Section 1- biological molecules

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