The contractile unit of a muscle is the ____.
A. sarcomere
B. myosin head
C. phosphate group
D. myofibril
E. actin filaments
Answer: A
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Which epithelial cell is modified for diffusion?
a. cuboidal b. simple squamous c. simple columnar d. stratified squamous e. stratified columnar
The chorionic villi eventually form the placenta, a disc-shaped structure that ____
a. releases sex hormones at appropriate times throughout pregnancy b. initiates uterine contractions c. binds to the zygote to accelerate organ development d. nourishes the embryo throughout pregnancy e. prevents infection by blocking the passage of microorganisms through the cervix during pregnancy
What was the purpose of the spark chamber in this experimental apparatus?
a. To generate heat
b. To produce ATP
c. To stop the reaction
d. To generate lightening
e. To produce UV radiation
The lateral movement of transmembrane proteins can be restricted by several different mechanisms
Which mechanism best describes the process by which nutrients are taken up at the apical surface of the epithelial cells that line the gut and released from their basal and lateral surfaces? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier