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    • Time: 36 hours
    • Free Certificate

    This course is intended for students interested in understanding and appreciating common biological topics, studying the smallest foundational units within biology: molecules and cells. Molecular and cellular biology is a dynamic field. There are thousands of opportunities within the medical, pharmaceutical, agricultural, educational, and industrial fields for experts in molecular and cellular processes. This course introduces these topics and provides a deeper understanding of how environmental factors affect and are affected by molecular and cellular processes. It will prepare you for diverse career paths and help you make sound everyday decisions that can improve your diet and health.

  • Unit 1: Introduction to Biology

    Biology is the study of life. While biologists have made great strides in discovering things on Earth, there are many new things to learn. What is life? What properties are required to be considered "living"? These questions are essential to discoveries biologists make every day. With such a vast scope of information, biologists must organize and categorize these discoveries to show connections and patterns to known facts. In this unit, we introduce the major topics biologists study and the theories they use and apply to their work.

    Completing this unit should take you approximately 2 hours.

    • 1.1: Introduction to Biological Inquiry

      Scientists search for knowledge through inquiry, which is a way of questioning and explaining phenomena that occur in nature. Science is a way of knowing. Let's begin our inquiry by exploring how biologists and researchers use the scientific method as an objective means of understanding the properties of life.

    • 1.2: Biological Systems and Water

      All living things have some core properties. Biologists focus on unifying themes that all discoveries fall under. For example, Earth, the only known biosphere, is made of 75 to 80 percent water. Since water's properties are conducive to life on Earth, scientists search for life when they discover the presence of water on other planets. The characteristics of living organisms (evolutionary adaptation, growth, metabolism, reproduction, etc.) differentiate living and non-living things. The fundamental difference between a living thing and a non-living thing is metabolism. Note that we are not contrasting "living" with "dead" – the word dead indicates something that once had properties of life! Metabolism is the chemistry of life; it encompasses all the biochemical reactions occurring in all the cells that make up an individual organism. The word biochemical differs from just chemical in that biochemical processes are specifically concerned with the chemical reactions that occur within living organisms and their implications for life processes and health. Life ceases when the biochemical reactions of metabolism cease. Life's characteristics include adaptation and change, maintenance of cellular structures, growth and development, homeostasis, metabolism, reproduction, and responsiveness to the environment.

    • Unit 1 Assessment

  • Unit 2: Basic Chemistry

    Nature requires the coordination and cooperation of multiple fields of study. It incorporates biology, physics, chemistry, and other academic disciplines. Life is multidisciplinary and driven by chemical processes. You need a basic understanding and appreciation of chemistry to fully understand biology since many topics overlap. For example, in Unit 1, we pegged the atom as the first part of the biological hierarchy. Here, we offer a deeper understanding of the atom as a foundational level of organization.

    Completing this unit should take you approximately 3 hours.

    • 2.1: Atoms and Molecules

      Atoms are the smallest structures in the universe. These substances cannot be broken down any further. Atoms join together to form elements. Elements come together to form molecules, which are the building blocks of the lowest level of life, the cell. To understand biology, you need to understand how these foundational elements form the structures of life. Protons, neutrons, and electrons are the primary subatomic particles. Protons and neutrons make up the nucleus of an atom. Electrons are found outside the nucleus. A proton has an electrical charge of +1. A neutron is nearly identical in size to a proton, but it has no charge. An electron is much smaller than a proton or neutron. An electron is also a charged particle. Despite being much smaller than a proton, the charge of an electron is equal in magnitude to the charge of a proton. However, the charge is opposite, so each electron has a charge of -1.

    • 2.2: Thermodynamics

      Thermodynamics is the scientific branch that studies how energy is transformed from one form to another. We study thermodynamics in biology because organisms are involved in many energy transactions. In other words, organisms are thermodynamic systems. Biochemical reactions must follow the laws of thermodynamics to predict whether reactions occur spontaneously or without any energy required. For example, living things need the ability to move. Energy gives this power, but it must be harnessed and transformed from one form of energy to another. Living things need usable forms of energy.

