foundations in biology - biological molecules

why is water polar

the O atoms attract more electrons making them slightly negative whereas the H atoms have a slight positive charge

hydrophilic

a molecule that is attracted to water. these molecules are either charged or polar and can dissolve in water. e.g. salt or glucose

hydrophobic

a molecule that is repelled by water. these molecules are non polar and cant dissolve in water. e.g. oil

what is a hydrogen bond

a weak interaction that can occur wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom

10 properties of water

liquid at room temperature

high latent heat of evaporation

high specific heat capacity

low density of ice

cohesion

adhesion

surface tension

water acts as a solvent

water is transparent

reactant

biological molecules =

carbon based molecules that make up living organisms

elements present in carbohydrates

carbon

hydrogen

oxygen

elements present in proteins

carbon

hydrogen

oxygen

nitrogen

sometimes sulfur

elements present in nucleic acids

carbon

hydrogen

oxygen

nitrogen

phosphorus

elements present in lipids

carbon

hydrogen

oxygen

mono

1

di

2

poly

many

sacchar

sugar

polymer

is a large molecule made from many smaller repeating molecules of the same monomer

polymerisation

formation of a polymer

monomer

a small molecule which binds to many other identical molecules to form a polymer

dimer

2 monomers joined together

polymer

a large molecule made from many smaller molecules called monomers

sharing one pair of electrons

single covalent bond

sharing 2 pairs of electrons

double covalent bonds

condensation reaction

removal of water to make polymer

hydrolysis reaction

addition of water to split polymer

functions of carbohydrates

energy source e.g. glucose

energy store e.g. starch or glycogen

structure e.g. cellulose in plant cell walls

also part of other molecules such as nucleic acids, glycoproteins, glucolipids

why are carbohydrates called hydrated carbon

in monosaccharides there are 2 hydrogen atoms and one oxygen for every one carbon in the structure (ch2o)n

monosaccharides single sugars

glucose - 6c (hexose)

ribose - 5c(pentose)

monosaccharides key features

simplest carbohydrate with single sugar units

important as an energy source (C-H bonds)

have between 3-7 carbon atoms

sweet tasting

soluble in water but insoluble in non polar solvents

disaccharide double sugars

sucrose - alpha glucose + fructose

maltose - alpha glucose + alpha glucose

lactose - alpha glucose + galactose

polysaccharide chains of many sugars

starch - lots of alpha glucose

glycogen - lots of alpha glucose

cellulose - lots of beta glucose

whats the difference between a hexose and pentose monosaccharide

in a hexose sugar theres 6 carbons but in a pentose sugar theres 5 carbons

name of monosaccharides that make up maltose

alpha glucose + alpha glucose

name of monosaccharides that make up sucrose

alpha glucose + fructose

name of monosaccharides that make up alpha lactose

(beta) galactose + alpha glucose

name of monosaccharides that make up beta lactose

(beta) galactose + beta glucose

name of monosaccharides that make up cellubiose

beta glucose + beta glucose

what type of reaction breaks up a polysaccharide into a disaccharide

hydrolysis

what type of reaction forms a disaccharide from monosaccharides

condensation

alpha glucose role in body

energy source

component of starch and glycogen which acts as energy stores

beta glucose role in body

energy source

component of cellulose which provides structural support in plant cell walls

ribose role in body

component of ribonucleic acid (RNA), ATP, and NAD

deoxyribose role in body

component of deoxyribonucleic acid (DNA)

