydrogenase… If it was to generate glucose then the reaction would have to be able to happen in reverse. However this isn’t possible because there is no enzyme that does the opposite of pyruvatedehydrogenase.

Therefore animals cannot convert fatty acids into glucose

34
Q

_________ results when insulin is absent

A

diabetic ketosis

35
Q

fatty acid synthesis takes place in three stages:

A
  1. Transfer of acetyl CoA out of the mitochondria into the cytoplasm. Citrate is transported into the cytoplasm and cleaved into oxaloacetate and acetyl CoA.

2 .Activation of acetyl CoA to form malonyl CoA.

  1. Repetitive addition and reduction of two carbon units to synthesize C16 fatty acid. Synthesis occurs on an acyl carrier protein.
36
Q
  1. citrate shuttle

________ is synthesized in the mitochondrial matrix, whereas fatty acids are synthesized in the ________

Acetyl-CoA units are shuttled out of the mitochondrial matrix as citrate

A

acetyl-CoA is synthesized in the mitochondrial matrix, whearas fatty acids are synthesized in the cytosol. Acetyl-CoA units are shuttled out of the mitochondrial matrix as citrate

37
Q

The malate dehydrogenase and NADP^+ linked malate enzyme reactions of the citrate shuttle exchange ________ for ________

A

NADH for NADPH

38
Q
  1. formation of malonyl coenzyme A

formation of ________ is the committed step in fatty acid synthesis

Acetyl-CoA carboxylase

A

malonly-CoA =commited step in fatty acid synthesis

Acetyl-CoA Carboxylase
-The carboxylation of acetyl-CoA to form malonyl-CoA is catalyzed by acetyl-CoA carboxylase, ACC

  • ACC is found in most organisms
  • Mammalian ACC contains two subunits each with a biotin cofactor
39
Q

Regulation of fatty acid synthesis

  • regulation of acetyl carboxylase
  • GLOBAL
  • +insulin
  • -glucagon
  • -epinphrine
  • LOCAL
    • citrate
  • -palmitoyl CoA
  • -AMPl
A

know what are positive and negative regulators

40
Q

The remaining reactions of fatty acid synthetase takes place on the ___________

A

fatty acid synthetase multienzyme comlex (FAS)

41
Q

____________, a complex of enzymes, catalyzes the formation of fatty acids.

Fatty acid synthesis occurs on the acyl carrier protein (ACP), a polypeptide linked to CoA. Intermediates are linked to the sulfhydryl group of the CoA attached to ACP.

__________ and _____________ attach substrates to the ACP.

A

fatty acid synthase

acetyl transacylase and malonyl transacyalse

42
Q

the intermediates in fatty acid synthesis are covalently linked to the _________

A

acyl carrier protein (ACP)

43
Q

Elongation

in _______ the enzyme that are involved in elongation are separate proteins;

In __________ the activities all reside on the same polypeptide

A

in bacteria

in higher organisms

44
Q

fatty acid synthesis consists of _______,_______,__________-and_________-

A

condensation, reduction, dehydration, and reduction reactions

45
Q

fatty acid synthesis

___________ catalyzes the condensation of acetyl ACP and malonyl ACP to form acetoacetyl ACP

the next three steps- reduction, dehydration, and another reduction-convert the keto group at carbon 3 to a methylene group (-CH2-) forming buyryl ACP

__________ is the source of reducing power

A

B ketoacyl synthase

NADPH

46
Q

acyl-malonyl ACP condensing enzyme forms ___________

A

acetoacetyl-ACP

47
Q

Elongation

-

A
  • The NADPH is used instead of NADH and FADH2

- The D–enantiomer of Hydroxybutarate is formed instead of the L–enantiomer

48
Q

the elongation cycle is repeated six more times, using malonl-coA each time to produce ____________

a thioesterase then cleaved the palmityl(C16) CoA from ACP

A

palmityl-ACP

49
Q

multifunctional fatty acid synthase.

