1. Biological Molecules - Carbohydrates Flashcards
Name 3 common monosaccharides?
-Glucose
-Galactose
-Fructose
What forms a glycosidic bond?
A condensation reaction
What is maltose made from?
α-glucose + α-glucose
What is sucrose made from?
α-glucose + α-fructose
What is lactose made from?
α-glucose + β-galactose
What is the difference between α-glucose and β-glucose?
α-glucose has the OH groups in line, β-glucose has the OH groups diagonal
What causes the colour change in a benedicts test?
Blue to brick red indicates electrons have been donated to the Cu2+ ions in benedicts solution.
What is a reducing sugar?
A sugar that donates electrons.
How do you test for reducing sugars?
-Add benedicts to solution
-Heat in a water bath at 80C for 5 minute
-Record colour change
How do you test for non-reducing sugars?
-Add HCl to solution and swirl to mix
-Place in a water bath at 80C for 5 minutes
-Remove and allow to cool
-Add 2 spatulas of sodium hydrogencarbonate
Add benedicts
-Place back in water bath for 5 minutes
-Record colour change
What are the non-reducing sugars?
Sucrose and lactose
What is released during a condensation reaction?
A water molecule
What 2 things happen during a condensation reaction?
-A water molecule is released
-A new covalent bond is formed
What 2 things happen during a hydrolysis reaction?
-Water molecule is used
-A new covalent bond is broken
What are 3 polysaccharides?
Starch
Glycogen
Cellulose
What is starch made from?
α-glucose
What is glycogen made from?
α-glucose
What is cellulose made from?
β-glucose
Is starch branched or unbranched?
Both.
What is starch’s branched structure called?
Amylopectin
What is starch’s unbranched structure called?
Amylose
Which glycosidic bond(s) does starch contain?
Both 1-4 and 1-6 glycosidic bonds
What is starch in regards to it having an unbranched structure?
What is the benefit of this?
Coiled - meaning it can be compact and store a lot of energy.
What forms when starch is hydrolysed?
α-glucose
What does a branched structure of starch mean?
It means more enzymes can act upon it, allowing lots of glucose to be released quickly.
Which glycosidic bond does amylose have?
1-4 glycosidic bond
Which glycosidic bond does amylopectin contain?
1-4 and occasional 1-6 glycosidic bonds
What are the percentages of each starch structure in starch?
-20% amylose
-80% amylopectin
What is a 1-4 glycosidic bond?
A bond between carbon 1 and carbon 4.
Which carbohydrate is the energy store in plants?
Starch
Which carbohydrate is the energy store in animals and fungi?
Glycogen
What is the difference between starch and glycogen?
Glycogen does not have amylose or amylopectin, instead just a branched and unbranched structure.
What is cellulose the polymer of?
β-glucose
What does cellulose consist of (structure wise)?
Straight, unbranched chains which run parallel to one another.
Which glycosidic bond(s) does cellulose contain?
Only 1-4 glycosidic bonds.
Give 5 features of starch that makes it a good storage molecule:
-Insoluble - doesn’t affect w.p of cell
-Unbranched, coiled, compact
-Polymer of α-glucose
-Highly branched - fast breakdown and release of glucose
-Large molecule - can not diffuse out of cell easily
What forms between adjacent cellulose chains, in turn forming what?
Hydrogen bonds form between adjacent chains, forming microfibrils.
What are microfibrils?
They are the strong fibres that are made of many cellulose chains that are held together by hydrogen bonds.
What is the benefit of a carbohydrate being a polymer of α-glucose?
Can provide respiratory substrate.
What is the structure of amylose and what does this mean?
It’s helical, so compact and more can be stored in cell.
What is the function of the spherical (unbranched) structure of glycogen?
Compact, so more can be stored in cell.
What is the function of the branched structure of glycogen?
Can be hydrolysed more rapidly.
What is the function of the hydrochloric acid in a non-reducing sugars test?
To break the glycosidic bonds.
What is added to the sample after the HCl in a non-reducing sugars test?
Why?
Sodium hydrogen carbonate is added to neutralise the sample.
