fatty acids

Question 1

fatty acids

Answer 1

• energy storage and production
• structural components of membranes
• some hormones are derived from fatty acids

Question 2

lipids

Answer 2

fatty acidsare conjugated with glycerol to form lipids -3 fatty acids linked to glycerol by an ester bond

Question 3

lipids are..

Answer 3

highly hydrophobic and not easily transporte

Question 4

TAG

Answer 4

triacylglycerol

Question 5

TAG as an energy source

Answer 5

not used until glucose supplies are low

-broken down in adipose tissue (fat tissue) is catalysed by triacylglycerol lipase

TAG + 3H2O –> glycerol and 3 fatty acids

-fatty acids are transported into the blood stream with albumin

Question 6

what catalysis the break down of TAG

Answer 6

triacylglycerol lipase

Question 7

what activates lipase

Answer 7

hormonally activated by glucagon

Question 8

saturated fatty acids

Answer 8

no double bonds

Question 9

unsaturated fatty acids

Answer 9

contains one or more double bonds (of cis configurations )

Question 10

fatty acids usually have an ….. number of C atoms

Answer 10

even

Question 11

what are fatty acids synthesised from

Answer 11

C2 precursor: acetyl CoA

Question 12

oxidation of fatty acids (3)

Answer 12

step 1: free fatty acids in the cytosol are activated formation fatty acylCoA step 2: fatty acyl-CoA uptake into mitochondria Step 3: beta-oxidation pathway in mitochondria

Question 13

only organ in the body than cannot use fat as an energy source

Answer 13

the brain

Question 14

step 1 of oxidation of fatty acids

Answer 14

-fatty acid activation- formation of any; CoA in cytoplasm -costs the equivalent of 2ATPs -AMP +ATP= 2 ADP

Question 15

step2 of oxidation of fatty acids

Answer 15

fatty acyl CoA uptake by mitochondria - in animals, fatty acids are oxidised in mitochondria -the inner mitochondrial membrane is not permeable to fatty acids ro fatty acyl CoA and instead the carnitine shuttle is used to transport fatty acyl CoA from the cytoplasm to the mitochondrial matrix

Question 16

carnitine shuttle

Answer 16

transports fatty acyl CoA from the cytoplasm to the mitochondrial matrix

Question 17

step 3 of oxidation of fatty acids

Answer 17

Beta oxidation of fatty acids in mitochondria - called B oxidation because the B carbon (C3) is oxidised 1.H removed from alpha and B carbons by acyl CoA dehydrogenase. Contains FAD cofactor. Electrons delivered to Coenzyme Q in ETC 2. Hydration of double bond- to produce hydroxyacly-CoA 3. C-OH oxidised to C=O. NADH formed is oxidised by ETC to produce ATP 4. CoASH attacks B carbon (red) to produced acetyl CoA and a fatty acyl CoA which is now 2 C atoms shorter Acetyl Co A oxidised by citric acid cycle

Question 18

in a even chained fatty acid (oxidation)..

Answer 18

all molecules are converted into acetyl CoA

Question 19

ATP yield from oxidation of palmitate

Answer 19

16 carbons long -cost of activation to palmitoyl-CoA= 2 ATP -7 rounds of b-oxidation -8 acetyl coA -8 x 10 ATP=80 ATP 7NADH -7x 2.5 ATP=17.5 ATP

Question 20

what can convert fatty acids to sugars and what cant

Answer 20

animals can convert fats to sugars and animals cannot

Question 21

plants and fungi can convert acetyl CoA into

Answer 21

sugars- because they have the glyoxylate acid cycle

Question 22

glyoxylate cycle

Answer 22

occurs in specilsiased organelles called glyoxysomes

Question 23

overall reaction in glyoxyate cycle

Answer 23

2Acetyl CoA–> malate–> oxaloacetate

Question 24

oxaloacetate can then be used to produce glucose vi

Answer 24

glucoseneogenesis

Question 25

odds chain fatty acids yield..

Answer 25

ATO and propionyl CoA

Question 26

although animal are incapable of producing glucose from acetyl CoA.. they can..

Answer 26

make glucose from propionyl CoA

Question 27

mammals can produce glucose from

Answer 27

odd chain fatty acids

Question 28

Fatty acid synthesis: first step

Answer 28

energy to form C-C bonds is supplied indirectly by synthesising malonyl CoA from acetyl CoA using AT and CO2 - reaction is catalysed by Acetyl CoA carboxylase (uses biotin as a cofactor)

Question 29

what cofactor does acetyl co A carboxylase use

Answer 29

biotin

Question 30

Step 1 of biosynthesis

Answer 30

an acetyl (2C) group is added using Malonyl CoA as the donor. Loss of CO2 drives the reaction Malonyl CoA s synthesised by the carboxylation of acetyl CoA Acetyl CoA + CO2 + ATP malonyl CoA +ADP + Pi

Question 31

Step 2 of biosynthesis

Answer 31

the C=O group on the C3 (B carbon) is reduced to C-OH by NADPH

Question 32

step 3 of biosynthesis

Answer 32

dehydration generates a duble and between the alpha and beta carbons (C2 and C3)

Question 33

step4 of biosynthesis

Answer 33

reduction of double bond to single bond

Question 34

step 5 biosynthesis

Answer 34

fatty acyle-ACP, now 2C longer, can re-enter the process or the process is stopped by removing ACP (using fatty acyl-ACP thioesterase)

Question 35

what removes ACP and stops fatty acid synthesis

Answer 35

fatty acyl-ACP thiesterase

Question 36

basics on fatty acid synthesis

Answer 36

same intermediates as B oxidation -occurs in cytosol different carrier (acyl carrier protein instead of acetyl CoA) -diff cofactors

Question 37

substrates of synthesis of fatty acids

Answer 37

acetyl CoA and NADPH

Question 38

citrate shuttle

Answer 38

used to transport acetyl CoA from the mitochondria to the cytoplasm

Question 39

sources of NADPH for fatty acid synthesis

Answer 39

pentose phosphate pathway and the citrate shuttle

Question 40

acetyl CoA carboxylase

Answer 40

is a biotin-dependent enzyme that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA

Question 41

acetyl CoA carboxylase is tightly regulated

Answer 41

inhibited by phosphorylation- AMP kinases is one of the major kinases--\> others are controlled by glucagon and adrenaline

Question 42

insulin signalling favours...

Answer 42

fatty acid synthesis by activating phosphatase that dephosphorylates acetyl CoA carboxylase.

Question 43

what is reciprocally regulated

Answer 43

fatty acid synthesis and breakdown

Question 44

glucagon promotes

Answer 44

release of fatty acids from ADIPOCYTES- high levels of fatty acyl CoA inhibits acetyl CoA carbboxylase

Question 45

malonylCoA made by acetyl CoA carboxylase inhibits..

Answer 45

carnitine acyle transferase I and prevents fatty acid oxidation by blocking entry into the mitochondrion

Question 46

summary of fatty acids

Answer 46

Summary ♣ Lipids have a range of functions- cell membrane, energy storage and cell signalling ♣ Fatty acid degradation (b-oxidation) occur in the mitochondria ♣ Animals cannot produce sugars from even chain length fatty acids (but can odd length) ♣ Fatty acid synthesis occurs in the cytoplasm ♣ Synthesis and degradation are tightly regulated.