PRE TEST

THE WORK OF CELLS

1 Living is work, and all forms of life require an ongoing supply of energy to perform the work of life. Energy is the capacity to do work, where work is defined as the ability to move matter or to rearrange a collection of matter. The cell is the basic unit of life. The work of life depends on the ability of cells to use energy to perform their many tasks. Energy enables cells to cause specific changes that are necessary for life. Many cells move or change their shapes. They grow and reproduce. Cells organize small organic molecules into proteins and DNA.Cells pump substances across membranes. They export products that are used in other parts of the organism. Cells must work just to maintain their own complex structure. The changes caused by cellular activities involve the transformation of energy from one type to another.Different kinds of change define the kinds of work performed by cells, which fall into three main categories: mechanical, synthetic, and concentration.

2 Mechanical work involves a physical change in the position of a cell or some part of the cell. One example is the movement of a cell in relation to its environment. Such movement requires the presence of some sort of appendage , such as the long, thread–like structure called a flagellum . Many bacteria have such appendages, and they wag these tail–like structures to push themselves through the environment. Sometimes, however, the environment is moved past a cell. This occurs with the beating of cilia, hair–like cellular structures that move rhythmically. The human trachea is lined with cilia that beat upward to sweep inhaled particles back to the mouth or nose, thus protecting the lungs. An example of mechanical work that involves not just a single cell but a large number of cells is muscle contraction. Muscle tissue is specialized for mechanical work. It consists of bundles of muscle fibers, each of which is an individual muscle cell containing numerous myofibrils, the contractile elements of the cell.Still another example of mechanical work occurs within a cell, and this is the movement of chromosomes during cell division. Matching pairs of chromosomes move apart and are propelled along the surface of the nucleus by the lengthening spindle fibers between them.The chromosomes eventually travel to opposite poles of the cell.

3 Synthetic work involves changes in chemical bonds. A cell is a miniature chemical industry, where thousands of reactions occur within a microscopic space. Almost every cell is continuously engaged in the important work of biosynthesis, which causes the formation of new bonds and the generation of new molecules. This activity can be observed in a population of growing cells, where the cells increase in size, number, or both, as additional molecules are being synthesized. Most structural components of a cell are in a state of constant turnover .The molecules that compose the structure are continuously being degraded and replaced.Almost all of the energy that cells need for biosynthetic work goes toward making energy–rich organic molecules from simpler starting materials, such as proteins from amino acids,and into activating these molecules for incorporation into larger molecules.

4 Concentration work is the transport of substances across a membrane or boundary when the substances are pumped against the direction of spontaneous movement. The purpose of concentration work is either to accumulate substances within a cell or to remove by–products of cellular activity that are not needed or might be toxic if allowed to remain. The transport of substances enables the cell to maintain internal concentrations of small molecules that differ from concentrations in the environment. For example, compared to its surroundings, an animal cell has a much higher concentration of potassium molecules and a much lower concentration of sodium molecules. The cell’s plasma membrane helps maintain these differences by pumping sodium out of the cell and potassium into the cell. A specialized case of concentration work is electrical work, which involves the movement of ions across a membrane against an electrical gradient. Every membrane has some electrical potential that is generated through concentration. Electrical work is important in the mechanism whereby impulses are conducted in nerve and muscle cells.

Glossary:

appendage: a part attached to an organism, such as an arm, leg, or tail

trachea: the tube that carries air from the throat to the lungs; windpipe

1. According to paragraph 1, what is essential to the work of life?

A The discovery that the cell is the unit of life

B The use of energy to cause cellular changes

C The availability of water

D The ability of organisms to adapt to their environment

2. In paragraph 1, the author makes the point that

A cells require energy from outside sources

B a cell’s ability to work decreases with age

C all life forms can evolve from simple to complex

D energy changes form during cellular activites

3. Paragraph 1 supports which of the following statements?

A Life is characterized by various kinds of change.

B Energy requirements impose a limit on the size of a cell.

C The work of cells is supported by energy from sunlight.

D Cellular respiration drives the energy use of a cell.

