Lipids Flashcards
Why is lipid important for health(2)
Energy during fasting
Energy during pregnancy
Lipids in disease (3)
Energy for host defence
Endocrine diseases associated
- cushings
- diabetes
Metabolic problems
- fatty liver
- hyperlipidemia
When does catabolism of lipids occur
Fasting
Demand for energy
What stimulates catabolism of lipids
Hormones stimulate lipases
Adrenaline
Glucagon
Cortisol
What is the type of fat in adipose tissues
Triglycerides
What happens to triglycerides in catabolism
Broken down to FA and glycerol
Released into blood
Travels to liver or muscles
What happens to FA at liver
Linked to CoA
Oxidised to acetyl CoA
Enters TCA
What happens if there is excess acetyl CoA
Converted to ketone bodies
Where does b-oxidation happen
Liver
Heart
Muscle
Mitochondria
Function of b-oxidation
To provide energy for metabolism as ATP
Substrate for b-oxidation
Long chain fatty acids
Palmitic acid
Or
Fatty acyl CoA
Products of b-oxidation
Co factors
NADH FADH
Ketone bodies
Or
Acetyl CoA
Control of b-oxidation
Whole level
Cellular level
Hormone control stimulate release of FA
Malonyl CoA controls enters of Fatty acyl CoA to mitochondria
What is fatty acid activation
When acyl CoA is formed
Where does fatty acid activation take place
Cytoplasm of cells
How many high energy bonds are involved in FA activation
2 high energy phospho bonds used
2 ATP
Produce high energy bonds
What type of bonds are formed in FA activation
Sulphur
What happens during FA activation
FA linked to CoA to form acyl CoA
What does the carnitine shuttle do
Transports the fatty acyl group to mitochondria
Describe. Shuttle
Outer membrane
- FA-CoA transfers FA to carnitine to produce
Fatty acyl carnitine enzyme
Inner membrane
- FA transferred back to CoA
What inhibits the carnitine shuttle
Malonyl CoA
Stops catabolism when have enough energy
What are the 4 steps of b-oxidation
- Dehydrogenase enzyme oxidises beta carbon
Fad reduced
- ATP and c=c form - Water and hydratase - hydrate double bond -OH
And H on C2 - Dehydrogenase with NAD remove hydrogen
= 3 ATP - Thiolase cleaves FA at C2 and C3
= fatty acyl CoA and acetyl CoA
What happens to the fatty acyl CoA after b-oxidation
Recycled but 2C less each time until only 4 carbon left
What is the product of b-oxidation of palmitic a acid (16C)
7 cycles - last cycle is 4C as 2 lost each time
7 FADH
7 NADH + H
131 ATP
What happens to unsaturated fatty acid b-oxidation
More c=c bonds
Other enzymes involved in oxidation
More energy used up
When does FA synthesis take place
When high energy
Where does FA synthesis take place
What part
Adipose
Mammary
Liver
Cytoplasm
What is substrate for FA synthesis
Where from
Acetyl CoA
Glycolysis
AA
How is acetyl CoA transported from mitochondria to cytoplasm for FA synthesis
Citrate shuttle
What is the product of FA synthesis
Palmitoyl CoA (16C)
What is the name of the multi enzyme complex in FA synthesis
Fatty acid synthase complex
What cofactors are involved in FA synthesis
NADPH + H
CoA
Provide energy
How does the citrate shuttle work
I. Mitochondria
Acetyl CoA To Oxalacetate To Citrate
In cytoplasm
= reverse
OAA back to mitochondria
What is produced WD in cytoplasm as by product of citrate shuttle
NADPH
What is the enzyme that is a control point in FA synthesis
Acetyl CoA carboxylase
What activates and what inhibits acetyl CoA carboxylase
Activated
- citrate (substrate)
- insulin
- CHO
Inhibited
- FA (product)
- glucagon
- fat
What is the first step of FA synthesis
Acetyl CoA
To
Malonyl CoA
By carboxylase adds carboxyl group
What is the fatty acid synthase complex
7 enzymes and acyl carrier protein
Where FA chain grows
ACP has active -SH which binds to growing FA chain
What does the acyl carrier protein do in FA synthesis
Transports FA growing chain from place to place
See sheet on steps and enzymes of FA synthesis
It’s complicated
What happens to produce FA
Elongated
Desaturated
Conjugated to triglycerides or phospholipid
Where are triglycerides synthesised the
ER
Source of glycerol
From liver
What happens to triglycerides
Go to VLDL for export to blood
What happens in adipose tissue to form triglycerides
Glucose enters tissue
Control of triglycerides
Whole body
Cellular
Only occurs when excess glucose
Insulin
Cellular
Acetyl CoA carboxylase
What does insulin stimulate in term of FA synthesis
Activates acetyl CoA carboxylase
Activates lipoprotein lipase in adipose tissue increasing TG break down in VLDL and transfer of FA to adipose
Functions of lipids (5)
Metabolism
Hormones
Structural
Electron transport
Antioxidants
