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SES1002 > Lipid Metabolism > Flashcards

Lipid Metabolism Flashcards

(57 cards)

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1
Q

What are simple lipids

A

Fatty acids/ building blocks

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2
Q

What are compound lipids

A

Triacylglycerols/ energy stores (triglycerides and Phosphoacylglycerols – membranes (phospholipids)

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3
Q

What are derived lipids

A

Steroids – e.g., cholesterol

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4
Q

What are fatty acids composed of

A

Composed of a hydrocarbon “tail” and a carboxyl group (-COOH) “head”.
They are carboxylic acids.

The carboxyl group head has two polar groups: C=O and O-H

Hydrocarbon tail is made up of hydrogen and carbon and is non-polar

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5
Q

How many carbons a can fatty acids vary in

A

1-30

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6
Q

How many C do SCFA have

A

<8 carbons

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7
Q

How many carbons do MCFA have

A

8-14 carbons

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8
Q

How many carbons so LCFA have

A

> 14

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9
Q

Where are short chain fatty acids typically found in

A

found in milk fat – produced from undigested CHO in the colon

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10
Q

Where are MCFA often found

A

Milk fat and coconut

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11
Q

Which type of FA is most common in our diet

A

LCFA are the most common in our diet – they are either saturated or unsaturated

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12
Q

Why are high saturated fat foods solid at room temperature

A

No C=C so molecule is straight and tightly packed

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13
Q

What is a monounsaturated fat

A

One C=C double bond

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14
Q

What is a polyunsaturated fat

A

More than one C=C

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15
Q

How are lipids stored in the body

A

Stored as triacylglycerides or triglycerides in adipose tissue and muscle

Can be un- or saturated fatty acids attached to the glycerol backbone

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16
Q

What are lipoproteins

A

Lipids surrounded by a protein (because lipids don’t like water; hydrophobic!)

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17
Q

What are the functions of lipoproteins

A

After digestion (or the breakdown of TAGs) they are used to transport lipids around the body to different tissues

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18
Q

What are examples of lipoproteins

A

Chylomicrons, VLDL, LDL, HDL

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19
Q

Why are lipids not metabolised immediately after a meal containing fat

A

Lipids aren’t metabolized until 1-2 h after a meal or even up to 6 h if the meal is particularly rich in CHO. This is because CHO releases insulin and insulin inhibits lipolysis.

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20
Q

What stores can lipids can be broken down from

A

Adipose tissue and skeletal muscle

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21
Q

What hormone activates lipolysis at rest

A

Glucagon

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22
Q

What is the main hormone that activates lipolysis during exercise

A

Adrenaline

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23
Q

What is lipolysis

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A

Lipolysis is the breakdown of a TAG into 1 glycerol and 3 free fatty acid molecules

24
Q

What three different enzymes break down the three different fatty acids

Study These Flashcards
A

Adipose triglyceride lipase (ATGL)
Hormone sensitive lipase (HSL)
Monoacylglycerol lipase (MGL)

