4.4 The formation of alpha helices and beta sheets satisfies the hydrogen-bonding requirements of the protein backbone

folding

The hydrogen bonds formed by α helices and β sheets may not contribute much to the overall stability of a folded protein but, nevertheless, the formation of these hydrogen bonds is critical for protein _____

energetic

Water is generally excluded from the interior of the protein and if, upon folding, a compensating hydrogen bond is not formed, then there will be an _____ penalty against folding

unfold, degrade

Here's why achieving low energy is important:

1. Stability: Systems, including proteins, naturally tend toward a state of minimum energy because this is the most stable state. A folded protein is considered stable when it's in a low-energy state, meaning it is less likely to ______ or ______.

forces

Low energy important:

Thermodynamics: According to the laws of thermodynamics, a system at lower energy has fewer _____ driving change. For proteins, this means they are less likely to misfold or interact inappropriately with other molecules.

function

Low energy important:

Functionality: Proteins in their native, low-energy state are able to maintain their correct 3D shape, which is crucial for proper biological _____. If a protein is in a higher energy state, it may be unstable, leading to misfolding or aggregation, which can impair its function or even cause diseases (like Alzheimer's or Parkinson's).

energy

Low energy important

Energy Efficiency: Biological systems are energy-efficient. By maintaining proteins and other molecules in low-energy, stable states, cells don't need to spend extra ___ on constantly refolding or repairing structures, saving resources for other processes.

alpha helices, beta sheets

The construction of proteins from _______ ____ and _______ _____ ensures that essentially all hydrogen-bonding groups that are excluded from water are able to form hydrogen bonds with each other

interface

The backbone groups form hydrogen bonds in a regular pattern, thereby compensating for the loss of hydrogen bonds with water, which is excluded from the ____ between the two helices

hydrophobic

The sidechains that are located at the interface btwn alpha/beta secondary structures are ______