Water can diffuse directly across lipid bilayers, but ions cannot. What aids the ions in water in entering or exiting a
cell?
a. transport proteins in a cell’s cytoplasm
b. transport proteins in a cell’s plasma membrane
c. sugars produced in source regions
d. organic compounds stored in plant tissues
e. companion cells
ANSWER: b
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This unique feeding structure, called a lophophore, is found in which of these groups?
1.brachiopods
2.bivalves
3.porifera
4.polychaetes
The female external genitalia are collectively known as the ____
a. ovary b. oviduct c. vagina d. vulva e. uterus
The respiratory membrane is a combination of
A) bronchi and air sacs. B) bronchioles and capillary walls. C) alveolar and capillary walls. D) bronchi and bronchioles. E) bronchioles and air sacs.
Pre-mRNA splicing does not involve which of the following structural features?
a. 5? cap b. branch site c. 3? splice site d. 5? splice site e. All of these structural features are involved in pre-mRNA splicing.