HOW
THINGS GET INTO THE CELL
In this
assignment you will learn how things get into and out of cells. The cell
membrane plays an important role in allowing nutrients to enter the cell, and
wastes to exit the cell. To understand this process we must learn about cell
membranes, diffusion and osmosis, facilitated transport, active transport,
endocytosis and exocytosis. Chapter 4 of the text covers these topics, and the
following activities will help you to better understand these processes
Review of
the Fluid Mosaic Model of the Cell Membrane
1. Be able
to identify the details of the diagram on page 68:
2. Why is
the term, fluid mosaic an appropriate name for the cell membrane model?
3. In point
form, outline the main points you would use to describe the fluid mosaic model
of the cell membrane.
Cell
Membrane Permeability
The cell
membrane controls what enters and leaves the cell, and acts as a selective
filter for products.
1.
Distinguish between the following types of cell membranes:
a. Impermeable
b. Permeable
c
Selectively permeable
Methods
of Getting into Cells
1. List
three ways in which things can get into cells.
Diffusion
1. Define
diffusion.
2. Describe
a specific example of diffusion.
3. Explain
how the following factors affect the rate of diffusion:
a.
temperature
b. size of
molecules
c.
concentration of the gradient
Osmosis
1. Define
osmosis.
2. How does
osmosis differ from diffusion?
3. Define
and give a specific example of:
a. osmotic
pressure
b. turgor
pressure
c.
hydrostatic pressure
d. tonicity
4. Define
and give an example of the following types of solutions:
a. isotonic
b. hypotonic
c.
hypertonic
5. Figure
4.7 illustrates animal and plant cells placed in different solutions of salt.
Describe the appearance of each type of cell in each environment (isotonic,
hypertonic, or hypotonic) and why it appears that way.
Isotonic
Hypertonic
hypotonic
6. What
happens when a cell is crenated?
7. Define
cell lysis.
8. An __________
solution is one where the concentration is equal on both sides of the membrane.
When placed in this solution the cell will ___________. A ___________ solution
is a solution that has a greater solute concentration outside the cell than
inside. When placed in this type of solution the cell will __________ . A
__________ solution is one in which the solute concentration outside the cell
is greater than inside the cell. When placed in this solution the cell will
__________ .
Facilitated
Transport
1. Define
the term facilitated transport.
2. What
types of molecules move into the cell by facilitated transport?
3. What is
the location of the protein carriers within the cell?
4. Is energy
required during facilitated transport?
5. Describe
the direction of the diffusion gradient in facilitated transport.
6. Fig 4.8
on page 74 illustrates a model of facilitated transport. List the main points
you would use in writing a paragraph on facilitative diffusion.
Active
Transport
1. Define
the term active transport.
2. Look at
Figure 4.9 illustrating active transport and explain why energy from ATP is
required.
3. Describe
how the protein carrier operates in active transport.
4. What is
the direction of flow in the concentration gradient during active transport?
5. The most
well-documented example of active transport is the sodiumpotassium pump. List
the main points you would use to explain the sodium potassium pump.
Endocytosis
and Exocytosis
1. Draw a
diagram illustrating endocytosis and list the main points you would use to
explain endocytosis.
2. Draw a
diagram illustrating exocytosis and list the main points you would use to
explain exocytosis.
3. Explain
the role of the cell membrane during endocytosis and exocytosis.
4. Describe
a specific example of:
a.
Endocytosis
b.
Exocytosis
5. What is
the direction of flow in the gradient during endo and exocytosis?
6. Endo and
exocytosis are considered to be forms of active transport. Explain why.
7. Define and
give an example of (a) pinocytosis, (b) phagocytosis.
Sample
Exam Questions
1. Explain
how the structure of the cell membrane is related to its function.
2. Draw a diagram to show the effect of placing a red blood cell in each of the following solutions: (a) 10%, (b) distilled water, (c) 0.9%. Indicate the flow of water in your diagrams.