Lecture 9 - Fatty Acid Metabolism II

Question 1

what is fatty acid anabolism (i.e: biosynthesis)?

Answer 1

fatty acid anabolism is essentially the reverse of fatty acid catabolism (i.e: beta-oxidation)

Question 2

what sort of process is fatty acid anabolism?

Answer 2

fatty acid anabolism is a two step process: preparation of precursor malonyl-CoA & acyl-ACP followed by elongation of fatty acid by fatty acid synthase

Question 3

what are the starting materials for fatty acid anabolism?

Answer 3

the starting materials are:

(1) unit added is malonyl-CoA instead of acetyl-CoA (bB-oxidation)

(2) chain reaction starts from acyl-CoA and malonyl-CoA

Question 4

where does fatty acid catabolism take place?

Answer 4

fatty acid catabolism takes place in the mitochondria

Question 5

where does fatty acid anabolism take place?

Answer 5

fatty acid anabolism takes place in the cytoplasm

Question 6

what is the primary electron donor in fatty acid anabolism?

Answer 6

NADPH is the primary electron donor in fatty acid anabolism

Question 7

fatty biosynthesis - step one - carboxylation:

Answer 7

(1) fatty acid synthesis starts by carboxylation of acetyl-CoA to malonyl-CoA by acetylene-CoA carboxylase enzyme [this step requires 1 ATP for every malonyl-CoA synthesised

Question 8

substrates of fatty acid synthase are:

Answer 8

substrates of fatty acid synthase are: acetyl-CoA, malonyl-CoA and NADPH

Question 9

what is mamillian fatty acid synthase encoded by?

Answer 9

a singular gene

Question 10

structure of fatty acid synthase:

Answer 10

a single polypeptide chain with three domains and 7 catalytic sites makes a homodimer

Question 11

what is required for the fatty acid synthase reaction?

Answer 11

a significant amount of NADPH is required

Question 12

how many fatty acids are synthesised simultaneously?

Answer 12

2 fatty acids are synthesised simultaneously

Question 13

where does fatty acid biosynthesis take place?

Answer 13

fatty acid biosynthesis takes place in the cytosol

Question 14

the cytosolic pathway leads to:

Answer 14

the synthesis of saturated fatty acids, with the main product being the 16-carbon fatty acid palmitate

Question 15

elongation reactions are catalysed by enzymes located on:

Answer 15

the cytosolic face of the endoplasmic reticulum membrane - malonyl CoA acts as the donor

Question 16

what reactions also occur at the ER membrane? reduction

Answer 16

reactions also occur at the ER membrane to produce unsaturated fatty acids

Question 17

what odes fatty acid elongation require?

Answer 17

fatty acid elongation requires acid elongase

Question 18

where does fatty acid elongation occur?

Answer 18

fatty acid elongation occurs on the ER

Question 19

Very long chain FA produced in the _____ which increases rapidly during __________ producing the FA required for ____________production

Answer 19

(1) Brain

(2) myelination

(3) sphingolipid

Question 20

where in the body does fatty acid biosynthesis take place?

Answer 20

pathways are present in: the liver, brain and kidney cells

Question 21

what is fatty acid biosynthesis regulated and activated by?

Answer 21

fatty acid biosynthesis is regulated by hormones and are activated in mammary glands during and post pregnancy

Question 22

when is the fatty acid biosynthesis pathway likely to occur?

Answer 22

the pathway is used in conditions of excess energy in particular carbohydrate intake

Under a condition in which citrate accumulates more than the capacity of TCA cycle to process, citrate moves to the cytoplasm

Question 23

how does excess citrate from the TCA cycle allow for aided fatty acid biosynthesis?

Answer 23

•Citrate is digested down to acetyl-CoA and oxaloacetate.

•Oxaloacetate returns to mitochondria as pyruvate

•The conversion of oxaloacetate to malate then pyruvate provides the NADPH pool required for FA anabolism (biosynthesis)

Question 24

what is needed to produce the variety of fatty acids:

Answer 24

•Additional enzymes and reactions are needed to produce the variety of fatty acids

Question 25

Elongation reactions are catalysed by enzymes located on the:

Answer 25

cytosolic face of the endoplasmic reticulum membrane. Malonyl CoA acts as the donor

Question 26

the cytosolic pathway leads to:

Answer 26

the synthesis of SATURATED fatty acids, with the main product being the 16 carbon fatty acid, palmitate

Question 27

how are fatty acids transported?

Answer 27

fatty acids are transported in a form of neutral fats that are either monoacylglycerol (MAG), or diacylglycerol (DAG) or triacylglycerol (TAG)

Question 28

what about palmitate allows it allows it to be activated by ATP/AMP and to be acyl-CoA before attached to a glycerol:

Answer 28

the reactive carboxyl group of palmitate

Question 29

what about glycerol becomes activated when fatty acids are attached?

Answer 29

glycerol has 3 hydroxyl groups where activated fatty acids are attached

Question 30

what is glycerol synthesised from?

Answer 30

fatty acids are synthesised from DHAP and Glycerol-3-phosphate (G-3-P)

Question 31

G-3-P comes from:

Answer 31

dihydroxyacetone phosphate (DHAP) – glycolysis

Question 32

fatty acids are stored as neutral fats in the body in three forms:

Answer 32

•Monoacylglycerol (MAG)

•Diacylglycerol (DAG)

•Triacylglycerol (TAG)