L3 - Lipids Flashcards
What are the 2 groups of lipids?
Triglycerides and phospholipids
How are triglycerides formed?
By the condensation of one molecule of glycerol and three molecules of fatty acid
What forms an ester bond?
A condensation reaction between glycerol and a fatty acid (RCOOH)
One water molecules is released per ester bond
What 2 forms can the R-group of a fatty acid be?
saturated or unsaturated
What happens in phospholipids?
In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group
What are triglycerides mainly used as?
As energy store molecules
What type of bond forms beteren glycerol and the fatty acid chains?
Ester bonds
How many molecules of water are released per 1 triglyceride bond?
3 molecules of water
What is the structure of fatty acids?
Long ‘tails’ made of a chain of hydrocarbon with 4-36 carbon atoms
(Most have 12-18)
Glycerol links to the central carbon atom on fatty acids
What are triglycerides function in energy release?
Chemical energy is stored in the fatty acid hydrocarbon tails
So lots of energy is released when triglycerides are broken down
How does the amount of energy contained in lipids compare to carbs?
Carbs contain half the amount of energy per gram lipids do
Why do triglycerides repel water?
They are insoluble in water because the fatty acid tails are hydrophobic
Meaning the cell’s water potential isn’t affected by triglycerides
If they didn’t repel water, water would enter the cell through osmosis causing the cell to swell up
Why do the insoluble triglycerides crowd together at droplets in cells?
Because the hydrophobic fatty acid tails face inwards
What do phospholipids do?
Form a bilayer which controls what comes in and out of the cell
What is the structure of phospholipids?
Composed of fatty acid chains attached to glycerol
Has 2 hydrophobic fatty acid tails and 1 hydrophilic phosphate group
Making it an amphipathic molecule
What do the hydrophobic tails of phospholipids do?
They can’t interact with water
In membranes, they face inwards in the bilayer
This means water-soluble substances can’t easily pass through the membrane
What does the hydrophilic head of phospholipids do?
It can interact with water
In membranes, it faces outwards
What is the structure of saturated fatty acids?
Carbon atoms have single bonds in between them in the hydrocarbon chain
The number of hydrogen atoms attached to the carbon skeleton is maximised
What are saturated fatty acids like at room temperature?
What are they also linked to?
Solid at room temp and usually of animal origin
Linked to increased risk of cardiovascular disease in humans
What foods contain a high proportion of saturated fat?
5
Cream Cheese Butter Other whole dairy products Fatty meats
What is the structure of unsaturated fatty acids?
Have one or more double bonds between carbon atoms in the hydrocarbon chain
What is an example of an unsaturated fat?
Cooking oils
What are unsaturated fats like at room temperature?
Double bonds ‘kink’ the carbon chain so unsaturated fats can’t pack tightly together
Causing them to remain liquid at room temperature
Is the phosphate head of phospholipids positively or negatively charged?
Negatively charged
What are the 3 main functions that lipids serve in plants and/or animals?
Storage of energy
A structural component of hormones
As signalling molecules
How do phospholipids contribute to cell membrane structure?
Phospholipids orient their heads towards the polar molecules and tails in the interior of the membrane, forming a bilayer
