Introduction

Chapter 1. Chapter 3: Cell Function and Structure

Interactive Study Guide
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Polaris Trail

Welcome to the Interactive Study Guide for Chapter 3: Cell Function and Structure! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Wonder Drug:

How a chance discovery in a London laboratory revolutionized medicine

DRIVING QUESTIONS

  • What structural features are shared by all cells and what are the key differences between prokaryotic and eukaryotic cells?
  • How do solutes and water cross membranes and what determines the direction of movement of solutes and water in different situations?
  • How do antibiotics target bacteria and in what situations is antibiotic therapy indicated?
  • What are some key eukaryotic organelles and their functions?

Driving Question 1

What structural features are shared by all cells and what are the key differences between prokaryotic and eukaryotic cells?

Why should you care?

While bacteria are prokaryotic cells, other organisms such as fungi, plants, and humans are made up of eukaryotic cells. Why is this important? Prokaryotic organisms, like bacteria, are everywhere on earth, including on and inside you. Although some bacteria cause diseases, many are essential to the lives of many other kinds of organisms, including humans. Understanding the differences between eukaryotic cells and prokaryotic cells (such as the presence or absence of a nucleus and other organelles,or the different structure of ribosomes in the two groups) will help you understand the broad world around you.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain the basic principles of the cell theory.
  2. Compare and contrast the differences and similarities between prokaryotic and eukaryotic cells.

Infographic Focus:

The infographics most pertinent to the Driving Question are 3.2, 3.3, 3.4 and 3.5.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
The organelle in eukaryotic cells that contains the genetic material.
Cells that lack internal membrane-bound organelles.
A phospholipid bilayer with embedded proteins that forms the boundary of all cells.
A chemical that can slow or stop the growth of bacteria; many antibiotics are produced by living organisms.
A complex of RNA and proteins that carries out protein synthesis in all cells.
A rigid structure enclosing the cell membrane of some cells that helps the cell maintain its shape.
The concept that all living organisms are made of cells and that cells are formed by the reproduction of existing cells.
The membrane-bound compartments of eukaryotic cells that carry out specific functions.
The gelatinous, aqueous interior of all cells.
Cells that contain membrane-bound organelles, including a central nucleus.
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Explain the basic principles of the cell theory.

1.

Describe the tenets of the cell theory.
The cell theory states that all living organisms are made up of cells and that new cells arise from previous cells.

Compare and contrast the differences and similarities between prokaryotic and eukaryotic cells.

3.

Fill in the table below with “Present” or “Absent” to describe if the organelle or structure is present in prokaryotic and eukaryotic cells. Note that most prokaryotic and some eukaryotic cells have a cell wall.

Prokaryotic Cells Eukaryotic Cells
Cell membrane made of a phospholipid bilayer.
Ribosomes
Membrane-bound organelles
Genetic material contained in a nucleus
Cytoplasm
Table
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Review Questions

5.

According to the cell theory, bacteria ____________ .

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Driving Question 2

How do solutes and water cross membranes and what determines the direction of movement of solutes and water in different situations?

Why should you care?

The movement of substances in and out of cells through their cell membranes and into their cytoplasm is essential to their functioning and therefore their life.Water movement across the cell membrane from an area of lower solute concentration to an area of higher solute concentration is called osmosis. Solute movement down their concentration gradient (from an area of high concentration to an area of low concentration) is called diffusion: simple diffusion happens when solutes can move right across the phospholipids of the membrane, and facilitated diffusion happens through the assistance of transport proteins found in the membrane. Transport proteins are also used to move solutes against their concentration gradient (from areas of low to areas of high concentration). This is called active transport.

This movement of water and solutes across cell membranes is important because it is necessary for cells to maintain water balance and obtain nutrients to stay alive. When you digest food, the nutrients have to cross membranes; when you move a muscle, ions and signal molecules have to cross cell membranes; when you take medicine, like antibiotics, the medicine may need to cross cell membranes in order to reach its target and be effective.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain how phospholipids form the basic structure of the cell membrane.
  2. Predict the net direction of water movement across the membrane of cells found in different environments.
  3. Compare and contrast simple diffusion, facilitated diffusion, and active transport.

Infographic Focus:

The infographics most pertinent to the Driving Question are 3.4, 3.5, 3.6 and 3.7.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
Describes a solution surrounding a cell that has a higher concentration of solutes than the cell.
Proteins involved in the movement of molecules across the cell membrane.
The energy-requiring process by which solutes are pumped from an area of lower concentration to an area of higher concentration with the help of transport proteins.
Describes a solution surrounding a cell that has a lower concentration of solutes than inside the cell.
The process by which large or hydrophilic solutes move across a membrane from an area of higher concentration to an area of lower concentration with the help of transport proteins’ facilitated diffusion does not require an input of energy.
The diffusion of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.
Describes a solution surrounding a cell that has the same solute concentration as the cell.
The movement of small, hydrophobic molecules across a membrane from an area of higher concentration to an area of lower concentration; simple diffusion does not require an input of energy.
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Explain how phospholipids form the basic structure of the cell membrane.

