CHAPTER 8 Cellular Energy

8-3 Cellular Respiration

JOURNAL Explain how Cellular Respiration is related to Photosynthesis.

Vocabulary anaerobic process aerobic respiration aerobic process Cellular Energy Vocabulary anaerobic process aerobic respiration aerobic process glycolysis Krebs cycle fermentation

Cellular Respiration

Cellular Respiration: “What” The process that releases energy from food in the presence of oxygen. Opposite of photosynthesis! Sugar + oxygen  carbon dioxide + water + energy

Cellular Respiration: “Why” Function: Harvest electrons from carbon compounds (glucose), and use that energy to make ATP, which provides energy for cells to do work.

Cellular Respiration: “Where”

Cellular Respiration: “How” Cellular Energy Occurs in two main parts. Glycolysis Aerobic respiration

Aerobic vs. Anaerobic Aerobic – pathways that require oxygen Anaerobic – does not directly require oxygen

Cellular Respiration Overview Video

Glycolysis You must put energy in to get energy out! Glucose is broken down in the cytoplasm through the anaerobic process of glycolysis.

Glycolysis Glycolysis has a net result of two ATP, two NADH and two pyruvate. Most of the energy from the glucose is still contained in the pyruvate.

Glycolysis Review Where does glycolysis take place? Cytoplasm What are the energy carrying molecules in involved in glycolysis? ATP, NADH What is the main molecule being broken down? What is it broken down into? Glucose  pyruvate (pyruvic acid) Does glycolysis require oxygen? No. It is anaerobic.

In the presence of oxygen, pyruvate is transported into the mitochondrial matrix, where it is eventually converted to carbon dioxide KREB’S CYCLE

Krebs Cycle The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle.

Pyruvate reacts with CoA to from acetyl-CoA Pyruvate reacts with CoA to from acetyl-CoA. CO2 is released and NADH is formed. Acetyl CoA forms Citric Acid Citric Acid is broken down. Two CO2 molecules are released. One ATP, three NADH and one FADH2 are formed. Remember, two pyruvates are formed during glycolysis. Both go through the Kreb’s cycle. So… for every ONE glucose molecule, there are two “turns” of the Kreb’s Cycle!

Krebs Cycle Net Yield = -six CO2, -two ATP, -eight NADH, -two FADH2 (Citric Acid Cycle) Net Yield = -six CO2, -two ATP, -eight NADH, -two FADH2

Electron Transport Final step in the breakdown of glucose Point at which (the most) ATP is produced Produces 32 ATP

In eukaryotes, one molecule of glucose yields 36 ATP under ideal conditions

Cellular Respiration Totals

So what happens when oxygen is not available? The cell can still undergo Glycolysis to produce ATP, but without oxygen the electron transport chain does not work, so waste builds up.

Anaerobic Respiration (Fermentation) Cellular Energy Anaerobic Respiration (Fermentation) The anaerobic pathway that follows glycolysis Occurs in the cytoplasm Two main types Lactic acid fermentation Alcohol fermentation

Lactic Acid Alcohol Produced by skeletal muscles when the body can’t supply enough oxygen; causes fatigue and soreness Occurs in yeast and some bacteria

Still Unsure? Watch this three-part series. Part 1: Introduction and Glycolysis Part 2: The Kreb’s Cycle Part 3: Electron Transport Chain

JOURNAL List the three parts of cellular respiration. At which stage is oxygen crucial? What type of pathway is this (aerobic or anaerobic)?

Comparing Photosynthesis and Cellular Respiration Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food.

Comparing photosynthesis and cellular respiration

Quick lab, page 264 How does exercise affect disposal of wastes from cellular respiration? After completing the lab, read pages 264-265 in your textbook for further information.

journal Create a table or diagram that demonstrates the processes of photosynthesis and cellular respiration. Try to name what type of organism each process occurs in, which organelle each process takes place in, what is needed for each process and what is a result of each process (what goes in, what comes out?)