Based on Our Current Understanding of Physics, We Can Understand

question 59

Multiple Choice

Based on our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as about ________.

• A) one ten-billionth of a second after the Big Bang
• B) 380,000 years after the Big Bang
• C) 10⁻⁴⁵ seconds after the Big Bang
• D) 10 billion years ago

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Definitions:

Basement Membrane

A thin, fibrous structure that lies underneath epithelial cells, providing support and anchorage, and acting as a barrier against the spread of cells.

Gap Junction

Junction between cells formed by the joining of two adjacent plasma membranes; it lends strength and allows ions, sugars, and small molecules to pass between cells.

Adhesion Junction

Junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to buttonlike thickenings.

Tight Junction

A complex of proteins in the cell membrane that creates a watertight seal between cells, preventing leakage of extracellular fluid.