Bio Ch. 6

Photosynthesis vs. Cellular Respiration

Photosynthesis

Process: Photosynthesis occurs in the chloroplasts of plant cells and involves using sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂).Equation: The overall equation can be summarized as:6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.Importance: This process is crucial for life on Earth as it forms the basis of the food chain and is responsible for producing the oxygen we breathe.Location: Photosynthesis takes place in the chloroplasts, containing chlorophyll, which captures sunlight.

Cellular Respiration

Process: Cellular respiration occurs in the mitochondria and is essentially the reverse of photosynthesis. It utilizes oxygen (O₂) to break down the glucose produced during photosynthesis, generating energy (ATP) while releasing carbon dioxide (CO₂) and water (H₂O) as by-products.Equation: The cellular respiration equation can be represented as:C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.Significance: Cellular respiration is critical for providing energy required for cellular processes and maintaining life.

How Our Bodies Use Oxygen

Breathing is vital as it supplies oxygen (O₂), which is transported through the bloodstream to every cell in the body. Cells utilize oxygen in the process of cellular respiration to generate ATP, the energy currency of cells, while simultaneously producing carbon dioxide (CO₂) as a waste product.The blood, once it collects CO₂, returns it to the lungs where it is exhaled. This cycle is essential for maintaining an efficient exchange of gases.

Energy from Food

The food we consume, including sugars, fats, and proteins, serves as fuel for cellular activities. The primary fuel utilized in cellular respiration is glucose (C₆H₁₂O₆), which is metabolized to produce ATP. During this process, cellular respiration captures approximately 34% of the energy available in glucose, with the remainder dissipating as heat, aiding in thermoregulation and body warmth.

Cellular Respiration in 3 Stages

1. Glycolysis

   • Location: Cytoplasm

   • Description: Glycolysis breaks down one molecule of glucose into two molecules of pyruvate, generating 2 ATP and NADH, an electron carrier.

2. Citric Acid Cycle (Krebs Cycle)

   • Location: Mitochondria

   • Description: This cycle processes pyruvate to release CO₂ and produces additional ATP and electron carriers.

3. Electron Transport Chain (ETC)

   • Location: Mitochondria

   • Description: The electrons from NADH and FADH₂ flow through protein complexes, facilitating the production of 28 ATP. Oxygen acts as the final electron acceptor; thus, its availability is crucial for this process.

How ATP is Made

During the Electron Transport Chain, electrons move alongside the membrane, liberating energy that powers the pumping of H+ ions across the membrane. As these ions flow back through ATP synthase, they drive the synthesis of ATP from ADP and inorganic phosphate.

Fermentation (When Oxygen is Low)

In situations where oxygen is scarce, cells can still produce ATP through fermentation:

• Lactic Acid Fermentation: Occurs within muscle cells, producing lactic acid, which can lead to muscle soreness. It is employed in the production of fermented food products such as yogurt and cheese.

• Alcoholic Fermentation: Carried out by yeast, it results in the production of ethanol and CO₂, and is crucial for brewing beer, making wine, and baking bread.Importance of Fermentation: This process is essential during anaerobic conditions, permitting cells to generate energy when oxygen levels are inadequate.

Other Fuel Sources

• Fats are broken down into fatty acids, which can enter the citric acid cycle for energy production.

• Proteins are split into amino acids, which can be converted into molecules that enter cellular respiration pathways.

Regulation of Energy Use

The body finely tunes energy usage based on supply and demand. When amino acids are in excess, cells downregulate metabolic pathways, an adaptive process known as feedback inhibition. This helps in conserving resources and maintaining homeostasis, ensuring the body operates efficiently and effectively.

Chapter 6 Test Study Guide

How Cells Harvest Chemical Energy

This is a brief overview of the topics we covered in Chapter Six, not a comprehensive guide for the Test. You should review this as well as your notes, worksheets, labs, review games, etc.

Big Ideas: 

1. Cellular respiration oxidizes fuel molecules and generates ATP for cellular work. 

2. The main stages of cellular respiration are glycolysis, pyruvate oxidation, and the citric acid cycle, and oxidative phosphorylation

3. Fermentation regenerates NAD+, allowing glycolysis and ATP production to continue without oxygen. 

4. The breakdown pathways of cellular respiration intersect with biosynthetic pathways. 

6.1 Photosynthesis and Cellular Respiration Provide Energy for LIfe

6.2 Breathing Supplies O2 for use in cellular respiration and remove CO2

• Know how photosynthesis and cellular respiration are related 

  • What are the starting materials and products for each process

• How is breathing related to cellular respiration? 

6.3 Cellular Respiration banks energy in ATP molecules

• What is the chemical and word formula for cellular respiration? 

6.4 The human body uses energy from ATP for all its activities

• Compare and contrast a Calorie and a kilocalorie 

6.5 Cells capture energy from electrons “falling” from organic fuels to oxygen

• What is a redox reaction?

  • What is oxidation and reduction?

• What role do electron carriers play in the ETC?

  • How do they pass on their electrons?

6.6 Overview: Cellular respiration occurs in three main stages

• Review the steps of cellular respiration

  • What are the products and reactants of each stage

  • Review Fig 6.6 pg 97

• What is chemiosmosis?

  • How does that relate to the ETC and ATP? 

6.7 Stage 1: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

6.8 Multiple reactions in glycolysis split glucose into two molecules 

• What does glycolysis mean?

• Where does it take place?

• What are the final products of glycolysis?

  • What is an important intermediate?

• What method produces ATP?

• What is the energy investment phase vs energy payoff phase?

6.9 Stage 2: The citric acid cycle complex the energy yielding oxidation of organic molecules 

6.10 The multiple reactions of the citric acid cycle finishes off the dismantling of glucose 

• What is the Citric Acid cycle (Krebs cycle)?

• Where does it take place?

• What is the starting molecule? What are the final products?

  • What are some examples of intermediates?

• What method produces ATP?

6.11 Stage 3: Most ATP production occurs by oxidative phosphorylation 

• What is the Electron Transport Chain?

• Where does it take place?

• What is the starting molecule? What are the final products?

  • What is the role of oxygen in this step?

6.13 Review: Each molecule of glucose yields many molecules of ATP

• Review figure 6.13 pg 104

6.14 Fermentation enables cells to produce ATP without oxygen 

• Compare and contrast aerobic vs anaerobic respiration

• What is lactic acid fermentation?

  • What are the reactants and products?

  • Examples of application

• What is alcoholic fermentation?

  • What are the reactants and products?

  • Examples of application

6.16 Cells use many kinds of organic molecules as fuel for cellular respiration 

• How do molecules other than glucose go through cellular respiration?

  • Lipids and proteins- review 

6.17 Organic molecules from food provide raw materials for biosynthesis 

• Examples of structures made from molecules that aren’t used for cellular respiration