Regulation of biochemical pathways in photosynthesis and cellular respiration

Question 1

Biochemical pathway

Answer 1

• Is a series of linked biochemical reactions that start with an initial reactant that is converted into a final product
• The product of one reaction is the starting reactant for the next step

Question 2

Catabolic pathway

Answer 2

• Exergonic
• Breaks down complex molecules into more simple molecules
• They are energy releasing pathways
  Eg. cellular respiration

Question 3

Anabolic pathway

Answer 3

• Endergonic
• Assemble simple molecules into more complex molecules
• Require a net input of energy (energy requiring pathways)
  Eg. photosynthesis

Question 4

Enzymes

Answer 4

• Are soluble globular proteins which act as biological catalysts to speed up the rate of the reactions in biochemical pathways
• They enable reactions to occur at lower temperatures, reducing the amount of activation energy needed.
  Active site
• Unique 3D shape complementary to a specific substrate. When substrate binds at enzyme active site, the substrate can be split into smaller molecules, rearranged or assembled into more complex molecules

Question 5

Cofactor

Answer 5

Any molecular that interacts with an enzyme to help maximise its function.
Organic cofactors - essential for the function of particular enzymes (also known as coenzymes)
Inorganic cofactors - have metal ions such as magnesium, copper, manganese, calcium or clusters of several ions. No source of carbon or oxygen

Question 6

Temperature

Answer 6

As temp drops below optimum, reaction rate drops due to low thermal energy (fews collisions between substrate and enzyme) enzyme becomes inactive
As temp increases above optimum, reaction rate reduces and heat denaturation occurs

Question 7

pH

Answer 7

–> measure of hydrogen ions (acidic low hydrogen, alkaline high hydrogen)
When the pH is outside its optimal (too acidic or too basic) the bonds at the active site will break and no longer have a level of complementary to its substrate.

Question 8

Substrate concentration

Answer 8

Rate of reaction increases with increasing substrate concentration but only up to a point where active sites of the enzyme molecules are occupied.

Question 9

Enzyme concentration

Answer 9

(provided substrate concentrations are high and temp and pH are kept constant) increases in enzyme concentration are expected to produce a continual increase in reaction rate. This may level off if substrate concentration becomes a limiting factor.

Question 10

Competitive enzyme inhibitors

Answer 10

Competitive inhibitors bind to the active site of an enzyme, preventing substrates from binding

Question 11

Non-competitive enzyme inhibitors

Answer 11

Non-competitive inhibitors bind to an allosteric site on the enzyme

Question 12

Irreversible inhibition

Answer 12

Occurs when a specific molecule forms a covalent bond with an enzyme at its active site, and the normal substrate is permanently blocked from the active site.

Question 13

Reversible

Answer 13

Occurs when a specific molecule forms a hydrogen bond with an enzyme at its active site, and the normal substrate is blocked from the active site (not permanent)
Forms a weak hydrogen bond- bond is able to break

Question 14

Allosteric site

Answer 14

Location on an enzyme molecule where a compound can bind and alter the shape of the enzyme, thus the active site (is not permanent)