key features of polysaccharides

made up of 100s or 1000s of repeating monosaccharide subunits

formed by repeated condenssation reactions

can be broken down by hydrolysis using enzymes

polysaccharides are not sugars and dont taste sweet

polysaccharides are insoluble in water

to break down starch you need

amylase to break down = 1,4 glycosidic bonds and

glucosidase to break down = 1,6 glycosidic bonds

amylose function

energy store in plants

amylose structure

unbranched

polysaccharide twists to form helix

amylose glycosidic bonds

alpha - 1,4 glycosidic bonds only

amylose extra detail

hydrogen boding present within structure for further stabilisation

compact

can store a lot of glucose in a small space

amylopectin function

energy store in plants

amylopectin made of

alpha glucose

amylopectin structure

polysaccharide chains coiled into helix

branching present

amylopectin glycosidic bonds

alpha - 1,4 and 1,6

amylopectin extra details

hydrogen bonding present within structure for further stabilisation

compact

greater surface area for enzyme action and therefore more rapid hydrolysis

glycogen made of

alpha glucose

glycogen structure

polysaccharide chains coiled into helix

lots of branching present(far more than amylopectin) and more alpha - 1,6 glycosidic bonds

glycogen glycosidic bonds

alpha 1,4 and 1,6

glycogen extra detail

hydrogen bonding present within structure for further stabilisation

compact

highly branched

can be very rapidly hydrolysed

more branches = more ends = more hydrolysis = more glucose for energy (respiration)

describe the importance of polysaccharides being insoluble

polysaccharides act as energy storage molecules

by being large and insoluble it means that they are able to perform such structural roles without being dissolved in cytoplasm

why is glycogen a good storage molecule

insoluble

does not affect water potential

can be broken down quickly by hydrolysis

lots of branches

compact

high energy content for mass

is amylose humans or plants

plants

where is amylose stored

starch grains in plant cells vacuole

is amylose a form of starch

yes

whats the monomer of amylose

alpha glucose

is amylose branched

no

is amylose soluble

no

what type of glycosidic bonds does amylose have

alpha - 1,4

is amylose spiralled

yes

are H bonds important in amylose

yes

is amylopectin humans or plants

plants

where is amylopectin stored

starch grains in plant cells vacuole

is amylopectin a form of starch

yes

what is the monomer of amylopectin

alpha glucose

is amylopectin branched

yes

is amylopectin soluble

no

what type of glycosidic bonds does amylopectin have

alpha - 1,4 and 1,6

is amylopectin spiralled

yes

are H bonds important in amylopectin

yes

is glycogen humans or plants

humans

where is glycogen stored

glycogen granules in cells like the liver

is glycogen a form of starch

no

what is the monomer of glycogen

alpha glucose

is glycogen branched

yes

is glycogen soluble

no

what type of glycosidic bonds does glycogen have

alpha - 1,4 and 1,6

is glycogen spiralled

yes

are H bonds important in glycogen

yes

role of cellulose

to provide structure, has a high tensile strength, insoluble, unreactive and inflexible

where is cellulose found

in a plant cell wall

what is cellulose

a structural carbohydrate

what is cellulose made of

beta glucose

what do we use cellulose as

a fibre source

what glycosidic bonds does cellulose have

beta - 1,4

why is cellulose not spiralled

has inverting alternate beta glucose molecules which prevent spiralling

H bonds exist between glucose molecules within the same chain

H bonding exists between glucose molecules in different chains

how is cellulose packed into fibres in the cell wall

• around 60 cellulose chains become cross linked by hydrogen bonds to form microfibrils

• microfibrils are held together by further hydrogen bonds to form microfibrils and groups of microfibrils combine to form fibres

• pectin acts like glue

whats the role of chitin

functions as a structural polysaccharide forming insect and crustacean exoskeletons and fungi cell wall

forms long parallel chains of acetyleosein in similar ways to cellulose

whats the structure of chitin

has an acetylamino group rather than a hydroxyl group on C2

whats the role of peptidoglycan

bacterial cell walls

whats the structure of peptidoglycan

this is made from long polysaccharide chains that lie in parallel, cross linked by short peptide chains

where do lipids come from

animals and vegetable sources

what aren’t lipids like proteins and carbohydrates

polymers

what elements do lipids contain

carbon

hydrogen

oxygen