Exam 2 Ch 20 Flashcards
1
Q
How many enzyme reactions in fatty acid biosyntheis
A
7
2
Q
cofactor required for decarboxylases
A
Thiamine Pyrophosphate (TTP)
3
Q
cofactor required for carboxylases
A
biotin
4
Q
What is the first committed and rate-determining step in fatty acid biosynth?
A
catalyzed by acetyl-CoA carboxylase. Acetyl-CoA + -O2C = malonyl-CoA.
5
Q
methods for Regulation of acetyl-CoA carboxylase
A
allosteric control, hormonal regulation, covalent modification
6
Q
What are the two isoforms of acetyll-CoA carboxylase?
A
ACC1: adipose tissue
ACC2: tissues that oxidize but do not synth fatty acid
7
Q
Structure of fatty acid synthase
A
ACP phosphopantetheine arm mimics pyruvate dehydrogenase lipoic acid arm
8
Q
Most important step
A
C-C bond forming
9
Q
Elongation reactions after formation of acetoacetyl-ACP
A
- Reduction by KR. Carbonyl to alcohol
- Dehydration by DH to eliminate water
- Reduction by ER, reduces alkene to alkane
10
Q
How many times does the elongation reactions happen
A
6 additional times
11
Q
How many carbons formed through elongation
A
4 + (6x2) = 16
12
Q
what is palmitate an example of?
A
What is the 16 carbons after elongation reaction called
13
Q
How is the elongation of fatty acid terminated
A
thioester hydrolysis
14
Q
What is the termination by thioester hydrolysis catalyzed by
A
palmitoyl thioesterase (TE)
15
Q
three steps of fatty acid whatever
A
Formation of CC bond
elongation
term
16
Q
Fatty acid exgtension occur where? hint:2
A
mitochondrial elongation and endoplasmic reticulum elongation
17
Q
how to unsaturate a fatty acid
A
oxidation
18
Q
WHat is oxidation of fatty acid catalyzed by
A
O2 dependent reactions. non-heme iron cofactors (cuz most are heme)
19
Q
Whare are the for isoforms
A
delta: 9,6,5,4,
20
Q
what pathway does the esterification of glycerol to fatty acids go through in the mitochondria
A
glycerol-3-phosphate pathway
21
Q
what pathway does the esterification of glycerol to fatty acids go through in the peroxisome
A
dihydroxyacetone pathway
22
Q
what pathway does the esterification of glycerol to fatty acids go through in the endoplasmic reticulum
A
Either of the two pathways
23
Q
How many acyltransferases required for a diacyl branch
A
- 3 for tiacyl branch
24
Q
define lipid?
A
organic biomolecule that are water-insoluble or amphipathic (both water loving and fearing)
25
List all 8 lipids
1. Fatty acids
2. glycerolipids
3. Glycerophospholipids
4. Sphingolipids
5. Sterol lipids
6. Prenol Lipids
7. Saccharolipids
8. Polyketides
26
fatty acid
chain elogated aliphatic molecules with a terminal carboxylic acidfatty acids
27
glycerol esterified fatty acids
glycerolipids
28
phosphate substituted glycerolipids
glycerophospholipids
29
N-acetylated fatty acids chain
Sphingolipids
30
Contain four-fused rings
Sterol lipids
31
Alkene alcohols
Prenol lipids
32
Fatty acids linked to sugars
Saccharolipids
33
Alternating ketones and methylene groups
polyketides
34
What are steroids
sterol lipids
35
what are fat?
glycerolipids
36
what are phospholipids?
glycerophopholipids
37
Saturated and even-chain
Stearic acid
38
unsaturated and even-chain and trans
elaidic acid
39
unsaturated, even chain, cis
oleic acid
40
what are triglycerides and triacylglycerols
glycerolipids
41
is a saturated glycerolipid liquid or solid
solid. Unsaturated are liquid
42
What is the difference between simple and mixed triglyceride and which are more common?
Simple contains the same three fatty acids and mixed contains different fatty acids. Mixed is common.
43
what is esterification
fatty acids bind w a glycerol molecule
44
what is the major storage of energy in humans the 90% of all dietary lipids
triglycerides (glycerol esterification 1,2, or 3)
45
WHat is the main component of bio membranes in eukaryoitic cells
glycerophospholipids
46
Are N-acetylated fatty acid chains (sphingolipids) universal in eukaryotic cells or prokaryotic cells
Eukaryotic cells. Rare in pro
47
What do Sphingolipids do in the body?
signalling molecules
48
list the simple sphingolipids:
Sphingosine and ceramides
49
List the complex Sphingolipids
sphingomyelins, Cerebrosides, and Gangliosides
50
what type of lipid has 4 fused rings
sterol lipids
51
what do sterol lipids do?
components of cell membranes and signaling molceules
52
5 types of serol lipids
sterols, steroids, secosteroids, bile acids, and steroid conjugates
53
Why are fats a more efficient stored form of energy?
because of their density.