7.

The fatty acids that make up the ‘tails’ of a phospholipid are called ‘fatty’ because they have many properties of fats and oils. How does this fact fit in with the structure of the cell membrane? (Refer to Chapter 2 if necessary).
Since the tails of the phospholipids making up the lipid bilayer of the cell membrane are fatty in nature, and thus hydrophobic, they would rather interact with each other than the aqueous solutions of the extracellular matrix and cytoplasm of the cell. This results in a double layer of phospholipids with the head of the phospholipids from each layer interacting with the aqueous solutions and the tails interacting with each other to form a barrier.

Predict the net direction of water movement across the membrane of cells found in different environments.

9.

In which direction (into or out of the cell) will there be a net movement of water when the cell is placed:

In an isotonic solution?

In an hypertonic solution?

In an hypotonic solution?
Isotonic = equal solute concentration in and out of the cell, so there is no net movement of water as the water would flow freely into and out of the cell
Hypertonic = higher solute concentration outside the cell, so water would move towards the higher solute concentration which, in a hypertonic case, is outside the cell.
Hypotonic = higher solute concentration inside the cell, so water would move inside the cell towards the higher solute concentration.

Compare and contrast simple diffusion, facilitated diffusion, and active transport.

11.

Fill in the chart below; although the questions could be answered with yes or no, you should also consider noting extra information in the space to clarify the answer and help you remember it:

Simple Diffusion Facilitated Diffusion Active transport
Requires a special membrane protein?

Fill in:

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May work with relatively large molecules?

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Involves substances moving from high to low concentration?

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Involves substances moving from low to high concentration?

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Requires additional energy from the cell to occur?

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Charged and hydrophilic molecules may move across the membrane this way?

Fill in:

Fill in:

Fill in:
Table
Simple Diffusion Facilitated Diffusion Active transport
Requires a special membrane protein? No Yes, but no energy required Yes, but energy required
May work with relatively large molecules? No, cannot fit through the cell membrane Yes, but no energy required Yes, but energy required
Involves substances moving from high to low concentration? Yes Yes No, which is why energy is required to pump the molecules against their concentration gradient
Involves substances moving from low to high concentration? No No Yes, which is why energy is required to pump the molecules against their concentration gradient
Requires additional energy from the cell to occur? No No Yes
Charged and hydrophilic molecules may move across the membrane this way? No, only uncharged molecules can cross both the hydrophilic and hydrophobic areas of the cell membrane Yes, no energy is required Yes, energy is required
Table

Review Questions

14.

Consider a bacterium living in a solution with low sugar concentration. It has already accumulated more sugar molecules in its cytoplasm than are in the surrounding solution. How may it continue to uptake more sugar?

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Driving Question 3

How do antibiotics target bacteria and in what situations is antibiotic therapy indicated?

Why should you care?

In this chapter, we will explore what a cell is and does through the story of the discovery of penicillin, the first antibiotic drug. The discovery of antibiotics was the biggest medical breakthrough of 20th century medicine. Bacterial infections that were once incurable, fatal, or debilitating could be cleared up in a few days. It is difficult to imagine how this changed people's world view, but now that we have an increasing number of bacterial infections that cannot be cured easily with antibiotics, we may soon be back to a time of worrying if minor wounds could lead to life-threatening infections.

Part of the reason that antibiotics are beginning to lose their efficacy against some bacteria is that the general public has not understood how they work and therefore used them improperly. Most of the simple respiratory infections you would call a 'cold' are caused by viruses, which are not cells, and therefore not alive. Antibiotics, as their name implies ('anti': against, and 'biotic': living), are effective only against living organisms, specifically bacteria. Furthermore, when antibiotics are used to treat viruses, a side effect can be killing off all but the most resistant bacteria. By learning the parts of cells and how they work, you will be better able to make informed decisions about using antibiotics.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain how antibiotics kill bacteria without harming their host.
  2. Identify medical situations where antibiotics are effective.
  3. Explain why the overuse and misuse of antibiotics is a threat to the future of human health.

