Term
| What activates Acetyl-CoA Carboxylase (ACCase)? |
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Definition
| Phosphorilation by AMP activated protein kinase |
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Term
| What is the first committed step of fatty acid synthesis in plants? |
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Definition
In chloroplasts, formation of Malonyl-CoA is the first committed step of fatty acid synthesis (point of no return): you can not synthesize anything else from it, exept fa. |
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Term
| How AACase is regulated in plants? |
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Definition
Feedback-Inhibition
Phosphorylation
Thioredoxin (Redox Regulation) |
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Term
| What catalyse all steps of fatty acid synthesis, which occur after Malonyl CoA? |
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Definition
| fatty acid synthase – FAS |
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Term
| Describe animal (yeast) FAS |
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Definition
Type I Complex
2 identical ~250 kDa subunits (Homodimer)
one peptide chain catalyses all consecutive reactions |
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Term
| Describe plant (bacteria) FAS |
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Definition
Type II Complex
several individual subunits (~ 12 different enzymes)
strict coupling of enzymatic activity |
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Term
| Which subunits FAS type I consists of? |
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Definition
Acetyl-CoA-CE Transacylase (AT) (brings Acetyl CoA)
Malonyl-CoA-ACP Transacylase (MT)
β-Ketoacyl-ACP Synthase (CE)
β-Hydroxylacyl-ACP Dehydratase (DH)
Enoyl-ACP Reduktase (ER)
3-Ketoacyl-ACP Reduktase (KR)
[Thioesterase - release fa] |
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Term
| What condensing enzyme does? |
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Definition
| Initialy two C moities comes to condensing enzyme and Acetyl CoA and Malonyl CoA comes and become condensed, C-C bound is formed |
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Term
| Where enzyme activity takes place in FAS? |
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Definition
| Reduction unit of opposite chain |
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Term
| What isoforms of condensing subunit do plants posses? |
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Definition
Plants posses 3 iso-forms of the condensing enzyme (KAS)
Kas III: C2 Acetyl-CoA
Kas I: C4 – C14 Acyl-ACPs
Kas II: C10 – C18 Acyl-ACPs
=> KAS III: initiation of fatty acid synthesis
KAS I: synthesis up to max. C14
KAS II: synthesis up to max. C18 |
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Term
| How is the synthesis of fatty acids terminated in animals (yeasts) ? |
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Definition
| By thioesterase (hydrolase): hydrolysis of Acyls-ACP →free fatty acid and ACP |
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Term
| How is the synthesis of fatty acids terminated in plants? |
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Definition
| Glycerol-3-phosphate acyltransferase: direct transfer of fatty acid from ACP to glycerol → Lipid |
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Term
| Which types of thioesterases does plants have? |
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Definition
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Term
| What is specific about FatC? |
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Definition
FatC specific for short fatty acids accumulation of C10, C12 and C14
found in seeds of plants such as coconut, Cuphea or California laurel
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Term
| What is specific about FatA? |
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Definition
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Term
| Where very-long-chain fatty acids are used? |
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Definition
C20 to C22 for storage lipids
C22 to C26 for sphingolipids
C26 to C32 for waxes |
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Term
| Which fatty acids derivatization (especially desaturation) occur for? |
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Definition
Occurs form C16 fatty acids onwards
most often on C18 fatty acids
catalysed by a family of phylogenetically related fatty acid
derivatizing enzymes |
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Term
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Definition
Very-long-chain fatty acids are synthesized by the addition of further C2 moieties onto long-chain fatty acids
catalysed by a family of enzymes called elongases
reaction sequence very similar to fatty acid synthase (FAS)
Steps: condensation, reduction, dehydration, reduction |
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Term
What is the most important derivatization
of membrane lipids? |
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Definition
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Term
| Where are the desaturases localized? |
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Definition
Most desaturases are localized on the cytosolic site of the ER-membrane
desaturation of C18 to C18:1 can also occur in chloroplasts by a soluble Stearoyl-ACP Δ9-Desaturase !
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Term
| What desaturases require for work? |
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Definition
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Term
| What fatty acid do we usually have as first at ceramide? |
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Definition
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Term
| What sphingolipids have as backbone? |
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Definition
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Term
| How sphingolipids are synthesed? |
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Definition
Sphingosine is synthesized by condensation of palmitoyl-CoA and serine
Transfer of a second fatty acids onto serine creates ceramide
Palmitoyl-CoA (C16) + Serine → Sphingosine
Acyl-CoA (Cn) + Sphingosine → Ceramide |
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Term
| Where is first fa bound to sphingosine? |
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Definition
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Term
| Where is second fa bound to sphingosine? |
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Definition
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Term
| Which pathways exists in the adding of head group to phospho? |
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Definition
CDP diacylglycerol pathway (Phosphatidate is activated)
Diacylglycerol pathway (Headgroup is activated) |
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Term
| CDP diacylglycerol pathway |
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Definition
Phosphatidate + CTP → CDP-Diacylglycerol + PPi
CDP-Diacylglycerol + headgroup → Phospholipid + CMP |
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Term
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Definition
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Term
| How the addition of a headgroup to sphingolipide occurs? |
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Definition
Sphingolipide are synthesized via the transfer of a headgroup from a phospholipid onto ceramide
!!! phospholipids are a prerequisite for sphingolipids !!!
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Term
| What usually sugars in glycosphingolipids posess? |
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Definition
| unusual sugars and can be branched |
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Term
| Synthesis of Sterol-Lipids |
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Definition
Synthesis of isopentenyl-PP via the mevalonate pathway* (cytosol)
Synthesis of farnesyl-PP (peroxisome)
Squalen synthesis and formation of cholesterol (ER)
* plants also have the DoxP pathway
in plastids |
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Term
Where HNG-CoA reductase is situated?
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Definition
| HMG-CoA reductase is an integral protein of the ER membrane |
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Term
How is sterol synthesis regulated?
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Definition
on transcription: steroids
on translation: isoprenoids
Activation/deactivation: proteases, AMP-dependent kinases, protein phosphotases |
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