Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
|
Covalent bonding |
Atoms share a pair of electrons in their outer electron shells |
|
|
Ionic Bonding |
when ions of opposite charges attract. The electrostatic attraction is known as ionic bond |
|
|
Hydrogen bonding |
Electrons within a molecules are not evenly distributed.this is known as polar molecule. The negative regions of a molecule attracts the positive region they form not so strong bonds |
|
|
monomers |
single unit of a molecule |
|
|
polymers |
A chain of a large number of similar units bonded together |
|
|
Condensation |
When monosaccharides are joined by glycosidic bonds |
|
|
Hydrolisis |
the breaking down of polysaccharides to monosaccharides and water |
|
|
Test for reducing sugars |
Add 2cm3 of food sample in a test tube Add an equal amount of Benedictts solution Heat the mixture in gently boiling water for 5 minutes. If it changes red/brown,it is a reducing sugar |
|
|
How disaccharides are formed |
glucose +glucose=maltose glucose+fructose=sucrose glucose+galactose= lactose |
|
|
What bond joins monosaccharides together |
glycosidic bond |
|
|
Test for non reducing sugars |
Add 2cm3 of the sample being tested to a test tube add the same amount of benedictts solution place the tube in boiling water for 5 minutes if its blue,then reducing sugar is not present. Add another 2cm of the food sample to 2cm of hydrochloric acid and heat for 5 minutes slowly add some hydrogencarbonate to neutrilise the acid retest the resulting solution by heating with 2cm of benedictts solution if the reducing sgar is now present the solution will turn brown |
|
|
Test for starch |
Place 2cm3 of the substance into a test tube Add 2cm3 of iodine solution and shake /stir The presence of starch or solution is shown by a black blue solution |
|
|
What the constituents of starch |
Alpha glucose only |
|
|
Expalain why benedictt's reagent turns red when heated with a reducing sugar |
sugar denotes electrons electrons that reduce blue CuSO4 to orange |
|
|
Explain the structure of starch |
it is a polysaccharide the chains may be branched or unbranched. The unbranched chain may be wound into a tight coil to male it very compact |
|
|
Main role of starch |
It is insolube and therefore doesnt affect the water potential and water is not drawn in by osmosis being large and solube,it doesn't diffuse out of cells. It is compact and can therefore be stored in a small space when hydrolsed it can form alpha glucose |
|
|
structure of glycogen |
similar in structure to starch but shorter chains. it is highly branched |
|
|
Why glycogen is good for storage |
it is insolube and therefore doesn't draw water in by osmosis being insolube doesn't diffuse out of cells it is compact and therefore can be stored in a small space it is highly branched and therefore can be acted upon simultaneously by enzymes. |
|
|
Cellulose |
it is made up of beta glucose instead of alpha glucose it has straight unbranched chains They form cross linkages between adjacent chains. |
|
|
Cellulose provide in rigidity and support because |
they are made up of beta glucose so form straight, unbranched chains these cellulose chains run parallel to each other and are cross linked by hydrogen bonds which add collective strength they are grouped to form micro fibrils which are in turn grouped to form fibres which provide more strength |
|
|
Lipids (properties) |
they are insoluble in water soluble in solvents they contain hydrogen,carbon and oxygen |
|
|
Role of lipids |
Source of energy:when oxidised they produce twice as much energy as the same mass of carbohydrates an release valuable water waterproofing:they are insoluble in water and therefore act as a waterproofing Insulation: they are slow conductors of heat when stored beneath the body and help to retain heat Protection:fat is stored around delicate organs . |
|
|
Structure of triglyceride |
They are made of three fatty acids and one glycerol molecule All different fatty acids have a carboxyl group |
|
|
How their structure of triglyceride relate to their |
They have low mass to energy ratio making them good storage molecules Being large,non polar molecules triglyceride are insoluble in water.As a result they don't affect osmosis in cells or their water potential |
|
|
Structure of phospholipids |
They are similar to lipids except that one of the fatty acids is replaced by a phosphate molecule A hydrophilic head:Interacts with water but not with fat A hydrophobic tail:which orients itself away from water but mixes readily with fat |
|
|
How the structure of phospholipids relate to their properties |
They create a hydrophobic barrier between the inside and the outside of a cell The hydrophilic head head helps to hold the surface of the cell surface membrane their structure allows them to form glycolipids by combining with carbohydrates within the cell surface membranes |
|
|
Test for lipids |
Take a grease free test tube to a sample of 2cm3 add 5cm3 of ethanol shake it vigourously to dissolve any lipid in the sample add 5cm3 of water and shake gently a cloudy white colour indicates the presence of a lipid As a control,repeat the same procedures using water instead of the sample.the solution remained clear |
