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BioChemistry
Final Exam Pt 4
| Question | Answer |
|---|---|
| Many molecular motors are members of the _____ family | P-loop NTPase |
| The first kinesin discovered was called _____ | conventional kinesin |
| In kinesin, a _____ undergoes conformational change after nucleotide binding | neck linker |
| The functional unit in a muscle cell is a | sarcomere |
| _____ is the name given to actin monomers | G-actin |
| _____ is a prokaryotic homolog of actin | MreB |
| An ____ is a bundle of nine microtubule pairs surrounding two singlet microtubules. | axoneme |
| A prokaryotic protein similar to tubulin is called a ____ | FtsZ |
| Flagella are used for ____ in bacteria. | chemotaxis |
| Molecules such as glucose that attract bacteria are termed ____ | Chemoatractants |
| Myosin light chains are related to the ____ family of proteins. | EF hand |
| A helical section that moves dramatically when NTP is bound is called the ____ in P-loop NTPases. | lever arm |
| Troponin reacts in response to the ion ____ | calcium |
| During a muscle contraction, the thin filaments (actin, tropomyosin, troponin) slide along the ______ | thick filaments |
| Single molecules of myosin in actions were studied using ____ | an optical trap |
| Actin likely evolved from a protein that bound ______ | ATP |
| Microtulules are tracks for kinesins and _____ | dyneins |
| Taxol inhibits the proliferation of cells by stabilizing the polymer form of ____ | microtubules |
| Bacterial flagella are polymers composed of 53-kd subunits of a protein called _____ | flagellin |
| Bacterial flagella rotate in one direction for smooth swimming and in the other direction to cause ____ | tumbling |
| Energy used to propel molecular motors includes | ATP, ion gradients |
| The major family(ies) of eukaryotic motor proteins is(are) | myosins, kinesins, dyneins |
| The structure of dynein lends itself to the formation of | oligomers |
| Binding of ATP causes ____ in myosin head affinity for actin filaments | a decrease |
| Binding of ATP causes _____ in kinesin affinity for microtubules. | an increase |
| Actin polymers will assemble | automatically by self-assembly |
| How is MreB similar to actin? | It folds into a similar tertiary structure, and Like F actin, it forms polymers. |
| What is the rate and distance of the movement of myosin heads? | Each head moves 5 times per second, approximately 110 Angstroms |
| How does the length of the lever arm affect the rate? | A mutated shorter arm has a reduced rate, and a mutated longer arm has a faster rate |
| Human spastic paraplegia has been linked to a mutation in | kinesin family genes |
| Bacterial motors differe from eukaryotic ones in that the bacterial motor | spins around a central axis |
| What is the energy source used to rotate the flagella? | proton gradient |
| The structure in bacteria that rotates is referred to as | the MS ring |
| The biased random walk motion of bacteria is the result of | swimming with more tumbling when moving away from a chemorepellant |
| Molecules that cause bacteria to swim away from toxic substances are | chemorepellants |
| How do molecular motors work? | Proteins undergo conformational changes, in very small increments, which are converted to motor type activity |
| To what families are myosin, kinesin, and dynein related (in humans)? | While amino acid sequences are varied, the 3-dimensional structures of myosin & kinesin are similar to the P-loop NTPase domains that r observed in G proteins. Dynein contains domains structurally similar to the P-loop NTPase domains in the AAA subfamily |
| Briefly describe the structure of myosin | Myosin consists of a long stalk-like region with two heads at one end. The ATP-binding domains are near the heads, and the long stalk serves as an attachment site to other proteins |
| What serves as the track for myosin? | Actin, in a polymeric form, serves as the molecular track for myosin |
| What is F-actin? | The filamentous form of actin is a helical structure formed from actin monomers. It resembles a two-stranded string or cable. One end contains a "point" and the other end is "barbed" |
| What was learned using the optical trap laser studies? | The Studies indicated myosin heads undergo structural changes in conformation when they bind to actin that pulls the actin filament, leading to a displacement of the beads.After a time period, the actin is released& rturns to orig position between 2 beads |
| Describe the experiment that supports role of the lever arm in myosin motor activity | Investigators deleted sequences to shorten the lever arm & inserted sequences to extend the lever arm. The rate of myosin movement along an active filament decreased as the lever arm was shortened & increased as the lever arm was extended |
| What is the cause of Charcot-Marie-tooth disease? | This neuropathy is caused by a mutation in kinesin type K1F1B~B |
| How does the action of kinesin differ from that of myosin on its track? | Myosin binds and releases actin after each stroke. In contrast, kinesin is a processive enzyme. The heads operate in concert, with one, then the other binding. |
| Compare the speed of movement of a motile bacterium to a human | the bacterium can move approximately 25 um/sec or about 10 body lengths. To achieve this a human would have to run a 100-m dash in 5 sec. |
| How is a bacterial motor similar to ATP synthase? | In both cases, a proton moving across a membrane into a channel causes a structure to rotate. |
| How are flagellin subunits arranged in the bacterial flagellum? | Flagellin subunits form helical polymers containing 5.5 subunits/turn. The subunits are arranged around a hollow core and can extend up to 15 um in length |
| Is the motion of a bacteria deliberate and exact toward a target chemoattractant, or is it random? | While the bacteria will eventually arrive at its source, there is a great deal of random movement caused by the tumbling as it seeks the proper direction |
Created by:
AshCha
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