wk 14 - proteins
Disulfide bonds
Strong chemical side bonds formed when the sulfur atoms in two adjacent protein chains are joined together
Primary structure of protein
The first level of protein structure; the specific linear sequence of amino acids joined by peptide bonds making up a polypeptide chain. coded for in the gene of DNA
Dipeptide
Two amino acids bonded together
Peptide bond
a bond that holds amino acids together; chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid
Sickle cell anemia
a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle (half moon) shape. happens when one amino acid is out of place. the GLU is replaced with a valene
The 'R' in a amino acid represents
a hydrogen or carbon-hydrogen group
What is formed by the linking of two amino acids
a peptide bond
Following a dehydration reaction of an amino acids
a peptide bond joins two amino acids and a water molecule is realeased
Actin and myosin
account for the movement of cells and the ability of our muscles to contract
Functional proteins are usually
alpha helix
Functional proteins shape
alpha helix
Coiling of the chain results in a
alpha helix - right handed spiral or slinky like shape
Two types of secondary structure
alpha helix and beta pleated sheet
Two types of secondary structure are possible. They are called the __________ and the ________
alpha helix and the beta pleated
The secondary structure is often an ______ or ________
alpha helix; beta pleated sheet
Building blocks of proteins
amino acids
Genes determine the sequence of
amino acids (eye color, hair, skin, nails, etc)
Proteins usually have >50
amino acids and are usually used more than once
Amino acids contain what functional groups
amino and carboxyl
-NH2 represents
amino group
Amino acid contains
amino group (-NH2), carboxyl group (-COOH) and R group varies, determining uniqueness of each amino acid
All amino acids have a _____ group and a _____ group
amino; carboxyl
The activity of many proteins (and enzymes) depends on the presence of
an active site that "fits" into a specific substrate
In enzymes the polypeptide..
bend and twists in different ways
Structural proteins are usually
beta pleated
Structural proteins shape
beta pleated proteins
Folding of the chain results in a
beta pleated sheet - similar to a hand held fan
The tertiary structure gives proteins their
biological activity
If a protein is denatured then the parts of the active site are no longer in close proximity, can no longer "fit" into the substrate, and therefore
cannot react
4 types of organic molecules
carbohydrates, lipids, proteins, nucleic acids
All proteins contain the same 4 elements
carbon, hydrogen, oxygen and nitrogen
-COOH represents
carboxyl (acid) group
in a peptide bond, the bond occurs between a
carboxyl group of one amino acid and amino group of another amino acid
Functional proteins
category of proteins that affect the functional operations of a cell; proteins that cause chemical changes in the molecules
Dentaure
change in the shape of an enzyme so that it can no longer speed up a reaction
The 'R' group gives each amino acid its
chemical properties
Hemoglobin
complex protein (iron-containing protein) in red blood cells that carries oxygen to your body's organs and tissues and transports carbon dioxide from you organs and tissues back to your lungs
Amino acid
compound with an amino group on one end and a carboxyl group on the other end
When proteins are exposed to extreme heat or pH they undergo an irreversible change in shape
denature. a protein denatures when it loses structure and function.
Hydrogen bonds in a protein are broken, then the shape of the protein can change, making it incapable of performing its physiologic function. The protein is said to be
denatured
What type of bond holds the secondary structure together
hydrogen bonds holds the secondary structure together
Amino acids are put together by dehydration synthesis and broken up by
hydrolysis reaction
The hydrogen bonding in amino acid
influences the structure and shape of a protein
If the hydrogen bonds in a protein can easily re-form, then the denaturation reaction is said to be
reversible
the regular reoccurring arrangement of the amino acid chains is called the ______________ of a protein
secondary structure
Hydrogen bonds hold
secondary structure together
Tertiary structure occurs when a polypeptide bends and twists into a
three-dimensional shape
Most enzymes have a quaternary structure
thus, proteins can differ in many ways, such as in length, sequence and structure
A ______ consists of three amino acids held together by ________ bonds
tripeptide; peptide
Each individual protein is
unique
Tertiary structure is maintained by
various types of bonding between R-groups; covalent bonding, ionic bonding, hydrogen bonding and disulfide bonding
Final shape of protein
very important; determines its function
The hydrophobic portions are packed mostly on the inside and the hydrophilic portions are on the outside where they can make contact with..
water
Everything is determine by the primary structure. If the primary structure is out of sequence then the rest of the sequence
will be out of whack
_______ bonds between the peptide bonds holds the shape in place
hydrogen
Proteins perform many functions
-catalyzing biochemical reactions -serving as receptors and transporters -aiding movement
Examples of structural proteins
-keratin (makes up hair and nails) -collagen (leads support to ligaments, tendons, and skin) -spiderwebs -silk
Proteins in plasma membranes of cells have various functions
-some form channels that allow substances to enter and exit (channels allow substances to cross membranes) -some are carriers that transport molecules into and out of the cell -some are enzymes
Examples of functional proteins
1. enzymes 2. hormones 3. actin and myosin 4. hemoglobin 5. immunoglobulins
Proteins 4 levels of structure
1. the sequence of its amino acids 2. the folding or coiling of the polypeptide chain 3. the complete, three-dimensional arrangement of a polypeptide chain 4. (only if the protein has more than one chain) the way in which the different polypeptides are arranged
There are _____ common amino acids found in living organism's
20
Primary structure of a polypeptide is its own particular sequence of the possible
20 types of amino acids
As these chains form the polypeptide develops multiple levels of structure, which contributes to its overall shape
4 levels of protein organization
Polypeptide
A polymer (chain) of many (~4-50) amino acids linked together by peptide bonds.
