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Biochemistry 2 > Lipids > Flashcards

Lipids Flashcards

1
Q

Method of action of hormone?

A

Interacts with a far away organ via blood stream

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2
Q

Method of action of paracrine?

A

Acts upon neighboor tissues

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3
Q

Method of action of autocrine?

A

Acts upon the cell that produce it

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4
Q

Method of action of juxtacrine?

A

Acts upon cells that are right next to thee original cells

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5
Q

Method of action of pheromones?

A

Acts upon subjects of the same species: from exocrine gland

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6
Q

3 types of signaling molecules

A

Lipids, proteins and CHO

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7
Q

What is a bioactive lipid?

A

Acts as a signal molecule

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8
Q

Are fatty acids SM?

A

Yes

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9
Q

Are glycerophospholipids SM?

A

Yes

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10
Q

Are sphingolipids SM?

A

Yes

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11
Q

Are sterol lipids SM?

A

Yes

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12
Q

Are prenol lipids SM?

A

Yes

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13
Q

Are saccharolipids SM?

A

No

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14
Q

Are polyketides SM?

A

No

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15
Q

Are glycerolipids SM?

A

No

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16
Q

What is a glycerolipid?

A

Di-triacylglycerol

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17
Q

What are inositol phosphates?

A

PIP3 and IP3

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18
Q

What are the precursors of inositol phosphates?

A

Glycerophospholipids as PIP2

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19
Q

To obtain PIP3, we should […] PIP2

A

Phosphorylate with PI3 kinase

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20
Q

To obtain IP3, we should […] PIP2

A

Hydrolyze with phospholipase C

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21
Q

PIP3 is important because…

A

It leads to a nucleation point for protein complexes involved in biosignaling

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22
Q

Two sphingolipids and their derivatives act as intracellular signal…

A

Ceramide and sphingomyelin

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23
Q

What is the special role of ceramide?

A

Stabilizes lipids rafts

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24
Q

Ecosanoids act as…

A

Paracrine factors

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25
Q

Prostanglandin E1 is an…

A

Ecosanoid

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26
Q

What does prostaglandin regulate?

A

Smooth muscle contraction; blood flow and body temperature

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27
Q

Thromboxanes are..

A

Ecosanoids

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28
Q

Thromboxanes regulate…

A

Blood clothing

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29
Q

Leukotrienes are…

A

Ecosanoids

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30
Q

Leukotrienes regulate…

A

Airway smooth muscles contractions

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31
Q

Sterol lipids act as…

A

Hormones: they regulate gene expression

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32
Q

Sterol hormones are derived from…

A

Cholesterol

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33
Q

Fat-solubles vitamin are…

A

Prenols

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34
Q

Prenols act as…

A

Hormones and pigments

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35
Q

Examples of prenols

A

Vitamin D, A, E, K

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36
Q

Role of Vit D

A

Precursor to a hormone that regulate calcium metabolism

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37
Q

Role of Vit A

A

Furnishes visual pigment; regulator of epithelial cell growth

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38
Q

Role of Vit E

A

Protection of membrane lipids from oxidation

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39
Q

Role of Vit K

A

Blood-clothing process

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40
Q

Tocopherols are pretty much like prenols. Examples of tocopherols

A

Vit E, K and warfarin (blood anticoagulant, which inhibits prothrombin)
Ubiquinone and plastoquinone (electron carrier in mito/chloro)

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41
Q

Which membrane of a cell contain the most cholesterol amount?

A

Plasma membrane

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42
Q

Why are membranes mobile?

A

Non covalent interactions

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43
Q

At RT, what is the state of a lipid bilayer?

A

Semisolid liquid ordered state: strongly constrained and paracrystalline

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44
Q

Sterols have paradoxal effects on membrane, explain

A

They tend to stabilize unsaturated fat, but they mobilize saturated fatty acids

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45
Q

What is a membrane raft?

A

Island of glued lipids, with high content of sphingolipids and cholesterol: quite unmobile considering the variety of sphingo and phospho

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46
Q

What is an amphitropic protein?

