T3 L5: Introduction to lipids Flashcards
What are 3 examples of labile energy stores?
ATP (in the phosphate groups), Redox agents (NADH, FADH2) and ionic transmembrane gradients
What is creatine phophate?
An energy store in muscles
Give 2 examples of large and stable energy stores
Carbohydraes and fats
What is the importance of acetyl-CoA in energy production?
Its an energy mediator used to begin the Krebs cycle by oxidising citric acid
What molecule is cholesterol produced from?
Acetyl-CoA
What organ absorbs glycogen?
The liver
What are ketone bodies and what is their function?
They are produced by the liver from fatty acids during a low-carbohydrate diet, fasting or too much alcohol. They are alternatives to ATP
During ketosis, where will high levels of ketones be present?
In the urine and blood but not enough to cause acidosis
Why does the brain need a constant supply of ketone bodies and glucose from plasma?
There is no glycogen in the brain
What does fatty acid synthesis lead to?
A fatty acid with an even number of carbons. The process requires ATP
What is the structure of a fatty acid?
A straight carbon chain with a COOH group
What are essential fatty acids?
Those that must be in the diet because they can’t be produced
What is an ester bond?
A glycocidic bond but in fatty acid
What 4 types of molecules is cholesterol a precursor for?
Bile acids, steroids, hormones and vitamin D
What are the sources of cholesterol?
From the diet or can be made by the liver
When is cholesterol amphipathic?
When it’s free
When is cholesterol hydrophobic?
When its esterified (because there is nothing to interact with water as the OH is gone)
When are ketone bodies produced by the body?
During fasting (after all fat and glucagon is used up)
What are ketone bodies produced from?
Acetyl-coA
Give 3 examples of ketone bodies
Acetoacetate, beta-hydroxybutyrate and acetone (the waste product)
Why do unsaturated fatty acids have a lower melting point?
They have an irregular structure compared to saturated fatty acids so their intermolecular forces are weaker
What type of optical isomerism do most unsaturated fatty acids have? Cis or Trans?
Cis
Why are trans unsaturated fats bad?
They increase levels of LDL
What are the 4 pathways of lipid transport?
- Exogenous pathways - Gut to liver and periphery (muscle and adipose tissue)
- Endogenous pathway - Liver to periphery
- Recycled pathway - Periphery to liver
- In the form of bile acid - Liver to digestive tract
Describe the exogenous pathway (from gut to liver and periphery) of lipid transport
Lipids from diet are packaged by the small intestine into chylomicrons which are taken up by the liver and periphery
What is meant by exogenous?
From the outside
Describe the endogenous pathway (from liver to periphery) of lipid transport
Lipids from the liver are packaged into VLDL and then stored in the periphery
What is meant by endogenous?
Made by the body
Describe the recycling pathways (from periphery to liver) of lipid transport
It occurs when the lipid supplies in the liver are being exhausted during starvation or exercise. HDL transports the lipids back to the liver so they can be converted back into energy
What are chylomicrins?
Molecules that transport triglycerides
Describe the bile production pathway of lipid transport
Cholesterol is converted into bile acids and released into the cystic duct. Most of the bile acids are reabsorbed by the gut and returned to liver and recycled
What is the function of lipoprotein lipase?
It metabolises triglycerides into fatty acids and glycerol to remove the triglycerides from VLDL and then moves them across the capillary membrane. This happens because triglycerides cannot go through cell membranes
What are apolipoproteins?
Proteins in lipoprotein molecules that can hold lipids . They’re amphipathic so it can bind to the protein and to the lipid at the same time
How dense is cholesterol compared to tryglycerides and proteins?
Between triglycerides and proteins
Why are bigger lipoproteins lower in density?
Because they are carrying more proteins
Why are LDL dangerous?
Because they are incorperated into atheromas. In the blood, it’s storage for cholesterol that can’t be stored anywhere else. It’s what is left over once the periphery has absorbed endogenous triglycerides from VLDL from the liver
Why is HDL better than LDL?
Because HDL lowers cardiovascular risk. It carries lipids from fat cells to the liver when cholesterol is being used up
Which type of lipid signifies a risk of atheroma?
VLDL
What is VLDL used for?
Used to transport endogenous cholesterol and triglycerides from the liver to the periphery
What is IDL?
Intermediate density lipoprotein. It’s the intermediate molecule before VLDL becomes LDL
What do the beta cells of the pancreas produce?
Insulin
What do the alpha cells of the pancreas produce?
Glucagon
What does hypercholesterolaemia increase the risk of?
Arteriosclerosis
What is the function of statins?
They block endogenous cholesterol synthesis by blocking HMG-CoA Reductase
What is simvastatin prescribed for?
For cardiovascular disease prophylaxis especially for men over 50
What is metabolic syndrome?
Its a group of risk factors that increase the risk of cardiovascular disease, stroke and type 2 diabetes
