Lipid Metabolism Flashcards
(136 cards)
1
Q
Lipids are not soluble in water, but they are soluble in…?
A
…non-polar organic solvents.
2
Q
What is this the general formula for?:
CH3(CH2)nCOOH.
A
Fatty acids.
3
Q
Fatty are a long ……………… chain with a terminal ………………. group.
A
Hydrocarbon, carboxyl (COOH).
4
Q
Name some places where lipids are found in the body and in what forms.
A
Adipose tissue - triacylglycerol.
Membranes - phospholipids.
Plasma - free fatty acids / non-esterified fatty acids (NEFA).
Plasma - glycolipids.
Plasma - cholesterol esters.
5
Q
Name some of the major biological roles of fatty acids.
A
Energy storage and production, protection, insulation, as components of biological membranes, as precursors to other biological molecules (e.g. eicosanoids, prostaglandins, prostacyclins, thromboxanes and leukotrienes).
6
Q
What are the two most abundant lipids?
A
Triacylglycerol (TAG) and phospholipids (PL).
7
Q
What is an ester?
A
Carbon double bonded to oxygen.
8
Q
What is the name for carbon double bonded to oxygen?
A
An ester.
9
Q
TAG molecules are formed from esters of haw many fatty acids, plus glycerol?
A
Three.
10
Q
Phospholipids are formed from esters of how many fatty acids, plus glycerol?
A
Two.
11
Q
Phospholipids are formed from two fatty acids, glycerol, and what else?
A
Phosphate and another alcohol (often including nitrogen).
12
Q
What are the four ways in which fatty acids can differ?
A
- Chain length.
- Number of double bonds.
- Position of the double bonds(s) in the chain.
- Type of double bond (cis or trans).
13
Q
In fatty acids, which is the most common type of double bond found in nature? Cis or trans?
A
A cis double bond, where the carbon atoms are on the same side.
14
Q
Where are fatty acids with trans double bonds found?
A
In hydrogenated fats, e.g. in rumen and margarines.
15
Q
What impact do cis/trans double bonds have on a membrane?
A
Membranes with fatty acids containing cis double bonds are more fluid and flexible. This is because the cis-bonded fatty acids cannot pack as closely together as trans-bonded fatty acids.
16
Q
Which appears straight and which appears bent? Cis-bonded or trans-bonded fatty acids?
A
Cis-bonded fatty acids appear bent and trans-bonded fatty acids appear straight.
17
Q
If a fatty acids has no double bonds, is it polyunsaturated, saturated or monounsaturated?
A
Saturated.
18
Q
If a fatty acid has one double bond, is it saturated, polyunsaturated or monounsaturated?
A
Monounsaturated.
19
Q
If a fatty acid has more than one double bond, is it monounsaturated, polyunsaturated or saturated?
A
Polyunsaturated.
20
Q
How are ALL polyunsaturated fatty acids made?
A
Desaturating monounsaturated fatty acids.
21
Q
Animals can only make polyunsaturated fatty acids based on which monounsaturated fatty acid?
A
Oleic acid.
22
Q
How do animals make polyunsaturated fatty acids from monounsaturated fatty acids?
A
By inserting a double bond between the existing bond and the carboxyl group.
23
Q
Animals cannot make which polyunsaturated fatty acids from oleic acid?
A
Linoleic acid and alpha-linolenic acid.
24
Q
How do plants make polyunsaturated fatty acids from monounsaturated fatty acids?
A
They insert a double bond between the existing bond and the methyl group.
25
Where do plants add a double bond when they desaturate a monounsaturated fatty acid to a polyunsaturated fatty acid?
Between the existing bond and the methyl group.
26
Where do animals add a double bond when they desaturate a monounsaturated fatty acid to a polyunsaturated fatty acid?
Between the exisiting bond and the carboxyl group.
27
What is the name for fatty acids that can be made by plants, but not by animals?
Essential fatty acids.
28
Essential fatty acids can be made by ................... , but not by .................. .
Plants, animals.
29
What two functions are essential fatty acids vital for in the body?
Membrane function and as precursors of eicanosoids.
30
What are eicanosoids?
