M AIN I DEA : L IVING ORGANISMS OBTAIN ENERGY BY BREAKING DOWN ORGANIC MOLECULES DURING CELLULAR RESPIRATION. Cellular Respiration Notes

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.

T HE 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.

O VERVIEW OF C ELLULAR R ESPIRATION Organisms obtain energy in a process called cellular respiration. The equation for cellular respiration is the opposite of the equation for photosynthesis. Label: C 6 H 12 O6 + 6O 2  6CO 2 + 6H 2 O Carbon Dioxide Water OxygenGlucose ATP

C ELLULAR R ESPIRATION Cellular respiration occurs in two main parts: Glycolysis and Krebs Cycle & Electron Transport - Glycolysis (anaerobic process) Anaerobic processes do not require oxygen. an = without aero = oxygen

Aerobic respiration Aerobic respiration includes the Krebs cycle and electron transport both are aerobic processes. Aerobic processes require oxygen.

C ELLULAR RESPIRATION OCCURS IN THE MITOCHONDRIA, THE ENERGY POWERHOUSE ORGANELLES OF A CELL.

G LYCOLYSIS comes from the Greek words glykys, meaning sweet and lysis, meaning to rupture or break Glucose is broken down in the cytoplasm through the process of glycolysis. Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down. Glycolysis has a net result of two ATP and two pyruvate. Glucose is broken down during glycolysis inside the cytoplasm of cells.

K REBS C YCLE After glycolysis, most of the energy from the glucose is still contained in the pyruvate. The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle (also known as the citric acid cycle ). The Krebs cycle takes place inside the mitochondria of cells. Pyruvate is broken down into carbon dioxide during the Krebs cycle inside the mitochondria of cells.

E LECTRON T RANSPORT In aerobic respiration, electron transport is the final step in the breakdown of glucose. It is the point at which most of the ATP is produced (24 ATP)

E LECTRON TRANSPORT OCCURS ALONG THE MITOCHONDRIAL MEMBRANE.

A NAEROBIC R ESPIRATION Some prokaryotes grow and reproduce without oxygen. The anaerobic pathway that follows glycolysis is fermentation, which occurs in the cytoplasm. Pro – means – before Prokaryotes are simple and do not have a nucleus or membrane bound organelles.

P ROKARYOTES VS E UKARYOTES Some prokaryotes also undergo aerobic respiration. Because prokaryotes do not have mitochondria, there are differences in the process. The main difference involves the use of the prokaryotic cellular membrane as the location of electron transport. In eukaryotic cells, pyruvate is transported to the mitochondria. In prokaryotes, this movement is unnecessary, saving the prokaryotic cell two ATP, and increasing the net total of ATP produced to 38. Pro 38 Eu 36 SMALL PROKARYOTES – More efficient!

T WO M AIN T YPES OF F ERMENTATION : Lactic Acid Fermentation and Alcohol Fermentation

W HEN OXYGEN IS ABSENT OR IN LIMITED SUPPLY, FERMENTATION CAN OCCUR.

L ACTIC A CID F ERMENTATION Skeletal muscles produce lactic acid when the body cannot supply enough oxygen, such as during periods of strenuous exercise. When lactic acid builds up in muscle cells, muscles become fatigued and might feel sore. Lactic acid also is produced by several microorganisms that often are used to produce many foods, including cheese, yogurt, and sour cream.

A LCOHOL F ERMENTATION Alcohol fermentation occurs in yeast and some bacteria.

P HOTOSYNTHESIS AND C ELLULAR R ESPIRATION Photosynthesis and cellular respiration form a cycle in which the products of one metabolic pathway form the reactants of the other metabolic pathway

M ETABOLIC P ATHWAYS Produce and break down simple carbohydrates The products of cellular respiration are the reactants for photosynthesis.

L ESSON S UMMARY Many living organisms use cellular respiration to break down glucose. In the absence of oxygen, cells can sustain glycolysis by fermentation. Cellular respiration with oxygen (aerobic respiration) makes more ATP than anaerobic respiration.