Flashcards in Lipids Deck (54):
What are Lipids?
Heterogeneous organic molecules that are hydrophobic (remember they can still be soluble in organic solvents)
What are the basic functions of Lipids?
1. Storage of energy
2.Structure in membranes (P.Lipids)
4. Hormone functions
5. Vitamins (A,D,E,K)
6. Signalling molecules
What are the five classes of lipids?
1. Fatty Acids
2. Triglyceride (TAG)
Is an unsaturated fatty acid liquid or solid?
What are the essential fatty acids?
Linoleic and Alpha-Linolenic
What is the structure of Triglyceride (TAG)?
Esters of fatty acids and glycerol
Why does TAG coalesce into lipid droplets in adipose tissue?
They are water insoluable
Use of TAG?
Dietary fuel and insulation (TAG is main dietary lipid)
What is the structure of phospholipds?
Glycerol bonded to 2 fatty acids and a phosphate group
Where is the main site of digestion of TAG?
What are lipids digested by?
Pancreatic enzymes called lipases
How is digestion made easier?
Emulsification and peristalsis using bile salts
What does bile salts do to aid digestion of TAG?
Forms mixed micelles and emulsions, spreading lipids out for maximum digestion and stopping them coalescing/collecting together in aqueous solutions.
What are bile salts derived from?
What do pancreatic lipases break TAG down into?
Monoacylglycerol and 2 fatty acids
What does a phospholipid break down into?
Fatty acids and a lysophospholipid
What happens to large lipid products once broken down?
Large fatty acid chains form mixed micelles with bile salts and are released onto the micro-villi/brush border entering by diffusion.
What happens to medium lipid chain products after digestion?
Absorbed into micro-villi/brush border without mixed micelles
Structure of fatty acids?
Hydrocarbon chain with a carboxylic group at one end
Are phospholipids amphipathic?
What does amphipathic mean?
Having both hydrophilic and hydrophobic parts
What are cholesterol esters broken down into during lipid digestion?
Cholesterol and a free fatty acid
Once lipid products reach intestinal cells, what happens to them?
They are repackaged into original lipid (TAG cholesterol ester, fatty acids) and packaged into chlyomicrons for transport through blood and lymph via lymphatic system.
When chylomicrons reach tissues, what occurs?
TAG is hydrolysed to free fatty acids and glycerol by lipoprotein lipase.
Once chylomicrons reach tissue and TAG being hydrolysed, what happens to products?
Fatty acids are used for energy or re-esterified to TAG.
How are free fatty acids transported around the body?
Transported using a lipoprotein in complex with serum albumin.
What do Low Density Lipoproteins (LDL) do?
Carry cholesterol from the liver to other tissues, which is bad
What do High Density Lipoproteins (HDL) do?
Collect cholesterol from tissues and take it to liver for elimination (good)
What does Beta Oxidation do?
Breaks down fatty acids 2 carbons per cycle
What does beta oxidation form?
Acetyl CoA, NADH and FADH2
Where does beta oxidation occur?
What are the 3 stages of beta oxidation?
In activation stage if beta oxidation, what is activated and where?
Fatty acids are activated to form long chain fatty acyl CoA in the cytoplasm
In the transport stage of beta oxidation, what transports acyl CoA from cytoplasm to mitochondrial matrix?
What is carnitine?
Non Essential amino acid
What does malonyl CoA do?
Inhibits Carnitine fatty-acyl transferase, which is crucial in fatty acid degradation/beta oxidation. (Malonyl does this to let fatty acid synthsis occur and stop degredation)
What is the significance of the fact malonyl CoA inhibits Carnitine fatty-acyl transferase?
It means synthesis and degradation of fatty acids can't happen simultaneously
What are the stages of degradation step in beta oxidation?
1. Fatty acyl CoA is DEHYDROGENATED to form FADH2 and an intermediate.
2. Intermediate is HYDRATED
3. Hydrated intermediate is DEHYDROGENATED to from NADH
4. Thiolysis occurs forming Acetyl CoA which feeds into the Citric Acid Cycle.
Process repeats till the Fatty acyl coA is depleted of carbons, as this only removes 2 carbons at a time.
Are fatty acids gluconeogenic (Can glucose be synthesized from them) ?
When are ketone bodies formed?
During fasting or starvation when glucose levels run low
What are ketone bodies made from?
Excess acetyl CoA from fat metabolism
What uses ketone bodies?
Cardiac and Skeletal muscles, and brain cells in times of starvation.
What does high ketone levels result in?
Ketonemia and Ketouria and acetone from breath
Where are ketone bodeis made?
In liver, acetone is also made but removed from expiration, hence acetone breath
In diabetes, why does the patient have high levels of ketone bodies?
Body can't use glucose as fuel as no insulin, making oxaloacetate levels drop which causes CAC to slow maeing Acetyl CoA can't be processed after beta oxidation, so is used to make ketone bodies instead.
Where does fatty acid synthesis occur?
Cytosol of liver
What does fatty acid synthesis use?
Acetyl CoA derived from excess protein fat and carbs
Acetyl coA transported from mitochondria to cytosol for fatty acid synthsis using what?
Malonyl CoA is needed for fatty acid synthsis - why?
To inhibit carnitine fatty acyl transferase, thus inhibiting degradation of fatty acids.
What controls the formation of malonyl CoA?
Acetyl CoA Carboxylase - is a regulatory enzyme.
Functions of cholesterol?
Precursor for steroids and are components of cell membrane
What are Eicosanoids derived from?
20 carbon Omega3/6 fatty acids
What are Eicosanoids the precursors for?