Answer the following question given this paragraph: Ions such as sodium (Na + ), potassium (K + ), calcium (Ca 2+ ), and chloride (Cl - ), are important for many cell functions. Because they are charged (polar), these ions do not diffuse through the membrane. Instead they move through ion channel proteins where they are protected from the hydrophobic interior of the membrane. Ion channels allow the formation of a concentration gradient between the extracellular fluid and the cytosol. Ion channels are very specific, as they allow only certain ions through the cell membrane. Some ion channels are always open, others are "gated" and can be opened or closed. Gated ion channels can open or close in response to different types of stimuli, such as electrical or chemical signals. Q: Because they are charged (polar), these ions do not diffuse through what? A:
OPTIONS:
- substrate
- cell wall
- protein
- membrane

Answer: membrane

Answer the following question given this paragraph: Even though large life forms have been very successful on Earth, most of the life forms on Earth today are still prokaryotessmall, relatively simple single-celled organisms. As it is difficult to identify, observe and study such small forms of life, most of these organisms remain unknown to scientists. Advancing technologies, however, do allow for the identification and study of such organisms. Q: What is a small, relatively simple single-celled organism called? A:
OPTIONS:
- ribosome
- amoeba
- eukaryote
- prokaryote

Answer: prokaryote

Answer the following question given this paragraph: Note Today, new elements are usually named after famous scientists. The names of the elements can be cumbersome to write in full, especially when combined to form the names of compounds. Therefore, each element name is abbreviated as a one- or two-letter chemical symbol. By convention, the first letter of a chemical symbol is a capital letter, while the second letter (if there is one) is a lowercase letter. The first letter of the symbol is usually the first letter of the element's name, while the second letter is some other letter from the name. Some elements have symbols that derive from earlier, mostly Latin names, so the symbols may not contain any letters from the English name. Table 2.3 "Element Names and Symbols" lists the names and symbols of some of the most familiar elements. Table 2.3 Element Names and Symbols. Q: Today, new elements are usually named after famous scientists. the names of the elements can be cumbersome to write in full, especially when combined to form the names of compounds. therefore, each element name is abbreviated as a one- or two-letter chemical this? A:
OPTIONS:
- notation
- title
- shorthand
- symbol

Answer:
symbol