lecture 6 Flashcards
what are proteins made up of?
proteins are made up of alpha amino acid monomers that are linked to peptide bonds
what is the polymer of protein?
dipeptides and polypeptides with three or more amino acids linked together by peptide bonds
what determines the functions of proteins?
the shape and amino acid sequence
proteins are in almost every cellular function
what is the monomer of proteins?
amino acids
what is the structure of amino acids?
alpha carbon attached to an amino group and a carboxyl group
what types of forms can amino acids occur in?
a,b,y forms
alpha, beta, y=third carbon
what is GABA?
gamma-aminobutyric acid
y-amino acid that functions as a neurotransmitter that is responsible for neuron firing ( helps you relax )
What are D and L isomers of amino acids?
enantiomers
which isomers ( D or L ) of amino acids is used as building blocks of proteins?
L isomers
True or false
Amino acids are great biological buffers?
true
-they maintain the pH range of cells
what do amino acids do at a low pH?
the carboxyl and amino group accept a proton and becomes protonated
-NH3+
what do amino acids do at a high pH?
the carboxyl and amino group donates a proton and becomes dissociated
-COO-
what are zwitterions?
the term for when amino acids are present in their dipolar ionic state
what do the chemical and physical properties of the R group in amino acids do?
it determines the unique characteristics of a particular amino acid.
Are the R groups polar or non polar?
non polar
Are the R groups polar/electrically charged or non polar?
polar/electrically charged
look for positive charge (+) or look for carboxyl or hydroxyl
the structural and functional diversity of proteins is based on what?
based on the different arrangements of amino acids.
proteins predominantly made of leucine would be hydrophobic or hydrophilic?
hydrophobic ( non polar )
proteins predominantly made of Serine would be hydrophobic or hydrophilic?
hydrophilic ( polar )
what is the polypeptide backbone of proteins?
the repeating structure of atoms with side chains coming out like charms on a bracelet
what is the N-terminus of polypeptides?
the free amino end
what is the C-terminus of polypeptides?
the free carboxyl end
where does the energy go when forming a bond and when a breaking a bond?
forming a bond= energy in
breaking a bond = energy out
what are the four levels of protein structure?
1) primary structure: amino acid sequence
2) secondary structure: coiling and folding in the polypeptide chain
3) tertiary structure: overall 3D shape that is determined by the amino acid side chains
4) Quaternary structure: association of multiple polypeptide chains
In the primary structure, what determines the sequence of the amino acid chain?
the nucleotide sequence of the gene that encodes the protein
what are these bonds called?
peptide bonds
what occurs in sickle-cell anemia?
the negatively charged amino acid is replaced by a nonpolar one resulting in altered protein folding ( affecting the secondary and tertiary structure of protein ) -> this occurs in the primary structure
what are the two types of forms created during the secondary structure of proteins?
1) alpha helix ( coiled - holds helix cells in shape)
2) Beta pleated sheet ( folded - hold neighboring strands of sheet together )
alpha helix = fibrous proteins of wool, skin, nails
beta pleated sheet = globular proteins, fibroin, silk protein produced by spiders
at which level of protein stucture is the protein given its final shape?
tertiary stucture= given a 3D shape of the folded polypeptide chain
what are the four possible interactions in the tertiary structure?
1) hydrogen bonds
2) hydrophobic interactions
3) disulfide bridges
4) ionic bonds
what are the two forms of tertiary structure?
1) globular ( combinations of a-helices and b-sheets, roughly spherical)
2) Fibrous ( consisting of a-helices )
what is hemoglobin?
a globular protein with four polypeptide subunits in the quaternary structure.
what is collagen?
a fibrous protein consisting of three helical polypeptides coiled together
what is protein folding?
when a cell synthesizes polypeptides they must fold into their correct shape or conformation
what are chaperonins?
protein complexes which separate new polypeptides from the potentiallly disruptive chemical conditions within the cytoplasm.
what are monomeric proteins?
proteins made of single polypeptide chain (no quaternary structure )
what are oligomeric proteins?
proteins that consist of two or more polypeptide chains
what is a conjugated protein?
protein that contains amino acids and some other chemical group, a prosthetic group
what is a simple protein?
a protein only made up of amino acids
doesn’t combine with other macromolecules
what is protein denaturation?
the process by which involves the disruption and possible destruction of both the secondary and tertiary and sometimes quaternary structures.
causes the coilage of a random shape
what can cause protein denaturation?
- heat ( frying an egg, boiling milk )
- alcohol ( causes H-bonds to form between the new alcohol molecule and the protein side chains instead of normal H-bonds)
- change in pH
Give an example of denaturation in disease.
- mutations
- Alzheimer’s diease -AD (presence of protein plaques and neurofilbrillary tangles in the brain)
- cancer ( caused by misfolding of proteins that function as tumor-suppressor agents )
what are prions?
misfolded proteins that become an infectious agent
- can affect the structure of the brain or neural tissue causing untreatable fatal damage
Why is prion dieases collectively called spongiform encephalopathies?
because they cause sponge-like vacuoles in the brain.
i.e. mad cow disease
what are the two forms that prions exist as?
1) version consisting of three alpha helical regions and two short beta sheets
2) misfolded form made of beta sheets (infectious agent)
what is happening in this image?
Prion proteins are attaching to normal proteins and infecting them causing them to become a prion and affect other prions.
what are the 8 protein functions?
1) enzymatic proteins
2) storage proteins
3) chemical messenger proteins
4) contractile and motor proteins
5) defensive proteins
6) transport proteins
7) receptor proteins
8) structural proteins
what is the role of enzymatic proteins?
function is to accelerate chemical reactions
what is the role of storage proteins?
function is to provide a source of amino acids for developing embryos or developinh infants (milk)
what is the role of chemical messengers?
its role is to coordinate an organism’s activities such as hormones ( endocrine system ) and neurotransmitters ( nervous system )
ex: insulin , acetylcholine ( ACh)
what is the role of contractile proteins?
function in movement
muscle movement, undulations of cilia and flagella
what is the role of defensive proteins?
function as defensive substances within the body
parasite, bacteria, virus
what is the role of transport proteins?
function is to move substances within the body or in and out of cells
hemoglobin
what is the role of receptor proteins?
function is to regulate the response of the cell to chemical stimuli
what is the role of structural proteins?
function is to provide support. They function in the cell membrane, muscle tissue, tendons and ligaments
collagen and elastin = fibrous proteins
