Bellwork question: Why do macromolecules differ in the amount of energy they contain?

Cellular Respiration – an overview Section 9.1

Where do organisms get their energy? Unit – calories 1 calorie = amount of energy required to increase 1 gram of water by 1 degrees Celsius 1000 calories – 1 Calorie Cells can use all sorts of food as energy

Examples 1 gram of sugar = 3811 calories (3.8 Calories) 1 gram of beef fat = 8893 calories (8.9 Calories) Carbohydrates and proteins – approximately 4000 (4 Calories) calories per gram Fats- approximately 9000 calories (9 Calories) per gram

Cellular respiration overview It does not happen instantaneously!

Stages of cellular respiration Cells can use variety of food sources Glucose most important Only a small amount of energy is ‘liberated’ during glycolysis Pyruvic acid enters in Krebs cycle Most energy generated in electron transport chain

Role of oxygen Oxygen required at the end of the electron transport chain If cell needs energy it needs oxygen We need to breather to respire Cellular respiration with oxygen is aerobic Krebs cycle Electron transport chain Occur in mitochondria Glycolysis is anaerobic Occurs in cell cytoplasm Can continue without oxygen – fermentation Keeps glycolysis running

Photosynthesis vs Repsiration Photosynthesis removes CO2 Respiration replaces CO2 Photosynthesis releases oxygen Respiration requires oxygen Virtually all living things respire, but only plants and some bacteria can photosynthesize

Bellwork: Why does glycolysis have to occur before the Krebs cycle?

The process of cellular respiration Section 9.2