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Science for Medicine > Lipids > Flashcards

Lipids Flashcards

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1
Q

What is a lipid?

A

It is an ester of a long hydrocarbon FA that is insoluble in water and is found in all living cells and tissues

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2
Q

What are the functions of lipid?

A

Energy storage, signalling molecules, enzyme cofactors, structural component of cell membranes, synthesis of vitamins and hormones

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3
Q

What are FAs?

A

They are hydrocarbon chains with a carboxylic group at one end, they can be saturated or unsaturated and their nutritional value can vary

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4
Q

What are the 4 types of fats?

A

Essential, good, bad and really bad

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5
Q

What are essential fats?

A

Fats that must be obtained from the diet as we can not produce C=C structures beyond C9 e.g. Linoleic acid

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6
Q

What are good fats?

A

Polyunsaturated e.g. plant oils

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7
Q

What are bad fats?

A

Unsaturated e.g. steric acid

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8
Q

What are really bad fats?

A

Trans fats e.g. margarine

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9
Q

What do gluconeogenic substances not contain?

A

FAs

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10
Q

What does the FA nomenclature of 12:1 and 16:2(2,8) mean?

A

12: 1- 12xC’s and 1xC=C
16: 2(2,8)- 16xC’s and 2xC=C (at C2 and C8)

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11
Q

What are the 3 major classes of lipids?

A

FA, triacylglycercide (TAG) and phospholipid

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12
Q

What are TAGs?

A

Main dietary lipid consisting of esters of FAs and glycerol

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13
Q

What are the properties of TAG?

A

It is anhydrous, highly reduced, combine in to water droplets and are major components of adipose tissue

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14
Q

What are the functions of TAG?

A

Energy storage (best), insulators, and forms depot fat in adipose tissue

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15
Q

What do phospholipids consist of?

A

Glycerol, 2xFA and a phosphate group

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16
Q

What are the properties of phospholipids?

A

Anhydrous

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17
Q

What are the functions of phospholipid?

A

Basic structure of cell membranes

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18
Q

What diseases are lipids involved in?

A

Atherosclerosis and steatorrhea

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19
Q

What is atherosclerosis?

A

Increases blood pressure due to an imbalance in lipid metabolism

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20
Q

What is steatorrhea?

A

Lipid malabsorption which leads to excess fat in pool and causes stool to float due to excess fluid. It has an oily appearance and foul smell

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21
Q

What causes steatorrhea?

A

Problems in bile secretion, pancreatic function and intestinal cell uptake

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22
Q

Where does digestion take place?

A

In the mouth and small intestine (mainly)

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23
Q

What is involved in digestion?

A

All lipids (mainly TAG), pancreatic enzymes, bile salts which cause emulsification and peristalsis

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24
Q

How are TAGs digested?