      Two of the four laws of thermodynamics are especially important in biology:

      • The First Law of Thermodynamics states that energy cannot be created or destroyed, although it can be transferred and transformed. This is also known as the law of conservation of energy.
      • The Second Law of Thermodynamics states that every energy transaction increases the entropy (disorder) of the universe. This second law implies that every energy transaction involves some loss of usable energy as heat, so no energetic process (including those occurring in organisms) can ever be perfectly efficient.

      We will review thermodynamics again in Unit 5 when we study metabolism and metabolic pathways.

      Energy is a basic process common among all living organisms. We define energy as the capacity to do work, which refers to some sort of change. For example, moving an object from one place to another requires work, and energy is required for that work. Heat is energy in the form of the movement of particles (atoms, ions, or molecules) within a substance.

      Heat is energy that is unavailable for performing work. Temperature measures the average speed of the particles in an object. Temperature and heat are not the same thing. Temperature does not depend on how much matter is present, whereas heat does.

      For example, a swimming pool has the same temperature as a cup of water from that swimming pool, but the swimming pool contains much more heat than the cup of water because it contains much more matter.

    • Unit 2 Assessment

  • Unit 3: Biological Molecules

    Biological molecules are the essential molecules needed for life. These molecules can be organic or inorganic. Organic chemistry is the study of carbon, an element that forms strong covalent bonds essential for the foundational structures of all living things. Water, salts, acids, and bases are mostly essential inorganic molecules that facilitate many biological processes. All organisms contain organic biological molecules – carbohydrates, proteins, lipids, and nucleic acid – essential to life. This unit explores the structures and functions of these organic molecules and how our body needs them to function properly.

    Completing this unit should take you approximately 5 hours.

    • 3.1: Water and Organic Molecules

      The important molecules of life include water, salts, acids, bases, and organic compounds. Water is the solvent of life. Living organisms survive because of chemical reactions that occur in the presence of water. Molecules dissolved in water (salts, acids, and bases) are hydrophilic, while organic molecules that are nonpolar and unable to form hydrogen bonds with water are hydrophobic. Each type of substance has an important role in the chemical reactions of life. Water is one of the most important compounds on earth – no living organism can survive without it.

    • 3.2: Acids and Bases

      pH measures the very reactive hydrogen ion. We use the pH scale to measure the hydrogen ion concentration of biological systems. An imbalance in the level of hydrogen ions can be damaging to life. Acids are molecules that, when dissolved in water, increase the hydrogen concentration levels in the solution. Bases are molecules that, when dissolved in water, decrease the hydrogen concentration in the solution. Buffers work to maintain pH by regulating levels of hydrogen ions in living things.

    • 3.3: Biological Macromolecules

      Living things are primarily composed of organic or carbon-based molecules. Carbon has four valence electrons, which allows it to form strong covalent bonds in large, complex, and diverse molecules. Living things need this molecule diversity to provide many structures with different functions. These biological macromolecules of life are carbohydrates, lipids, proteins, and nucleic acids.

      All organisms contain organic biological molecules – carbohydrates, proteins, lipids, and nucleic acid – which are essential to life.

      1. Lipids consist of a diverse set of hydrocarbon molecules (containing hydrogen and carbon). This makes them largely non-polar because the covalent bonds in hydrocarbons (between two carbon atoms or between a carbon atom and a hydrogen atom) feature equal sharing of electrons.
      2. Polysaccharides are complex carbohydrates of carbon, hydrogen, and oxygen in a 1:2:1 ratio, giving them an empirical formula generalized as (CH2O)n (note that the "n" is a designation of the number of carbons in the molecule).
      3. Proteins are enormously diverse in structure and function, yet they all feature the substructure of amino acids. Each amino acid features a central carbon atom connected to a hydrogen atom, an amino group, a carboxyl group, and a variable R group.
      4. Nucleic acids are informational molecules with a basic structure. Each of their subunits includes a five-carbon sugar (either ribose or deoxyribose) attached to a phosphate group and a nitrogenous base.

      Knowing the chemical structure that underlies these essential biomolecules not only allows you to recognize them. It explains how they are constructed within cells and how they interact chemically with each other in metabolism and give rise to the structural component of organisms.

