Biological Molecules 2 - Carbohydrates and Glucose Flashcards
What elements do carbohydrates contain?
Carbon, Hydrogen and Oxygen
What are the main functions of carbohydrates?
1.Storage and release of energy
2. Cellular structures
How many bonds does each element of carbohydrates form?
Carbon - 4
Oxygen - 2
Hydrogen - 1
What is meant by the singular term ‘saccharide’?
It is another term meant for sugar.
What are the three classes of carbohydrate?
Monosaccharide - monomers which form the building blocks for larger carbohydrates such as glucose
Disaccharide - 2 monosaccharides joined together by glycosidic bonds during a condensation reaction such as lactose, maltose and sucrose
Polysaccharide - Large complex carbohydrates formed form very large numbers of monosaccharides joined by glycosidic bonds
What is the general formula of monosaccharides?
Cn H2n On
If n = 3 then the sugar is…
triose
If n = 5 then the sugar is…
Pentose
Why is glucose considered a hexose sugar?
It has 6 carbons.
Draw the structure of alpha glucose, and then the structure of beta glucose.
https://alevelbiology.co.uk/notes/biological-compounds/
What is meant by the term isomer?
Molecules which have the same general formula but have different arrangement of atoms such as alpha and beta glucose.
What is the difference between alpha and beta glucose?
On carbon 1 of alpha glucose the OH is pointed downwards whereas on beta glucose, the 1st carbon has the OH pointed upwards.
What are other examples of hexose monosaccharides other than glucose?
Galactose and Fructose - they are also isomers as they have the same general formula but different arrangement.
Do you recognise the structure of fructose and galactose? Try to familiarise yourself with them.
https://stock.adobe.com/uk/images/2d-vector-set-the-molecular-structure-of-the-dietary-monosaccharides-n-glucose-fructose-galactose-molecules-isolated-on-white-background-monosaccharides-simple-sugars-monomers-of-carbohydrates/437754716
What is a property of monosaccharides?
They are small in size and soluble in water so they can easily dissolve inside a cell and are easily transported in the bloodstream of animals.
Give examples of disaccharides and how they are formed.
Maltose: alpha glucose + alpha glucose
Sucrose: alpha glucose and fructose
Lactose: alpha glucose and galactose
Give the main function of each disaccharide.
Maltose: found inside seeds and is an important source of glucose for germination.
Sucrose: transported through the phloem of plants.
Lactose: found in milk and an source of energy for the young.
What is the general formula of disaccharides?
C12 H22 O11 (+H2O)
What is the resulting link between two sugars called?
A glycosidic bond.
What carbon is the glycosidic bond between two monosaccharides?
Carbon 1 of one monosaccharide bonded to carbon 4 of a 2nd.
What reaction breaks down disaccharides to monosaccharides?
A hydrolysis reaction chemically inserts water into the bond to break it.
Are polysaccharides insoluble and why?
Yes because they are large in size.
Why does glucose need to be stored appropriately?
glucose is soluble in water and this can affect osmosis.
How is glucose overcome from affecting osmosis?
We can convert glucose to a storage polysaccharide which will give the properties of being insoluble, compact and easily hydrolysed.
Give 4 examples of polysaccharides.
Starch, glycogen, chitin and cellulose
Briefly describe starch.
Starch is the energy storage in plant cells and is made up of alpha glucose monomers. Starch is also made up of two different molecules: amylose and amylopectin.
Describe the structure and bonding of amylopectin
It is a branched polymer
It contains alpha 1 - 4 and alpha 1 - 6 glycosidic bonds.
Describe the structure and bonding of amylose
It is a straight-chained polymer and it is a helical shape
It contains alpha 1 - 4 glycosidic bonds.
Briefly describe glycogen.
It is the energy storage in animals and it is very readily hydrolysed. It is also made up of alpha glucose monomers. It is found in muscle and liver cells.
Describe the structure and bonding of glycogen.
It is highly branched so that glucose is readily hydrolysed. It contains alpha 1 - 6 and alpha 1 - 4 bonds.
Starch and glycogen are made up of alpha-glucose monomers. This means that they have the same structural features as glucose when it is stored correctly in a cell in the appropriate form. Recall the structural features if glucose in a cell.
Insoluble - so doesn’t affect osmosis within a cell
Compact - so large amounts can be stored in small spaces
Readily hydrolysed - to release glucose for respiration.
Briefly describe cellulose.
It provides strength and rigidity in plant cell walls and it is made up of beta-glucose monomers. The cellulose cell wall is inelastic and has a high tensile strength to prevent the plant cells from bursting.
Describe the structure of cellulose.
each adjacent monomer is rotated by 180 degrees
which form straight chains
straight chains joined together by hydrogen bonding between OH groups
these straight chains formed together by hydrogen binding form a strong microfibril
these microfibrils form a strong cellulose bundle
the beta-glucose monomers are joined together by alpha 1 - 4 glycosidic bonds
Why is cellulose freely permeable
there are spaces between the fibres which means water and solutes can penetrate through to the cell membrane
Briefly describe chitin
It is made up of beta-glucose monomers
similar in structure to cellulose but some OH groups in each beta-glucose molecule are replaced by nitrogen-containing acetyl amine groups
It forms part of an insect’s exoskeleton.
What are the 3 main features of chitin?
Strong, lightweight and waterproof
