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Cells are tremendously variable in their shapes and sizes, yet all cells share common properties. They all face the challenge of generating energy from food molecules that they will use to move, grow, and reproduce. This unit provides an overview of molecules and processes that make up the inner workings of the cell.
Cells Are the Basic Units of Living Organisms
All cells evolved from a common ancestor and use the same kinds of carbon-based molecules. Learn how cell function depends on a diverse group of nucleic acids, proteins, lipids, and sugars.
Eukaryotic Cells Possess a Nucleus and Membrane-Bound Organelles
Eukaryotic cells are more complex than prokaryotic ones because of specialized organelles. Learn how ancient collaborations between cells gave eukaryotes an important energy boost.
Cell Function Depends on the Continual Uptake and Conversion of Energy
Cells generate energy from the controlled breakdown of food molecules. Learn more about the energy-generating processes of glycolysis, the citric acid cycle, and oxidative phosphorylation.
Photosynthetic Cells Capture Light Energy and Convert It to Chemical Energy
The sun is the ultimate source of energy for virtually all organisms. Photosynthetic cells are able to use solar energy to synthesize energy-rich food molecules and to produce oxygen.
Metabolism is the Complete Set of Biochemical Reactions within a Cell
Cells constantly adjust the flow of molecules through metabolic pathways in response to energy needs. Learn how enzymes control these molecular transformations.
A cell's ability to function depends on its set of various proteins. How is a cell’s genetic information used to make proteins, the master operators of the cell? In this unit, you will learn about the processes involved in producing proteins and how a protein's three-dimensional form determines its function.
Information Transfer in Cells Requires Many Proteins and Nucleic Acids
The decoding of information in a cell's DNA into proteins begins with a complex interaction of nucleic acids. Learn how this step inside the nucleus leads to protein synthesis in the cytoplasm.
DNA Is Extensively Compacted with Proteins Chromosomes
Long, slender DNA molecules wind around proteins and fold in complex ways to form chromosomes. Learn how chromosomes are more than just packaging devices for DNA.
Differential Control of Transcription and Translation Underlies Changes in Cell Function
In multicellular organisms, nearly all cells have the same DNA, but different cell types express distinct proteins. Learn how cells adjust these proteins to produce their unique identities.
The Functions of Proteins Are Determined by Their Three-Dimensional Structures
Proteins are the workhorses of cells. Learn how their functions are based on their three-dimensional structures, which emerge from a complex folding process.
Proteins Are Responsible for a Diverse Range of Structural and Catalytic Functions in Cells
Protein surfaces are designed for interaction. Learn how proteins can bind and release other molecules as they carry out many different roles in cells.
What are the specialized components of a cell? Some parts of a cell are universal to all types, and some are specific to certain tissues and organisms. The eukaryotic cell cytoplasm contains a variety of membrane-enclosed compartments, called organelles, and each has a specialized function. How are these organelles organized within the cytoplasm? In this unit, you will learn about membrane-bound cell compartments called organelles, which are essential to cell structure and function.
Specialized Membranes Organize the Eukaryotic Cell Cytoplasm into Compartments
There are many different kinds of membranes in a cell. Learn how they subdivide sections of a cell and how proteins in these membranes are gatekeepers for what goes in and what comes out.
Cytoskeletal Networks Provide Spatial Organization and Mechanical Support to Eukaryotic Cells
Dynamic networks of protein filaments give shape to cells and power cell movement. Learn how microtubules, actin filaments, and intermediate filaments organize the cell.
The internal membranes of eukaryotic cells form an interconnected network. Learn about how they break down food particles, recycle cell debris, and export waste.
Mitochondria Are Independently Replicating Organelles That Supply Much of the Energy of the Cell
Mitochondria are fascinating structures that create energy to run the cell. Learn how the small genome inside mitochondria assists this function and how proteins from the cell assist in energy production.
Plant Cells Have Chloroplasts and Other Structures Not Present in Animal Cells
Plant cells have some specialized properties that make them distinct from animal cells. Learn how special structures, such as chloroplasts and cell walls, create this distinction.
Cells do not exist in isolation. They are constantly receiving and sending signals to other cells and to themselves. How do cells sense their environment and initiate responses to signals they receive? This unit introduces the biochemical pathways that cells use to process information from their environment.
Cells Receive and Process a Diverse Set of Chemical Signals and Sensory Stimuli
Chemical signals are continually bombarding cell. Learn how the binding of a signal to cell receptors initiates a process called signal trandsduction inside the cell that causes a chain of reactions.
G-Protein-Coupled Receptors Play Many Different Roles in Eukaryotic Cell Signaling
The large family of G-protein-coupled receptors (GPCRs) contains a diverse group of membrane-bound signaling molecules. Learn how activated GPCRs relay messages by heterotrimeric GTP-binding proteins.
Ion Channel Receptors Generate Electrical Signals in Response to Chemical Signals
An excitable cell converts chemical or mechanical signals into electrical signals. Learn how ion channels connected to a receptor make this conversion happen.
Receptor Tyrosine Kinases Regulate Cell Growth, Differentiation, and Survival
Signal binding to membrane receptor tyrosine kinases (RTKs) activates an enzyme called a kinase. Learn how kinases initiate a signaling cascade that relays information to the nucleus.
Cells Sense the Presence of Other Cells and Their Environment
The orderly arrangement of cells in tissues depends on complex signaling between cells. Learn how cellular junctions play important roles in cell adhesion and communication.
The ability to reproduce is one of the defining characteristics of cells. Intricate cellular controls ensure that cell division is accurate and occurs only under the appropriate conditions. What happens when these control systems go awry? In this unit, you will learn about the cell cycle, the molecules that control it, and how slight alterations in the cycle can lead to large-scale changes in tissues and whole organisms.
The Eukaryotic Cell Cycle Consists of Discrete Phases
Cells grow and replicate their DNA, and then they divide. Learn the substages of this iterative pattern, called the cell cycle. How does a cell regulate these stages?
Cyclin-Dependent Kinases Regulate Progression through the Cell Cycle
Coordinated protein phosphorylation reactions control progression through the cell cycle. Learn how specific complexes of cyclins and cyclin-dependent kinases (CDKs) catalyze these reactions.
Mitosis Produces Two Daughter Cells with the Same Genetic Makeup
Cells duplicate and condense their DNA prior to entering mitosis. During mitosis, chromosomes attach to a spindle of microtubules that distribute them equally to two daughter cells.
Tissues Are Organized Communities of Different Cell Types
The organized arrangement of cells in tissues relies on controlled cell division and cell death. Learn how cells are replenished by stem cells and removed by apoptosis.
Normal Controls on Cell Division are Lost during Cancer
Cancer is somewhat like an evolutionary process. Over time, cancer cells accumulate multiple mutations in genes that control cell division. Learn how dangerous this accumulation can be.
References and Supplementary Materials
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