carbohydrates Flashcards
What is a monomer
Small units which larger molecules are made
What is a polymer
many monomers join together by a condensation reaction
E.g polysaccharides proteins DNA/RNA
What is a condensation reaction
A chemical bond is formed between 2 molecules and it involves the elimination of a water molecule
What is a hydrolysis reaction
A water molecule is used to break a chemical bond between 2 molecules
What is a monosaccharide
Monomers which larger carbohydrates are made
Give examples of monosaccharides
Glucose fructose galactose
A condensation of 2 monosaccharides form a what
Glycosidic bond
How is a disaccharide formed
2 monosaccharides joined together forming glycosidic bond
Formed by a condensation reaction, releasing a water molecule
What is a polysaccharide
Formed by the condensation of many glucose units(many monosaccharides)
Joined together by glycosidic bond releasing water molecule
How is glycogen and starch formed
By the condensation of alpha glucose
Glucose + glucose
Maltose
Glucose + fructose
Sucrose
Glucose + galactose
Lactose
Explain how the structures of starch relate to their functions
● Helical → compact for storage in cell
● Large, insoluble polysaccharide molecule → can’t leave cell membrane
● Insoluble in water → water potential of cell not affected
Explain how the structure of glycogen relate to their function
● Branched → compact to fit more molecules in small area
● Branched → more ends for faster hydrolysis → release glucose for respiration to
make ATP for energy release
● Large, insoluble polysaccharide molecule → can’t leave cell membrane
● Insoluble in water → water potential of cell not affected
Explain how the structure of cellulose relates to its function
● Every other β-glucose molecule is inverted in a long, straight, unbranched chain
● Many hydrogen bonds link parallel strands to form microfibrils (strong fibres)
● Hydrogen bonds are strong in high numbers
● So provides strength to plant cell walls
What’s the Benedict’s test for reducing sugars
-add Benedict’s reagent to a sample and heat in water bath
-if positive it turns blue to red precipitate
What is the test for non reducing sugars
- Do Benedict’s test and stays blue / negative
- Heat in a boiling water bath with acid (to hydrolyse into reducing sugars)
- Neutralise with alkali
- Heat in a boiling water bath with Benedict’s solution
- Positive result = red precipitate
Describe the biochemical test for starch
Add iodine
Positive result is a colour change orange to blue-black
Describe the basic structure of starch
● Polysaccharide of α-glucose
● Amylose - 1,4-glycosidic bonds → unbranched
● Amylopectin - 1,4- and 1,6-glycosidic bonds → branched
Describe the basic structure of cellulose
● Polysaccharide of β-glucose
● 1,4-glycosidic bond → straight, unbranched chains
● Chains linked in parallel by hydrogen bonds forming microfibrills
Basic function of starch
Energy store in plant cells
Basic function of cellulose
to strengthen cell wall of plant and algae cell wall
basic function of glycogen
Energy store in animal cells
