L6 Sugars and Lipids Flashcards
What is a carbohydrate?
- A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H), and oxygen (O) atoms, usually with a hydrogen-oxygen ratio of 2:1
- The typical structure of a carbohydrate is a multiple of CH2O, e.g. C3H6O3
What is sugar?
Sugar is a type of carbohydrate
What are the 3 functions of sugar?
What are the 3 functions of sugar?
What are the 3 categories for carbohydrates?
- monosaccharides
- disaccharides
- polysaccharides
What are monosaccharides?
Monosaccharides are simple sugar molecules containing 3 to 7 carbon atoms
What is an example of a monosaccharide?
Glucose
What are disaccharides?
Disaccharides are 2 monosaccharides linked together
What is an example of a disaccharide?
Table sugar
→ it is made of fructose and glucose
What are polysacchirides?
Polysaccharides are 3 or more monosaccharides linked together (more like 100-1000 monosaccharides)
What are some examples of polysaccharides? (3)
- cellulose
- chitin
- starch
Which two functional groups are always found in sugar?
- one carbonyl
- several hydroxyl groups
Give 2 examples of carbonyl groups
- an aldose
- a ketose
What is the relationship between an aldose and a ketose
They are isomers
What are isomers?
Isomers are molecules with an identical molecular - that is the same number of atoms of each element - but distinct arrangements of atoms in space
What are optical isomers? (stereoisomers)
- Stereoisomers are molecules that have the same molecular formula and sequence of bonded atoms, but differ in the 3 dimensional orientation of their atoms in space
- Optical isomers are mirror images of each other
What is an example of sugars that are optical isomers?
Glucose and galactose
- glucose is the sugar in fruit
- galactose is the sugar in milk
What happens to straight-chain glucose in solution?
It forms another covalent bond to become the ring form of glucose.
What are the two types of glucose rings?
Alpha-glucose and beta-glucose
What is the relationship between alpha-glucose and beta-glucose
They are 2 isomers of glucose
How are sugar polymers (polysaccharides) formed?
They are formed by covalent bonds called glycosidic linkages, between the C-1 of one sugar with any OH-group of the second sugar
What does the alpha1,4 glycosidic linkage give rise to?
It gives rise to maltose, and eventually starch
What does the beta1,4 glycosidic linkage give rise to?
It gives rise to cellobiose and eventually cellulose
In starch, are the CH2OH bulky groups on the same side or on opposite sides?
They are on the same side
→ this bends the polymer resulting in the shape of a spiral
In cellobiose, are the CH2OH bulky groups on the same side or on opposite sides?
They are on opposite sides.
→ this makes a very symmetrical straight molecule
What are lipids?
Lipids can be all kinds of structures: the only thing that they have in common is that they are insoluble in water
What are the roles of lipids? (7)
- energy storage (fats and oils)
- cell membranes (phospholipids)
- capture of light energy (carotenoids)
- hormones and vitamins (steroids and modified fatty acids)
- thermal insulation
- electrical insulation of nerves
- water repellency (waxes and oils)
What are the most important lipids? (2)
Fats (solid) and oils (liquid)
What are fats and oils composed of?
3 fatty acids and 1 glycerol connected by covalent bonds
What are fatty acids composed of?
Fatty acids have one carboxyl group and a long hydrocarbon chain
What property do fatty acids have?
They are amphiphilic
What are unsaturated fatty acids?
Unsaturated fatty acids are fatty acids that contain double bonds
What does it entail that unsaturated fatty acids have double bonds?
- The double bonds cause kinks in the fatty acid tails
- Because of this, unsaturated fatty acids cannot be packed as closely together as straight saturated fatty acids
- And this is the reason that butter is solid at room temperature (saturated) and oils are fluid at the same temperature (unsaturated)
What are phospholipids composed of?
Phospholipids have a hydrophilic head and two hydrophobic fatty acid tails that are attached to glycerol
What property do phospholipids have?
They are amphiphilic
What unique capability to phospholipids have?
They can self assemble into lipid bilayers, with the hydrophobic fatty acid tails pointing inward away from water, and the hydrophilic head pointing outwards
Lipid bilayers assemble into what shape?
Into a globular compartment (sphere)
Why is it energetically favorable for lipid bilayers to assemble into a globular compartment?
Because no more hydrophobic parts are exposed to water
Do lipid bilayers move?
Yes, lipid bilayers are very fluid, with phospholipids constantly in lateral motion
What is the effect of unsaturated fatty acids in lipid bilayers on the fluidity and permeability of the membrane?
Unsaturated fatty acids in lipid bilayers increase the fluidity and permeability of the membrane
How do fish and plants use double bonds in phospholipids to keep membrane fluidity stable over a wide variety of temperatures?
They adjust the amount of double bonds that they have to do so. (Increase the number of double bonds to become more permeable and more fluid).
