1.6- metabolic pathways

Question 1

what is metabolism?

Answer 1

all the reactions that take place in a living cell

Question 2

what are metabolic pathways?

Answer 2

integrated and controlled pathways at enzyme-controlled reactions within a cell

Question 3

2 types of cell reactions

Answer 3

catabolic

anabolic

Question 4

what happens in catabolic pathways?

Answer 4

substrate is usually a large molecule

products are small molecules

energy is released

Question 5

what happens in anabolic pathways?

Answer 5

substrate is usually a small molecule

products are large molecules

energy is required

Question 6

what are metabolic pathways made up of and how do they work?

Answer 6

chains of enzyme catalysed reactions

the product of one reaction is the substrate for the next

Question 7

what happens in alternative routes of metabolic pathways?

Answer 7

allows steps in the pathway to be bypassed

Question 8

2 things that control metabolic pathways

Answer 8

presence or absence of particular enzymes

regulation of the rate of reaction of key enzymes

Question 9

what do enzymes do in a metabolic pathway and how?

Answer 9

speed up rate of reaction

by lowering the activation energy needed by the reactants to form the transition state

Question 10

what is the lock and key hypothesis?

Answer 10

that enzymes are large, complex proteins folded into specific shapes so they can fit a particular substrate

Question 11

what is induced fit?

Answer 11

enzymes only act on one specific substrate complementary to and fits into the active site

when a substrate enters the active site, the active site can change shape slightly to better fit the substrate after the substrate binds

Question 12

2 things induced fit ensures

Answer 12

enzymes active site comes into very close contact with the molecules of the substrate

increases the chances of a reaction taking place

Question 13

affinity between substrate and active site

Answer 13

substrate molecules have a high affinity for the active site

Question 14

affinity between product and active site

Answer 14

subsequent products have a low affinity allowing them to leave the active site

Question 15

how is the orientation of reactants determined?

Answer 15

by the shape of the active site when the reaction involves 2 or more substrates

Question 16

what is activation energy?

Answer 16

the energy needed to break chemical bonds in the reactant chemicals

Question 17

when do the chemical bonds break in the reactant chemicals?

Answer 17

when the molecules of the reactant have absorbed enough energy to make them unstable

Question 18

what happens once the chemical bonds break?

Answer 18

they are now in the transition state and the reaction can occur

Question 19

how does an enzymes presence effect activation energy and what’s the outcome?

Answer 19

lowers activation energy

makes it easier to start a reaction

Question 20

what happens as the substrate concentration increases in a reaction?

Answer 20

more and more of the enzymes active sites become used until there are none available

Question 21

what happens at a low concentration of substrate in a reaction?

Answer 21

reaction rate is low since there are too few substrate molecules present

Question 22

how do you increase the reaction rate?

Answer 22

by increasing the substrate concentration

Question 23

what happens when increasing substrate concentration no longer increases the reaction rate?

Answer 23

enzyme concentration now becomes the limiting factor and the graph levels off

Question 24

how do you reverse a metabolic pathway?

Answer 24

abundance of one metabolite and the scarcity of the one prior

enzyme between metabolites can go into reverse and convert some back until balanced state is restored

Question 25

3 types of inhibition

Answer 25

competitive

non-competitive

feedback

Question 26

what are competitive inhibitors?

Answer 26

have the same shape or partial shape as the natural substrate for the enzyme

Question 27

where do competitive inhibitors bind and what is this effect?

Answer 27

at the active site

prevents the substrate from binding

Question 28

what can reverse competitive inhibition and how?

Answer 28

by increasing the substrate concentration

increases the likelihood of the substrate molecule combining with the active site and not the inhibitor

Question 29

where do non-competitive inhibitors bind and what is this effect?

Answer 29

bind away from the active site

change the shape of the active site preventing the substrate from binding

Question 30

what can reverse non-competitive inhibition?

Answer 30

non-competitive inhibition is a permanent change

cannot be reversed by increasing the substrate concentration

Question 31

when does feedback inhibition take place?

Answer 31

when the end product in the metabolic pathway reaches a critical concentration

Question 32

how does feedback inhibition work and what is the effect?

Answer 32

end product then inhibits an earlier enzyme blocking the pathway

prevents further synthesis of the end product