carbohydrates Flashcards
Define the term monomer
Monomers are small identical or similar molecules which can be condensed (joined/linked together) to make larger molecules called polymers.
Define the term polymer
Polymers are large molecules made from joining many (3 or more) identical or similar monomers together.
Describe hydrolysis and condensation reactions
A condensation reaction joins two monomer units together with the removal of one water molecule.
A hydrolysis reaction involves adding one molecule of water to break the bond between two monomers.
State the elements found in carbohydrates.
The elements found in carbohydrates are Carbon (C), Hydrogen (H) and Oxygen (O).
H : O is 2 : 1 .
name 3 monosaccharides
glucose and galactose and fructose.
molecular formula of glucose
C6 H12 O6
alpha glucose
penguin
beta glucose
Egyptian mummy
show how two glucose molecules join together by a condensation reaction to form maltose. Give the molecular formula for this reaction.
C6H12O6 + C6H12O6
——–> C12H22O11 + H2O
Name the bond formed when two monosaccharides join together
The bond which forms between the two monosaccharides is called a glycosidic bond.
look in booklet and identify fructose and galactose
fructose has only 5 carbons with a pointy head
galactose has both (OH) groups facing up
glucose + glucose =
maltose and hydrolytic enzyme is maltase
glucose + galactose =
lactose and hydrolytic enzyme is lactase
glucose + fructose =
sucrose and hydrolytic enzyme is sucrase
easy way to remember - sucrose is found in fruit - fruit sounds like fructose
carbohydrates into sugars
sugars into monosaccharide and then into ( glucose, fructose, galactose)
sugars into disaccharides and then into (sucrose, maltose, lactose)
carbohydrates into polysaccharides
polysaccharides and then into storage molecules such as ( glycogen(humans)) and (starch(plants))
polysaccharides and then into structural molecules such as cellulose in plants
describe starch? (alpha glucose)
starch is helical so it doesn’t take up much space
its a polymer of alpha glucose joined by glyosidic bonds
its insoluble so doesn’t effect the water potential
large so cant leave the cell
1 - 4 glyceridic bonds
can be branched or unbranched
describe glycogen ( alpha glucose )
short chains
more highly branched
larger surface area
stored in muscles and liver
insoluble so doesn’t affect water potential
more short chains - glycogen being more readily hydrolysed into glucose for respiration
structure of cellulose (beta glucose) - related to its function
long straight unbranched chains of beta glucose
joined by hydrogen bonds
forms microfibrils
provides strength and rigidity
Identify alpha glucose is a reducing sugar and as such forms an orange precipitate when boiled with Benedict’s solution.
- Add equal volumes of Benedict’s solution;
- Heat to 95 ⁰C;
- Red/orange/yellow/green precipitate (shows reducing sugar present);
@ Benedict’s test for reducing sugar (glucose, galactose, lactose, maltose, fructose)
Identify sucrose and starch are a non-reducing sugars and as such do not form an orange precipitate when boiled with Benedict’s solution.
No colour change
Explain that following hydrolysis by heating with acid into monomer units (non-reducing sugars) of sucrose form an orange precipitate when boiled with Benedict’s solution.
- Add dilute hydrochloric acid (HCl) to sugar solution; - (to hydrolise glycocidic bonds)
- Boil sugar solution;
- Add sodium hydrogen carbonate (NaHCO₃) (alkali) to neutralise;
- Add equal volumes of Benedict’s solution to the sugar solution;
- Heat to 95 ⁰C;
- Red/orange/yellow/green precipitate (shows reducing sugar present);
Give test for starch as add drop of iodine solution, if starch is present solution will turn blue/black
- Add potassium iodide(KI) solution to the food sample;
- Blue/black/purple indicates starch is present;