A

By pancreatic lipase which forms monoacylglycerol and 2xFAs

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25
How are cholesterol esters digested?
Broken down to cholesterol and 1xFA
26
How are phospholipids digested?
Hydrolysed to lysphophospholiid and 1xFA
27
When are FAs releases from fat stores?
When energy supply is low
28
How are lipids absorbed?
The products of digestion form mixed micelles with bile salts and their contents are released when a brush border membrane is crossed
29
Do all FAs need micelles?
No, only long chain FAs
30
What are bile salts?
Derivatives of cholesterol that are biological detergents that form emulsions with mixed micelles and prevent lipids from combining in an aqueous environment
31
What is the brush border membrane?
Enterocytes that release the products of lipid into cells via diffusion
32
How are lipids transported?
Chylomicrons, lipoprotein and albumin
33
What is the function of chylomicrons?
They store TAG, FAs and cholesterol esters which are then releases by exocytosis into the blood via the lymphatic system
34
What happens to TAG after it has been transported?
It is hydrolysed to FAs and glycerol by lipoprotein lipase when it reaches tissues
35
What happens to FAs after they are transported?
They are used a energy or er-esterfired into TAG for storage
36
What is the most dense out of chylomicrons, HDL and LDL?
Most- HDL | Least- Chylomicrons
37
What are lipoproteins?
They have hydrophilic surfaces and hydrophobic cores and are transport free FAs
38
Why are lipoproteins in a complex with serum albumin?
As serum albumin is the most abundant plasma protein with many binding sites
39
How is cholesterol transported?
LDL- liver -> tissue | HDL- tissue -> liver
40
What is VLDL?
Very low density lipoprotein
41
What is albumin?
A protein which is used to transport unesterified carboxylic acids by binding to them
42
How is excess carbohydrate and C from protein stored?
As FA residues and TAG in adipose tissue due to metabolism through acetyl CoA
43
Where are FAs synthesised?
Liver, lactating memory gland, adipose tissue and kidney
44
How are FAs synthesised from TAG?
They are released by hormone sensitive lipase (HSL) which is activated by adrenaline and inhibited by high plasma glucose and insulin
45
Where does FA synthesis take place?
In the cytosol from acetyl CoA which uses ATP and NADPH
46
What is acetyl CoA?
It is transported to cytosol by citrate shuttles. It is formed in mitochondria
47
Why are citrate shuttles used to transport acetyl CoA?
It can't cross the mitochondrial membrane, only the acetyl bit can
48
When do citrate shuttles occur?
When mitochondrial [citrate] is high
49
What are the products of FA synthesis?
Palmitic acid- C16
50
What is elongation and desaturation?
The further modification of palmitate (ester of palmitic acid) in the mitochondria by digestive enzymes
51
What is the function of Acetyl carrier protein (ACP)?
It links intermediates
52
What is the catalyst involved in FA synthesis?
A multi enzyme complex
53
What is the fate of FAs?
Acetyl CoA -> FA (in liver) -> TAG -> VLDL -> adipose tissue
54
What is an example of an essential FA?
Omega 3, which is derived from linoleic acid and lowers cholesterol
55
What are the effects of deficiencies in essential amino acids?
Growth retardation, reproductive failure and chronic intestinal disease
56
What is B-oxidation?
The metabolism of FAs, by degrading 2xC at a time in the mitochondria matrix
57
What are the products of B-oxidation?
1xacetyl CoA, 1xNADH, 1xFADH2
58
What are the 3 stages involved in B-oxidation?
Activation, transport and degradation
59
What is the process of activation in B-oxidation?
FAs are activated in the cytoplasm and forms acyl CoA
60
What is acyl CoA?
A temporary compound formed when acetyl CoA binds to a long-chain FA
61
What is involved in the transport phase of B-oxidation?
Carnitine shuttles
62
What is the process of transport in B-oxidation?
Long chain FAs are transported from cytoplasm -> inside the mitochondrion, catalysed by carnitine fatty-acyl transferase
63
What type of amino acid is carnitine?
Non-essential
64
What is the function of molnyl CoA?
It inhibits carnitine fatty-acyl transferase in FA synthesis
65
Can FA synthesis and degradation occur at the same time?
Nope
66
What is the process of degradation in B-oxidation?
FA acyl CoA is dehydrogenated to form FADH2 and another intermediate, which is then hydrated and dehydrated to form NADH. Thylosis then occurs
67
What is thylosis?
Forms acetyl CoA form dehydrogenated NADH
68
What are steroid hormones?
They are chemical substances that serve as chemical messengers. Steroids are major lipid class
69
What is the function of cholesterol?
It is the main starting material for steroid hormone synthesis, and is a component of cell membranes
70
Where does cholesterol synthesis occur?
Liver
71
What is the structure of cholesterol?
27xC and 4x benzene rings
72
What are ketone bodies?
Water soluble compounds produced from excess acetyl CoA that are transported through the blood to peripheral tissues
73
What are the functions of ketone bodies?
They can be re-converted into acetyl CoA or enter the CAC
74
What is ketosis?
Metabolic process that burns stored fats when there is not enough glucose, due to starvation as TAGs aren't being mobilised. The [ketone body] increases
75
What is ketogenesis?
The production of ketone bodies which occurs in the liver and also produces acetone
76
Why must acetone be expelled by respiration?
It is too unstable
77
What are the 2 main types of ketone bodies?
Actetoacetate and 3-hydroxylbutarate

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