4. The author mentions a flagellum in paragraph 2 in order to

A illustrate how a cell can move through its environment

B compare appendages with other parts of the cell

C identify the most interesting cellular structure of bacteria

D describe the diversity of structures found in cells

5. The word propelled in paragraph 2 is closest in meaning to

A hidden

B pushed

C caught

D absorbed

6. All of the following are given as examples of mechanical work EXCEPT

A the beating of cilia in the human trachea

B the contraction of muscle tissue

C the organization of small molecules into proteins

D the activity of chromosomes during cell division

7. What is the main purpose of paragraph 3?

A To define the concept of work in cell biology

B To compare synthetic work and biosynthesis

C To describe the structural components of a cell

D To explain the function of synthetic work

8. Which sentence below best expresses the essential information in the highlighted sentence in paragraph 3? Incorrect choices change the meaning in important ways or leave out essential information.

A Observation of cell growth is an easy way to learn about the structure of molecules.

B Cell activity during synthetic work involves an increase in the rate of cell growth and reproduction.

C Biosynthesis occurs when new molecules are generated as cells grow in size, number,or both.

D A population of growing cells needs a large input of energy so that new molecules can be synthesized.

9. The word turnover in paragraph 3 is closest in meaning to

A disturbance

B purification

C stress

D replacement

10. By stating in paragraph 4 that substances are pumped against the direction of spontaneous movement , the author implies that

A moving the substances requires the use of force

B this work creates molecules of higher structural complexity

C the substances move in a continuously changing direction

D cell division is necessary to perform concentration work

11. What can be inferred about concentration work from paragraph 4?

A Concentration work is a specialized case of mechanical work.

B Animal cells synthesize new molecules during concentration work.

C Some concentration work generates electrical impulses.

D Concentration work involves a low rate of energy consumption.

12. Look at the four squares, A , B , C ,and D , which indicate where the following sentence could be added to the passage. Where would the sentence best fit?

The result is not just a change in concentration but also the establishment of an electrical potential across the membrane.

Concentration work is the transport of substances across a membrane or boundary when the substances are pumped against the direction of spontaneous movement. The purpose of concentration work is either to accumulate substances within a cell or to remove by–products of cellular activity that are not needed or might be toxic if allowed to remain. A The transport of substances enables the cell to maintain internal concentrations of small molecules that differ from concentrations in the environment. B For example, compared to its surroundings, an animal cell has a much higher concentration of potassium molecules and a much lower concentration of sodium molecules. The cell’s plasma membrane helps maintain these differences by pumping sodium out of the cell and potassium into the cell. C A specialized case of concentration work is electrical work, which involves the movement of ions across a membrane against an electrical gradient. D Every membrane has some electrical potential that is generated through concentration. Electrical work is important in the mechanism whereby impulses are conducted in nerve and muscle cells.

13. An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Cells use energy to generate the specific changes that define the different kinds of work they do.

Answer Choices

A Cells perform mechanical work, which causes the movement of cells in relation to their environment or the movement of components within cells.

B Mechanical work can involve a single cell or a large number of cells, such as muscle tissue, which contains bundles of fiber–like cells.

C Most cells engage in synthetic work, the formation of new chemical bonds and the generation of new molecules.

D Animal cells perform concentration work when they pump potassium and sodium molecules across the plasma membrane.

E Cells perform electrical work to maintain the electrical potential across cell membranes, even when the organism is at rest.

F Concentration work involves accumulating substances and moving substances across a membrane or against an electrical gradient.

Answers to the Reading questions are on page 631.

Use your Pre–Test results to identify the skills and question types that you need to practice.

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QUESTIONS 1—5

1. What is the conversation mainly about?

A Arrangements for a guest speaker next week

B Material to review for an upcoming test

C The student’s vacation in the mountains

D A report that the student is preparing

2. Listen again to part of the conversation.Then answer the question.

Why does the professor say thi

A To imply that the student does not need advice

B To inform the student that he has only a little time to talk

C To invite the student to come to a meeting

D To suggest that the student’s presentation will be too long

3. What types of data does the student plan to use? Click on 2 answers.

A A summary of volcanic eruptions

B A photograph of an observatory

C A recorded interview with a geologist

D A series of pictures of a mountain

4. What is the student’s opinion of the photographs?

A They are the best photographs she has ever taken.

B They are old and poor in quality, but will have to suffice.

C They show the mountain’s changes very clearly.

D They would be more interesting if they were in color.

5. Listen again to part of the conversation. Then answer the question.

What does the professor mean when he says thi

A The audience is very likely to ask about the meaning of the bulge.

