2.1.2 d-g Biological Molecules - Carbohydrates Flashcards
What are the elements present in Carbohydrates?
C , H, O
Define monosaccharide
a single sugar molecule
monomers of carbohydrates
Define Disaccharide
a molecule made of 2 monosaccharides joined by a glycosidic bond
Define polysaccharide
a polymer made up of more than 2 monosaccharides joined together
Define pentose sugar
a monosaccharide made up of 5 carbons
Define hexose sugar
a monosaccharide made up of 6 carbons
Define triose sugar and give an example
a monosaccharide made up of 3 carbons
- glyceraldehyde
What a furanose ring?
a 5 membered ring
e.g. fructose
What is a pyranose ring?
a 6 membered ring
e.g. glucose
Draw a molecule of alpha-glucose
hexose
OH group on carbon 1 below the ring
Draw a molecule of beta-glucose
hexose
OH group on carbon 1 above the ring
Draw a molecule of ribose
pentose - 5 carbon atoms
Define isomer
molecules with the same molecular formulae but different structural formulae
What is the difference between alpha and beta glucose?
The hydrogen and hydroxyl groups on carbon 1 are reversed
What is the difference between alpha glucose and ribose
- glucose is a pyranose/hexose
- ribose is a furanose/pentose
- glucose is used in starch and glycogen
- ribose is used in RNA
What is the difference between alpha glucose and ribose
- glucose is a pyranose/hexose
- ribose is a furanose/pentose
- glucose is used in starch and glycogen
- ribose is used in RNA
Give 3 examples of disaccharides and state which monosaccharides they are composed of
Maltose - alpha glucose + alpha glucose
Sucrose - alpha glucose + fructose
Lactose - alpha glucose + galactose
State the functions and properties of glucose and where it is found
-monosaccharide
- used in respiration
- used to make polymers like starch, glycogen, cellulose
State the functions and properties of fructose and where it is found
- hexose sugar
- found in fruit
State the functions and properties of galactose
- hexose sugar
Draw a labelled diagram demonstrating how two molecules of glucose form a disaccharide in a condensation reaction, showing the location of a 1,4-glycosidic bond and from where a water molecule is generated
condensation reaction
- hydroxyl groups on carbon 1 and 4
water is lost and bond is formed by remaining oxygen atom
Describe, using a diagram, how hydrolysis of maltose occurs and why water is needed
- the glycosidic bond is broken by adding water
- catalysed by enzymes at 35-40 degrees celsius/ or by being boiled with an acid for acid hydrolysis
Why does alpha-glucose link together to form starch but beta-glucose links together to form cellulose
because of the arrangement of the hydrogen and OH groups on carbon 1
What are the two polysaccharides that make up starch?
- amylose (1,4 bonds only - bc unbranched)
- amylopectin ( 1,4 and 1,6 - bc branches and straight)
Explain with use of diagrams why glycosidic bonds are called 1,4 or 1,6
depends on whether the glycosidic bonds between the OH groups on carbons 1 and 4 or 1 and 6.
What is the structure of a cellulose fibre?
Cellulose chains link via hydrogen bonds
- forming strong fibres - called microfibrils
- microfibrils give structural support for cells
Describe and explain the properties and functions of starch.
STARCH: stores excess glucose in plants
- made up of amylose and amylopectin
- coils into helix
- insoluble (no effect on water potential) + compact - ideal for storage
- amylose - straight, unbranched (1,4 a glucose)
- amylopectin - long branched (1,4 + 1,6 a glucose)
- amylopectin side branches - allow enzymes to hydrolyse into glucose
quickly
Describe and explain the properties and functions of glycogen.
GLYCOGEN: polysaccharide - stores excess glucose in animals + fungi
- coils into helix
- insoluble (no effect on water potential) + compact - ideal for storage
- similar to amylopectin but v. more branched
- 1,4 + 1,6 a-glycosidic bonds = branched
- more branches - hydroylsed into glucose faster - glucose released quicker - meet high metabolic demands of animals
Describe and explain the properties and functions of cellulose.
CELLULOSE: makes up cell wall in plants
- long straight
- insoluble (doesnt effect water potential) (permeable to solutes)
- unbranched chains of beta glucose
- doesnt form helix
- forms cellulose molecules from b-glucose which join via hydrogen bonds to form layers of microfibrils
- give strength to cell walls