When O2 binds to a heme group, the two bonds of Fe2+ that are not planar with the heme are occupied by:

One O 2 molecule and one His amino acid atom.

When O 2 binds to a heme group, the two bonds of Fe 2+ that are not planar with the heme are occupied by:

So this practice problem says when oxygen binds to a heme group, the 2 bonds of the iron 2 plus that are not planar with the heme are occupied by which one of these 4 potential answer options below. And of course, after reading through each of these options, there's a few that we can eliminate right off the bat such as option d here, which says that the iron 2 plus binds to 2 oxygen molecules. And, of course, we know that's not true. It only binds to 1 oxygen, not 2, and that's why we can cross off option d. And we can also eliminate option c here because it says that the iron the iron 2 plus will bind to 1 oxygen molecule and a nitrogen atom of the heme. However, recall that we are looking for a bond that is not planar with the heme. And so it's true that iron 2 plus does bind to nitrogen atoms of the heme but those bonds are planar with the heme of course and so, we're looking for bonds that are not planar with the heme and that's why we can eliminate c. So now we're between option a and option b, which both say that iron 2+ will bind to 1 oxygen molecule, but the difference is, that the other bond is going to be to 1 serine amino acid atom, versus 1 histidine amino acid atom. And, of course, recall from our previous lesson video that it does not bind to serine, instead it binds to histidine. And so if we scroll up to the image from our previous lesson video we can clearly see that the 2 bonds that are not planar with the heme are gonna be these vertical bonds going this bond here and this bond here going down. So the vertical one's going up and the vertical one going down and notice the vertical one going up is bonded directly to an oxygen molecule, just as being stated here and then the one going down is binding to a histidine amino acid atom. And so it's true that option B here is the correct answer for this problem and that concludes this practice. So, I'll see you guys in our next video.

When O 2 binds to a heme group, the two bonds of Fe 2+ that are not planar with the heme are occupied by:

One O 2 molecule and one His amino acid atom.

One O 2 molecule and one Ser amino acid atom.

One O 2 molecule and a nitrogen atom of the heme.

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1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

8. Protein Function

Heme Prosthetic Group

Biochemistry

8. Protein Function

Heme Prosthetic Group

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Multiple Choice

When O₂ binds to a heme group, the two bonds of Fe²⁺ that are not planar with the heme are occupied by:

One O₂ molecule and one Ser amino acid atom.

One O₂ molecule and one His amino acid atom.

One O₂ molecule and a nitrogen atom of the heme.

Two O₂ molecules.

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Verified step by step guidance

Understand the structure of the heme group: The heme group consists of a porphyrin ring with an iron (Fe2+) atom at its center. The iron atom can form six coordination bonds.

Identify the planar bonds: Four of these bonds are planar and are formed with the nitrogen atoms of the porphyrin ring.

Determine the non-planar bonds: The remaining two bonds are perpendicular to the plane of the heme. These are the axial positions.

Recognize the role of oxygen: One of these axial positions is typically occupied by an oxygen (O2) molecule when the heme is in its oxygenated form.

Identify the amino acid interaction: The other axial position is usually occupied by a histidine (His) residue from the protein structure, specifically the proximal histidine, which helps stabilize the iron-oxygen complex.