Enzymes and Water

Objectives

• Describe the effect of pH and temp on enzyme activity
• Explain a polar molecule
• Describe the significance of polar bonds
• ID water's structure and properties
• Explain why water is essential for life

Last week I mentioned that enzymes lower activation energy. How do they do that?

Untitled Slide

• Bring reactants together
• This happens at the active site
• Position reactants correctly
• Allow reactions to occur by different pathways

Some enzymes work best at certain pHs, like pepsin in your stomach.

Biochemical reactions work best at normal body temp. At higher temps, the shape deteriorates.

Objectives

• Describe the effect of pH and temp on enzyme activity
• Explain a polar molecule
• Describe the significance of polar bonds
• ID water's structure and properties
• Explain why water is essential for life

Dihydrogen monoxide

75% of Earth is covered in water

Water is transparent. This is good, because some things that live in it need light to make food.

The oxygen is more electronegative than hydrogren.

This means oxygen pulls harder on the electrons than the hydrogen does.

The electrons are still being shared, but the oxygen ends up with a slightly negative charge.

The hydrogens end up with a slightly positive charge.

This slight difference in electrical charge is called polarity. Water is a polar molecule.

Remember that opposite charges attract?

The slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of another.

This attraction results in bonds called hydrogen bonds.

Think about the surface tension lab. How would hydrogen bonding play a role?

Hydrogen bonds cause water to have a high boiling point.

Water expands when it freezes, so ice is less dense than water.

Thus ice floats on water. This is important for life. Why?

Water is involved in biochemical reactions like photosynthesis and cellular respiration.

Water is the main component of many solutions.

A solution is composed of two or more substances and has the same composition throughout it.

In pure water a fraction of molecules break down to form ions.