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MC Biochem 2 > chat 26 > Flashcards

chat 26 Flashcards

1
Q

Triacylglycerol

  • structure
  • function
A

Structure:
-Glycerol and 3 Fatty acids

Function:

  • Long term energy storage
  • reduced and anhydrous
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2
Q

Phospholipid

  • structure
  • function
A

Structure:

  • glyceorl
  • two fatty acids
  • Polar head group containing phosphate

Function
-membrane component

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3
Q

Sphingolipids

  • structure
  • function
A

Structure:

  • sphingosine
  • 2 fatty acids
  • Polar head group containing carbohydrate

Function:
-membrane component especially in cells of CNS

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4
Q

Cholesterol

-function

A

Membrane component

Precursor:

  • Seroid hormones
  • Bile salts
  • vit D
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5
Q

Synthesis of Phosphatidate

A

Substrates:
Glycerol 3-Phospahte
-comes from reductions of dihydroxyacetone-3Phosphate or Phosphorylation of Glycerol
2 Acyl CoA molcules
-activated by CoA for synthesis of Fatty acids

Product:
-Phosphatidate (diacyl glycerol 3-Phosphate)

Cellular Localization:

  • Cytosolic face of smooth ER
  • outer membrane of mitochondria

COMMON INTERMEDIATE IN SYNTHESIS OF TRIACYLGLYCEROLS AND PHOSPHOLIPIDS

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6
Q

Salvage pathway for Phosphatidate

A

Diacylglycerol Kinase
Diacylglycerol + ATP-> Phosphatidate +ADP

Cellular Localization:

  • Cytosolic face of smooth ER
  • outer membrane of mitochondria
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7
Q

Triacylglycerol Synthesis

A

Triacylglycerol Synthetase

2 activities:

  • Phosphatase (1)
  • Diglyceride acyltransferase (2)

Mechanism:

1) Phosphatidate is hydrolyzed and OH replaces Phosphate group to produce Diacylglycerol (DAG)
2) DAG receives 3rd acyl group to form triacylglycerol (remember 3FAs)

Cellular Localization:
-Cytoplasmic side of Smooth ER

Organ localization:
-Liver

Triacylglycerols are transported from the liver via the blood to muscle (energy) or adipose tissue (storage)

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8
Q

Phospholipid synthesis general ideas

A

requires activated intermediate=Phosphatidate

2 Routes

1) activation of diacylglycerol by attaching CDP
2) activation of alcohol (inositol or other alcohol) by attaching CDP
- Phosphatidylinositol
- Cariolipin
- Phosphatidylethanolamine
- Phosphatidylcholine
- Phosphatidylserine

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9
Q

Phosphatidylinositol synthesis

A

1st step) ACTIVATE
Substrates:
-Phosphatidylate
-Cytidine triphosphate (CTP) (really add CMP to form CDP)

Product:

  • CDP-diacylglycerol
  • -Pyrophosphate which is hydrolyzed to provide energy for reaction

2nd step) Put new head group on
Substrate
-CDP-diacylglycerol
-Alcohol (Ex: inositol)

Product:

  • Phosphotidylinositol
  • CMP

Inositol can be phosphorylated by specific kinases to phosphotidylinositol 4,5-bisphosphate

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10
Q

How is phosphatidylinositol unusual?

A

contains specific fatty acids:
C1=Stearic acid
C2=arachidonic acid

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11
Q

Cardiolipin Synthesis

A

Found in mitochondria

If the CDP-diacylglycerol reacts with phosphotidylglycerol then it forms Cardiolipin (diphosphotidylglycerol)
-2 phosphatidyls hooked together by glycerol

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12
Q

Phosphotidylethanolamine synthesis

A

1) ethanolamin acitivated by Phosphorylation by the gamma phosphate of ATP
2) Phosphorylethanolamine reacts with CTP to form CDP-ethanolamine
- Pyrophosphate hydrolyzed to provide energy for reaction
3) CDP-ethanolamine reacts with diacylglycerol and CMP acting as a leaving group

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13
Q

Phosphatidylserine synthesis

A

Synthesized from phosphatidylcholine or phosphatidylethanol amine by exchange of head groups with serine

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14
Q

What is the common precursor for synthesis of Sphingolipids

A

Ceramide

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15
Q

Ceramide Synthesis

A

1) Fatty Acid CoA (Palmitoyl CoA) + serine ->3-ketosphinganine
- releasing CO2 + CoA
2) reducing Carbonyl to Hydroxyl producing dihydrosphingosine
- NADPH to NADP+
3) Addition of Second Fatty acids to Alpha Amino group of serine producing dihydroceramide
4) Double bond is formed to the right of OH producing Ceramide
- FAD reduced to FADH2

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16
Q

What are the different sphingolipids

A

REMEMBER CERAMIDE IS COMMON PRECURSOR for:

  • Sphingomyelin
  • cerebroside
  • gangliosides
17
Q

Ganglioside Synthesis

A

containCarbohydrates:

  • activated UDP glucose/galactose
  • added one at a time to ceramide
18
Q

Cholesterol Structure

A

27 carbons

  • Four rings called steroid nucleus (A, B, C, D)
  • -8carbon chain (20-27C
19
Q

Cholesterol Synthesis Overview

A

27 Carbons are derived from Acetyl CoA

Cellular Localization

  • Cytoplasm
  • Endoplasmic Reticulum

Organ Localization:

  • Liver parenchymal cells
  • Intestine (secondary site)

3 Stages:

1) Synthesis of isopentenyl pyrophosphate (activate isoprene)-cytoplasm
2) 6 molecules of isopentyl pyrophosphate condense to form squalene- ER
3) Cyclization of squalene-ER

20
Q

Lipid (Cholesterol) Transport

A

Lipids are transported in the blood and other bodily fluids as spherical complex with apoproteins. (AKA apolipioproteins)

21
Q

Apoproteins

  • Where are they synthesized
  • function
A

Synthesized in the liver and intestine

Function:

  • Solubizile hydrophobic lipids
  • contain cell-targeting signals
22
Q

What is a healthy humans HDL/LDL ratio

A

3.5

23
Q

What does excess cholesterol lead to?

A

formation of atherosclerotic plaques leading to disease and death

24
Q

How are Lipoprotein (aproprotein) particles classified?

A

By density:

  • as the move throughout the body, there:
  • density and protein concentration increases
  • size and lipid concentration decrease
Less dense:
Chylomicrons
Chylomicron remnants
VLDL-very low density lipoproteins
IDL-intermediate density lipoproteins
LDL-low density lipoproteins
HDL-high density lipoprotein
25
Q

Chylomicrons

A 
Dietary lipids(C, CE, PL, TAG) are removed from the intestine as chylomicrons
-Transported in the blood

Lipoprotein Lipases

  • located along blood vessels in tissues that use fatty acids as fuel
  • Hydrolyzes TAG, releasing fatty acids
  • as TAG (triacylglycerol) is removed chylomicrons converted to Chylomicron remnants
26
Q

Chylomicron remnants

A

Liver removes cholesterol rich chylomicrons remnants from the blood stream

27
Q

VLDL

A

Very Low density lipoproteins

Excess C, CE, and TAG transported out of the liver as VLDL and enter the bloodstream
-Lipoprotein lipases Hydrolyze TAG, as TAG is removed, they are converted to IDL-> LDL

28
Q

IDL

A

Intermediate Density Lipoproteins

LDL precursor
-rich in CE

Transported into blood:

  • half are taken up by the liver for processing
  • half are converted to LDL for further removal of TAG which converts them VLDL->IDL->LDL
29
Q

LDL

A

low-density Lipoprotein
BAD CHOLESTEROL

Major Cholesterol Carrier

  • transpsorts CE to peripheral tissue
  • regulates DE novo synthesis of cholesterol

LDL Contain:

  • Shell of phospholipids and C
  • 1500CE surround by PE and C
  • one APO B 100 molecule that recognizes target cells

C in LDLs take up cells by receptor mediated endocytosis

30
Q

HDL

A

High Density Lipoprotein
Reverse cholesterol transport
-picks up C from peripheral tissue, esterifies it and carries it to liver or tissue that uses C as precursor for steroid synthesis

GOOD cholesterol

31
Q

Familial Hypercholesterolemia

A

Usually caused by absence or deficiency of functional LDL receptors

  • inherited high cholesterol in the form of LDL
  • when concentration is high it accumulates inthe blood as atherosclerotic bplaques
32
Q

Cholesterol is precursor for synthesis of:

A

Bile salts
Steroid Hormones
Vitamin D

33
Q

Vitamin D

A

Stimulates absorption of calcium and phosphate

Activated by P450 system

34
Q

Bile Salts

A

Poly derivatives (breakdown particles) of cholesterol that solubilize dietary lipids:

  • Glycocholate
  • Taurocholate

**Detergent

Solubillization:

  • exposes more surface area of cholesterol to digestive action of lipases
  • increases absorption of cholesterol in intestine

Localized in:

  • synthesized in liver
  • stored in gall bladder
  • function in small intestine
35
Q

Cytochrome P450 System

A

A family of proteins containing a cytochrome with a bound iron

Localization:

1) Cellular-two forms
- Mitochondrial-hydroxylation of steroids
- Endoplasmic Reticulum-detoxification of drugs/toxins
2) Organs:
- liver, small intestine, kidney, steroid hormone producing tissue

Function:
Detoxification of foreign substance

36
Q

Steroid Hormones

A

5 Classes:
1) Progestagens
-synthesized in corpus luteum-temporary site in ovary after follicle is released
Ex: Progesterone

2)Glucocorticoids
-synthesized in adrenal cortex
Ex: Cortisol

3)Mineralocorticoids
-synthesized in adrenal cortex
Ex; Aldosterone

4) Androgens
-synthesized in testes
Ex: testosterone

5)Estrogens:
-synthesized in ovaries
Ex: Estrone

MC Biochem 2 (31 decks)

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