Table of Contents North Carolina Essential Standards Correlation Chart........ 6 Objectives Chapter 1 Cell Biology................................. 9 Lesson 1 Cell Structure............................... 10 1.1.1, 1.1.2 Lesson 2 Homeostasis and Cell Transport................ 16 1.1.1, 1.2.1, 4.2.2 Lesson 3 The Structure and Function of Macromolecules.... 23 4.1.1 Lesson 4 Enzymes................................... 28 4.1.3 Lesson 5 The Cell Cycle.............................. 34 1.2.2 Lesson 6 Cell Differentiation........................... 38 1.1.3 Lesson 7 Energy in Cells.............................. 42 4.2.1 Chapter 1 Review...................................... 47 Chapter 2 Organisms................................ 53 Lesson 8 Single-Celled Organisms...................... 54 1.1.1, 1.1.2, 1.2.3 Lesson 9 Transport in Organisms....................... 61 2.1.2 Lesson 10 Respiration................................. 68 2.1.2 Lesson 11 Feeding Adaptations......................... 74 2.1.2 Lesson 12 Reproduction............................... 81 2.1.2 Lesson 13 Behavioral Adaptations....................... 88 2.1.2 Chapter 2 Review...................................... 93 Chapter 3 Ecosystems............................... 99 Lesson 14 Energy Flow in Ecosystems................... 100 2.1.1, 4.2.2 Lesson 15 Biogeochemical Cycles...................... 105 2.1.1 Lesson 16 Relationships among Organisms............... 110 2.1.3 Lesson 17 Population Dynamics........................ 116 2.1.3, 2.1.4 Lesson 18 How Humans Affect the Environment........... 122 2.1.1, 2.2.1, 2.2.2 Lesson 19 Conservation.............................. 130 2.2.2 Chapter 3 Review..................................... 135 4
Chapter 1 Lesson 1 Cell Structure Objectives: 1.1.1, 1.1.2 Key Words cell eukaryote organelle prokaryote cytoplasm nucleus nuclear membrane chromosome plasmid plasma membrane ribosome mitochondria cell wall chloroplast vacuole Getting the Idea While living organisms share a few common structures and functions, they exhibit an amazing diversity of sizes, shapes, and features. The same is true of cells, the basic units of structure and function in all organisms. Each cell is a complete system that carries out all the processes necessary for life. All cells, both single-celled organisms and cells that are part of larger organisms, have some features in common. However, cells also have a wide range of specialized structures that aid in their survival. Prokaryotic Cells and Eukaryotic Cells The two basic types of cells are prokaryotic cells and eukaryotic cells. Each kind of cell performs similar functions in the same ways. Both kinds of cells are enclosed by an outer structure called a plasma membrane. Both are filled with cytoplasm and contain structures called ribosomes, in which proteins are synthesized. How then do the two kinds of cells differ? You can see some of the differences in the diagram below. Nucleus Eukaryote Ribosomes Plasma membrane Prokaryote Cell wall Mitochondria Flagellum NOTE: Not to scale Plasmid One obvious difference is that the eukaryotic cell is more complex than the prokaryotic cell. The two kinds of cells have very different internal structures. For example, the eukaryotic cell has a distinct nucleus and other cell structures, called organelles, that are enclosed within membranes. Organisms whose cells have a distinct nucleus and membrane-bound organelles are called eukaryotes. The cells of eukaryotes are larger than prokaryotic cells. A typical eukaryotic cell ranges in size from about 2 to 100 micrometers. By contrast, most prokaryote cells are only 0.5 to 2 micrometers in size. 10
Organelles are cell structures that are specialized for different functions. Each type of organelle has a structure that is suited to its function. You will learn more about how organelle structure is related to function as you read about the different types of organelles. Many eukaryotic organisms consist of large numbers of cells that work together. Plants, animals, protists, and fungi are all eukaryotes. All plants and animals, and some protists and fungi, are multicellular, or made up of many cells. In eukaryotes, the organelles interact to carry out most of the cell s life processes. Notice that the prokaryotic cell does not have a nucleus or membrane-bound organelles. Organisms whose cells lack a nucleus and membrane-bound organelles are prokaryotes. In prokaryotes, most