3.1.2 Carbohydrates Flashcards
How many monomers does glucose have , name them and draw them ?
2 , Alpha and Beta glucose
How are polysaccharides formed ?
Polysaccharides are formed by the condensation of many glucose
units.
How are glycogen and starch formed ?
Glycogen and starch are formed by the condensation of
α-glucose.
How is cellulose formed ?
Cellulose is formed by the condensation of β-glucose
What three monosaccharides do you need to know the structure of ?
Glucose , Fructose and Galactose
How do disaccharides form ?
Two monosaccharides are joined together by a
glycosidic bond. This is a condensation reaction which involves the removal of a
molecule of water
What is a polysaccharide ?
A long chain of monosaccharides that are linked by glycosidic bonds are known as a
polysaccharide
How is sucrose made ?
Glucose and Fructose
What is the stucture and fucntion of cellulose ?
Cellulose is a polymer of β glucose - it’s made of long, unbranched chains of
beta-glucose.
‒ Condensation reactions link carbon atom 1 to carbon atom 4 on the next β
glucose.
‒ The glucose subunits in the chain are oriented alternately upwards and
downwards.
‒ The consequence of this is that the cellulose molecule is a straight chain rather
than curved.
The cellulose chains are linked together by hydrogen bonds to form strong fibres
called cellulose microfibrils.
‒ Because of those fibres, the tensile strength of cellulose provides structural
support for the cells (e.g the cell walls) and prevents plant cells from bursting -
even under very high (water) pressure.
How is lactose made ?
glucose and galactose
How is Maltose made ?
Glucose and glucose
Where is starch found and what is it used for ?
Cells get their energy from glucose. Plants store excess glucose as starch.
‒ When a plant needs more glucose for energy, it will break down that starch to
release the glucose
What are the two versions of starch ?
Amylose and Amylopectin
What type of glucose is starch made of ?
Alpha glucose two variations amylose and amylopectin
What is the struture and function of amylose ?
Amylose is a long, unbranched chain of α-glucose. The angle of the glycosidic
bonds give it a coiled, cylinder-like structure. This compact structure is good for
storage because more glucose can be stored in a small space
What is the structure and function of amylopectin ?
Amylopectin is a long, branched chain of α-glucose. It has side branches which
allow the enzymes that break the molecule down to access glycosidic bonds
easily - meaning the glucose can be released quickly
Why is starch good for energy storage ?
starch is insoluble, water cannot enter the cells by osmosis - which makes it
very good for storage.
What number on carbons are the condensation links on ?
Condensation reactions link carbon atom 1 to carbon atom 4 on the next
α-glucose.
Where is glycogen found and what is the main function of it ?
Glycogen is the main energy storage material in animals
Where is glycogen stored in humans ?
it is stored in the liver and some muscles
Where is glycogen used ?
It’s used in cells where large stores of dissolved glucose would cause osmotic problems
What is the stucture of glycogen like ?
Glycogen has a similar structure to amylopectin but it has a lot more side
branches. These extra branches mean the stored glucose can be released very
quickly - something that is very important in animals.
What are the adaptations that make glycogen a suitable energy source ?
As a result of the branches, glycogen is very compact which makes it very good
for energy storage.
‒ Glycogen does not affect the osmotic balance of cells - i.e. cause too much water
to enter them.
What are reducing sugars ?
All monosachharides and some disaccharides including maltose and lactose
How do you test for reducing sugars and what is the positive result ?
Add Benedict’s reagent (which is blue) to a sample and heat it in a water bath that
boils the mixture for 5 minutes.
‒ If the test is positive, it will form a coloured precipitate (solid particles suspended
in the solution).
blue to green, yellow, orange, or brick red
How do you compare the amount of reducing sugars in different solutions ?
higher concentration of reducing sugar , further the colour change blue to green, yellow, orange, or brick red (more accurate way is to filter the solution and weigh the precipitate )
How do you test for a non-reducing sugar ?
Following a negative Benedicts test
Take a fresh sample of the solution and either heat it with diluted hydrochloric
acid or hydrolyze using enzymes.
‒ You can then neutralise it with sodium hydrogencarbonate.
‒ Once you have done these, you can continue the Benedict’s test in the same way
you would for a reducing sugar.
‒ If the test is positive, it will form the coloured precipitate just the same as for a
reducing sugar. If the test is negative, the solution stays blue and it means the
solution does not contain any sugar
How do you test for starch and what is the positive result?
Add iodine dissolved in potassium iodide solution to the test sample the colour changes from brown-orange to a dark blue-black
