Biology Unit 3 Lesson 2

Unit 3

Breathe

Lesson 2: Cellular Respiration

Can You Explain It?

Gather Evidence As you explore the lesson, gather evidence that bonds are broken and new bonds are formed in the process of cellular respiration.

Predict How is the process of fuel combustion in a car engine similar to the way the cells in your body release energy stored in fuel?

Matter and Energy in Cellular Respiration

• Almost all the energy on Earth has its origin in the sun.
• Recall that photosynthesis converts light energy into chemical energy in the form of glucose.
• Chemical bonds must be broken for the stored energy to be released
• In cells, cellular respiration releases chemical energy from sugars to make ATP when oxygen is present

During cellular respiration, is energy absorbed or released? Explain how you know, citing evidence from the graph.

The Process of Cellular Respiration

• The bonds of glucose is broken down to make new bonds in ATP, the energy molecule
• Energy in the form of heat is also released - contributes to why mammals are endothermic.
• Aerobic - requires oxygen; cellular respiration; produces more ATP
• Anaerobic - does not require oxygen; anaerobic respiration

Determine the inputs and outputs of cellular respiration using these: ATP, heat, glucose, carbon dioxide.

The balanced chemical equation for cellular respiration is below. How does this equation represent the law of conservation of matter—that matter cannot be created or destroyed?

A. The inputs are different than the outputs. B. The atoms of hydrogen, oxygen, and carbon are rearranged. C. There are equal numbers of atoms on each side of the equation. D. The number of molecules is the same on either side of the equation.

Mitochondria

• Cellular Respiration occurs in the mitochondria, found in both plant and animal cells
• The folded membrane inside the mitochondria allow for many ATP to be made at once.

Cellular Respiration & Photosynthesis

Photosynthesis and cellular respiration work together as a cycle. Review the two reactions to compare the processes. What is the relationship between photosynthesis and cellular respiration? Draw a table to compare the processes.

All together glycolysis and cellular respiration produce a net gain of up to 38 ATP for every glucose molecule.

Fermentation

• Cells cannot store large amounts of oxygen
• When you are doing high levels of activity, you cannot bring in enough oxygen
• Anaerobic Process - glycolysis and fermentation
• Fermentation does not make ATP, but it allows glycolysis to continue by replenishing the NAD+ molecules
• Lactic acid is a waste product of fermentation and builds up in muscle cells
• When oxygen returns, cellular respiration will continue
• Organisms without mitochondria use fermentation and glycolysis to make ATP

Explain It!

Summarize the evidence that you have gathered to explain how molecules are rearranged and energy is transferred in the process of cellular respiration.

1. Cite evidence to support the claim that bonds are broken and new bonds are formed in each stage of cellular respiration.
2. Explain how energy is transferred from the bonds of food molecules to cellular processes.

Glycolysis

• Takes place in cytoplasm
• Anaerobic
• Breaks down glucose into pyruvate
• Makes 2 ATP

Krebs Cycle

Also called: Citric Acid Cycle

• Continual series of reactions
• Completes breakdown of glucose started in glycolysis
• Transfers high energy electrons to the next step
• Products - 2 ATP; 8 NADH; 2 FADH2, 6 CO2

Electron Transport Chain

• Uses proteins embedded in the inner membrane of the mitochondria
• NADH & FADH2 are used to make ATP
• Water is formed during this stage
• Makes 32 ATP

The input for glycolysis is (ATP / glucose), which is an output of photosynthesis. Glycolysis forms pyruvate, which drives the Krebs cycle to produce (carbon dioxide / water) and ATP. Electrons carry the energy from the broken bonds in the glucose molecule to the new bonds formed in CO2 and H2O. NADH and FADH2 transport these electrons. Cellular respiration is (aerobic / anaerobic) and therefore requires O2, obtained from the atmosphere, as an input used for the electron transport chain. The outputs from this final stage are (carbon dioxide / water) and ATP.