of the processes of life occur in the cytoplasm. The cytoplasm is the thick, semifluid material that is enclosed by the plasma membrane. In eukaryotes, the cytoplasm contains the nucleus and the organelles that carry out most of the cell s life processes. For example, eukaryotes have specialized organelles that release energy. In prokaryotes, the processes that release energy occur in the cytoplasm or the plasma membrane. All prokaryotes are one-celled organisms either bacteria or archaea. The Nucleus The largest structure in most eukaryotic cells is the nucleus. The nucleus directs and controls most cellular activities. It is enclosed by a structure called the nuclear membrane, or nuclear envelope. This membrane controls the passage of materials between the nucleus and the cytoplasm. The nucleus contains deoxyribonucleic acid, or DNA. The DNA molecules control protein production and cell functions. DNA also stores the genetic information that is passed from parent to offspring during reproduction. In eukaryotes, DNA is bundled into structures called chromosomes, which are located in the nucleus. You will read more about DNA and chromosomes in Lessons 5 and 20. Prokaryotic cells lack nuclei, but they do contain DNA. Their DNA is found floating in the cytoplasm. In addition to a large, tangled piece of DNA, many prokaryotes have ring-shaped pieces of DNA called plasmids, which are also suspended in the cytoplasm. Structures Common to Most Eukaryotic Cells The organelles common to most eukaryotic cells are shown in the diagram of the animal cell below. Ribosomes Chromosomes Nucleus Plasma membrane Mitochondria Animal Cell Endoplasmic reticulum Cytoplasm Lysosome Golgi body 11
Plasma Membrane The plasma membrane is a thin, flexible layer that surrounds the cytoplasm. This membrane supports and protects the cell and gives it shape. The plasma membrane is made up of two layers of lipids, in which protein molecules are embedded. Tiny openings in the plasma membrane enable it to control which materials enter and leave the cell, either from the external environment or from other cells of the same organism. The plasma membrane is also called the cell membrane. You will learn more about the role of the plasma membrane in the movement of materials into and out of cells in the next lesson. Ribosomes Structures called ribosomes are scattered throughout the cytoplasm of a cell. Ribosomes make a variety of proteins that are used throughout the cell. Unlike most organelles, ribosomes are not enclosed by membranes. Many ribosomes float freely within the cytoplasm of both prokaryotes and eukaryotes. In eukaryotes, ribosomes may also be attached to the endoplasmic reticulum (ER). The endoplasmic reticulum is a network of membranes and sacs that transports molecules from one part of the cell to another. Mitochondria Mitochondria (singular mitochondrion) are the organelles that carry out cellular respiration. Cellular respiration is the process by which living things obtain energy from food. Mitochondria have folded inner membranes that increase the surface area available for the release of energy. Cells that need a lot of energy, such as muscle cells, have many more mitochondria than cells with lower energy requirements. Other Organelles Two other organelles common to many eukaryotes are the Golgi apparatus (also called Golgi bodies) and lysosomes. The Golgi apparatus is a system of membranes that modifies proteins and lipids according to where they will be used. Lysosomes are small, spherical organelles that break down old organelles and carry out digestion in the cell. Lysosomes are common in the cells of animals and fungi, but they are rare in plant cells. Recall that individual cells carry out all of the functions required for life. These functions include energy production and use, the synthesis and transport of molecules, and the removal of wastes. Cell organelles must interact to carry out all of these functions. For example, the DNA in the nucleus directs the ribosomes to assemble proteins that are used as enzymes in other parts of the cell. Mitochondria use enzymes made by the ribosomes to generate the energy that is used by other organelles. The term cell was first used by Robert Hooke in 1663 to describe what he observed through a microscope. What he saw were cell walls in the bark of a cork tree. The cell walls formed rectangular compartments, or cells. 12 Chapter 1: Cell Biology
