Cellular Respiration: Process, Structure, and Energy Production

Cell membrane is a gatekeeper, allowing specific molecules to pass, excluding others, based on size and charge, crucial for cellular function.

### Cellular Respiration: From Glucose to ATP
* 🔬 The process of cellular respiration begins with glycolysis, which occurs in the cytoplasm and breaks down glucose into **two 3-carbon molecules of pyruvate**.
* ⚖ Glycolysis requires an initial investment of **2 ATP**, but ultimately produces a net gain of **2 ATP per glucose molecule**.
* 🔋 Pyruvate then enters the mitochondria for the Krebs cycle (citric acid cycle), where it is **further broken down to release more energy**.
* 🌬 The electron transport chain (ETC) in the inner mitochondrial membrane is where the majority of ATP is generated, using the energy from electrons carried by **NADH and FADH2**.
* This entire process is an example of a redox reaction, where **glucose is oxidized into carbon dioxide** and **oxygen is reduced into water**.
* 🌿 Cellular respiration is the process by which cells extract energy from glucose to produce **ATP, the energy currency of the cell**.
* 🏭 The relationship between cellular respiration and photosynthesis is complementary, with cellular respiration **breaking down glucose** and photosynthesis using light energy to **build glucose**.
* 🔗 Enzymes play a crucial role in catalyzing the various steps of cellular respiration, **lowering the activation energy** required for the reactions to occur.

### Cellular Respiration and Photosynthesis: A Detailed Overview
* 🔋 The process of cellular respiration begins with glycolysis, where glucose is broken down into pyruvate, producing **2 ATP and 2 NADH**.
* 🔄 Before entering the Krebs cycle, pyruvate is converted to acetyl CoA in a preparatory step, releasing **2 CO2 and 2 NADH**.
* 🌀 The Krebs cycle then completes the oxidation of glucose, producing **6 NADH, 2 FADH2, 2 ATP, and 4 CO2** per glucose molecule.
* 🔌 The electron transport chain, located in the inner mitochondrial membrane, uses **NADH and FADH2** to create a **proton gradient for ATP synthesis**.
* 🔬 In the absence of oxygen, fermentation occurs, converting pyruvate to **lactate or ethanol** to regenerate **NAD+ for glycolysis**.
* ☀ Photosynthesis begins with the light reactions in the thylakoid membranes, where photosystems I and II convert light energy into **ATP and NADPH**.
* 🌿 The Calvin cycle, occurring in the stroma, uses **ATP and NADPH** to fix CO2 into glucose, with the enzyme **rubisco** playing a **key role**.
* 🌈 Chlorophyll pigments absorb light energy, with chlorophyll a and b absorbing most wavelengths except green, which is reflected, giving plants their **green color**.

Biology 1408 Exam 2 Review

Natalie Russell

Preparing for the Electric Sam Exam: A Guide

It is important to review the study guide, watch the videos, and go through the extra materials for each lesson.

Lesson 5 covers the plasma membrane, which is mostly made of a phospholipid bilayer with polar heads pointing in and out of the cell, and hydrophobic tails preventing the passage of large and charged molecules.

Diffusion and osmosis are essential processes to understand for the exam, as diffusion involves solute molecules moving from high to low concentration without energy, while osmosis specifically deals with the movement of water molecules in response to the concentration of solute molecules, especially across the plasma membrane.

Understanding Osmosis and Cell Energetics

Osmosis is the movement of water to achieve solute balance, causing cells to shrink or swell depending on the tonicity of the solution.

Plant cells become turgid in hypotonic solutions, while animal cells undergo hemolysis, and both shrink in hypertonic solutions.

Cell energetics involve endocytosis, exocytosis, and active transport, which requires energy expenditure by the cell.

The law of conservation of energy states that energy cannot be created or destroyed, only transformed with a loss of usable energy and an increase in entropy.

Kinetic energy is the energy of motion, potential energy is stored in chemical bonds, and ATP serves as the energy currency of cells for cellular work.

ATP is the energy currency of the cell, essential for cellular work and function.

It is continuously regenerated from ADP through the process of cellular respiration, using the energy from the food we eat.

ATP is used for biosynthesis, detoxification, temperature regulation, ion transportation, and muscle contraction, among other cellular processes.

Enzymes are protein catalysts that lower the activation energy of chemical reactions and have specific substrates, often participating in metabolic pathways.

They can be inhibited by competitive or non-competitive inhibitors, affecting their activity.

Enzymes can also become denatured by extreme heat or pH levels, impacting their three-dimensional structure and function.

The Role of Temperature in Enzyme Function and the Process of Cellular Respiration

Enzymes function best at their optimum temperature and pH, with deviations leading to a loss of function.

The energy of activation is reduced by enzymes, allowing reactions to proceed with less input of energy.

Cellular respiration is a process that uses glucose and oxygen to produce ATP, with glucose being oxidized to carbon dioxide and oxygen being reduced to water.

Cellular respiration involves three main phases: glycolysis, the Krebs cycle, and the electron transport chain (ETC) or oxidative phosphorylation, all of which take place in the cytoplasm or mitochondria.

Glycolysis produces two ATP and two NADH molecules, serving as the starting point for the process.

The Krebs cycle, preceded by a preparatory step, generates six NADH, two FADH2, and two ATP, while fully breaking down the initial glucose molecules.

The Role of NADH and FADH2 in Cellular Respiration

Pyruvate is converted to acetyl CoA, producing CO2 and NADH, and this process occurs twice for each glucose molecule.

The Krebs cycle then produces NADH, FADH2, ATP (or GTP), and CO2, with the total yield being 6 NADH, 2 FADH2, and 4 CO2 for every glucose molecule.

NADH and FADH2, as electron carriers, play a crucial role in the electron transport chain, where they transfer electrons and contribute to the pumping of protons across the inner mitochondrial membrane, ultimately creating a gradient for ATP production.

Electrons are passed through the electron transport chain and accepted by oxygen to produce water.

The buildup of protons on one side of the membrane creates a gradient, which is used to generate ATP through ATP synthase.

In the absence of oxygen, glycolysis can lead to fermentation, producing lactic acid in muscle cells, while the overall process of cellular respiration yields approximately 36 ATP molecules per glucose molecule.

Photosynthesis is driven by sunlight and involves a redox reaction where carbon dioxide is reduced to glucose and water is oxidized to produce oxygen gas.

It is an endergonic reaction, requiring sunlight as an energy input.

The process takes place in the chloroplast, with light reactions occurring in the thylakoid membranes and the Calvin cycle occurring in the stroma.

The Role of NADPH and ATP in Photosynthesis

Photosystem I and II work together to produce NADPH, which provides the reducing power needed for the Calvin cycle to convert carbon dioxide into glucose.

The light reactions also generate ATP, through a process similar to cellular respiration, to further support the production of glucose.

Chlorophyll pigments absorb light energy, with chlorophyll a, chlorophyll b, and beta carotene each absorbing different wavelengths of light to drive the photosynthetic process.

Light Reactions, ATP Production, and the Calvin Cycle

The light reactions in photosynthesis result in the production of ATP and NADPH.

The Calvin cycle uses six molecules of CO2 to produce one molecule of glucose, with the help of ATP and NADPH.

The enzyme Rubisco plays a crucial role in carbon dioxide fixation, ultimately allowing every carbon in glucose to come from CO2.