Final: fatty acid synthesis

Question 1

different forms of lipids

Answer 1

cholesterol, glycerol, phospholipids, fatty acids

Question 2

simplest form of lipids

Answer 2

fatty acids

Question 3

short and medium chain fatty acids

Answer 3

come from diet

Question 4

long chain fatty acids

Answer 4

synthesized by liver and fat cells

Question 5

how are long chain fatty acids synthesized?

Answer 5

combining lots of 2 carbon molecules (acetyl-CoA) into palmitoyl-CoA (single chain 16 carbon molecule

Question 6

use of palmitoyl-CoA

Answer 6

use to synthesize even longer fatty acids

Question 7

to create palmitoyl-CoA where do atoms come from?

Answer 7

acetyl-CoA provides carbon atoms

NADPH provides hydrogen atoms

Question 8

where do we get acetyl-CoA for fatty acid synthesis

Answer 8

carbohydrate metabolism (mainly glucose)

Question 9

after a starchy meal…

Answer 9

increase in glucose, pancreas releases insulin, cells take in glucose

Question 10

inside cells…

Answer 10

glucose enters glycolysis, yields 2 pyruvate and ATP

Question 11

pyruvate goes to…

Answer 11

mitochondria after pyruvate dehydrogenase converts it to acetyl-CoA

Question 12

acetyl-CoA goes to…

Answer 12

CAC where it combines with oxaloacetate to form citrate

Question 13

citrate goes to…

Answer 13

ETC to form ATP

Question 14

more glucose =

Answer 14

more ATP

Question 15

when CAC enzymes are inhibited, what do we use acetyl-CoA for?

Answer 15

fatty acid synthesis

Question 16

where are enzymes for fatty acid synthesis found?

Answer 16

in the cytoplasm

Question 17

how does acetyl-CoA get from mitochondria to cytoplasm?

Answer 17

acetyl-CoA combines with oxaloacetate to form citrate (just like in CAC)
happens when ATP is high

Question 18

once in cytoplasm,

Answer 18

citrate lyase cleaves citrate into oxaloacetate and acetyl-CoA
citrate shuttle!

Question 19

citrate-malate shuttle…what does oxaloacetate do once in cytoplasm?

Answer 19

goes back to mitochondria to combine with the next acetyl-CoA
malic enzyme converts oxaloacetate to pyruvate (so it can cross to mito)
NADP+ to NADPH

Question 20

once back in mitochondria, pyruvate…

Answer 20

is converted back into oxaloacetate by pyruvate carboxylase

Question 21

what increases pyruvate carboxylase activity?

Answer 21

acetyl-CoA!

makes oxaloacetate more available

Question 22

what provides hydrogens for fatty acid synthesis?

Answer 22

some comes from NADPH produced by malic enzyme

the rest comes from metabolism of excess glucose in PPP

Question 23

fatty acid synthesis overview

Answer 23

acetyl-CoA to palmitoyl-CoA

Question 24

fatty acid synthesis rxn 1

Answer 24

acetyl-CoA to malonyl-CoA

enzyme: acetyl-CoA carboxylase

Question 25

acetyl-CoA carboxylase cofactors

Answer 25

ATP Biotin Carbon dioxide ABC!

Question 26

rate-limiting step

Answer 26

acetyl-CoA carboxylase

Question 27

2 types of regulation of acetyl-CoA carboxylase

Answer 27

hormonal and allosteric regulation

Question 28

hormonal regulation of acetyl-CoA carboxylase

Answer 28

insulin (removes) and glucagon (adds) a phosphate group to acetyl-CoA carboxylase

Question 29

fed state

Answer 29

insulin activates phosphatase 2 which removes phosphate group from acetyl-CoA carboxylase, increasing activity

Question 30

fasted state

Answer 30

glucagon activates AMP-dependent kinase, adds phosphate group to acetyl-CoA carboxylase, decreasing activity we want to use fatty acids for energy, not build them

Question 31

allosteric regulation

Answer 31

molecule increases or decreases activity of an enzyme by binding on a site different to where the substrate binds

Question 32

citrate and acetyl-CoA carboxylase

Answer 32

citrate allosterically increases activity of acetyl-CoA carboxylase

Question 33

fatty acids and acetyl-CoA carboxylase

Answer 33

fatty acids allosterically inhibit acetyl-CoA carboxylase

Question 34

1 cycle, what happens

Answer 34

1 acetyl-CoA to 1 malonyl-CoA | 2 NADPH needed

Question 35

to make a 16 carbon palmitoyl-CoA we need...

Answer 35

8 acetyl-CoA | 14 NADPH

Question 36

where are fatty acids stored

Answer 36

in adipocytes and liver cells as TAGs

Question 37

difference between fatty acid synthesis and beta-oxidation?

Answer 37

1) intermediates in fatty acid synthesis are covalently linked to sulfhydryl groups of ACP (acyl carrier proteins) 2) fatty acid synthesis occurs in cytosol 3) fatty acid synthase (FAS) is only protein in synthesis (it has many enzymatic activities) 4) synthesis uses NADP+/NADPH as co-enzyme for REDOX rxns

Question 38

what does it take to generate palmitate?

Answer 38

acetyl-CoA 7 malonyl-CoA (includes acetyl-CoA, CO2, ATP) 14 NADPH

Question 39

source of 2 carbon units during fatty acid synthesis?

Answer 39

malonyl-CoA

Question 40

how is malonyl-CoA produced?

Answer 40

by acetyl-CoA carboxylase

Question 41

acetyl-CoA carboxylase regulation

Answer 41

inhibited by palmitoyl-CoA and activated by citrate

Question 42

acetyl-CoA carboxylase regulation pt. 2

Answer 42

more active when not phosphorylated less active when phosphorylated

Question 43

what happens to free fatty acids?

Answer 43

they don't stay in cytosol! | they rapidly esterify and move in TAGs or membrane lipids