A

Free or attached to the membrane, depending on bioregulation (eg.: phosphorylation)

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47
Q

What is a peripheral protein?

A

Binds to membrane protein depending on pH, chelating agent, urea and carbonate

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48
Q

What is an integral protein?

A

Imbated in the membrane

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49
Q

What is a GPI-linked protein?

A

Linked to the membrane with glycophosphate

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50
Q

What is the common lenght of fatty acids?

A

10-20 fatty acids, but range = 4-28

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51
Q

Lateral diffusion of phospholipids is..

A

Uncatalyzed

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52
Q

Uncatalyzed flip-flop is..

A

Not going to happend

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53
Q

Catalyzed transbilayer delocalization needs..

A

ATPase

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54
Q

What is a flippase?

A

Phospho to the bottom; P-type ATPase

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55
Q

What is a floppase?

A

ABC transporter to the top of the bilayer

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56
Q

What is a scramblase?

A

Moves lipids in either direction, toward equilibrium

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57
Q

3 components of cytoskeleton

A

Ankyrin, spectrin and junctional complex (actin)

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58
Q

What if lipids or proteins bind to cytoskeleton?

A

Not free anymore

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59
Q

Raft is

A

An island of glued sphingolipids and cholesterol + calveolin; quite unmobile

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60
Q

What is a calveola?

A

A semi closed vesicle in the membrane, created by calveolin dimers

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61
Q

What is the role of calveola?

A

Signaling and localization

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62
Q

Membrane fusion needs 5 things

A

2 membranes to fusionate and 3 G prot: v-SNARE, t-SNARE and SNAP25

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63
Q

v-SNARE binds to…

A

Coming vesicle (or membrane)

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64
Q

t-SNARE binds to…

A

Plasma membrane of targeted cell

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65
Q

SNAP25 induces..

A

A zipping up of v and t-SNARE

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66
Q

Zipping causes..

A

Curvature + lateral tension = favorable hemifusion

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67
Q

What is hemifusion?

A

When outer membranes of both are fusioned

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68
Q

Complete fusion induces..

A

A pore, that will widden

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69
Q

What does disassembly the SNA G-Prot?

A

NSF

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70
Q

Before starting fusion process, what does the synapse need?

A

A starter: in neuron, it is the Ca2+ concentration

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71
Q

There are 6 types of transport

A

Simple diffusion; facilitated diffusion; primary active transport; secondary active transport; ion channel; ionophore-mediated ion transport

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72
Q

What is the benefit of having a transporter?

A

Speed of passage

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73
Q

There are two major categories of tranporters?

A

Carriers and channels

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74
Q

Which transporters are carriers?

A

Primary, secondary and passive transporter

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75
Q

Which transporters are channels?

A

Ion gated channels + ionophore-mediated ion transporter

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76
Q

Glucose transporter is a…

A

Passive transporter (from natural gradient, only travel the membrane rapidly)

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77
Q

Glucose transporters are dependent of insulin.. why?

A

Their presence on the membrane (via vesicles) is determined by the interaction or not of insulin on its receptor

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78
Q

Carbon dioxide and water can be broken down into…

A

Bicarbonate + H+ (neutralized by Cl-)

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79
Q

In erythrocytes of respiring tissues..

A

The CO2 enters the cell, is broken down, bicarbonate diffuses in the blood stream while the Cl- enters the cell (it is an antiport ion passage)

80
Q

In erythrocyte of lungs…

A

The bicarbonate enters the cell while the Cl- exits it, pushing leftward the reaction.. CO2 leaves the erythrocyte

81
Q

Types of ion passage

A

Uniport (it enters solely), symport (enters with a friend) or antiport (it enters as long as something else exits)

82
Q

There are two types of active transport: primary and secondary

A 
Primary = ATP breakdown leads to the entry of a substrate against its electrochemical gradient
Secondary = 2 steps : 1- ATP breakdown make a substrate exit to create a gradient and 2- that exiting substance help another one to enter the cell against its electrochemical gradient
83
Q

What is a P-type ATPase?

