Lipids Flashcards
What are lipids?
A group pf substances that are soluble in alcohol rather than water. They include triglycerides, phospholipids, glycolipids and cholesterol
What are phospholipids?
Molecule consisting of glycerol, 2 fatty acids, and 1 phosphate group
what is a property of lipids?
They are insoluble in water because they are non-polar and therefore they are not attracted to the water
What are the three most important lipids?
Triglycerides
Phospholipids
Steriods
None of them are polymers. they are different compounds bonded together. They are example of Macromolecules
Describe the structure of triglyceride
Glycerol and fatty acids.
Glycerol: 3 carbon atoms. It’s an alcohol, therefore, contains free -OH groups. There are 3 -OH groups in triglycerides
Fatty acid: many types. Those we cannot make and most be ingested are called “essential fatty acids”
Describe the fatty acids in triglycerides
Carboxyl group (-cooh) on one end, attached to a hydrocarbon tail, made of only carbon and hydrogen atoms 2-20 carbons long Carboxyl group ionises into H+ and a -COO- group. Therefore it is an acid because it produces free H+ ions
Give inofrmation about saturated and unsaturated fatty acids
If saturated there are no double-double carbon bonds (C=C)
If unsaturated there is a double-double carbon bond, which means that fewer H-atoms can ee bonded to the molecule
Single C=C bond — monounsaturated fatty acid
More than 1 C=C bond — polyunsaturated fatty acid
unsaturated fatty acid have a different shape because where the C+C bond is the chain kinks changing the hydrocarbon chain
Kink pushes molecules apart = more fluid
More unsaturated fatty acid = lower melting point
Animal lipids = solid at room temperature (20o) - saturated
What bond forms in lipids?
The covalent bond is called ester bonds
Talk about the formation of ester bonds
Condensation reaction happens between the -COOH group pf the fatty acid and the -OH group of the glycerol
Covalent bond formed= ester bond
What are the functions of triglycerides?
Energy source: they can be broken down in respiration to release energy and generate ATP.
Energy store: Because they are insoluble in water they can be stored without affecting the water potential in the cells.
Insulation: Adipose tissue is a storage location for lipids in whales, acting as a heat insulator. Lipids in nerve cells act as an electrical insulator. Animals preparing for hibernation store extra fat.
Buoyancy: Because fat is less dense than water, it is used by aquatic mammals to help them stay afloat
Protection: Humans have fat around delicate organs, such as their kidneys, to act as a shock absorber. The peptidoglycan cell wall of bacteria is covered in a lipid-rich outer coat.
What is the first step to break down triglycerides in respiration to release energy and generate ATP.
The first step is to hydrolyse the ester bond, and then both glycerol and the fatty acids can be broken down completely to carbon dioxide and water. Respiration of a lipid produces more water than respiration of a sugar.
What is the structure of phospholipids?
1 glycerol molecule
2 fatty acid groups
1 phosphate group
What occurs in a condensation reaction between two phospholipids?
A condensation reaction between an -OH group on a phosphoric acid molecule(H3PO4) and one of the 3 -OH group of the glycerol forms an ester bond. Water is removed, leaving a linkage of an oxygen atom
what is the behaviour of phospholipids in water?
When surrounded by water, phosphate group = negative therefore it is polar (attracted to water)
Fatty acid tail = non-polar therefore repels water
Phosphate group - hydrophobic (head)
Fatty acid - hydrophobic (tail phospholipids molecules are amphipathic
What does the phosphate group look like?
Has oxygen, phosphorus (P) and hydrogen
What does the fatty acid look like in phospholipids?
Chain with a double oxygen bond to a carbon with 2 hydrogen bonds.
Often even numbers of carbon atoms
Often 1 chain is saturated and the other is non-saturated
Give information about phospholipids which are amphipathic:
Form a layer on the surface of the water - heads in water, tails sticking out
May also form micelles - tiny balls with tails tucked inside and the heads out
What is the phospholipid bilayer?
2 rows of phospholipid: tail inwards. head outwards
Individual phospholipids are free to move around in their layer, but will not move into a position where the hydrophobic tail is touching the water. This gives the membrane some stability.
The membrane is selectively permeable - only small and non-polar molecules can move through the tail in the bilayer (e.g. Oxygen, CO2)
Controls what goes in and out of the cell and keeps it functioning properly
Give information about cholesterol
Its a steroid alcohol - a type of lipid not made up of glycerol or fatty acid
Has 4 carbon-bond rings
Small and hydrophobic molecules - it can sit in the middle of the hydrophobic part of the bilayer
Regulates fluidity of the membrane - not to fluid or stiff
Many are made in the liver of animals
Plants also have a cholesterol derivative in their membrane called stigmasterol - different because it has a double bond between C-22 and C-23
Give examples of steroid hormones
Testosterone
Oestrogen
Vitamin D
All made of cholesterol
