Ch. 9 Sec. 1. Chemical Pathways. Animal Cells. Food serves as a source of raw materials for the cells in the body and as a source of energy. . Animal. Plant. Mitochondrion. Plant Cells. Fig. 9-1 pg. 221. Intermembrane space.
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Ch. 9 Sec. 1 Chemical Pathways
Animal Cells Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Plant Mitochondrion Plant Cells Fig. 9-1 pg. 221
Intermembrane space Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria. Outer membrane Inner membrane Matrix
I. Chemical Energy and Food • C6H12O6 1. One gram, when burned in the presence of oxygen, releases 3811 calories of heat energy 2. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 Co 3. Equivalent to 3.8 Calories (food labels)
B. Glycolysis – 1st step in releasing energy of glucose Glucose is broken down Releases a small amount of energy Yields 2 molecules of pyruvic acid
II. Overview of Cellular Respiration • If oxygen is present, glycolysis is followed by the Krebs cycle and the electron transport chain. • Glycolysis, the Krebs cycle, and the electron transport chain make up a process called cellular respiration
A. Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
B. The equation for cellular respiration is: 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy oxygen + glucose → carbon dioxide + water + Energy
C. Each of the three stages of cellular respiration captures some of the chemical energy available in food molecules and uses it to produce ATP.
Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place in the mitochondria. Glycolysis Cytoplasm Mitochondrion
Glycolysis occurs in the • mitochondria. • cytoplasm. • nucleus. • chloroplasts.
III. Glycolysis the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.
A. ATP Production • At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction (AKA activation energy) • When glycolysis is complete, 4 ATP molecules have been produced (using energy released during glucose breakdown) • Net gain of 2 ATP molecules. • Also produces 4 high-energy electrons 2 ATP 2 ADP 4 ADP 4 ATP 2 Pyruvic acid
B. NADH Production • The reaction of glycolysis that removes 4 high-energy electrons, passes them to an electron carrier called NAD+. • Each NAD+ accepts a pair of high-energy electrons and becomes an NADH molecule. 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid 2
3. The NADH molecule holds the electrons until they can be transferred to other molecules. 4 ADP 2 ATP 2 ADP 4 ATP 2NAD+ 2 Pyruvic acid 2 To the electrontransport chain
C. The Advantages of Glycolysis • The process of glycolysis is so fast that cells can produce thousands of ATP molecules in a few milliseconds. • Glycolysis does not require oxygen.
IV. Fermentation - releases energy from food molecules by producing ATP in the absence of oxygen (anaerobic)
NADH to NAD+ 1. High-energy electrons passed back to pyruvic acid. 2. Allows glycolysis to continue producing a steady supply of ATP.
Fermentation releases energy from food molecules in the absence of • oxygen. • glucose. • NADH. • alcohol.
The two main types of fermentation are lactic acid fermentation and alcoholic fermentation
B. Alcoholic Fermentation • Yeasts and a few other microorganisms • Equation for alcoholic fermentation after glycolysis: pyruvic acid + NADH → alcohol + CO2 + NAD+ 3. Causes bread dough to rise a. CO2 bubbles b. Alcohol evaporates during baking
C. Lactic Acid Fermentation 1. In many cells, pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid. 2. Regenerates NAD+ so that glycolysis can continue
3. Equation for lactic acid fermentation after glycolysis is: pyruvic acid + NADH → lactic acid + NAD+
4. Produced in muscles when O2 runs out Results in build-up of lactic acid Causes soreness
The first step in fermentation is always • lactic acid production. • the Krebs cycle. • glycolysis. • alcohol production.
9–1 Chemical Pathways Food is the energy source for cells. The energy in food is measured in calories. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie (capital C) used on food labels is equal to 1000 calories. Cells do not burn glucose or other food compounds. They gradually release the energy.
The process begins with a pathway called glycolysis.Glycolysis is the process in which a glucose molecule is split in half. This forms two molecules of pyruvic acid, a 3-carbon compound. Glycolysis takes place in the cytoplasm of a cell.Through glycolysis, the cell gains 2 ATP molecules. In addition, the electron carrier NAD+ accepts a pair of high-energy electrons, producing NADH. By doing this, NAD+ helps pass energy from glucose to other pathways in the cell.
When oxygen is not present, fermentation follows glycolysis. Fermentation releases energy from food molecules by forming ATP. Fermentation does not need oxygen, so it is said to be anaerobic. During fermentation, cells convert NADH back into the electron carrier NAD+ that is needed for glycolysis. This lets glycolysis continue to make a steady supply of ATP.
The two types of fermentation are alcoholic fermentation and lactic acid fermentation.• Yeasts and a few other microorganisms carry out alcoholic fermentation. The equation for alcoholic fermentation after glycolysis is:pyruvic acid + NADH ➝ alcohol + CO2 + NAD+
• Lactic acid fermentation occurs in muscles during rapid exercise. The equation for lactic acid fermentation after glycolysis is: pyruvic acid + NADH ➝ lactic acid + NAD+ If oxygen is present, the Krebs cycle and electron transport chain follow glycolysis. Together, these pathways make up cellular respiration.
Cellular respiration is the process thatreleases energy by breaking down glucose and other foodmolecules in the presence of oxygen.Cellular respiration takes place in mitochondria. The equation for cellular respiration is:6O2 + C6H12O6 ➝ 6CO2 + 6H2O + EnergyOxygen + glucose ➝ carbon dioxide + water + Energy