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Respiration
Chemical Cycling
Cellular Respiration C6H12O6+O2CO2+H2O
Photosynthesis CO2+H2O C6H12O6+O2
Why do we need to eat food?
Respiration and Breathing
How does cellular respiration relate to breathing?
How exactly is O2 used in the cells?
Why exactly do we breath out CO2?
Cellular Reactions
What type of bond holds food molecules together?
Cellular Reactions
What type of bond holds food molecules together?Covalent bonds: sharing of electrons
When looking at the formulas, we are looking at the transfers of electrons
Redox ReactionsChemical reactions that transfer electrons from one substance to anotherOxidation: loss of electrons from a moleculeReduction: gain of electrons
Redox ReactionsWhen electrons change partners, from sugar to oxygen, energy is releasedWhy?Because electrons are being transferred
from a less stable molecule (sugar) to a more stable molecule (O2)
Remember, the less stable the molecule, the more potential energy
O2 is one of the most stable molecules and its used by cells to cause redox reactions
Redox Reactions
As electrons are passed from a less stable to a more stable molecule, energy is released
This energy is used to recycle ADP to ATP
Cells Must Be Efficient
What would happen if our cells burn glucose (releasing electrons) all at once?
Redox Reactions
One Way We Regenerate ATP
The Fast Way!
A Closer Look
Cellular Respiration has three main stages Glycolysis Krebs Cycle Electron Transport
Chain
You need to know: The purpose of each
stage Where it takes place
A Closer LookGlycolysis “sugar splitting” Glucose is split in two Makes it easier to
harvest electrons in the glucose molecule
Takes place in cytosol Because glucose is split
(less stable to more stable), a little energy is released to make ATP
Glycolysis Summary
Glycolysis Krebs Cycle
Pyruvic Acid Two molecules from
glycolysis (cytoplasm) Enters mitochondria PA does not enter
Krebs cycle Two Acetyl-CoA
Pyruvate Processing
A Closer LookKrebs Cycle (Citric Acid Cycle) Completely strips the split sugar
molecules of their electrons Electrons are carried off by
NADH & FADH2
A waste product is produced (CO2)
A small amount of energy is used to make ATP
Takes place in mitochondria
ChemiosmosisElectron Transport Chain Electrons captured by
NADH are passed down a chain of proteins
O2 is the final electron acceptor (most stable)
Energy is released as electrons are passed down the chain to O2
This energy is used to make ATP….but how?
The ETC: Review
ATP Synthase
Summary
What If O2 is Absent?
When muscles are over worked, they run out of O2
Without O2, the Krebs Cycle and ETC shut downGlycolysis produces small amounts of energy and lactic acid (ethyl alcohol)
Lactic Acid
Summary
We need the electrons in food to drive the synthesis of ATP
We need O2 because it’s a stable electron acceptor and therefore runs the ETC
CO2 is a waste product produced after foods have been completely stripped of their electrons (exhale out lungs)
Cellular respiration is a three stage process