Chapter 5: Proteins

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Chapter 5: Proteins
Study Questions
Name
Date
Per.
1) Draw the general chemical structure of an amino acid and label its parts.
2) What is the NAME of the covalent bond that links 2 amino acids together?
Peptide
3) How many amino acids are there?
20
4) Complete the following table of protein functions:
Type of protein
Structural
Function
Support
Storage of amino acids
Storage
Examples
-Collagen & elastin -> connective tissues
(tendons, ligaments)
-Keratin -> hair, horns, feathers, skin
appendages
-Silk fibers -> insects & spiders (cocoons &
webs)
-ovalbumin -> in egg white (a.a. source for
embryo)
-casein -> prot. Of milk (a.a source for baby
mammals)
-plants have storage prot. in seeds
-Hb -> xport O2 from lungs
-xport across cell membranes
Transport
Transport of other substances
Hormonal
Coordination of an org’s activities
-Insulin -> reg. [ ] of sugar in blood of
vert’s.
Receptor
Response of cell to chem’l stimuli
Contractile
Movement
Defensive
Protect against disease
-recept. Built into membrane of a nerve cell
detect chem’l signals released by other nerve
cells
-actin & myosin -> movement of muscles
-Undulation of cilia & flagella (propel cells)
-AB combat bacteria & viruses
Enzymatic
Selective acceleration of chem’l
rxn’s
-Digestive enzymes hydrolyze the polymers in
food
5) Why is a protein’s shape of conformation so important?
It’s shape & conformation determines how it will work. The fxn. Of a protein depends on it’s ability
to recognize & bind to some other molecule; lock & key
6) Summarize and distinguish between the four levels of protein structure:
a) Primary structure: sequence of amino acids (in a linear structure)
b) Secondary structure: coils & folds of 1 degree structure that results from H-bonds along
the backbone of the polypeptide
c) Tertiary structure: irregular contortions that results from bonds (ionic, H, covalent) between
R-groups (side chains); some finished here
d) Quaternary structure: overall protein structure that results from the assembly of all
polypeptide subunits
7) In Fig. 5.17, amino acids are grouped by their side chains or R groups. What are the consequences of being
in these different groups? Some a. acids are polar & these a. acids will be attracted to each other;
non-polar will be attracted to non-polar but repelled by polar; - & + electrically charge will be
attracted but - & - or + & + (leads to specific 3-D shape)
8) Draw the structure of a generalized dipeptide, showing the peptide linkage with an arrow.
9) List four types of chemical/molecular interactions that contribute to the reinforcement of the tertiary
structure of a protein.
1) Hydrophobic (non-polar R groups group together)
2) Van Der Waals- (Once non-polar R group close together; V.D.W. help hold)
3) H
> Polar R groups
4) Ionic
5) disulfide bridges-> Reinforced by covalent bond; 2-SH groups brought together
10) What are chaperonins and what is their function?
Prof. Folding helpers
11) What technique is used to determine a protein’s 3-D structure?
X-ray crystallography (Wikipedia definition: method of determining the arrangement of atoms within a crystal, in which a
beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and
intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons
within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their
chemical bonds.)
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