Biological molecules Flashcards
Structure vs function of starch
- insoluble - doesn’t draw water into cells by osmosis - doesn’t affect water potential
- Large + insoluble - can’t diffuse out of the cell
- compact - large amount stored in a small space
- easily hydrolysed - glucose readily transported and available for use in respiration
- Branching gives many ends - more sites for enzyme action
Structure vs function of cellulose
- long, straight chains of beta glucose
- chains run alongside one another with hydrogen bonds forming cross linkages between them
- Molecules grouped to form microfibrils which form fibres to provide more strength
Structure vs function of glycogen
- insoluble - doesn’t draw water into cells by osmosis - doesn’t affect water potential
- Large + insoluble - can’t diffuse out of the cell
- compact - large amount stored in a small space
- more branches than starch - more ends - speeds enzyme action - more rapidly broken down to glucose monomers - used in respiration
Testing for reducing sugar
- heat with benedict’s
- positive result = brick red precipitate
Testing for non-reducing sugar
- heat with benedict’s - no change
- add dilute hydrochloric acid
- add sodium hydrocarbonate until neutral
- heat with benedict’s
positive result = brick red precipitate
Triglyceride structure to function
- high ratio of energy storing C-H bonds to form atoms - excellent energy store
- Low mass:energy - good energy store - large amount stored in a small space
- Large, non-polar, insoluble - storage doesn’t affect osmosis in cells
- high hydrogen:oxygen atoms - release water when oxidised
Primary structure
The sequence of amino acids in the polypeptide (peptide bonds)
Secondary structure
the primary structure coils to form a
alpha helix, held by hydrogen bonds
Tertiary structure
secondary structure folds to form final 3D shape, held together by hydrogen/ionic/disulfide bonds
quaternary structure
more than one polypeptide chain
Activation energy
The minimum amount of energy needed to activate the reaction
The induced fit model
- Active site changes shape to allow the substrate to bind to the active site
- Active site changes shape so the substrate fits exactly to form enzyme-substrate complexes
Effect of substrate concentration on enzyme activity
- increase substrate concentration increases chance of successful collisions, increase chance of forming an ES complex, increase rate of reaction
- this continues until all the enzyme’s active sites are saturated = maximum rate of reaction
Effect of enzyme concentration on enzyme activity
- increase enzyme concentration, increases chances of successful collisions, increase chance of forming an ES complex, increase rate of reaction
- this continues until all the substrates are used up = maximum rate of reaction
Effect of temperature on enzyme activity
- as temperature increases
- the kinetic energy increases
- the molecules move faster
- increases chance of successful collisions
- increase chance of forming ES complex
- increases rate of reaction
- carries on until optimum
- after optimum
- bonds in tertiary structure break (hydrogen and ionic bonds)
- lose active site shape
- substrate no longer complementry
- can’t form ES complexes
- enzymes denatured
Effect of PH on enzyme activity
if change PH away from optimum, bonds in tertiary structure break, lose active site shape, no longer form ES complex, enzyme denatured
Competitive inhibitors
a substance with a similar shape to the substrate and a complementry shape to the enzyme’s active site, binds to the active site, blocking it, preventing ES complexes from forming. Can be overcome by adding more substrate
Non-competitive inhibitors
a substance that binds to the allosteric site on the enzyme which causes the active site to change shape, so less ES complexes can form. Cannot be overcome by adding more substrate
