Carbohydrates Flashcards
State the elements present in carbohydrates.
Carbon, Hydrogen, oxygen
State the general formula of carbohydrates.
(CH2O)x
where x is any number between three and eight
Define the term monosaccharide
A monomer of carbohydrates, a single sugar
Define the term disaccharide
A molecule comprising two monosaccharides, joined together by a glycosidic bond
Define the term polysaccharide
A polymer made up of many sugar monomers (monosaccharides)
Define pentose sugar
a monosaccharide composed of 5 carbons
Define hexose sugar
a monosaccharide composed of 6 carbons
Define the term “triose sugar” and name an example.
a monosaccharide composed of 3 carbons
e.g L-Glyceraldehyde and D-Glyceraldehyde
Draw a molecule of alpha, beta glucose and ribose
look at book
Draw a simplified molecule of alpha- and beta-glucose.
look at book
Define the term isomer
Isomers are molecules that have the same molecular formula, but have a different arrangement
Describe the difference between alpha- and beta-glucose.
Alpha glucose has an -OH (hydroxyl group) that points “downwards”, away from the ring, whereas the -OH on carbon 1 of beta glucose is above the ring.
Draw a table listing the properties and differences between alpha-glucose and ribose.
Similarities:
1. They are both carbohydrates
2. Both monosaccharides
3. Both have the same general formula
4. Both very soluble in water
Differences:
1. Glucose has 6 carbons whereas ribose has 5 carbons
2. Glucose is a hexagon and ribose is a pentagon
3. Glucose main function- production of ATP during aerobic R .
4. Ribose main function- Forms a component of nucleotide DNA and RNA. and also a component of ATP
List 3 examples of disaccharides and for each state which monosaccharides they are composed of. (F)
- Sucrose- alpha-glucose and Fructose
- Lactose- Alpha- glucose and galactose
- Maltose- Alpha glucose and Alpha-glucose
State the properties and functions of glucose
- Glucose is a hexose sugar and can either be alpha or beta glucose which both have a ring structure.
- It’s structure makes it soluble so it can be easily transported - because hydrogen bonds from between the hydroxyl groups and water molecules
- And its chemical bonds contain a lot of energy
- this relates to its function as the main energy source in animals and plants
- It is polar so hydrogen bonds can form.
State the properties and functions of fructose
- A hexose monosaccharide
2. It is the sugar in fruits and is used as a sugar substitute for diabetics
State the properties and functions of galactose
- A hexose monosaccharide
2. It is used to make lactose ( the sugar in milk)
State the properties and functions of maltose
- A disaccharide made of two alpha- glucose molecules
2. Found in intestines and germinating seeds is an intermediate in the formation of starch.
State the properties and functions of sucrose
- A disaccharide made of alpha-glucose and fructose and is table sugar
- In plants carbohydrate is moved from one region to another as sucrose.
State the properties and functions of lactose
- A disaccharide made from alpha-glucose and galactose
- It is the main sugar in milk
- It is difficult to hydrolyse providing a slow release of sugars to baby
Draw a labelled diagram demonstrating how two molecules of glucose form a disaccharide in a condensation reaction, showing the location of a 1,4-glycosidic bond and from where a water molecule is generated.
Look at book
Describe, using a diagram, how hydrolysis of maltose occurs and why water is needed.
- Hydrolysis of maltose occurs when a water molecule is added to maltose disaccharide
- the addition of water results in the breakdown of maltose to two alpha- glucose monosaccharides.
- The 2 hydrogen atoms and the oxygen atom bond with the oxygen joining the monomers.
- This forms two hydroxyl groups on each monosaccharide (OH)
Explain why alpha-glucose links together to form starch whereas beta-glucose links together to form cellulose.
- Because beta-glucose has a hydroxyl group pointing up. This means the hydroxyl group on carbon-1 and carbon-4 would be too far way from each other to react
- So the only way beta-glucose can join together and from a polymer is if alternate beta-glucose molecules are turned upside down.
- This means that the polysaccharide is unable to coil or form branches so is a straight chain molecule- cellulose
- Starch has branches and coils- amylopectin 1-6 bonds as well as 1-4 glycosidic bonds
List the two different polysaccharides that make up starch.
- Amylopectin
2. Amylose
Explain with the use of diagrams why glycosidic bonds are called 1,4 or 1,6.
- because the bond either happens with the hydroxyl group from the 1st carbon in the structure and the 4th carbon.
- or with the 1st carbon and the 6th carbon
Explain how to calculate the number of glycosidic bonds in a carbohydrate given the number of monosaccharides it is made up from.
It will be one less
c-c-c-c-c-c
6 monosaccharides but only 5 bonds
Explain how to calculate the chemical formula for a carbohydrate given the number of hexose sugars it is made up from.
Multiply c6h12o6 by n=number of hexose sugars
and then minus h2o*(n-1)
Describe the structure of a cellulose fibre.
- cellulose molecules make hydrogen bonds with each other forming microfibrils.
- these microfibrils join together forming macrofibrils, which combine to produce fibres
- these fibres are strong and insoluble and are used to make cell walls.
- cellulose is an important part of our diet, it is very hard to break down into monomers and forms the fibre necessary for a healthy digestive system.
State the properties and functions of cellulose
- A straight chain molecule of beta- glucose.
- because it is straight chain the chains can lie parallel to each other. numerous hydrogen bonds link the parallel chains producing strength- means it provides structural support for cells.
State the properties and functions of starch
1.Starch is the main energy storage material in plants
2. Starch is insoluble in water- so it doesn’t cause water to enter the cell by osmosis which would make them sell- good storage
3. Amylose- long unbranched chain of alpha-glucose
the angles of the glycosidic bonds give it a coiled structure- making it compact so it’s very good storage as it can fit a lot in a small space.
4. Amylopectin- long branched chain of alpha-glucose. its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. - it releases glucose quickly.
State the properties and functions of glycogen
- It is a polysaccharide of alpha-glucose, with a very similar structure to amylopectin except with a lot more side branches coming off it.
- loads of branches mean that stored glucose can be released quickly which is important for energy release in animals.
- it is also a very compact molecule so it’s good fro storage.
