Proteins perform many essential functions in cells including structural support, storage, transport, cell communication, movement, and defense against pathogens. They are made up of polymers of amino acids called polypeptides that fold into unique 3D shapes determined by their amino acid sequence. This structure enables their diverse functions, such as hemoglobin transporting oxygen in red blood cells and antibodies fighting bacteria. Changes to a protein's primary structure, such as the amino acid substitution in sickle-cell hemoglobin, can impact its structure, function, and cause disease.
2. Essential Knowledge
• Essential knowledge 4.B.1: Interactions
between molecules affect their structure
and function.
• a. Change in the structure of a molecular
system may result in a change of the function
of the system.
• b. The shape of enzymes, active sites, and
interaction with specific molecules are
essential for basic functioning of the enzyme.
3. • Structural support, storage, transport,
cellular
communications, movement, and defense
against foreigners
• Make up more than 50% of dry mass of cells
Protein Functions!
6. Example: Lactase, an Enzyme
• Enzyme that helps break down sugar lactose into
galactose and glucose. Speeds up reactions rates:
• Lactose intolerant: Mutation of Chrom. 2.
• Cramps, bloating, flatulence
7. • Hormonal protein: regulates sugar in
blood (tells cells to take it in), pancreas
Example: Insulin
11. Protein Structure and Function
• Consists of 1/more polypeptides
twisted, folded, and coiled into a
unique shape (determined by amino
acid sequence)
12. Four Levels of
Protein Structure
• Primary,
Secondary,
Tertiary,
Quartenary!
• Watch
Videos!
13. Hollow
cylinder
Cap
Chaperonin
(fully assembled)
Polypeptide
Steps of Chaperonin
Action:
1 An unfolded poly-
peptide enters the
cylinder from one end.
2 The cap attaches, causing the
cylinder to change shape in
such a way that it creates a
hydrophilic environment for
the folding of the polypeptide.
3 The cap comes
off, and the properly
folded protein is
released.
Correctly
folded
protein
•Chaperonins are protein molecules that
assist the proper folding of other proteins
14. Sickle-Cell Disease: A Change in
Primary Structure
• A change in primary structure can affect
a
Proteins structure and function
• Ex: Sickle-cell disease: results from a
single
amino acid substitution in protein
hemoglobin
17. Fig. 5-22c
Normal red
blood cells are
full of individual
hemoglobin
molecules, each
carrying oxygen.
Fibers of abnormal
hemoglobin
deform red blood
cell into sickle
shape.
10 µm 10 µm
18. Messing Up Proteins?
• Alterations in pH, salt concentration,
temp.,
or other environmental factors can cause a
protein to unravel denaturation
inactive protein
19. • Acts as a catalyst to speed up
chemical
reactions
• Can perform functions repeatedly
workhorses!
Enzyme Proteins!
20.
21.
22.
23. Cofactor
s
• A non-protein chemical compound
required for enzyme activity Ex: Fe
• “Helper Molecules" that assist
Biochemical transformations.
24. Coenzym
es
• A protein chemical compound required for
enzyme activity
• “Helper Molecules" that assist Biochemical
transformations.
25. Cofactors and
Coenzymes
• Work together to regulate enzyme function.
• Usually the interaction relates to a structural
change that alters the activity rate of the
enzyme
28. Allosteric Competition
• Binding of
inhibitor to
another
(allosteric) site of
enzyme (rather
than active site)
prevents binding
of substrate
29. Model Interpretations
The change in function of an enzyme can be
interpreted from data regarding the
concentrations of product or substrate as a
function of time. These representations
demonstrate the relationship between an
enzymes activity, the disappearance
• of substrate, and/ or presence of a
competitive inhibitor.
