Proteins serve a variety of functions including?
Transport (myoglobin & Hemoglobin), structural, and motor function.
Myoglobin transports?
O2 throughout muscles.
Hemoglobin transports?
O2 in blood.
Myoglobin and hemoglobin are both _____ proteins, but many of the most abundant proteins are _____ proteins.
Globular; Fibrous proteins that are elongated and may assemble to form extended structures that determine the shape and other physical attributes of cells and entire organisms.
What forms microfilaments in cells?
Actin
What constitute microtubules?
Tubulin dimers
What constitutes the bulk of animal hair?
Keratin filaments
What is a major protein in connective tissue?
Collagen
The movements of cells and the movements of organelles within cells reflect the action of _____ that operate along tracks provided by cytoskeleton fibers.
Motor proteins
_____ interacts with _____ to facilitate muscular movement.
Myosin; actin
_____ moves along _____ to support a variety of cellular functions.
Kinesin; microtubules
Myo means _____ and globin means _____.
Muscle; Containing protein.
Myoglobin is a classical _____ protein.
Globular
Secondary structures are mostly what?
Alpha helices
What is a heme?
Iron-containing porphyrin derivative that is a type of prosthetic group.
A prosthetic group is?
Organic molecule bound to protein that aids protein function. Book definition= An organic compound that allows a protein to carry out some function that the polypeptide alone cannot perform.
Heme is a _____ that chelates iron for oxygen transport.
Porphyrin
Myoglobin transports O2 via what?
The Iron (Fe) in heme.
_____ residues play a key role in anchoring both O2 and iron.
His
What is often treated with iron supplements or an iron-rich diet?
Anemia
What is Myoglobin's function?
Cellular storage and transport of oxygen.
Myoglobin is most commonly found where?
In muscle cells
Myoglobin's tertiary structure?
Globular shaped protein with a hydrophobic pocket where a heme prosthetic group lies.
What is Myoglobin's binding mechanism?
Oxygen is sandwiched between the 6th coordination position of Fe (II) and His above it.
Oxygen binding to myoglobin depends on what?
The oxygen concentration.
Myoglobin binds to O2 in a _____ trend.
Hyperbolic trend
Fractional saturation (Y) is what?
The proportion of myoglobin molecules that have bound O2.
When finding out the amount of O2 bound to myoglobin (Y), the more oxygen gets you closer to what?
Saturation
When percent bound is 50%
PO2=K
When the K value, Myoglobin has _____ attraction to Oxygen.
High
Given Y is 50% and Mackerel PO2=1.9torr, Bonito PO2=1.6torr, and Tuna PO2=1.2: Myoglobin of which specie of fish has the highest K value?
Mackerel, because PO2 equals K when Y is 50%.
Given Y is 50% and Mackerel PO2=1.9torr, Bonito PO2=1.6torr, and Tuna PO2=1.2: Which specie of fish live in deeper ocean?
Tuna, the depression lowers oxygen and tuna is able to absorb oxygen because the smaller the K value the more aggressive and attracted it is to Oxygen.
What formula is used to calculate % saturation of myoglobin from PO2?
Y = PO2/K+PO2
At what pressure of oxygen will 75% of myoglobin be saturated? K=2.8torr
Y = PO2/K+PO2
0.75 = PO2/2.8+PO2
0.75 (2.8+PO2) = PO2
2.1+0.75PO2 = PO2
2.1 = 1.0 PO2-0.75 PO2
2.1 = 0.25PO2
2.1/0.25 = 8.4 torr (ANSWER)
What are true statements regarding the fractional saturation of myoglobin?
It is a function of Oxygen concentration, it is a function of Oxygen affinity, and the quantitative measure of Oxygen affinity is determined at 50% saturation.
Hemo means what?
Blood
What is the function of Hemoglobin?
Transport of oxygen from the lungs to the body tissues.
Hemoglobin is most commonly found where?
In red blood cells.
Hemoglobin's tertiary structure is?
Nearly identical to myoglobin (Globular shaped)
Hemoglobin's quaternary structure is?
