Lipids Flashcards
(106 cards)
1
Q
Types of lipid?
A
Phospholipid, glycolipid, triacylgylcerols, and steroids
2
Q
Functions of lipids
A
Form barriers (internal & external), stored energy source, and involved in signal transduction pathways
3
Q
Why can’t our bodies synthesize cis-polyunsaturated fatty acids and therefore we need to eat them especially omega-3 and omega-6.
A
Our bodies lack the enzyme to add C-C double bonds past carbon 9
4
Q
Why arent lipids considered polymers
A
Smaller than average Eukaryotic protein, not many monomers, and monomers are not interlinked
5
Q
What is the general structure of TAG
A
3 fatty acids & glycerol backbone
6
Q
True or false, number of adipocyte cells increase as you age.
A
False, number is established during childhood
7
Q
How does weight loss/gain work in regards to adipocytes
A
Adipocytes increase in triacylglycerol content
8
Q
Where is TAG stored
A
In adipocytes within adipose tissue
9
Q
What is the general structure of a phospholipid
A
Phosphate, alcohol, and fatty acids
10
Q
What are the two types of phospholipids and their platforms
A
Phosphoglyceride and sphingolipid; platforms are glycerol and sphingosine, respectively
11
Q
How many fatty acids does phosphoglyceride contain
A
2
12
Q
How many FAs does sphingolipid contain
A
1
13
Q
What are glycolipids
A
Its a membrane lipid with a carbohydrate monomer covalently attached
14
Q
Are glycolipids neutral or negatively charged
A
DEPENDS whether or not sulfate group is present!
15
Q
What is the function of a glycolipid
A
Membrane stability and cell to cell interaction
16
Q
What are the two types of glycolipids
A
Glycosphingolipids and glycoglycerolipids
17
Q
Integral membrane component in ANIMAL CELLS and important in embryo development
A
Glycospingolipids
18
Q
Integral membrane component in PLANT cells; important for photosynthesis
A
Glycoglycerolipids
19
Q
What are the functions of steroids
A
Signaling, digestion of dietary lipids, and membranes
20
Q
What lipid has a non-linear, tetracyclic platform
A
Steroids
21
Q
What is the most abundant steroid
A
Cholesterol
22
Q
True or false, steroids typically have fatty acids
A
False, they generally lack
23
Q
How much of a eukaryotic cell’s membrane does cholesterol take up
A
30-40%
24
Q
Why are steroids considered lipids
A
Same solubility characteristics (hydrophobic & water-insoluble), found naturally alongside other lipids within fat, and synthesize from the same substance as other lipids (Acety coA)
25
How much water do cells have and where is most found.
70% and found within the cytoplasm
26
Why is water a polar molecule
Electrons spend more time near oxygen than near hydrogens and gives O the partial negative and H a partial positive
27
Explain the hydrophobic effect
Phenomenon where non polar molecules aggregate to avoid contact with polar molecules
28
Is less surface area between oil and water high or low entropy
High entropy
29
What are nonpolar phospholipid tails of a membrane stabilized by
Van der waals with adjacent hydrocarbon chains
30
What are polar phospholipid heads of a membrane stabilized by
Hydrogen bonds by surrounding water
31
How does viscosity affect a membrane
More viscous = too rigid and less vicious can cause a leaky membrane
32
Common attributes membrane share
Amphipathic phospholipids, asymmetric (hydrophobic vs hydrophobic regions) non-covalent assemblies, electrically polarized and fluid structures, have specific proteins
33
Explain membrane polarity
Phospholipid heads are naturally negatively charged due to phosphate group but tend to be neutral on extracellular side due to interactions with positively charged ions and negatively charged on the intracellular side due to lack of interaction with positively charged ions.
