Biochem

Front 1

Fatty acid synthesis occurs in ______ compartment of the cell

Back 1

The cytosol of liver and adipose tissues

Front 2

A hormone that stimulates fatty acid synthesis is______

Back 2

insulin, which activates Acetyl-CoA carboxylase

Front 3

Acetyl CoA carboxylase has a covalently bound prosthetic group called ______

Back 3

Biotin

Front 4

Name the substrates that are required by the acetyl CoA carboxylase to form malonyl CoA.

Back 4

Acetyl-Coa

Bicarbonate

ATP

**ACC has a covalently bound biotin moiety which participates in the carboxylation rxn in forming malonyl CoA ***

Front 5

Describe how mitochondrial acetyl CoA is made available in the cytosol.

Back 5

Mitochondrial Acetyl-CoA cannot diffuse naturally through a transferase protein. Citrate Synthase will use Acetyl-CoA and Oxaloacetate to form Citrate, which can be transported across the membrane via a citrate transporter. Once in the cytosol, citrate lyase will separate Acetyl-CoA and Oxaloaceetate. Then Malate dehydrogenase will convert Oxaloacetate into Malate which can then yield NADH through its coversion to pyruvate

Front 6

Name the reductant that is required for the fatty acid synthesis ___?

Back 6

NADPH

Front 7

Name the substrate and products of malic enzyme.

Back 7

Malic enzyme uses malate to conver it to pyruvate, yielding NADPH in the process

Front 8

Name the vitamin derivative that is part of the ACP portion of the fatty acid synthase complex___?

Back 8

Biotin

Front 9

Starting from Acetyl-CoA and malonyl-CoA name the steps that are involved in the synthesis of palmitate.

Back 9

Acetyl-CoA is first converted into Malonyl-CoA through Acetyl-CoA carboxylase.Using carbonate and ATP.

At the first step, Acetyl-CoA will attach itself to the FAS enzyme.

Secondly, the Acetyl-CoA enzyme complex will join w/ Malonyl-CoA and ACP using Malonyl Transferase. It will then undergo various reductions and dehydrations to yield Palmitoyl-CoA. The CoA and enzyme will be removed by Thioesterase-I and we will end up with Palmitate.

Front 10

Name the enzyme domain that releases palmitate from the fatty acid synthase complex

Back 10

Thioesterase-I domain will cleave palmitate from the FAS complex.

Front 11

Name the enzyme that is expressed during lactation in mammary glands that is relevant to fatty acid synthesis.

Back 11

Thioesterase II

Front 12

Name the fatty acids that are relased by thioesterase II. (2)

Back 12

This enzyme will cleave the growing FA chain from FAS, yielding either :

1. Capric (C10)

2. Myristic(C12)

*These compounds are much easier for babies to digest*

Front 13

Name two essential fatty acids.

Back 13

Linoleic Acid

Linolenic Acid

Front 14

True/False:

All naturally occuring double bonds of fatty acids are of CIS configuration.

Back 14

TRUE

Front 15

Linoleic acid is the precursor for the biosynthesis of ____

Back 15

Arachidonic Acid

Front 16

Storage form of fatty acid is?

Back 16

Triglycerides

Front 17

Triglycerides are stored in ____ tissue

Back 17

Adipose

Front 18

Name the precursors for the synthesis of triglyceride?

Back 18

Acetyl-CoA

Front 19

The backbone compound, on which fatty acids are esterified to form triglycerides are

Back 19

Triglycerides are attached to a glycerol backbone.

Front 20

Before beta-Oxidation, activated fatty acids are esterified to ____ compound so that it can be transported from the cytosol to the mitochondria.

Back 20

In order to cross the mito membrane, FA must be first converted to Fatty Acyl-Carnitine, catalyzed by Carnitine Acyltransferase I. Once transported across the membrane it is then converted back to FA by Carnitine Acyl transferase II.

Front 21

Name 3 energy related compounds that are produced upon B-Oxidationof fatty acids.