B Some questions may require a long time to answer completely.

C The student should prepare a list of questions in advance.

D There will be questions about the volcano on the next test.

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QUESTIONS 6—11

6. What is the lecture mainly about?

A How nature’s color signals can help us understand climate change

B What color pigments in leaves reveal about the health of trees

C Technology for collecting data about environmental conditions

D The relationship between seasonal changes and animal behavior

7. Why does the professor say thi

ATo encourage students to observe animals

B To predict effects of climate change

C To illustrate the concept of phenology

D To describe nature in an artistic manner

8. Listen again to part of the discussion. Then answer the question.

Why does the professor say thi

A To state that the class will participate in a research study

B To signal that he will eventually address the student’s question

C To introduce a digression to a personal story

D To express annoyance at the interruption of his explanation

9. Listen again to part of the discussion. Then answer the question.

What does the professor imply when he says thi

A The textbook has many photographs of color pigments.

B The students should take notes on what he is about to say.

C The textbook contains information that is also available online.

D The students should read the explanations in the textbook.

10. What does the professor say about a method of data collection that uses a camera?

A The camera obtains better photographs than those in the textbook.

B The camera collects color data about the forest for an online database.

C The students are required to use a camera to assist in their observations.

D The camera does not provide evidence of changes in animal behavior.

11. According to the professor, how will color data about forests be useful to researchers?

A The data will enable development of better models for predicting effects of climate change.

B The data will either support or disprove the position that phenology is a reliable science.

C The data will assist in the creation and manufacture of synthetic color pigments.

D The data will answer questions about the relationship of weather patterns and psychology.

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QUESTIONS 12—17

12. What is the main idea of the talk?

A Managers must combine information and resources to produce and market a product.

B Farm management is a complex job with responsibility for all of a farm’s resources.

C Many farm managers hire a farm operator to perform the daily tasks of running the farm.

D Farming is a business that involves risk,uncertainty, and constantly changing conditions.

13. Which of the following best describes the organization of the talk?

A A comparison of farm managers to other types of managers

B A description of a farm’s physical,financial, and human resources

C A summary of the process for preparing a business plan

D A list of the requirements and responsibilities of farm management

14. According to the professor, in which subjects must a farm manager be knowledgeable? Click on 3 answers.

A Engineering

B Biological sciences

C History of civilization

D Communication

E Strategic planning

15. Listen again to part of the lecture. Then answer the question.

Why does the professor say thi

A To introduce the topic of preparing a business plan

B To stress that farm managers must understand ecology

C To warn students of the financial risks of farming

D To recommend a specific sequence of business courses

16. According to the professor, what should be included in the business plan for a farm? Click on 2 answers.

A A description of the farm and its goals

B Photographs of the machinery and workers

C Plans for production and marketing

D A strategy for public relations

17. What can be inferred about the students in this class?

A They have little or no experience in resource management.

B They are from families that own farms or other businesses.

C They have previously completed courses in general management.

D They are interested in farm management as a career.

Stop

Answers to the Listening questions are on pages 631–632.

Use your Pre–Test results to identify the skills and question types that you need to practice.

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QUESTION 1

In this question, you will be asked to talk about a familiar topic. After you hear the question, you will have 15 seconds to prepare your response and 45 seconds to speak.

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Stop

Preparation Time–15 seconds

Response Time–45 seconds

QUESTION 2

In this question, you will be asked to give your opinion about a familiar topic. After you hear the question,you will have 15 seconds to prepare your response and 45 seconds to speak.

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Preparation Time–15 seconds

Response Time–45 seconds

QUESTION 3

In this question, you will read a short passage about a campus situation, listen to a conversation, and then speak in response to a question about what you have read and heard. After you hear the question, you have 30 seconds to prepare your response and 60 seconds to speak.

Read the following information from a university website.

Reading Time–45 seconds

NEW BLOCK SCHEDULE

Starting in the fall quarter, students will be able to take classes in an entirely new way.Now they will have the option to take English composition classes linked with subject–area courses in “blocks” as an integrated learning experience. There will be three interest tracks:Society and the Individual, the Natural World, and Business and Leadership. Each track will be offered in multiple blocks of time, giving students more flexibility around their busy schedules. Students can concentrate their classes in mornings or afternoons on four or five days a week, or in mornings and afternoons twice a week.

