Energy is the ability to do work all living things need energy to function and it comes from food or sunlight

The types of energy are kinetic energy, which is associated with the organized motion of objects; thermal energy, which is associated with the random motion of molecules; light energy, which is produced when atoms heat up and travel in waves; potential energy, which matter has due to its location or structure; and chemical energy, which is potential energy available in a chemical reaction.

Thermodynamics is the study of the flow and transformation of energy in the universe. The laws of thermodynamics include the conservation of energy, which states that energy cannot be created or destroyed, only changed, and that energy cannot be converted without some loss to the environment, also known as entropy.

Metabolism refers to all the chemical reactions in a cell, while a metabolic pathway is a series of chemical reactions providing reactants for the next set of reactions. The types of metabolic pathways include:

• Catabolic pathways: These involve the release of energy when polymers are broken down into smaller molecules. For example, during digestion, food is broken down through hydrolysis into monomers, which are then utilized by the body. Another example is cellular respiration, which involves the breakdown of glucose into carbon dioxide and water, releasing usable energy.

• Anabolic pathways: These pathways use energy to build larger molecules from smaller ones. Photosynthesis is a primary example, as it utilizes energy from sunlight to convert carbon dioxide and water into glucose and oxygen through dehydration synthesis.

ATP (adenosine triphosphate) is made when water splits apart and H+ ions (protons) build up. An organic phosphate molecule is added to ADP to form ATP. ATP synthase (an enzyme) in the mitochondria is crucial during both photosynthesis and cellular respiration for energy production.

Cellular Respiration

Cellular respiration is the process by which cells break down glucose (a monosaccharide with the formula C6H12O6) in the presence of oxygen to produce energy. The overall chemical reaction is:

[ \text{C}6\text{H}{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy (ATP)} ]

This process occurs in several stages:

1. Glycolysis: This occurs in the cytoplasm, where one molecule of glucose is broken down into two molecules of pyruvate, producing a net gain of 2 ATP and 2 NADH molecules.

2. Krebs Cycle (Citric Acid Cycle): This takes place in the mitochondria and processes pyruvate into carbon dioxide, while producing high-energy carriers, such as NADH and FADH2, and a small amount of ATP.

3. Electron Transport Chain: Also located in the mitochondria, this stage uses NADH and FADH2 produced in previous stages to create a large amount of ATP (approximately 32-34 ATP). This occurs as electrons are transported along the inner mitochondrial membrane, ultimately producing water when oxygen accepts the electrons.

The efficiency of cellular respiration means that one molecule of glucose can produce up to 38 molecules of ATP under optimal conditions.

Photosynthesis

Photosynthesis uses light energy, carbon dioxide, and water to create glucose and oxygen. The chemical reaction occurs in the chloroplasts: [ 6\text{CO}_2 + 6\text{H}2\text{O} + \text{light energy} \rightarrow C_6H{12}O_6 + 6\text{O}_2 ]

Light Dependent Reactions

Step 1: Sunlight strikes the plants' chlorophyll molecules, initiating the electron transport chain, resulting in the production of NADPH. Water molecules split, generating oxygen as a byproduct. ATP is created through ATP synthesis during this process. The results of the light-dependent reactions include:

• 2 oxygen molecules

• 1 ATP

• 1 NADPH

Calvin Cycle

Part B occurs in the stroma and does not require light, utilizing the products from the light-dependent reactions to convert carbon dioxide into glucose through a series of enzymatic reactions.