25
Which enzyme breaks down the triacylglycerol to a diacylglycerol
Adipose triglyceride lipase (ATGL)
26
Which enzyme breaks down the diacylglycerol to a monoacylglycerol
Hormone sensitive lipase (HSL)
27
What enzyme breaks monoacylglycerol into fatty acid and glycerol
Monoacylglycerol lipase (MGL)
28
When does breakdown typically occur
In fasting conditions or upregulated during exercise
29
What hormones regulate lipolysis by stimulating the lipase enzymes to split the TAGS into glycerol and FFA
Glucagon and epinephrine ect.
30
Why is lipid metabolism important during endurance exercise
Lipid oxidation (aerobic), so fats used to produce ATP increases as endurance exercise does
31
Why with increased duration of exercise is their a higher utilisation of lipids and why is there a higher utilisation in trained athletes
Because the carbohydrates store is depleted (muscle and liver glycogen) And endurance trained people are better able to utilise oxygen for lipid oxidation
32
How are FA transported in the blood
FA are hydrophobic so have to be bound to albumin to travel in the blood
33
Which enzyme is primary regulator of lipolysis rate
Hormone sensitive lipase (HSL)
34
How is glycerol transported
Glycerol is hydrophilic so can go straight to the liver
35
How many FA molecules can albumin carry
10 FA molecules
36
What happens to FA after lipolysis
can either be remade into TAGS or taken to tissues for oxidation
37
How many transporter proteins are used to transport albumin to the cell cytosol
3
38
What are the three transporter proteins that transport albumin into the cell cytosol (transport FA across the membrane for beta oxidation)
Fatty acid binding protein, fatty acid transport protein and fatty acid translocase(CD36)
39
How can you increase the number of transport proteins
The number of transport proteins can be increased by aerobic exercise and/or a HF diet
40
What happens to FA once they have been transported into tissues
Once transported to tissues, FA can be used to generate energy via a process called beta-oxidation
41
What is beta oxidation
beta oxidation is a process whereby the carbon chains of the FA are removed, therefore shortening the molecule The aim of beta-oxidation is to derive acetyl CoA for use in the TCA cycle
42
Where does beta oxidation occur
in the mitochondrial matrix and requires oxygen
43
Why do we need to transport FA from the cytoplasm to the mitochondrial matrix
The enzymes needed to generate ATP from the mitochondria are located in the MM
44
What are FA activated into and why
FA will not be transported if it is not activated To activate, FA reacts with coenzyme A to form ACYL COA – NOT acetyl coA
45
What catalyses FA activation
fatty acyl CoA synthetase
46
What is needed for FA activation and what is produced
requires ATP. 2 ATP are required so AMP and two PPi are produced.
47
What happens to the activated FA
Carnitine forms a bond with the C group on the Acyl CoA molecule to form Acyl carnitine Acyl carnitine diffuses into inter membrane space via porins on the outer MM Protein transporter called acyl carnitine translocase transports acyl carnitine to the MM remove this carnitine from the the Acyl group Acyl coA however goes through the process of Beta oxidation
48
What enzyme catalyses the formation of Acyl carnitine
carnitine acyl transferase 1 (on outer MM)
49
What enzyme removes carnitine from the Acyl group
carnitive acyl transferase II
50
What happens to the carnitine after
The carnitine can then be transported back to the cytoplasm to repeat the process via the translocase enzyme
51
Summarise how FA are transported to the MM
carnitine has to shuttle acyl coa into the MM for beta oxidation.
52
How many carbon chains are removed from the FA on each cycle of beta oxidation
2 carbon chains (More C chains = more cycles until only acetyl CoA is left)
53
What does malonyl CoA and why is it relevant
Malonyl-CoA is an important regulator of CAT1 activity – the enzyme that joins acyl and carnitine together to acyl carnitine
54
What happens to the carnitine shuttle/beta oxidation when malonyl CoA is decreased
Malonyl CoA is decreased during exercise to allow beta-oxidation to occur – e.g., breakdown fats for ATP Carnitine acyl transferase I activity Increases FA uptake into the MM
55
What happens to the carnitine shuttle/beta oxidation when malonyl CoA is increased
Malonyl-CoA increases when there is abundant Acetyl CoA in the cytoplasm – inhibiting beta-oxidation
56
Why does increased carbohydrate availability/ acetyl CoA decrease beta oxidation
Acetyl CoA availability is dependent on carbohydrate availability in the cell ●E.g., after a carbohydrate-rich meal, or when glycogen loading for exercise ●So carbohydrate intake or oxidation inhibit beta-oxidation Exercise intensity increased so Carbohydrate oxidation the dominant fuel source FFA oxidation in both adipose
57
Are there any differences in the metabolism of saturated and unsaturated fatty acids?
saturated fatty acids are oxidized more quickly than unsaturated fatty acids

SES1002 (23 decks)

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