A

Cation transporter, reversibily phosphorylated by ATP

84
Q

In which category of transport is P-type ATPase a transporter?

A

Active transport: both primary or secondary

85
Q

ATPase with moving calcium: there are seven steps

ATPase with moving calcium step 1

A

Ca2+ (M domain) and ATP (N domain) bind to the E1 receptor (cytosol face): N domain moves

86
Q

ATPase with moving calcium step 2

A

The switch conformation allows the Asp351 in the P domain to be phosphorylated (E1-P)

87
Q

ATPase with moving calcium step 3

A

The phosphorylation opens up the receptor (E2-P), Ca2+ can leave

88
Q

ATPase with moving calcium step 4

A

A domain moves, ADP+Pi leave

89
Q

ATPase with moving calcium step 5

A

E2-P become E2

90
Q

Which domain was phosphorylated in the Ca2+ ATPase?

A

P domain

91
Q

ATPase with moving calcium step 6

A

A domain resets

92
Q

ATPase with moving calcium step 7

A

P and M domains reset to become E1 conformation

93
Q

Na+/K+ ATPase in 5 steps

Na+/K+ ATPase step 1

A

3 inside Na+ bind to the transporter

94
Q

Na+/K+ ATPase step 2

A

Phosphorylation by ATP opens up the gate (Enz II)

95
Q

Na+/K+ ATPase step 3

A

Releasing of Na+ induces binding up of 2 K+

96
Q

Na+/K+ ATPase step 4

A

K+ presence induces dephosphorylation (Enz I)

97
Q

Na+/K+ ATPase step 5

A

Dephosphorylation induces 2 K+ to enter

98
Q

Internal concentration of K+

A

140 mmol/L

99
Q

Internal concentration of Na+

A

12 mmol/L

100
Q

External concentration of K+

A

4 mmol/L

101
Q

External concentration of Na+

A

145 mmol/L

102
Q

F-Type ATPase is..

A

A reversible proton pump/ATP synthase

103
Q

ABC transporters stand for…

A

ATP binding cassette

104
Q

What is an ABC transporter?

A

They transport many solutes against a concentration gradient

105
Q

Examples of solute transported by ABC transporters?

A

Amino acids, peptides, proteins, metal ions, lipids, bile salts, drugs

106
Q

What is the difference between symporters and secondary active transport?

A

Symporter are composed of an ion to which a substrate is bound. This S enters the cell by the driving force of the gradient of the ion.
A secondary active transport uses 2 ATPases: one to produce energy via the travel of an ion through its gradient, so the second, against its gradient, can travel as well

107
Q

P-type ATPase is an active transporter, but it is also an…

A

Antiporter

108
Q

What is homeostasis?

A

Organized and regulated dynamic steady state

109
Q

Why don’t erythrocytes have mitochondria or nucleus?

A

They must not use glucose or O2, just transport it

110
Q

10 principles of regulation of enzymes

Regulated enzymatic activity step 1

A

(Extracellular) signal

111
Q

Regulated enzymatic activity step 2

A

Activation of transcription factor like (de)phosphorylation and interaction to produce mRNA of specific genes

112
Q

Regulated enzymatic activity step 3

A

mRNA degradation rate (sort of control over expression)

113
Q

Regulated enzymatic activity step 4

A

mRNA translation rate on ribosome leads to an enzyme

114
Q

Regulated enzymatic activity step 5

A

Rate of protein degradation

115
Q

What is a turnover?

