life 120 - ch.6-8

chemical reactionsn

• drive the processes of life

• are always occurring

• harvests energy and uses it for work

metabolism

totality of chemical reactions in an organism

metabolic pathways

multistep reaction that starts with certain reactant and ends with certain product

• each step is catalyzed by an enzyme

two types of metabolic pathways

• anabolic: requires energy, builds complex reactions

• catabolic: releases energy, turns complex reactions into simpler ones

energy

the capacity to cause change

kinetic energy

energy based on motion

thermal energy

type of kinetic energy that is focused on the random movement of atoms/moleculesth

heat

thermal energy is transferred from one object to another

potential energy

energy that matter posses based on its location/structure

chemical energy

potential energy available for release in chemical reactionn

thermodynamics

the study of energy tranformations

laws of thermodynamics

1. energy can not be created or destroyed; it can only be transformed and transferred

2. every transformation and transfer of energy increases the entropy of the universe

entropy

disorder in a system

• without additional energy input, systems gravitate towards disorder

free energy

portion of system’s ability to do work

• amount of free energy is dependent on composition and the arrangement of components of an object

free energy steps

1. free energy is at its peak, but is unstable and has higher capacity of work

2. free energy is released, less stable, released energy is used to do work

3. free energy is decreased, is more stable, and has less capacity of work

exergonic reactions

net loss of energy, negative, spontaneous/downhill reaction

endergonic reactions

gain of energy, positive, nonspontaneous/uphill reaction

spontaneous reaction

reaction that is energetically favorable/exergonic

how does a cell perform chemical reactions that are not energetically favorable?

• favorable reaction drive the abilities of unfavorable reactions

• ATP is used to help drivee unfavorable reactions

ATP hydrolysis

• releases free energy that can be used to do work

• ATP + H2O —> ADP + P1 + Energy

reaction coupling

allows cells to use energy from ATP hydrolysis to drive energetically unfavorable reactions

ATP regulation cycle

see image

catalyst

chemical agent that speeds up a reactione

enzyme

• protein catalyst

• enzymes allow reactions to occur on the time scale necessary for life processes

transition state

high energy state where molecules are able to react

• some reactions occur slowly even if they’re favorable

activation energy

energy needed to reach transition state

• enzymes can lower activation energy, creating alternative/faster pathways without changing level of free energy

• created by thermal energy and molecular collisions

substrate

a reactant molecule

• an enzyme’s active site allows enzymes to be very specific for a single reaction

catalytic cycle of an enzyme

• substrate binds to active site

• substrate is held in active site by weak interactions

• substrates are coverted to products

• products are spit out

• active site is empty and ready for more substrates to enter

positive regulation

enzyme binds to other factors or is modified in order to reactivate

negative regulation

enzyme activity is blocked by an inhibitor

competitive inhibitor

binds to an active site and prevents substrate from getting in

noncompetitive inhibitor

binds to a different location of an enzyme, altering the shape of the enzyme’s active site

chemical equilibrium

reached when rate of forward reaction is equal to rate of reverse reactions

• concentrations of reactants and products remain essentially stable

• chemical reactions proceed in both directions

  • one direction is often more energetically favorable

over of matter and energy flow

cellular respiration

• includes aerobic and anaerobic respiration, but it’s mainly aerobic

• we will focus on sugar glucose

cellular respiration formula

C₆H₁₂O₆ + 6 O₂ —> 6 CO₂ + 6 H₂O + energy (ATP + heat)

cellular respiration is ____ to combusion

similar

combustion formula

CH₄ + 2 O₂ —> 2 CO₂ + 2 H₂O

reactions of cellular respiration are kept in a ______

non-equilibrium state

oxidation-reduction reactions

chemical reactions based on the transfer of electrons

oxidation

losing electrons

reduction

gaining electronsox

oxidation agent

causes oxidation, gains electrons

reduction agent

causes reducing, loses electron

electron transfer during methane combustion

• carbon is oxidized because it has less of a share of electrons

• oxygen is reduced because it has a greater share of electrons

• reaction proceeds to the right because electrons are at a low energy level when they are closer to oxygen

• CH₄ becomes oxidized into CO2

• 2 O2 becomes reduced into 2 H2O

electron transfer during cellular respiration

• electrons in reactants have a higher energy state than electrons in products

• overall reaction is broken down into a series of redox reactions

• reaction driven to the right for the same reason as methane combustion

• C6H12O6 is oxidized into 6 CO2

• 6 O2 is reduced into H2O

NAD+

functions as a high energy electron shuttle during cellular respiration

• disaccharide

• nicotinamide is nitrogenous base

• NAD+ reduction into NADH ads an extra hydrogen to nicotinamide base

• NADH maintains electrons in a high energy state for use later in cellular respiration

ATP is generated in two different ways

• substrate level phosphorylation

• oxidative phosphorylation

substate level phosphorylation

enzyme transfer a phosphate group from a molecule to ADP

• ( phosphate + substrate —> ADP ) —> product + ATP

• occurs during glycolysis and citric acid cycle

o

oxidative phosphorylation

redox reactions of the electron transport chain are coupled to addition of free phosphate to ADP

• occurs during last stage of respiration

overview of cellular respiration

mitochondrial anatomy

glycolysis

• sugar splitting in cytosol

• glucose (6c) is oxidized into two pyruvate (3c)

• energy investment phase

  • 2 ATP used

• energy payoff phase

  • 4 ATP reformed

  • 2 NADH formed

citric acid cycle

• pyruvate enters mitochondria

• pyruvate is oxidized into acetyl CoA

  • 1 CO2 released

  • 1 NADH formed

• acetyl CoA enters CAC and is coupled to oxaloacetate

• sequentially oxidized

  • 2 CO2 released

  • 3 NADH formed

  • 1 ATP formed

  • 1 FADH2

  • oxaloacetate reformed

oxidative phosphorylation (electron transport chain)

• energy harvested from NADH and FAD2

• high energy electrons transferred down ETC in a series of redox reactions

• energy released coupled to the movement of H+ across membrane

• generates an H+ concentration gradient

• oxygen serves as final electron acceptor

chemiosis

proton diffuse across inner mitochondrial membrane

ATP synthase

couples proton movement to ATP formatin

blocking one reaction inhibits __________

upstream and downstream reactions

ATP production in the absence of oxygen

• oxygen is the terminal electron acceptor of the ETC

• without oxygen, a cell uses other means to generate ATP

anaerobic respiration

some bacteria use a different molecule as the terminal electron acceptor

fermentation

• bacteria, yeast, and other cells

• glycolysis produces ATP and NADH, NADH recyled back to NAD+

  • NADH is recycled to NAD+ by transferring electrons to pyruvate or a pyruvate derivative

    • this removes pyruvate and replenishes the pool of NAD+ allowing glycolysis to continue

exercise and cellular respiration

• ATP is rapidly consumed by muscles during exercise

• the body must replenish ATP supplies in order to continue

• cellular respiration is thus critical to sustained exercise

during exercise

• breathing rate and heart rate increase

• dilation of blood vessels in muscle tissue

• glucose release from glycogen stores

after training

• heart muscle becomes stronger

• increased red blood cell count

• increased blood vessel density

artificial methods

erythropoetin and blood doping to increase red blood cell count