2. Proteins: Characteristics
Make up 10 to 30% of cell mass.
Basic structural material of the body.
Play vital roles in cell functioning.
All contain carbon, hydrogen, oxygen,
and nitrogen. Some contain sulfur or
phosphorus also.
All proteins are made up of building
blocks called amino acids.
4. Amino Acids
20 commonly occur in nature, 8 of these are
essential AA (can’t be synthesized by
human body, must be included in diet)
Two important functional groups—the amino
group (can act as a base and accept
protons) and the carboxyl group (can act as
an acid and donate protons).
All amino acids are identical except for the R
group—the R groups are what make each
amino acid different and chemically unique.
7. Protein Formation
Proteins are formed from amino acids
by dehydration synthesis.
The bonds between adjacent amino
acids are called peptide bonds.
Most proteins contain over 100 amino
acids and are truly macromolecules.
Some contain up to 10,000 amino
acids.
8. Organization of Proteins - 4
Structural Levels of Proteins
Primary structure– the linear sequence of
amino acids in the chain.
Secondary structure—formed by coiling of
the primary chain into an alpha helix (with
hydrogen bonds maintaining the coiled
structure) or a beta pleated sheet (hydrogen
bonds hold primary polypeptide chains side
by side in a pleated structure like an
accordion).
9.
10. Structural Levels of Proteins
Tertiary structure—achieved when an
alpha helix or beta pleated sheet folds
in a three dimensional way to produce
a globular molecule.
The structure is maintained by both
hydrogen and covalent bonds.
11.
12. Structural Levels
Quaternary structure—happens when
two or more polypeptide chains
aggregate in a regular manner to form
a complex protein.
The shape of a protein determines its
function. Anything that causes the
protein to unfold will result in the
protein being unable to perform its job.
15. Fibrous Proteins
Strand-like
Also called structural proteins.
Most exhibit secondary structure only but some
have quaternary structure as well (collagen is an
example of a protein with quaternary structure).
Insoluble in water
Very stable
Provide mechanical support and tensile strength.
Examples include collagen and keratin (both of
which are present in skin), and the muscle proteins
actin and myosin
16. Globular Proteins
Spherical and compact
Tertiary structure; some with quaternary
structure as well
Water soluble
Chemically active
Examples are enzymes and antibodies
Also called functional proteins
Susceptible to denaturing
17.
18. Protein Denaturation
The activity of functional proteins depends on their
three dimensional structure.
The hydrogen bonds responsible for maintaining the
structure are fragile and can be broken by changes
in both the physical and chemical environment.
Hydrogen bonds begin to break when the pH
changes or the temperature rises above normal.
The proteins unfold and lose their biological activity.
19. Enzymes
Enzymes are globular proteins that act
as biological catalysts.
Each enzyme is chemically specific.
Enzymes work by lowering the
activation energy of a reaction.
Enzymes act on substrates and trigger
chemical reactions in the body.
21. Nucleic Acids
Contain carbon, hydrogen, oxygen, nitrogen,
and phosphorus
Two types—DNA and RNA
DNA is the genetic material of the cell and is
found in the nucleus.
It replicates itself in order for cell division to
occur.
It provides instructions for protein synthesis.
There are 3 major types of RNA
(messenger, transfer and ribosomal). Each
has a different function.
22.
23. DNA
DNA is coiled like a spiral staircase or
ladder, known as a double helix
The 2 “backbones” are composed of
alternating sugar and phosphate groups
Each “rung” of the ladder is composed of 2
nitrogenous bases hooked together by
hydrogen bonds
Chromosomes are formed from DNA.
Genes are sections of chromosomes. Taken
together, all of the genetic material in a
cell’s nucleus is known as a genome
24. Nucleotides
The structural units of nucleic acids
Each nucleotide has three components
N-containing base
5-carbon sugar (a pentose)
Phosphate group
(Note: A nucleoside consists of just a base plus a
pentose sugar without the phosphate)
25. N-containing Bases
There are 5 different N-containing bases
found in nucleic acids. These are divided
into 2 types, purines and pyrimidines.
They follow these base-pairing rules:
Adenine pairs with thymine
Cytosine pairs with guanine
Uracil replaces thymine in RNA
Adenine and guanine are purines. They
each contain 2 rings.
Cytosine, uracil, and thymine are
pyrimidines. They each have a single ring
structure.
27. DNA
DNA replicates itself before cell division and
provides instructions for making all of the
proteins found in the body.
The structure of DNA is a double-stranded
polymer containing the nitrogenous bases A,
T, G, and C, and the sugar deoxyribose.
Bonding of the nitrogenous bases in DNA is
very specific; A bonds to T (via 2 hydrogen
bonds), and G bonds to C (via 3 hydrogen
bonds)
The bases that always bind together are
known as complementary bases.
28.
29. DNA polymerase III adds one nucleotide at a time to the 3’
end of the newly formed strand following base pairing rules
30. RNA
The major types of RNA are produced inside
the nucleus, and then transported into the
cytoplasm, where they are used to make
proteins according to the instructions
provided by the DNA.
The structure of most types of RNA is a
single-stranded polymer containing the
nitrogenous bases A (adenine), G (guanine),
C (cytosine), and U (uracil), and the sugar
ribose.
In RNA, G bonds with C, and A bonds with
U.
34. ATP
ATP is the energy currency used by the cell.
ATP is an adenine-containing RNA
nucleotide that has two additional phosphate
groups attached.
The additional phosphate groups are
connected by high energy bonds.
Breaking the high energy bonds releases
energy the cell can use to do work.