Now cover the passage and listen to the recording. When you hear the question, begin preparing your response.

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Stop

Preparation Time–30 seconds

Response Time–60 seconds

QUESTION 4

In this question, you will read a short passage, then listen to a lecture on the same topic, and then speak in response to a question about what you have read and heard. After you hear the question, you have 30 seconds to prepare your response and 60 seconds to speak.

Read the following information from a textbook.

Reading Time–45 seconds

PROVERBS

A proverb is an expression that conveys a bit of traditional wisdom that has been passed down from previous generations. The language of a proverb is simple and direct, offering advice on how to live. In most cases, the origin of a proverb is unknown. The images in proverbs usually refer to everyday objects and experiences. A proverb’s effectiveness lies mainly in its simplicity and its memorability. Several linguistic techniques aid our ability to remember proverbs, such as rhythm, rhyme, and parallelism. Another common technique is alliteration, the repetition of the same consonant sound at the beginning of two or more words.

Now cover the passage and listen to the recording. When you hear the question, begin preparing your response.

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Stop

Preparation Time–30 seconds

Response Time–60 seconds

QUESTION 5

In this question, you will listen to a conversation. You will then be asked to talk about the information in the conversation and to give your opinion about the ideas presented. After you hear the question, you have 20 seconds to prepare your response and 60 seconds to speak.

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Preparation Time–20 seconds

Response Time–60 seconds

QUESTION 6

In this question, you will listen to a short lecture. You will then be asked to summarize important information from the lecture. After you hear the question, you have 20 seconds to prepare your response and 60 seconds to speak.

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Stop

Preparation Time–20 seconds

Response Time–60 seconds

Key points for the Speaking questions are on pages 632–633.

Each response earns a score of 1, 2, 3, or 4, with 4 being the highest score.

Use your Pre–Test results to identify the skills and question types that you need to practice.

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QUESTION 1

For this task, you will write a response to a question about a reading passage and a lecture. You may take notes, and you may use your notes to help you write your response. Your response will be scored on the quality of your writing and on how well you connect the points in the lecture with points in the reading. Typically, an effective response will have 150 to 225 words.

Reading Time–3 minutes

Freshwater ecosystems are classified according to water flow. Lotic ecosystems are characterized by water that is moving continually from the earth or over its surface. Springs,brooks, streams, and rivers are lotic ecosystems, and their most important physical factor is water flow. Water flow, or current, is influenced by the amount of water in the stream or river,and this varies with rainfall patterns, snow melt, and other seasonal changes. When the water level of a stream or river increases, its current becomes faster and stronger.

Another characteristic is the ecosystem’s oxygen and nutrient content. Lotic ecosystems typically have high oxygen levels because water flowing over rocks, logs, and other objects causes turbulence that oxygenates the water. The more rapid and turbulent the flow, the more oxygen the water carries through the system.

A third characteristic is the production of organic matter. In lotic ecosystems, most of the production comes from surrounding land habitats and is carried into the stream in runoff from rainfall. Fallen leaves from dense, overhanging vegetation can add substantial amounts of organic matter. This matter enters the stream, where it becomes a food source for other organisms. The nutrient content of a lotic ecosystem is largely determined by the terrain and vegetation through which the stream or river flows. Because most lotic ecosystems are relatively shallow and have long shorelines, terrestrial production can usually supply the energy needs of the ecosystem. Fast-flowing streams and rivers do not support large communities of plankton because these microscopic organisms are washed away by the flow of water.

Now listen to the recording. When you hear the question, begin your response. You may look at the reading passage during the writing time.

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Writing Time–20 minutes

QUESTION 2

For this task, you will write an essay in response to a question that asks you to state and support your opinion on a topic. Your essay will be scored on the quality of your writing, including how well you organize and develop your ideas and how well you use language to express your ideas. Typically, an effective essay will have a minimum of 300 words.

Read the question below and make any notes that will help you plan your response. Then begin typing your essay.

Writing Time–30 minutes

Key points for Writing Question 1 are on page 633.

Responses to Writing Question 2 will vary.

Each response earns a score of 1, 2, 3, 4 or 5, with 5 being the highest score.

Use your Pre–Test results to identify the skills and question types that you need to practice. 8YszGQhY0sJSbmBaqVH9/nYCWSHilh1Ca2uiXKfIdRnZceUQwFY55VhSO5yfaVqA