Intro To Lipids And Fatty Acid Oxidation

Front 1

16:0 represents which fatty acid?

Back 1

Palmitic Acid

Front 2

18:0 represents which fatty acid?

Back 2

Stearic Acid

Front 3

18:1 delta 9 represents which fatty acid?

Back 3

Oleic Acid

Front 4

18:2 delta 9,12 represents which fatty acid?

Back 4

Linoleic Acid

Front 5

18:3 delta 9,12,15 represents which fatty acid?

Back 5

Linolenic Acid

Front 6

20:4 delta 5,8,11,14 represents which fatty acid?

Back 6

Arachidonic Acid

Front 7

Name two essential fatty acids. Why are they essential?

Back 7

Linoleic and linolenic acids are essential because they cannot be synthesized de novo, must be gained from diet.

Front 8

What is the defect in MCADD?

Back 8

Medium chain acyl-CoA dehydrogenase deficiency causes abnormal amounts of 8-10 carbon chain fatty acids in the circulation.

Front 9

Describe the structure of a micelle.

Back 9

A micelle is a unilamellar amphipathic molecule with hydrophobic lipid head groups facing outwards towards aqueous media and hydrophobic tails segregated inside.

Front 10

Unsaturated fatty acids have cis or trans double bonds?

Back 10

cis

Front 11

What is saponification?

Back 11

lipid esters + base + heat = salts, long chain fatty acids (12-20 carbons long) + base + heat = soaps

Front 12

Ingested glycerophospholipids and triglycerides are primarily broken down where?

Back 12

Small Intestine

Front 13

Name several enzymes that function in lipid degradation in lysosomes.

Back 13

acid lipase, ceramidase, phospholipase A1 and A2, sphingomyelinase (phospholipase C), esterase, gangliosidase.

Front 14

The products of lipids degraded in the cytoplasm serve as?

Back 14

second messengers

Front 15

Where does phospholipase A1 cleave glycerophospholipids?

Back 15

the ester of the alpha chain

Front 16

Where does phospholipase A2 cleave glycerophospholipids?

Back 16

the ester of the beta chain

Front 17

Where does phospholipase C cleave glycerophospholipids?

Back 17

between the O and P of the phosphate proximal to the glycerol backbone

Front 18

where does phospholipase D cleave glycerophospholipids?

Back 18

between the O and P of the phosphate distal to the glycerol backbone

Front 19

What is the first step in fatty acids degradation? What species and enzymes are required for it?

Back 19

Activation of the fatty acid by attaching a CoA molecule via acyl-CoA sythetase (thiokinase). consumes an ATP -> AMP (equivalent of 2ATP consumed)

Front 20

Where does fatty acid activation occur?

Back 20

Outside of the miochondria in the cytoplasm.

Front 21

How does Acyl-CoA pass through inner mitochondrial membrane?

Back 21

carnitine acylcarnitine translocase

Front 22

what must happen to acyl-CoA so that it can pass through inner mitochondrial membrane?

Back 22

it must be esterified to carnitine by the enzyme carnitine palmitoyl transferase I

Front 23

what does carnitine palmitoyl transferase II do?

Back 23

it removes the carnitine from acyl-CoA so that beta oxidation can proceed

Front 24

malonyl Co-A

Back 24

1)precursor in fatty acid synthesis 2)inhibits carnitine palmitoyl transferase I thereby inhibiting beta oxidation of fatty acids

Front 25

what is the first step of beta oxidation in the mitochondria?

Back 25

acyl-CoA dehydrogenase oxidizes fatty acyl-CoA, introducing a double bond between the alpha and beta carbons and reducing an FAD+ to FADH2.

Front 26

What is the second step of beta oxidation in mitochondria?

Back 26

enoyl CoA hydratase adds water across the double bond to give 3-hydroxyacyl CoA

Front 27

What is the third step of beta oxidation in mitochondria?

Back 27

3-hydroxyacyl CoA dehydrogenase oxidizes the beta carbon, making a C=O double bond and reducing NAD+ to NADH + H

Front 28

What is the fourth step of beta oxidation in mitochondria?

Back 28

acetyl-CoA acetyltransferase (thiolase) adds CoA to the beta carbon giving rise to an acetyl CoA and an acyl fatty acid containing two less carbons

Front 29

How many net ATP are derived from the beta oxidation of palmitoyl CoA?

Back 29

106 ATP

Front 30

How many NADH are derived from the beta oxidation of Stearic Acid (including those from the TCA cycle)?

Back 30

35 NADH

Front 31

How many FADH2 are derived from the beta oxidation of Stearic Acid (including those from the TCA cycle of acetyl-CoA)?

Back 31

17 FADH2

Front 32

Which enzyme in the beta oxidation pathway reduces an FAD+ to FADH2

Back 32

Acyl-CoA dehydrogenase

Front 33

Which enzyme in the beta oxidation pathway reduces a NAD+ to NADH + H?

Back 33

3-hydroxyacyl CoA dehydrogenase

Front 34

Where does beta oxidation of fatty acids occur?

Back 34

most tissues except for the brain

Front 35

Where are ketone bodies formed?

Back 35

liver mitochondria

Front 36

How is HMG-CoA formed?

Back 36

The enzyme HMG-CoA synthase combines acetoacetyl CoA and Acetyl CoA

Front 37

What happens to HMG-CoA in the fed state?