Local hormones which alter activity of the cells that they are produced in and those adjoining them.
They regulate a range of functions including inflammation, blood flow, blood clotting and ion transport across membranes.
31
Name some of the functions of eicanosoids, local hormones which are made from essential fatty acids.
They regulate a range of functions including inflammation, blood flow, blood clotting and ion transport across membranes.
32
Animal fats tend to be solid at room temperature, whereas plant fats tend to be liquid. Why is this, in terms of the double bonds in the fatty acids?
Animal fats tend to be saturated, having few double bonds in order to pack together tightly and store fat as efficiently as possible.
Plant fats have more double bonds so they take up more space and are more liquid.
33
Why do animals synthesise fatty acids?
So that they have fat reserves that can be used for energy in bad times - when it is cold, or there is less food available, for example.
34
What does this show?:
Acetyl CoA - Malonyl CoA - Palmitic Acid - Stearic Acid - Oleic Acid.
The synthesis of fatty acids in animals.
35
Fill in the blanks:
C 2:0 - ?
? - Malonyl CoA
C 16:0 - Palmitic Acid
? - Stearic Acid
C 18:0 - ?
What does this represent?
Acetyl CoA
C 3:0
C 18:0
Oleic Acid.
Fatty acid synthesis in animals.
36
Do biologocally relevant fatty acids have ODD or EVEN numbers of carbons?
Even.
37
Where in the cell are fatty acids made?
In the cytosol.
38
What is the first step of fatty acid synthesis in animals?
Acetyl CoA (C 2:0) to Malonyl CoA (C 3:0).
39
What is the main difference between fatty acid synthesis in prokaryotes and eukaryotes?
In prokaryotes, fatty acids are synthesised by the action of a series of separate enzymes.
In eukaryotes, fatty acids are synthesised by the action of a multifunctional enzyme complex.
40
What does ACP stand for? What is its role in fatty acids synthesis?
Acyl Carrier Protein.
The intermediates in fatty acid synthesis are linked to ACP, which is different in eukaryotes and prokaryotes.
41
True or false? The Acyl Carrier Protein (ACP) is the same in prokaryotes and eukaryotes.
False.
In prokaryotes the ACP is a 77 amino acid protein joined to a phosphopantetheine group.
In eukaryotes it is part of the fatty acid synthase complex.
42
Complete these reactions:
Acetyl CoA + ACP =
Malonyl CoA + ACP =
What are these reactions called?
= Acetyl ACP + CoA
= Malonyl ACP + CoA.
The Acetyl and Malonyl Transacrylase reactions.
43
Which fatty acids are synthesised by the fatty acid synthase system?
Long chain saturated fatty acids.
44
In prokaryotes, the fatty acid synthase system for making long chain saturated fatty acids contains four separate enzymes. What are the substrates?
HINT: there are only three substrates!
Acetyl ACP, Malonyl ACP and NADPH.
45
What does the thioesterase enzyme do in fatty acid synthesis?
It releases the carbon chain (termination) when it reaches C 16:0 (palmitic acid).
Sometimes shorter chains are made, e.g. in the mammary glands.
46
Why does the non-polar nature of fatty acids mean that they are good for storing energy?
They do not need to be surrounded by water (unlike sugars), which increases efficiency of space water usage in the body.
47
What are the main steps of fatty acid synthesis?
HINT: there are only two!
1. Formation of malonyl CoA.
2. Synthesis of palmitate.
48
Complete the reaction for the formation of malonyl CoA, the first step in fatty acid synthesis:
7 Acetyl CoA + 7CO2 + 7ATP =
= 7 Malonyl CoA + 7ADP + 7Pi + 7H+.
49
Complete the reaction for the formation of palmitate from malonyl CoA, the second step in fatty acid synthesis:
Acetyl CoA + 7 Malonyl CoA + 14 NADPH + 7H+ =
= Palmitate + 7CO2 + 14NADP+ + 8CoA + 6H2O.
50
Complete the reaction for the overall synthesis of fatty acids (palmitate):
8 Acetyl CoA + 7ATP + 14NADPH =
= Palmitate + 14NADP+ + 8CoA + 6H2O + 7ADP + 7Pi.
