BIO20A: Chemical Principles

Unit 1 covers general Chemical Principles such as Cell size & chemistry, Chemical Bonds, Properties of Water, and Acids/Bases/pH

Seeing cells from the Naked eye

~ 0.2mm or 200µm

Seeing cells with a Light Microscope

~0.2µm

Seeing cells with a Electrion Microscope

~0.2nm

What elements make up ~96% of body mass?

O (65%), C (18.5%), H (9.5%), and N (3.3%)

What % does water make up in the cell?

70% of the cell

The rest of the cell is made by what four macromolecules?

Proteins, Carbohydrates, Lipids, and Nucleic Acids

What % of the cell’s dry weight does protein make?

55% of the cell

What are the levels of cell chemistry in order from smallest to largest?

Elements, Small Molecules, Macromolecules, Complexes and Structures, Viruses, and Cells

Describe a Nonpolar Covalent bond

A strong bond where electrons are equally shared

Describe a Polar Covalent bond

A strong bond where electrons are unequally shared. The more electronegative atom has a partial charge.

Describe an Ionic bond

A bond strong when dry but weak in water where a very electronegative atom that takes an electrion, making oppositely charged ions attract one another (NaCl)

Describe a Hydrogen bond

A weak bond where a partial positive H is attracted to a partial negative N, O, or F

Describe hydrophonic interactions and Van der Waals

A weak bond where nonpolar molecules cluser away from water and brief attractions occur between close molecules

Why do weak bonds matter?

Since they can form and break easily molecules can bind briefly and let go

What are the properties of water?

• Cohesion: water molecules stick together

• High Heat Capacity: water absorbs or releases a lot of heat with little change in temperature, which stabilizies climates and bodies of water

• High Heat Vaporization: evaporation takes a lot of

• Ice being less dense than liquid water: ice flotes and insulates lakes so life survives below

• Universal solvent: Water surrounds ions and polar molecules. Hydrophilic substances favor water whereas Hydrophobic ones do not.

What is the reversible reaction between water molecules and Hydrogen + Hydroxide an example of?

dynamic equilibrium

What ions do acids have more of? bases?

Acids have more hydrogen ions. Bases have less hydrogen ions and more hydroxide ions.

1. What is the formula for pH?

2. What is the pH scale?

3. What pH is acidic?

4. What pH is basic?

1. pH = -log[H⁺]

2. It’s a scale of 0-14

3. below 7

4. above 7

What internal pH do cells have?

pH of ~7. Any changes would be harmful to the cell

What are buffers?

A weak acid with a matching base that either takes or release a [H⁺] ion. This helps stabilize the pH of cells