b1.1 carbohydrates and lipids Flashcards
what are the chemical properties of carbon?
each carbon atom can form 4 covalent bonds
carbon is contained in nucleic acids, carbohydrates, lipids and proteins
carbon can form rings (nucleic acids), branched and unbranched molecules
what are monomers, polymers and macromolecules?
monomers are the smaller subunits from which larger molecules are made. polymers are molecules made up from a large number of monomers in a chain. the process by which monomers join to form polymers is called polymerisation.
macromolecules are very large molecules. polymers can be macromolecules, but not all polymers are macromolecules.
what is a condensation reaction?
polymers are formed during condensation reactions. a condensation reaction occurs when molecules combine together, forming covalent bonds and resulting in polymers. water is removed as part of the reaction.
what is a hydrolysis reaction?
polymers often need to be broken down into their monomers. the reaction that allows this to occur is a hydrolysis reaction. in hydrolysis of macromolecules, covalent bonds are broken when water is added.
what are the functions of carbohydrates?
carbs make up 10% of the organic matter in a cell. functions include:
- energy source (released from glucose during respiration)
- energy store (starch & glycogen)
- structural (cellulose)
some form parts of larger molecules (nucleic acids, glycolipids)
what are the properties of monosaccharides?
monosaccharides can join together via condensation reactions. the new chemical bond that forms between two monosaccharides is known as a glycosidic bond.
monosaccharides have the general formula Cn H2n On.
monosaccharide properties include:
1. soluble in water
2. sweet
3. form crystals
4. chemically stable
5. yields high levels of energy when broken down
there are different types of monosaccharides formed from molecules with varying numbers of carbon atoms, eg:
- triose 3c
- pentose 5c
- hexose 6c
what is alpha glucose?
C₆H₁₂O₆ - tends to occur as ring structure as it is more stable than linear
what is beta glucose?
the same as alpha glucose, however there is a slight difference in the structure. the hydroxyl group at carbon 1 is above the plane of the ring (instead of above it).
a-glucose and b-glucose have very different properties due to these structural differences.
different shaped forms of the same molecule are called isomers.
what are disaccharides?
disaccharides are :
- soluble
- sweet tasting
- forms crystals
examples are:
- glucose + glucose = maltose
- glucose + fructose = sucrose
- glucose + galactose = lactose
how are disaccharides formed?
disaccharides are formed when two monosaccharides are joined together by a glycosidic bond (covalent).
the reaction involves the formation of a water molecule.
the glycosidic bond forms at carbon 1 of the first glucose molecule and carbon 4 of the second - called a 1,4-glycosidic bond. many of these bonds results in an unbranched chain.
carbon 1 can also form a glycosidic bond with carbon 6, which results in side branches
what is amylose?
amylose consists of thousands of a-glucose molecules, all bonded together by 1,4-glycosidic bonds through condensation reactions. it has unbranched, straight chains.
amylose chains coil into a spring due to ring structure of glucose and 1,4 linkage. this makes it compact and ideal for storage.
starch is a mixture of amylose and amylopectin molecules
what is amylopectin?
amylopectin consists of a-glucose molecules in a branched chain, bonded by 1,4 and 1,6 glycosidic bonds.
starch is a mixture of amylose and amylopectin molecules
what is glycogen?
glycogen is a polymer of a-glucose moelcules. it has a similar structure to starch, but has shorter chains with lots of branches.
it is found in animals (liver and muscle cells) and can be hydrolysed into glucose molecules - therefore is an energy storage molecule.
due to shorter chains, it can be hydrolysed quicker and so releases energy quicker than starch - often called animal starch. it is insoluble
what is cellulose?
cellulose is a polysaccharide of b-glucose molecules bonded together by condensation reactions. the chains are straight and long (unlike chains of a-glucose molecules, which are coiled and often branched). the chains are strong, which means cellulose has a structural function in plants.
the b-glucose, the hydroxyl group on c1 is angled upwards and the hydroxyl group on c4 is angled downwards. to bring these groups together and allow a condensation reaction to occur, each b-glucose added to the chain must be inverted in relation to the previous one.
