More Than Half a Century Ago, Two Cell Biologists Published

question 18

Multiple Choice

More than half a century ago, two cell biologists published details of their research involving isolated membrane vesicles from chloroplasts. Normally, the fluid inside these vesicles is near neutral. In an experiment, these membrane vesicles were soaked in an acidic solution (pH 4) until the inside of the vesicle also became pH 4. Based on the details provided in this scenario, by what mechanism could hydrogen ions have crossed the vesicle membrane, and what do you think happened at the molecular level?

• A) Simple diffusion; hydrogen ions moved into the vesicle through a channel protein.
• B) Active transport; hydrogen ions moved out of the vesicle with the help of ATP energy.
• C) Facilitated diffusion; hydrogen ions moved into the vesicle through a channel protein.
• D) Pinocytosis; water moved from outside the vesicle to inside.
• E) Osmosis; water moved from inside the vesicle to outside.

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Definitions:

Bronfenbrenner's Systems

A theoretical model that explores how different environmental systems influence human development, ranging from immediate surroundings to broader societal cultures.

Microsystem

The immediate settings with which the child interacts, such as the home, the school, and the child’s peers.

Exosystem

Community institutions and settings that indirectly influence the child, such as the school board and the parents’ workplaces (from the Greek exo, meaning “outside”).

Ethologists

Specialists who study animal behavior in natural environments, focusing on how animals interact with each other and their surroundings.