Chapter Six: An Intro to Metabolism

Question 1

what is metabolism?

Answer 1

metabolism is the sum of the chemical reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material

Question 2

what is activation energy?

Answer 2

activation energy is the minimum quantity of energy which the reacting species must posses in order to undergo a specified reaction

Question 3

what is Gibbs free energy? what is its symbol?

Answer 3

Gibbs free energy is usable energy; energy that is available to do work. G

Question 4

how does an activation barrier work?

Answer 4

the higher the barrier, the fewer molecules that will have the energy to make it over at any given moment.

Question 5

explain activation barrier chart.

Answer 5

see notes

Question 6

what is a catalyst?

Answer 6

a catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction

Question 7

what is an enzyme?

Answer 7

an enzyme is a catalytic protein. (selective acceleration of chemical reactions)

Question 8

what is an example of a enzymatic process? explain.

Answer 8

an example is sucrase breaking down sucrose with the addition of water (called hydrolysis). the sucrase enzyme catalyzes the chemical reaction taking place to break down the sucrose. the end product is glucose and fructose.

Question 9

how do enzymes speed up chemical reactions?

Answer 9

enzymes catalyze reactions by lowering the activation energy barrier.

Question 10

do enzymes affect the change in free energy?

Answer 10

no, they do not.

Question 11

how does an enzyme affect a course of reaction? how does a course of reaction differ without an enzyme?

Answer 11

the course of reaction without an enzyme has a higher activation energy barrier, compared to a course of reaction with an enzyme. the change in free energy is unaffected by the enzyme however.

Question 12

what is a substrate?

Answer 12

the reactant that an enzyme acts on.

Question 13

what is the enzyme-substrate complex?

Answer 13

when the enzyme is bound to its substrate.

Question 14

what is the active site?

Answer 14

the region on the enzyme where the substrate binds.

Question 15

what is substrate specificity?

Answer 15

when an enzyme only acts on a particular substrate (each chemical reaction has its own enzyme)

Question 16

why does enzyme specificity happen?

Answer 16

enzyme specificity occurs because there is a complementary fit between the shape of its active site and the substrate shape.

Question 17

how do enzymes reduce activation energy?

Answer 17

enzymes can change shape due to chemical interactions with the substrate. this induced fit of the enzyme to the substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction.

Question 18

how does an active site lower an activation energy barrier?

Answer 18

1. orienting substrates correctly
2. straining substrate bonds
3. providing a favorable microenvironment
4. covalently bonding to the substrate

Question 19

explain figure 6.15 (enzyme)

Answer 19

refer to notes

Question 20

what factors affect enzyme activity?

Answer 20

conditions within the cell: overall environmental factors (eg. pH and temp), chemicals that specifically influence the enzyme, and the relative concentrations of enzyme and substrate

Question 21

when does an enzyme perform the best?

Answer 21

an enzyme performs the best at it’s optimal temp and pH which allow for the most active shape of the enzyme molecule to occur

Question 22

why does an enzyme have an optimal temperature?

Answer 22

There is an optimal temperature for the rate of reaction because the temperature alters the shape of the active site in the enzyme in a way that is most effective for the shape of the substrate. This therefore maximizes the number of collisions between the enzyme and substrate molecules. When the temperature of the reaction is not between the optimal conditions, the enzyme may denature, or lose its ability to bind to the substrate.

Question 23

why does an enzyme have an optimal pH?

Answer 23

at the optimal pH, the bonds within the enzyme are influenced by the H+ and OH- ions in a way that the active site in the enzyme is more effective for the shape of the substrate. If the pH value of the enzyme is too high, the enzyme may denature, and be inactive, compared to if the pH value of the enzyme was too low, the rate of reaction would be at a slow pace.

Question 24

what are cofactors?

Answer 24

cofactors are nonprotein enzyme helpers that activate inactive enzymes.

Question 25

what are the types of cofactors?

Answer 25

1. inorganic - metal in ionic form

2. organic - called coenzymes. include vitamins

Question 26

what are enzyme inhibitors?

Answer 26

inhibitors reduce the level of activity of the enzyme (eg. toxins, poisons, pesticides, and antibiotics)

Question 27

what are competitive inhibitors?

Answer 27

competitive inhibitors bind to the active site of an enzyme, competing with the substrate

Question 28

what are noncompetitive inhibitors?

Answer 28

noncompetitive inhibitors bind to another part of an enzyme causing the enzyme to change shape and making the active site less effective (can be reversed)

Question 29

why does a cell regulate and monitor the activity level of enzymes?

Answer 29

a cell needs to regulate/ monitor the activity of an enzyme because they don’t need to be active constantly, because it is a waste of energy. a cell

Question 30

how does a cell regulate and monitor the activity level of enzymes?

Answer 30

a cell does this by switching on or off the genes that encode specific enzymes. or by increasing or decreasing the activity of enzymes.

Question 31

what is allosteric regulations?

Answer 31

allosteric regulations occur when a regulatory molecule binds to a protein at one site and affects the protein’s function at another site. this may either inhibit or stimulate an enzymes activity.

Question 32

what are allosterically regulated enzymes made from?

Answer 32

polypeptide subunits.

Question 33

what two forms do enzymes come in?

Answer 33

each enzyme has active and inactive forms

Question 34

what happens when an activator binds to an enzyme?

Answer 34

the binding of an activator stabilizes the active form of the enzyme.

Question 35

what happens when an inhibitor binds to an enzyme?

Answer 35

the binding of an inhibitor stabilizes the inactive form of the enzyme.

Question 36

what is feedback inhibition?

Answer 36

the end product of a metabolic pathway shuts down the pathway.

Question 37

what if an enzyme has sub-optimal conditions?

Answer 37

an enzyme can lose its ability to bind to a substrate.

Question 38

how does enzyme concentration affect rate of reaction?

Answer 38

increasing enzyme concentration will speed up the reaction, as long as there is substrate available to bind to. Once all of the substrate is bound, the reaction will no longer speed up, since there will be nothing for additional enzymes to bind to.

Question 39

how does substrate concentration affect rate of reaction?

Answer 39

increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bound, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate.

Question 40

is an enzyme reusable?

Answer 40

yes

Question 41

what are the two models of enzyme-substrate interaction?

Answer 41

lock-and-key, and induced fit.

Question 42

what is induced fit?

Answer 42

the binding of a substrate or some other molecule to an enzyme causes a change in the shape of the enzyme so as to enhance or inhibit its activity.