12-03: Lipids
Lipids
Made of mostly Carbon and Hydrogen with a few Oxygen
Though they are the same elements as carbohydrates, they’re different because there are way fewer Oxygens - there is no more 1:2:1 ratio customary of carbohydrates
Primarily composed of non polar bonds formed between C and H
Hydrophobic molecules: they repel/”hate” water
Few polar O-H bond and more non polar C-H bonds (which share electrons equally)
The more C-H bonds they have, the more non polar they are
Used for long term energy storage, membranes, and dissolving of fat soluble vitamins (ADEK)
Four groups:
Fats
Phospholipids
Steroids
Waxes
Fats
Also known as triglycerides (or triacylglycerols)
Made up of 1 glycerol molecule and 3 fatty acids chains
Lots of chemical potential energy stored in these bonds – 38 kJ/g (9cal/g)
More than twice the energy of carbohydrates
Excess (any kind of food but namely carbohydrate) consumption is converted into fat though the body can store some in glycogen
Glycerol
Component of triglycerides
Also called glycerine
3 carbon molecule with 3 hydroxyls
It is a polyol or sugar alcohol
Fatty Acids
Long chains of carbons bonded to hydrogens with a carboxyl group at one end
Usually start counting carbons from the carboxyl end
Longer chains are less soluble
Usually even numbered, usually 16 or 18 carbons in length (with some exceptions)
We can draw fatty acids in 3 ways
Structural
Condensed
Skeletal - Line angle diagram
Saturated Fatty Acids
Has no C=C double bonds between Carbons – there are as many Hydrogens bonded to Carbons as possible
Animal fats (e.g. butter made from animal (cow) milk) - higher proportion of of saturated fatty acids in their triglycerides
Solids at room temperature: the fatty acids can pack tighter together which makes them denser
When we have fats that have a high proportion of saturated fatty acids, they are linear and can pack more tightly close together and can therefore maintain a fixed shape
They have higher melting points
Structure of a saturated fatty acid:
Unsaturated Fatty Acids
Has at least 1 C=C double bond
Plant oils - higher proportion of unsaturated fatty acids in their triglycerides
Liquid at room temperature: the fatty acids are bent (at the C=C bonds) and therefore cannot pack very tightly, making them less dense
Can be monounsaturated (1 Carbon double bond) or polyunsaturated (more than 1 Carbon double bond)
Structure of an unsaturated fatty acid
Hydrogenation
Hydrogenation: the process that turns plant oils into semi solids (e.g. margarine or vegetable shortening)
Decrease the number of C=C bonds
They add hydrogen to the unsaturated fatty acids to partially saturate them. They don’t do this to all of the C=C bonds, but enough for it to become a semi-solid
Used to improve the shelf-life and appearance of foods
The product doesn’t finish off being fully saturated – there aren’t enough H’s added to fully saturate the product, it becomes partially saturated
Trans fats
Side effect of hydrogenation
H’s placement creates a trans fat when it is on the opposite side
Hydrogen bonds on opposite sides of the chain of C=C bonds
Cis fats have both H’s on the same side
Putting it all together – triglycerides
Fats: triglycerides that are made of glycerol and 3 fatty acids linked by ester bonds to 1 glycerol molecule
Dehydration Synthesis:
3 waters produced because we have 3 linkages (and water is a product in dehydration synthesis which causes these linkages)
These are all saturated fatty acids in the triglyceride molecule formed above – they can be any kind of fatty acids and can also be a mix of different fatty acids
Fatty acid chains can be all the same, all different, or any combination
Be sure to draw them in the same format/represent them in the same way
Triglycerides are non polar
Phospholipids
These are in cell membranes – phospholipid bilayer
Phospholipids: similar to triglycerides, however 1 of the fatty acids is replaced with a phosphate group and a choline group
Phospholipid layers
Since it has a polar head and non polar tail, one end is hydrophilic (loves water): the heads and one end is hydrophobic (hates water): the tails
Heads are polar so they will be attracted to the water - tails will orient themselves with the oil to get away from the water
They make up most of the cell membrane 2 fatty acids (hydrophobic), glycerol, phosphate and choline (which are charged and therefore they're hydrophilic)
Liposome - 2 layers of phospholipids because there's an aqueous environment on interior & exterior which therefore attracts the heads
This is a bilayer sheet - the building blocks of the liposome
Micelle - single layer of phospholipids - tails on the inside and heads on the outside
Makes the soap bubbles or micellar water
Micelles in the water (little bubbles in solution)
Putting on the cotton swab - opens the micelle and then the tails face outwards and attract grease/makeup - heads are all attracted to the cotton
Steroids (Sterols)
Steroids: made of 4 fused hydrocarbons rings with a variety of side chain functional groups
Group of lipid molecules
Basic structure
Examples:
Cholesterol – needed for cell membranes
Sex hormones – estrogen and testosterone, secreted to do something, chemical messengers
Waxes
Waxes: fatty acids linked to alcohols (ester)
Fatty acids have carboxyl, alcohols have hydroxyl
Large molecules, no lipids form polymers
Examples
Cutin: water resistant covering made by epidermal cells of plants, conserves water and is a barrier against infection for the plants
Evergreen trees/pine trees – waxes around pine needles to thrive through the winter (evergreens do photosynthesis through the winter because they have enough water, water gets in through the roots)
Beeswax: structure for beehives
Earwax: a water repellent that protects the delicate ears
Where do lipids come from?