Back 21

Upon Beta-Oxidation of FA:

-7 FADH2

7 NADH

-8 Acetyl-CoA

Are produced to create ATP

Total of 131 ATP gross, and 129 ATP net

Front 22

Name an enzyme that is located in the mitochondrial matrix that cleaves fatty acyl-carnitine

Back 22

Carnitine Acyl transferase II

Front 23

Upon complete oxidation of stearic acid, myristic acid and lauric acid, how many moles of ATP are formed respectively?

Back 23

131 ATP

Front 24

Name a methylated fatty acid that is derived from dairy products.

Back 24

Phytanic Acid

Front 25

Name an enzyme that uses vitamin B12 derivative as a coenzyme in the enzyme catalysis

Back 25

Mutase

Front 26

Name a 3 carbon compound that is formed from the oxidation of odd chain fatty acids.

Back 26

Odd chain FA oxidation will result in NADH, FADH2, and Propionyl-CoA, which can be converted into Succinyl-CoA to enter the TCA and yield 6 more ATP equivalents.

Front 27

Name 2 enzymes that convert propionyl CoA into succinyl CoA

Back 27

The conversion of Propionyl-CoA into Succinyl-CoA is catalyzed first by Propionyl-CoA Carboxylase. Then a Methyl Malonyl CoA mutase with a Vitamin B12 as a cofactor (cobalamin, prosthetic group) will yield the Succinyl-CoA

Front 28

Name 2 carboxylases that require biotin as a coenzyme

Back 28

1. Acetyl-CoA Carboxylase

2. Propionyl-CoA Carboxylase

Front 29

Name a compound that is catabolized by a-oxidation

Back 29

Phytanic Acid is oxidized by alpha oxidation because of the methyl groups that are attached. The methyl groups do not allow this to be catalyzed by Acyl-CoA dehydrogenase. This compounds is broken down and releases CO2 as a byproduct.

Front 30

Name an allosteric activator and and inhibitor of acetyl CoA carboxylase.

Back 30

Activator: Citrate and Insulin

Inhibitor: Fattyacid-CoA and phosphate.

Front 31

Carnitine Acyl-Transferase is inhibited by ____

Back 31

Malonyl CoA

Front 32

Name a hormone that triggers the catabolism of fats.

Back 32

Glucagon, secreted by alpha cells of the pancrease will trigger catabolism of triglycerides

Front 33

Phosphorylation of acetyl CoA carboxylase by protein kinse A inactivates the enzyme.

True/False?

Back 33

False. Insulin will activate a phosphatase that will DEphosphorylate Acetyl-CoA carboxylase into its active form

Front 34

Phosphorylation of hormone sensitive lipase by protein kinase A activates the enzyme. True or False?

Back 34

True.

Glucagon will stimulate cAMP which will activate Protein Kinase A (PKA) to phosphorylate enzymes such as hormone sensitive lipase and Carnitine Acycltransferase I.

Front 35

Name the defect in Refsum's disease.

Back 35

Refsum's disease involves the inability to degrade Phytanic acid because of a deficiency in the alpha-hydroxylating enzyme.

As a result, lipids build up in the plasma and tissues, causing neurological damage.

Front 36

In Sudden Infant Death Syndrome the enzyme that is defective is _____?

Back 36

SIDS invloves the inability to beak down medium chain FA, because of a defiency in the medium chain fatty acyl-CoA dehydrogenase enzyme.

Front 37

Name the two conditions that would result in methyl malonic acedemia (aciduria)

Back 37

There are two types of disease manifestations: In one case methylmalonyl CoA mutase is missing. In some patients conversion of Vitamin B12 into coenzyme form is missing. In either case it causes metabolic acidosis and mental retardation due to the improper utiliztion of odd chain fatty acids.

Front 38

Define Obesity

Back 38

It is the condition that results in a body mass index more than 30 kg/m2. Clinically, this involves hypertension, gall stones, and diabetes.

Front 39

Name a natural and an artificial compound that inhibits fatty acid synthase

Back 39

The naturally occuring inhibitor for FAS is cerulinin

A synthetic equivalent of cerulinin has been named as C75.

