Chapter 2: Chemical Context of Life Flashcards
(28 cards)
What is an atom?
smallest unit of matter that retains the properties of an element
13 most common elements in the human body
O, C , H, N, Ca, Phosphorus(P), Potassium(K), S, Na, Cl, Mg, I, Fe
When do ionic bonds form?
When a cation(+ve) and anion(-ve) are attracted to each other
How do ionic compounds behave in the absence of water vs in the presence of water ?
- Ionic compounds in the absence of water: crystallization
- Ionic compounds in water: ionization
Why are ionic bonds weak bonds in living organisms(covalent are the strongest)?
Cells are surrounded by fluids (ionic bonds break to form ions)
When do polar covalent bonds occur(eg. H2O)?
When the atoms in the bond have varying electronegativities (as atoms have varying levels of attraction towards the shared e-) (non-polar(eg. methane) bond)-> equal electronegativities)
What is a hydrogen bond?
Electrostatic attraction between hydrogen and an electronegative atom(eg. O/N). Weak but additive.
What are Van der Waals interactions?
Weak interactions cause by partial positive/negative charges from random placements of e-(piling of e-)
relative strength of bonds/interactions (in this chapter)
covalent(strongest)>ionic>H bond>Van der Waals(weakest here)
What are some conditions associated with Van Der Waals interactions?
- Weak but additive(hence; geckos)
-Require atoms/molecules to be close together - happens between non-polar molecules
fun fact: initially found in real gases!
Examples of H bonds and Van der Waals attractions being “additive”
- H bonds hold DNA strand together(sugar-phosphate/ A-T/C-G base pairs)
- Van der Waals attractions help hold plasma membrane together
Differentiate between hydrogen bonds/polar molecules and Van Der Waals interactions
- H bonds(H is a polar atom, bond formed btw polar molecules): permanent dipoles
- Van der Waals interactions: caused by instantaneous dipoles(due to random e- placement)
Polar vs non-polar
polar= charged, non-polar= uncharged
What influences molecular shape?
no. of e- pairs surrounding a central atom in a molecule (VSPER theory)
Why is molecular shape important to the biological activity of molecules?
- determines how a molecule interacts with other molecules( e. proper orientation in A.E.)
- influences function(reactivity, solubility, polarity, etc.)->how a molecule participates in runs in a living organism
A molecule has to have atleast ____ (molecule vs compound)
1 covalent bond
Chemical equilibrium is reached when:
rate of forward rxn= rate of backward rxn
Covalent bonds hold atoms together because they
fill shells without giving atoms much charge, bring e- closer to protons
orbitals vs shells
a “shell” refers to a specific energy level surrounding the nucleus, while an “orbital” is a three-dimensional region within a shell where an electron is most likely to be found
A covalent bond is formed between _ (no. of) atoms?
2
What is the trend of electronegativity in the periodic table?
increases across a period and decreases down the group
What does the prefix iso mean?
equal/same
what does the suffix “lysis” mean?
to split apart(hydrolysis is the splitting of water)
In a double covalent bond, a carbon atom shares ..
electrons in two orbitals
