Section 1- biological molecules

get a hint

hint

what is the basic unit and polymer of a carbohydrate called

what is the basic unit and polymer of a carbohydrate called

sugar unit called monosaccharide and polymer called polysaccharide

monosaccharide

-sweet tasting

-general formula of (CH2O)n

alpha and beta glucose

testing for reducing sugars

-add 2cm3 of sample to test tube and grind it up

-add equal volume of benedict’s solution to the test tube

-gently heat solution for 5 minutes

-if there is a colour change from blue to orange then reducing sugars are present

disaccharides - examples

glucose+glucose = maltose

glucose+fructose=sucrose

glucose+galactose=lactose

disaccharides - bonding

form a condensation reaction resulting in a glyosidic bond and a side product of water

adding water will form the two original monosaccharides and this a hydrolysis reaction

testing for nonreducing sugars

-add 2cm3 of sample to test tube and grind it up

-add equal volume of benedict’s solution to the test tube

-gently heat solution for 5 minutes

-if there is a colour change from blue to orange then reducing sugars are present

-if no colour change add dilute hcl and heat for another 5 mins, then add sodium hydrogencarbonate and test for neutral using pH paper. test using benedicts again.

polysaccharides - starch and its forms

starch is a glucose used to store glucose in plants.

-amylose is unbranched starch, with 1,4 bonds creating a helix chain

-amylopectin in branched with 1,4 bonds and 1,6 bonds, also creating a helix shape, but one that can be hydrolysed more easily to release glucose quicker.

polysaccharides - starch and its properties

-helix coiled structure so is compact and can store lots of glucose

-insoluble so wont move out of the cell

-doesn’t affect water potential of the cell

-large structure so doesn’t diffuse out of the cell

testing for starch

add iodine to a 2cm3 sample

shake or stir

the orange iodine will change to blue-black if the starch is present inside the sample

polysaccharides - glycogen form and properties

-known as animal starch, stores a glucose within animals

-very highly branched so can hydrolyse lots of glucose quickly.

-insoluble so doesn’t affect the water potential of the cell

-large molecule so doesn’t diffuse out of the cell

-compact so easily stored

-more branched than starch

cellulose - forms and properties

-cellulose is b glucose and used in cell walls.

-forms straight ,unbranched chains and then the layers are joined together y hydrogen bonds

-hydrogen bonds help to strengthen the cellulose making it god for its function of cell walls.

lipids - roles and properties

• insulation as they’re not god heat conductors

• waterproofing as they’re insoluble

• energy sources

• protection around vital organs

• only carbon hydrogen and oxygen

• insoluble in water but soluble in organic solvents

triglycerides

• made from three fatty acids (COOH) and one glycerol molecule (CH2OH)

  • fatty acids and glycerol form a glyosidic bond with condensation reaction

structure of triglycerides related to function

• high ratio of carbon to hydrogen bonds to carbon atoms so they produce lots of energy

• low mass to energy ration so good storage molecule

• insoluble so don’t affect water potential of the cells

• release water when oxidised so a good water source

phospholipids structure

• the same as triglycerides but with a phosphate molecule instead of a fatty acid

• hydrophobic tail of fatty acids

• hydrophilic phosphate head

  • used in cell membranes

lipids test

• add the sample to test tube

• add ethanol to same along with water

• shake the test tube

  • milky white emulsion at the top of the tube means lipid is present in the sample

proteins monomer and its structure

• the monomer for the protein is amino acid

  • the amino acid has a H group, a COOH group, a NH3 group and an R group

bonding in protein/poly peptide

• the bonds between amino acids are condensation

  • they remove a molecule of water and form a peptide bond

Primary structure of proteins

• amino acids react to form polypeptide chains

• these are determined by the DNA sequence coded for

• primary protein structure determines the overall function and structure

secondary structure in proteins

• the polypeptide chains fold and form hydrogen bonds

  • the hydrogen bonds start to form a coil or pleated beta sheet structure within the polypeptide chains

tertiary structure in proteins

• tertiary structure is when the 3D structure begins to form

• there are three main bonds which cause this:

• disulphide bridges - fairly strong so not easily broken

• hydrogen bonds- lots of these but easily broken

  • ionic bonds - form between the COOH and NH3 groups not involved in the reaction. these are weaker than disulphide and easily broken by changes in pH

Quaternary structure of proteins

• these are when many polypeptide chains join together and form more complex structures.

test for proteins

• add biuret to a warmed sample of proteins

  • if present, the solution will turn from blue to purple

nucleotide structure and bonding

• a nucleotide is made up of a pentose sugar, a phosphate group and nitrogen bases: CTUAG

• the components of a nucleotide join together through a condensation reaction to form a mononucleotide

  • mononucleotides join together to form a phosphodiester bonds, resulting in a dinucleotide or polynucleotide

RNA

• called ribonucleic acid

• pentose sugar is a ribose sugar

• bases are CGUA

• used to transfer genetic info from DNA to ribosomes

• used for protein synthesis

• used in ribosomes along with proteins

DNA

• pentose sugar is a deoxyribose sugar

• bases are ATCG

• double stranded with hydrogen bonds connecting the complimentary bases

• double helix twisted structure

stability of DNA

• the cytosine and guanine bonds have a triple hydrogen bond so the more C-G bonds there are, the more stable

• the phosphodiester bonds acts as a backbone for the helix and protects more chemically reactive bases

function of DNA

• stable structure so limited number of mutations occur

• two separate strands only joined by hydrogen bonds so easy to separate for DNA replication

• large molecule carrying lots of info but the helix coil means it is compact

• base pairing allows for DNA replication

• strong phosphodiester backbone protects DNA from outside forces

two types of cell division

• nuclear division which is the nucleus dividing (mitosis and meiosis)

  • cytokinesis is the division of the cell

semi conservative replication

• the enzymes DNA helicase works its way through the strand, hydrolysing the hydrogen bonds and unwinding DNA

• the free nucleotides use complimentary base pairing to match up and form new strands.

• DNA polymerase works to join the new strands from the nucleotides connected to the original strand

  • the 2 new strands consist of one original strand and one new strand, meaning the strands are semi conserved

equation for ATP to store energy

ATP + H2O → ADP + Pi + Energy

synthesis of ATP

• production of atp is a reversible reaction.

• the atp molecule can be condensed to form adp again

  • atp has a low activation energy so energy can quickly and easily be released from this process

roles of ATP

• immediate energy source, each ATP molecule releases less energy than a glucose molecule so the energy is being released in more manageable loads. it is also a lot quicker than hydrolysing all the ends of the glucose storage

• metabolic processes to build up molecules from their monomers such as starch and cellulose

• movement in muscle contraction

• active transport of substances in processes such as digestion

  • activation of molecules as ATP is used to overcome the activation energy of a reaction

Water and its functions

• polar molecule

• hydrogen and oxygen in the water bond so the molecule ‘stick’ together and form unusual properties

• the specific heat capacity of water is high as the bonds require lots of energy in order to break them

• same with latent heat of vaporisation

  • high surface tension

water in living organisms

• used in metabolic processes to do hydrolysis

• a solvent for gases and enzymes

• evaporates to cool organisms

inorganic ions

• phosphate molecules in DNA and lipids

• hydrogen ions for determining the pH of solutions and therefore the use of enzymes

  • sodium ions are important in the cotransport of glucose and amino acids