51
Which is the main fatty acid synthesised in animals?
Palmitic acid / palmitate. C 16:0.
52
How many carbons does palmitic acid have? How many double bonds? Is it saturated or unsaturated?
It has 16 carbons, 0 double bonds and is saturated.
C 16:0.
53
60% of fatty acids in human adipose tissue have how many carbon atoms? What does this show?
60% of fatty acids in human adipose tissue have 18 carbon atoms.
As humans synthesise palmitic acid, these 18 carbon fatty acids must come from dietary sources or further metabolism of palmitic acid.
54
When palmitic acid has been formed, it is transported from the ................ to the .................... ..................... where two carbon atoms are added to form ................... ................... (C 18:0).
Cytoplasm, endoplasmic reticulum, stearic acid.
55
Name the enzyme that catalyses the reaction which adds two carbon atoms to turn palmitic acid into stearic acid.
Elongase.
56
What is added to stearic acid (C 18:0) to form oleic acid (C 18:1)? Which enzyme does this?
A double bond is added by Δ9-desaturase.
57
Phospholipids are categorised by their different .................... groups.
Alcohol.
58
Some biologically important phospholipids are phosphatidylcholine, phosphatidylethanolanine, phosphatidylserine and phosphatidylinotisol. What is their major role, and which function do they play a key role in?
Phospholipids are a major component of cell membranes and play a key role in cell signalling.
59
What is the product of the first step of TAG AND PL synthesis, which is the same in both cases?
Phosphatidate.
60
In the synthesis of TAG and PL, what are the two fates of phosphatidate?
Diacylglycerol and CDP-Diacylglycerol.
61
In TAG synthesis, ..................... becomes ................... then ................... as fatty acid groups are added.
Phosphatidate, diacylglycerol, triacylglycerol.
62
In phospholipid synthesis, phosphatidate can become ................ or .................. before it becomes a phospholipid.
Diacylglycerol or CDP-Diacylglycerol.
63
Which fate of phosphatidate eventually becomes the phospholipid phosphatidylinitosol?
CDP-Diacylglycerol.
64
How do adipose tissue, the liver, intestines and muscles all communicate to assess energy status?
Via the blood stream.
65
Which is these is an energy sink, which is an energy source and which is energy storage?:
Adipose tissue.
Liver.
Muscles.
Intestines.
Source - intestines.
Sink - muscles.
Short-term storage - liver.
Long-term storage - adipose tissue.
66
Which organ can 'pre-warn' adipose tissue that it needs to start to release energy as its own supplies are running low? Why does it do this?
The liver can warn adipose tissue that its own short-term energy storage is running low because it takes longer for energy stored in adipose tissue to be released.
67
Lipids are not soluble in water, instead there are two ways they are transported through the body. Name them.
Lipoproteins and non-esterified fatty acids.
68
Where in the body are lipoproteins used for lipid transport?
Lipids from dietary sources are transported from the intestines as lipoproteins and lipids made or stored in the liver are transported as lipoproteins.W
69
Which tissue releases non-esterified fatty acids into the bloodstream?
Adipose tissue.
70
What is another terms for non-esterified fatty acids?
Free fatty acids.
71
Name the four components of lipoproteins.
1. Proteins (apolipoproteins).
2. Phospholipids (phosphatidylcholine most abundant).
3. Triacylglycerol (TAG).
4. Cholesterol.
72
Cholesterol is found in two places in lipoproteins, where?
At the surface as free cholesterol.
As cholesterol ester in the core.
73
True or false? All cholesterol is bad.
False! We need some cholesterol for our bodies to function correctly.
74
The fats carried by a lipoprotein 'signal' to determine...?
...where the lipoprotein is going and what it's function is.
75
Lipoproteins differ in their ratio of protein/lipid, phospholipid/cholesterol ester/cholesterol/TAG ratio and specific proteins present, leading to physical differences in...?
...charge, density and size.
76
What are apolipoproteins?
A diverse group of proteins associated with lipoproteins, ranging widely in size.
Most transfer between lipoproteins, some stay with the lipoprotein particles.
