B M 1 : Carbohydrates Flashcards
What are most carbohydrates?
Polymers
What are polymers? And what are they composed of?
Large, complex molecules composed of long chains of monomers joined together
What are monomers?
Small, basic molecular units
What are examples of monomers?
- monosaccharides
- amino acid
- nucleotides
What are most carbohydrates made of?
Monosaccharides
What elements do app carbohydrates contain?
Carbon
Hydrogen
Oxygen
What is glucose?
A hexose sugar - a monosaccharide with six carbon atoms in each molecule
What are the two types of glucose?
Alpha and beta glucose
What are alpha and beta known as?
Isomers ( molecules with the same molecular structure formula as each other, but with atoms connected in a different way)
What group is reversed in alpha-glucose?
Right hand side group
Hydrogen on top
Oxygen and hydrogen on bottom
What group is reversed in beta-glucose?
Right hand side group
Hydrogen on bottom
Hydrogen and oxygen on top
What reaction joins monosaccharides together?
Condensation reaction
What’s a condensation reaction?
When two molecules join together with the formation of a new chemical bond, and water molecules is released when bond is formed
What bond is formed between two monosaccharides as a molecule of water is released?
Glycosidic bond
What if formed when two monosaccharides join together?
A disaccharide
What disaccharide is formed from a condensation reaction between glucose and a fructose molecule?
Sucrose
What disaccharide is formed from a glucose molecule and a galactose molecule?
Lactose
What reactions breaks polymers and apart?
Hydrolysis reactions
What are polymers broken down into?
Monomers
What does a hydrolysis reaction do?
Breaks chemical bonds between monomers using a water molecules
What test do you use to test for sugars?
Benedict’s test
What is sugar a general term for?
Monosaccharides and disaccharides
What are all sugars classed as?
Reducing or non-reducing
What does reducing sugars include?
All monosaccharides (eg glucose) And some disaccharides (eg maltose and lactose)
How to test with Benedict’s reagent (which is blue)
Add it to a sample and heat it in a water bath that’s been brought to a boil
What happens if the test is positive?
It will form a coloured precipitate (solid particles suspended in the solution)
The colour precipitate changes from?
Blue > green> yellow >orange > brick red
Th higher the concentration of reducing sugar?
The further the colour changes
-can use to compare the amount of reducing sugar in different solutions
What’s a more accurate way to compare the amount of reducing sugars in a solution?
Filter the solution and weight the precipitate
Could there’s still be non-reducing sugars present if the Benedict’s test for reducing sugars is negative?
Yes
How to test for non-reducing sugars?
1) break down into monosaccharides (get new sample of test solution, adding dilute hydrochloride acid and heat in water bath until brought to a boil
2) neutralise it with sodium hydrogen-carbonate
3) carry out Benedict’s test like you would die reducing sugars
If test is positive for non reducing sugars what happens?
Forms coloured precipitate (as for reducing sugars test)
If test negative for non-reducing sugars what happens?
The solutions stays blue, meaning it doesn’t contain any sugar (either reducing or non-reducing
What are polysaccharides?
Loads of sugars joined together
How is a polysaccharide formed?
When more than two monosaccharides are joined together by condensation reactions
Starch is what in plants?
The main energy storage material
-plants store excess glucose as starch
What is starch a mixture of?
Two polysaccharides of alpha-glucose -amylose and amylopectin
Amylose is what?
A long, unbranched chain of a-glucose
What’s the structure of amylose like?
Angles of glycosidic bonds give it a coiled structure
Makes it compact so really good for at storage because you can fit more in a small space
Amylopectin is what?
A long, branched chain of a-glucose
Amylopectin structure?
Side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily
Means glucose can be released quickly
About starch
- It’s insoluble in water
- It doesn’t affect water potential so doesn’t cause water to enter cells by osmosis which would make them swell
- makes it good for storage
What test do you used to test for starch?
The iodine test
How to test for starch?
Add iodine dissolved in a potassium iodide solution to the test sample
Is starch is present what happens?
The sample changes from browny-orange to a dark blue-black colour
What’s the main energy storage material in animals?
Glycogen
whats excess glucose stored as?
Glycogen
what is glycogen?
polysaccharide of alpha glucose
whats the structure of alpha glucose like?
Similar to amylopectin except has loads more side branches coming off of it
- loads of branches means stored glucose can be released more quickly
- very compact = good for storage
whats a major component of cell walls in plants?
cellulose
whats cellulose made of?
Long, unbranched chains of beta-glucose
- when beta-glucose molecules bond they form straight cellulose chains
- these chains are linked together by hydrogen bonds to form strong fibers called microfibrils
what does the strong fibers in cellulose structure mean cellulose is good for?
providing structural support
