This document provides information about proteins including their structure, functions, and classification. It discusses that proteins are the most structurally and functionally diverse biomolecules, accounting for over 50% of dry cell mass. They are involved in many functions including metabolism, storage, support, transport, regulation, and motion. The document describes the building blocks of proteins as amino acids and explains the four levels of protein structure: primary, secondary, tertiary, and quaternary. It also lists some examples of structural and functional proteins.

1. Proteins
2006-2007
MC 2
Biochemistry
BSN 1

2. Proteins
 Most structurally & functionally diverse group of
biomolecules
 Proteins account for more than 50% of the dry
mass of most cells
 Function:
 involved in almost everything
 Metabolism
 Storage
 Support
 Transport
 Regulation
 Motion

3. Metabolism
 Enzymes
 Biological catalysts
– speed up chemical reactions
 Digestive enzymes that aid in hydrolysis
o Lipase
o Amylase
o Lactase
o Protease
 Molecular Biology
o Polymerase
o Ligase
 Industry
o Dairy, baby food, rubber, beer, photography,
contact lens cleaner

4. Storage

5. Support
 Structural proteins
 Keratin – hair and nails
 Collagen – supports ligaments, tendons, and skin
 Silk – cocoons and spider webs

6. Assignment (40 points) : WRITE DOWN
answers on a long coupon bond. Submit on
Nov 14, 12 noon @ A-205/ 206.
1. In a tabulated form, write down the structural
differences between an α–keratin and
collagen. (15 points)
2. Classify protein based on the source of this
molecule. Briefly describe each. (5 points)
3. Enumerate and briefly describe the
classification of proteins based on its
biological function. (20 points)

7. Transport
 Channel and carrier proteins in the cell membrane
 Allows substances to enter and exit the cell
 Transport molecules in blood
 Hemoglobin
– transports oxygen in the blood

8. Defense
 Antibodies
 Combat bacteria and viruses

9. Regulation
 Hormones
 Intercellular messengers that influence metabolism
 Insulin – regulates the amount of glucose in the
blood and in cells
 Human growth hormone – its presence determines
the height of an individual
 Receptor Proteins
 Built into the membranes of nerve cells
 Detect chemical signals (neurotransmitters)
released by other nerve cells

10. Motion
 Muscle contraction
 Actin and myosin – make up muscle fibers
 Motor proteins within the cell
 Allow cell components to move from place to place
 Flagella- move the cell
 Cilia- move contents around the cell

11. Proteins
• A protein is a biologically functional molecule that
consists of one or more polypeptides
• Amino acids are the building blocks (monomers)
of proteins
 Amino acids are organic molecules with carboxyl and
amino groups
 Amino acids differ in their properties due to differing side
chains, called R groups (see next slide)
• Polypeptides are unbranched polymers built from
the same set of 20 amino acids

12. Proteins
 Structure:
 monomer = amino acids
 20 different amino acids
 11 made by body
 9 essential amino acids (must get from food)
 polymer = polypeptide
 protein can be one or more polypeptide chains
folded & bonded together
 large & complex molecules
 complex 3-D shape
Rubisco
hemoglobin
growth
hormones

13. Amino acids
 Structure:
 central carbon (α carbon)
 amino group
 carboxyl group (acid)
 R group (side chain)
 variable group
 confers unique
chemical properties
of the amino acid
—N—
H
H
C—OH
||
O
R
|
—C—
|
H

14. Over a hundred amino acids but…

15. Nonpolar amino acids: Non-polar amino acids tend to
be found in the center of the molecule (stabilize the structure).
 nonpolar & hydrophobic

16. Polar amino acids: Polar amino acids tend to be located
on the protein surface (capable of interacting with water molecules)
 polar or charged & hydrophilic

17. Sulfur containing amino acids
 Form disulfide bridges
 cross links between sulfur in amino acids
You wondered
why perms
smelled like
rotten eggs?
H-S – S-H

18. Building proteins
 Peptide bonds
 linking NH2 of one amino acid to COOH of another
 C–N bond
 N terminus – C terminus
peptide
bond
dehydration synthesis

19. Protein structure & function
 Function depends on structure
 3-D structure
 twisted, folded, coiled into unique shape
hemoglobin
collagen
pepsin

20. Primary (1°) structure
 Order of amino acids in chain
 amino acid sequence determined by
gene (DNA)
 slight change in amino acid sequence
can affect protein’s structure & it’s
function
 even just one amino acid change can make
all the difference!
lysozyme: enzyme
in tears & mucus
that kills bacteria

21. Sickle cell anemia

22. Secondary (2°) structure
 “Local folding”
 folding along short
sections of polypeptide
 interaction between
adjacent amino acids
 H bonds between
backbones (O:H)
 -helix
 -pleated sheet
 Fibrous proteins – only
have secondary structure
 Keratin
 Silk

23. Secondary (2°) structure

24. Tertiary (3°) structure
 “Whole molecule folding”
 created when the secondary structure
fold and form bonds to stabilize the
structure into a unique shape
 determined by interactions
between R groups
 Hydrophobic interactions
 anchored by
disulfide bridges
 Ionic Bonds between R groups
 Hydrogen bonds between backbones
 Van derWaals Force (velcro)
 Globular (spherical) proteins – have
tertiary structure
 enzymes

25. Quaternary (4°) structure
 two or more tertiary folded peptide subunits bonded
together to make a functional protein
 Hemoglobin – 4 polypeptides
 Collagen – 3 polypeptides
hemoglobin
collagen =
skin & tendons

26. Protein structure (review)
1°
2°
3°
4°
aa sequence
peptide bonds
H bonds
R groups
hydrophobic interactions,
disulfide bridges, ionic bonds
determined
by DNA
multiple
polypeptides
hydrophobic
interactions

27. Denature a protein
 Unfolding a protein/changes the shape
 disrupt 3° structure
 pH  temperature
 unravels or denatures protein
 disrupts H bonds, ionic bonds &
disulfide bridges
 destroys functionality