Carbohydrates: 1 gram = 4 kcal
Proteins: 1 gram = 4 kcal
Fats: 1 gram = 9 kcal
54
What happens when you add water to a glycerol?
It goes from like triacylglycerol to fatty acid and a diacylglycerol.
55
what lipids are involved in digestion?
Triglycerides.
56
by what processes does digestion happen at lipid-water interfaces?
Churning and emulsifcation of bile acids
57
what form are triacylglycerols in for digestion
liposome(hole in the middle), micelle, bilayer
58
what is saponification?
conversion of an ester to an alcohol and carboxylate salt when reacted with a base.
59
what is a detergent like effect and what prevents it
saponification is, and fatty acid-binding proteins protect
60
what is a fatty acid-binding protein
Cytoplasmic protein that increases the
solubility of water-insoluble compounds
61
What is the most common lipid
triacylglycerols
62
which is more dense, glycogen or triacylglycerol?
triacylglycerol
63
Where does lipid digestion occur?
lipid-water interfaces
64
what is rate of digestion dependent on?
surface area
65
what helps with digestion so lipids are smaller?
emulsification by bile salts (amphipathic steroids)
66
what do lipases do to triglycerides?
hydrolyze them into fatty acid chains and glycerol
67
Examples of lipases?
pancreatic lipase and phospholipase
68
what facilitates absorbtion of lipid hydrolysis products?
bile salts and fatty acid-binding proteins
69
how are lipids transported between tissues?
lipoproteins
70
What is the fat to protein ratio of lipoproteins that are large
more fat, less protein, less dense
71
what is the least dense lipoprotein
chylomicrons
72
What is lipoproteins composedof?
triglyceride & cholesterol core, phospholipid shell, wrapped in apoliproprotein
73
what's the point of apolipoprotein?
1. It's the part that binds to a lipid.
2. Stabilizes complex and
3. provides functional identity of lipoprotein
74
What transports cholesterol and other lipids from tissues back to the liver?
HDL
75
What transports endogenous triglycerides & cholesterol from liver to tissue
VLDL, iDL, LDL
76
What transfers dietary intestinal triglycerides and cholesterol through the blood stream to the liver
chylomicrons
77
what is the point of receptor-mediated endocytosis?
General processs used to uptake large molecules via a unique receptors. MOlecules that are too big to be engulfed.
78
How do receptor mediated endocyutosis molecules interact with chylomicrons and VDL?
they are hydrolyzed
79
How do receptor mediated endocyutosis molecules interact with LDL?
bound and engulfed by cells
80
How do receptor mediated endocyutosis molecules interact with HDL
HDL transfers components to cell via the receptor
81
What is the odd-chain oxidation product of phenyl-labeled fatty acids?
benzoic acid
82
What is the even-chain oxidation product of phenyl-labeled fatty acids?
phenylacetic acid
83
where does oxidation of fatty acids occur?
B carbon from the carboxylic acid end
84
what is the priming of fatty acid oxidation catalyzed by?
acyl-CoA synthase
85
What are thokinases?
Acyl-CoA synthase (used to catalyze fatty acid oxi)
86
can acyl-CoA diffuse into mitochondria?
Noo
87
how are fatty acid transported into mitochondria
Transesterification reaction between carnitine &
acyl-CoA
88
what are the 4 reactions of oxidation of fatty acids in the mitochondria?
1. Dehydrogenation of acyl-CoA to trans-enoyl-CoA (Acyl-CoA dehydrogenase)
2. Hydration of 2-enoyl-CoA (enoyl-CoA hydratase)
3. Dehydrogenation of 3-L-HydroxyacylCoA (3-L-hydroxylacylCoA dehydrogenase)
4. Thiolysis of B-ketoacyl-CoA (B-ketoacyl-CoA thiolase)
89
list the type of catalist for all four oxi of fat reactions
dehydrogenase,
hydratase
dehydrogenase
thiolase
90
What does each round of fatty acid oxidation produce?
1 NADH (2.5 ATP), 1 FADH2 (1.5 ATP), 1 Acetyl-CoA (10 ATP)
91
what is the core of a lipoprotein made of?
triglycerides and cholesterols
92
what is the surface of lipoproteins made of
phospholipids
93
what is the stabilizer and director of lipoproteins
apolipoprotein
94
what does chylomicron move
dietary fats to liver & muscle tissues
95
what do VLDL, IDL, LDL move?
endogenous fats from liver to tissues
96
what does HDL move
endogenous fats from tissues to liver
97
how is fatty acid oxidation primed?
