Download STUDY GUIDE: CHAPTER 4

CHAPTER 4 Learning Targets
The Cell in Action (LS 2a, LS 3b, LS 6b)
NAME ________KEY__________________
DATE ___________________ Block _____
You should be able to:
(Chapter 4 Section 1 and 2)
1. __________ Describe why diffusion occurs.
Diffusion occurs because molecules are trying to spread out as far as possible (and
eventually reaching equilibrium.)
2. __________ Explain why energy is not required for diffusion.
Energy is not required for diffusion because molecules are constantly moving.
3. __________ Identify the direction of diffusion if given two different solutions.
For example: What direction will the water move in the following picture (assume
the membrane is selectively permeable to water, x)?
x x x x x x x x x x x x
x x x x x x x
x o x o
x x x x x x x o x o x o
x x x x x x x x o x o x
x x x x x x x o x o x o
4.
5.
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7.
8.
9.
Water molecules can move through the semi-permeable membrane and so they move
from their area of high concentration (left side) to their area of lower
concentration (right side)
__________ Explain how a semipermeable membrane works.
A semi-permeable membrane controls what enters and leaves by size of the
molecule. Only the smallest molecules can enter through the phospholipids. Larger
molecules may have to enter through a protein doorway or by endocytosis.
__________ Explain the effect of diffusion on size of cell.
If water diffuses into a cell, the cell will get larger. If water diffuses out of a cell,
the cell will get smaller.
__________ Identify which molecules can diffuse through the phospholipids.
Water and oxygen
__________ Identify which molecules can diffuse through protein doorways.
Sugar and amino acids
__________ Describe passive transport. Does it use energy?
It is the movement of molecules from areas of high concentration to areas of low
concentration. It does not use energy.
__________ Describe active transport. Does it use energy?
It is the movement of molecules from areas of low concentration to areas of high
concentration. It does use energy.
10. __________ Describe endocytosis and exocytosis.
Endocytosis is bringing large molecules into the cell by the cell membrane
surrounding the molecules and folding inward into a vesicle that breaks off from the
cell membrane inside the cell.
Exocytosis is removing large molecules from the cell by a vesicle merging with the
cell membrane and pouring the large molecule outside the cell.
11. __________ Identify whether endocytosis and exocytosis require energy.
Endocytosis and exocytosis both require energy.
12. __________ Describe what occurred in the egg diffusion lab and why it occurred.
Day 1 to Day 2 egg got much larger because vinegar/water diffused from the
vinegar (high concentration of water) into the egg (low concentration of water).
Day 2 to Day 3 egg got much smaller because vinegar/water diffused from the egg
(high concentration of water) into corn syrup (low concentration of water).