carbohydrates Flashcards
state the elements present in carbohydrates
carbon, hydrogen, oxygen
state the general formula of carbohydrates
Cx(H2O)y
define the term monosaccharide
a monomer, or single unit, that makes a simple sugar
define the term disaccharide
two monosaccharides joined together by a condensation reaction
define the term polysaccharide
many monosaccharides joined together by a polymerisation reaction
define the term pentose sugar
a monosaccharide containing 5 carbons
define the term hexose sugar
a monosaccharide containing 6 carbons
what is meant by a furanose ring?
a monosaccharide that forms a cyclic ring with 5 members
what is meant by a pyranose ring?
a monosaccharide that forms a cyclic ring with 6 members
define the term isomer
an isomer has the same chemical formula but a different structural formula and arrangement
describe the difference between alpha and beta glucose
the same other than the arrangement of the OH and H group on carbon 1. alpha glucose has the OH group below the carbon whereas beta glucose has the OH above the carbon.
when alpha glucose forms a polysaccharide the chain is helix shaped, whereas beta glucose forms a straight chain.
list the properties of ribose
carbons : 5 oxygens: 10 hydrogens: 5 positioning of OH on carbon 1: above c solubility: soluble polar: yes hydroxyl groups: yes
list the properties of alpha-glucose
carbons: 6
oxygens: 12
hydrogens: 6
positioning of OH on carbon 1: below c
solubility: soluble
polar: yes
hydroxyl groups: yes
list three examples of disaccharides and the monomers they are composed of.
sucrose - alpha glucose and fructose
lactose - alpha glucose and galactose
maltose - 2 x alpha glucose
state the properties and function of glucose
- small, soluble, a good source of energy, polar
- found in plant sap, human blood and most animal cells
state the properties and function of fructose
- soluble, energy source, one of the smallest units
- found in fruits
state the properties and function of galactose
- very stable in solution, very similar to glucose
- not normally found in large quantities but forms a part of milk
state the properties and function of maltose
- formed by the breakdown of starch, made of two alpha glucose molecules
- found in intestines and germinating seeds
state the properties and function of sucrose
- made from glucose and sucrose, good preservative
- found in sugar cane or beat
state the properties and function of lactose
- made from glucose and galactase, the beta glycosidic bonds can cause lactose intolerance. difficult to hydrolyse - slow release of energy.
- found in milk
describe how the hydrolysis of maltose occurs and why water is needed.
two alpha glucose units are broken at the glycosidic 1-4 bond. water is needed to complete the units of alpha glucose produced.
explain why alpha glucose linking forms starch whereas beta glucose forms cellulose.
alpha glucose chains form helix shapes called amylose, alpha glucose also forms branches called amylopectin. these two elements form starch. However when beta glucose forms a chain it forms only straight lines, these are held together by hydrogen bonds to form cellulose microfibrils.
name the two different polysaccharides that link together to form starch.
amylose and amylopectin
explain why glycosidic bonds are called 1,4 or 1,6
they’re called 1,4 if they occur between carbon 1 of one monosaccharide and carbon 4 of another, and 1,6 when it’s between carbon 1 and carbon 6. you start counting the carbons from the very right carbon in the sugar.