      • A polymer is a particular category of macromolecule built by connecting many smaller subunits called monomers (poly means many). Of the four biological macromolecules you have been studying, only three are polymers. Lipids are not polymers, but the others are.
      • Polysaccharides are macromolecular carbohydrates. Be careful with the words polysaccharide and carbohydrate. They are sometimes used interchangeably but should not be. Carbohydrates include both small molecules and large molecules (macromolecules). Polysaccharides are a type of carbohydrate, but not all carbohydrates are polysaccharides. As the name implies, polysaccharides are polymers made up of multiple monosaccharides. Monosaccharides are monomers, and they can be connected in a linear or branched arrangement.
      • Proteins are polymers that are made up of monomers called amino acids. Unlike polysaccharides, which may be branched, a protein must be a linear (or end-to-end) arrangement of amino acids. Organisms use 20 different kinds of amino acids (in an unlimited number of combinations and orders) to construct their proteins.
      • We can also call a nucleic acid a polynucleotide. That alternative name indicates it is a polymer made up of many nucleotides. In the case of DNA, the monomers are nucleotides containing the pentose (five-carbon sugar) called deoxyribose. For RNA, the nucleotides contain ribose instead of deoxyribose. Although there are only four commonly used DNA nucleotides (and four commonly used RNA nucleotides), a typical DNA molecule contains millions of nucleotides, so there is an unlimited number of sequences of such nucleotides.

      Make sure you can match each type of monomer to the type of polymer that can be made from such monomers. You should also know how polymers are constructed using dehydration reactions and deconstructed using hydrolysis reactions.

    • Unit 3 Assessment

  • Unit 4: Cells and Cell Membranes

    Cells are the smallest units of life. In this unit, we explore the characteristics, components, and functions of cells. Learning about the structures of cells allows us to see the similarities and differences among organisms. Bacteria, plant, animal, and fungus cells are similar in many ways and contain many of the same small structures known as organelles. However, some characteristics help distinguish whether a cell belongs to an animal, plant, fungus, or bacteria. For example, all plant cells contain cell walls, while animal cells lack this particular extracellular structure. The water within a cell that presses against the cell wall gives a plant its rigidity and your celery its crunch!

    Completing this unit should take you approximately 6 hours.

    • 4.1: Cellular Organization and Organelles

      Although all cells share certain characteristics (for example, every cell has a plasma membrane), biologists recognize two fundamentally different categories of cells: prokaryotic and eukaryotic. We compartmentalize cells into several structures with specific functions in the cell. We call these structures organelles. Organelles are subunits in the anatomy of the cell. The advantage of compartmentalization inside the cell is that many different functions can be localized in specific places. This brings about a high level of organization and efficiency for the cell. In this section, we discuss the structures and functions of the different parts of the cell.

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        Cell Structure Page
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        Parts of a Cell Page
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        Studying Cells Page
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        Prokaryotic Cells Page
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        Eukaryotic Cells Page
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        Types of Cells Page
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        The Endomembrane System, Proteins, the Cytoskeleton, and Connections between Cells and Cellular Activities Book
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      • Test Yourself: Prokaryotic and Eukaryotic Organelles

        It is a good idea to make a visual study guide because you will need to recognize the different structures and functions of all prokaryotic and eukaryotic organelles. Start by listing all of the organelles. Then designate them as being found in prokaryotes, eukaryotes, or both. Use appropriate vocabulary to describe their structures and general functions in a cell.

        Quiz yourself – you should be able to describe the structure and function of all organelles in the cell, explain how organelles control protein synthesis in the cytoplasm, discuss the difference in organelles between plant and animal cells, list the components of the endomembrane system, describe the energy conversions carried out by mitochondria and chloroplasts, and describe the various functions of the cytoskeleton.

    • 4.2: The Cell or Plasma Membrane

      The cell membrane (often called the plasma membrane) protects the contents within the cell and monitors all of the components that enter and exit the cell. The cell or plasma membrane also plays a role in the communication and attachment of tissues. Its structure is made of phospholipids and proteins. These biological molecules play an important role in the different actions of the cell's membrane. In this section, we discuss the structure and function of the membrane and its impact on the life of the cell.

