Hyaluronic acid gives a very slippery quality to fluids that contain it. Hyaluronic acid

A) resists stretching.
B) functions as an insulator.
C) is a good lubricant for joint cavities.
D) promotes oxygen transport in the plasma.
E) is a protein.

When Na⁺ is actively transported from tubular cells to the interstitial fluid,

A) no energy is needed.
B) glucose and amino acids are countertransported at the same time.
C) Na⁺ concentration gradient is established between the tubule lumen and tubule cell.
D) water is countertransported by carrier molecules.
E) water is secreted.

What evidence supports the idea that some nuclei are totipotent?

A) Nuclei taken from the cells of an embryonic frog can direct a frog egg to develop into a tadpole.
B) Nuclei taken from the cells of a frog embryo can direct any amphibian egg to develop into a tadpole.
C) Nuclei taken from a different species can direct a tadpole egg to develop into a normal tadpole.
D) Some cells are capable of undergoing unlimited cell cycles.
E) Some cells are capable of arresting their cell cycle at will.

Which statement is true about epithelial tissue?

A) Epithelial tissue helps to protect the body from bacterial invasion.
B) Epithelial tissue can be glandular.
C) Epithelial tissue can be found lining the tubules of the kidney.
D) Epithelial tissue may contain column-shaped cells.
E) All the answers are true statements.

There are more microbial cells than human cells in your body, and the health of this microbiota clearly influences human well-being. How many microbes are there?

A) For every cell in your body, there are ten microbial cells.
B) For every cell in your body, there are one hundred microbial cells.
C) For every cell in your body, there are one thousand microbial cells.
D) For every cell in your body, there are ten thousand microbial cells.

Which part of the sperm contains ATP-producing mitochondria?

A) head
B) middle piece
C) tail
D) acrosome
E) zona pellucida