Lipids Flashcards
Where are lipids generally found? (3)
Cell membranes
Lipid droplets in adipose
Lipoproteins in blood
Aside from their use in energy storage and membranes, what are lipids used for in the body? (4)
Enzyme cofactors
Hormons
Vitamins
Signalling molecules
What are the 5 classes of lipid?
Phospholipids Triacylglycerols Free fatty acids Glycolipids Steroids
A fatty acid with a 17:3 in the name means what?
17 carbons
3 double bonds
True or false
In omega acids, the double bond is counted from the carboxyl end of the molecule?
False
Normal convention is to count from the Coo- end but omega acids are counted from the methyl end
Why must we obtain linoleic and linolenic acids from plants?
Essential fatty acid
Can not synthesise it
Why are we unable to make essential fatty acids?
Humans cannot introduce double bonds beyond carbon 9
What problems are caused by fatty acid deficiency?
GRSKVDA
Growth retardation Reproductive failure Skin lesions Kidney/Liver disorder Visual problems Depression (Omega 3) ADHD (Omega 3)
What are the main uses of triacyglycerols?
Energy
Insulation
(TAG’s are the main lipid type in stored fat)
Where are triacylglycerols stored?
Adipose tissue
Describe the basic structure of phospholipids.
Glycerol
2 FA
Phosphate
What is the main dietary lipid type?
Triacylglycerols
What is the main site of digestion of lipids?
Small intestine
What molecules are used to digest lipids in the small intestine?
Pancreatic lipases
+ bile salts
Where are bile salts produced and what are they derivatives of?
Gallbladder
Cholesterol
What do bile salts do?
Emulsify lipids into smaller droplets
What is produced when Triacylglycerols are broken down in the small intestine?
2 FA
1 Monoacylglycerol
Phospholipids are broken down into what?
in small intestine
1 FA
1 Lysophospholipid
Bile salts combine with the products of digestion of lipids to form?
Micelles
Why do micelles only contain long chain fatty acids and not short/medium chain?
Short chain FA can diffuse through membrane directly
What is Steatorrhea?
Inadequate lipid absorption
Defects in bile secretion, pancreatic function, intestinal cell uptake
What happens to the products of digestion after they cross into epithelial cells? (4)
Re-synthesised
Made into chylomicrons
Exocytosis into lymph
Movement into blood
What is the purpose of apoB-48?
Solubilising protein
Describe how the triacyglycerols are transported into tissues.
Chylomicrons broken down into FA + glycerol in capillaries by lipoprotein lipases
These are found mostly in capillaries of skeletal muscle and adipose tissue
Chylomicron remnants transported to liver
What are the Fatty acids and glycerol molecules (produced when chylomicrons are broken down) used for?
FA used for energy (skeletal muscle) or resynthesised to make TAG for storage (adipose)
Glycerol is used by liver to make G-3-P (glycolysis & gluconeogenesis)
Where is triacylglycerol stored?
Adipose cells/tissue
What does Hormone sensitive lipase (HSL) do?
Release stored TAG in adipose cells
What transmitter is used to trigger Hormone sensitive lipase to start working?
Adrenaline (epinephrine)
What is the difference in how fatty acids and triacylglycerols are transported in the blood?
FA’s - serum albumin
TAG’s - lipoproteins
Why are lipoproteins needed?
TAGs and cholesterol esters are insoluble in water
Cannot travel in blood/lymph
True or false
Chylomicrons are examples of lipoproteins
True
What are the 4 types of Lipoproteins?
Chylomicron
VLDL (Very low density lipoprotein)
LDL
HDL
What problems are associated with too much LDL?
Atherosclerosis
Where do VLDLs transport TAGs to and from?
Liver to tissues
What do LDL’s transport?
Mainly cholesterol
Release in extra-hepatic tissues
What is the function of HDLs?
Transport cholesterol from tissues to liver to be eliminated
What is Beta oxidation?
Degradation of fatty acids, 2 carbons at a time
Produces Acetyl CoA + NADH + FADH2
Where does Beta oxidation occur?
Mitochondrial matrix
What are the 3 stages of Beta oxidation?
Activation
Transport
Degradation
What happens in the activation stage of beta oxidation?
Fatty acids activated to form fatty acyl CoA
In cytoplasm
Describe the transport stage of beta oxidation.
Carnitine shuttle
Fatty acyl CoA moves across outer mitochondrial membrane
CoA group removed, Carnitine group added
Fatty acyl Carnitine moves across inner membrane
Carnitine removed, CoA added forming Fatty acyl CoA
What is the enzyme used to for adding/removing the Carnitine /CoA groups in the transport stage of Beta oxidation?