Hetero-tetramer
What is the binding mechanism in Hemoglobin?
Oxygen binds to the heme group just as in myoglobin BUT is subject to steric regulation.
Myoglobin (Mb) and Hemoglobin (Hb) are similar in what structures?
Their secondary and tertiary structures. Their secondary and tertiary structures overlap almost perfectly when superimposed.
Which one does not have a quaternary structure? Hb or Mb?
Myoglobin does NOT have a quaternary structure.
Mb and Hb are only about ___ % identical in primary sequence.
18%
In a conservation of key amino acids in sequence alignment analysis, Identical means?
Positions where has the be that particular amino acid.
In a conservation of key amino acids in sequence alignment analysis, Conserved means?
Positions where is occupied by the same type of amino acids. Example: Only acidic or only small hydrophobic amino acids.
In a conservation of key amino acids in sequence alignment analysis, not conserved means?
Positions where any amino acid can occupy.
What do the similarities in structure and sequence between Mb and Hb indicate?
A common evolutionary origin.
Oxygen binds _____ to Hb.
Cooperatively, meaning hemoglobin's four heme groups are not independent but communicate with each other in order to work in a unified fashion.
O2 binding to myoglobin is a?
Hyperbola
O2 binding to hemoglobin is a?
Sigmoid, which indicates cooperativity which is binding of O2 to one subunit induces easier binding to other subunits.
How does hemoglobin achieve this cooperative binding mechanism?
Hemoglobin's four heme groups are not independent but communicate with each other in order to work in a unified fashion.
What are the two conformations of hemoglobin?
Tense (deoxyhemoglobin) and Relaxed (oxyhemoglobin)
Which conformation of hemoglobin is in the lungs?
Relaxed oxyhemoglobin
Which conformation of hemoglobin is in muscles?
Tensed deoxyhemoglobin
T/F Hemoglobin only allows two conformations.
TRUE
_____ decreases Hb's O2 affinity.
Biphosphoglycerate (BPG)
BPG binds only to the _____ conformation of Hb.
Tense (deoxy)
BPG stabilizes what conformation of hemoglobin?
Tense, when you don't have BPG the hemoglobin is more in loading (relaxed) phase so they get oxygen.
What is a side effect of the conformation change in hemoglobin?
Bohr effect, which is the reduction of hemoglobin's oxygen-binding affinity when the pH decreases.
As pH _____, O2 affinity _____.
Increases; Increases
Single point mutation of Glu to Val causes what?
Sickle cell anemia
T/F The tertiary structures of myglobin, Alpha-hemoglobin and Beta-hemoglobin are nearly identical and are therefore nearly identical in primary structure.
FALSE, the tertiary structures are very similar but the amino acid sequences are only 18% identical.
The Bohr effect describes a lowered O2 affinity of Hb when the pH _____.
Decreases
T/F The affinity of Mb remains high at all O2 concentrations.
TRUE
T/F Hb exhibits different affinities at low versus high O2 concentrations.
TRUE
T/F The affinities of each of the 4 subunits of Hb are independent of each other.
FALSE, they are dependent on each other.
T/F Hb binds the first molecule of O2 more readily than the last.
FALSE, the 1st is the hardest to bind.
A typical eukaryotic cell contains what three types of cytoskeletal (intracellular) proteins that form fibers extending throughout the cell?
Microfilament, intermediate filament (Keratin), and Microtubules.
What provides structural support extracellularly?
Collagen
Microfilaments are made of what?
Actin
What are the functions of microfilaments?
Skeletal support in eukaryotes and cellular migration.
The diameter of microfilaments is?
70 A
The building blocks of microfilaments are?
Actin monomers made up of 375 amino acids (aa)
Microfilaments are powered by what?
ATP
What is the overall structure of a microfilament?
Double strand coiled filament with each actin monomer contacts four of its neighbors.
Special property of microfilaments
The filament is constantly assembling and disassembling from each end. The filament is said to be treadmilling when the rate of growing of one end match the rate dissembling of the other end.
