BIOLOGY 2B03 - Cell Biology Exam Review all what
you need to know new update (covered from
module 1- module 5) McMaster University
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Bio 2B03 Module 1 Lecture 1
Protein Functions:
- Structure: such as tubules, actins and microtubules
- Sensors: Initiate change inside of the cell by relaying information.
- Enzymes: can metabolize chemical reactions
- Regulation: Proteins can be activators or silencers for genes which allows gene expression to
be controlled. They can also modify the function of other proteins and turn them on or off.
- Signaling: Proteins act as signals as well as the receptors for communication between cells.
They are also the transduction pathways that interpret those signals.
Protein Structures:
1) Primary structure:
- The linear array of amino acids.
- There is an amino end (N-terminus)
and a carboxyl end (C-terminus).
- Between each amino acid residue is a
peptide bond holding it together into
a chain
- The peptide bond is between a C-
terminus and an N-terminus, it is a C-
N bond
Amino Acids:
- Each amino acid has a similar
structure around the central
Alpha carbon.
- They all consist of:
1) Hydrogen
2) Amino group (H3N+)
3) Carboxyl group
4) Variable R-group
- The variable group of each
individual amino acid will dictate
that amino acid’s properties BUT the
accumulated R groups will define the properties of the entire polypeptide.
Amino Acid Side Chains:
- The side chains of amino acids will dictate their characteristics and will change how the
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amino acid is classified.
- These side chains differ in:
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1) Size
2) Shape
3) Charge
4) Hydrophobicity
5) Reactivity
- **These properties allow amino acids to be classified based on their SOLUBILITY IN WATER
or the POLARITY OF THE SIDE CHAIN.
Solubility:
Definition- a molecule is soluble in water if it can form hydrogen bonds with water which is
thermodynamically favorable. A soluble molecule usually carries hydrophilic amino acids residues on its
exterior.
Hydrophobic molecules:
- Cannot form hydrogen
bonds or can form very
little, so they are either
insoluble in water or
only slightly soluble.
- Amino acids with long
and saturated
hydrocarbon chains in
their R group are usually
hydrophobic due to this
non-polar side group.
- HYDROPHOBIC amino
acids tend to be in the
interior of cytosolic
proteins and form a
hydrophobic core.
- A protein found in a hydrophobic environment (i.e membrane) has hydrophobic molecules
on the exterior of the protein thus making it hydrophobic and insoluble.
- Hydrophobic amino acids can be divided into Aromatic amino acids AND Aliphatic amino
acids (hydrocarbon chain).
- ***Tyr has an OH group and so it can be a part of both hydrophobic and hydrophilic since
the OH can hydrogen bond.
Hydrophilic molecules:
- Typically charge polarized and capable
of hydrogen bonding.
- Includes: molecules with an – OH at one end
(O-) & molecules with an – NH2 at one end
(NH3+)
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