Chapter 3: Section D: Enzymes and Chemical Energy Flashcards Preview

ONLINE PHYSIOLOGY > Chapter 3: Section D: Enzymes and Chemical Energy > Flashcards

Flashcards in Chapter 3: Section D: Enzymes and Chemical Energy Deck (23):
1

Metabolism

all the chemical reactions that occur within out cells

2

Anabolism

synthesis of organic molecules (together)

3

Catabolism

breakdown of organic molecules (apart)

4

Chemical reactions

- reactants react with each other chemically to form a product
- glucose + fructose (reactants) sucrose (product)
- chemical reactions either use energy (transfer it to molecules ) or release energy as heat (energy measured in kilocalories)
- chemical reactions are reversible

5

Exergonic reactions

- the reactants contain more energy than the products
- releases energy
- once begun, occur spontaneously
- ATP --> ADP+Pi+energy

6

Endergonic reactions

- the products contain more energy than the reactants
- use energy
- will only occur if energy is added
- ADP+Pi+energy --> ATP

7

Irreversible reactions

- use large amount of energy because almost all reactant molecules have become product

8

Four factors that affect reaction rates

- reactant concentrations (higher concentrations: faster reaction rates)
- activation energy (higher activation energy: slower reaction rate)
- temperature (higher temperature: faster reaction rate)
- catalyst (presence of catalyst: faster reaction rate)

9

Law of mass action

- an increase in the concentration of the reactants (or decrease in product concentration) will increase the rate of the forward reaction, increasing product formation and v.v.

10

Activation Energy

- once an exergonic reaction begins, it proceeds spontaneously but because existing chemical bonds need to be destabilized to get the reactions started, a small amount of energy must be added to start the reaction = activation energy
- activation energy is like a ball rolling down a hill, takes a push to get started (Energy) but then rolls freely

11

Enzyme

- biological catalyst
- molecule that lowers the activation energy of a chemical reaction and speeds up the rate at which chemical reactions occur
- the enzyme is not used up in the reaction

12

substrates

- reactants in an enzymatic reaction (E+S--> ES--> E+P)
- enzyme-substrate complex forms when the substrate binds to the active site on the enzyme
- shape of active site is specific for a given substrate
- induced fit vs. lock&key model

13

Induced Fit substrate

- somewhat fits into ligand, however once it is close, then it is molded into the binding site

14

Lock&Key Model

- fits binding site for a very specific shape

15

Cofactors

- non-protein molecules that are required by an enzyme for it to function
- metal ions & coenzymes

16

Metal enzymes

copper, zinc, iron

17

coenzymes

nonprotein organic molecules (derived from vitamins)

18

regulation of enzyme-mediated reactoins

- affect rate or effectiveness
1) substrate concentration
2) enzyme concentration
3) pH of environment
4) temperature
5) regulation of enzyme activity

19

Allosteric modulation

- activation or inhibition or change in affinity
- modulator molecule binds to regulatory site on enzyme that changes shape of active site
- increase affinity --> increase reaction rate, however max rate doesn't change
- any enzyme can have variety of allosteric and/or covalent modulation sites

20

noncompetitve inhibition

- inhibitor binds to an allosteric (regulatory) site or causes covalent modulation on the enzyme --> shape change, preventing substrate binding

21

competitve inhibition

- inhibitor has a shape similar to the substrate; binds to active site and enzyme activity ends

22

feedback inhibition/end-product inhibition

- the product of an enzyme-catalyzed metabolic reaction or pathway inhibits enzyme activity
- regulates amount of product produced by inhibiting itself when has enough product (self-regulating process)

23

metabolic pathways

- series of linked reactions that result in a desired product
- each step is controlled by a specific enzyme
- A--E1--> B--E2--> C--E3--> D
*takes to get from A to D many enzymes (E1, E2, E3)