    • 4.3: Membranes, Lipids, and the Fluid Mosaic Model

      We measure the fluid components of the membrane by the types and amounts of lipids found in the membrane. We describe the protein components of the membrane as a mosaic with different functions. In this section, we discuss the structures and functions of the components of the plasma membrane. After you have watched the videos in this section, you should be able to explain how molecules cross cell membranes, discuss the channel proteins, carrier proteins, pumps, and aquaporins involved in transport, distinguish between osmosis, facilitated diffusion, and active transport, and describe how large molecules are transported across a cell membrane.

    • 4.4: Diffusion, Osmosis, and Active Transport

      The plasma membrane is a selectively permeable barrier. We classify transmembrane transport (transport of a particle through a biological membrane) as active or passive. The distinction refers to the requirement of an external source of energy.

      • Active transport, as its name implies, requires an additional (external) energy source to drive it. That energy source is often ATP, but other sources can also be used. The additional energy allows active transport to move particles against their gradient.
      • Passive transport does not require additional (external) energy for the transport to occur. A gradient that drives passive transport can be a concentration gradient (when the concentration of a certain particle is higher on one side of the membrane than the other), an electrical gradient (when the charge distribution is different on one side of the membrane than the other), or both. In all cases, the transport occurs "down" the gradient – from the place of higher to lower concentration). Passive transport never occurs in the direction against the gradient.

      Three subcategories of passive transport include:

      1. Simple diffusion is the passive transport of solute particles down the gradient through the phospholipid bilayer of the biological membrane. This only occurs for particles small or non-polar enough to pass through the bilayer.
      2. Facilitated diffusion requires the help or facilitation of a transport protein to get the particle through the membrane. This occurs for particles that are too big or too polar to cross the phospholipid bilayer.
      3. Osmosis is the passive transport of solvent particles (not solute particles) down the gradient through a selectively permeable membrane. Since the solvent is always water in biological systems, biological osmosis refers to the movement of water.

      These transmembrane transport processes are fundamental to life because organisms must continuously exchange materials with their surroundings to stay alive.

    • 4.5: Transporting Signal Molecules across the Plasma Membrane

      Signal molecules are examples of ligands (a molecule that binds to another, usually larger, molecule) because they bind to other molecules to pass through the plasma membrane. The molecules the signals bind to are called receptors. When a signal binds to a receptor, the binding causes changes in the cell. These changes are the responses to the signal.

      Some signal molecules are small and non-polar, so they are easily able to pass through a cell's plasma membrane, and therefore, they bind to internal receptors. Most signals, however, are too large or too polar to pass through the plasma membrane, so they must bind to receptors on the exterior surface of the cell. Although these signals do not enter the cell, they still cause changes inside the cell.
      There are three primary mechanisms for this occurrence – the difference lies in what kind of receptor receives these signals.

      1. Ion-channel-linked receptors are transmembrane proteins that simultaneously serve as signal receptors and ion channels. When a signal molecule binds to such a receptor, the ion channel either opens or closes its gate. This leads to changes in the flow of ions, which are charged particles. This redistribution of charge causes various responses.
      2. G-protein-linked receptors are transmembrane receptors that are associated with special proteins (G proteins) situated on the part of the protein that is in contact with the interior surface of the membrane. The binding of a signal to the receptor activates (and frees) the G protein, and that activation leads to various responses.
      3. Enzyme-linked receptors are transmembrane proteins that simultaneously serve as signal receptors and enzymes. The binding of a signal to the receptor activates the enzymatic portion of the receptor (which faces the interior of the cell), and once activated, the enzyme catalyzes various reactions, leading to various responses.

    • Unit 4 Assessment

  • Unit 5: Enzymes, Metabolism, Cellular Respiration

    Metabolism refers to the sum total of every chemical reaction in every organism. Cells use enzymes and metabolic pathways to conduct these chemical reactions. It is essential to understand the reactions that comprise metabolism to learn how organisms acquire and use energy to survive. Since this process is complicated, we will explore it from several angles in this unit.

    Completing this unit should take you approximately 5 hours.

    • 5.1: Energy and Thermodynamics

      Energy flows through all living systems. The chemical reactions that build and break down energy-containing compounds are vital to all living organisms. Biochemical pathways involve the building and breaking down through anabolism and catabolism, respectively. Notice that all of these pathways involve chemical reactions that require enzymes, which are the biological catalysts we will discuss in the next section. Remember that the laws of thermodynamics state that energy is neither created nor destroyed but transformed from one form to another. Biochemical reactions follow these same laws of thermodynamics, which predict whether reactions will occur spontaneously or without any energy required.

