Know me slide 5 Flashcards
(Greek) Proteios
“first” or “primary”
Proteins account for more than half the dry mass of
most cells.
Proteins have critical and diverse roles throughout
the bodies of all organisms
A catalyst
is a substance that accelerates the rate of a chemical reaction without affecting the products of the reaction and without itself being altered or consumed by the reaction.
enzymes.
The catalysts in living
organisms are proteins called
enzymes.
Enzymes are typically very large molecules that
bring
together or break apart substrates (the molecules upon
which a chemical reaction occurs).
1 Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). 2 Substrates held in active site by weak interactions, such as hydrogen bonds, and ionic bonds. 3 Active site can lower the energy needed to start a reaction.
4 Substrates are converted to products 5 Products are released. 6 Active site is available for two new substrate molecules
Amino acids
are the
monomer building blocks of
proteins.
Polypeptides
are polymers
of amino acids
A protein consists
of one or
more polypeptides.
There are 20
different amino
acid monomers
from which
polypeptides are
assembled.
Amino Acid Monomers
Differ in their properties
due to differing side
chains, called R-groups
Amino acids are linked
by
peptide bonds
Peptide bonds are
formed
through
dehydration reactions
A protein’s specific
conformation
(or 3D
shape) determines its
function
4 Levels in Protein Structure
- Primary Structure
- Secondary Structure
- Tertiary Structure
- Quaternary Structure
Primary Structure
• The linked series of amino acids with a unique sequence
• The 20 amino acids can be assembled in 20^127 sequences
(for the polypeptide of 127 amino acids shown above).
• Primary structure dictates structure at higher levels
Secondary Structure
Hydrogen bonds between amino acids of a single
polypeptide (α helix) or amino acids of adjacent polypeptides
(β sheet) bring about secondary structure
Tertiary Structure
Results from interactions between the side chains (R-groups) of amino acids Involves a variety of bonds: disulfide bridges, hydrogen bonds, van der Waals interactions, ionic bonds
Quaternary Structure
• The overall structures of
proteins that are comprised
of more than one
polypeptide subunits
Hemoglobin is the ironcontaining
oxygen transport
protein in the blood of
mammals and other animals.
It consists of four polypeptide
chains, each of which has a
heme group
Anemia –
decreased
hemoglobin in blood, usually
from iron deficiency
Sickle-cell hemoglobin differs from normal hemoglobin in only
one amino acid.
Sickle hemoglobin molecules adhere when
they are deoxygenated, and can cause blood cells to lodge in
blood vessels.
Denaturation
occurs when a protein unravels and loses its
three dimensional conformation
The protein conformation that arises from a given primary
structure depends
on the physical and chemical conditions
of the protein’s environment.
Protein Functions
- Enzymes
- Structural proteins
- Storage proteins
- Transport proteins
- Hormones
- Receptor proteins
- Contractile and motor proteins
- Defensive proteins
Collagen
is the most abundant protein in animals and
provides the high tensile strength and resilience needed
in skin, tendons, and ligaments
The venoms of stingrays and other animals are proteins.
These
can act by breaking down tissues or acting on components of the
nervous system.
Nucleic acids
are the molecules in which
hereditary information is stored and transmitted.
Genes
are made of nucleic acids
Genes are the units of inheritance
Genes specify the amino acid sequences of
polypeptides
Genes are the units of inheritance
Genes specify the amino acid sequences of
polypeptides
There are two types of nucleic acids:
-Deoxyribonucleic Acid (DNA)
– Ribonucleic Acid (RNA)
Both are present in cells
DNA contains the genetic “blueprint” of an
organism
– RNA is involved in protein synthesis
Nucleic acids exist as
polymers called
polynucleotides
made
up of monomers called
nucleotides
nucleotides
Each polynucleotide
consists of monomers
called nucleotides
Each nucleotide is made
up of a
nucleoside (a
nitrogenous base and a
pentose sugar) and a
phosphate group
Nitrogenous Bases
3 pyrimidines – single 6- membered ring • 2 purines – one 6- membered ring + one 5- membered ring • Differ in functional groups • Are abbreviated C, T, U, A, and G • T is found only in DNA, U is found only in RNA
DNA nucleotides contain
a deoxyribose sugar
RNA nucleotides contain
a ribose sugar.
Deoxyribose is
identical to ribose
except
it is missing
an oxygen on the
second carbon
Carbons of the pentose sugars
are
numbered clockwise from the carbon
attached to the nitrogenous base.
The sugar carbons are labeled with a
prime (‘)
to distinguish them from the
nitrogenous base carbons
phosphodiester linkages
Nucleotides are linked into
polynucleotides by
phosphodiester linkages
Polynucleotides have a 5´ end
(phosphate group) and a 3´ end
(hydroxyl group).
DNA molecules have directionality
- has important implications for the
biological roles of DNA and RNA.
A DNA molecule consists of two
“antiparallel” nucleotide strands
(running in opposite directions
One strand runs 5’ to 3’,
the other runs 3’ to 5’
DNA
contains A, C, G, T; usually doublestranded,
has a deoxyribose pentose sugar
RNA
contains A, C, G, U; usually singlestranded,
has a ribose pentose sugar
DNA in the cell nucleus
contains the instructions
for protein synthesis.
Every three nucleotides
codes for an amino acid.
messenger RNA
The code is exported from the nucleus in the form of an RNA copy called messenger RNA (mRNA).
Ribosomes translate
mRNA to proteins.
The nucleotide
sequence of the DNA
molecule comprises
discrete units of
inheritance called
genes that specify
functional proteins
Individual genes can be
from
100’s to 1000’s of
nucleotides long.
