Cellular Respiration What we do with the glucose from photosynthesis to release the energy stored in it

Stored Energy The amount of energy available in a molecule is measured in calories: the amount of energy needed to warm 1 gram of water by 1 degree C. In food, this energy is measured as kilocalories (kilo =?), or Calories. A gram of carbohydrates has 4 Calories; a gram of fat has 9.

Glucose Glycolysis Cytoplasm Pyruvic acid Electrons carried in NADH Krebs Cycle Electrons carried in NADH and FADH 2 Electron Transport Chain Mitochondrion Cellular respiration

Glucose (C 6 H ) + Oxygen (0 2 ) Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide (CO 2 ) + Water (H 2 O) Cellular Respiration

Glucose To the electron transport chain 2 Pyruvic acid Glycolysis

What if there is no O 2 ? One round of glycolysis doesn’t make much ATP, but it happens really fast and is done by thousands sets of enzymes per second in a cell. Problem: lots of NAD + is needed to pick up electrons and H +. It will run out very quickly. Usually aerobic respiration recycles it.

Aerobic and anaerobic pathways Glucose Glycolysis Krebs cycle Electron transport Fermentation (without oxygen) Alcohol or lactic acid

Lactic acid fermentation Glucose Pyruvic acid Lactic acid

The point of fermentation Fermentation produces no more ATP, but returns NADH to the low energy form NAD + ; this allows glycolysis to continue working. Humans appreciate the products of alcohol fermentation and use them to produce alcohol and to make bread rise.

Good, but not great Glycolysis and fermentation provide enough ATP for single celled organisms, or to power larger organisms for a short time. Bigger organisms need to take advantage of the remaining energy in pyruvic acid.

Why Do We Need So Much ATP? Number of molecules per cell Molecules synthesized per second Molecules of ATP required per second for synthesis DNA ,000 RNA15, ,000 Polysacch arides 39, ,000 Lipids15,000,00012, ,000 Proteins1,700,0001,400.02,120,000

Aerobic respiration Happens in the mitochondrion. 2 Sets of reactions: –Krebs Cycle in mitochondrial matrix –Electron transport chain and chemiosmosis in cristae.

Citric Acid Production The Krebs Cycle

Krebs cycle From each pyruvic acid, a set of chemical reactions produces –2 ATP –NADH –FADH 2 –CO 2 as a byproduct Since we started with 2 pyruvic acids, the cycle runs twice for each glucose.

On to electron transport… The NADH and FADH 2 will be used in the electron transport chain. – H ions will be released from them and electrons will pump the ions – chemiosmosis – just like in photosynthesis!

Electron Transport Hydrogen Ion Movement ATP Production ATP synthase Channel Inner Membrane Matrix Intermembrane Space Electron Transport Chain

Aerobic exercise Aerobic respiration gives us more ATP, but it takes longer to get started. Conditioning increases the number of mitochondria in cells and the number of red blood cells so we are better at carrying oxygen. These factors make aerobic respiration work more efficiently.

Anaerobic exercise? At the beginning of exercise, we rely on glycolysis and fermentation to provide ATP. Lasts about 90 seconds. After long periods of exercise (breathing hard!) we start to run out of oxygen and have to switch back to fermentation for a bit. Lactic acid accumulates in muscles – what happens?