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Lipids > business > Flashcards

business Flashcards

1
Q

FA as a fuel?

A

Stored as triacylglycerol

TAG oxidised to meet energy needs

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2
Q

fatty acids we need to know

A

Palmitate is 16 Carbons long

Stearate is 18 Carbons long

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3
Q

Plant oil

A

55-83% oliec acid

liquid at room temp

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4
Q

Animal fats

A

Saturated fatty acids

solid at room temp

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5
Q

What does hydrogenation do to fats

A

adds H over the double bond i.e unsaturated to saturated

increases melting point

make spreads and shit

Level of hydrogenation controlled by H2, temp and time

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6
Q

What does hydrogenation do to fat stereochemistry

A

converts cis to trans which is more stable

Trans isomers are implicated in disease. bad cholesterol

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7
Q

Types of membrane lipids

A

Phospholipids
Glycolipids
Cholesterol

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8
Q

Phospholipid structure

A

.

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9
Q

Sphingosine

A

instead of glycerol sometimes

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10
Q

Phospholipids derived from glycerol

A

Phosphoglycerides

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11
Q

Phospholipid without alcohol

A

Phosphatidate

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12
Q

Glycolipids

A
  • Includes a fatty acid unit and a sugar unit (glucose or galactose)
  • Orient asymmetrically with the sugar pointing extracellularly
  • Have a sphingosine backbone
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13
Q

Cholestrol

A
  • 25% of neuronal lipid is cholesterol
  • Has a hydroxyl group at one end.
  • Long carbon tail
  • Many aromatic rings
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14
Q

Soluble Proteins

A

Common examples are N-myristoyl and S-palmitoyl anchoring motifs

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15
Q

β-oxidation

A

• Fatty Acid ->Acetyl CoA->Citric Acid Cycle->Energy

1) Oxidation: activated FA oxidized to introduce a double bond by a dehydrogenase
b. Redox cofactor is FAD FADH2

2) Double bond hydrated-introduces a hydroxyl group
a. Catalysed by hydratase family enzyme

3) OH group oxidised Ketone
a. Redox therefore catalysed by dehydrogenase
b. Redox cofactor= NAD+ NADH

4) Fatty Acid Cleavage acetyl CoA and FA that is 2C shorter
a. Catalysed by thiolase enzyme
b. Cofactor= CoA

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16
Q

Absorption, Transport and Storage or fatty acids

A

Most ingested FA are triacylglycerol (TAG)
Lipases neck it to fatty acids
absorbed by intestinal cells
packages TAG into chylomicrons
chylomicrons travel in lymph and blood to adipose and muscle cells
broken down to FFA by active hormone-sensitive lipase if needed or just stored as TAG

17
Q

Triacylglycerol as energy stores

A

Highly concentrated stores of metabolic energy because they are reduced

TAG are nonpolar so are stored in an anhydrous form

18
Q

Fatty Acid Activation and Transport

A

FA must be activated first before it can enter mitochondria via formation of thioester linkage to coenzyme A

Reaction takes place on outer mitochondrial membrane
Translocase enzyme does the actual translocation

19
Q

Ketone Bodies

A

are formed from Acetyl CoA when fat breakdown predominates

20
Q

Fatty acid precursors

A

recursors for nearly all FA synthesis is acetyl CoA

21
Q

Sources of Acetyl CoA

A

glycolysis (pyruvate)
fatty acid degradation
and fatty acids

22
Q

Fatty Acid Synthesis

A

takes place in the cytosol

23
Q

Formation of malonyl CoA

A

Carboxylation of acetyl to malonyl
• First irreversible reaction is the committed step in fatty acid synthesis

• Reaction is catalysed by cytoplasmic enzyme acetyl CoA Carboxylase 1 (and 2)

24
Q

acetyl CoA Carboxylase 1

A

Plays essential roles in regulating fatty acid synthesis and degradation for fatty acid metabolism

25
Q

palmitate formation

A

Thioesterase hydrolyses C16-acyl ACPà palmitate and ACP

Acts like a ruler to determine FA chain length

8 Acetyl CoA + 7 ATP + 14 NADPH + 6H ——–> Palmitate + 14 NADP+ + 8 CoA + 6 H2O + 7 ADP + 7 Pi

26
Q

Citrate as a carrier

A

• Citrate carries acetyl groups from mitochondria to the cytoplasm for fatty acid synthesis
• Mitochondria, however, are not readily permeable to acetyl CoA
• Barrier to acetyl CoA is bypassed by citrate, which carries acetyl groups across the inner mitochondrial
membrane

27
Q

Sources of NADPH for Fatty Acid Synthesis

A

Return of oxaloacetate formed in transfer of acetyl groups to the cytoplasm

Additional 6 molecules of NADPH required come from pentose phosphate pathway

28
Q

Elongation and unsaturation of fatty acids are

accomplished by accessory enzyme systems

A

elongation reactions and addition of double bonds catalysed by enzymes mainly on cytosolic face of endoplasmic reticulum

29
Q

When is fatty acid synthesis maximum

A

maximal when carbohydrate and energy levels are plentiful and when fatty acids are scarce

30
Q

Allosteric regulation

A

stimulation of ACC by citrate
inhibition of ACC by palmitoyl
CoA

31
Q

Hormonal regulation

A

Glucagon and Epinephrine inhibit fatty acid synthesis
by ACC phosphorylation by AMP-activated protein kinase

Insulin stimulates fatty acid synthesis removal of phosphate

32
Q

LDL

A

Primary source of cholesterol from cells outside liver and intestine is plasma (not de novo synthesis)àPrimary source is LDL

33
Q

Cholesterol Synthesis

A

Derived from acetyl CoA in a three-stage synthetic process

1) Synthesis of isopentenyl pyrophosphate (an inactivated isoprene that is the key building block of cholesterol)
2) Condensation of six molecules of isopentenyl pyrophosphate to form squalene

3) Cyclization of squalene and tetracyclic product is subsequently converted into cholesterol
1) occurs in cytoplasm, 2) and 3) occur in ER

34
Q

Stage One: Mevalonate Synthesis

A

Starts with formation of HMG-CoA from acetyl CoA

COMMITED step

35
Q

HMG-CoA reductase drugs

A

target of statin drugs to treat heart disease

Lovostatin

36
Q

Receptor-mediate Endocytosis

A

1) B100 (apolipoprotein)- Found on surface of LDL particles and mediates binding to LDL receptor
2) Receptor: LDL particle complex is internalized by endocytosis
3) Endosome is acidified (proton pump) which causes the receptor to release LDL cargo
a. Some receptor returns to the cell surface
b. Some receptor is degraded
4) Endosome fuses with lysosome (full of enzymes)
a. Protein component hydrolysed to free amino acids
b. Cholesterol esterols hydrolysed (lipase) to release free cholesterol
i. Membrane biosynthesis
ii. Re-esterified (-chol-oleate: stored inside cell)

37
Q

Absence of LDL receptor

A

leads to hypercholesterolemia and atherosclerosis

38
Q

Familial hypercholesterolemia

A

Cholesterol is deposited in various tissue because the high concentration of LDL cholesterol in the plasma

39
Q

Important cholesterol derivatives

A

Bile salts

steroids

Lipids (5 decks)

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