Carbohydrates - B1 Flashcards
Are most carbohydrates monomers or polymers?
Polymers
What 3 groups are carbohydrates split into?
Monosaccharides, disaccharides, and polysaccharides.
What are monosaccharides?
-single sugars
-different ones contain different numbers of carbon atoms
can be made into di/polysaccharides
Name 3 examples of monosaccharides.
Glucose, fructose, galactose
What is the difference between alpha glucose and beta glucose?
Alpha- hydrogen on top, hydroxyl on bottom
Beta- hydrogen and hydroxyl on carbon 1 are swapped around
They are isomers.
What does it mean if alpha and beta glucose are isomers of each other?
They are both molecules of glucose(same molecular formula), but the atoms have been arranged in a different way(different structure), giving them different properties.
What are disaccharides?
A substance made from two monosaccharides.
Give 3 examples of disaccharides.
Maltose, sucrose, lactose.
What type of reaction bonds two monosaccharides together, and what is produced along with the disaccharide?
-Condensation reaction
-H2O is produced.
What monosaccharides form:
a)sucrose?
b)maltose?
c)lactose?
a)alpha glucose, fructose
b)alpha glucose, alpha glucose
c)alpha glucose, galactose
What reaction turns disaccharides(polymers) back into monosaccharides(monomers)?
Hydrolysis, add water.
What is hydrolysis?
Polymers being broken down to constitute monomers.
What is condensation?
Two monomers join together by a chemical reaction.
What are three examples of polysaccharides?
Starch, glycogen, cellulose.
What is the amylose structure of a starch molecule and what is it’s functions?
-Un-branched and highly coiled, it has C1-4 bonds.
-The coiled shape makes it compact and excellent for storage
What is the amylopectin structure of starch and what is it’s function?
-C1-4 and C1-6 glycosidic bonds so it’s coiled. but also has branches.
-This increases the area for enzymes to hydrolise so it can be broken down quicker into glucose than amylose
What is the function of starch being insoluble?
Doesn’t effect osmosis(presence of starch in solution will not lower water potential causing unwanted movement of water), doesn’t diffuse out of cells.
What is the function of glycogen being more branched than starch and being coiled?
There are more free ends where glucose molecules can either be added or removed, allowing for condensation and hydrolysis reactions to occur more rapidly
- storage or release of glucose can suit demands of the cell
- more branched and coiled makes it more compact which helps them store more.
Is glycogen also insoluble?
Yes.
What is cellulose made from?
Beta glucose.
What happens to the beta glucose in cellulose molecules because the hydroxyls don’t line up?
Every other glucose turns 180 degrees so that they match up and can form glycosidic bonds, also making it linear(the chains)
Why are cellulose molecules strong?
The rows allow lots of hydrogen bonds to form between OH groups. This gives cellulose strength for cell walls. The OH bonds form between and within chains.
Thy hydrogen bonds are weak on their own, but the sheer amount of them makes them strong.
Is cellulose branched or unbranched?
Unbranched as it only has C1-4 bonds.
What are the different parts of the structure of cellulose?
-CH2OH group alternates
-doesn’t coil
-unbranched
-forms fibrils->lots of chains cause fibrils which add to strength beta glucose->cellulose fibres->microfibrils->macrofibrils->matrix
What is the role of cellulose?
-Important structural molecule
-Major cell wall component
What is a reducing sugar?
A sugar that give electrons(reduce) to other molecules.
What are some examples of reducing sugars?
All monosaccharides and most disaccharides such as maltose and lactose.
What is produced in a chemical reaction with reducing sugars?
Reduce copper ions in copper sulfate which forms an orange/red precipitate copper oxide.
What is a non-reducing sugar? Give an example.
A sugar that cannot give electrons. An example is sucrose.
What is needed to be added in a non-reducing sugar chemical test?
You need to add HCl to conduct the test. This hydrolyses to produce monosaccharides.
Which chemical test is for:
a)reducing sugar
b)non-reducing sugar
c)starch
a)Benedict’s
b)Benedict’s
c)iodine
Explain the chemical test for a reducing sugar.
Benedict’s test:
-Add Benedict’s solution to 10cm^3 sample in test tube.
-Shake mixture and heat in a water bath for 3 mins(heat don’t boil)
-Observe colour change(precipitate): blue>green>yellow>orange>brick red
Explain the chemical test for a non-reducing sugar.
Benedict’s test:
-Add 3cm^3 hydrochloric acid to the non-reducing sugar(sucrose)
-Heat in a water bath for 1 min
-Add one spatula of sodium hydrogen carbonate to neutralise
-Perform the Benedict’s test as completed for a reducing sugar
-Observe colour change: blue>green>yellow>orange>brick red
Explain the chemical test for starch.
Iodine test:
-Place drops of iodine on a sample
-If present it will turn from a orange/brown colour to a blue/black
