Question

1. what is the function of the cell membrane? 2. explain how the cell membrane is selectively permeable? 3. which requires more energy, moving particles with the concentration gradient or against? 4. what are the three kinds of passive transport? 5. what happens to a cell in an isotonic solution? hypertonic? hypotonic? 6. how is active transport different from passive transport? 7. what are the differences between endocytosis, exocytosis and phagocytosis? 8. why is transport important?

Explanation:

1. The cell membrane is a phospholipid - bilayer structure with embedded proteins. It is selectively permeable as it allows certain substances (like small non - polar molecules) to pass through easily while restricting others (large polar molecules, ions).
2. Passive transport with the concentration gradient (diffusion, facilitated diffusion, osmosis) does not require energy. Active transport against the concentration gradient requires energy (usually in the form of ATP) as it moves substances from an area of low concentration to high concentration.
3. In an isotonic solution, there is no net movement of water across the cell membrane, and the cell maintains its shape. In a hypertonic solution, water moves out of the cell, causing it to shrink. In a hypotonic solution, water moves into the cell, causing it to swell.
4. The three kinds of passive transport are simple diffusion (movement of small non - polar molecules), facilitated diffusion (movement of polar or large molecules with the help of transport proteins), and osmosis (movement of water across a semi - permeable membrane).
5. Active transport uses transport proteins and energy to move substances against the concentration gradient, unlike passive transport which relies on the concentration gradient.
6. Endocytosis is the process of taking substances into the cell by forming vesicles from the cell membrane. Exocytosis is the opposite, where vesicles fuse with the cell membrane to release substances outside the cell. Phagocytosis is a type of endocytosis where large particles are engulfed.
7. Transport is important for maintaining homeostasis within the cell, obtaining nutrients, getting rid of waste, and communicating with other cells.

Answer:

1. The cell membrane is a phospholipid - bilayer structure with embedded proteins that controls the movement of substances in and out of the cell, making it selectively permeable.
2. Active transport against the concentration gradient requires energy, while passive transport with the gradient does not.
3. In an isotonic solution, the cell maintains its shape; in a hypertonic solution, the cell shrinks; in a hypotonic solution, the cell swells.
4. The three kinds of passive transport are simple diffusion, facilitated diffusion, and osmosis.
5. Active transport uses energy and transport proteins to move substances against the concentration gradient, different from passive transport.
6. Endocytosis takes substances into the cell, exocytosis releases substances out of the cell, and phagocytosis is a type of endocytosis for engulfing large particles.
7. Transport is important for maintaining cell homeostasis, obtaining nutrients, removing waste, and cell - cell communication.