BIOL Ch 6

energy

the capacity to do work

work

a force acting on an object that causes the object to move

chemical energy

the energy that is contained in molecules and released by chemical reactions. Contained within sugar, glycogen, and fat.

ATP

cells use … to accept and transfer energy from one chemical reaction to the next. The principal energy carrier in cells

high-energy phosphate bonds

energy is stored in the … of ATP

endergonic reaction

the formation of ATP is a …

broken down into ADP + P and its stored energy is released

at sites in the cell where energy is needed, ATP is …

very briefly before being broken down

unlike glycogen and fat, ATP stores energy …

potential and kinetic

two types of fundamental energy

potential energy

stored energy

kinetic energy

energy of movement

laws of thermodynamics

describe the quantity and quality of energy

first law of thermodynamics

energy can neither be created nor destroyed, but can change form. Also referred to as law of conservation of energy. Total amount of energy within a closed system remains constant unless energy is added or removed

second law of thermodynamics

the amount of useful energy decreases when energy is converted from one form to another. Systems move towards maximum entropy

entropy

a measure of disorder/unpredictability

chemical reaction

a process that forms or breaks chemical bonds holding atoms together. They convert reactants into products

exergonic

reactions that release energy

the burning of glucose. Overall: sugar combines with oxygen to produce CO2 and water, thus releasing energy. Why: molecules of sugar contain more energy than the molecules of CO2 and water.

example of exergonic reaction

activation energy

initial energy input required to start up a chemical reaction. Negatively charged electron shells of atoms repel one another and inhibit bond formation. Molecules must be moving fast to overcome electronic repulsion and react. Increase temperature → increase kinetic energy → increase rate of reaction

endergonic

reactions that require a net input of energy. Contain less energy than products. Energy in glucose cannot be used directly to fuel these.

process of photosynthesis. Overall: plants add the energy of sunlight to the lower-energy reactants water and CO2 to produce the higher energy-product sugar

example of endergonic reaction

breakdown of glucose

most organisms are powered by …

energy-carrier molecule

high-energy, unstable molecules. Where glucose breakdown energy is first transferred to. Present at the site of an exergonic reaction, capture some of the released energy from a reaction. Transfers energy to an endergonic reaction elsewhere in a cell.

glucose metabolism

energy can be transferred to electrons in …

NAD and FAD

electron carrier molecules such as …transport high-energy electrons

high-energy electrons to other molecules

electron carriers donate … leading to ATP synthesis

coupled reaction

when an exergonic reaction provides the energy needed to drive an endergonic reaction. They may occur in different parts of the cell, so the energy-carrier molecules carry the energy from one to the other

lower activation energy (making reactions more likely to go forward). Control the rate of energy release and capture some energy in ATP

how do enzymes promote biochemical reactions?

regular body temperature

spontaneous reactions proceed too slowly to sustain life at …

reaction speed

determined by the activation energy required to start process

low activation energies

proceed rapidly at body temperature

high activation energies

move very slowly at body temperature

enzymes

biological catalysts composed of protein that regulate all reactions in living cells and catalyze chemical reactions by lowering the activation energy.

orient, distort, and reconfigure

in the process of lowering activation energy, enzymes … molecules

coenzyme

small nonprotein helper molecules that are sometimes required to help enzymes

water-soluble vitamins (some B vitamins)

many … are essential to humans because they are used by the body to synthesize coenzymes

catalysts

speed up the rate of a chemical reaction without themselves being used up

1. speed up reactions by lowering activation energy
2. speed up only exergonic reactions
3. are not consumed or changed by the reactions

three properties of all catalysts

the conversion of CO to CO2

catalytic converters in cars facilitate …

active site

a pocket in each enzyme where one or more reactant molecules can enter. “Lock and key”.

complementary and specific

the distinctive shape of the active site is both … and … to the substrate

substrates

reactant molecules

1. shape and charge of active site allows only specific substrates to enter
2. upon binding, the substrates and active site change shape and promote a reaction
3. when reaction Is finished, the product(s) no longer properly sit into active site

three steps of enzyme catalysis

metabolism

the sum of all the chemical reactions within a cell

metabolic pathways

where many cellular reactions are linked. An initial reactant molecule is modified by an enzyme many times until a final product is produced

the active sites of all the enzyme molecules are being continuously occupied

as substrate levels increase, the reaction rate will increase until …

1. control of enzyme synthesis (quantity)
2. control of enzyme activity (quality)

ways metabolic pathways are controlled

metabolic need

genes that code for specific proteins are turned on and off according to …

increase, increased, decreased

… in substrate can trigger … enzyme production → … substrate levels

Pepsin is inactive when synthesized but becomes activated in the stomach under acidic conditions

example of enzyme synthesized in inactive form

competitive inhibition

a substance that is not the enzyme’s normal substrate binds to the active site of the enzyme, competing with the substrate for the active site

noncompetitive inhibition

a molecule binds to a site on the enzyme different from the active site

allosteric regulation

the way in which small regulator molecules can bind to enzymes and enhance or inhibit activity

feedback inhibition

negative feedback type of allosteric inhibition that causes a metabolic pathway to stop producing its product when quantities reach and optimum level

inhibited allosterically by the end product of the pathway

an enzyme near the beginning of a metabolic pathway is …

drugs and poisons

… inhibit enzymes by competing with the natural substrate for the active site

nerve gases and insecticides

some … permanently block the active site of acetylcholinesterase

arsenic, mercury, and led

… bind permanently to the non-active sites of various enzymes, activating them

pH is too high or low

enzyme structure is denatured and function is destroyed when …

salts

… can destroy enzyme function by altering structure of enzyme

slows it down

effect low temperatures on molecular movement

causes enzyme shape to be altered, destroying function

effect of high temperatures on molecular movement

very narrow range

most enzyme function optimally within a …

pH 2

maximum activity of pepsin occurs at about ..

pH 8

maximum activity of trypsin occurs at about …

pH 7.4

maximum activity of most cellular enzymes occurs at about …

98\.6° F (37° C)

maximum activity for most human enzymes occurs at about …