9 terms

7th Grade Science: Cells - Section 1-4 Diffusion and Limits on Cell Size

Sci7 - Chapter 2.3 What a cell has to do to survive
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diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
osmosis
Diffusion of water (or another solvent) through a semi-permeable membrane from an area with many water molecules into an area with fewer water molecules.
passive transport
Movement of substances through a cell membrane without the use of cellular energy; includes diffusion, osmosis, and facilitated diffusion.
active transport
The movement of materials through a cell membrane using energy (usually against their "concentration gradient" - the opposite of diffusion)
What are the two main reasons cells don't grow indefinitely
1. Diffusion of molecules is too slow for large volumes
2. DNA limits cells size
How big are most cells?
Most cells are between 2μm and 200μm
What do cells do before they get too big?
They divide.
What is an Amoeba?
A large single celled organisms.
What does the folded cell membrane of an amoeba do?
creates a large surface area for diffusion to occur effectively
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