it is a functional enzyme that is composed of two identical chains
the enzyme consists of two distinct compartments

  1. The __________ compartment, which bind the acetyl and malonyl substrates and condenses them
  2. the _________ compartment, which carrier out the reduction and dehydration activities required for elongation
A
  1. selecting and condensing

2. modification

50
Q

Elongation and unsaturated

Fatty acid synthase cannot generate fatty acids long than ________

longer fatty acids are synthesized by enzymes attached to the endoplasmic reticulum

these enzymes extend palmitate by adding two carbon units, using malonyl CoA as a substrate

A

C16 palmitate

51
Q

Membrane bound enzymes generate unsaturated fatty acids

Enzymes bound to the endoplasmic reticulum introduce double bonds into saturated fatty acids

mammals lack the enzymes that introduce double bonds beyond carbon ___________

____ and ______ are essential fatty acids that must be obtained form the diet

A

carbon 9

linoleate and linolenate

52
Q

Desaturation of stearoyl CoA

Desturase uses electron from ETS
-cytochrome bs
NADH is electron donor

A

General (may not be important)

53
Q

Regulation of intracellular fatty acid metabolism

  • both short- and long term regulatory processes are used
  • in _________ regulation, enzymes are regulated by allosteric effectors, covalent modification (AMPK), and hormones
  • _______ regulation is effected by alteration in gene expression
A
  • in short-term regulation

- long term regulation

54
Q

AMPK- Master regulator

5′-AMP-activated protein kinase is activated by an increase in _________ ratio
Switches anabolic pathways off and catabolic pathways on
Shifts metabolism from energy-consuming processes to energy-generating processes

A
  • AMP/ATP
55
Q

The liver is the primary site of cholesterol synthesis, although most tissues synthesize some cholesterol.

Cholesterol synthesis occurs in 4 stages.

A
  1. Formation of mevalonate from Acteyl-CoA
  2. Isopentyl pyrophosphate is synthesized from mevalonate.
  3. Six molecules of isopentyl pyrophosphate condense to form squalene.
  4. Squalene cyclizes and is converted into cholesterol.

Stage 1 occurs in the cytoplasm and stages 2 and 3 in the endoplasmic reticulum.

56
Q
  1. Formation of HMG-CoA –> Mevalonate

HMG-CoA reductase is a target for some ______________

  1. Formation of Activated isoprene

pyrophosphate is a good ___________ in these nucleophillic substitution reactions

  1. formation of squalene
A

cardiovascular drugs

leaving group

57
Q

cholesterol degrades into ??????/

A

lanosterol, terosterone, estradiol, cortisol, aldosterone, vitamam D, cell membrane, bile salts`

58
Q

cholesterol homeostasis

–> intricate regulation through

A
  1. cholesterol
  2. LDL receptor activity
    3, bile acid synthesis
59
Q

regulation of cholesterol biosynthesis

A

insulin “high glucose”

glucagon “low glucose”

60
Q

_____________are a class of drug that lowers serum cholesterol levels by inhibiting HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis

___________ also interfere with CoQ, a critical molecule in energy generation

A

statins

61
Q

Molecules in meat may increase heart disease risk? describe this study and is it true?

A 
Gut flora (of meat eaters) converts carnitine and choline into trimethylamine and enzymatic oxidation converts this to heart harming molecule TMAO (trimethylamine N-oxide)
Gut microbes do not produce TMAO directly. They convert phosphatidylcholine (a common component of animal products such as meat and eggs) into a foul-smelling gas called trimethylamine; the liver then converts this gas into TMAO. 
L-carnitine passed right through the guts of long-term vegans and vegetarians, leaving their blood practically TMAO-free. When researchers examined volunteers’ stool, they found different groups of bacteria in people who did and didn’t eat meat.

Biochemistry (aka hell) (14 decks)

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