    • 5.2: Metabolic Pathways, Enzymes, and Regulation

      Metabolism refers to all chemical reactions in the cell. Some reactions break down large molecules and release energy, while others require energy to build up large molecules. These reactions are connected via metabolic pathways that must be regulated to conserve resources and energy.

    • 5.3: The Role of Cellular Respiration, Energy, and ATP

      In this section, we explore cellular respiration. This metabolic pathway breaks down our food in the form of glucose to produce oxygen, water, and ATP, which is the most usable energy source for the cell. This process takes place in the mitochondria within the cell. Aerobic respiration occurs in the presence of oxygen; anaerobic respiration occurs without oxygen and builds lactic acid.

      Any living cell can extract energy from fuel and temporarily store that energy in the form of ATP or a similar energy currency. The primary processing of fuel is called glycolysis. Only certain cells under the right conditions can continue where glycolysis leaves off, allowing much more usable energy to be extracted from the fuel.

      That additional processing of energy is called cellular respiration. Glycolysis and cellular respiration extract usable energy from fuel by undergoing oxidation/reduction (or redox) reactions.

      Oxidation refers to the loss of electrons from a particle (such as a fuel molecule), whereas reduction is the gain of electrons. Since electrons are not destroyed in chemical reactions, oxidation occurs only if reduction also occurs. When something is oxidized (loses electrons), something else gets reduced (gains electrons).

      Organisms extract energy from fuel molecules by oxidizing these fuel molecules. In cellular respiration, there is a substance (external to the process) that ultimately accepts the electrons that have been removed from the fuel. For aerobic organisms, that substance is oxygen, and when oxygen accepts those electrons (along with protons) from the fuel molecules, the oxygen gets reduced into water. Cellular respiration is important because it allows for the maximal oxidation of fuels, which maximizes the amount of energy that can be extracted and stored as ATP.

    • 5.4: Glycolysis

      Living organisms perform an important catabolic pathway that breaks down organic compounds to yield energy as ATP. The molecules are completely broken down aerobically through cell respiration. Scientists have defined three primary stages in cell respiration, which we will review in detail: glycolysis, the citric acid cycle, and oxidative phosphorylation.

      Glycolysis is the first step in cellular respiration. It involves the partial breakdown of glucose into two pyruvate molecules. Glycolysis is also the first step in harvesting potential energy from the glucose bond. Notice that glycolysis, a multi-step biochemical pathway, produces a small amount of energetic resources.

    • 5.5: The Krebs Cycle (Citric Acid Cycle)

      The Krebs cycle (also called the citric acid cycle and TCA cycle) is a cyclical biochemical pathway that begins the completion of the oxidation of glucose. While it forms a small amount of ATP via substrate-level phosphorylation, its main role is the formation of energetic electron carriers that are needed for the electron transport chain.

    • 5.6: Oxidative Phosphorylation: Electron Transport Chain and Chemiosmosis

      Oxidative phosphorylation is the final stage of cellular respiration and consists of two closely connected components: the electron transport chain and chemiosmosis. In the electron transport chain, electrons are passed from one molecule to another, and the energy released during these electron transfers is used to form an electrochemical gradient. In chemiosmosis, the energy stored in the gradient produces ATP.

      The electron transport chain is a collection of proteins located in the inner membrane of the mitochondria known for its role in creating a proton gradient that is necessary for oxidative phosphorylation. These proteins are part of the final step of cellular respiration, where glucose is completely oxidized by oxygen. The electrons, temporarily carried by previous redox electron carriers, move through the chain and reduce oxygen gas.

    • 5.7: Anaerobic Cellular Respiration: Fermentation

      Organic molecules are partially broken down when they lack oxygen. Some organisms use fermentation to break glucose down when oxygen is not available, following the electron transport chain.

    • Unit 5 Assessment

  • Unit 6: Photosynthesis

    Have you ever wondered how a plant grows from a tiny acorn into a giant oak tree? Where does all that biomass come from? How does it get the energy to grow? Photosynthesis is the fascinating process plants use to convert light energy to chemical energy. Because plants are at the bottom of the food pyramid in almost all ecological systems, understanding how they grow and develop will give you a greater understanding of your environment.

