biol 1406 chapter 6

properties by which we define life

order, growth, reproduction, responsiveness, and internal regulation, all require a constant supply of energy

thermodynamics

the branch of chemistry concerned with energy changes

first law of thermodynamics

energy is conserved, cells convert energy from food or sunlight into usable forms (ATP), energy cannot be created or destroyed

second law of thermodynamics

entropy (disorder) increases, cells maintain order by constantly using energy

energy

the capacity to do work

kinetic

energy of motion

potential

stored energy

heat

most convenient way of measuring energy because all other forms of energy can be converted into it

(1) calorie

heat required to raise 1 gram of water 1 degree C

energy flow

energy flows into the biological world from the sun, captured by photosynthetic organisms, stored as potential energy in chemical bonds

redox reactions

OIL RIG, reduction is a higher level of energy than oxidized form, redox reactions are always paired

gibbs free energy

the energy available to do work at constant temperature in a system, G = energy available to do work, H = enthalpy (energy in a molecule’s chemical bonds), T = absolute temperature (K = C + 273), S = entropy (unavailable energy), G = H - TS, TS expresses the amount of disorder in a system

change in G < 0

spontaneous, exergonic

change in G > 0

non-spontaneous, endergonic

exergonic

reactions that are spontaneous

endergonic

reactions that require free energy

activation energy

the extra energy required to destabilize existing bonds and initiate a chemical reaction

rate of exergonic reaction

depends on the activation energy required, larger activation energy proceeds more slowly, can be increased by increasing energy of reacting molecules (heating) or lowering activation energy (catalyst)

catalysts

substances that influence chemical bonds in a way that lowers activation energy, are enzymes, cannot violate laws of thermodynamics (cannot make an endergonic reaction spontaneous, do not alter the proportion of reactant turned into product)

ATP (adenosine triphosphate)

the primary energy currency used by cells, composed of ribose (five carbon sugar), adenine, and a chain of three phosphates

how ATP stores energy

in the bonds between its phosphate groups

function of ATP hydrolysis

release energy for cellular processes

enzymes

found in all living cells, made of proteins, biological catalysts, speed up reactions, unchanged by reactions

active site

the region of an enzyme where the substrate binds and the reaction occurs

induced fit model

the enzyme changes shape slightly to fit and stabilize the substrate

how to lower enzyme activation energy

destabilize existing bonds and stabilize the transition site

saturated enzyme

all active sites are occupied; adding more substrate wont increase rate

temperature effects on enzyme activity

too low = slow reaction, too high = denaturation

denaturation

protein loses its three-dimensional structure and biological function due to external stress

average optimum pH

6-8

enzyme and substrate relationship

interact through a temporary, specific fit

inhibitors

substances that bind to an enzyme and decreases its activity

competitive inhibitors

competes with substrate for active site by blocking the active site

noncompetitive inhibitor

binds to enzyme at a site other than active site, changes shape of enzyme so it cannot bind to substrate, most bind to allosteric site

allosteric inhibitor

binds to allosteric site and reduces enzyme activity

allosteric activator

binds to allosteric site and increases enzyme activity

cofactors

act to assist enzymes and can be metal ions including zinc, molybdenum, manganese, often found in the active site of the enzyme, function to draw electrons away from covalent bonds

coenzymes

type of cofactor that are nonprotein organic molecules and act as electron acceptors/transferrers, these are vitamins

metabolism

total of all chemical reactions carried out by an organism

anabolic reactions/anabolism

expend energy to build up molecules (endergonic), builds biopolymers by dehydration reactions

catabolic reactions/catabolism

harvest energy by breaking down molecules (exergonic), breaks biopolymers by hydrolysis reactions

feedback inhibition

when the end product of a pathway inhibits an earlier enzyme to prevent waste