Lipids (β-oxidation, fatty acid synthesis, ketone bodies)

what do plants use to store energy

starch

what do humans use to store energy (one lipid storage and one carbohydrate storage)

triacylglycerols and glycogen

what are the two attributes of fats that make them more efficient and economical at energy storage?

they are reduced and anhydrous

three places where fatty acid synthesis takes place (LAK)

liver, adipose tissue and kidneys

three molecules which are required for fatty acid synthesis (AAN)

acetyl CoA, NADPH and ATP

which molecule is needed to activate fatty acids for synthesis or degradation?

coenzyme A

three steps of fatty acid mobilisation

1. lipolysis (in adipose tissue)

2. release from adipocytes

3. transport (by albumin)

during lipolysis in fatty acid mobilisation, glycerol released and then converted to what and where?

to glyceraldehyde 3 phosphate in the liver

which enzymes perform lipolysis of TAGs to FAs and glycerol

cAMP regulated lipases

which hormone inhibits lipolysis

insulin

which hormones promote lipolysis

glucagon, epinephrine, norepinephrine, adrenocorticotropic hormone

adrenocorticotropic hormone stimulates adrenal glands to release which hormone

cortisol

what is the enzyme which activates fatty acids by adding the coenzyme A to a FA?

acyl CoA synthetase or fatty acid thiokinase

fatty acids (in the form of acyl CoA) get transported through the mitochondrial membrane as which molecule

acyl carnitine

which enzyme catalyzes the conversion of carnitine + acyl coa —→ acyl carnitine + coa

carnitine palmitoyltransferase I (CPT I)

which enzyme catalyzes the conversion of acyl carnitine + coa → acyl coa + carnitine

carnitine palmitoyltransferase II (CPT II)

what is the name of the translocase protein which transports acyl carnitine through the mitochondrial membrane

carnitine transporter

what kind of ion is carnitine (has one positive and one negative charge)

zwitterion

four main steps in β-oxidation

1. oxidation by FAD

2. hydration

3. oxidation by NAD+

4. thiolysis (cleavage)

what is the sequence of the starting molecule, intermediates and end products of the four steps in β-oxidation

1. acyl coa

2. trans delta2 enoyl coa

3. L-3 hydroxyacyl coa

4. 3 ketoacyl coa

5. acyl coa + acetyl coa

the point of one oxidative cycle of β-oxidation is to produce an acyl coa which is shortened by…

two carbons

besides the main substrates at each step of β-oxidation what other reactants are there for each step

1. FAD

2. water

3. NAD+

4. CoA

what are the enzymes used at each of the four steps of β-oxidation

1. acyl coa dehydrogenase

2. enoyl coa hydratase

3. L-3 hydroxyacyl coa hydrolase

4. beta ketothiolase

β-oxidation of fatty acids results in … of carbon atoms two at a time (2 words)

systematic removal

what is the name of the enzyme complex which incorporates all enzymes needed for fatty acid synthesis

fatty acid synthase

what is the reducing agent in FA synthesis

NADPH

what are the oxidising agents in β-oxidation?

NAD+ and FAD

where do β-oxidation and fatty acid synthesis occur respectively?

mitochondrial matrix and cytoplasm

cleavage of citrate to acetyl CoA and oxaloacetate by ATP citrate lyase costs how much ATP?

1

oxaloacetate and acetyl CoA come together to form … which is then transported from the matrix to the cytoplasm

citrate

when citrate enters the cytoplasm it is converted back to oxaloacetate and acetyl CoA by which enzyme?

ATP citrate lyase

what is produced as a side product as oxaloacetate is converted back to pyruvate in the cytoplasm and is also used in FA synthesis?

