Science Group
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Science Group
Answer: Most plant cells lack centrioles, although animal cells typically contain them.
Answer: Both plant and animal cells have a true nucleus and membrane-bound organelles, so both are eukaryotic.
Answer: The rigid cellulose cell wall gives plant cells their definite shape.
Answer: Plastids are organelles found in plant cells; animal cells do not contain them.
Answer: Plant cell walls are made of cellulose, which provides strength and support.
Answer: The cell wall protects the cell and gives it mechanical support.
Answer: The cell wall allows almost all substances to pass through it, so it is fully permeable.
Answer: The middle lamella, which cements adjacent cells together, is made chiefly of pectin.
Answer: Fungal cell walls are made of chitin, not cellulose as in plants.
Answer: Lignin is deposited in secondary cell walls, making them hard, thick, and impermeable.
Answer: The cell wall is non-living and rigid, unlike the living plasma membrane.
Answer: The plasma membrane is built on a double layer (bilayer) of phospholipid molecules with embedded proteins.
Answer: Singer and Nicolson proposed the fluid mosaic model in 1972, describing proteins floating in a fluid lipid bilayer.
Answer: A selectively permeable membrane permits some molecules to pass while preventing others.
Answer: In the fluid mosaic model, proteins float in or on the fluid phospholipid bilayer like mosaic pieces.
Answer: Osmosis is the net movement of water from a region of higher water concentration to lower concentration across a semipermeable membrane.
Answer: Small nonpolar molecules diffuse easily through the lipid bilayer down their concentration gradient.
Answer: In a hypotonic solution water enters the cell, making it swollen and turgid.
Answer: In a hypertonic solution the cell loses water and the cytoplasm shrinks away from the wall, causing plasmolysis.
Answer: The plasma membrane consists mainly of a phospholipid bilayer with proteins and some carbohydrates.