Infographic Focus:

The infographics most pertinent to the Driving Question are 3.1, 3.4, 3.5 and 3.6.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
Refers to bacteria with a cell wall that includes a thick layer of peptidoglycan that retains the Gram stain.
Refers to bacteria with a cell wall that includes a thin layer of peptidoglycan surrounded by an outer lipid membrane that does not retain the Gram stain.
The macromolecule found in all bacterial cell walls that confers rigidity.
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Explain how antibiotics kill bacteria without harming their host.

16.

What is the function of ribosomes in all cells?
Ribosomes are a major player in protein synthesis. Basically, they ‘read’ messenger RNAs that contain ‘codes’ for specific proteins, and translate those codes into proteins.

Identify medical situations where antibiotics are effective.

You have a friend with a cold. He went to his doctor and was annoyed that his doctor would not prescribe him an antibiotic to get rid of his cold. You decide you need to set the record straight.

19.

Does your friend’s doctor think he has a bacterial infection? How do you know?
No, because the doctor did not prescribe your friend antibiotics.

Explain why the overuse and misuse of antibiotics is a threat to the future of human health.

Triclosan is a compound added to many soaps, deodorants, mouthwashes, and other grooming products as an antibacterial agent (in fact it is often hard to find soaps without it). Triclosan also has a medical use as a cleansing agent for antibiotic-resistant skin infections. However, there is evidence that some bacteria are becoming resistant to triclosan. In addition, research has shown that washing hands thoroughly with plain soap (i.e. without triclosan) and water removes or kills as many bacteria as when using a triclosan-containing soap.

22.

How do you think that bacteria can become resistant to triclosan?
Much like most populations of organisms, a population of bacteria living on your hands is made up of individuals that can differ from one another. It is possible that one or a small number of individuals harbor a mutation that allows them to survive and reproduce even in the presence of triclosan. Over time, these resistant bacteria will make up the majority of the population resulting in triclosan resistant bacteria.

Review Questions

24.

An new antibiotic targets the phospholipid head of the cell membrane’s lipid bilayer. Would this anitbioitc be useful as an anti-bacterial therapy?

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Driving Question 4

What are some key eukaryotic organelles and their functions?

Why should you care?

Different organelles present in your cells help you do things like obtain energy from food (mitochondria), move your muscles (cytoskeleton), grow hair (rough endoplasmic reticulum and the Golgi apparatus), produce hormones (smooth endoplasmic reticulum), and decode your genes (ribosomes). In plant cells, organelles called chloroplasts allow the cells to carry out photosynthesis. The cooperation of all the organelles within eukaryotic cells, such as the ones that make up your body, is close to miraculous. You should care about organelles because they explain part of the fascinating story of how you function.

Some organelles are found in all cells, but others are specific to certain organisms. You should care about what the different organelles do, because the ones in your cells allow them to function, but you should also care about how organelles differ between organisms like animals and plants. This will help you appreciate how you work, how plants work, and how plants and animals are both very different from prokaryotes like bacteria. The latter point is important if you want to understand better how antibiotics work to combat a bacterial infection without harming the patient.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Describe the organelles found in most eukaryotic cells.
  2. Describe endosymbiosis and what it means in terms of antibiotic specificity.

Infographic Focus:

The infographics most pertinent to the Driving Question are 3.8 and Up Close: Eukaryotic Organelles.

Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
An organelle in plant and algal cells that is the site of photosynthesis.
The scientific theory that free-living prokaryotic cells engulfed other free-living prokaryotic cells billions of years ago, forming eukaryotic organelles such as mitochondria and chloroplasts.
Membrane-bound organelles responsible for important energy-conversion reactions in eukaryotes.
The double membrane surrounding the nucleus of a eukaryotic cell.
A network of protein fibers in eukaryotic cells that provides structure and facilitates cell movement.
An organelle in eukaryotic cells filled with enzymes that can degrade worn-out cellular structures.
An organelle made up of stacked membrane-enclosed discs that packages proteins and prepares them for transport.
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Describe the organelles found in most eukaryotic cells.

26.

Match the organelle with the proper description:

Membrane-bound site of lipid production
Membrane-bound site of protein processing, packaging, and distribution
Network of protein fibers that helps other organelles move around cytoplasm
Translates genetic material into proteins
Contains genetic material
Converts light energy into chemical energy
Converts energy in food to another form of energy that the cell can use
Membrane-bound site of protein production
Breaks down molecules and parts of the cell for re-use
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Describe endosymbiosis and what it means in terms of antibiotic specificity.

28.

In your own words, describe the theory of endosymbiosis.
The theory of endosymbiosis states that certain organelles of eukaryotic cells, the mitochondria in animal cells and the chloroplasts in plant cells, arose from a prokaryotic cell that was engulfed by a eukaryotic cell billions of years ago.

Review Questions

30.

Which of the following would not be found in a eukaryotic cell:

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B.
C.
D.
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