PDF CHAPTER 9 - CELLULAR RESPIRATION - North Allegheny

[Pages:16]CHAPTER 6 CELLULAR RESPIRATION

Chemical Energy In Food

Purpose of food:

Source of raw materials used to make new molecules

Source of energy

calorie ? the amount of energy needed to raise the temperature of one gram of water one degree Celsius.

Cells don't burn glucose but gradually release the energy from it.

Glycolysis ? chemical pathway that begins the process of releasing the energy in glucose.

Cellular Respiration Overview

Cellular Respiration ? the process that releases energy by breaking down food molecules in the presence of oxygen. Contains 3 Pathways: Glycolysis Krebs cycle Electron transport The equation for cellular respiration is:

6O2 + C6H12O6 6CO2 + 6H2O + ENERGY (ATP)

Cellular Respiration overview

If cellular respiration took place in one step, all the energy would be released at once and most would be lost as heat.

PROBLEM: The cell has to find a way to trap the energy a little bit at a time.

SOLUTION: Each of the three stages of cellular respiration captures some of the chemical energy available in food molecules and uses it to produce ATP or energy.

Step 1: Glycolysis

Takes place in the cytoplasm.

Glycolysis is the process in which 1 molecule of glucose is broken in half, producing 2 molecules of pyruvic acid.

This process has to get things going so it uses 2 stored ATP molecules.

4 ATP molecules are made during glycolysis, so a total of 2 ATP molecules are released by glycolysis as energy.

This is only 2% of the total chemical energy in glucose.

NAD+ is converted to NADH.

Step 1: Glycolysis

Glycolysis is so fast that cells can produce 1000s of ATPs in milliseconds.

Glycolysis does not require oxygen.

OXIDATIVE RESPIRATION

To get the rest of the energy from the food molecules, the cell uses oxygen.

Aerobic ? requires oxygen. The energy-releasing pathways require

oxygen, and that is the reason we need to breathe, to respire. Respiration - process that involves oxygen and breaks down food molecules to release energy.

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