Biology 120 Exam 3

exam 3

potential energy in bonds

chemical energy

weaker bonds with equally shared electrons

high potential energy

stronger bonds with unequally shared electrons

low potential energy

shorter, covalent bonds

potential energy decreases, thermal energy or light

enthalpy

H, total energy in a molecule

how to calculate enthalpy

potential energy of the molecule + effect of the molecule on surrounding pressure and volume

net enthalpy

the total energy in biological systems

changes in enthalpy

based on the difference in potential energy

exothermic reactions

release heat energy, delta H less than 0, products less potential energy than reactants

endothermic reactions

take up heat energy, delta H greater than 0, products higher potential energy than reactants

entropy

S, the amount of disorder

products more disordered than reactants

entropy increases, delta S greater than 0

gibbs free energy

G, determines whether a reaction is spontaneous or requires added energy to proceed

change in G =

delta H - T*Change in S

change in G is less than 0

spontaneous reaction, exergonic

Change in G is greater than 0

Nonspontaneous reaction that requires energy output to occur, these reactions are endergonic

Change in G = 0

Reaction at Equilibrium

Collision Theory

Reaction at equilibrium

Energetic Coupling

Allows chemical energy released from one reaction to drive another reaction

during a redox reaction, electrons

can be transferred or simply shift

redox electrons transferred

from e donor to e acceptor

most e acceptors

gain potential energy as they are reduced

e usually accompanied by

a proton

ATP transfers energy via

phosphate groups

ATP forms bonds between

3 phosphate groups

negative charges

repel

high energy bonds store

potential energy

ATP hydrolysis releases

free energy

ATP hydrolysis forms

ADP and Pi

ATP hydrolysis is

highly exergonic

enzymes...

are protein catalysts, bring reactions together in precise orientations, make reactions more likely, are specific for a single type of reaction

before a reaction can take place, reactants must

collide in a precise orientation, have enough kinetic energy to overcome repulsion between electrons that come into contact as a bond forms

substrates bind to

the enzymes active site

enzymes undergo a shape change when

the substrates are bound to the active site

substrates bind via

hydrogen bonding

enzymes lower

activation energy

reaction rates depend on

the kinetic energy of the reactants, the activation energy of the particular reaction

interactions between the enzyme and the substrate

stabilize the transition state, lower the activation energy required for the reaction to proceed

3 steps of enzyme catalysis

initiation, transition state facilitation, termination

initiation

substrates bind to the active site in a specific orientation, forming an enzyme-substrate complex

transition state facilitation

interactions between enzyme and substrate lower the activation energy

termination

products have lower affinity for active site and are released. Enzyme is unchanged after the reaction

the speed of an enzyme-catalyzed reaction

increases linearly at low substrate concentrations, slows as substrate concentration increases, reaches maximum speed at high substrate conceptions

cofactors

inorganic ions, such as Zn^2+, Mg^2+, and Fe^2+, that reversibly interact with enzymes

coenzymes

organic molecules such as NADH or FADH2 that interact with enzymes

prosthetic groups

non-amino acid atoms or molecules that are permanently attached to proteins

factors that affect enzyme function

temperature and pH

temperature affects

folding and movement

pH affects

shape and reactivity

most enzymes are regulated by

regulatory molecules

competitive inhibition

occurs when a single molecule competes with the substrate for the active site

allosteric regulation

occurs when a molecule binds at a location other than the active site and causes a change in enzyme shape

covalent modification

changes the enzymes primary structure, can be irreversible or reversible

irreversible changes of enzymes

result from cleavage of peptide bonds

reversible changes of enzymes

addition of phosphate groups, causes a change in shape, may active or inactive the enzyme

kinase

turns protein on

phosphatase

turns protein off

metabolic pathways are regulated by

feedback inhibition

anabolic

small molecules are assembled into large ones, energy is required

catabolic

large molecules are broken down into small ones, energy is released

steps of cellular respiration

glycolysis, pyruvate processing, citric acid cycle, electron transport/oxidative phosphorylation

2 requirements of cells for cellular respiration

energy to generate ATP, a source of carbon to use as raw materials fro synthesizing macromolecules

catabolic pathways

breakdown molecules, harvest stored energy to produce ATP

anabolic pathways

synthesis of larger molecules, often use energy in the form of ATP

glycolysis starts by using

2 ATP (energy investment)

energy payoff phase

NADH is made and ATP produced by substrate level phosphorylation

net yield of glycolysis

2 NADH, 2 ATP, 2 pyruvate

glycolysis inhibitors

phosphofructokinase (feedback inhibition)

ATP required at steps ____ of glycolysis

1 and 3

input of glycolysis

2 ATP 1 glucose

output of glycolysis

2 NADH 2 ATP 2 Pyruvate

pyruvate processing takes place in

pyruvate dehydrogenase (mitochondrial matrix)

input of pyruvate processing

pyruvate, NAD, CoA

output of pyruvate processing

CO2, NADH, acetyl CoA

inputs of citric acid cycle

2 AoC for each glucose

outputs of citric acid cycle

6 NADH 2 FADH2 and 2 ATP

citric acid cycle regulated

feedback inhibition

electrons that aren't used are transferred into

oxygen to from water

maximum ATP yield per glucose

38

molecules that oxidize NADH and FADH2

electron transport chain

ETC components

proteins, ubiquinone, "Q"

photosynthesis

the use of sunlight to manufacture carbohydrates

photosynthesis 2 sets of reactions

light dependent and Calvin cycle reactions

light dependent reactions

produce o2 to h2o, water split to form o2, electrons excited by light energy, high energy electrons are transferred to the electron carrier NAD, forming NADH

Calvin cycle reactions

produce sugar from CO2, electrons and ATP are used to reduce CO2

interior of chloroplasts

thylakoids

stacks of thylakoids

grana

space inside thylakoid

lumen

surrounding thylakoid

stroma

process of thin layer chromotography

separates different pigments from plants

chlorophyll

absorb red and blue light, reflect and transmit green light

carotenoids

absorb blue and green light, reflect and transmit yellow, orange, and red light

carotenoids and xanthophylls

absorb light and pass energy onto chlorophyll, extended range of photosynthesis, protect chlorophylls from damage by stabilizing free radicals

photosystem 2

ATP

photosystem 1

NADPH

when light is absorbed, electrons enter

an excited state

in photosynthesis, released energy is used to

reduce molecules to manufacture sugar

electrons are passed down an ETC in the

thylakoid membrane

passing down of electrons in ETC...

produces proton gradient, drives ATP production via ATP synthase

in the ETC linear pathway

electrons from photosystem 2 produce a proton - motive force that drives ATP synthesis, electrons from photosystem 1 produce NADPH