Front 40

Malonyl-CoA inhibits the production of a neuropeptide hormone called..

Back 40

NPY or Neuropeptide Y

Front 41

True or false

Neuropeptide Y signals the inhibition of feeding?

Back 41

False. As Malonyl CoA is built up due to the inhibition of FAS, Neuropeptide Y synthesis is inhibited. It is this inhibition of NPY synthesis that will inhibit feeding. So, NPY itself does not inhibit feeding, but rather promotes feeding.

Front 42

Describe diabetic ketoacidosis

Back 42

Ketoacidosis is the production of ketone bodies (acetoacetate, beta-hydroxybutate, and acetone) in excess from what the liver needs. This usually occurs under starvation or Diabetes Type I. Because of glucose starvation in the tissues, the body must oxidize the FA as sources for energy.

Front 43

Name the two enzymes that convert alcohol into acetate.

Back 43

1. Alcohol Dehydrogenae

2. Acetaldehyde dehydrogenase

*NAD+ is the oxidant.

*Acetate can be used as a small energy source as the acetate is converted into Acetyl-CoA in the mitochondria, and then directly enters the TCA cycle

Front 44

Name the reductant that is produced during the oxidation of alcohol

Back 44

NAD+ is used during the oxidation of alcohol

Front 45

How many moles of ATP are produced upon complete oxidation of ethanol?

Back 45

In the conversion of ethanol to acetate, two NADH are produced to yield a potential 6 ATP. But, one ATP is used during the conversion process, so a net result of 5 ATP is produced

Front 46

Name a few compounds that are metabolized by omega-oxidation pathway

Back 46

--fatty acids with 6-10 carbons.

Front 47

Upon complete oxidation of capric acid, how many moles of net ATP are produced?

Back 47

--78 moles of net ATP are produced.

Front 48

What are the advantages of having fatty acid synthase as a multi enzyme complex as seen in mammals as opposed to individual polypeptides as seen in bacteria?

Back 48

?

Front 49

Explain why fat storage is energetically better compared to glycogen?

Back 49

Fat produces 9 kcal/mole (~ 131 ATP for palmitate), whereas glycogen only produces 2 ATP/mole through anaerobic metabolism and ~36 ATP/mole through aerobic metabolism.

Front 50

Explain how ketone bodies can serve as an energy source in brain during starvation.

Back 50

--Ketone bodies can be transferred to extrahepatic tissue. Acetoacetate with the addition of succinyl CoA becomes acetoacetyl CoA (by thiophorase), then becomes 2 Acetyl CoA catalyzed by Thiokinase. Acetyl CoA can then enter the TCA cycle.

Front 51

Explain why carnitine palmitoyltransferase I deficiency leads to hypoketosis?

Back 51

?

Front 52

Why are alocholholics hypoglycemic

Back 52

?

Front 53

Is the NADH/NAD+ ratio high or low in alcoholics?

Back 53

--the NADH/NAD+ ratio is low, due to the production of 3-hydroxybutyrate. Usually NADH/NAD+ ratio is high in the liver.

Front 54

Explain why high NADH production in alcoholics leads to lipid accumulation

Back 54

?

Front 55

What are omega-3 ad omega 6 fatty acids?

Back 55

Omega-3 fatty acids (also called ω-3 fatty acids or n-3 fatty acids[1]) are polyunsaturated fatty acids (PUFAs) with a double bond (C=C) at the third carbon atom from the end of the carbon chain

** Linolenic Acid**

Same with Omega 6:

Linoleic Acid

Front 56

Describe the citrate lyase catalyzed rxn

Back 56

Citrate is transported via a transporter from the mito chondria into the cytosol. Citrate lyase using CoA cleaves citrate into OAA and acetyl CoA.

Front 57

Which compound has a sweet fruity odor in type I diabetics?

Back 57

Ketone bodies

Front 58

High NADH/NAD+ in alcoholics results in the production of (2)

Back 58

Acetaldehyde

Acetate

Front 59

A person with a deficiency of vitamin B12 is recommended to avoid what type of food?

