biological molecules Flashcards
what 3 elements make up carbohydrates?
carbon, hydrogen and oxygen
what 3 structures do carbohydrates exist in?
monosaccharides, disaccharides and polysaccharides.
monosaccharides
small chain molecules, soluble
examples of monosaccharides
glucose, galactose and fructose
disaccharides
2 monosaccharides
3 types of disaccharides
maltose (2 glucose)
sucrose (glucose + fructose)
lactose (glucose + galactose)
what are polysaccharides?
they are polymer containing many monosaccharides linked by glyosidic bonds.
features of glucose
it is a hexose (6 carbon) sugar.
formula of glucose
C6H12O6
are monosaccharides reducing sugars?
Yes, they all are, as they can donate an electron to another chemical.
what happens when a reducing sugar is in water?
the ring open up to display a free ketone or aldehyde group, this donates an electron and thus reduces the Benedict’s solution.
what is a condensation reaction?
joining of molecules to form chemical bonds, excluding water
it allows the formation of disaccharide molecules and eventually polysaccharide molecules.
how are polysaccharides formed?
through a condensation reaction
what are polysaccharides used for?
used as energy stores and as structural components of cells.
examples of polysaccharides
starch and cellulose in plants, and glycogen in animals.
features of starch
found in plants
helical structure
compact, can be hydrolysed back into alpha glucose for respiration
insoluble, cannot effect water potential
starch test
add iodine, if present turns blue-black
feature of glycogen
highly branched with 1-4 and 1-6 glycosidic bonds
broken down for respiration, storage molecule
animal cells, polymer of alpha glucose
features of cellulose
polymer of beta glucose
hydroxyl groups can form hydrogen bonds with other molecules
forms fibrils, provides strength for plant cell walls
straight chained 1-4 glycosidic hydrogen bonds
Benedict’s test for reducing sugars
reducing sugars= monosaccharides
1. test tube, add blue Benedict’s reagent, heat
2. reducing sugar goes brick red, negative stays blue
3. add Hal, boil to hydrolyse non-reducing sugar, add sodium hydrogen carbonate, do Benedict’s test again, positive result= non-reducing sugar
features of lipids
main functions= insulation, energy storage, protection
types of lipids
triglycerides (known as true fats or natural fats) and also waxes, steroids and cholesterol.
test for lipids
dissolve sample with ethanol
add water
lipid present= cloudy white emulsion
features of triglycerides
condensation of 3 fatty acids + 1 glycerol (forms ester bonds)
high ratio of C-H to C-C bonds= energy storage
metabolic water source (high ratio H-O atoms)
insoluble, no affect of water potential
low mass