Chapter 3, Section 4

Respiration

What Is Respiration? Respiration: cells break down simple

food molecules such as sugar and release the energy they contain

Cells store energy in the form of carbohydrates 1. sugars2. starches

Storing and Releasing Energy

Energy stored in cells is like a savings account

During photosynthesis, plants capture energy from sunlight and “save” it

When cells need energy, they “withdraw” it by breaking down the carbohydrates for energy

Breathing and Respiration

Respiration can mean two different things:1. Breathing: moving air in and out

of your lungs

2. Cellular Respiration: process that takes place inside cells

The Two Stages of Respiration

Stage 1o Takes place in the cytoplasm of the

organism’s cellso Molecules of glucose are broken down into

smaller moleculeso NO oxygen is involved and only a small

amount of energy is released

Stage 2o Takes place in mitochondriao Small molecules are broken down into even

smaller moleculeso Require oxygen and release a great deal of

energy

The Respiration Equation

Raw materials

Products

sugar oxygen water carbon dioxide

Comparing Photosynthesis and Respiration

Can you notice anything familiar about the equation for respiration?o It is the opposite of the equation for

photosynthesis

During photosynthesis, carbon dioxide and water are used to produce sugars

During respiration, sugar glucose and oxygen are used to produce carbon dioxide and water

These two processes form a cycle that keeps the levels of oxygen and carbon dioxide fairly constant in Earth’s atmosphere

Fermentation an energy releasing process that does

not require oxygen

fermentation releases less energy than respiration

Two Types of Fermentation

Alcoholic Fermentationo Occurs when yeast and some other single-celled

organisms breakdown sugarso The products are: alcohol, carbon dioxide, and

small amount of energyo Important to bakers and brewers

Lactic-Acid Fermentationo Muscle cells use up the oxygen faster than it could be replacedo One product of this type of fermentation is lactic

acido It is a painful sensation in your muscles, muscles

feels weak and sore