3.3 Carbohydrates Flashcards
What are carbohydrates?
Molecules
consisting of carbon hydrogen & oxygen only
What is a monosaccharide?
a single sugar molecule
3.3 Carbohydrates
What are sugars?
Type of molecule
used by organisms as source of ATP/metabolic energy
What is a glycosidic bond?
Covalent bond
between 2 monosaccharides
What is a disaccharide?
2 sugars
joined by glycosidic bond
What are examples of monosaccharides?
Glucose
Fructose
Galactose
What are examples of disaccharides?
Maltose
Sucrose
Lactose
What is a condensation reaction?
Reaction between 2 molecules
forming a larger molecule + releasing water molecule
What is the name of the reaction by which glucose monomers join to form maltose?
condensation
What is a hydrolysis reaction?
Breakdown of molecule
into 2 smaller molecules
by addition of water
Draw the structure of an alpha-glucose molecule:
OH/hydroxyl group on carbon 1 is below the plane of carbon atoms
Draw the structure of a beta glucose molecule:
OH/hydroxyl on carbon 1 is above plane of carbon atoms
What is the difference between alpha & beta glucose?
OH on carbon 1 is above the plane in beta glucose
OH on carbon 1 is below plane in alpha glucose
Name 3 examples of polysaccharide energy stores:
Glycogen
Starch: Amylopectin + Amylose
What is the monomer of glycogen?
alpha glucose
What is the monomer of starch?
alpha glucose
What are the characteristics of an efficient energy store?
- BRANCHED
- more ends for enzymes to bind & hydrolyse carbohydrate
- INSOLUBLE
- does not dissolve & change water potential, causing unwanted osmosis
- COMPACT
- can store high amounts of energy in limited space
What is the energy store which animals & fungi use?
glycogen
Where do animals store glycogen?
liver & muscle cells
Where do plants store starch?
starch grains
Compare the structures of glycogen & starch:
- GLYCOGEN
- 1-4, more 1-6 glycodisic bonds than amylopectin
- more branches & more compact than amylopectin
- more ends for enzymes to hydrolyse into glucose at faster rate
- higher metabolic demand of animals compared to plants
- 1-4, more 1-6 glycodisic bonds than amylopectin
- AMYLOPECTIN
- 1-4, less 1-6 glycosidic bonds than glycogen
- less branches & less compact than glycogen
- less ends for enzymes to hydrolyse into glucose, ∴ slower rate
- lower metabolic demand of plants compared to animals
- AMYLOSE
- 1-4 glycosidic bonds only
- no branching
- hydrogen bonds between ꭤ-glucoses form helix structure
How is the demand for energy of plants & animals reflected in the structure of their energy stores?
Glycogen (energy store in animals) contains many more 1-6 glycosidic bonds than amylose/amylopectin
more branched & compact
more ends for enzymes to hydrolyse glycogen into glucose at faster rate
due to higher metabolic demand in animals compared to plants
What is the monomer of cellulose?
beta-glucose
Describe the structure of cellulose:
straight chained
each alternate beta-glucose molecule is inverted
1-4 glycosidic bonds
(otherwise OH on neighbouring glucose molecules would be too far away to react)
strong & insoluble
Describe how cellulose chains join to form cell walls:
beta-glucose undergo condensation to form straight-chain cellulose polymers with 1-4 glycosidic bonds
hydrogen bonds form between cellulose chains, forming microfibrils
microfibrils join to form macrofibrils
Describe the properties of cellulose:
strong & insoluble