Lesson 1: Cell Structure Structures Found in Some Eukaryotic and Prokaryotic Cells The organelles discussed so far are common to most eukaryotic cells. They are found in animals, plants, protists, and fungi. The cells of some eukaryotes, particularly plants, have structures that are not found in other types of eukaryotic cells. Many of these structures are shown in the diagram of the plant cell below. Plant Cell Cytoplasm Mitochondria Vacuole Chloroplast Golgi body Endoplasmic reticulum Ribosomes Nucleus Cell wall Plasma membrane Cell Wall The plant cell shown is surrounded by a cell wall. A cell wall is a rigid structure that surrounds the plasma membrane of some cells, giving them additional protection and support. Cell walls are thicker than plasma membranes but also have openings that enable the cell to control the passage of materials into and out of the cell. The cells of all prokaryotes, fungi, and plants have cell walls. Some protists also have cell walls. The cell walls of different kinds of organisms are composed of different materials. Plant cell walls are made of cellulose, a substance made up of sugars. The cell walls of fungi contain chitin. Chitin is made from sugars modified by the addition of nitrogen. Bacteria have cells walls made up mostly of peptidoglycan. This molecule is made up of sugar and protein. The cell walls of archaea do not contain peptidoglycan. Instead, they are composed of a variety of other molecules. Chloroplasts Plant cells contain chloroplasts. Chloroplasts are organelles that capture the energy of sunlight and use it for photosynthesis. Photosynthesis is a process in which energy from sunlight is used to make sugar from water and carbon dioxide. A green pigment called chlorophyll captures the energy from sunlight. Some protists, including algae, also have chloroplasts. Some bacteria carry out photosynthesis, but they do not have chloroplasts. In these bacteria, chlorophyll is scattered through the cytoplasm. Animals and fungi do not have chloroplasts or carry out photosynthesis. Vacuoles Plant cells have a large central vacuole, an organelle that stores water and other important materials, including salts, proteins, and carbohydrates. In plants, pressure from the liquid-filled vacuole also helps support heavy structures such as leaves and flowers. Many animal cells have small vacuoles, which store substances and transport them within the cell. The cells of some protists also contain vacuoles that may store either useful materials or wastes. 13
Comparing Structures Found in Different Kinds of Cells The table below summarizes the functions of the main components of prokaryotic cells and two types of eukaryotic cells. Cell Components and Functions in Different Organisms Cell Component Function Prokaryotes (Bacteria and Archaea) Plants Eukaryotes Animals Cytoplasm Nucleus Plasma membrane Site of biochemical reactions Control of most cell activities; location of most DNA Control of materials entering and leaving the cell Present Present Present Absent Present Present Present Present Present Cell wall Support for the cell Present Present Absent Mitochondria Cellular respiration Absent Present Present Ribosomes Protein synthesis Present Present Present Chloroplasts Photosynthesis Absent Present Absent Vacuoles Storage; transport; support Absent One large Several small Discussion Question Which cell structures are common to prokaryotic cells, plant cells, and animal cells? Why do you think these features are found in all types of cells? Lesson Review 1. How do eukaryotic organisms differ from prokaryotic organisms? A. Prokaryotic organisms are not made up of cells. B. Prokaryotic organisms do not contain genetic information. C. All eukaryotic organisms have many cells, and prokaryotic organisms have only one. D. Prokaryotic organisms do not have nuclei. 14 Chapter 1: Cell Biology
Lesson 1: Cell Structure 2. Which structures are least likely to appear in the same eukaryotic cell? A. mitochondria and chloroplasts B. ribosomes and mitochondria C. a cell wall and chloroplasts D. small vacuoles and a cell wall 3. Which of the following structures separates the nucleus from its environment? A. cell wall B. plasma membrane C. nuclear membrane D. endoplasmic reticulum 4. The diagram shows the folded inner membrane structure of a mitochondrion. How does this structure help a mitochondrion perform its function in a cell? 15