Fatty acid oxidation

Question 1

how can we fast for up to 2 weeks at a time?

Answer 1

we can store dietary fuels and break them down into ATP

Question 2

fatty acids

Answer 2

long chains of carbon and hydrogen

Question 3

how do fatty acids generate ATP?

Answer 3

transfer of electrons in form of hydrogens to molecules can generate ATP

Question 4

where does fatty acid oxidation occur?

Answer 4

mitochondria of heart, liver, skeletal muscle cells

Question 5

where is fat stored?

Answer 5

in adipocytes as triglycerides

Question 6

triglyceride

Answer 6

3 fatty acids attached to glycerol

Question 7

what enzyme breaks down triglycerides?

Answer 7

Hormone sensitive lipase breaks triglycerides down into 3 fatty acids + glycerol

Question 8

starvation state

Answer 8

blood glucose decreases, pancreas secretes glucagon which increases activity of hormone sensitive lipase

Question 9

what hormone increases activity of hormone sensitive lipase?

Answer 9

increase in glucagon!

Question 10

once broken down by hormone sensitive lipase, what happens

Answer 10

fatty acids can leave fat cell and enter blood stream and bind to albumin

Question 11

albumin does what with fatty acids?

Answer 11

takes them to target cells, such as liver cells that can perform fatty acid oxidation
also makes them more soluble

Question 12

fatty acid oxidation getting into the cell

Answer 12

fatty acid dissociates from albumin and diffuses into cell

Question 13

carnitine shuttle step 1

Answer 13

enzyme: fatty acyl-CoA synthetase
fatty acid to fatty acyl-coa
requires 2 ATP + CoA
ATP to AMP and PPi

Question 14

mitochondrial matrix

Answer 14

core of mitochondria
contains enzymes for beta-oxidation
BUT fatty acyl-CoA can’t cross mitochondrial membrane while CoA is attached

Question 15

carnitine shuttle step 2

Answer 15

fatty acyl-CoA to fatty acyl-carnitine +CoA (now can cross mito membrane)
enzyme: carnitine acyltransferase 1 (CAT1) replaces CoA with carnitine

Question 16

carnitine shuttle step 3

Answer 16

once inside matrix, CAT2 puts CoA where carnitine is. regenerating fatty acyl-CoA and free carnitine

Question 17

carnitine shuttle purpose

Answer 17

carnitine can go back and forth through mitochondrial matrix to bring in more fatty acids

Question 18

where do we get carnitine from?

Answer 18

diet! mainly meat

Question 19

carnitine shuttle regulation

Answer 19

malonyl-CoA (from fatty acid synthesis) can inhibit CAT1 and slow down fatty acid oxidation

Question 20

alpha and beta carbons of fatty acid chain

Answer 20

2nd (alpha) and 3rd (beta) carbons of chain

Question 21

fatty acid oxidation step 1a

Answer 21

palmitoyl-CoA to enoyl-CoA
enzyme: acyl-CoA dehydrogenase removes 1 hydrogen from alpha and beta carbons
gives hydrogens to FAD to make FADH2

Question 22

fatty acid oxidation step 1b

Answer 22

enoyl-CoA to beta-hydroxyacyl-CoA

enoyl-CoA hydratase uses H2O to add OH to beta carbon

Question 23

fatty acid oxidation step 2

Answer 23

beta-hydroxyacyl-CoA to beta-ketoacyl-CoA
enzyme: beta-hydroxyacyl-CoA
NAD+ to NADH

Question 24

fatty acid oxidation step 3

Answer 24

beta-ketoacyl-CoA to acetyl-CoA

enzyme: beta-ketothiolase

Question 25

beta oxidation 1 cycle energy payoff

Answer 25

1 NADH, 1 FADH2, 1 acetyl-CoA

Question 26

where do NADH and FADH2 go?

Answer 26

ETC! bc they are electron rich they can make ATP 1 NADH = 3 ATP 1 FADH2 = 2 ATP

Question 27

where does the 1 acetyl-CoA go?

Answer 27

citric acid cycle to yield NADH and FADH2 which then enter ETC and yield 12 ATP per acetyl-CoA

Question 28

1 palmitoyl-CoA yields

Answer 28

7 NADH 7 FADH2 8 acetyl-CoA 131 ATP - 2 ATP = 129 ATP

Question 29

odd-chain fatty acids...what is different?

Answer 29

same process until we have 3 carbon molecule left (propionyl-CoA)

Question 30

what does propionyl-CoA get converted to

Answer 30

succinyl-CoA | a TCA cycle intermediate

Question 31

where does succinyl-CoA go (2 options)

Answer 31

1) enter TCA cycle and become oxaloacetate (extra oxaloacetate can be used in gluconeogenesis) 2) succinyl-CoA can be fully oxidized to CO2

Question 32

fatty acid oxidation summary (3 steps)

Answer 32

1) activation 2) carnitine shuttle 3) beta-oxidation

Question 33

what triggers release of fatty acids from TAGs?

Answer 33

adrenaline, glucagon, and ACTH can activate lipases that release fatty acids from TAGs

Question 34

what happens to glycerol when fatty acids are broken down?

Answer 34

glycerol goes back to liver and can be converted to DHAP for gluconeogenesis

Question 35

fatty acids from diet

Answer 35

dietary TAGs are degraded in duodenum with aid of lipases from the pancreas fatty acids enter intestinal cells and are re-packaged as chylomicrons for transport in blood

Question 36

beta oxidation rxn 1

Answer 36

1) form double bond by acyl-CoA dehydrogenase

Question 37

beta oxidation rxn 2

Answer 37

2) hydrate double bond by enoyl-CoA hydratase

Question 38

beta oxidation rxn 3

Answer 38

3) oxidation by hydroxyl-CoA dehydrogenase

Question 39

beta oxidation rxn 4

Answer 39

4) cleavage of beta-keto ester to release acetyl-CoA and acyl-CoA

Question 40

acyl-CoA dehydrogenase

Answer 40

tightly bound to FAD | electrons picked up by FAD are moved into ETC via UQH2

Question 41

oxidation of palmitate (16C) yields...

Answer 41

106 ATP costs 2 ATP to activate fatty acid yield is 100 ATP via ETC/ox phos and 8 ATP from TCA cycle

Question 42

how many ATP per NADH or FADH2

Answer 42

2. 5 ATP per NADH | 1. 5 ATP per FADH2

Question 43

fatty acid oxidation: anaerobic or aerobic?

Answer 43

aerobic: requires oxygen!

Question 44

when do we use more fatty acids as fuel

Answer 44

long duration = use more fats | higher intensity = more carbs as fuel

Question 45

ketone bodies

Answer 45

alternate source of fuel produced in liver mitochondria (ketosis or ketogenesis) can't be used by liver! transported in blood for use by other tissues

Question 46

ketone bodies unique facts

Answer 46

soluble form of fats can cross blood-brain barrier (can be used by brain when glucose is unavailable) EX: starvation/low carbs or Diabetes Mellitus

Question 47

ketoacidosis

Answer 47

caused by very high amounts of ketone bodies in blood acidify blood, put strain on kidney occurs during uncontrolled diabetes mellitus (without insulin, cells can't use glucose in body) fatty acids broken down and acetyl-CoA used to produce ketone bodies