Problem 92 - Chemistry Matter and Change

Question

Write balanced equations for photosynthesis, cellular respiration, and the hydrolysis of lactose.

Step-by-Step Solution

Answer

Photosynthesis: \( 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \). Cellular respiration: \( \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{energy} \). Hydrolysis of lactose: \( \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{C}_6\text{H}_{12}\text{O}_6 \).

Step 1: Photosynthesis Equation

Photosynthesis is the process by which green plants and some organisms use sunlight to synthesize foods with the help of chlorophyll pigments, primarily in leaves. The general balanced equation for photosynthesis is: \[ 6 ext{CO}_2 + 6 ext{H}_2 ext{O} + ext{light energy} \rightarrow ext{C}_6 ext{H}_{12} ext{O}_6 + 6 ext{O}_2 \] This equation represents the conversion of carbon dioxide and water, using light energy, into glucose and oxygen.

Step 2: Cellular Respiration Equation

Cellular respiration is the process that releases energy from glucose and other food molecules in the presence of oxygen. The overall balanced equation for cellular respiration is the reverse of photosynthesis and is given by:\[ ext{C}_6 ext{H}_{12} ext{O}_6 + 6 ext{O}_2 \rightarrow 6 ext{CO}_2 + 6 ext{H}_2 ext{O} + ext{energy} \] Here, glucose and oxygen are converted into carbon dioxide, water, and energy (in the form of ATP).

Step 3: Hydrolysis of Lactose

The hydrolysis of lactose is a chemical reaction where lactose is broken down into its component monosaccharides, glucose and galactose, with the help of the enzyme lactase. The balanced equation for this reaction is:\[ ext{C}_{12} ext{H}_{22} ext{O}_{11} + ext{H}_2 ext{O} \rightarrow ext{C}_6 ext{H}_{12} ext{O}_6 + ext{C}_6 ext{H}_{12} ext{O}_6 \] Lactose (a disaccharide) and water are the reactants, and glucose and galactose (both monosaccharides) are the products.

Key Concepts

Photosynthesis

Photosynthesis is an essential process in our ecosystem that allows plants, algae, and some bacteria to convert light energy, usually from the sun, into chemical energy in the form of glucose. This process takes place primarily in the chloroplasts found within the cells of leaves, using chlorophyll to capture light. The overall balanced chemical equation for photosynthesis is:\[ 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \]**Key Points:**

• Carbon dioxide (CO₂) is absorbed from the air.
• Water (H₂O) is taken up from the soil.
• Light energy helps convert CO₂ and H₂O into glucose (C₆H₁₂O₆), a sugar that serves as food for the plant.
• Oxygen (O₂) is released as a byproduct and contributes to breathable air.

Photosynthesis is not only vital for the plants themselves but also for all life on Earth, providing oxygen and forming the base of the food chain.

Cellular Respiration

Cellular respiration is a fascinating process that occurs in the cells of living organisms. It takes glucose and oxygen, turning them into energy, which is stored as ATP (adenosine triphosphate), alongside carbon dioxide and water as byproducts. This process occurs mainly in mitochondria, the powerhouses of cells. The chemical equation for cellular respiration is essentially the opposite of photosynthesis:\[ \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{energy} \ (\text{ATP}) \]**Important Aspects:**

• Glucose (C₆H₁₂O₆) from food is the primary fuel.
• Oxygen (O₂) is needed for aerobic respiration to occur effectively.
• The process releases energy by breaking the bonds in glucose.
• Carbon dioxide (CO₂) and water (H₂O) are expelled as waste products.

Cellular respiration allows organisms to harness the energy necessary for various functions, including growth, repair, and maintaining homeostasis.

Hydrolysis of Lactose

Hydrolysis of lactose is a chemical reaction vital for digesting milk sugars in organisms that consume lactose. This reaction is facilitated by the enzyme lactase, which breaks down lactose into two simpler sugars: glucose and galactose. The balanced chemical equation is:\[ \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{C}_6\text{H}_{12}\text{O}_6 \]**Key Details:**

• Lactose (C₁₂H₂₂O₁₁) is a disaccharide found in milk.
• The addition of water (H₂O) breaks the bond between glucose and galactose.
• Glucose and galactose are monosaccharides, or simple sugars, that can be easily absorbed into the bloodstream.

The hydrolysis of lactose is crucial for mammals to utilize milk as a source of energy and nutrition. Without sufficient lactase, individuals may become lactose intolerant, leading to digestive discomfort.