    Completing this unit should take you approximately 4 hours.

    • 6.1: Overview of Photosynthesis

      Photosynthesis is how green plants and other photosynthetic organisms use sunlight's power to synthesize their own food from carbon dioxide and water. It harnesses sunlight by using the green pigment chlorophyll and generates oxygen as a byproduct. The food and oxygen created by these autotrophs (organisms that make their own food) indirectly nourish and energize the whole earth.

    • 6.2: Photosynthesis and Photorespiration

      The products of photosynthesis are sugars and oxygen. This anabolic process requires the reactants carbon dioxide and water. When there are significant amounts of these reactants, photosynthesis can nourish the plant and indirectly support life on Earth. However, in environments where water and carbon dioxide are limited, there is a risk of photorespiration.

    • 6.3: C-4 and CAM Photosynthesis

      The fixation step is a crucial step in the Calvin cycle. It takes in carbon dioxide and joins it with an intermediate compound (ribulose bisphosphate), thus incorporating inorganic carbon dioxide into an organic compound. The enzyme that catalyzes this step is called RuBisCO (ribulose bisphosphate carboxylase oxygenase).

      RuBisCO can operate to join either carbon dioxide or oxygen to ribulose bisphosphate. However, joining oxygen instead of carbon dioxide is counterproductive because no carbon fixation (the purpose of the Calvin cycle) takes place. This counterproductive process (incorporating oxygen instead of carbon dioxide) is called photorespiration.

      Two major categories of plant species have evolved ways around this problem:

      1. C-4 plants separate the process of carbon dioxide intake (which occurs in superficial cells called mesophyll cells) from the process of carbon fixation in the Calvin cycle (which occurs in deeper cells called bundle sheath cells).
      2. CAM plants take in carbon dioxide and store it in the form of organic acids during the night when their stomata are open. During the day, the organic acids are broken down to release the carbon dioxide for the Calvin cycle while the stomata are closed (preventing oxygen from interfering).

      These two types of plants operate the Calvin cycle more efficiently because photorespiration is minimized. As you review C-4 plants and CAM plants, notice that they accomplish the same thing in two different ways. After you have read this section, you should be able to define the purpose of the stomata, describe the two photosynthetic adaptations that minimize photorespiration, and list the types of plants that have these adaptations.

    • 6.4: The Carbon Cycle

      The phrase "carbon cycle" refers to the many chemical transformations that occur involving compounds containing carbon. The carbon cycle is cyclic because there is a continuous alternation between the carbon of organic compounds and the carbon of inorganic compounds. Inorganic carbon dioxide gets fixed (by autotrophs) into organic compounds. These organic compounds get converted into other organic compounds (including simple organic compounds like monosaccharides, nucleotides, and amino acids, as well as complex macromolecules like polysaccharides, nucleic acids, lipids, and polypeptides).

      Carbon in these organic compounds is passed from organism to organism as they feed on each other. Some of the organic molecules are used as fuel by the organisms, and the oxidation of these organic fuels (to provide energy for the organisms) returns the carbon to inorganic form (carbon dioxide) to complete the cycle. In this cycle of transformations, carbon (matter) remains in the ecosystem (it is conserved). It is not destroyed; it is only transferred and transformed.

    • Unit 6 Assessment

  • Unit 7: Cellular Reproduction: Mitosis

    Organisms require their cells to divide for reproduction, growth, development, and repair. Cellular division is divided into two phases: Mitosis and cytokinesis. Mitosis involves the division of the nuclear chromosomes, while cytokinesis is the division of the cytoplasmic components into new daughter cells. Serious consequences, such as cancer, can occur if this cell cycle is disrupted in some way.

    Completing this unit should take you approximately 3 hours.

    • 7.1: DNA and RNA

      Molecular biology studies subcellular structures, their interactions, and how they function in the cell's biological processes. Nucleic acids are important molecules that carry information that leads to the production of proteins. Proteins are the physical expression of genetic information in cells.

      The nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are important molecules that carry genetic information throughout cells. Like an architect's blueprint, nucleic acids have rules that lead to the synthesis of the major building blocks of living things.

