Carbohydrates Flashcards
What are carbohydrates?
Polymers
What are the monomers of carbohydrates called and give some examples?
Monosaccharides.
e.g. typically sugars :
glucose, fructose, galactose
How is glucose useful?
Used in cellular respiration to make ATP ; using oxygen alongside.
What happens when you combine two monosaccharides give some examples.
You make a disaccharide.
e.g. sucrose, maltose, lactose
What is the name for many monosaccharides?
A polysaccharide
How are disaccharides formed?
They are formed from two monosaccharides joined together by a glycosidic bond formed by a condensation bond.
What are the equations for the 3 known disaccharides?
glucose + glucose —> maltose + water
glucose + galactose —> lactose + water
glucose + fructose —-> sucrose + water
What type of glycosidic bonds are disaccharides formed from?
1-4 glycosidic bond ( bond between carbon 1 and carbon 4)
What catalyses hydrolysis in the body?
Enzymes
During which process are carbohydrates hydrolysed into the body as monomers?
Glycogenolysis - store of glycogen hydrolysed back into glycogen when blood sugar levels drop.
Digestion - when starch is hydrolysed into glucose
How are carbohydrates important to an organism, the structure, and function of its cells?
To make cells through cellulose, fungi use it to make cell walls through chitin.
What is starch?
Starch is used as an energy store in plant cells. It is a polysaccharide of a - glucose.
Structure : Amylase - 1,4 glycosidic bonds —> unbranched
Amylopectin - 1,4 and 1,6 glycosidic bonds —–> branched.
What is glycogen?
Glycogen is used as an energy store in animal cells. It is a polysaccharide made of a-glucose. It has 1,4 and 1,6 - glycosidic bonds —-> branched.
How does the structure of starch ( amylase) relate to its function?
Starch ( amylase ) has a helical structure, making it compact for cell storage.
It is a large, insoluble polysaccharide molecule, can’t leave the cell / cross-cell membrane
Insoluble in water, the cell’s water potential is not affected ( no osmotic effect ).
How does the structure of glycogen ( and starch amylopectin ) relate to its function?
It is branched, making it compact/ to fit more molecules in a small area.
Branched, more ends for faster hydrolysis - release glucose for respiration to make ATP for energy release.
Large, insoluble polysaccharide molecules, cant leave cell / cross-cell membranes.
Insoluble in water, water potential of cell not affected ( no osmotic effect ).
What is cellulose?
Provides strength and structural support to plant/algae cell walls.
It is a polysaccharide of beta-glucose.
1,4 glycosidic bond —> straight, unbranched chains.
Chains are linked in parallel by hydrogen bonds forming microfibrils.
How does the structure of cellulose relate to its function?
- Every other beta-glucose molecule is inverted in a long, straight, unbranched chain.
- Many hydrogen bonds link parallel strands ( crosslinks ) to form microfibrils ( strong fibrils).
- Hydrogen bonds are strong in high numbers.
- So provides strength to plant cell walls.
Describe the test for reducing sugars.
Reducing sugars = monosaccharides, maltose, lactose
1. Add Benedict solution ( blue ) to the sample.
2. Heat in a boiling water bath.
3. Positive result = green/yellow/orange/red precipitate.
Describe the test for non-reducing sugars.
Non-reducing sugars = sucrose.
1. Do Benedict’s test and stays blue/negative.
2. Heat in a boiling water bath with acid ( to hydrolysed into reducing sugars ).
3. Neutralise with alkali ( e.g. sodium bicarbonate ).
4. Heat in a boiling water bath with Benedict’s solution.
5. Positive result =green/yellow/orange/red precipitate.
Suggest a method to measure the quantity of sugar in a solution.
- Carry out the Benedict’s test as above, then filter and dry precipiate.
- Find mass/weight.
Describe the biochemical test for starch.
Add iodine dissolved in potassium iodide (orange/brown) and shake/stir
Positive result = blue/black.
