Problem 76 - Chemistry The Central Science

Question

Which transition metal atom is present in each of the following biologically important molecules: (a) hemoglobin, (b) chlorophyls, (c) siderophores, (d) hemocyanine.

Step-by-Step Solution

Answer

The transition metal atoms present in the given biologically important molecules are: (a) Hemoglobin: iron (Fe), (b) Chlorophylls: magnesium (Mg), (c) Siderophores: iron (Fe) (by interaction), and (d) Hemocyanine: copper (Cu).

Step 1: Recognizing the metal in hemoglobin

Hemoglobin is a protein responsible for carrying oxygen in the blood of vertebrates. The metal present in hemoglobin is iron (Fe), which is a transition metal. It's part of a heme group within the protein structure.

Step 2: Identifying the metal in chlorophylls

Chlorophylls are the green pigments responsible for photosynthesis in plants and algae. The metal present in chlorophylls is magnesium (Mg). It is situated in the center of a porphyrin ring.

Step 3: Determining the metal in siderophores

Siderophores are small molecules that bind and transport iron (Fe) in microorganisms. Although siderophores do not directly contain a transition metal within their structure, they interact with iron (Fe) as a way to acquire this metal for the microorganisms.

Step 4: Finding the metal in hemocyanine

Hemocyanine is a copper (Cu)-containing protein that serves as an oxygen-carrier in the blood of various invertebrates, including mollusks and arthropods. The transition metal atom present in hemocyanine is copper (Cu). To summarize, the transition metal atoms present in each biologically important molecule are: - Hemoglobin: iron (Fe) - Chlorophylls: magnesium (Mg) - Siderophores: iron (Fe) (by interaction) - Hemocyanine: copper (Cu)

Key Concepts

Hemoglobin and Iron

Hemoglobin is an essential molecule found in the blood of vertebrates. Its primary function is to transport oxygen from the lungs to other parts of the body. This molecule contains an iron atom at its core. This iron atom plays a key role in its oxygen-carrying ability. Iron is a transition metal and is located inside a heme group, which is a part of hemoglobin's structure.

• Iron in hemoglobin binds with oxygen molecules.
• This bonding process allows red blood cells to deliver oxygen efficiently.

When oxygen is present, these iron atoms bind reversibly, which means they can easily pick up and release oxygen as needed. This process is crucial because it ensures that different tissues get the oxygen they need for survival and function.

Chlorophyll and Magnesium

Chlorophyll is the pigment responsible for the green color in plants and algae. It plays a vital role in photosynthesis, the process by which plants convert sunlight into energy. At the heart of each chlorophyll molecule is a magnesium ion. This ion is held in place by a large molecule called a porphyrin ring.

• Magnesium in chlorophyll captures light energy.
• This energy is then used to convert carbon dioxide and water into glucose.

The process of photosynthesis is essential for life on Earth as it provides essential oxygen and food for other living organisms. The magnesium center in chlorophyll is crucial because it helps stabilize the pigment and allows the absorption of light in the optimal spectrum for photosynthesis.

Siderophores and Iron

Siderophores are fascinating molecules found in microorganisms. They have a critical function: to capture and transport iron from the environment. These molecules do not contain a metal themselves but have a high affinity for iron (Fe). They are crucial in microbial iron acquisition because iron is a vital nutrient that many organisms require.

• Siderophores bind strongly to iron ions.
• They transport the iron back into the microorganism.

Once inside, the microorganisms can use iron for essential processes such as respiration and DNA synthesis. The ability of siderophores to sequestrate iron is especially important in environments where iron is scarce, giving microorganisms a competitive advantage.

Hemocyanin and Copper

Hemocyanin is an oxygen-transport protein found in the blood of many invertebrates, including arthropods and mollusks. Instead of iron, like in hemoglobin, the active site in hemocyanin contains copper atoms. These copper ions are responsible for binding oxygen.

• Copper in hemocyanin allows oxygen transport under different conditions.
• It gives the blood of these animals a blue color when oxygenated.

This feature is particularly useful in colder and low-oxygen environments where many of these invertebrates live. The presence of copper allows hemocyanin to bind oxygen efficiently at lower concentrations, ensuring adequate oxygen supply throughout the organism’s body.