|
|
Structure of an amino acid |
They are made of amino group-NH2 carboxyl group-_COOH hydrogen group -H R group |
|
|
what is the bond that holds amino acids together? |
A peptide bond by condesation |
|
|
The primary structure of proteins |
when many polymers of amino acids come together they form polypeptides |
|
|
Secondary structure of proteins |
The linked amino acids posses both -NH and C=O.These groups therefore readily form weak bonds called hydrogen bonds. This causes long polypeptide chains to be twisted into a a 3D shape known as an alpha helix |
|
|
Tertiary structure |
The alpha helix can be twisted and folded to give a complex 3D protein structure of each protein This structure is maintained by a number of bonds namely disulfide bonds ionic bonds;formed between any carboxyl and amino groups that are not involved in forming peptide bonds Hydrogen bond;which are numerous but easily broken |
|
|
Quaternary structure |
Large proteins often form complex molecules containing a number of individual polypeptides linked in various ways |
|
|
Test for proteins |
Place the solution to be tested in a test tube and add an equal volume of sodium hydroxide solution at room temperature Add a few drops of dilute copper 2 sulphate and mix gently A purple colouration indicates the presence of peptide bonds hence a protein. |
|
|
what are enzymes?
|
Enzymes are globular proteins that act as catalysts
|
|
|
For a reaction to take place:
|
the substrates must collide with enough energy to alter the arrangement of their atoms in order to form the products The free energy of the products must be less than that of the substrates The minimum amount of energy needed to kick-start the reaction should be availabe |
|
|
Enzyme structure
|
specific region of an enzyme that is functional is the active site The molecule on which the enzyme acts on is known as the substrate The substrate and the enzyme form a substrate enzyme complex |
|
|
The induced fit model
|
It suggests that the enzyme has a general shape that alters in the presence of a substrate The enzyme is flexible and can mould itself around the substrate.As it changes its shape,it puts a strain on the substrate molecule. The strain distorts the bond in the substrate molecule and this subsequently lowers the activation energy needed to break the bond |
|
|
Effect of temperature on enzyme action |
A rise in temperature increases the kinetic energy of the molecules.There will be more successful collisions between the substrate and the enzymes.More enzyme substrate complexes will be formed. The rate of reaction will increase If the temperature increases even further the hydrogen and other bonds will be destroyed and the enzyme will be denatured such that the substrate won't fit in the active site any more |
|
|
Effect of pH on enzyme action |
A change in the pH away from the optimum affects the enzyme action If the change is extreme,it denatures the enzyme.it does this by: A change in the pH alters the charges on the amino acids that make up the active site of the enzyme,as a result the substrate can not fit and no enzyme -substrate complexes are formed |
|
|
Effect of enzyme concentration on the rate of reaction |
As long as there is excess substrate,an increase in the amount of enzyme leads to proportionate increase in the rate of a reaction.This is because if there is more substrate than enzymes can cope with.If you therefore increase the enzymes concentration some of the excess substrate will be acted upon and the rate of reaction will increase. |
|
|
Effect of substrate concentration on the rate of reaction |
If the concentration of the enzyme and the substrate is constant and the substrate is slowly increased,the rate of reaction will proportionately increase. As more substrate is however increased,all the active sites are filled up to a point where they can't keep working. Further addition of substrate will have no effect on the reaction When there is excess substrate the graph levels off |
|
|
Enzyme inhibitors
|
Are substances that directly on indirectly interfere with the enzymes active site therefore reducing its activity |
|
|
competitive inhibitors
|
they have a similar shape to the substrate. It is the difference between the concentration of the substrate and the concentration of the inhibitor that determine the effect of the inhibitor if the concentration of the substrate is increased they could occupy the active site when the inhibitor leaves and this reduces inhibitor activity |
|
|
Non competitive inhibitor
|
it attaches itself on a binding site which is not the active site. This changes the shape of the active site such that the substrate can no longer bind to it and the enzyme can't function
|
|
|
Metabolic pathways
|
Is a series of reactions in which each step is catalysed by an enzyme The end product inhibits enzyme A, if for some reason the concentration of the end product increases above normal, then there will be greater inhibitor of enzyme A. As a result less end product will be produced and its concentration will return to normal. This means there will be less product to inhibit enzyme A and the end product will increase again |
