Lipids Flashcards
(32 cards)
What is a lipid?
A molecule made up of carbon, hydrogen and oxygen. It will always contain 2 fatty acids and a glycerol.
Why are lipids not polymers?
There are not made up of similar repeating units.
Do carbohydrates or lipids release more energy when oxidised?
Lipids
Do carbohydrates or lipids contain contain more oxygen atoms?
Lipids.
What elements are lipids made up of?
Carbon, hydrogen and oxygen.
What is a triglyceride?
A lipid made up of three fatty acids bonded to one glycerol molecule by ester bonds.
What is a phospholipid?
A lipid made up of 2 fatty acids and a phosphate group joined to a glycerol molecule by ester bonds.
What are the structural differences between triglycerides and phospholipids?
Triglycerides have 3 fatty acids whereas phospholipids only have two fatty acids (1 is replaced by a phosphate group)
What is the bond between the fatty acid and glycerol molecule called?
Ester bond.
What part of the fatty acid bonds to the glycerol?
The carboxylic acid group.
Explain the reaction which produces a triglyceride.
The three fatty acids are joined to the glycerol via a condensation reaction.
The fatty acids’ carboxylic groups lose a hydrogen and and the glycerol loses 3 hydroxyl molecules.
Three ester bonds are formed (one for each fatty acid) between the glycerol’s carbon and the fatty acids carbon.
3 water molecules are eliminated in the process.
Why are lipids insoluble in water?
They are non-polar.
What are lipids soluble in?
Organic solvents. E.g., alcohol.
What function does insoluble in water link to?
Makes them good storage molecules as they are osmotically inactive.
What is a beneficial quality of lipid bonds?
Ester bonds are very high energy bonds so when broken they release lots more energy than carbohydrates.
How do lipids protect organs in animals?
They act as a heat insulator, thus help the animal retain body heat.
What is the function of triglycerides?
Storage molecule.
What is a function of phospholipids?
Used to form a cell membranes in plants and animals.
How do animals lubricate their skin?
They produce an oily secretion from the sebaceous glands to lubricate the skin.
Does a condensation or hydrolysis reaction produce water?
Condensation reaction.
What is the difference between saturated and poly-unsaturated?
Saturated molecules do not contain any double bonds between two carbons whereas poly-unsaturated molecules contain 2 or more.
What are fatty acids called when they contain one carbon to carbon double bond?
Mono-unsaturated.
Give 8 properties of triglycerides.
Non-polar.
Insoluble in water.
Soluble in organic solvents.
Have high energy bonds.
Low mass to energy ratio.
High ratio of C-H bonds to C atoms.
High ratio of H:O atoms.
Release water when oxidised.
What functions do triglycerides have due to these properties?
They are good storage molecules as: they store lots of energy per molecule; they are insoluble so do not affect the osmotic potential of the cell.
They are an important source of (metabolic) water as they release water when oxidised.
