1- carbohydrates Flashcards
monosaccharides
- single sugar molecule
- soluble in water
disaccharide
- 2 monosaccharides
polysaccharide
- many monosaccharides
monosaccharides can join together to form
disaccharides and polysaccharides by glycosidic bonds which are formed in condensation reactions
carbohydrate functions
- usable source of energy via respiration
- storing energy
- building cell walls in plants
polysaccharide function
- energy store
- structural components of cells (cellulose)
glycogen properties
- compact energy store
- low solubility, no osmotic effect
- branched, easily hydrolysed
starch properties
- compact energy store
- low solubility, no osmotic effect
- large
cellulose properties
- main part of plant cell walls
- strong carbohydrate, prevents cells from bursting when taking in water
glucose
- monosaccharide
- contains 6 carbon atoms in each molecule
- main substrate for respiration
- 2 isomers; alpha and beta glucose
alpha glucose diagram
beta glucose diagram
ribose
Ribose is a monosaccharide containing 5 carbon atoms. It is a pentose sugar, and a component of RNA. DNA contains an isomer of ribose called deoxyribose, which lacks the OH group on the second carbon of the sugar ring. This makes it more stable than ribose.
ribose diagram
disaccharides examples
- maltose is a disaccharide formed by condensation of 2 glucose molecules
- sucrose is a disaccharide formed by condensation of glucose and fructose
- lactose is a disaccharide formed by condensation of glucose and galactose
polysaccharides are formed from
many glucose units joined together
types of polysaccharides
- glycogen and starch which are both formed by the condensation of alpha glucose
- cellulose formed by the condensation of beta glucose
glycogen
- main energy storage molecule in animals
- formed from alpha glucoses joined by 1,4 and 1,6 glycosidic bonds
- has large number of side branches, which increases the availability of terminal glucose molecules for aerobic respiration
- large but compact molecule, so maximises the amount of energy it can store
starch
- stores energy in plants
- mixture of 2 polysaccharides called amylose and amylopectin
amylose
- 10-30% of starch
- unbranched chain of alpha glucoses joined by 1,4 glycosidic bonds
- it’s coiled so very compact molecule that can store a lot of energy
amylopectin
- 70-90% of starch
- branched chain of alpha glucoses joined by 1,4 and 1,6 glycosidic bonds
- large numbers of side branches
- compact molecule but not as compact as amylose
cellulose
- component of cell walls in plants
- formed from long, unbranched chains of beta glucose molecules joined by 1,4 glycosidic bonds
- To form 1,4 glycosidic bonds, consecutive beta glucose molecules are inverted at 180º to each other. This allows hydrogen bonds to form between chains, giving cellulose its strength
- Microfibres and microfibrils are strong threads which are made of long cellulose chains joined together by hydrogen bonds and they provide structural support in plant cells
carbohydrates vs lipids
