Topic: Non Enzymatic Protein Function

Motor proteins are non-enzymatic proteins that perform mechanical movement in cells or muscles.

Motor proteins are a class of molecular motors that can move along the cytoplasm of animal cells. They convert chemical energy into mechanical work by the hydrolysis of adenosine triphosphate (ATP). Motor proteins include myosin, kinesin, and dynein. These aid in movement through exergonic ATP hydrolysis that causes conformational changes in these proteins.

Myosin is present in the muscles of the body. Conformational changes in myosin help in the contraction and movement of the muscles. Kinesin is present in the cell and helps in the movement of chromosomes during cell division as well as in the movement of vesicles in the cell. Dynein helps in the movement of single cell appendages like cilia and flagella.

Practice Questions


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MCAT Official Prep (AAMC)

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Sample Test B/B Section Passage 1 Question 4


Key Points

Motor proteins are a class of molecular motors that can move along the cytoplasm of animal cells.

Myosin, kinesin, and dynein are motor proteins.

Myosin helps in the movement of the muscles.

Kinesin helps in the movement of chromosomes and vesicles in the cell.

Dynein helps in the movement of cilia and flagella.


Key Terms

Exergonic: a reaction in which energy is released

Hydrolysis: a reaction in which breakdown of the molecule occurs due to reaction with water

Adenosine triphosphate (ATP):  an energy-carrying molecule found in the cells of all living things

Myosin: a fibrous protein that forms (together with actin) the contractile filaments of muscle cells and is also involved in motion in other types of cells.

Kinesin: a protein belonging to a class of motor proteins found in eukaryotic cells

Dynein: a family of cytoskeletal motor proteins that move along microtubules in cells

Hydrolysis: the chemical breakdown of a compound due to reaction with water



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