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Genes, molecules and cells (2) > Fat metabolism > Flashcards

Fat metabolism Flashcards

1
Q

What type of molecules are lipids?

A

Hydrophobic organic molecules

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2
Q

What are 3 functions of a lipid?

A
  1. Bilayer
  2. Energy stores
  3. Intra cellular signalling
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3
Q

What are the 2 main types of lipids?

A

Fatty acids

Glycerols (mono, di, tri)

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4
Q

What is the structure of a fatty acid?

A

Carboxylic acid with long chain hydrocarbon side groups

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5
Q

What species contain fatty acids?

A

Higher plants and animals

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6
Q

Where can fatty acids found in the body and how is it transported?

A

Plasma - serum albumin

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7
Q

How can fatty acids be used by tissues?

A

They are oxidised (liver & muscle) for energy

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8
Q

Can the brain metabolise fatty acids?

A

No - albumin cannot pass blood membrane barrier

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9
Q

What is the structure of a glycerol?

A

H2OC - HOC - H2OC

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10
Q

How are the tails attached to the glycerol?

A

Esterification

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11
Q

What Carbon number do the double bonds appear?

A

Carbon 9

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12
Q

Where are glycerols found? (2)

A

Fats and oils of plants and animals

Energy reserves - most abundant fatty acid

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13
Q

Where are fatty acids stored?

A

Adipose tissue

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14
Q

How are fatty acids stimulated to be released?

A

Hormone-sensitive lipase (removes fatty acid from C1 or C3)

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15
Q

How does hormone sensitive lipase become active? (2)

A
  1. Phosphorylated by a 3’-5’ cyclic amp protein kinase

2. Glucagon/epinephrine binds to the cells

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16
Q

How is hormone-senstive lipase deactivated?

A

High insulin or glucose causes dephosphorylation and inactivates

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17
Q

Where does glycerol released go?

A

To the liver via the blood

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18
Q

How does the Beta carbon (2) chain get broken down, where does this occur and what are the products?

A

Oxidation
Mitochondrial matrix
Acetyl CoA, NADH, FADH2

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19
Q

What is the equation for long fatty acid chain breakdown?

A

Fatty acid + CoA + ATP Acyl-CoA + AMP + PPi

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20
Q

What is used to prime long chain fatty acid breakdown?

A

Thiokinases

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21
Q

What is the long chain fatty acid breakdown driven by?

A

Exergonic hydrolysis of pyrophosphate - highly exergonic

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22
Q

What is the carnitine shuttle? (3)

A

A rate-limiting process
Fatty acids transfers its acyl-CoA on to carnitine
Transfers acyl group from there cytosol to the mitochondrial matrix via the outer mitochondrial membrane and inner mitochondrial membrane

23
Q

What is the purpose of acylcarnitine?

A

Transported into the matrix to allow free carnitine to go the other way

24
Q

What enzyme is used to remove carnitine and reattach CoA?

A

Transferase 1

25
What enzyme is used to break up carnitine from CoA in the mitochondrial matrix?
Carnitine palmitoyltransferase 2
26
How can the carnitine shuttle be inhibited?
Malonyl CoA means palmitate cannot be transferred
27
How do we obtain carnitine? (2)
Diet | Synthesised from LYSINE and METHIONINE in the kidneys and liver
28
What can cause carnitine deficiencies? (4)
Liver disease Malnutrition Pregnancy/burns victims Haemodialysis
29
How do short/medium chained fatty acids enter the mitochondria?
They do not need the carnitine shuttle and can cross the membranes freely
30
What are the 4 sequences in the fatty acyl-CoA formation?
1. Formation of a trans - alpha,beta double bond 2. Hydration of the double bond 3. NAD+ dependent dehydrogenation of the beta - hydroxyacyl-CoA 4. Carbon alpha - Carbon Beta cleavage in thiolysis reaction with CoA to from acetyl-CoA and a new acyl-CoA
31
What happens in the 1st sequence of fatty acyl-CoA formation and what does it produce? (3)
Formation of a trans alpha-beta double bond - via dehydrogenase by flavoenzyme acyl-CoA dehydrogenase - Produces FADH2
32
What happens in the 2nd sequence of fatty acyl-CoA formation and what does it produce? (3)
Hydration of the double bond - Enoyl-CoA hydratase - forms 3-L-hydroxyacyl-CoA
33
What happens in the 3rd sequence of fatty acyl-CoA formation and what does it produce? (3)
NAD+ dependent dehydrogenation of the beta-hydroyacyl-CoA - by 3-L-hydroxyacyl-CoA dehydrogenase - forms beta-ketoacyl-CoA, forms NADH
34
What is the effect if acetyl-CoA on pyruvate carboxylase?
A positive allosteric effector
35
What does each round of Beta-oxidation produce? (3)
NADH FADH2 Acetyl CoA
36
How much ATP is used in beta-oxidation?
129 ATP
37
Where are ketone bodies formed?
Liver
38
What are the 3 ketone bodies?
1. Acetoacetate 2. 3 - hydroxybutyrate 3. Acetone
39
What are ketone bodies important for?
Energy sources in heart and skeletal muscle | They do not need transport proteins
40
Where does lipid biosynthesis occur?
Cytosol
41
What is the first step of de novo fatty acid synthesis?
Transfer of acetate units from mitochondrial acetyl CoA to the cytosol
42
How is acetyl CoA produced?
Oxidative carboxylation of pyruvate by pyruvate dehydrogenase
43
What does the tricarboxylate transport system do? (3)
1. The CoA portion of acetyl CoA cannot cross the inner mito-membrane 2. OAA is reduced to malate by malate dehydrogenase 3. Male is oxidatively decarboxylated to pyruvate by malic enzyme, then returned
44
How does Acetyl-CoA form malonyl CoA
Carboxylation - biotin is the coenzyme
45
How is palmitic acid formed? (7)
1. Acetate is transferred from acetyl CoA to SH group of ACP 2. This 2-C unit is transferred to the thiol group of a cysteine residue 3. The ACP accepts a 3-C malonate unit it from lankly CoA 4. The acetyl group on the cysteine residue condenses with the malonyl group on ACP 5. The ketogenic group is reduced to an alcohol 6. Water is removed to introduce a double bond between C2 and C3 7. The double bond is reduced
46
How many times is the palmitic cycle repeated?
5
47
How is the palmitic cycle terminated?
Palmitoyl - S - ACP
48
How can palmitate be elongated?
SER or mitochondria
49
How are long chain fatty acids desaturated?
Desaturates - add cis - double bonds
50
What are fatty acids stored in?
Triacylglycerides - glycerol phosphate is the initial acceptor
51
What is the purpose of turning a fatty acid into a ketone?
Transport
52
What is the main biosynthesis step of lipids?
Condensation of C2 units
53
What do insulin and glucagon regulate?
Opposing pathways

Genes, molecules and cells (2) (14 decks)

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