Monomers, Polymers and Carbohydrates Flashcards
What are monomers?
small units that are the components of larger molecules, e.g monosaccharides such as glucose, amino acids and nucleotides
Give examples of monomers?
monosaccharides such as glucose, amino acids and nucleotides
What are polymers?
molecules made from many monomers joined together.
What are monomers joined by?
A chemical bond in a condensation reaction where by a water molecule is eliminated.
What is a condensation reaction?
A reaction that joins two molecules together with the formation of a chemical bond and the elimination of a molecule of water.
What is a hydrolysis reaction?
A reaction that breaks a chemical bond between two molecules and involves the use of a water molecule.
What are monosaccarides?
A single monomer
What is a disaccharide?
Two monomers joined together
Name three monosaccarides?
Glucose, Galactose and fructose
What is glucose?
A monosaccharide containing 6 carbon atoms in each molecule, and is the main substrate for respiration and therefore of great importance. It has two isomers – alpha and beta glucose with structures
What is Maltose?
A disaccharide formed by the condensation of two glucose molecules.
What is sucrose?
A disaccharide formed by condensation of glucose & fructose.
What is lactose?
A disaccharide formed by condensation of glucose & galactose.
What is a polysaccharide
Long chains of monosaccharides linked by glycosidic bonds.
What do polysaccharides include?
- Glycogen and starch are both formed by the condensation of alpha glucose.
- Cellulose formed by the condensation of beta glucose
What is Glycogen?
The main energy storage molecule in animals and is formed from many molecules of
alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds.
Describe the components of glycogen?
- large number of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches.
- relatively large but compact molecule thus maximising the amount of energy it can store.
- Insoluble means it will not affect the water the potential of cells and cannot diffuse out of cells.
What is Starch?
A polysaccharide that stores energy in plants and is a mixture of two polysaccharides called amylose and
amylopectin
What is Amylose?
Amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, and as a result amylose is coiled and thus a very compact molecule storing a lot of energy.
What is Amylopectin?
Amylopectin is branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds. Due to the presence of many side branches, these can be acted upon simultaneously by many enzymes and thus broken down to release their energy.
What are the properties of starch?
- insoluble: so will not affect cell water potential,
- Compact: so a lot of energy can be stored in a small space
- When it is hydrolysed the released alpha glucose can be transported easily
What is Cellulose?
A component of cell walls in plants and is composed of long, unbranched chains of beta glucose which is joined by glycosidic bonds.
What are Microfibrils?
Strong threads are made of long cellulose chains running parallel to one another that are joined together by hydrogen bonds forming strong cross-linkages
Why is Cellulose important?
Cellulose is important in stopping the cell wall from bursting under osmotic pressure:
- it exerts inward pressure that stops the
the influx of water. - Meaning: that cells stay turgid and rigid, helping to maximise the surface area of plants for photosynthesis.
What are isomers?
Two molecules with the same molecular formula but differ structurally.
What is Benedict’s reagent used for?
Used to test for the presence of reducing sugars
What are reducing sugars?
Glucose, Galactose and fructose
State the disaccharides?
Maltose, Lactose and Sucrose
What is Benedict’s reagent?
Benedict’s reagent is an alkaline solution of Copper(II) Sulfate
Summarise the Benedict test (reducing sugars)
- Add 2cm3 of the food sample to be tested (needs to be in liquid form, to begin with).
- Add 2cm3 of Benedict’s Reagent.
- Heat the mixture gently in a water bath for five minutes. If the solution turns brick red (orange-brown) then a reducing sugar is present and it is a positive result.
Summarise the Benedict test (non-reducing sugars)
- 2cm3 of food sample (must be in liquid form) is added to 2cm3 of Benedict’s Reagent. This is then placed in a water bath for 5 minutes to gently warm.
- If the colour does not change from blue to brick-red then a reducing sugar is not present.
- Another 2cm3 of the same food sample is then taken and 2cm3 of dilute hydrochloric acid is added. The test tube is then placed in a water bath for 5 minutes. The dilute HCl will hydrolyse the disaccharides and polysaccharides into their constituent monosaccharides.
- After this some sodium hydrogen carbonate is added in order to neutralise the test tube as Benedict’s Reagent will not work in acidic conditions. pH paper is used to check that the solution is neutralised.
- The solution can now be retested by adding 2cm3 of Benedict’s Reagent to the solution and placing it in a water bath for 5 minutes.
- If a non-reducing sugar is present in the original sample then a colour change from
the blue Benedict’s Reagent to brick red (orange-brown) will be observed.
What is the chemical test for starch?
A chemical test for starch is iodine/potassium iodide. If the solution turns blue/black in
colour from orange-brown then starch is present.
What is a Glycosidic bond?
A bond formed as a result of a condensation reaction between saccharide molecules
Name the disaccharides are reducing sugars
Maltose & Lactose
What describes the Benedict’s solution
Clear blue liquid
Describe the chain of a polysaccharide
Their chain may be branched or unbranched and could contain different types of monosaccharides.
Starch, glycogen, cellulose and chitin are examples of polysaccharide
Which is structurally different between starch and cellulose gives them different physical properties
Cellulose is formed by 1-4 Beta-glycosidic linkages and cross links, making them rigid. Starch has 1-4 & 1-6 glycosidic linkages without the tight cross links of cellulose
Chitin is a polysaccharide. What is it’s formula?
(C8H13O5N)n
What is the major difference between chitin and other types of polysaccharide?
Chitin is nitrogenous
Why is it impossible for humans to digest food that contain cellulose?
Human digestive enzyme cannot break the 1-4 beta glycosidic linkage in cellulose, which requires a special enzyme that is absent in humans
