AP Biology Enzymes

Metabolism

all chemical reactions in an organism

metabolic pathways

series of chemical reactions that either build complex molecules or break down complex molecules

steps of substances being broken down

substrate->intermediate->product

catabolic metabolic pathway

pathways that RELEASE energy by BREAKING DOWN complex molecules into simpler compounds

anabolic pathways

CONSUME energy to BUILD complicated molecules from simpler compounds

energy

-the ability to do work

-organisms need energy to survive and function

loss of energy flow result

death

kinetic energy

-energy associated with motion

thermal energy

energy associated with movement of atoms or molecules (kinetic)

Potential energy

stored energy

chemical energy

potential energy available for release in a chemical reaction (potential)

thermodynamics

-study of energy transformations in matter

-apply to universe as a whole

1st law of thermodynamics

-energy cannot be created or destroyed

-can be transferred or transformed

1st law example: think...

-chemical (potential energy) stored in nut transformed into kinetic energy for squirrel to climb tree

2nd law of thermodynamics

-energy transformation increases entrophy (disorder) of the universe

-during energy transfers/transformations some energy is unstable and lost as heat

-basically using energy= release heat

2nd law example

as squirrel climbs tree, energy is released as heat

free energy

-scientists use to determine the likelihood of reactions in organisms, or if the reaction is energetically favorable

-free energy of reactions determine if reaction occurs spontaneously

exergonic or endergonic determination

-based on how the free energy changes

exergonic reactions

-reactions that release energy

-ex. cellular respiration

-spontaneous

endergonic reactions

-reactions that absorb energy

-ex. photosynthesis

-not spontaneous

living cells have what?

- constant flow of materials in and out of membrane

-cells not a equilibrium

cell work types:

mechanical, transport, chemical

Mechanical cell work

- movement

-ex. cilia, movement of chromosomes, contraction of muscle cells

-not really plants however- mostly animal cells

transport cell work

-pumping substances across membranes against spontaneous movement (concentration gradient)

chemical cell work

- synthesis of molecules

-ex. building polymers from monomers

ATP

- adenosine triphosphate: molecule used as source of energy to perform work

-ATP couples exergonic reactions to endergonic reactions to power cellar work

Organisms energy through ATP

- obtain energy by breaking bond between 2nd and 3rd phosphate via hydrolysis

- ATP->ADP

Phosphorylation

released phosphate moves to another molecule to give energy

ATP Cycle

rate of metabolic reactions

-laws of thermodynamics tell spontaneous or not, but not rate

-some spontaneous reactions move too slowly to use

-enzymes catalyze

enzymes

-macromolecules that catalyze (speed up) reactions by lowering initial energy

- are not consumed by reaction

-type of protein (can denature)

-enzyme names end in -ase

enzyme reactant

- act on reactant called substrate

active site

- area for substrate to bind

enzyme substrate complex

- substrates held in active site by weak interactions

-substrates converted to products

-products released

induced fit

enzymes will change the shape of their active site to allow the substrate to bond better

enzyme catabolism

enzyme anabolism

effects on enzymes

- are proteins-> 3D shape can be affected (denatured) by:

-temperature

-ph (likes basic)

-chemicals

shape change=

FUNCTION CHANGE

Optimal Conditions

-conditions that allow enzymes to function optimally

- increases with temp (at a certain point, will denature)

-function best at specific ph (to far outside can break H bonds, changing shape)

Enzyme cofactors

- non-protein molecules that assist enzyme function

-inorganic cofactors= metals

-can be bound loosely or tightly

holoenzyme

-enzyme with cofactor attached

coenzymes

- organic cofactors

-ex. vitamins

enzyme inhibitors

- reduce activity of specific enzymes

-inhibition can be permanent or reversible

permanent and reversible inhibitors

- permanent: inhibitor binds with covalent bonds

-ex. toxins and poisons

-reversible: inhibitor binds with weak interactions

competitive inhibitors

-reduce enzyme activity by blocking substrates to active sites

- can be reversed with increased substrate concentrations

noncompetitive inhibitors

- bind to an area other than the active site (allosteric site) which changes the sahpe of the active site

-type of allosteric inhibition

regulation by cell

- must be able to regulate metabolic pathways

-control when and where enzymes active

-switch genes that code fro enzymes on or off

allosteric regulation

- allosteric enzymes have 2 binding sites

- 1 active site

-1 allosteric site (regulatory site other than active)

allosteric regulation how

- molecules bond to allosteric site- changes shape and function of active site

- may result in inhibition (by inhibitor) or stimulation (by activator) of the enzymes activity

allosteric activator

-substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain open

Allosteric inhibitor

substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites are closed (inactive form)

cooperativity

substrate binds to one active site (on an enzyme with more than one active site) which stabilizes the active form

-considered allosteric regulation since binding at one site changes the. shape of other sites