Download respiration - MagnusonScience

Respiration
• Cells - energy to do work - stored
as organic molecules - broken down
to get energy.
• 2 ways - 1 in absence of oxygen
(fermentation).
• Other aerobic (presence of oxygen)
- respiration.
http://www.jracademy.com/~vinjama/2003pics/fermentation%5B1%5D.jpg
• Formula for respiration: C6H12O6 +
6O2 -> 6CO2 + 6H2O + Energy (ATP
+ heat)
• Glucose traditionally used - any
organic molecule can be starting
material.
http://tidepool.st.usm.edu/pix/resp.gif
• ATP (adenosine triphosphate)
molecule used in energy.
• When has phosphate group - like
loaded spring; when loses phosphate
group, energy released.
• Energy comes from conversion of
ATP to ADP and inorganic
phosphate (Pi).
• Animal cells can regenerate ATP
back from Pi and ADP by breaking
down organic molecules.
http://www.med8th.com/nobel/winners/1992/1992-phosphorylation.jpg
• Movement of end phosphorus group
from one molecule to another phosphorylation.
• Temporarily changes shape of
molecule; changes back to original
shape when phosphate leaves.
• Redox reaction - electrons
transferred from 1 reactant to
another.
• Loss of electrons - oxidation.
• Addition of electrons - reduction.
• Electron donor - reducing agent;
electron recipient - oxidizing agent.
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/redox.gif
• Respiration is a redox reaction.
• Glucose oxidized, oxygen reduced,
electrons lose potential energy.
http://bioweb.wku.edu/courses/BIOL115/Wyatt/Metabolism/Respiration.gif
• At key steps, hydrogen atoms
stripped from glucose, passed 1st to
coenzyme (i.e. NAD+)
• Turns NAD+ into NADH.
• NADH shuttles electrons from
food to “top” of chain.
• At “bottom,” oxygen captures
electrons and H+ to form water.
http://kvhs.nbed.nb.ca/gallant/biology/etc.jpg
• 3 stages in respiration: glycolysis,
Krebs cycle, electron transport
chain and oxidative phosphorylation.
• Glycolysis – cytoplasm; Krebs cycle
- mitochondrial matrix.
• Glycolysis and Krebs cycle electrons passed from substrates
to NAD+, forming NADH.
• NADH passes electrons to electron
transport chain (ETC).
• In ETC electrons move from
molecule to molecule until they
combine with O2 and H+ ions to form
water.
http://www.biology.lsu.edu/introbio/spring/Spring%202005/1001/SMP/Overall%20summary%20of%20Glycolysis%20and%20the%20Krebs%20Cycle.jpg
• During ETC energy carried by
electrons stored in mitochondrion
in form used to synthesize ATP via
oxidative phosphorylation.
• ATP also generated in glycolysis and
Krebs cycle by substrate-level
phosphorylation.
• Enzyme transfers phosphate
group from organic molecule
(substrate) to ADP, forming ATP.
*
• 38 ATP produced per mole of
glucose - broken down to CO2 and
H2O by respiration.
• 34 ATP made through oxidative
phosphorylation , 4 ATP from
substrate-level phosphorylation
giving 38 total ATP molecules.
http://www.nismat.org/physcor/atp.gif
• During glycolysis, glucose, 6-C sugar
split into (2) 3-C sugars.
• Net yield from glycolysis 2 ATP and
2 NADH per glucose.
• Glycolysis occurs whether O2
present or not.
• O2 present, pyruvate moves into
Krebs cycle.
• More than ¾ of original energy in
glucose still present in 2 molecules
of pyruvate.
• Pyruvate first modified into acetyl
CoA (actually enters Krebs cycle)
• Each turn of Krebs cycle produces 1
ATP, 3 NADH, 1 FADH2 (electron
carrier) for every molecule of
acetyl CoA.
• Most ATP generated during
respiration comes from energy in
electrons carried by NADH (and
FADH2).
• Energy in these electrons used in
ETC to make ATP.
http://www.stanford.edu/group/hopes/treatmts/ebuffer/f_j03nadhrole.gif
• As electrons move down ETC they
pass energy.
• Transported by either NADH or
FADH2..
• Purpose of ETC - break up energy
into smaller amounts - released in
smaller amounts.
• ATP synthase makes ATP from ADP
and Pi.
• ATP synthesis generated through
proton gradient produced by
movement of electrons along ETC.
• Gradient made when there is higher
concentration in one area.
• Several chain molecules use flow of
electrons to pump H+ from matrix
to intermembrane space.
• Concentration of H+ - proton-motive
force.
• ATP synthase molecules only place
that allow H+ to diffuse back to
matrix of mitochondria.
• Coupling ETC with ATP synthesis
called chemiosmosis - helps
generate ATP.
http://fig.cox.miami.edu/~cmallery/150/makeatp/chemiosmosis.jpg
• Glycolysis produces 2 ATP whether
or not O2 present.
• O2 present, additional ATP
generated when NADH delivers
electrons to ETC.
• If no O2 present - process
fermentation.
http://www.mr-damon.com/experiments/2sp/projects/images/fermentation.jpg
• If NAD+ present, electrons accepted
whether or not O2 present.
• During fermentation, ATP generated by
glycolysis; NAD+ recycled by
transferring electrons from NADH to
pyruvate.
• Aerobic conditions, NADH transfers
electrons to ETC, recycling NAD+.
http://www.botany.unibe.ch/deve/images/ethferm1.gif
• Alcohol fermentation, pyruvate
converted to ethanol in 2 steps.
• 1st, pyruvate converted to 2-C
compound (acetaldehyde) by
removal of CO2.
• 2nd, acetaldehyde reduced by
NADH to ethanol (used in brewery).
• Lactic acid fermentation, pyruvate
reduced directly by NADH to form
lactate (form of lactic acid).
• Muscle cells switch from aerobic
respiration to lactic acid
fermentation to generate ATP when
O2 is scarce.
• Waste – lactate; buildup causes
muscle soreness.
• Aerobic respiration, 38 ATP
generated (2 produced through
anaerobic respiration for 1 molecule
of glucose).
• Some organisms (facultative
anaerobes), including yeast,
bacteria, survive using either
fermentation or respiration.
• Glycolysis can occur with many
organic molecules.
• If not carbohydrate - must be
broken down 1st.
• Fats give 2x as much ATP as
carbohydrates.
http://www.teachnet.ie/gmcweeney/images/fats.JPG
• Respiration monitored through
supply and demand.
• Glycolysis - phosphofructokinase
(enzyme) speeds up or slows down
glycolysis.
• If enzyme active - because ATP
levels low - respiration speeds up.
• http://www.teachersdomain.org/resources/t
dc02/sci/life/cell/mitochondria/index.html