This week in AP Bio we started chapter 2 which is on chemistry. Most of it was review and we talked about energy, atoms, bonds, and water polarity. This connects with Big Idea 2.B, which states “Growth, reproduction and dynamic homeostasis require that cell create and maintain internal environments that are different from their external environments.”
Lecture: Bio- Chemistry
Energy and Atoms
- Atoms: the smallest fundamental unit of matter.
- 120 different kinds of atoms (“elements”)
- Biology is made up of 4 major, 10 minor.
- Energy interacts with atoms in different ways.
- Holds e-‘s to nucleus
- When atoms absorb energy, e-‘s move to higher energy levels
- The movement of e-‘s back to lower energy levels releases energy.
Atoms Bond
- Bonding is accomplished by electrons interacting between atoms due to valence considerations. Two major kinds of bonds hold atoms together.
- Ionic bond
- Transfer of e-‘s
- Not many combinations.
- Example is salt, or, NaCl.
- Covalent bond
- Sharing of e-‘s
- Infinite combinations
- All important biological molecules are covalently bonded.
- Example is glucose and DNA
- Ionic bond
- Not all Bonds are created equal.
- Polarity: the unequal sharing of electrons in a covalent bond leads to unequal distribution of charge in molecule. Polar molecules are attracted to other polar molecules.
- Hydrogen Bonds: The strongest attraction between most polar molecules. Common in biological systems.
- Bonds determine shape.
- Shape is important.
- Structure and function closely related.
- All chemical reactions result in breaking and forming bonds. In any reaction, mass, energy, and charge are conserved.
- 2H2 O2 = H20
Compounds and Emergence
- The properties of a compound can be very different from properties of elements that make them.
- Emergence: Increasing levels of complexity in a system can demonstrate novel properties not seen in the levels below them.
- Example: Salt
Radioactivity
- Atoms with unstable nuclei are “radioactive.”
- Emit high energy particles until stability is reached.
Big Questions
- Why is water such a big deal?
- In our bodies, we are water
- Earth has water
- Unique properties such as polarity and hydrogen bonds.
- Cohesion: sticking together
- Adhesion: Sticking to other things
- Water is both cohesive and adhesive, which gives water high surface tension.
A High Specific Heat
- Specific heat: How much heat is absorbed/ released before an increase/ decrease in temperature.
- There is no universal solvent but water comes close.
Reflection/ Questions
- How does the cohesion and adhesion of water help us?
- Are there other solvents that are as good/universal as water?
Helpful Links
https://www.khanacademy.org/science/biology/chemistry–of-life
AP Biology 