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7 Cards in this Set

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  • Back
distinguish between
diffusion and osmosis
Diffusion – molecules move from higher to lower concentration (down their concentration gradient)

Osmosis is the diffusion of water across a differentially permeable membrane.
distinguish between
endocytosis and exocytosis
exocytosis – In exocytosis, a vesicle often formed by Golgi apparatus fuses with the plasma membrane as secretion occurs; method by which insulin leaves insulin-secreting cells.

endocytosis - During endocytosis, cells take in substances by vesicle formation as plasma membrane pinches off.
distinguish between
active transport and
passive transport
Passive transport – moves molecules across membrane without expenditure of energy by cell. (includes diffusion and facilitated transport).

Active transport – uses energy (ATP) to move molecules across membrane. (includes active transport, exocytosis, endocytosis, and pinocytosis.
4:3 What is passive diffusion? How does it take place?
A few substances can move across membranes without any assistance. These chemicals always move from an area of high concentration to an area of low concentration. This is called passive diffusion and substances can move only with the concentration gradient.
The four main kinds of passive transport are diffusion, facilitated diffusion, filtration and osmosis.
4:1 Explain what would happen to a freshwater unicellular organism if it was suddenly released in a saltwater environment. Use the terms isotonic, hypotonic and hypertonic in your answer.
The cell will shrink because the organism is hypotonic (fewer solutes) compared to the saltwater that is hypertonic (greater solutes).
The cell contracts and crenation occurs forming abnormal notches around the cell due to loss of water through osmosis.
The cytoplasm decreases in volume. This process would continue until an isotonic state is reached.
4:1 cont. What would happen if a marine organism were placed in freshwater?
Since water molecules diffuse from higher to lower concentration, water would diffuse into the cells of the marine organism.
Cells would swell up.
In order to reach an isotonic state the organism will take on water.
The marine organism swells up, and will burst and die when placed in fresh water.
4:4 How can substances move across a membrane against a concentration gradient? What are the processes that can accomplish this movement? Give an example of when this might need to take place.
Substances move across membrane through active transport.
low concentration to high concentration.