      As their names indicate, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are both nucleic acids. Any nucleic acid is a polymer made up of monomers called nucleotides.

      Any nucleotide consists of three components:

      1. A pentose (five-carbon sugar)
      2. A nitrogenous base attached to the pentose
      3. A phosphate group also attached to the pentose

      For DNA, the specific pentose in each of its nucleotides is deoxyribose, whereas RNA features ribose as the pentose in each of its nucleotides. There are normally four kinds of DNA nucleotides because there are four normal nitrogenous bases used in DNA: adenine, guanine, cytosine, and thymine.

      RNA also features four kinds of nucleotides, and the nitrogenous bases are nearly the same as for DNA, except that RNA uses uracil instead of thymine. DNA functions for self-replication (before a cell divides into two cells) and for transcription, a process that produces RNA. There are different functional categories of RNA, including mRNA, tRNA, rRNA, and others.

    • 7.2: Cell Division

      All living things are composed of cells. All cells come from other cells through the process of cell division. Some cells divide for reproduction purposes, while others divide for growth, development, or repair.

    • Unit 7 Assessment

  • Unit 8: Cellular Reproduction: Meiosis

    Meiosis is a specialized type of cellular reproduction that only occurs in the ovaries and testes and results in an egg or sperm, respectively. Sexual reproduction is responsible for the amazing amount of diversity within a species. When sperm fertilizes an egg, the resulting offspring contain genes from the father and the mother. In essence, you contain genes from ALL of your ancestors, at least in a small part.

    Completing this unit should take you approximately 2 hours.

    • 8.1: Cell Division, Meiosis, and Sexual Reproduction

      Meiosis is a type of cell division that leads to the production of non-identical daughter cells. These sex cells contain half the genetic information and are combined for sexual reproduction; this is the reason Meiosis is also called "reduction division". Sexual reproduction is critical for the diversity of living things.

      Meiosis is unique to organisms that reproduce sexually (plants, animals, fungi). The life cycle of any sexual species features fertilization, which is the fusion of unicellular gametes (one male gamete and one female gamete) to produce a unicellular zygote. The unicellular zygote produced by fertilization carries a random mix of chromosomes from both gametes.

      Consequently, the ploidy (the number of sets of chromosomes in a cell) of the zygote is double the ploidy of the gametes. If fertilization were the only process occurring in each generation, then the ploidy would double each generation (tetraploid, octoploid, etc.), and the resulting zygote would not survive. A separate process is needed to cut the ploidy in half to prevent the ploidy from doubling each generation.

    • 8.2: Chromosomes, Chromatids, and Chromatin

      Chromosomes are unique collections of genetic material that make up each of us as individuals. They are made up of chromatin which is composed of histone proteins and DNA. When DNA is copied, chromatids are formed to be passed on to cells upon cell division.

    • Unit 8 Assessment

  • Unit 9: Mendelian Genetics and Chromosomes

    Do you ever wonder why you look like your brother or sister or where you got your freckles? Are you concerned about developing a disease another family member struggles with? We can answer these types of questions with an understanding of genetics. In this unit, we learn about the basic principles of inheritance and the probability of passing certain traits from one generation to another.

    Completing this unit should take you approximately 3 hours.

    • 9.1: Introduction to Genetics

      Genetics studies heredity and how different characteristics are passed from generation to generation. It also examines the variation of characteristics important for the diversity of life. Scientists have studied inheritance laws and detailed their frequent exceptions. We often say our genes give us our traits. This is true, but only indirectly.

    • 9.2: Heredity

      Heredity is the study of how characteristics are passed from parents to offspring. Genetic information is physically expressed through the production of proteins. We call this physical expression the phenotype. Scientists study the probability of certain phenotypes being passed to future generations to help demonstrate the laws of heredity.

    • Unit 9 Assessment

  • Unit 10: Gene Expression

    This unit teaches us about the universal genetic codes deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). We call DNA and RNA universal because we find them in every known organism. As we learned in Unit 7, the DNA and RNA in every organism are made up of the same few ingredients. However, extremely slight differences often account for the differences between species. What makes a dog different from a toadstool? What accounts for the differences within species? What makes you different from your neighbor? This unit will give you a greater understanding of the genetic code and its impact on your life.

