Question answer :
1) Explain how cell membranes are selectively permeable.
=) The membrane is selectively permeable because substances do not cross it indiscriminately. Some molecules, such as hydrocarbons and oxygen can cross the membrane. Many large molecules (such as glucose and other sugars) cannot. Others actually bind to the molecules and move them across the membrane.
2) Compare and contrast the processes of osmosis and diffusion.
=) Osmosis only allows solvent molecules to move freely, but diffusion allows both solvent and solute molecules to move freely. Osmosis happens when molecules move from higher to lower concentrations, but diffusion happens when it is reversed.
3) Identify the molecules that help
substances move through the cell
membrane during active transport and facilitated diffusion.
=) Carrier proteins such as uniporters, symporters, and antiporters perform primary active transport and facilitate the movement of solutes across the cell's membrane.
4) Why are endocytosis and exocytosis important processes to cells?
=) Endocytosis and exocytosis are important mechanisms for bringing substances into and out of a cell. Cells use exocytosis to secrete proteins. ... Three types of endocytosis bring substances into the cell. Using phagocytosis, certain protists and white blood cells are capable of engulfing very large particles.
5) Why are fresh fruits and vegetables sprinkled with water at produce markets?
=) Produce is sprayed with water to keep it hydrated and fresh. Without this “misting”, many types of vegetables would wilt and lose their crispness. ... Once they have been harvested, they will lose their freshness, attractiveness, and crispness if they are not regularly sprayed with water.
6) tell the difference between passive transport and active transport. Begin with the phrase "Trans- port through membranes."
=) Transport down the concentration gradient is known as passive transport. Active transport, on the other hand, involves the net transport of a material against its concentration gradient. Active transport must be mediated by a protein, and it requires an input of energy in order to oppose the concentration gradient.
7) Seawater is saltier than tap water. In your Science Journal, explain why drinking large amounts of seawater would be dangerous to humans.
=) In the beginning, the primeval seas were probably only slightly salty. But over time, as rain fell to the Earth and ran over the land, breaking up rocks and transporting their minerals to the ocean, the ocean has become saltier. Rain replenishes freshwater in rivers and streams, so they don't taste salty.
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