Back 59

Fatty foods

Front 60

A person with biotin deficiency cannot metabolize _____ fatty acid

Back 60

propionyl CoA - odd number of carbons

Front 61

Explain obesity, overweight, underweight in terms of BMI

Back 61

BMI of over 25 is considered overweight, over 30 is considered obese (although this number keeps

increasing as more and more people fall into the obese category), and 17-19 is underweight.

Front 62

What compound is the source of all carbons in cholesterol?

Back 62

Acetyl-CoA

In general terms the synthesis starts at acetyl-CoA, and all carbons in cholesteral arise from acetyl-CoA

Front 63

Cholesterol is the precursor for what 4 major types of compounds?

Back 63

Cholesterol is a precursor for compounds such as:

1. Bile Acids

2. Vitamin D

3. Corticosteroids

4. Sex Hormones

Front 64

What are the five stages in cholesterol biosynthesis that we discussed and their products?

Back 64

The five stages of cholesterol biosynthesis are:

1.Mevalonate

Product: Mevalonate

2.Synthesis of Isoprenoid units

Product: Isopentenyl pyrophosphate

3.Synthesis of Squalene

Product: Squalene

4.Conversion to Lanosterol

Product: Lanosterol

5. Conversion to Cholesterol

Product: Cholesterol

Front 65

What are the substrate, enzyme, and product of the rate-limiting step of cholesterol synthesis?

Back 65

The reaction is as follows:

HMG-CoA + 2NADPH + 2H+ --> Mevalonate + 2NADP+ CoASH

Substrate: HMG-CoA, 2NADPH

Enzyme: HMG-CoA reductase

Product: Mevalonate, 2NADP+, CoASH

Front 66

What are the different means by which cholesterol synthesis is controlled naturally?

Back 66

It can be controlled by the bicyclic control mechanism. Increased insuiln, will cause a decrease in cAMP, which will increase cholesterol levels (levels of HMG-CoA Reductase increase).

Whereas an increase in glucagon will cause cAMP levels to increase, reducing cholesterol levels (levels ofHMG-CoA Reductase decrease).

Synthesis can also be controlled genetically, HMG CoA reductase has a sterol unit on its DNA that will inhibit the synthesis of mRNA for HMG-CoA reductase.

Finally, HMG-CoA reductase can be inhibited by cholesterol itself. There is a hydrophobic domain of HMGR in the ER membrane that can accelerate the degradation of HMGR

Front 67

What are the main dietary sources of cholesterol? How does our body get rid of cholesterol?

Back 67

Dietary sources include:

meat, fish, dairy, and poultry products.

Cholesterol is removed from our system primarily by bile salts. Cholesterol is usually moved into the outer tissues by LDL. Then HDL will take the cholesterol from the outer tissues and bring it to the liver, where most of it excrted. Bile salts excreted from pancreas will bind to the cholesterol and it is passed through the intestines.

Front 68

What are bile salts and their use? What is the route of circulation for their re-absororption?

Back 68

Bile salts are primarily recirculated when they are taken up by the portal vein in the small intestine. They will then be taken to the liver and sent back to the pancreas

Front 69

In what two ways is pharmaceutical intervention used to lower patient cholesterol levels?

Back 69

Cholesterol levels can be affected by pharmaceutical intervention at the rate limiting step. Mevacor or "statin" drugs can mimic HMG-CoA reductase intermediates and inhibit this enzyme competitively. This usually triggers a mechanism that causes LDL receptors to increase, thus circulating LDL and cholesterol levels drop.

Oral treatment w/ resisns (cholestyramine and cholestipol) remove bile salts, prevents recirculation causing serum cholesterol to drop. Also, pharmaceuticals can mimic the actions of bile salts. Non-digestible compounds that can bind to cholesterol can remove cholesterol through intestinal excretions.

Front 70

What are the roles of HDL and LDL w/ respect to cholesterol?

Back 70

HDL removes cholesteral from the outer tissues and brings it into the liver for excretions w/ the aid of LCAT. LDL will store cholesterol in the outer tissues with the aid of ACAT.