Cellular Respiration

I. How do living things turn food into energy? How it begins in humans: 1. The nervous system senses that nutrients are needed and excretes chemical signals that increase appetite. 2. The organism eats food, and the food is broken down into simple molecules in the digestive system (metabolism). 3. Nutrients such as carbohydrates and proteins are transported through intestinal membranes into the circulatory system.

I. How do living things turn food into energy?

4. Blood carries nutrients to cells. 5. Nutrients are transported into cells. Sugar is transported into the cell with the help of a molecule called insulin.

I. How do living things turn food into energy? Once sugar enters the cell, the cell must convert it to usable energy. The process of converting nutrients into ATP is called cellular respiration. Do plants carry out cellular respiration? _____________

I. How do living things turn food into energy? Yes! ALL LIVING THINGS CARRY OUT CELLULAR RESPIRATION! (Even plants)

II. Where is this happening? Cellular respiration takes place in specialized organelles called mitochondria. Typical animal cells have 1000 to 2000 mitochondria per cell.

II. Where is this happening? Mitochondria are specialized for energy conversion. The inner membrane of mitochondria is highly convoluted, forming folds called cristae. Inside the membrane are proteins that carry out cellular respiration.

Why do mitochondria have so many folds in their membranes? Why do mitochondria have so many folds in their membranes? ________________________________________ ________________________________________

III. So how does it happen exactly? 1. Glycolysis - Happens in the cytoplasm of the cell. One glucose molecule is split into 2 molecules of pyruvate - During this process, 2 ATP are made. Hydrogen atoms are also removed from the glucose molecule by NAD+, and NADH is formed. 2. Transition reaction - Pyruvate is transported into the mitochondria, where it is converted to a molecule called acetyl CoA. During this process, 2 NADH molecules are made.

1.

2.

III. So how does it happen exactly? 3. Krebs cycle – Happens in the matrix of the mitochondria. In the presence of oxygen, acetyl CoA is converted to carbon dioxide. In the process, 2 ATP are made. Other molecules called FADH2 and NADH are made. Carbon dioxide is given off as waste. 4. Electron transport chain – Happens in the inner membrane. Consists of a series of carrier molecules which pass electrons from a high- energy compound to a final low-energy electron acceptor (oxygen). Energy is released during these oxidation-reduction reactions to produce 32 ATP. Water is also released as waste.

3.

4. electron transport chain electron transport chainelectron transport chain

III. So how does it happen exactly? How many total ATP molecules are made from one glucose molecule? ___________

IV. What is ATP used for? Everything! Any cell process that requires energy requires ATP. Cells use ATP to transport materials around the cell, construct building blocks of the cell, communicate with other cells, and do many many other jobs.

V. What if there’s no oxygen around? Can cells still get energy from nutrients? Yes! When conditions are anaerobic (no oxygen), cells can still break down sugar and make ATP. This process is called fermentation.

V. What if there’s no oxygen around? Can cells still get energy from nutrients? Fermentation is not very efficient, though, because only 2 ATP are made for every molecule of glucose. The final product of fermentation is either alcohol (like yeast make) or lactate (which can make your muscles sore).

To Summarize: C 6 H 12 O 6 + O 2  CO 2 + H 2 O + ATP