Made by the smooth endoplasmic reticulum within the cell
Able to protect the lipids from the cytoplasmic environment (filled with water)
It will then package the lipids into vesicles to be shipped to where they are needed in & out of the cell
Lipids
Made of mostly Carbon and Hydrogen with a few Oxygen
Though they are the same elements as carbohydrates, they’re different because there are way fewer Oxygens - there is no more 1:2:1 ratio customary of carbohydrates
Primarily composed of non polar bonds formed between C and H
Hydrophobic molecules: they repel/”hate” water
Few polar O-H bond and more non polar C-H bonds (which share electrons equally)
The more C-H bonds they have, the more non polar they are
Used for long term energy storage, membranes, and dissolving of fat soluble vitamins (ADEK)
Four groups:
Fats
Phospholipids
Steroids
Waxes
Fats
Also known as triglycerides (or triacylglycerols)
Made up of 1 glycerol molecule and 3 fatty acids chains
Lots of chemical potential energy stored in these bonds – 38 kJ/g (9cal/g)
More than twice the energy of carbohydrates
Excess (any kind of food but namely carbohydrate) consumption is converted into fat though the body can store some in glycogen
Glycerol
Component of triglycerides
Also called glycerine
3 carbon molecule with 3 hydroxyls
It is a polyol or sugar alcohol
Fatty Acids
Long chains of carbons bonded to hydrogens with a carboxyl group at one end
Usually start counting carbons from the carboxyl end
Longer chains are less soluble
Usually even numbered, usually 16 or 18 carbons in length (with some exceptions)
We can draw fatty acids in 3 ways
Structural
Condensed
Skeletal - Line angle diagram
Saturated Fatty Acids
Has no C=C double bonds between Carbons – there are as many Hydrogens bonded to Carbons as possible
Animal fats (e.g. butter made from animal (cow) milk) - higher proportion of of saturated fatty acids in their triglycerides
Solids at room temperature: the fatty acids can pack tighter together which makes them denser
When we have fats that have a high proportion of saturated fatty acids, they are linear and can pack more tightly close together and can therefore maintain a fixed shape
They have higher melting points
Structure of a saturated fatty acid:
Unsaturated Fatty Acids
Has at least 1 C=C double bond
Plant oils - higher proportion of unsaturated fatty acids in their triglycerides
Liquid at room temperature: the fatty acids are bent (at the C=C bonds) and therefore cannot pack very tightly, making them less dense
Can be monounsaturated (1 Carbon double bond) or polyunsaturated (more than 1 Carbon double bond)
Structure of an unsaturated fatty acid
Hydrogenation
Hydrogenation: the process that turns plant oils into semi solids (e.g. margarine or vegetable shortening)
Decrease the number of C=C bonds
They add hydrogen to the unsaturated fatty acids to partially saturate them. They don’t do this to all of the C=C bonds, but enough for it to become a semi-solid
Used to improve the shelf-life and appearance of foods
The product doesn’t finish off being fully saturated – there aren’t enough H’s added to fully saturate the product, it becomes partially saturated
Trans fats
Side effect of hydrogenation
H’s placement creates a trans fat when it is on the opposite side
Hydrogen bonds on opposite sides of the chain of C=C bonds
Cis fats have both H’s on the same side
Putting it all together – triglycerides
Fats: triglycerides that are made of glycerol and 3 fatty acids linked by ester bonds to 1 glycerol molecule
Dehydration Synthesis:
3 waters produced because we have 3 linkages (and water is a product in dehydration synthesis which causes these linkages)
These are all saturated fatty acids in the triglyceride molecule formed above – they can be any kind of fatty acids and can also be a mix of different fatty acids
Fatty acid chains can be all the same, all different, or any combination
Be sure to draw them in the same format/represent them in the same way
Triglycerides are non polar
Phospholipids
These are in cell membranes – phospholipid bilayer
Phospholipids: similar to triglycerides, however 1 of the fatty acids is replaced with a phosphate group and a choline group
Phospholipid layers
Since it has a polar head and non polar tail, one end is hydrophilic (loves water): the heads and one end is hydrophobic (hates water): the tails
Heads are polar so they will be attracted to the water - tails will orient themselves with the oil to get away from the water
They make up most of the cell membrane 2 fatty acids (hydrophobic), glycerol, phosphate and choline (which are charged and therefore they're hydrophilic)
Liposome - 2 layers of phospholipids because there's an aqueous environment on interior & exterior which therefore attracts the heads
This is a bilayer sheet - the building blocks of the liposome
Micelle - single layer of phospholipids - tails on the inside and heads on the outside
Makes the soap bubbles or micellar water
Micelles in the water (little bubbles in solution)
Putting on the cotton swab - opens the micelle and then the tails face outwards and attract grease/makeup - heads are all attracted to the cotton
Steroids (Sterols)
Steroids: made of 4 fused hydrocarbons rings with a variety of side chain functional groups
Group of lipid molecules
Basic structure
Examples:
Cholesterol – needed for cell membranes
Sex hormones – estrogen and testosterone, secreted to do something, chemical messengers
Waxes
Waxes: fatty acids linked to alcohols (ester)
Fatty acids have carboxyl, alcohols have hydroxyl
Large molecules, no lipids form polymers
Examples
Cutin: water resistant covering made by epidermal cells of plants, conserves water and is a barrier against infection for the plants
Evergreen trees/pine trees – waxes around pine needles to thrive through the winter (evergreens do photosynthesis through the winter because they have enough water, water gets in through the roots)
Beeswax: structure for beehives
Earwax: a water repellent that protects the delicate ears
Where do lipids come from?
Made by the smooth endoplasmic reticulum within the cell
Able to protect the lipids from the cytoplasmic environment (filled with water)
It will then package the lipids into vesicles to be shipped to where they are needed in & out of the cell