Back 37

it is converted to cholesterol

Front 38

What happens to HMG-CoA during fasting? Using what enzyme?

Back 38

it is converted to acetoacetate via HMG-CoA lyase

Front 39

The reaction of HMG-CoA with HMG-CoA lyase yields?

Back 39

acetoacetate and acetyl CoA

Front 40

Name the three ketone bodies created during fasting.

Back 40

acetoacetate, acetone, and beta-hydroxybutyrate

Front 41

How is beta-hydroxybutyrate formed?

Back 41

acetoacetate reacts with beta-hydroxybutyrate reductase, consuming an NADH molecule

Front 42

what happens to blood pH during starvation? why?

Back 42

blood pH decreases because of the production of excessive amounts of ketone bodies

Front 43

what for and where are ketone bodies used?

Back 43

they are used as energy sources in extrahepatic tissues

Front 44

how are ketone bodies degraded in extrahepatic tissue?

Back 44

beta-hydroxybutyrate is oxidized to acetoacetate. acetoacetate is activated when succinyl-CoA donates its CoA to yield acetoacetyl-CoA and succinate. acetoacetyl-CoA requires only one enzyme (thiolase) to break into 2 Acetyl Co-A molecules that can be further metabolized to ATP via the TCA cycle.

Front 45

If only thiolase enzyme is used, how many ATP are derived from one molecule of acetoacetate?

Back 45

20 ATP

Front 46

If the entire beta oxidation process is used on one molecule of acetoacetate, how many ATP are derived?

Back 46

24 ATP

Front 47

During shorter periods of fasting, what is the brain's principal source of energy? How does it differ during starvation?

Back 47

During fasting, the brain consumes glucose derived from the breakdown of muscle proteins. During starvation, because the body cannot survive if the brain consumes so much muscle protein, it is forced to consume ketone bodies for energy.

Front 48

During starvation, what compounds can be found in the urine?

Back 48

ketone bodies

Front 49

During periods of fasting, where does the heart, kidney, and other muscle derive its energy?

Back 49

from the oxidation of free faty acids and from the degredation of ketone bodies

Front 50

In severe uncontrolled diabetes, from what compounds is energy derived?

Back 50

escessive amounts of glucose are derived from the breakdown of muscle protein to power the brain and blood and excessive amounts of fatty acids are consumed by other tissues in the form of free fatty acids and ketone bodies

Front 51

Why is coma a common occurence in patients with severe uncontrolled diabetes?

Back 51

Because of elevated levels of ketone bodies in the blood, ketonemia results, lowering the pH of the blood and leadin to coma.

Front 52

What distinguishes starvation state from uncontrolled diabetes?

Back 52

Both situations result in urine excretion of extra ketone bodies but no excess glucose is excreted in a starvation state (it is all used by the blood) like it is in diabetics.

Front 53

How does beta oxidation of fatty acis containing odd numbers of carbons differ from even numbered carbon?

Back 53

Beta oxidation is the same for odd numbered carbon fatty acids until a terminal 3 carbon fragment (propionyl CoA) remains. Propionyl CoA is carboxylated with propionyl-CoA carboxylase and the cofactor biotin to methylmalonyl-CoA (this step consumes an ATP) and then methylmalonyl-CoA is rearranged to succinyl CoA (an intermediate of the TCA cycle) via methylmalonyl-coA mutase and the cofactor B12.

Front 54

Describe alpha oxidation of fatty acids.

Back 54

RCH2COOH + monooxygenase + O2 + Fe2+ + ascorbic acid -> alpha hydroxy fatty acid (added an OH) + dehydrogenase + NAD+ -> carboxylic acid + NADH + decarboxylase + ATP + NAD+ + ascorbic acid -> RCOOH + CO2

Front 55

Describe omega oxidation of fatty acids.

Back 55

CH3CH2CH2COOH + NADPH + monooxygenase + O2 -> HOOCCH2CH2COOH (dicarboxylic acid) + NADP+

Front 56

Describe peroxisomal degradation of long chain fatty acids.

Back 56

Analagous to beta oxidation to shorten fatty acid chain, produces H2O2 in atleast one step of pathway. After partial degradation in peroxisomes, release medium chain fatty acid and beta oxidation continues in mitochondria.

Front 57

What enzyme is used to conver delta 3-cis unsaturated fatty acids into delta 2-trans unsaturated fatty acids?

Back 57

delta 3-cis -> delta 2-trans enoyl Co-A isomerase

Front 58

What enzyme is used to convert a delta 4-cis unsaturated fatty acid into a delta 3-trans unsaturated fatty acid?

Back 58

enoyl co-A reductase

Front 59

Why does the degradation odd carbon number unsaturated fatty acids yield less energy than saturated fatty acids?

Back 59

the isomerase enzyme used to convert cis double bonds to trans double bonds in unsaturated fatty acids fulfill the same function as acyl-CoA dehydrogenase does in normal beta oxidation, but they don't produce an FADH2

Front 60

Does the degradation of even carbon number unsaturated fatty acids yield the same or less energy than saturated fatty acid of the same number of carbons? Why?

Back 60

less ATP. though acyl-CoA dehydrogenase is used creating an alpha carbon double bond and producing FADH2 as in normal beta oxidation, an enoyl-CoA reductase is required to shift that the two double bonds to one beta carbon trans double bond. this process consumes an NADPH thereby reducing the amount of ATP derived from the reaction.