77
What can the type of lipoproteins in someone's blood determine?
Whether they are at risk of cardiovascular disease.
78
What are the five main functions of apolipoproteins?
1. Structure - they hold lipoproteins together.
2. Enzyme activation / inhibition.
3. Receptor recognition - *very important*.
4. Energy metabolism activation / inhibition.
5. Membrane transport activation / inhibition.
79
What part of lipoproteins have these functions:
1. Structure - they hold lipoproteins together.
2. Enzyme activation / inhibition.
3. Receptor recognition - *very important*.
4. Energy metabolism activation / inhibition.
5. Membrane transport activation / inhibition.
Apolipoproteins.
80
Name the two pathways of lipoprotein metabolism.
Exogenous and endogenous.
81
Which lipoprotein metabolism pathway sees dietary lipids absorbed into enterocytes in the small intestine, where PL, cholesterol, cholesterol ester and TAG are incorporated into chylomicrons?
The exogenous pathway.
82
In exogenous lipoprotein metabolism, which apolipoprotein joins with PL, cholesterol, cholesterol ester and TAG to form chylomicrons?
Apo B48.
83
What is formed from apo B48, PL, cholesterol, cholesterol esters and TAG in exogenous lipoprotein metabolism?
Chylomicrons.
84
Over 90% of a chylomicron is TAG - what does this mean for it's size and density?
Chylomicrons are very large with a very low density.
85
Once formed, chylomicrons are secreted into the ............... and then into the bloodstream.
Lymph.
86
In capillaries of adipose tissue and muscle, chylomicrons become anchored to which enzyme?
Lipoprotein lipase (LPL).
87
Chylomicrons become anchored to lipoprotein lipase enzyme in the capillaries of which tissues?
Adipose tissue and muscle tissue.
88
Lipoprotein lipase hydrolyses ................ and releases ............. .............. which are taken up by the tissue.
TAG, fatty acids.
89
In lipoprotein metabolism, what does LPL hydrolyse and what is released, to be taken up by tissues?
LPL hydrolyses TAG to release fatty acids, which are taken up by tissues.
90
In exogenous lipoprotein metabolism, what happens when most of the TAG in a chylomicron has been hydrolysed?
It is released back into the circulation as a chylomicron remnant.
91
What are chylomicron remnants rich in?
Cholesterol.
92
How are chylomicron remnants removed from circulation?
It binds to receptors in the liver.
93
What is the endogenous pathway of lipoprotein metabolism?
The transport of lipids from the liver.
94
In the endogenous pathway of lipoprotein metabolism, PL, cholesterol, cholesterol ester, TAG combine with what to form a very low density lipoprotein (VLDL)?
Apolipoprotein (apo) B100.
95
Where is VLDL formed in endogenous lipoprotein metabolism?
In hepatocytes of the liver phospholipid.
96
Over 60% of a VLDL's mass is TAG, what does this mean for it's density?
It has a low density, but denser than a chylomicron.
97
VLDL are secreted directly into...?
...the bloodstream.
98
VLDL are very .......... in fat and .......... dense than water.
High, less.
99
In endogenous lipoprotein metabolism, when most of the TAG has been hydrolysed, what happens to the VLDL?
It is released as an intermediate density lipoprotein (IDL).
100
What happens to intermediate density lipoproteins (IDL) that are released in endogenous lipoprotein metabolism?
They are converted into low-density lipoproteins (LDL).
101
What are low-density lipoproteins rich in?
Cholesterol.
102
Do lipoproteins get more or less dense as you back towards the liver?
Less dense.
103
How is the LDL formed in endogenous lipoprotein metabolism removed from circulation?
By interaction with specific surface cell receptors.
104
80% of LDL is removed from the circulation by which organ?
The liver (the remaining 20% is removed by other tissues).
105
Which apolipoprotein is part of endogenous lipoprotein metabolism? Which is part of exogenous lipoprotein metabolism?
Endogenous - Apo B100.
Exogenous - Apo B45.
106
How can LDL lead to heart disease?
It can deposit cholesterol in the arteries, leading to artherosclerosis.
