Carbohydrates Flashcards
(21 cards)
2 forms of glucose
-alpha + beta
-isomers
3 major polysaccharides
-starch, glycogen and cellulose
The shape of glucose
-sugars with 6 carbon atoms = hexose
-monosaccharide
-glycosidic bonds - 1’4, 1’6 bonds
-condensation join + H2O up
-galactose + fructose
Properties of monosaccharides
-soluble in water
-contains lots of OH groups - they form H bonds with water molecules
Pentose monosaccharides
-contain 5 carbons
-eg. Ribose + deoxyribose
-form RNA and DNA
Formation of disaccharides + polysaccharides
-monosaccharides can be chemically joined to form larger carbs
The 2 isomers
-beta - OH at top
-alpha - OH at the bottom
What is a disaccharide?
-2 glucose molecules reacting together
-also form water - from a H from one, and a OH from another
-condensation
What is maltose made of?
2 alphas
What is sucrose made from?
Glucose + fructose
What is lactose made from?
Glucose + galactose
What is a glycosidic bond?
-chemical bond between 2 molecules of glucose
-carbon 1’4 glycosidic bond
-if water is added to DS - GS bond is broken
-converts back into OG MS
(Hydrolysis)
What is starch made from?
-contains dissolved glucose - water moves in - plant stores starch
-grains are found in plastids - chloroplasts + colourless amyloplast
-2 molecules; amylose + amylopectin
-when cells need glucose - water is used to break GS bonds
What is amylose made of?
-polymer of alpha
-lots of alpha = polysaccharide chain of amylose
-can twist into helix = H bonds form between glucose along the chain
Why can’t amylose + amylopectin diffuse through a cell membrane?
-too large
Structure of starch
-amylopectin - polymer of alpha with branches every 25-30 glucose molecule
-branch connected to main chain by GS bond - 1’6
Why do we need starch?
-need glucose - enzymes break GSB in starch - hydrolysis - needs water
-enzyme breaking down starch acts at end of molecule
-lots of branches = lots of ends = enzyme can break down starch quickly
What is glycogen?
-animal store of glucose
-in liver + muscle cells
-polymer of alpha 1’4 - contains branches 1’6
-more branched than amylopectin = compact
-insoluble in water - doesn’t draw water in
Importance of glycogen
-lots of free ends - enzymes convert glycogen to glucose fast
-high rate of respiration - sudden spike - glycogen can be converted to glucose to be used
What is cellulose?
-polymer of beta glucose -OH on top
-can’t form between 1’4 - every 2nd beta is flipped
-unbranched polysaccharide - no branches - can be close together
-H bonds can form between neighbouring chains = strong
Grouping of cellulose
-(microfibril) - group together to make large microfibrils
-group make a cellulose fibre = plant cell wall
-impermeable to molecules
