2.1) Metabolic Pathways Flashcards
1
Q
- What is βmetabolsimβ?
A
- The combination of all enzyme catalysed reactions within a cell.
2
Q
- What are βcatabolicβ pathways?
A
- Breakdown of molecules into sub-units π₯
- Releases energy β‘
- Provides building blocks π§±
3
Q
- What are βanabolicβ pathways?
A
- Synthesis of molecules from sub-units β¨
- Requires energy β
- (e.g. synthesis of proteins from amino acids)
4
Q
- What is a summary of the control of metabolic pathways?
A
- Metabolic pathways are controlled by the presence (or absence) of particular enzymes in the pathway,
β and through the regulation of the rate of reaction of key enzymes within the pathway.
5
Q
- What are the 3 properties of a catalyst?
A
- Lowers the activation energy β‘π
- Speeds up the rate of a chemical reaction π§ͺ
- Remains unchanged at the end of the reaction π
6
Q
- What is βactivation energyβ and how can it be lowered?
A
- βActivation energyβ is the input of energy to start the reaction off.
- βActivation energyβ can be lowered with the use of enzymes (biological catalysts)
7
Q
- What is βenzyme actionβ?
A
- Enzymes are made of proteins folded into a specifc shape
β exposing the active site (region where substrate fits) - Enzymes are specific to one type of substrate.
β The molecules of a substrate are complementary to the active site, showing a high affinity (chemcial attraction) β -
Products have a low affinity for the active site
β so are released after the reaction.
8
Q
- Describe βinduced fitβ
A
- Induced fit
β is when the shape of the enzyme changes slightly to make the active site fit very closely round the substrate molecule,
β³ as the active site is dynamic and flexible.
9
Q
- Explain the effect of substrate concentration
A
- At low concentrations of substrate π«
β the reaction rate is low π
β³ due to there being too few substrate molecules present to make maximum use of all the active sites. - An increase in substrate concentration π«
β means higher reaction rates π
β³ since more active sites are being used. - A further increase in substrate π« concentration
β fails to increase the reaction rate β
β³ because all the active sites are occupied (enzyme concentration + limiting factor) - The graph levels off γ°οΈ
β because there are more substrate molecules than active sites.
10
Q
- Explain βreversibilityβ
A
- Most metabolic pathways are reversible. π
β Often an enzyme can catalyse a reaction in both directions.
β³ The actual direction depends on the relative concentration of the reactants and products β¨ - If the concentration of metabolite B **was to *increase to an unusally high level and A were to *decrease, ππ
β enzyme 2 could go into reverse and convert some of B back into A until a balanced state (equilibrium) was restored.
11
Q
- Explain βregulation of metabolic pathwaysβ
A
- Some metabolic pathways
β (e.g. glycolysis in respiration)
β³ are needed to operatre continuosuly. - The genes that code for their enzymes must always be switched on so that the enzymes are always present in the cell
12
Q
-
REVIEW QUESTIONS:
1. State the term which describes a metabolic patwhay in which simple molecules are built up into complex molecules.
- i) Describe how the genetic code for glycogen synthase might be altered in an individual with the disease.
ii.) Explain why this altered genetic code fails to produce glycogen synthase.
A
- Anabolic pathway
- i.) The genetic code will contain a different nucleotide/base
ii.) The protein contains different amino acids.
13
Q
- What is an βinhibtorβ and can you name the three types?
A
- An βinhibitorβ is a substance which decreases the rate of an enzyme-controlled reaction.
- COMPETITIVE
- NON-COMPETITIVE
- FEEDBACK INHIBITION (BY AN END PRODUCT
14
Q
- Describe and explain βcompetitive inhibitorsβ
A
- A competitive inhibitor
β is a molecule which has a similar shape as the enzymeβs substrate. - It joins with the active site
β and prevents the substrate from joining to the enzyme. - As the inhibitor and substrate are competing for space on the active site,
β the reaction rate is reduced.
15
Q
- Describe and explain βnon-competitive inhibitorsβ
A
- A non-competive inhibitor
β binds to a location on the enzyme away from the active site (allosteric site) - It alters the enzymeβs shape
β and therefore the active site. - The substrate is prevented from binding to the enzymeβs active site
β and the reaction rate is severely reduced. - Additionally, increasing the substrate concentration has no effect on the reaction with a non-competitive inhibitor.