107
How can HDL prevent or reverse arthersclerosis?
By removing cholesterol from artery walls.
108
Fatty acids in adipose tissue are metabolised to...?
...TAG.
109
Fatty acids in the liver are metabolised to...?
...TAG, PL and acetyl CoA.
110
Fatty acids in muscle tissue are metabolised to...?
Acetyl CoA, ultimately CO2.
111
The brain cannot directly use fatty acids for energy, unlike some other tissues BUT after prolonged starvation, it can use .................... ....................., metabolised from fatty acids in the liver.
Ketone bodies.
112
Under which conditions are ketone bodies produced in the liver by fatty acid metabolism?
Starvation.
113
What are the three sources of fatty acids for energy?
1. Released by LPL from chylomicrons.
2. Released by LPL from VLDL.
3. Released as NEFA / FFA from adipose tissue.
114
What is this the overall equation for:?:
Palmitoyl - CoA + 7FAD + 7NAD+ + 7CoA + 7H2O = 8 Acetyl - CoA +7FADH2 + 7NADH2.
The metabolism of palmitic acid (C 16:0).
115
How much energy (in ATP) is released from the breakdown of palmitic acid? How does this compare to glucose?
106 ATP, far more than glucose!
116
Which fatty acid can be cis, cis Δ9, Δ12-octadecadienoate / C18:2 cis, cisΔ9, Δ12) when numbered from the carboxyl end?
This is linoleic acid, with 18 carbons and 2 cis double bonds, one between 9 and 10 and one between 12 and 13 when numbered from the COOH end.
117
Which fatty acid is C18:2, named from the n or omega end?
Linoleic acid, with 2 cis double bonds, one between the 6 and 7 carbons and one between the 9 and 10 carbons when numbered from the methyl / CH3 end.
118
Which fatty acid is C18:2?
Linoleic acid.
119
Which fatty acid is C18:3, and can be C18:3 cis, cis, cisΔ9Δ12Δ15 OR C18:3 n-3?
Alpha-linolenic acid.
120
Do fatty acids with more double bonds increase or decrease the risk of cardiovascular disease? Why?
Fatty acids with more double bonds (i.e. unsaturated) decrease the risk of cardiovascular disease because they are less tightly packed togther and therefore make membranes more fluid and flexible.
121
Acetyl CoA is made where?
Fatty acids are made where?
So the ................/................. shuttle transfers the two.
Acetyl CoA is made in the mitochondria.
Fatty acids are made in the cytosol.
So the pyruvate / malate shuttle transfers the two.
122
The fatty acid synthase reactions is a series of four reactions, which are?
1. Condensation.
2. Reduction.
3. Dehydration.
4. Reduction.
123
To get from malonyl CoA to palmitic acid in fatty acid synthase, the chain has to be ...?
...elongated.
124
What does albumin bind to in lipid transport?
Non-esterified (free) fatty acids.
125
What is the reverse cholesterol transport pathway?
Lipoproteins go back to the liver to be 'recharged' with lipids.
126
What is needed for fatty acid metabolism in adipose tissue? What is released?
Chylomicron / VLDL and glucose.
Fatty acids are released bound to albumin.
127
True or false? The liver can produce fatty acids from scratch.
True.
128
What is needed for fatty acid metabolism in the liver? What is released?
Chylo remnants and NEFA are used, VLDL is secreted.
129
In the liver, fatty acids undergo what process to form TAG and PL, which is secreted as VLDL?
Esterification.
130
What is happening in the liver in lipogenesis?
Synthesis of fatty acids from scratch.
131
What are cells in adipose tissue called?
Adipocytes.
132
What is required for fatty acid metabolism in muscles? What is released?
Fatty acids from chylomicrons / VLDL and NEFA are required, CO2 and ATP is released.
133
What does this equation represent?:
Fatty acid + ATP + CoA = Fatty acid CoA + AMP + PPi.
Fatty acid oxidation.
134
Which enzyme catalyses fatty acid oxidation?
Acyl CoA.
(NOT acetyl CoA!).
135
Where does Acyl CoA have to move to in order to catalyse fatty acid oxidation?
The mitochondria.
136
