1. Your body does it millions of times at once!
Respiration
Your body does it millions of times at once!

2. What is respiration?
Physiological definition: The act of exchanging gasses with the environment
mammals : inhale air, exhale CO2
Biochemical definition aka cellular respiration: The release of energy from glucose or other organic substances inside living cells.

3. Respiration in mammals
Air is inhaled through the lungs (breathing)
Hemoglobin molecules inside red blood cells capture O2
Blood with O2 is pumped through the body to all tissues
In capillaries, cells release CO2 into the blood and pick up fresh O2
O2 diffuses into the cell, and is used in the mitochondria to break down glucose molecules and make ATP

4. How does O2 get into the blood?
Lungs are mostly a collection of tiny hollow sacs called alveoli, and they are surrounded by tiny blood vessels called capillaries
As you inhale, the alveoli fill up with air, which contains O2
Because there is more O2 in the lungs than in the blood, O2 diffuses down its concentration gradient from the alveoli into red blood cells
Blood coming from the lungs is red because it is filled with O2

6. How does O2 get into cells?
Cells and tissues receive all nutrients (food, O2, water) in capillary beds
When blood from the lungs reaches cells, there are many more O2 molecules in the blood than in the cell, and O2 (green) diffuses into cells down its concentration gradient
At the same time, waste CO2 (blue) travels out of those cells and into the blood where there is almost no CO2

7. How do animal cells use O2?
Cells break down glucose molecules to create ATP, the energy storing molecule
O2 is a crucial molecule in this process
Aerobic respiration
Takes place in the mitochondria of animal cells
Making energy from glucose with the use of O2
What our bodies do 95% of the time

8. What happens without O2 Anaerobic respiration
Making energy by breaking down glucose without O2
Much less efficient, takes place during emergencies when not enough O2 is available
Produces alcohol in yeasts
Produces lactic acid in mammals
EX: When running away from a tiger, your muscles need lots of ATP FAST, but your heart can’t pump enough O2 for aerobic respiration to produce enough ATP. Your muscles switch to anaerobic respiration, and the next day, all that lactic acid makes that tissue sore.

9. How does your body use ATP?
ATP is the most important energy provider for cells in all tissues
Breaking a phosphate group off of ATP releases energy used in other reactions in the cell
ATP  ADP + Pi
ADP is recycled and the Pi group is put back on during cellular respiration

10. Using ATP during active transport
ATP is hydrolyzed (broken) into ADP + Pi by the Na+/K+ pump
Energy released during ATP hydrolysis is used to make Na+ and K+ ions move against their concentration gradients
ADP is transported back to the mitochondria to be recycled into ATP during cellular respiration