Cellular Respiration Overview

April 1, 2013

Learning Targets

• Students will be able to explain where

organisms get the energy they need for life

processes.

• Students will be able to define cellular

respiration.

• Students will be able to compare

photosynthesis and cellular respiration.

Bell Work

• Watch the Chapter Mystery video on page 431

at the beginning of Chapter 9.

• What adaptations do you think whales have

that allow them to go so long without

breathing?

Where do organisms get energy?

• Autotrophs – make their own food through photosynthesis.

• Heterotrophs – must consume other organisms for food.

• Food molecules contain chemical energy that is released when chemical bonds are broken.

Energy in food

• How much energy is in food?

• Varies with the type of food.– Depends on chemical

structure

• Energy in food is described in units of calories.– Amount of energy

needed to raise the temperature of 1 gram of water 1 degree Celsius.

Cells and Food Energy

• Cells break down food slowly, capturing

chemical energy at key steps

• Cellular respiration is the process that

releases energy from food in the presence of

oxygen.

Cellular Respiration

• Overall reaction for cellular respiration

• Requires oxygen and food (such as glucose)

Cellular Respiration

• Happens in a series of steps to control the

energy being released from the food.

• Energy from the reactions is stored as ATP.

Writing Break

• Do plants undergo cellular respiration? What

organelle(s) do they have that helps you

determine the answer?

Stages of Cellular Respiration

• Three main stages:– Glycolysis

– Krebs cycle

– Electron transport chain

• Most of the energy comes from the electron transport chain

Oxygen and Energy

• Oxygen is a powerful electron acceptor.

• Aerobic processes – require oxygen, such as Krebs cycle and the electron transport chain.

• Anaerobic processes – do not require oxygen, such as glycolysis

• In the absence of oxygen, fermentation keeps glycolysis going to provide ATP for cellular activity

Mitochondria

• Mitochondria are organelles that convert

chemical energy in food to usable energy for

the cell.

• Glycolysis generally occurs in the cytoplasm,

but the Krebs cycle and the electron transport

chain take place inside the mitochondria.

Writing Break

• Make a flowchart that shows the different

steps of cellular respiration.

• Chapter mystery clue – If whales remain

underwater for 45 minutes or more, do you

think they rely primarily on aerobic or

anaerobic pathways?

Photosynthesis and Cellular Respiration

• Photosynthesis removes CO2 from the air and cellular respiration puts it back. Photosynthesis releases O2 into the atmosphere and cellular respiration uses that oxygen to release energy from food.

Assessment

• Questions:

– Why do food molecules differ in the amount of energy they contain?

– Write the overall reaction for cellular respiration.

– In what ways are cellular respiration and photosynthesis considered opposite processes?

– The Greek word glukus means “sweet” and the Latin word lysis refers to a process of loosening or decomposing. Based on this information, write a definition for the word glycolysis.

• Analyzing Data activity – page 433 “You are what you eat”