A

Degradation of a protein (time of half-life rates it)

116
Q

Regulated enzymatic activity step 6

A

Enzymatic sequestration: compartimentalization (if an enzyme is sequestred, it limits its activity)

117
Q

Regulated enzymatic activity step 7

A

The actual binding of the enzyme and its substrate (concentration of substrate, Km)

118
Q

Regulated enzymatic activity step 8

A

Presence of allosteric activator/inhibitor

119
Q

Regulated enzymatic activity step 9

A

(De)phosphorylation alters the activity of enzyme

120
Q

Regulated enzymatic activity step 10

A

Regulatory protein (PKA, which is cAMP dependent, is not active until cAMP binds to its inhibitory subunits, releasing the C substrate binding cleft)

121
Q

Organism level regulation examples (4)

A

Opposite pathways aren’t favored simultaneously; maximization of product utilization (end products are precursors of other things); alternate directions for fast switching; end product is an inhibitor of cycle

122
Q

How do lipids yield energy?

A

By fatty acid oxidation: removal of acetyl-CoA

123
Q

Why do triglycerides are good at being energy source?

A

Inert, insoluble (no osmolarity), 2x protE/CHOE, highly reduced

124
Q

Lipids are digested and transported in 7 steps

Lipid digestion step 1

A

Bile salts (from the liver) form micelles of triacylglycerol in the small intestine

125
Q

Lipid digestion step 2

A

Intestinal lipases breakdown TG into mono/biG, fatty acids and glycerol

126
Q

Lipid digestion step 3

A

Monomeres are converted back to TG into the small intestine mucosa

127
Q

Lipid transport step 4

A

TG + chol + apolipoproteins are integrated into chylomicron (in the liver)

128
Q

Lipid transport step 5

A

Chylomicrons move through lymphatic system and bloodstream to tissues like myocytes and adipocytes (not arrived yet)

129
Q

Lipid transport step 6

A

ApoC-II (capillary) converts TG to f.a. and glycerol

130
Q

Lipid transport step 7

A

F.a enter the cells and are oxidized as fuel

131
Q

What is a chylomycron?

A

A coat of apolipoproteins surounds cholesterol and TG

132
Q

How does mobilization of lipids work?

A

Via G-prot receptor of glucagon: PKA phosphorylates an hormone sensitive lipase, which leads to the release of a f.a. in the bloodstream

133
Q

How does HSL works, once phosphorylated?

A

PKA phosphorylates HSL and peripilin (surface protein of lipid droplet). Phosphorylated peripilin permits HSL to access surface of droplet to hydrolyze TG into f.a.

134
Q

Once f.a. are released of a lipid droplet, what happens?

A

They leave the adipocyte via albumine, which make them travel in the bloodstream to the myocyte (enters via a f.a. transporter)

135
Q

Once the f.a. enters the myocyte, how does it produce energy?

A

The f.a. is oxidezed to CO2, and the energy is conserved into ATP

136
Q

F.a. are transported to be oxydized, but what about glycerol of the original TG?

A

It is phosphorylated by glycerol kinase-G3PD-triose phosphate isomerase into G3P, which is an intermediate into glycolysis preparatory phase that is gonna be oxidized as well

137
Q

How % does glycerol contribute to energy yielding of TG?

A

5%

138
Q

What is activation of F.A.?

A

It is the preparatory phase (as in glucose) to form fatty acyl-CoA, which is gonna release enough energy to regenerate much more ATP

139
Q

How does f.a. activation work?

A

1- ATP is broken down into AMP-f.a. and PPi (which will be hydrolyzed into 2Pi) by f.a. acyl-CoA synthetase
2- AMP is released by the attack of CoA, forming thioester f.a. acyl-CoA

140
Q

How does f.a. enters the mitochondria, once inside the myocyte (2)?

A

1- Small f.a. of 12/- C diffuse freely
2- Longer f.a.-acyl-CoA form f.a.-carnitine (in the cytosol) and enter the matrix by facilitated diffusion by acyl-carnitine transporter; f.a.-carnitine is transformed into f.a. acyl-CoA + carnitine in the matrix by carnitine acyl transferase II

141
Q

Once in the mitochondria matrix, what does happen of the f.a.?

A

B-oxidation

142
Q

How do we know how much acetyl-CoA is the f.a. gonna release?