CoA at the cost of ATP & PPi
98
How are fattty acid oxidation transferred form cytosol to mitochondria matix?
Carnitine transesterification
99
how many reactions in the matrix?
4
100
how many atp does each fatty acid oxi cycle yield?
14
101
What is the structure of most unsaturated fatty acids
Cis and have double bonds that originate at position ~9 and are spaced out about 3 carbons apart.
102
What is the problem with Oleic Acid (cis-enoyl-CoA)? What is the solution?
Enoyl-CoA hydratase can only add water to trans double bonds. Enoyl-CoA isomerase converts the cis to trans.
103
what is the problem with linoleic acid (2,4-dienoyl-CoA)? what is the solution?
enoyl-CoA hydratase is designed to do trans-double bonds not cis. 2,4-dienoyl-CoA reductase reduces it to trans
104
What does 3,5-2,4-dienoyl-CoA isomerase do?
It catalyzes the isomerizatino of 2,5-enoyl -CoA to 3,5-enoyl-CoA which is better for oxidation which is better for oxidation. 3,5-2,4-dienoyl-CoA isomerase converts 3,5-diene to 2,4-diene which has better conjugation.
105
What are the three solutions for unsaturated fatty acids that are problematic?
1. Isomerize fatty acid from cis to trans
2. Reduce one of the conjugated double bonds
3. Rearrange double bond(3,4 and 5,6 to 2,4 and 4,5 and 2,3), or reduce one db
106
What does fatty acid oxidation in odd-chain's yield and what is it converted to?
Propionyl-CoA which is converted to succinyl-CoA
107
Where is odd-chain fatty acid oxidation most commonly found in?
Plants and marine organism
108
what reactions catalyze the conversion of propionyl-coA to succinyl-CoA?
1.Carboxylation (biotin cofactor)
2. isomerization (no cofactor)
3. isomerization (cobalamin cofactor)
109
What are the cofactors used in the conversion of propionyl-CoA to succinyl-CoA?
biotin (vitamin B7) cofactor and cobalamin (vitamin B12) cofactor
110
What type of ring core does cobalamin have? Is it aromatic? What molecule does it contain?
Corrin ring core. Not aromatic. Tetrapyrrole macrocycle.
111
What kind of center does cobalamin have and what is the center coordinated by?
Cobalt center
Coordinated by adenosyl (Ado) and Dimethyl benzimidazole (DMB)
112
What is methylmalonyl-CoA mutase
series of steps to convert methylmalonyl-CoA to succinyl-CoA. Converts methylmalonyl group to a succinyl-CoA
113
What are methylmalonyl-CoA Mutase important for?
The conversion of methylmalonyl-The conversion of methylmalonyl-CoA to succinyl-CoA is a vitamin B₁₂-dependent radical rearrangement that’s essential for metabolizing odd-chain fatty acids and certain amino acids into a usable TCA cycle intermediate.
114
Where does fatty acid oxidation occur?
Mitochondrion
115
Where are very long chain & brnached fatty acids oxidized?
Peroxisome
116
How do fatty acids first enter the peroxisome?
transferase
117
How many reactions and enzymes are involved in the oxi of fatty acids in the peroxisome?
4 reactions (same as in mitochondria) and 3 enzymes
118
What is peroxisomal fatty acid oxidation activated by?
long-chain acyl-CoA synthase
119
what are the 3 enzymes in peroxisomal fatty acid oxi?
1. Acyl-CoA oxidase
2. Enoyl-CoA Hydratase, 3-L-hydroxyacyl-CoA dehydrogenase
3. Peroxisomal Thiolase
120
What is Ketogenesis?
Acetyl-CoA produced by fatty acid oxidation can be converted to acetoacetate (ketone) or
D−β−hydroxybutyrate (ketone)
121
What can be major sources of energy for the brain during starvation of low carb diets?
Ketone bodies (acetoacetate, acetone, D-B-Hydroxybutyrate)
122
What triggers Ketogenesis?
buildup of acetyl-CoA
123
Why is there a builtup of acytl-CoA sometimes, triggering ketogenesis?
Fatty acid oxidation produces more acytl-CoA than the TCA cycle can process
124
What does enoyl-CoA isomerase do?
Cis to trans isomerization
125
what does 2,4-Dienyol-CoA Reductase do?
Conjugated double bond reduction
126
What does 3,5-2,4-Dienoyl-CoA Isomerase do?
Diene isomerization
127
What is the terminal product of B fatty acid oxi of odd chain
Succinyl-CoA
128
What is succinyl-CoA converted to when it enters the TCA cycle?
fumarate
129
When succinyl-CoA enters the TCA cycle what is a result of this?
shunts malate out of matrix and into the cytosol where it is converted to pyruvate
130
What does the odd chain fatty acid oxi enzyme Propionyl-CoA Carboxylase do?
