Cellular Respiration Chapter 8.3

Main Idea Living organisms obtain energy by breaking down organic molecules during cellular respiration

Real-World Connection Monarch butterflies must constantly feed on nectar from flowers to provide energy to sustain themselves during their winter migration to parts of Mexico and California each year.

Similarly, humans and other living organisms need reliable food sources to supply energy to survive and grow.

Cellular Respiration The function of cellular respiration is to harvest electrons from carbon compounds, such as glucose, and use that energy to make ATP. ATP is used to provide energy for cells to do work.

CHEMICAL EQUATION C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy (notice this equations is the opposite of photosynthesis…weird!)

SING ALONG TIME Sugar Sugar Sugar

Cellular Respiration (CR) CR occurs in two main parts: Glycolysis and aerobic respiration Glycolysis is an anaerobic process, which means it does not require oxygen

Aerobic respiration includes the Krebs cycle and electron transport chain, which does require oxygen

Glycolysis Glucose (sugar) is broken down in the cytoplasm through the process of glycolysis Glucose (6 carbon compound) is broken down into 2 pyruvate (3 carbon compound) molecules

For every glycolysis reaction 4 molecules of ATP are produced, but there is only a net yield of 2 Because glycolysis begins with the input of 2 molecules of ATP 4 total ATP- 2 input= net yield of 2 ATP

Krebs Cycle Glycolysis has a net result of 2 ATP and 2 pyruvate molecules. Most of the energy from the glucose is still contained in the pyruvate

In the presences of oxygen, pyruvate is transported to the mitochondria and is eventually converted to carbon dioxide The Krebs cycle is also known as the Tri- carboxylic acid (TCA) cycle and the citric acid cycle.

Steps of the Krebs Cycle Pyruvate joins with a co-enzyme called acetyl CoA Acetyl CoA binds with citric acid Citric acid breaks down into 2 molecules of carbon dioxide and 1 ATP

Finally, acetyl CoA and citric acid are generated and the cycle continues Recall that two molecules of pyruvate are formed during glycolysis, resulting in how many turns of the Krebs cycle????? AND THE ANSWER IS…………

The net yield of the Krebs cycle is 2 ATP, 8 NADH, and 2 FADH2

Electron Transport Electron transport is the final step in the breakdown of glucose High-energy electrons and hydrogen ions from NADA and FADH2 produced in the Krebs cycle are used to convert ADP to ATP

NADH and FADH2 release electrons, the energy carriers are converted to NAD+ and FAD, and H+ ions are released into the mitochondria H+ ions diffuse down their concentration gradient back across the membrane through ATP synthase molecules

Oxygen is the final electron acceptor in the electron transport chain The electron transport chain produces 24 ATP

Overall ATP Production One molecule of glucose yields 36 ATP in eukaryotes (what are eukaryotes??) One molecule of glucose yields 38 ATP in prokaryotes (what are prokayotes??)

Anaerobic Respiration The anaerobic pathway that follows glycolysis is fermentation There are 2 main types of fermentation – Lactic acid fermentation – Alcohol fermentation

Lactic Acid Fermentation Enzymes convert the pyruvate made during glycolysis to lactic acid Skeletal muscle produces lactic acid when the body cannot supply enough oxygen, such as during strenuous exercise

Lactic acid build up results in fatigued and sore muscles Lactic acid also is produced by several micro-organisms that often are used to produce many foods, including cheese, yogurt, and sour cream

Alcohol Fermentation Alcohol fermentation occurs in yeast and some bacteria During fermentation, pyruvate is converted to ethyl alcohol and carbon dioxide