A

of total C/2

143
Q

What is the fate of acetyl-CoA once produced?

A

It enters the TCA cycle, releases electrons and CO2, then those electrons enter the ETC to regenerate ATP

144
Q

Where does B-oxidation occurs on a f.a.?

A

Carboxyl-end

145
Q

How much FADH2 and NADH are formed from a f.a.?

A

(Acetyl-CoA)-1

146
Q

How many ATP by FADH2?

A

1,5

147
Q

How many ATP by NADH?

A

2,5

148
Q

B-oxidation step 1

A

Acyl-CoA dehydrogenase take off H2 to FAD from the carboxyl end

149
Q

B-oxidation step 2

A

Enoyl-CoA hydratase add an hydroxyl group to the C right before the carboxyl end (formation of acetyl at the carboxyl end)

150
Q

B-oxidation step 3

A

B-hydroxyacyl-CoA dehydrogenase take off this water around the third C to give it to NAD (forming a new carboxyl end)

151
Q

B-oxidation step 4

A

Acyl-CoA acetyltransferase (thiolase) puts a CoA to the new formed carboxyl end, which replace the odd one that can now leave as acetyl-CoA

152
Q

Two additional enzymes are required with unsaturated f.a.

A

Isomerase (from cis to trans) + reductase (from 2 double bonds to only one)

153
Q

When odd number f.a. occurs, what is the pathway?

A

Acetyl-CoA + propyonyl are formed. The acetyl-CoA goes to the TCA cycle, while the propyonyl is transformed in a 3 enzymes pathway to become succinyl and enter the TCA that way

154
Q

What are the 3 enzymes of propionyl-CoA pathway?

A

propionyl-CoA carboxylase (with biotin); methylmalonyl-CoA epimerase; methylmalonyl-CoA mutase (with B12)

155
Q

B-oxidation in mitochondria vs peroxysome

A

1- There is no ETC, O2 is directly reduced from FADH2

2- NADH/Acetyl-CoA can’t be oxidized in the peroxysome, they are exported to come back later

156
Q

Some oxidation occurs in the ER

A

It is w-oxidation

157
Q

What is the difference between w and B-oxidation?

A

Not the carboxyl end but the first carbon of medium f.a. chains; when the begining is transformed to carboxyl end as well, it can enter b-oxidation

158
Q

Net yield regarding NADH in w-oxidation?

A

1 (1 preparatory for 2 yielded)

159
Q

What is a ketone body?

A

Extra acetyl-CoA that didn’t undergo TCA cycle, it is used by some extra-hepatic tissues: it allows a continuous f.a. oxidation

160
Q

What are the three types of ketone bodies?

A

Acetone; acetoacetate and D-B-hydroxybutyrate

161
Q

Where are the ketone bodies formed?

A

In the liver

162
Q

Ketone bodies biosynthesis

A

2 acetyl-CoA are merged into acetoacetyl-CoA, which leads to HMG-CoA
HMG-CoA is a precursor of the three types of ketone bodies: it forms acetoacetate, which either undergo acetone or reversibly undergo D-B-hydroxybutyrate

163
Q

Ketone bodies catabolism

A

When energy needs occur, D-B-hydroxybutyrate undergo acetoacetate form and reduces NAD; acetoacetate becomes acetoacetyl-CoA by succinyl-CoA; and thiolase breakdown acetoacetyl-CoA into two acetyl-CoA

164
Q

Biological functions of lipids (9)

A

Energy storage; membrane components; anchors; cofactors; signals; pigments; detergents; transporters; antioxidants

165
Q

How do we synthetise f.a.? (2)

A

1- Formation of malonyl-CoA

2- Additions of 2 carbons chains

166
Q

What is malonyl-CoA?

A

Acetyl-CoA + CO2

167
Q

What is the enzyme catalyzing formation of malonyl?