Carboxylation
131
What does the odd chain fatty acid oxi enzyme Methylmalonyl-CoA Racemase do?
Stereo-isomerization
132
What does the odd chain fatty acid oxi enzyme Methylmalonyl-CoA Mutase do?
Strucutral isomerization
133
Does peroxisomal B Fatty acid oxi require carnitine to transfer them?
no
134
What are the basic reactions in mitochondrial and peroxisomal B-oxidation?
1. Oxidation of the fatty acid (removes 2 electrons).
2. Hydration (adds a water molecule).
3. Oxidation (removes more electrons).
4. Thiolysis (cleavage of the bond to release acetyl-CoA or smaller fragments).
135
Which uses more enzymes peroxisomal or mitochondria
mitochon (4) peroxi (3)
136
137
what is biosynthesis
anabolism of complex molecules from simpler ones
138
Where does biosynthesis take place?
Cytoplasm
139
wehre does B Oxidation occur?
MItochondria.
140
Can Acetyl-CoA cross the mitochon membrane?
No, uses the Citrate-Malate-Pyruvate shuttle to transfer acetyl-CoA into the cytosol
141
What are fatty acids made of?
acetyl-CoA
142
How many fatty acid biosynthesis reactions does it require?
7
143
In prokaryotes, what type of enzymes catalyzes fatty acid biosynthesis?
independent cytosolic enzymes
144
In eukaryotes, what type of enzymes catalyzes fatty acid biosynthesis?
single multifunctional cytosolic enzyme complex
145
What is a growing fatty acid chain linked to help it elongate? It is covalently bonded to this.
a acyl carrier protein (ACP) via Serine
146
What is the fatty acid chain covalently bonded to within the ACP?
Serine
147
What is the first committed step in fatty acid biosynthesis? What does it convert?
Acetyl-CoA Carboxylase (ACC). Converts acetyl-COA to malonyl-CoA
148
Can acetyl-CoA Carboxylase be regulated?
Yes, allosteric, hormonal, covalent. It is also biotin-dependent
149
What does acetyl-CoA Carboxylase (ACC) do?
one to activate CO₂ (biotin carboxylation) and the second to carboxylate acetyl-CoA, producing malonyl-CoA.
150
Does fatty acid synthase have an arm?
Yes, Acyl Carrier Protein (ACP) phosphopantetheine arm. Reaches active sites of multiple subunits
o Single ACP domain can reach both
protomers
151
Synthesizing carbon-carbon bonds
MAT transfers acetyl-CoA and malonyl-CoA to ACP (forming acetyl-ACP and malonyl-ACP)
152
What are the fatty acid elongation reactions
1. Reduction
catalyzed by KR; reduces carbonyl to an alcohol
2. Dehydration
catalyzed by DH; eliminates water
3. Reduction
catalyzed by ER; reduces alkene to alkane
153
154
How many times does the fatty acid elongation reaction happen?
cycles 7 times
155
How may carbons are the fatty acid chains elongated by each cycle?
2 carbons
4+(6×2) = 16 carbons (i.e. palmitate)
156
What is the last step in fatty acid biosynthesis?
End-Capping
157
by what means in the fatty acid chain terminated by in end-capping reaction?
Thioester hydrolysis
158
What is the end-capping reaction catalyzed by and what does it generate?
palmitoyl thioesterase (TE). Generates a terminal carboxylic acid group and regenerates ACP to thiol form
159
How are fatty acid extensions made?
by elongases in the mitochondira or endoplasmic reticulum
160
Which fatty acid extension is independent of the cytosolic fatty aicd synthesis?
Mitochondrial elongation
161
Which fatty acid extension method is dependent on condensation of acetyl-CoA & malonyl-CoA?
Endoplasmic reticulum elongation
162
What are unsaturated fatty acids produced by?
terminal desaturases, addition of double bonds
163
What does desaturation reactions require
oxygen and non-heme iron cofactors
164
WHat fatty acids can mammals cannot produce?
w-3 and w-6. THat's why they are essential to eat
165
How do you form triaglycerides, the primary form of fat storage in the body?
fatty acid esterification
166
What is the pathway of esterification in the mitochondria
glycerol-3-phosphate pathway
167
What is the path of esterification in the peroxisome
dihydroxyacetone pathway
168
What is teh esterification pathway in the endoplasmic reticulum?
glycerol-3-phosphate pathway or dihydroxyacetone pathway
169
if a fatty acid branch has two acyltransferases required, what is it
diacyl branch
170
what does triacyl branch have?
three acyltransferases required
171
What are the four different pathways acetyl-CoA can go into?
citric acid cycle, ketone bodies, fatty acid synth, cholesterol.
172
Whcih pathways regenerage acetyl-CoA?
fatty acid synth and keton body synth
