Monomers, Polymers And Carbohydrates Flashcards
Define Monomer. Give Examples
Smaller units that join to form larger molecules.
E.g., Monosaccharides (glucose, fructose, galactose), nucleotides, amino acids
Define Polymer. Give some examples
Molecules formed when many monomers join together.
E.g., Polysaccharides, DNA/RNA, Protein
What happens in a condensation reaction?
For 2 monosaccharides, a new chemical bond has formed between 2 molecules (glycosidic bond.)
It is the chemical process in which 2 molecules combine to form a more complex one with the elimination of a simple substance, usually water. Examples are polysaccharides and polypeptides.
What happens in a hydrolysis reaction?
It is the breaking of large molecules to smaller ones by the addition of water.
What is a monosaccharide? Give some examples.
Monomers from which larger carbohydrates are made from. Examples of hexose Monosaccharides are glucose, fructose and galactose. They all follow the C6H12O6 formula.
The type of bond formed when Monosaccharides react.
(1,6, or 1,4) Glycosidic bond. They are chemical bonds that link ring-shaped sugar molecules to other molecules.
Describe 3 Disaccharides and describe how they have formed.
Lactose: alpha Glucose and Beta Galactose
Maltose: x2 Alpha Glucose
Sucrose; Alpha Glucose and Beta Fructose
Describe 2 main functions of Monosaccharides:
Energy source for fuelling cell metabolism e.g., respiration.
Structural units for disaccharides and monosaccharides.
Information on Lactose
Lactose is found in milk and the enzyme is lactase. Naturally occurs in small intestines of mammals.
Information on Maltose.
Uses enzyme maltose. Naturally occurs in small intestines of mammals and germinating seeds.
Information on Sucrose.
Table sugar from plants as sugar cane. Sucrase. Found in small intestines of mammals.
Test for Reducing Sugars
- Add 2cm3 of food sample into a test tube (if not in liquid form, grind it up in water.)
- Add equal volumes of Benedict’s reagent.
- If present, it turns brick-red. Spectrum of colour depends on the amount of sugar (green if small amount.)
Test for Starch
- Add 2cm3 of sample into a test tube/ 2 drops into a depression on a spotting tile.
- Add 2 drops of Iodine solution and shake.
- If present, blue-black colouration.
Test for Non-reducing sugars.
- Add 2cm3 of sample into a testable.
- Add dilute HCl (2cm3) and place test tube in a gently boiling water bath (80 degrees) for 5 minutes - HCl hydrolyse the glycosidic bond.
- Add equal amounts of Sodium hydroxide to neutralise acid
- Add 2cm3 of Benedict’s reagent and gently heat mixture for 5 minutes.
- If present, would turn brick red.
Give examples of Reducing Sugars
-all monosaccharides
-Maltose and Lactose (2 examples of disaccharides.)
Give examples of Non-reducing sugars
- Sucrose
-Polysaccharides
What is a reducing sugar?
A sugar that can donate electrons to another chemical or reduce another chemical.
What is a non-reducing sugar?
Sugars that do not possess the ability to donate electrons, hence they cannot be oxidised.
What does quantitive mean?
Tells us the amount of substance present.
What does qualitative mean?
Tells us if a substance is either present or not.
Outline how colorimetry can be used to give qualities results for the presence of sugar and starch.
Using machine, we can plot a calibration curve, with absorbance and concentration, which we can use to read off the concentration.
Function of Starch
Energy storage in plants
Structure of Starch
-Found in plants, in small grains
- formed through the condensation reaction between alpha glucose with glycosidic bonds.
-made up of amylose and amylopectin
Structure and function of Amylose
-makes up 20% of starch.
- made up of (1,4) glycosidic bonds - makes it compact as it is linear, so can then coil up into a helical structure, so lots can be stored in a small amount of space.
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