Plasma membrane
A selectively-permeable phospholipid bilayer forming the boundary of the cells
What types of bond holds these secondary structures together
hydrogen bonds
Enzymes
Catalysts for chemical reactions in living things; some proteins act as enzymes
Hormones
Chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another, influence cellular metabolism
Polarity of peptide bond
H bonding is possible between C-O of one amino acid and N-H of another amino acid in polypeptide
The chemical differences between one amino acid and another is due to
R group
Amino acids differ from one another by their
R group. R group varies from having a single carbon to being a complicated ring structure
In enzymes, the polypeptide bends and twists in
different ways
A ______ consists of two amino acids held together by a ________ bond
dipeptide; peptide
Proteins are broken down by
enzymes; hydrolyze them into amino acids
Amino acids are usually abbreviated by the
first 3 letters of their name
10 essential amino acids
for building proteins in body, need to get them from diet
Two or more polypeptides bond to make
functional protein
Genes tell your body how to sequence amino acids
genes are instructions for proteins that regulate the activity of other genes
In muscles, myosin molecules have a rod shape ending in a
globular (globe-shaped) heads
Examples of proteins with quaternary structures are
hemoglobin and the sodium channels in the cell membranes
In the denaturation of a protein, ________ bonds are broken
hydrogen
If the hydrogen bonds cannot re-form then the process is termed
irreversible denaturation
Each polypeptide has its own sequence of amino acids and
its own sequence of R groups
The shape of proteins determines
its structure
Proteins
long chain molecules composed of amino acids bonded together
Protein buffers
nearly all proteins can function as buffers. Proteins are made up of amino acids, which contain positively charged amino groups (-NH2) which acts as an H+ acceptor, and negatively charged carboxyl groups (-COOH) which act as an H- donor. The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers.
If the hydrogen bonds in a protein are broken, can the protein easily maintain its structural shape?
no
Enzymes cannot function unless they have their
normal shape
Tripeptide
three amino acids bonded together
Beta pleated sheet consists of parallel strands of polypeptides
parallel strands of polypeptides
What type of bond holds the amino acids together in the primary structure
peptide
What type of bond holds the primary structure together
peptide bonds hold the primary structure together
A ______ consists of many amino acids held together by a ________ bonds
polypeptide; peptide
The linear sequence of amino acids in a protein is called _____________ of that protein
primary structure
Some proteins have only one polypeptide and others have more than one polypeptide, each with its own....
primary, secondary and tertiary structures
4 levels of protein organization
primary, secondary, tertiary, quaternary
Immunoglobulins
protect cells. proteins that bind with specific antigens (foreign substances; toxins) in the antigen-antibody response. preventing them from destroying cells and upsetting homeostasis.
Every cell in the body carries out
protein synthesis (dehydration synthesis)
Amino acids bond together to form
proteins
Polymers composed of amino acids monomers
proteins
Denaturation occurs when
proteins encounter hostile environments such as temperature and pH, and therefore lose their shapes and functions; the normal bonding between R-groups are disturbed
Structural proteins
provide physical stability and movement; form an organism's physical attributes, give support.
Hemoglobin is a complex protein that has a _________ structure
quaternary
What level protein structure is determined by interactions of more than one polypeptide chain
quaternary
A protein can contain several, polypeptides and this accounts for a possible _________
quaternary structure
In proteins with multiple polypeptide chains these separate polypeptides are arranged to give such proteins a fourth level of structure termed..
quaternary structure
Separate polypeptide chains are arranged to give this the highest structure
quaternary structure
Factors that can denature proteins include
strong acids, heat, alcohol, and salts of heavy metals
Bond between R groups are
strong bonds
Proteins are molecules of
structure and function
Some proteins contain
sulfur, iron and phosphorus in addition to carbon, hydrogen oxygen and nitrogen
Interactions between r-groups hold
tertiary and quaternary structure together
Polypeptide chains can be made up of any combination of
the 20 different amino acids
Quaternary structure of protein
the 4th level of protein structure; the shape resulting from the association of two or more polypeptide subunits, only if proteins have more than one chain. occurs when two or more polypeptides interact to perform a biological function
Following a hydrolysis reaction of a polypeptide
the bond is broken with the addition of water
Secondary structure of protein
the second level of protein structure; the folding or coiling of the polypeptide chain. Protein takes on a certain orientation in space due to hydrogen bonding between amino acids causing the polypeptides to form and beta pleated sheet or and alpha helix.
Tertiary structure of protein
the third level of protein structure; the overall 3D shape of a polypeptide due to the interactions of the amino acid side chains with water, covalent bonding between R-groups, and other chemical interactions determine the folded 3D shape of a protein. complete 3D arrangement of a polypeptide
Atoms associated with peptide bond unevenly because oxygen is more electronegative than nitrogen
therefore, a hydrogen attached to nitrogen has a slightly positive charge, while oxygen has a slightly negative charge
In some cases proteins can form quaternary structures, which consists of interactions between multiple proteins
these interactions often result in the formation of large protein complexes
The coil of alpha-helix consists of loops of the linear arrangement of the amino acids
these loops are held together by bonds between the O of the C=O of one amino acid and the H of the NH of another amino acid
When your body breaks down proteins
they break down into amino acids and then your body reassembles them for different use