Module 6 Part 2: Metabolism Gen Bio

what two things make cellular activity possible?

energy and enzymes

what directs which reactions occur and when?

enzymes

what helps cells acquire and use energy?

enzymes

what is bioenergetics?

the study of how organisms manage their energy resources; the flow of energy through an organism

what is required to obtain energy?

chemical reactions

what is activation energy?

the minimum amount of kinetic energy required to initiate a chemical reaction

what is the transition state?

- the intermediate point between breaking old bonds and forming new ones

- free energy of transition state is high

at what point in a chemical reaction is free energy highest?

during the transition state

in order for a reaction to take place, reactants need to:

collide in precise orientation

have enough kinetic energy to overcome activation energy barrier and achieve transition state

T or F: enzymes are catalysts

true

what do enzymes do?

- bring reactants together in precise orientations

- make reactions more likely to occur

- are specific for a single type of substrate/reaction

T or F: enzymes will bind to any substrate. they are not specific

false

when reactants undergo chemicafl reactions by binding to an enzyme, they are called ___________

substrates

Can enzymes change the ΔG of a reaction?

no

can enzymes make an endergonic reaction exergonic?

no

T or F: enzymes will only hasten a reaction that would happen eventually

true

T or F: enzymes are very selective in order for processes in cells to be highly regulated

true

where do substrates bind?

at an enzymes active site

what is the purpose of active site binding?

it helps substrates collide in precise orientation and breaks and forms bonds in order to generate products

what is the name of the conformational change that occurs when substrates are bound to the active site?

induced fit

Do enzymes increase or decrease activation energy?

they decrease/lower activation energy

what is induced fit?

the mild shift in shape that occurs at the active site that optimizes reactions

what type of bonds hold substrates in place at the active site?

hydrogen bonding and weak interactions with amino acid residues

what are the three steps of enzyme catalysis?

initiation

transition state facilitation

termination

what is initiation?

the first step of enzyme catalysis. substrates are precisely oriented as they bind to the active site

what is transition state facilitation?

the second step of enzyme catalysis. interactions between substrate and active site R groups cause enzyme conformation change called induced fit and lower activation energy

what is termination?

third step of enzyme catalysis. reaction products are released from enzyme.

how does the speed of enzyme-catalyzed reactions differ with different substrate concentrations?

increases linearly at low substrate concentrations

at intermediate substrate concentrations, the increase in speed slows

at high concentrations, the reaction rate plateaus

does the speed of an enzyme catalyzed reaction occur faster at higher or lower substrate concentrations?

lower concentrations

what is saturation kinetics?

as substrate concentration increases, the reaction rate will increase until the active sites cannot accept substrates any faster and the reaction rate levels off.

what are the three molecules that are not apart of the enzyme that are required for their functionality?

1. cofactors

2. coenzymes

3. prosthetic groups

what is a cofactor?

inorganic ions, such as Zn2+, Mg2+ and Fe2+ that reversibly interact with enzymes

what are coenzymes?

organic molecules such as NADH or FADH2 that interact with enzymes

what are prosthetic groups?

non amino acid atoms or molecules permanently attached to proteins

T or F: enzyme structure is critical to its function

True

are enzymes sensitive to the alteration of protein shape?

yes

activity of enzymes changes due to what?

temperature, pH, interactions with other molecules, modifications of primary structure

How does temperature affect enzyme activity?

- affects folding and movement of the enzyme and substrates (weak bonds can break)

- affects kinetic energy

How does pH affect enzyme activity?

- affects enzymes shape and reactivity

- affects charge on acidic and basic groups

what two things impact enzyme shape and reactivity?

temperature and pH

T or F: enzymes have an optimal temperature and pH

true

what are regulatory molecules?

regulate a cell's enzymatic activity

may change enzymes structure

may change ability to bind to its substrate

may either activate or inactivate the enzymes function

what are the two ways that reversible regulatory interactions work via noncovalent interactions?

competitive inhibition and allosteric regulation

what is competitive inhibition?

molecule competes with the substrate for active site

what is allosteric regulation?

a molecule binds at a location other than the active site and causes a change in the enzymes shape that can activate or deactivate the enzyme.

aka non competitive inhibition

what are covalent modifications?

- regulation of enzymes through changes to the enzymes primary structure that can be reversible or irreversible

in covalent modifications, what causes irreversible changes to happen?

cleavage of peptide bonds

in covalent modifications, what is the most common reversible modification of enzymes?

phosphorylation

what is phosphorylation?

the addition of a phosphate group that modifies protein structure and can cause a change in shape of the enzyme that either activates or deactivates it.

what are catabolic pathways?

break down molecules for sources of energy and carbon building blocks

what are anabolic pathways?

use energy and carbon building blocks to synthesize molecules

how do enzymes work together in metabolic pathways?

they form a series or chain of reactions where each is catalyzed by a different enzyme to build biological molecules

how are metabolic pathways regulated?

through feedback inhibition

what is feedback inhibition?

a cellular control mechanism where the end product of a metabolic pathway acts as an inhibitor to an enzyme involved in its own synthesis