Biological Molecules - AS

Biological Molecules notes

Carbohydrates

• These contain: Carbon, Hydrogen and Oxygen.

• In Carbohydrates the basic monomer is sugar (saccharide)

• Monosaccharide: Simplest form of sugar, that can’t be hydrolyzed into a simpler form.

• EG: Fructose, Galactose, Beta and Alpha Glucose, amino acids

• These are reducing sugars

• Joined by a glycosidic bond

• Soluble in water and sweet tasting (form crystals)

• Disaccharide: A pair of sugars, can be hydrolyzed into simpler forms.

• EG: Sucrose, Lactose, Maltose

• Polysaccharide: Many Monomers combined. Can be hydrolyzed.

• EG: Starch, Glycogen, Cellulose

Glucose: This is a monosaccharide

There are two types of glucose:

Alpha Glucose

Beta Glucose

TEST FOR REDUCING SUGARS (MONOSACCHARIDES)

• Add benedict's solution

• Put into a water bath

• If it is a reducing sugar it will turn a BRICK RED

• ( SOME disaccharides are reducing sugars too)

Condensation and Hydrolyzation

• Condensation: The joining of molecules with a formation of a Chemical Bond, this includes the loss of a water molecule (H2O)

• Hydrolyzation: The process in which a water molecule (H2O) is added to a substance, which causes it to split into separate molecules.

Maltose

• This is a disaccharide (so it is joined by a glycosidic bond).

• It is composed by two Alpha Glucose molecules.

Disaccharides

• Alpha glucose  + fructose -> sucrose

• Alpha glucose + galactose -> Lactose

TEST FOR NON- REDUCING SUGARS (SUCROSE)

• Hydrolyze the sugar in HCL(to hydrolyse the glycosidic bonds)

• Neutralise the solution using sodium hydrogen carbonate

• Add benedict's solution and heat in a water bath

Polysaccharides

• These are formed by the condensation of glucose units.

• (Glycogen and Starch are formed by condensation of alpha)

• (Cellulose is formed by the condensation of beta glucose)

• Polysaccharides are polymers (chains of monosaccharides)

• Monosaccharides join together by glycosidic bonds formed by condensation reactions.

• These are large molecules- insoluble- good storage molecules.

• These break down into disaccharides and polysaccharides.

Starch

• Used in plants as a storage molecule. needed for when plants cannot photosynthesise (short term), needed for winter (allow seeds and bulbs to survive (long term)

• Polysaccharide (many disaccharides joined)

• This is a type of Polysaccharide.

• Found in plants.

• Mixture of amylose and amylopectin

• Amylose (1-4 glycosidic links)  has a linear (straight)  and helical (spiral)  structure .

• This is so that a large amount can be stored in a small space, because it is easily compacted. This is good for starch storage.

• Amylopectin is highly branched, so that it has a larger surface area. This means enzymes can reach is quickly and break down the glycosidic bonds into glucose.

• These are both made from lots of a- glucose molecules in a series of condensation reactions.

• It is insoluble-  maintain water potential (no osmosis)

• It is a large molecule - Can’t get out of the cell

• Helical - Can store a large amount in small space

• Branched - Surface area- glycosidic bonds broken by enzymes quickly (easily synthesised).

THE TEST FOR STARCH

• Put it in iodine solution

• If it is present- blue black colour

Glycogen

• Animals make glucose into glycogen (rather than starch).

• Glycogen is made from a-glucose (1-4…