NADPH

citrate is transported from the matrix to cytoplasm by which carrier?

mitochondrial citrate carrier

is the conversion of acetyl coa to malonyl coa reversible or irriversible?

irreversible

which enzyme catalyzes the conversion of acetyl coa to malonyl coa?

acetyl coa carboxylase

what molecule is required as a coenzyme for acetyl coa carboxylase?

carboxybiotin (vit b7)

is acetyl coa carboxylase active or inactive when carbohydrates and energy are plentiful?

active

what activates acetyl coa carboxylase?

insulin, citrate and dephosphorylation

what inhibits acetyl coa carboxylase?

glucagon, epinephrine, palmitoyl CoA, AMP/ATP ratio, phosphorylation, AMPK

is acetyl coa carboxylase active when its phosphorylated or dephosphorylated?

dephosphorylated

does acetyl coa carboxylase use ATP?

yes

does malonyl CoA promote or inhibit fatty acid catabolism?

inhibit

fatty acid synthase has which two components attached?

phosphopantetheine (vit b5) and acyl carrier protein (ACP)

which enzyme catalyzes the reaction acetyl CoA + acyl-carrier protein (ACP) —→ acetyl ACP + CoA

acetyl transacylase

which enzyme catalyzes the reaction malonyl CoA + acyl-carrier protein (ACP) → malonyl ACP + CoA

malonyl transacylase

malonyl-ACP acts as a donor of … to acetyl-KS (on FA synthase)

two carbon atoms

what molecule is released as malonyl-ACP donates two carbon atoms to acetyl-KS of FA synthase complex during condensation?

CO2

what are the four types of reactions that occur during fatty acid synthesis?

1. condensation

2. reduction

3. dehydration

4. reduction

what is the main product when malonyl ACP donates 2C to acetyl-KS?

activated acyl ACP (butyryl ACP)

after butyryl ACP is formed from acetyl and malonyl where on the FA synthase complex is it moved to?

the cysteine on KS

which molecule is needed to donate additional two carbon atoms to butyryl-KS?

malonyl CoA

where does malonyl CoA bind on the FA synthase complex before its about to donate 2C to butyryl-KS?

phosphopantetheine on ACP

what product do butyryl-KS and malonyl-ACP form after another FA synthesis cycle?

hexanoyl ACP

what molecule is used during the reduction reactions of FA synthesis?

NADPH

what molecule is released during the dehydration reaction of FA synthesis?

H2O

what molecule is released during the condensation step of FA synthesis?

CO2

what is the name of the enzyme domain on FA synthase which has the active-site cysteine which holds acyl chains in a thioester bond?

beta ketoacyl synthase

after the first step (condensation) of FA synthesis, where are the following intermediates bound?

ACP

the growing acyl chain during FA synthesis has to be moved from … to … for the next cycle to start

ACP to KS

name the intermediates of core pattern each of four steps of the elongation cycle of FA synthesis

1. beta ketoacyl acp

2. d-3-hydroxyacyl acp

3. trans delta 2 enoyl acp

4. acyl acp

what is the final 16C product of FA synthesis?

palmitate

total amount of cycles it takes to turn acetyl CoA into palmitate?

7

is palmitate saturated or unsaturated?

saturated

name all the enzymes in the FA synthesis cycle

1. beta ketoacyl synthase

2. beta ketoacyl acp reductase

3. d-3-hydroxyacyl acp dehydratase

4. enoyl acp reductase

which enzyme does malonyl CoA inhibit?

CPT I

during fasting, when carbohydrate levels are low and beta oxidation is high, what is acetyl CoA converted into?

ketone bodies

what are the three ketone bodies

acetoacetate, d-3-hydroxybutyrate and acetone

1st step of ketogenesis: acetyl CoA + acetyl CoA → … (enzyme)

acetoacetyl CoA + CoA (3 ketothiolase)

2nd step of ketogenesis: acetoacetyl CoA + acetyl CoA → … (enzyme)

3-hydroxy-3-methyl-glutaryl CoA + CoA (HMG synthase)

3rd step of ketogenesis: lysis of HMG CoA → … (enzyme)

acetoacetate + acetyl CoA (HMG lyase)

ketogenesis: acetoacetate → … (enzyme)

d-3-hydroxybutyrate (d-3-hb dehydrogenase)

is the decarboxylation of acetoacetate to acetone enzymatic or spontaneous?

spontaneous

where are ketone bodies produced?

matrix of hepatocyte mitochondria

what happens to ketone bodies when they enter mitochondria of heart, muscle or brain cells?

they are converted to acetyl CoA

ketone bodies can lower blood pH causing which condition?

acidosis

are ketone bodies water soluble?

yes

can ketone bodies cross the blood brain barrier?

yes

acetone is excreted how?

it is exhaled/urinated

formation of ketone bodies can have potentially fatal consequences for people with which chronic condition?

diabetes