Respiration

Chemical Cycling Cellular Respiration Photosynthesis C6H12O6+O2CO2+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 Reactions Chemical reactions that transfer electrons from one substance to another Oxidation: loss of electrons from a molecule Reduction: gain of electrons

Redox Reactions When electrons change partners, from sugar to oxygen, energy is released Why? 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 Look Glycolysis “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 Look Krebs 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

Chemiosmosis Electron 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 down Glycolysis 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