    Completing this unit should take you approximately 3 hours.

    • 10.1: DNA Replication and Synthesis

      Cells make copies of their DNA before they divide into identical daughter cells. This process is called DNA replication or synthesis. Chromosomes for sister chromatids after the copying of DNA. This allows cells to receive genetic information and produce proteins for identical phenotypes.

    • 10.2: DNA Transcription

      Genes are expressed by the production of proteins through two processes: transcription and translation. Transcription involves using the DNA code as a template to make mRNA messages. Translation involves the ribosome interpreting that message to build proteins.

    • 10.3: Translation and Synthesis

      Now that we have learned about transcription, let's review the second process of gene expression, which is translation. Translation refers to how the ribosome uses messenger RNA (mRNA) and transfer RNA (tRNA) to attach amino acids together to make proteins.

    • 10.4: Regulating Gene Expression

      Gene expression must be regulated throughout much of life. During certain times of development, growth, or repair, genes must be turned on and off. This helps cells interact with their environment and maintain homeostasis.

    • 10.5: Using DNA Technology

      DNA technologies have benefited our society in many ways. For example, today's scientists use the concepts you have studied in this course to improve our criminal justice system, enhance our food supply, and treat previously incurable diseases.
      Forensic scientists have developed next-generation DNA sequencing techniques using ever-smaller amounts of DNA evidence to identify criminals who have escaped criminal justice for years. These technologies have simultaneously allowed us to exonerate individuals who have been wrongly convicted and imprisoned for crimes they did not commit.

      Humans have used selective breeding techniques to artificially alter the genomes of plants and animals for thousands of years. However, today's biochemists use modern genetic manipulation techniques to quickly and efficiently modify the DNA in plants to create genetically modified organisms (GMOs). Farmers plant these genetically modified seeds to grow crops that produce more edible plant material, grow well in drought conditions, resist diseases, and repel destructive insects.

      Scientists have also created the gene-editing technique called CRISPR to swap faulty genes with healthy ones to treat human genetic disorders that cause debilitating diseases and cancers.

    • Unit 10 Assessment

  • Study Guide

    This study guide will help you get ready for the final exam. It discusses the key topics in each unit, walks through the learning outcomes, and lists important vocabulary. It is not meant to replace the course materials.

  • Certificate Final Exam

    Take this exam if you want to earn a free Course Completion Certificate.

    To receive a free Course Completion Certificate, you will need to earn a grade of 70% or higher on this final exam. Your grade for the exam will be calculated as soon as you complete it. If you do not pass the exam on your first try, you can take it again as many times as you want, with a 7-day waiting period between each attempt.

    Once you pass this final exam, you will be awarded a free Course Completion Certificate.

  • Saylor Direct Credit

    Take this exam if you want to earn college credit for this course. This course is eligible for college credit through Saylor Academy's Saylor Direct Credit Program.

    The Saylor Direct Credit Final Exam requires a proctoring fee of $5. To pass this course and earn a Proctor-Verified Course Certificate and official transcript, you will need to earn a grade of 70% or higher on the Saylor Direct Credit Final Exam. Your grade for this exam will be calculated as soon as you complete it. If you do not pass the exam on your first try, you can take it again a maximum of 3 times, with a 14-day waiting period between each attempt.

    We are partnering with SmarterProctoring to help make the proctoring fee more affordable. We will be recording you, your screen, and the audio in your room during the exam. This is an automated proctoring service, but no decisions are automated; recordings are only viewed by our staff with the purpose of making sure it is you taking the exam and verifying any questions about exam integrity. We understand that there are challenges with learning at home - we won't invalidate your exam just because your child ran into the room!

    Requirements:

    1. Desktop Computer
    2. Chrome (v74+)
    3. Webcam + Microphone
    4. 1mbps+ Internet Connection

    Once you pass this final exam, you will be awarded a Credit-Recommended Course Completion Certificate and can request an official transcript.

  • Course Feedback Survey

    Please take a few minutes to give us feedback about this course. We appreciate your feedback, whether you completed the whole course or even just a few resources. Your feedback will help us make our courses better, and we use your feedback each time we make updates to our courses. If you come across any urgent problems, email contact@saylor.org.