gen bio - lecture 2: scientific process and chemistry

evolution

• core theme of biology

• UNITY and DIVERSITY of organisms

• living organisms are modified descendants of common ancestors

emergence

• the whole is MORE than just the sum of its parts

ex. in a bike, all pieces are put together in a particular way to function — a pedal is meaningless alone)

emergent properties

• new processes that only appear when things are put together in a certain way

levels of biological organization (hierarchy of 7 things)

1. organelles

2. cells (being alive emerges here)

3. tissues

4. organs + organ systems

5. organisms, populations, communities (evolution emerges here)

6. ecosystems

7. biosphere

method of inquiry

seeking natural explanations for natural phenomena

• limited to what is observable and measurable

• systematic (NOT HAPHAZARD) investigation of natural world

hypothesis

TESTABLE explanation for observations based on available data

prediction

what you expect to see when you test your hypothesis

theory

broad explanation with significant support

law

statement of what ALWAYS occurs under certain circumstances

scientific method (6 main steps)

1. observation

2. background

3. hypothesis THEN

4. prediction

5. experiments

6. evaluate

- unsuccessful? revise

- success? repeat + verify

CHON

carbon, hydrogen, oxygen, nitrogen

• make up 96% of living matter

• essential elements of life

atoms

• have 3 subatomic particles (protons, electrons, neutrons)

electrons

• negatively charged

• move rapidly from shell to shell

• determine how an atom interacts

• the further away an electron is from the nucleus = the MORE potential energy an electron possesses

why can we use excited electrons to do work?

doing work releases energy and so the electron goes back to a lower energy state where it is more stable and less reactive

electron shell

an electron’s potential energy

valence shell

• outermost shell where bonds between electrons form

• needs 8 electrons in it to be STABLE/non reactive

chemical bonds result from…

how atoms share electrons

energy

capacity to cause change

molecules

compounds with 2+ atoms

electronegativity + special note about oxygen

• affinity for gaining electrons / tendency of an atom to attract electrons

  • F + O = most; S, H, I, C = medium, rest = low increasing left to right

• oxygen = VERY electronegative = VERY reactive

the type of bond made is determined by…

the difference in electronegativity

covalent bonds

• STRONGEST BOND

• sharing of a pair of electrons by 2 atoms

• intra(within)molecular bond

nonpolar covalent

when atoms have the same electronegativity = share electrons equally

polar covalent

a less than 2 difference in electronegativity which causes an unequal share of electrons (creates partially positive and partially negative sides to molecules)

ionic bonds

• electron is taken by the atom that is MORE electronegative (anion = - ; cation = +)

• GREATER than 2 difference in electronegativity

• intra(within)molecular bond

van der waals forces

• develop because electrons are in constant motion and can result in attractions between molecules

• inter(between)molecular bond

  • ex. dipole-dipole interactions (between polar), london dispersion forces (between nonpolar)

hydrogen bonds

• REALLY STRONG dipole-dipole interaction

• stick polar covalent molecules together

• polarity allows water molecules to form attractions to each other

** hydrogen bonds are responsible for…

the emergent properties of water!

(since water is polar, 1 molecule of water forms hydrogen bonds with other water molecules)

emergent properties of water (there are 4)

1. cohesion and adhesion (water molecules stick to each other)

2. moderates temperature (water’s high specific heat means that it is hard to change water temperature; water’s high heat of vaporization means that it is hard to change its state)

3. expands upon freezing (ice floats; hydrogen bonds in ice are more ordered and create air pockets)

4. universal solvent (substances can be…

• hydrophillic: LOVE water (ions, salts, polar)

• hydrophobic: AFRAID of water (lipids, non-polar)