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Intro to Cellular & Molecular Biology 
Class 1: ​Cellular Chemistry + Macromolecules of Cells 

​WEEK 1  

 

● Introduction 
○ The organic molecules to the ​right​ have
nonpolar covalent bonds that are
hydrophobic by nature-- the water
molecules push them together in order
to minimize their disruptive effects
...

■ The organic molecules squeeze together to allow the water to have
the highest entropy
...

● Close together, they may experience Van der Waals
interactions
...
This holds the atom together! (Opposite
charges attract)
● Functional groups​ and Organic Chemistry-- ​“Be able to recognize and draw 
them!​”
○ In the organic molecule above
in the picture, if you were to
add a carboxyl group to the
carbon, it becomes
hydrophilic
...

■ Similarly, if you added a
hydroxyl group
(alcohol), the high electronegativity of water causes the hydrogen it
is attached to to become partially positive
...

○ What is pH?
■ A measurement of how many protons (H+) or hydroxide ions are in
a solution
...
NH3+ is positively charged
(an extra H+) and NH2 is neutral
...

■ They contain a polar head (a negatively charged phosphate group
shown on the bottom in the picture to the ​left​)
■ And two nonpolar hydrocarbon tails! No nitrogen, no oxygen, no
charge!
■ Remember to ​“be able to draw a phospholipid symbol!”
○ The cell membrane is a ​lipid bilayer
...
In order to increase the entropy of water, the formation
of the lipid
bilayer is most
economical in
terms of
energy
...

Why?
● The hydrophobic interior is just peachy about accepting
other nonpolar molecules! BUT… it is quite hard for polar
molecules and ions to get into the club
...
Why? There are
hydroxyl groups attached to glucose, but in large
concentrations it may slip in
...

○ What is a covalent bond?
○ What makes phospholipids form a bilayer?
○ Functional groups
○ Why is carbon the central molecule for life?
○ Good question: How will high temperature affect the interactions of the
bilayer?
■ Increasing temperature = increasing vibrations in the cell
...


● Proteins-- extremely important! 
○ Proteins fall into 5 categories:
■ Enzymes-- we love ‘em
■ Structural proteins
■ Motility proteins
■ Regulatory proteins
■ Transport proteins
○ Drawing an amino acid:
■ Draw the amino on the left side*
■ All amino acids are the L form-- meaning that the amino is on the
left side
...


■ An amino acid is NOTHING without its R group-- a specific
extension that makes amino acids different
...

However, the amino acids are overall neutral and
hydrophilic
...

○ Peptide bonds are bonds between amino acids
through ​condensation​… the removal of water!
○ Proteins are referred to based on the N-terminal
and the C-terminal… shown in the ​diagram
...
They
are ​only​ hydrogen bonds
...

● The beta sheet ​is a sheet with peaks and troughs
...

○ Both beta sheets and alpha-helix structures are kept
stable by the hydrogen bonds between their jutting
out oxygen and hydrogen molecules
...

● There can also be an UNSTRUCTURED part of the protein-it allows the protein to change shape! So there are
alpha-helices, beta sheets, and these guys
...

■ Tertiary structure: How alpha-helix and beta sheet pieces fold to
create a protein
...

■ Quaternary structure: When the structure above combines with 3
other polypeptides to form a functional protein
...

○ Basically non-covalent bonds rule the entire universe
and the answer to every single question is
“non-covalent bonds
...
The MORE non-covalent
bonds, the MORE stable the structure is

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