34
How do prokaryotes regulate membrane fluidity
by fatty acid chain length and unsaturation. Shorter chain length and cis unsaturation = less rigidity
35
How do Eukaryotes regulate membrane fluidity
Through cholesterol, more cholesterol = more rigidity due to less non covalent interactions
36
What type of diffusion is common, transverse or lateral
Lateral
37
What can be transported by simple diffusion
Small uncharged molecules such as CO2; but must move along concentration gradient and be lipophilic
38
What type of transportation requires transporters (e.g protein pumps/channels)
The transportation of large uncharged molecules, ions and polar molecules, and anything moving against a gradient
39
What types of transport display substrate specificity (transport some things but not others)
Facilitated diffusion and active diffusion
40
What are the major classes of membrane receptors
Seven-transmembrane-helix (7TM) receptors (AKA G protein coupled receptors)
Dimeric protein receptors that recruit protein kinases
Dimeric protein receptors that are protein kinases
41
Names of ligand lipids (PMs)
FAHFAs and steroid hormones
42
Examples of mediator lipids (SMs)
PIP3, ceramide, and diaglycerol
43
What are the four steps to B-oxidation pathway
1. Oxidation by FAD
2. Hydration
3. Oxidation by NAD+
4. Thiolysis by coenzyme A
44
What does the B-oxidation pathway do
Each round shortens each FA hydrocarbon chain by 2 carbons
45
What do the products of B-oxidation enter
Cellular respiration
46
Where does the B-oxidation pathway occur
The mitochondria of skeletal muscle cells
47
What occurs in the first step of metabolism
The beta carbon is oxidized by acyl CoA dehydrogenase
48
What does Oxidation by FAD in metabolism generate
Trans double bond between carbon-2 and carbon-3
49
What are the products of step 1 in metabolism
Trans-Δ2-enoyl CoA and FADH2
50
What occurs in the second step of metabolism
Hydration of Trans-Δ2-enoyl CoA by enoyl CoA hydratase
51
What does step 2 of metabolism generate
Hydroxyl group and single bond between carbon-2 and Carbon-3
52
What is the product of step 2 metabolism
L-3- hydroxyacyl CoA
53
What occurs in step 3 of metabolism
Oxidation of L-3-hydroxyacyl CoA by L-3-hydroxyacyl CoA dehydrogenase
54
What is generated in step 3 of metabolism
Hydroxyl group converts into keto group at Carbon-3
55
What are the products of oxidation by NAD+ in metabolism
3-ketoacyl CoA and NADH
56
What occurs in step 4 of metabolism
The cleavage of 3-ketoacyl CoA by thiol group of a second coenzyme A molecule
57
What is generated in thiolysis by coenzyme A
Two molecules from the cleavage of 3-ketoacyl CoA
58
What are the products of step 4 of metabolism
Acetyl CoA and a fatty acid chain two carbons shorter
59
What happens after Thiolysis
Shortened FA undergoes another round of beta oxidation
Acetyl CoA enters cellular respiration via citric acid cycle
NADH and FADH2 enter cellular respiration via electron-transport chain
60
What are the FINAL Thiolysis products for even chained fatty acids
Two acetyl CoA
61
What are the final Thiolysis products for odd chained FA
Acetyl CoA and propionyl CoA
62
What happens to the propionyl CoA made in Thiolysis
Converted into succinyl CoA which then enters cellular respiration
63
How are FAs longer than 22 carbons metabolized
They’re first sent to peroxisome where the acyl group is shortened via peroxisomal beta oxidation and then transported to mitochondria for standard beta oxidation
64
What do additional enzymes do for unsaturated FAs in metabolism
shifts the position and configuration of C-C double bond (s)
65
Can skeletal muscles perform FA synthesis
No, they don’t have the necessary enzymes
66
Where does synthesis for fatty acids occur
In the cytoplasm of adipocytes and liver cells
67
What is the committed step in FA synthesis
Acetyl CoA getting condensed with bicarbonate generating malonyl CoA
68
What enzyme catalyzes the committed step in fatty acid synthesis
Acetyl CoA carboxylase I (ACC)
69
What are the steps to fatty acid synthesis
1. Condensation
