Question

directions: answer the following questions.

1. describe the structure of the cell membrane.

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1. hydrophilic means \water - loving\ or having an affinity for water. what do you think hydrophobic means?

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1. how is active transport different from passive transport?

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1. summarize the role of vesicles in endocytosis and exocytosis.

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Explanation:

1. The cell membrane is a phospholipid bilayer. It has phospholipids with hydrophilic heads and hydrophobic tails. Proteins are embedded or attached to it. Cholesterol is also present (in animal cells).
2. Since "hydrophilic" is "water - loving", by contrast, "hydrophobic" means "water - fearing" or having no affinity for water.
3. Active transport requires energy (usually ATP) and moves substances against their concentration gradient. Passive transport does not require energy and moves substances down their concentration gradient (either through simple diffusion or facilitated diffusion).
4. In endocytosis, vesicles form to bring substances into the cell. In exocytosis, vesicles fuse with the cell membrane to release substances out of the cell.

Answer:

1. The cell membrane is a phospholipid bilayer with embedded/attached proteins and (in animal cells) cholesterol. Phospholipids have hydrophilic heads and hydrophobic tails.
2. Hydrophobic means “water - fearing” or having no affinity for water.
3. Active transport requires energy (ATP) and moves substances against the concentration gradient. Passive transport does not require energy and moves substances down the concentration gradient.
4. In endocytosis, vesicles form to take substances into the cell. In exocytosis, vesicles fuse with the membrane to release substances out of the cell.