A

Acetyl-CoA carboxylase made up of three subunits: biotin carrier protein - biotin carboxylase - transcarboxylase

168
Q

Malonyl formation step 1 (out of 3)

A

Biotin arm + carbonate + ATP = binding to the biotin carboxylase + CO2 at the nitrogen ring + ADP + Pi

169
Q

Malonyl formation step 2

A

Biotin carboxylase activates CO2, which switches the conformation (everything goes to the third subunit)

170
Q

Malonyl formation step 3

A

Trancarboxylase catalyzes the addition of Acetyl-CoA to CO2, once malonyl is formed, it leaves the acetyl-CoA carboxylase

171
Q

Fatty acid synthesis phase 2 is…

A

Addition of two carbons to chain

172
Q

Phase 2 has 4 steps

F.a. synthesis phase 2 step 1

A

CONDENSATION: Malonyl group attached to fatty acid synthase by thiolester (-S) + acetyl group (previously added) on the f.a.synth condense to release the CO2 of the malonyl

173
Q

F.a. synthesis phase 2 step 2

A

REDUCTION: The B carbon of the thiolester carbon is reduced from a carbonyl to hydroxyl by the help of NADPH

174
Q

F.a. synthesis phase 2 step 3

A

DEHYDRATION: the B-carbon is dehydrated and form a new double bond with the alpha carbon (release of water)

175
Q

F.a. synthesis phase 2 step 4

A

REDUCTION: formation of a saturated chain by oxidation of NADPH again

176
Q

4 steps of phase II of f.a. synthesis in short

A

Add some stuff, reduce to put water (easier to take off after), take off water to have only a carbon chain, reduce it again to get a saturated chain

177
Q

FAS (f.a. synthase) can be found in two types

A

Type 1 for vertebrates; type 2 for fungi/plants/bacteria

178
Q

After the formation a two carbon saturated chain, there are 2 more steps before the cycle turns again

A

5- Translocation from ACP (-S) to -S from the KS subunit of f.a. synthase
6- The acetyl-CoA from the malonyl becomes the starter of another cycle (the extra acetyl-CoA)

179
Q

How many subunits are there in the f.a. synthase?

A

7

180
Q

What is the “model” fatty acid formed by f.a. synthase?

A

Palmitate (16:0)

181
Q

What can happen to palmitate once synthesized?

A

It can undergo elongation or desaturation to produce a variety of fatty acids

182
Q

What is the desaturation enzyme in animals?

A

Fatty acyl desaturase

183
Q

What are the three products of arachidonate (20:4)?

A

Leukotrienes, prostanglandins/thromboxanes

184
Q

Where does fatty acid synthesis occur?

A

Cytosol of cells in animals - chloroplasts of plants

185
Q

Where does further processing of fatty acids occur? (elongation/desaturation)

A

Smooth ER - elongation might happen in the mitochondria as well

186
Q

What is the donor of electron in fatty acid anabolism

A

NADPH

187
Q

Synthesis of fatty acids leads to two fates:

A

Phosphatidic acid leads to TG or glycerophospholipids

188
Q

Biosynthesis of cholesterol

Where does it happen?

A

In cytosol

189
Q

Where does G3P to phosphatidic acid occur?

A

Liver+kidney

190
Q

Biosynthesis of cholesterol happens in 4 steps

Cholesterol synthesis step 1

A

3 acetate are condensed to form a 6 carbon unit: melavonate

191
Q

Cholesterol synthesis step 2

A

Conversion of melavonate to activated isoprene (P-P)

192
Q

Cholesterol synthesis step 3

A

Polymerization of 6 5-carbon isoprene units to form a 30 units linear squalene (almost 4 rings)

193
Q

Cholesterol synthesis step 4

A

Cyclization of squalene

194
Q

Further processing of cholesterol leads to…

A

Steroid hormones; bile acids; vitamin D

195
Q

Activated isoprene is not only processed into cholesterol.. It can be processed into…

A

Vit A/E/K; carotenoids; plant hormones; isoprene; quinone electron carriers; dolichols; phytol chain of chlorophyll; rubber

Biochemistry 2 (3 decks)

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