B) We also know from studies of protein structure that one turn of an a-helix includes 3.6 amino acid residues and extends the long axis of the helix by - 0.56 nm. Approximately how many amino acids must a helical transmembrane segment of an integral membrane protein have if the segment is to span the lipid bilayer defined by two stearate molecules laid end to end, plus the polar head groups to which the stearate molecules are attached (assume a polar head group has a diameter of 0.5 nm)?

Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
icon
Related questions
icon
Concept explainers
Question
**Transcription for Educational Website:**

---

### Protein Structure and Transmembrane Segments

**B)** We also know from studies of protein structure that one turn of an α-helix includes 3.6 amino acid residues and extends the long axis of the helix by ~0.56 nm. Approximately how many amino acids must a helical transmembrane segment of an integral membrane protein have if the segment is to span the lipid bilayer defined by two stearate molecules laid end to end, plus the polar head groups to which the stearate molecules are attached (assume a polar head group has a diameter of 0.5 nm)?

---

In order to understand and solve this problem, one needs to consider the structural parameters of α-helices and the overall dimensions of the lipid bilayer including the polar head groups.

### Steps to Solve
1. **Determine the length of the lipid bilayer**: 
   - Each stearate molecule, a type of fatty acid commonly found in lipid bilayers, spans a certain length. This length can be found by considering the fully extended form of a stearate molecule.
   - We must also add the diameter of the polar head groups at each end of the lipid bilayer. Given that each polar head group has a diameter of 0.5 nm, the added length from both ends will be 1.0 nm.
  
2. **Translate the span into α-helix turns**: 
   - Knowing that each turn of an α-helix extends the helix axis by 0.56 nm and involves 3.6 amino acid residues, calculate the total number of amino acids required to span the entire bilayer.

### Detailed Calculation
- **Define the length of the lipid bilayer**: 
  - Assume the length of each stearate molecule in its fully extended form is approximately known from literature. For simplification, let's assume each stearate molecule is about 2 nm in length.
  - Therefore, the total length of the bilayer including the head groups: \( 2 \text{ nm} (each stearate) + 2 \text{ nm} (each stearate) + 1.0 \text{ nm} (polar head groups) = 5.0 \text{ nm} \).

- **Calculate the number of amino acids**:
  - If each turn of the α-helix extends
Transcribed Image Text:**Transcription for Educational Website:** --- ### Protein Structure and Transmembrane Segments **B)** We also know from studies of protein structure that one turn of an α-helix includes 3.6 amino acid residues and extends the long axis of the helix by ~0.56 nm. Approximately how many amino acids must a helical transmembrane segment of an integral membrane protein have if the segment is to span the lipid bilayer defined by two stearate molecules laid end to end, plus the polar head groups to which the stearate molecules are attached (assume a polar head group has a diameter of 0.5 nm)? --- In order to understand and solve this problem, one needs to consider the structural parameters of α-helices and the overall dimensions of the lipid bilayer including the polar head groups. ### Steps to Solve 1. **Determine the length of the lipid bilayer**: - Each stearate molecule, a type of fatty acid commonly found in lipid bilayers, spans a certain length. This length can be found by considering the fully extended form of a stearate molecule. - We must also add the diameter of the polar head groups at each end of the lipid bilayer. Given that each polar head group has a diameter of 0.5 nm, the added length from both ends will be 1.0 nm. 2. **Translate the span into α-helix turns**: - Knowing that each turn of an α-helix extends the helix axis by 0.56 nm and involves 3.6 amino acid residues, calculate the total number of amino acids required to span the entire bilayer. ### Detailed Calculation - **Define the length of the lipid bilayer**: - Assume the length of each stearate molecule in its fully extended form is approximately known from literature. For simplification, let's assume each stearate molecule is about 2 nm in length. - Therefore, the total length of the bilayer including the head groups: \( 2 \text{ nm} (each stearate) + 2 \text{ nm} (each stearate) + 1.0 \text{ nm} (polar head groups) = 5.0 \text{ nm} \). - **Calculate the number of amino acids**: - If each turn of the α-helix extends
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps with 2 images

Blurred answer
Knowledge Booster
Cell structure
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biochemistry and related others by exploring similar questions and additional content below.
Similar questions
  • SEE MORE QUESTIONS
Recommended textbooks for you
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781319114671
Author:
Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:
W. H. Freeman
Lehninger Principles of Biochemistry
Lehninger Principles of Biochemistry
Biochemistry
ISBN:
9781464126116
Author:
David L. Nelson, Michael M. Cox
Publisher:
W. H. Freeman
Fundamentals of Biochemistry: Life at the Molecul…
Fundamentals of Biochemistry: Life at the Molecul…
Biochemistry
ISBN:
9781118918401
Author:
Donald Voet, Judith G. Voet, Charlotte W. Pratt
Publisher:
WILEY
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781305961135
Author:
Mary K. Campbell, Shawn O. Farrell, Owen M. McDougal
Publisher:
Cengage Learning
Biochemistry
Biochemistry
Biochemistry
ISBN:
9781305577206
Author:
Reginald H. Garrett, Charles M. Grisham
Publisher:
Cengage Learning
Fundamentals of General, Organic, and Biological …
Fundamentals of General, Organic, and Biological …
Biochemistry
ISBN:
9780134015187
Author:
John E. McMurry, David S. Ballantine, Carl A. Hoeger, Virginia E. Peterson
Publisher:
PEARSON