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

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.

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

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

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

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

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.

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

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