The Cell in Its Environment – Flashcards
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What structure protects the contents of cells from the outside environment?
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Cell membrane
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What are some materials that pass through the cell membrane?
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Oxygen, food molecules and waste products.
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What are the 3 methods by which substances move into and out of a cell?
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Diffusion
Osmosis
Active transport
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What is the main method by which small molecules move across the cell membrane?
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Diffusion
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What is the concentration of a substance?
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The amount of the substance in a given volume.
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How is the concentration of a substance expressed?
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As a ratio....amount of substance/volume
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What causes diffusion?
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Molecules are constantly moving, and they bump into each other when there are more molecules in a particular area. Over time, these molecules will spread out evenly throughout the area.
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What causes molecules to push away from one another?
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Collisions.
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What happens if the concentration of oxygen molecules outside the cell is lower than that inside the cell?
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Diffusion.....the oxygen molecules will move inside the cell until the concentration is equal inside and outside.
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Why do many cellular processes depend on osmosis?
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Cells cannot function properly without adequate water, so many cellular processes depend on osmosis.
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If a red blood cell is floating in water that contains a large amount of salt, is the concentration of water molecules greater inside or outside the cell?
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There is a greater concentration of water molecules inside the cell.....because the salt takes up space in the salt water.
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What happens to the shape of a red blood cell that is in salt water?
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It shrinks....water moves out of the cell by osmosis since the concentration of water molecules outside the cell is less than that inside the cell.
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How is osmosis related to diffusion?
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In osmosis, water molecules move by diffusion from an area where they are highly concentrated through the cell membrane to an area where they are less concentrated.
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What happens to the shape of a red blood cell that is floating in water that contains very little salt?
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It swells, because water moves into the cell because the concentration of water molecules is greater outside the cell than inside.
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In a red blood cell floating in water containing a small amount of salt, is there a higher concentration of water molecules inside the cell or outside the cell?
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The concentration of water molecules outside the cell is greater than inside the cell. There is more salt inside the cell than outside the cell.
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What if a cell needs to take in a substance that is present in a higher concentration inside the cell than outside?
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The cell would have to move the molecules in the opposite direction than they naturally move by diffusion. They must have energy to do this....active transport.
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What type of transport requires the cell to use its own energy?
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Active transport.
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What are 2 methods that cells have to move materials by active transport?
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Transport proteins.
Transport by engulfing.
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How do transport proteins work?
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They "pick up" molecules outside the cell and carry them in, using energy. They can also transport molecules from inside the cell to the outside.
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What are some substances that are carried into and out of cells by transport proteins?
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Calcium
Potassium
Sodium
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Where are transport proteins located?
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In the cell membrane.
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Once a particle is engulfed and the cell membrane wraps around it, what is formed within the cell?
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A vacuole.
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Is transport by engulfing active or passive transport?
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Active....it requires energy.
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What prevents cells from growing very large?
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As cells get bigger, more of the cytoplasm is located farther from the cell membrane. Then it takes longer for a molecule to move in to its destination in the cell, or for wastes to move out...it could not function as well.
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How is a molecule carried to its destination once it enters a cell?
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By a stream of moving cytoplasm....like the currents in the ocean moving a raft.
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What happens when you drop a sugar cube into a mug of hot tea?
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The sugar dissolves in the heat. The sugar molecules then diffuse throughout the tea to sweeten the whole cup equally.
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Why do transport proteins require energy to function in active transport?
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They need energy to move molecules from lower to higher concentration (opposite to the movement of diffusion).
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What is the concentration of a solution that contains 60 g of sugar in 3 L of water (in grams per liter)?
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20 g/L
