Lecture 6: Carbohydrates and Lipids Flashcards
Three categories of carbohydrates
- Monosaccharides: single sugar molecules
- Disaccharides: two sugar molecules linked covalently
- Polysaccharides: Multiple sugar molecules linked together covalently
How are carbons, oxygens and hydrogens related in carbohydrates?
There are always the same number of carbons as oxygens and always double the amount of hydrogens
Difference between sugars and alcohols?
Sugars either have an aldehyde at the end of the molecule or a ketone in the middle of the molecule.
What is an isomer?
Molecule with the same molecular formula but different structure
Do isomers have the same chemical properties?
Yes
What is an optical isomer?
When four different atoms are attached to a central carbon atom in two different ways, these are called optical isomers
What is a glycosidic linkage?
Bond between a carbohydrate and another molecule(can be another carbohydrate)
Why are alpha-glucose and beta-glucose the only two disaccharides that matter?
Those are the only two that enzymes evolved to catalyze
What is starch?
Starch is a polysaccharide made from alpha(1-4 linkages) between alpha glucose molecules
What is starch in plants?
Amylose
Is starch branched or unbranched?
Unbranched(just a long chain)
What is amylopectin?
Moderately branched starch found in plants
What is glycogen?
Moderately branched starch found in animals
Is starch hard to breakdown?
NO
How is cellobiose made?
Two beta-glucose molecules from a beta 1-4 link to create cellobiose
Cellobiose vs Cellulose
Cellobiose: disaccharide
Cellulose: polysaccharide
Is cellulose branched or unbranched?
UNBRANCHED
Characteristics of cellulose?
-Very linear
-Very symmetrical
-Branched
-Hard to breakdown
What happens when you line up multiple cellulose strands next to each other?
Hydrogen bonds form between the strands, resulting in a very stable structure that can be hard to breakdown
What is the role of oligosaccharides?
They determine blood groups in our body
-They attach to proteins
Roles of lipids(7)
- Energy storage
- Cell membranes
- Capture of light and energy(carotenoids)
- Hormones and vitamins
- Thermal Insulation
- Electrical Insulation of nerves
- Water repellency(waxes and oils)
Characteristics of lipid?
-insoluble in water
- not polymers
Why are lipids in soluble in water?
-Lipids are made up of C-H bonds which are non-polar and hydrophobic. Since “like” dissolves “like” and water is polar, lipids are not soluble in water
Structure of fatty acids
- Carboxyl group (COOH) at one end of the chain
-At the other end straight carbon-hydrogen(hydrocarbon) chain
What is amphiphilic?
Something that is both hydrophilic and hydrophobic
Characteristics of fatty acids(2)?
-Derived from fats and oils
-Amphiphilic(hydrophilic carboxyl group, hydrophobic hydrocarbon chain)
Saturated vs Unsaturated fatty acids?
Saturated: Carbon chains completely surrounded by hydrogens, no double bonds
Unsaturated: Carbon chains missing some hydrogens, results in a double bond and kink in the hydrocarbon chain.
How are fats formed?
Fats are formed from three fatty acid chains covalently linked together via ester linkages to a glycerol molecule
What is glycerol?
Three carbon compound with each carbon being attached to one hydroxyl group
How do ester linkages occur in fatty acids?
OH of carboxyl group of fatty acid reacts with OH group of glycerol and forms an ester linkage releasing one water molecule (oxygen is now bound to carbon)
What is the structure of a phospholipid?
-Two hydrocarbon chains(non-polar)
- Hydrophilic head group(polar)
What is found in the hydrophilic head group of the phospholipid?
-Phosphate groups
-Charged Molecules
Characteristics of the lipid bilayer?
-Fluid
-Things inserted into it can move laterally
-Temperature affects it fluidity/ridgidity
What happened when the lipid bilayer is subject to cold temperatures?
- there is an increase in phospholipids with unsaturated hydrocarbon tails(the kinks allow for more freedom of movement)
- Phospholipids decrease their tails lengths
What happened when the lipid bilayer is subject to hot temperatures?
- Less unsaturated fatty acid tails
- Tail length increases(increases drag)
Functions of sugar?
- Energy storage
-Building block for nucleic acids
-Structural component
What two functional groups can be found in sugars?
- Hydroxyl
- Carbonyl(aldehyde/ketone)
What molecule does alpha 1-4 linkage give rise to?
Maltose and eventually starch
What molecule doe beta 1-4 linkage give rise to?
Cellobiose and eventually cellulose
What shape is starch?
Spiral
What provides more energy starch or fats?
Fats but take longer(better for long term storage)
Why do phospholipids assemble into a circular sphere shape?
It is most energetically favourable because no more hydrophobic edges are exposed to the water
