Explain how a molecule\'s size, polarity, and ability to form a hydrogen bond wi

Question

Explain how a molecule's size, polarity, and ability to form a hydrogen bond with water affect its movement across lipid bilayers. . Explain the mechanisms that give rise to turgor in plant cells. Describe the effects of very dilute and very concentrated solutions on animal cells. Explain the operation of channel versus carrier proteins, including the effect of solute concentration on their performance. 5 of 8 . Active transport requires the use of energy to move substances across a membrane against a concentration gradient via specialized proteins Primary active transport uses energy from the hydrolysis of ATP to move ions into or n gradients.

Explanation / Answer

1. Mechanism that give rise to turgor in plant cells. Describe the effects of very dilute and very concentrated solutions on animals cell.

The movement of water through semi permeable membrane from region of high concentration of water to low concentration of water is called Osmosis. Presence of solute effecting the concentration of medium generates the condition for movement of water across the membrane. The rgion with pure water has higher water potential. The region with more solute has lesser water potential. Water molecules have a tendency of moving from a region of higher water potential to lower water potential.

If an animal cell is placed in concentrated solution i.e hypertonic solution that means concentration of water outside the cell is lesser than concentration of solution inside the cell. This causes movement of water from cell to outside leading to shrinking of the cell.

If an animal cell is placed in Very dilute i.e hypotonic solution that means concentration of water inside the cell is lesser than concentration of solution outside the cell. This causes movement of water into the cell leading to swelling of the cell.

2. Channel Vs Proteins including effect of solute concentration on their performance.

Channel and carrier proteins both provide transport pathways to cross the lipid bilayer membrane. Channels always provide a passive way of transportation whereas carrier proteins can allow active as well as passive transport.

In presence of solute , channel protein show weak interaction with solute molecules to allow its passage whereas Carrier proteins undergo conformation changes to allow transport of molecules.

Also Channel proteins cannot transport molecules against concentration gradient whereas carrier proteins can utilize energy to transport against concentration gradient of solute.

3. Size of molecule, Polarity and ability to form hydrogen bonds and ability to pass through lipid bilayer:

Small size molecules can easily pass through the lipid bilayer.Larger and charged mocleule pass slowly through the membrance.Non polar (hydrophobic ) moelcules pass easily through lipid membrane whereas non polar molecles cannot.Ability to form hydrogen bonds increases ability of the molecule to pass the membrane lipid bilayer. Hydrogen bonds are weak bonds.

4. Active transport requires energy to transport molecules agaianst concentration gradient via special proteins

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