Globular _____ subunits associate in a _____ chain to form a microfilament.
Actin; double
The end of the ATP site is known as the ___ end, and the opposite end is the ___ end.
(-) end; (+) end
Addition is usually much more rapid at the ___ end.
(+) end
Actin polymerization is driven by _____ of ATP to produce _____ plus _____.
Hydrolysis (splitting ATP by the addition of water); ADP plus inorganic phosphate.
Actin polymerization reaction is catalyzed by _____ but not by _____.
F-actin (filamentous actin); G-actin (globular monomeric form)
Most of the actin subunits in a microfilament contain bound _____.
ADP
T/F Polymerization of actin monomers is a reversible process, so the polymer undergoes constant shrinking and growing as subunits add to and dissociate from one or both ends of the microfilament.
TRUE
Treadmilling
When the net rate of addition of subunits to one end of a microfilament matches the net rate of removal of subunits at the other end, the polymer is said to be treadmilling.
Cells can crawl by the _____ effect.
treadmill
In actin filaments, the nucleotide-binding sites are pointing to which end?
(-) end
Typically, which end of the actin filament grows faster?
(+) end
What is the function of a intermediate filament?
Exclusively skeletal support (structural proteins)
What is the diameter of a intermediate filament?
100A
What are the building blocks of a intermediate filament?
A dimer of alpha-helices in a left-handed coiled coil conformation.
The basic structural unit of a intermediate filament is?
A dimer of alpha helices that wind around each other which is called a coiled coil.
Intermediate filaments are assembled by what?
Hydrophobic interactions
What is the overall structure of an intermediate filament?
Cable like structure with 16 to 32 polypeptides at the cross section.
What is a special property of intermediate filaments?
Each alpha helix has a repeating pattern of seven amino acids when 1st and 4th positions are always hydrophobic residue. Crosslinking by disulfide bonds further stabilizes the intermediate filaments.
_____ is an intermediate filament.
Keratin
Keratin forms a _____ structure.
Coiled-coil structure which is a dimer of alpha helices.
What is the order that ultimately produces an intermediate filament composed of 16 to 32 polypeptides.
Monomer -> Dimer (coiled-coil) ->Tetramer ->Octamer ->Intermediate filament.
Our hair and finger nails are made out of what?
Keratin intermediate filaments
_____ can be observed in dividing cells.
Microtubules
_____ are shown in green fluorescence and _____ are detected in blue fluorescence.
Microtubules; chromosomes
Compared to an actin filament, which is thin and flexible, a microtubule is?
A microtubule is about 3 times thicker and much more rigid because it is constructed as a hollow tube.
What are the functions of Microtubules?
Skeletal support and cell mobility.
What is the diameter of a microtubule?
240A
What is the basic structural unit of a microtubule?
The protein tubulin.
What are the building blocks of microtubules?
Heterodimer made up of alpha and beta tubulins.
Microtubules are assembled by what?
Hydrophobic interactions and binding of a guanine nucleotide, either GTP (Guanosine triphosphate) or its hydrolysis product GDP (Guanosine diphosphate). GTP and GDP interactions.
What are the regulatory mechanism for microtubules?
GTP bound tubulins assemble and GDP bound tubulins disassemble.
What is the overall structure of microtubules?
Rigid tube like structure made up of 13 protofilaments.
What is a microtubules special property?
The (+) end of the microtubule grows and disassembles twice as fast as the (-) end.
Alpha and beta tubulin form _____.
Dimers
Microtubules are _____ fibers built from _____.
Hollow; tubulin dimers
_____ microscopy reveals tubular structure of a microtubule.
Cryoelectron
How many protofilaments make up the wall of the microtubule?
13
What is the function of Collagen?
Support of extracellular matrix.
What is the diameter of collagen?
15A
What are the building blocks of collagen?
Triple helix made up of three polypeptide with a common repeating pattern of Gly-Pro-Hyp
Collagen is assembled by what?
Hydrogen bond interactions and covalent linkers.
Collagen is typically found where?
in tendons, connective tissues and bones.
