John Bowne High School



Cellular Respiration

Aim: What is cellular respiration?

Key idea:

All the life processes require a constant supply of energy. Organisms obtain the energy they need by releasing the chemical energy stored in nutrients. The process of doing this is called respiration. Respiration involves a complex series of chemical reactions. Respiration involves the processes of aerobic and anaerobic respiration.

Assessing prior knowledge / Do Now – Use T-chart.

What do you know about cellular respiration? / What questions do you have about cellular respiration?

Motivation: Brainstorm technique:

-Why do we eat food? Especially carbohydrates like bread and potatoes.

-Why do we breathe?

Introduction to understanding:

-Respiration is the process by which organisms obtain the energy they need by releasing chemical energy stored in nutrients.

-Respiration includes all the processes by which the chemical bond energy in food molecules is converted or changes to a form usable by the organism. The chemical bond energy stored food is converted into the bonds of the energy carrier called ATP ( adenosine triphosphate). ATP is synthesized (made) from ADP ( adenosine diphosphate) and phosphate (P). The energy stored in ATP is released for use in the cell by hydrolysis ( to put water in the reaction) of the ATP to ADP and phosphate.

-These two processes, which are controlled by enzymes called ATP-ase, can be represented by the reversible reaction: H20 + ATP----enzyme ATP-ase----ADP + P + energy

-Q / What do we take in, when breathing?

-Respiration uses two processes to obtain energy: 1-aerobic, and 2-anaerobic respiration.

-If free oxygen is used, the process is called aerobic respiration.

-If free oxygen is not involved, it is called anaerobic respiration

Development of understanding:

-Q / What is the function of the organelle called mitochondria?

-The chemical reactions that release the energy in food molecules and store it in ATP take place inside the cells of the organism. In aerobic respiration, the reactions to produces ATP occurs in the mitochondria, where the necessary enzymes are present. In anaerobic respiration the reactions to produces ATP occurs in the cell, but not in the mitochondria.

-Q / What happens to your muscle, when you exercise too much?

-There is pain and fatigue in the area of the muscle.

-This is caused by the accumulation of lactic acid in the muscle by the lack of oxygen.

-When there is a lack of oxygen for the cells of the body, the cells can use anaerobic respiration for a limited time to produce energy (ATP), but this process is not efficient enough to produce ATP in quantity.

-Anaerobic respiration breaks down glucose (carbohydrate molecule) to either lactic acid or alcohol, and release carbon dioxide. Lactic acid is produced in muscle cells when oxygen is lacking. The accumulation of lactic acid is associated with muscle fatigue.

-Q / How is cheese, yogurt, and alcoholic beverages produced?

-Fermentation use anaerobic respiration to produce lactic acid or alcohol, and release carbon dioxide.

-Fermentation in special bacteria produces lactic acid that is used in diary products, such as yogurt.

-Fermentation in yeast produces alcohol and carbon dioxide. These end products are used in brewing alcoholic beverages and in baking. Where the carbon dioxide causes the dough to rise.

Glucose-------enzyme---------2 lactic acid + 2ATP

(in bacteria and in muscle cells lacking oxygen)

Glucose-------enzyme---------2 alcohol + 2 carbon dioxide + 2 ATP

(in yeast)

-In anaerobic respiration only 2 ATP are produced for each molecule of glucose. The end products, lactic acid or alcohol, still contain most of the chemical bond energy of the original glucose.

-The chemical reactions:

-The first series of reactions in anaerobic respiration converts each molecule of glucose to two molecules of a 3-carbon compound called pyruvic acid. Four molecules of ATP are produced during these reactions. However, two molecules of ATP are needed to activate the series of reactions. Therefore, there is a net output of only 2 ATP per molecule of glucose.

-The pyruvic acid is then converted either to lactic acid alone, or to alcohol and carbon dioxide, with no further energy change.

Glucose + 2ATP----enzyme----2 pyruvic acid + 4 ATP

^

2 lactic acid 2 alcohol + 2 carbon dioxide

-Q / What is aerobic respiration use for? Or What is the function of aerobic respiration?

-In aerobic respiration, molecules of food such as glucose are broken down completely to carbon dioxide and water in a series of steps by the action of enzymes. The bond energy of the glucose if gradually released, forming 36 molecules of ATP for each molecule of glucose.

-Oxidation – reduction reactions.

-The steps of aerobic cellular respiration involve the removal of hydrogen atoms and the release of carbon dioxide. The removal of either hydrogen atoms or electrons from a substance is a type of chemical reaction called oxidation. The transfer of hydrogen atoms or electrons to a substance is reduction. As glucose is oxidized in aerobic respiration, hydrogen atoms or their electrons are transferred from one compound to another in a series of oxidation-reduction reactions. During some of these transfer, energy is extracted and used to synthesis (made) ATP.

-Q / What is aerobic respiration?

-The role of free oxygen is to be the final acceptor of the hydrogen atoms. The oxygen combines with the hydrogen, forming water.

-The overall process of aerobic respiration is :

C6H12O6 (glucose) + 6O2----enzyme----6H2O(water) + 6CO2 (carbon dioxide) + 36ATP

-The phases of aerobic respiration: Krebs cycle

-Aerobic respiration begins with an anaerobic stage in which glucose is converted to pyruvic acid, and there is a net output of 2 ATP per glucose molecule. These reactions take place in the cytoplasm outside the mitochondria, where the necessary enzymes are present. This process is called glycolysis.

-The pyruvic acid produced in the anaerobic phase then enters the mitochondrion. In the mitochondrion, The pyruvic acid is further oxidized in a series of reactions that release enough energy to form an additional 34ATP molecules. Carbon dioxide is produced by some of the intermediate reactions. Free oxygen acts as the final acceptor of the hydrogen released by the oxidation reactions, forming water. The net gain from the complete oxidation of one glucose molecule by aerobic cellular respiration is 36 ATP.

Glucose + 2ATP------enzyme-----2 pyruvic acid + 2ATP

2 pyruvic acid + oxygen-----enzyme------carbon dioxide + water + 34ATP

Net output: 36ATP per glucose molecule.

Homework: Read your notes, and answer questions 1,4,and 5.

Summary:

1-What is aerobic respiration?

2-What is anaerobic respiration?

3-What is the purpose of aerobic and anaerobic respiration?

4-How much ATP is produced in anaerobic respiration?

5-How much ATP is produced in aerobic respiration?

6-What is the net output of ATP per molecule of glucose?

7-What is the function of the organelle called mitochondria?

8-Why do your muscles hurt or tired after a long exercise?

9-How is alcohol beverages produced?

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