Carnitine palmitoyl-transferase
1 + 2
Why does therapy for CAT-1 deficiency include giving medium chain Fatty acids?
Carntine shuttle used for long chain FA
Medium chain FA can pass into mitochondria without shuttle
Patient can carry out Beta Oxidation
There are 4 steps in the degradation stage of Beta oxidation, what are they?
Dehydrogenation - produce FADH2
Hydration
Dehydrogenation - produce NADH
Thiolysis - cleavage to produce Acetyl CoA
What is the Acetyle CoA produced by thiolysis used for?
Feeds into the citric acid cycle
What would be the product of complete beta oxidation of a 18:0 Fatty acid?
18 carbons
Each cycle produces 1 Acetyl CoA and a FA that is 2 C’s shorter
00-00-00-00-00-00-00-00-00
8 ‘splits of -‘ are needed
8 NADH + 8 FADH2 + 9 Acetyl CoA
What are peroxisomes used for?
Partial B-oxidation of >22 carbon FA chains
These could not originally pass into Mitochondria via C shuttle but can after leaving peroxisome
Why does Acetyl CoA not used in gluconeogenesis?
Thermodynamically impossible to convert Acetyl CoA to pyruvate
(only the opposite)
What does the body convert Acetyl CoA into during starvation?
Ketone bodies
Describe why ketone bodies are used?
Starving: glucose decreased
Excess Acetyl Coa from metabolism of FA converted to Ketone bodies
Supplies Cardiac + skeletal muscles + brain cells
Why must Fatty acids be converted to ketone bodies to supply the brain with energy?
Brain cannot use FA as fuel source
Brain needs a fuck ton of energy
Where are ketone bodies produced?
organelle + organ
Mitochondrial matrix of cells in the liver
True or false
The liver manufactures ketone bodies, but can not use them itself
True
A stranger in the street collapses in a manner similar to extreme drunked-ness
You approach to help but notice a strong fruity odour
The stranger is a diabetic
What is wrong with the stranger?
Diabetes leads to high ketone concentrations in blood
Ketonemia (blood) + Ketonuria (urine) + Acidemia (acidic blood)
Fruity odour due to Acetone
Where does Fatty acid synthesis take place? (3)
Liver
Lactating mammary gland
Adipose tissue
What organic molecule are fatty acids synthesized from in lipogenesis?
Acetyle CoA
What is used to provide energy for making FA’s in lipogenesis?
(2)
ATP
NADPH
Why is NADH not used in fatty acid synthesis?
NADH is used in FA degredation
Where does fatty acid synthesis take place?
Cytosol
liver, mammary gland, adipose
Where is acetyl CoA produced?
Mitochondria
How is Acetyle CoA moved to the cytosol?
Acetyle CoA reacted with oxaloacetate to make citrate
Citrate passes through membrane
Reverse reaction done so oxaloacetate + Acetyle CoA made on cytosol side
- ULTRA BASIC -
A.CoA turned to citrate, goes through and is turned back into A.CoA
Why is Acetyl CoA carboxylase a key enzyme in fatty acid synthesis?
Forms malonyl-CoA
Committed step in pathway
You have 32 molecules of Acetyl CoA, how many molecules of palmatite can you obtain from fatty acid synthesis?
4
8 A.CoA : 1 Palmatite
How many molecules of ATP and NADPH are used to produce 4 molecules of palmatite?
56 NADPH - 28 ATP
each palmatite requires 14 NADPH’s and 7 ATP’s to make
True or false
Steroids and Eicosanoids are both derived from cholesterol
False
Steroids are derived from cholesterol
Eicosanoids are derived from omega 3 and 6
What is cholesterol derived from?
Acetyl CoA
How do statins reduce cholesterol levels?
Inhibit enzyme needed in cholesterol synthesis
Lower LDL levels
What vitamins are derived from lipids?
A, D, E, K
What is beta oxidation?
Catabolism of Fatty acids to generate NADH, FADH2 and Acetyl CoA
What are the possible fates of Acetyl CoA, produced from Beta oxidation?
1) Feed into CAC
2) Ketogenesis
3) Lipogenesis (reverse)
Why does ketogenesis occur?
Fasting/starvation
Low blood glucose means energy is needed
Fatty acids are not gluconeogenic so can not make glucose, so are converted to ketone bodies which can be used as an energy source that isn’t glucose
What tissues can use ketone bodies as a fuel source?
Cardiac and skeletal muscle
The brain - this can’t use FA as an energy source
Where does ketogenesis take place
Liver
But the liver can’t use ketone bodies as an energy source
