🌿Biology for Non-STEM Majors Unit 3 – Cell Structure and Function

Key Concepts

• Cells are the fundamental unit of life and the building blocks of all living organisms
• Cell theory states that all living things are composed of cells, cells are the basic units of structure and function in living things, and all cells come from pre-existing cells
• Cells contain genetic material (DNA) that is passed on from one generation to the next during cell division
• Cells are highly organized structures with specific compartments and organelles that carry out distinct functions
• Cells can be classified into two main types: prokaryotic cells (bacteria and archaea) and eukaryotic cells (plants, animals, fungi, and protists)
• Cell membranes are selectively permeable barriers that control the movement of substances in and out of the cell
• Cells communicate with each other through chemical signaling and cell-to-cell junctions

Cell Basics

• Cells are microscopic structures that make up all living organisms
• The average size of a cell ranges from 1 to 100 micrometers (μm)
• Cells are surrounded by a plasma membrane that separates the cell's interior from the external environment
• The cell's interior, called the cytoplasm, contains various organelles and structures that carry out specific functions
• Cells contain genetic material (DNA) that is stored in the nucleus (in eukaryotic cells) or nucleoid region (in prokaryotic cells)
• Cells require energy to carry out their functions, which is obtained through cellular respiration or photosynthesis
• Cells can reproduce through the process of cell division, creating new cells with identical genetic material

Cell Structures and Their Functions

• The plasma membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell
  • It is composed of a phospholipid bilayer with embedded proteins
  • The fluid mosaic model describes the structure and organization of the plasma membrane
• The nucleus is the control center of eukaryotic cells and contains the cell's genetic material (DNA)
  • The nuclear envelope separates the nucleus from the cytoplasm
  • The nucleolus is a dense region within the nucleus where ribosomal RNA is synthesized
• Ribosomes are the sites of protein synthesis in the cell
  • They can be found free in the cytoplasm or attached to the rough endoplasmic reticulum
• The endoplasmic reticulum (ER) is a network of membrane-bound channels involved in protein and lipid synthesis and transport
  • The rough ER has ribosomes attached to its surface and is involved in protein synthesis and modification
  • The smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification
• The Golgi apparatus is a stack of flattened membrane sacs that modify, package, and sort proteins and lipids for transport to their final destinations
• Mitochondria are the powerhouses of the cell, generating ATP through cellular respiration
  • They have a double membrane structure with the inner membrane folded into cristae
• Lysosomes are membrane-bound organelles containing digestive enzymes that break down cellular waste and foreign particles
• Chloroplasts are the sites of photosynthesis in plant cells and contain chlorophyll pigments that capture light energy

Types of Cells

• Cells can be classified into two main types: prokaryotic cells and eukaryotic cells
• Prokaryotic cells (bacteria and archaea) are simpler and smaller than eukaryotic cells
  • They lack membrane-bound organelles and have a single circular chromosome in the nucleoid region
  • Examples of prokaryotic cells include E. coli and Staphylococcus aureus
• Eukaryotic cells (plants, animals, fungi, and protists) are more complex and larger than prokaryotic cells
  • They have membrane-bound organelles, including a nucleus that contains linear chromosomes
  • Plant cells have additional structures, such as a cell wall, chloroplasts, and a large central vacuole
  • Animal cells lack a cell wall and have a centrosome that organizes the microtubule network
• Specialized cells are differentiated to perform specific functions within multicellular organisms
  • Examples of specialized cells include neurons, muscle cells, and red blood cells

How Cells Work Together

• In multicellular organisms, cells work together to form tissues, organs, and organ systems
• Tissues are groups of cells with similar structures and functions that work together to perform a specific role
  • Examples of tissues include epithelial tissue, connective tissue, muscle tissue, and nervous tissue
• Organs are composed of multiple tissue types that work together to carry out a specific function
  • For example, the heart is an organ composed of cardiac muscle tissue, connective tissue, and epithelial tissue
• Organ systems are groups of organs that work together to perform a specific function in the body
  • The digestive system, for example, includes the mouth, esophagus, stomach, intestines, liver, and pancreas, all working together to break down and absorb nutrients
• Cells communicate with each other through chemical signaling and cell-to-cell junctions
  • Chemical signaling involves the release of signaling molecules (hormones, neurotransmitters) that bind to receptors on target cells
  • Cell-to-cell junctions (tight junctions, gap junctions, desmosomes) allow cells to physically connect and communicate with each other

Real-World Applications

• Understanding cell structure and function is crucial for developing new medical treatments and therapies
  • For example, cancer research focuses on understanding how normal cells become cancerous and developing targeted therapies to stop cancer cell growth
• Stem cell research holds promise for regenerative medicine, as stem cells have the ability to differentiate into various cell types
  • This could potentially be used to replace damaged or diseased tissues and organs
• Genetic engineering involves modifying the genetic material of cells to produce desired traits or products
  • Applications include creating genetically modified crops with improved yield or resistance to pests and diseases
• Cell culture techniques are used in various fields, such as vaccine production, drug testing, and tissue engineering
  • For example, the production of insulin for diabetes treatment involves growing genetically engineered bacterial cells in large bioreactors

Common Misconceptions

• Cells are not the smallest living things; viruses are smaller but are not considered living organisms as they cannot reproduce on their own
• Not all cells have a nucleus; prokaryotic cells lack a membrane-bound nucleus and instead have a nucleoid region containing their genetic material
• The terms "cell" and "molecule" are not interchangeable; cells are composed of many different types of molecules, but not all molecules are cells
• Cells do not have a "brain" that controls their functions; instead, the genetic material (DNA) and various organelles work together to regulate cellular processes
• Cells do not have a "stomach" for digesting food; instead, lysosomes contain digestive enzymes that break down cellular waste and foreign particles
• Not all cells are microscopic; some cells, such as the ostrich egg yolk, can be seen with the naked eye

Study Tips and Tricks

• Create a concept map or flowchart to visualize the relationships between different cell structures and their functions
• Use mnemonic devices to remember the names and functions of cell organelles (e.g., "My Very Eager Mother Just Served Us Nachos" for the order of the stages of mitosis)
• Practice drawing and labeling diagrams of cells and their organelles to reinforce your understanding of their structures
• Watch educational videos and animations that illustrate cellular processes and functions
• Participate in study groups or discuss concepts with classmates to clarify any confusing topics and learn from others' perspectives
• Create flashcards with key terms, definitions, and examples to test your knowledge and identify areas that need more study
• Relate cell structures and functions to real-world examples and applications to make the content more engaging and memorable
• Take practice quizzes and exams to familiarize yourself with the types of questions that may be asked and to identify areas that require more focus