Carbohydrates Flashcards
What is the general formula for monosaccharides?
(CH2O)n
Where n = 3 to 7
Where are carbohydrates used in living things?
As a source of energy for respiration
Storage
What is the most common monosaccharide?
Hexoses
What are some examples of monosaccharides?
Glucose
Fructose
Galactose
Ribose
What are the types of glucose?
Alpha glucose
Beta glucose
What rules are there for drawing alpha glucose?
Oxygen has to be bonded to the carbon not the hydrogen in OH
Rule for the OH's Down Up Down Down
Are all simple sugars reducing sugars?
No
How do you test for reducing sugars?
Add an equal volume of Benedict’s reagent to the sample
Heat the mixture for 3-5 mins
A brick-red precipitate indicates the presence of a reducing sugar
What is a reducing sugar?
It has the power to reduce something else
The sugar itself loses electrons and oxidises but it reduces another substance that gains the electrons
What helps to remember oxidation and reduction?
OIL RIG
What reaction joins two monosaccharides together?
A condensation reaction
What are two monosaccharides bonded called?
Disaccharides
What is the bond called that holds the monosaccharides together?
Glycosidic
What do you get when you react glucose + glucose?
Maltose
What do you get when you react glucose + fructose?
Sucrose
What do you get when you react glucose + galactose?
Lactose
What happens in a condensation reaction?
A molecule of water is removed
What is the reverse of a condensation reaction?
Hydrolysis
How do you work out the formula of a disaccharide?
Add the two monosaccharides together and take away water
What are the products of a condensation reaction?
A disaccharide and water
How do you test for non-reducing sugars?
Add an equal volume of Benedict’s Reagent to the sample and heat in a gently boiling water bath for 5 mins
If it doesn’t change colour a reducing sugar isn’t present
Then add equal volume of hydrochloric acid to the sample (different)
Boil for 5 mins
Slowly add sodium hydrogen carbonate solution
Add Benedict’s Reagent and if brick-red you know it is definitely a sugar present
Why is hydrochloric acid used in the non-reducing sugars test?
To split the disaccharides into monosaccharides using hydrolysis
Why is sodium hydrogen carbonate used in the non-reducing sugars test?
To change the pH as Benedict’s Reagent only works in alkaline conditions
What are the polymers we need to know?
Starch
Glycogen
Cellulose
What is starch primarily made of? Where is it found?
Amylose - a spiral shaped molecule
Very little amylopectin
In plants - as starch grains in chloroplasts
What monomer and bonding is used to make starch?
Alpha Glucose is bonded by 1,4 glycosidic bonds that make stands before coiled
What are the coils held in place by in starch?
Hydrogen bonds
Why does the coiling make amylose suitable to be a storage molecule?
It is compact so allows a lot of Glucose in a small space
What are some properties of starch?
Compact due to coiling
Insoluble and not sweet
Doesn’t affect osmosis and doesn’t diffuse out
Hydrolysed from both ends to produce glucose
What is the test for starch?
Add iodine and a positive result is blue/black
What is the monomer and bonding used in Glycogen?
Alpha glucose is bonded by glycosidic bonds 1,4 and 1,6
Where is glycogen found?
In animal cells as granules in muscle and liver cells
What is the shape of glycogen?
Highly branched
Where is cellulose found?
In plant cells in the cell wall
How do the beta glucoses bond?
Carbon 6 alternates to allow the 2 OH groups to fit together to remove the water when every other glucose inverts
What is the shape of cellulose?
Parallel chains
What are the properties of cellulose?
Very strong
Used for structural purposes
Prevents cells bursting
What is cellulose made from? What bonds and how is cellulose bonded?
Beta glucose joined by glycosidic bonds 1,4
The glucose’s are able to be connected as every other glucose is reflected vertically
There are thousands of weak hydrogen bonds which make it very strong called microfibril
What are the properties of glycogen?
Compact
Insoluble
They are hydrolysed much quicker than starch because of it’s many ends
What is a carbohydrate made up from?
Carbon, hydrogen and Oxygen
With the ratio of -
Hydrogen:Oxygen
2:1
What is a polymer?
A larger molecule or a chain of many monomers linked together in condensation reactions
What is a monomer?
A small single unit of an individual molecule
What is the monomer of a carbohydrate called?
Saccharide
What are simple monomers of carbohydrates called?
Monosaccharides
In animals what are carbohydrates stored as? Where?
Glycogen in liver and muscles
In plants what are carbohydrates used for? Where?
Starch - for storage
Cellulose - cell walls
What is the formula for fructose?
C6H12O6
