Lipids Flashcards
what are lipids?
Lipids are a diverse group of organic compounds which are insoluble in water. Lipids include the fats and the oils,fats are solid oils are liquid.
what elements are present in lipids?
carbon
hydrogen
oxygen
What are the three categories of lipids?
Triglycerides
Phospholipids
Steroids (cholesterol)
what is a macromolecule?
a molecule containing a very large number of atoms ( e.g lipids and proteins)
What is the basic structure of a triglyceride?
Made up of one glycerol molecule bonded to three fatty acid tails.
(monoglyceride have one glycerol head diglyceride have two ect..)
What is the glycerol head?
Chemical formula: C3H8O3
each of the carbons have an -OH group attached
What are fatty acids?
have the general formula: CH3 (CH2)n COOH
acids because they contain the carboxyl group (dissociates in water)
The rest is the hydrocarbon chain that varies between fatty acids and can vary with number of carbons or if they are saturated or unsaturated.
Craboxyl end is polar the hydrocarbon chain is not polar.
Difference between saturated and unsaturated fatty acids/triglycerides
saturated chains form straight chains whereas unsaturated form kinked chains where the double bond is.
How are triglycerides formed?
Glycerol and fatty acids joined by a condensation reaction between the hydroxyl group of the glycerol and the carboxyl group of a fatty acid
The bond is called an ester bond formed by the process of esterification.
How are triglycerides broken?
Ester bond can be broken by hydrolysis to from the fatty acids and glycerol.
Difference between fats and oils.
FATS= saturated hydrocarbons so can pack tightly together so solid at room temperature. OILS= unsaturated so form kinks and cant pack closely together so are liquids at room temperature.
Behaviour of lipids in water and organic substances.
Does not dissolve in water as the hydrocarbon chain is exposed and is not polar.
Will dissolve in organic solvents.
What is the basic structure of phospholipids?
Similar to that of a triglyceride but hey have a phosphate group in place of one of the fatty acid tails.
What is the property of each part of a phospholipid?
The phosphate group is charged so therefore polar so the phospholipid has a hydrophillic head
The tails are hydrophobic - so a hydrophobic head
This makes them amphipatic.
Difference between triglyceride and phospholipid.
triglyceride- 3 fatty acid tails attatched to one glycerol
phospholipid- 2 fatty acid tails and one phosphate group attatched to a glycerol. Also have the addition of phosphorus the element and the charged group.
What are glycolipids?
similar to phospholipids but rather than the phosphate group there is a carbohydrate group and are also amphipatic.
What is the structure of steroids?
4 connected organic rings with a variety of side groups
What happens to the side groups of cholesterol?
altering the side groups releases hormones such as testosterone or oestrogen.
How many water molecules are released in the formation of a triglyceride?
3
Functions of triglycerides
source of energy when respired
thermal insulation - blubber in whales
electrical insulation - myelin sheath
Waterproofing
Functions of phospholipids
membrane structure
Function of cholesterol
membrane structure
hormones (e.g oestrogen)
How do phospholipids form a membrane?
arranged in a bilayer in accordance to their hydrophobic and phydrophilic groups
hydrophobic tails in the middle away from the environment and hydrophilic heads next to the aqueous environment.
How does the presence of cholesterol affect the properties of cell membranes?
helps immobilise and make the surface of the membrane less soluble to very small water soluble molecules without cholesterol cell membranes would be too permeable to some molecules.
