Carbohydrates Flashcards
(26 cards)
What monomers are carbohydrates made of and what elements do they include?
Carbohydrates are made of the elements carbon, hydrogen, and oxygen. The monomers they are made from are monosaccharides.
What are 3 examples of monosaccharides?
Glucose, fructose, and galactose.
What is meant by glucose, fructose, and galactose being isomers?
They have the same molecular formulae but a different arrangement of atoms in a space.
How are disaccharides formed?
Disaccharides are formed by the condensation of 2 monosaccharides, forming a glycosidic bond.
What are 3 examples of disaccharides and their word equations?
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
What are the two isomers of glucose?
Alpha-glucose : HOH
Beta-glucose : OHH
How are polysaccharides formed?
Polysaccharides are formed by the condensation of many glucose monomers.
What are 3 examples of polysaccharides?
Starch, glycogen, and cellulose.
What is the importance of starch?
Starch is the main carbohydrate storage in plants.
How is starch formed?
Starch is formed by the condensation of alpha glucose which forms amylose and amylopectin.
What is the structure of amylose?
Amylose is an unbranched, helical polymer of alpha glucose. It gets its helical structure from the bond angles of the glycosidic bond.
What is the structure of amylopectin?
Amylopectin is a long, branched polymer of alpha glucose.
How does the structure of starch relate to its function?
Starch is compact due to the helical structure of amylose so lots of glucose can be stored in a small space, making it an efficient energy store.
Starch contains many branches in amylopectin which increases the number of points where enzymes can attach allowing for rapid hydrolysis back to glucose.
Starch is insoluble meaning it doesn’t affect water potential, so water isn’t drawn into or out of cells by osmosis.
What is the importance of glycogen?
Glycogen is the main energy storage in animals.
What is the structure of glycogen?
Glycogen has the same structure as amylopectin, but it has more branches.
How does the structure of starch relate to its function?
Glycogen contains many branches which increases the number of points where enzymes can attach allowing for rapid hydrolysis back to glucose.
Glycogen is compact so lots of it can be stored in a small space, making it an efficient energy store.
Starch is insoluble meaning it doesn’t affect water potential, so water isn’t drawn into or out of cells by osmosis.
What is cellulose?
Cellulose provides structure strength for cell walls in plants.
How does the structure of cellulose relate to its function?
Cellulose is made of long, unbranched chains of beta glucose which forms a straight chain. These chains run in parallel to each other and are linked by hydrogen bonds to form microfibrils. Many microfibrils are arranged in parallel groups called fibres. These fibres are laid down in a cell wall in different directions, providing tensile strength in all directions.
Hydrogen bonds also provide collective strength.
Cellulose is insoluble meaning it doesn’t affect water potential, so water isn’t drawn into or out of cells by osmosis.
What are examples of reducing sugars?
Glucose, fructose, galactose, maltose, and lactose.
What is an example of a non-reducing sugar?
Sucrose.
What is the process of testing for reducing sugars?
1) Add 2cm^3 of liquid food sample to 2cm^3 of Benedict’s reagent.
2) Heat the mixture in a water bath for 5 minutes.
A positive result is a colour change to brick-red.
What is the flow chart of the colour changes following a reducing sugars test?
Blue … Green … Yellow … Orange … Brick-red
The higher the concentration of reducing or semi-reducing sugar, the further the colour change goes.
Why is the colour change in a reducing sugars test observed?
This colour change happens because the sugars donate electrons to copper (Cu2+) ions in the Benedict’s solution, reducing them to Cu+ ions, which gives us the brick-red precipitate.
What is the process of testing for non-reducing sugars?
1) Following a negative reducing sugars test, add dilute hydrochloric acid to the mixture.
2) Boil the mixture.
3) Cool the solution and add an alkali (Sodium Hydrogen Carbonate) to neutralise the mixture and use pH paper to check.
4) Repeat Benedict’s test: add Benedict’s reagent and heat in a water bath for 5 minutes.
A positive result is an orange or brick-red colour change.
