Chapter 1. Chapter 3: Cell Function and Structure

1.1 Introduction

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.

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?

1.2 Driving Question 1:

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.

1.3 Driving Question 2:

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.

1.4 Driving Question 3:

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 20^th 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.

1.5 Driving Question 4:

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.