The model below shows the sodium-potassium
pump. Use the model and your knowledge of
science to answer questions 1–3.
1.What substance is released from the pump
in step B?
A ATP C sodium ion
B phosphate group D potassium ion2.Which statement about ion concentrations
in this model is correct?
F ATP collects outside the cell.
GK+ions collect inside the cell.
HNa+ions collect inside the cell.
J Na+ions collect outside the cell.
3.What would happen if a cell’s sodium-
potassium pumps did not function properly?
A Water would leave the cell by osmosis.
B The cell would swell and burst.
CSodium ions would diffuse out of the cell.
DThe concentration of potassium ions
would increase inside the cell.CHAPTER 4 Review 89
Critical Thinking
- Evaluating ResultsA gelatin block is pre-
pared with a chemical indicator that turns
pink in the presence of a base. The block is
enclosed in a membrane and placed in a
beaker of a basic solution. After half an
hour, the block begins to turn pink. Explain
why the gelatin turns pink. - Analyzing InformationUse your under-
standing of osmosis and diffusion to
explain why cooking dried pasta in boiling
water makes the pasta soft. - Evaluating ModelsExplain why you
think or do not think the model of diffusion
illustrated in Figure 1in this chapter is a
clear explanation of diffusion. - Applying InformationIdentify the property
of a cell membrane that allows particles to
pass through it. Predict how a cell mem-
brane that allows some types of ions and
molecules through but not others would
affect equilibrium between the cell and the
fluid around it.
Alternative Assessment
- Finding InformationUse library or Internet
resources to investigate problems in trans-
port of molecules across the cell membrane.
Several human diseases, including cystic
fibrosis, hypercholesterolemia, and myasthe-
nia gravis affect the function of specific
transport proteins. Describe the symptoms of
and treatments for the diseases. Summarize
your findings in a written report. - Career ConnectionMolecular Biologist
Research the field of molecular biology, and
write a report on your findings. Your report
should include a job description, the train-
ing required, kinds of employers, growth
prospects in the field, and an average start-
ing salary. If possible, interview a person
who works in this field. - Interactive Tutor Unit 1 Cell Transport and
HomeostasisWrite a report summarizing the
roles of osmosis and diffusion in the preserva-
tion of body organs donated for transplants.
Why must the organs be preserved in special
solutions prior to a transplant? Find out what
kinds of substances these solutions contain.
TAKS Test PrepTAKS Test Prep
9A4B4B9A3D4B4BTest
Pay close attention to questions that contain words
such as not, only, rather, and some.