IB Biology Topic B1.2.5 Effect of Ph and Temperature on Protein Structure Revision Notes (SL/HL)

IB Biology Topic B1.2.5 Effect of Ph and Temperature on Protein Structure Revision Notes (SL/HL) | RevisionDojo

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Protein Shape Depends on Weak Bonds That Break Easily

A protein's three-dimensional shape is held together by bonds and interactions between amino acids in the chain.
1. These include hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.
2. Most of these are individually weak, but collectively they hold the protein in a precise conformation.
Because these bonds are weak, changes in temperature or pH can break them.
1. When enough bonds break, the protein loses its three-dimensional shape, which is called denaturation.
2. A denatured protein still has its primary structure, so the amino acid sequence stays intact.
3. Its higher-level folding is disrupted, so it can no longer perform its function.

Common Mistake

Denaturation is not the same as breaking peptide bonds.
Peptide bonds are covalent and require hydrolysis to break.
Denaturation only disrupts the weaker bonds that maintain the 3D shape, such as hydrogen bonds, ionic bonds, and hydrophobic interactions.
The amino acid chain itself remains intact.

Temperature: Too Much Kinetic Energy Disrupts Folding

As temperature increases, molecules gain kinetic energy and vibrate more.
1. For enzymes, this initially increases reaction rate because substrate and enzyme molecules collide more often and with greater energy.
2. Beyond a certain point, the vibrations become strong enough to break the hydrogen bonds and other weak interactions holding the shape together.
Once enough bonds break, the protein unfolds and loses its functional conformation.
1. For most human proteins this happens above about 40°C.

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Protein Shape Depends on Weak Bonds That Break Easily

A protein's three-dimensional shape is held together by bonds and interactions between amino acids in the chain.
1. These include hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.
2. Most of these are individually weak, but collectively they hold the protein in a precise conformation.
Because these bonds are weak, changes in temperature or pH can break them.
1. When enough bonds break, the protein loses its three-dimensional shape, which is called denaturation.
2. A denatured protein still has its primary structure, so the amino acid sequence stays intact.
3. Its higher-level folding is disrupted, so it can no longer perform its function.

Common Mistake

Denaturation is not the same as breaking peptide bonds.
Peptide bonds are covalent and require hydrolysis to break.
Denaturation only disrupts the weaker bonds that maintain the 3D shape, such as hydrogen bonds, ionic bonds, and hydrophobic interactions.
The amino acid chain itself remains intact.

Temperature: Too Much Kinetic Energy Disrupts Folding

As temperature increases, molecules gain kinetic energy and vibrate more.
1. For enzymes, this initially increases reaction rate because substrate and enzyme molecules collide more often and with greater energy.
2. Beyond a certain point, the vibrations become strong enough to break the hydrogen bonds and other weak interactions holding the shape together.
Once enough bonds break, the protein unfolds and loses its functional conformation.
1. For most human proteins this happens above about 40°C.

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic B1.2.5: Effect of Ph and Temperature on Protein Structure Notes

Protein Shape Depends on Weak Bonds That Break Easily

Temperature: Too Much Kinetic Energy Disrupts Folding

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Protein Shape Depends on Weak Bonds That Break Easily

Temperature: Too Much Kinetic Energy Disrupts Folding

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics