37 Fatty Acid Oxidation and Ketone Bodies

Question 1

of the macronutrients, which one is the major source of energy for ATP synthesis?

Answer 1

fats and when they undergo fatty oxidation, they release 9 kcal/gram

Question 2

what is the major pathway for FA oxidation?

Answer 2

Beta oxidation in the mitochondrial matrix which generates acetyl CoA which can enter TCA and produce more ATP

Question 3

T/F, many tissues including muscles oxidize FA to CO2 and H2O?

Answer 3

T

Question 4

why are the FAs a source of little energy in the brain and nervous tissue?

Answer 4

they cannot be imported across the blood brain barrier, however, small chain FAs can get across the membrane

Question 5

do red blood cells contain mitochondria? if no, what is the effect?

Answer 5

no, so they cannot oxidize the FAs

Question 6

what can fatty acyl CoA be used for?

Answer 6

energy- beta oxidation ketogenesis

membrane lipids- phospholipids/sphingolipids

storage- triacylglycerols

Question 7

what are the major products of fat oxidation?

Answer 7

NADH, FADH2, acetyl CoA

Question 8

T/F, muscle uses Beta oxidation for ATP production?

Answer 8

T

Question 9

what does the muscle use fatty acids for?

Answer 9

beta oxidation for ATP production

Question 10

In the liver what molecule is produced by acetyl CoA via what process?what is this product converted too? where is this released

Answer 10

in the liver, acetyl CoA is produced by Beta oxidation which is converted into ketone bodies which are released into blood as a fuel source for other tissues

Question 11

are ketone bodies used for energy in the muscle and kidney?

Answer 11

yes

Question 12

if the concentration of ketone bodies are high like after a lengthy starvation period, can the brain and nervous tissue use these?

Answer 12

yes

Question 13

T/F, the liver can use ketone bodies since it has the enzymes to do so?

Answer 13

F, it does not have the enzyme to do so which is good because ketone bodies would be used up as they are made which would waste energy

Question 14

can red blood cells use ketone bodies?

Answer 14

no because they do not have mitocondria

Question 15

acetoacetate and beta-hydroxybutarate are examples of?

Answer 15

ketone bodies which are combinations of acetyl CoA molecules packaged together and are stable in the blood and so when cells take them up they extract the acetyl CoA and use it for their TCA cycle

Question 16

fatty acids are hydrophobic, T/F? what happens to chains that are longer than 4-C? how soluble are short chain fats?

Answer 16

true; usually bound to proteins and so they are carried in the blood by albumin and handled in the cells by fatty acid binding proteins

short chain fats are fairly soluble in water due to the polar nature of the carboxyl group and only a few extra CH2 groups

Question 17

people with fatty acid metabolism problems have issues with this enzyme?

Answer 17

carnitinepalmitoyltransferase I or (CPT I)

Question 18

T/F, liver acts under an insulin signal?

Answer 18

true

Question 19

what is the significance of malonyl CoA?

remember synthesize fats under insulin and oxidize fats under glucagon

Answer 19

this enzyme (negative allosteric inhibitor) is produced during fat synthesis and will shut down CPT1 which prevents newly synthesized fats from being imported into the mitochondria and immediately oxidized

malonyl CoA only present in appreciable amounts when fats are being synthesized like during insulin response

Question 20

so in a fatty acid, which carbon is the goal of oxidation?

Answer 20

the beta carbon, hence beta oxidation producing an acetyl CoA with fatty acyl CoA, so like for palmitoyl CoA, it gets oxidized 7 times and so you have 8 acetyl CoA producing a lot of energy

Question 21

fatty acids are oxidized into two carbon units making what?

Answer 21

acetyl CoA for TCA cycle

Question 22

in the steps for the oxidation of fatty acids what are the products?

Answer 22

FADH2, NADH, acetyl CoA

Question 23

generally, why is a long carbon fatty acid a good source of energy?

Answer 23

because for one palmitate for example, C16, you have 8 full cycles of the TCA cycle which yields 100 ATP compared to the 25 produced from glycolysis

Question 24

how is beta oxidation carried out for odd chain fatty acids?

Answer 24

the same as for the even and the final products are Propionyl CoA (3 carbon fatty acyl) and the acetyl CoA

Question 25

what happens to the propionyl CoA after beta oxidation of the odd chain fatty acid is complete?

Answer 25

propionyl Co A is carboxylated to methylmalonyl CoA, which is converted to succinyl CoA (a TCA cycle intermediate)

Question 26

what is a main mechanism by which FA oxidation is controlled?

Answer 26

NADH and FADH2

Question 27

ketone bodies can be used by what structures?

Answer 27

ketone bodies can be used by fast twitch skeletal muscle, cardiac muscle, brain

Question 28

where do the synthesis of ketone bodies occur?

Answer 28

liver mitochondria

Question 29

what happens to the ketone bodies that end up in tissue? by what tissue?

Answer 29

they are oxidized as fuel

• muscle and kidney, not liver because it lacks thiotransferase for oxidation
• brain during prolonged fasting/starvation and so when the ketone bodies get high enough they enter the brain and be utilized

Question 30

why can’t the liver oxidize fat?

Answer 30

it can’t because it doesn’t have the enzyme thiotransferase

Question 31

can acetoacetate enter the cells?

Answer 31

yes or produced in the cells via oxidation of Beta-hydroxybutyrate

note that reverse reaction of β-hydroxybutyrate formation, produces NADH which is used to generate ATP from oxidative phosphorylation and so more energy can be obtained

Question 32

cardiac muscles love ketone bodies T/F? slow twitch muscles?

Answer 32

T;T

Question 33

energy produced using ketone bodies derived from fatty acids is nearly the same as taking fatty acids all the way to CO2 and H2O. Advantages?

Answer 33

liver only partially oxidizes FAs to ketone bodies

Other tissues can use the ketone bodies as fuel

brain can use ketone bodies during starvation,
decreasing need for glucose

decreased use of muscle protein aas as carbon source for glucose production

Question 34

what are the key signals for fatty acid oxidation and ketone body utilization?

Answer 34

NADH and FADH2 levels and ATP levels

Question 35

why do muscles like cardiac muscles prefer fatty acids for fuel?

Answer 35

it provides the greatest amount of ATP with the least amount of work and so the heart uses fats as its primary source of energy and can also take signals from insulin and use glucose