2. Reduction of carbonyl group
3. Dehydration
4. Reduction of double bond
70
True or false, the FA synthesis pathway extends the hydrocarbon chain 2 carbons at a time and generates a saturated even chain FA
True
71
By what enzyme is the transfer of the acyl group to an ACP catalyzed by in FA synthesis
Malonyl-CoA:ACP Transacylase
72
Which substance is FA synthesis built upon
Hint: formed with ACP serving as a scaffold
Malonyl ACP
73
What is the first step of FA synthesis and which enzyme is involved
condensation of malonyl ACP with acetyl ACP; β-ketoacyl synthase
74
What does the first step of fatty acid synthesis do
extends acyl group by two carbons
75
What are the products of the first step of FA synthesis
acetoacetyl ACP and CO2
76
What is the second step Of fatty acid synthesis
reduction of carbonyl group by
3-ketoacyl-ACP reductase
77
What occurs during the second step of fatty acid synthesis
Reaction converts keto group to hydroxyl group at carbon-3
78
What is the product of the second step Of fatty acid synthesis
D-3-hydroxybutyryl ACP
79
What is the third step of FA synthesis
dehydration of D-3-hydroxybutyryl ACP by β-hydroxyacyl ACP dehydratase
80
What does the third reaction of FA synthesis generate
Generates trans double bond between carbon-2 and -3
81
What is the product of step 3 of FA synthesis
crotonyl ACP and H2O
82
What is step 4 of FA synthesis
reduction of the C=C bond by Enoyl ACP reductase
83
What is the electron donor in the fourth step of FA synthesis
NADPH
84
What does the fourth step of FA synthesis generate
single bond between carbon-2 and -3
85
What is the product of step 4 in FA synthesis
butyryl ACP
86
What happens after step 4 of lipid synthesis
1)lengthened acyl group undergoes another another round
2) butyryl ACP condenses with a new molecule of malonyl ACP
3) Forms C6-β-ketoacyl ACP; acyl group now contains 6 carbons
4) Rest of stage 3 (i.e. reduction, dehydration and reduction) follows
Repeats until C16-acyl ACP formed, as substrate for enzyme palmitoyl- protein thioesterase
87
Where does synthesis of odd chain saturated FAs occur
The cytoplasm
88
What is generated from propionyl CoA in order to build odd chain saturated FA
3-oxovaleryl-ACP
89
In order to synthesis a saturated FA product with 16+ carbons, it involves which organelle?
The endoplasmic reticulum
90
How is FA synthesis regulated
By hormones, citrate, phosphorylation, and palmitoyl CoA
91
What enzyme is a key control point of FA synthesis regulation
Acetyl CoA carboxylase I (ACC)
92
Where is cholesterol synthesized and from what substance
The liver; acetyl CoA
93
What are the steps of De Novo cholesterol synthesis
1. Synthesis of isopentenyl pyrophosphate from acetyl CoA
2. Condensation of isopentenyl pyrophosphate to form squalene
3. Cyclization of squalene to form cholesterol
94
What are inputs of part 1 of cholesterol synthesis
Acetyl CoA, ATP, and NADPH
95
What enzyme catalyzes cholesterol synthesis in step 1
HMG CoA reductase
96
How can cholesterol synthesis decline
By statin mimicking the substrate of HMG CoA reductase and bounding to the active site
97
What are inputs in part 2 of cholesterol synthesis
NADPH and 6 isopentenyl pyrophosphate
98
What is generated in part 2 of cholesterol synthesis
Pyrophosphate (PPi) and squalene (30Cs)
99
What are the inputs in part 3 of cholesterol synthesis
NADPH and O2
100
What is part 3 of cholesterol synthesis
Steroid nucleus first formed by squalene epoxide and then the product is cyclized to lanosterol then to cholesterol
101
Which two lipoproteins transport cholesterol
LDL and HDL
102
Where does LDL transport cholesterol
From liver to the body
103
Where does HDL transport cholesterol
From body to liver
104
Which phosphatase terminates insulin for receptors cytoplasmic domains
Protein tyrosine phosphatases
105
Which phosphatase terminates insulin signaling for inositol mediator lipids, such as PIP3
Lipid phosphatases
106
Which phosphatase terminates insulin signaling for activated effectors such as Akt
Protein serine phosphatase