What is a special property of collagen?
Pound for pound, stronger than steel. The protein contains large amounts of proline and hydroxyproline. Hydroxyproline is converted from regular proline by a mechanism which involves vitamin C.
Every 3rd amino acid in Collagen is _____. _____% of remaining amino acids are proline(Pro) or hydroxyproline(Hyp).
Gly; 30%
The most stable conformation for a polypeptide sequence containing repeating units of Gly-Pro-Hyp is what?
A narrow left-handed helix.
In collagen, three polypeptides wind around each other to form what?
A right-handed triple helix
The collagen triple helix is stabilized through what?
Hydrogen bonding
Collagen molecules _____ cross-linked. Which stabilizes collagen's structure.
Covalently. The cross-links are covalent bonds between side chains that have been chemically modified following polypeptide synthesis.
Collagen is mostly found in what type of tissue?
Tendon
What is the force that keeps the collagen fibers together?
Covalent bonds and hydrogen bonds.
A protein found in hair, horns, nails and feathers is what?
Keratin
Which of the following assembles by association of multiple protofilaments?
Tubulin
What are the two motor proteins?
Myosin and Kinesin
What is the function of Myosin?
Converts chemical energy stored in ATP to mechanical energy used for motion.
What is the overall structure of Myosin?
In the muscle hundreds of myosin tails associate to form a thick filament with the head domains sticking out.
What is structure of Myosin?
Each myosin protein is made up of two large polypeptides that form two globular heads attached to a long tail.
What is the mechanism of motion of Myosin?
Sandwiched between layers of actin filaments. Myosin thick filament crawls along the actin with continue hydrolysis of ATP.
What is a special property of Myosin?
The "cocking" of the myosin heads uses one ATP.
Myosin has _____ heads and a long _____.
Two; tail
Each head includes a binding site for _____ and a binding site for an _____.
Actin; adenine nucleotide
In the tail region, the two polypeptides twist around each other to form what?
A single rodlike coiled coil (similar to what occurs in intermediate filaments. The tail is hydrophobic.
In a muscle cell, hundreds of myosin tails associate to form a _____ filament with head domains sticking out. These heads act as cross-bridges to _____ filaments, which consist of an actin filament and actin-binding proteins that regulate the accessibilit
Thick; thin
What happens when a muscle contracts?
The multitude of myosin heads individually bind and release actin, which causes the thin and thick filaments to slide past each other. The action of myosin on actin results in an overall shortening of the muscle.
What drives the physical movement of myosin along an actin filament?
ATP hydrolysis
What are the steps in the myosin-actin reaction cycle?
1.) Reaction sequence begins with a myosin head bound to an actin subunit on the thin filament. ATP binding alters the configuration of the myosin head so that it releases actin.
2.) Hydrolysis of ATP to ADP +P triggers change that rotates myosin lever an
_____ is a microtubule-associated protein.
Kinesin
What is the function of Kinesin?
Transportation of cellular cargos along the microtubule filaments.
What is the overall structure of Kinesin?
Similar to myosin, kinesin protein is also made up of two large polypeptides that form two globular heads attached to a long tail. The difference is Kinesin does not form large bundle filament. Also kinesin has two small peptides on the ends of its tail f
What is the mechanism of motion of Kinesin?
With each hydrolysis of ATP the kinesin heads "walks" along the microtubule filament from (-) end to (+) end.
What is a special property of Kinesin?
The kinesin heads only binds to the beta tubulin subunits of the filament.
What are the steps of the Kinesin reaction cycle?
1.) ATP binds to the leading head. Movement swings the trailing head forward toward the (+) end of the microtubule.
2.) The new leading head binds to a tubulin subunit releasing its ADP. This step moves kinesin's cargo forward along the protofilament.
3.)
Which of the two proteins below has a binding site for tubulin? Myosin or Kinesin
Kinesin
What statements regarding myosin and kinesin are true?
There are 2 polypeptide chains in each molecule, in each monomer there is a globular head and a long tail, and the head contains a nucleotide-binding site.