General Biology PDF

CELL THEORY CELL Basic and fundamental unit of life, it The cell theory describes the basic properties of possesses a highly organized...

CELL THEORY CELL Basic and fundamental unit of life, it The cell theory describes the basic properties of possesses a highly organized structure that all cells. enables it to carry out its vital functions. The three scientists who contributed to the development of cell theory are Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. Cell theory is a fundamental principle in biology that describes the properties and functions of cells, which are the basic building blocks of all living organisms. Cell theory has three postulates: 1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of life structure and function in living organisms. 3. All cells are arise from pre-existing cells. The collective efforts of early scientists significantly accelerated the development of cell theory. TIMELINE 1665: Robert Hooke published his book Micrographia, which contains his drawings of a section of cork, as seem through one of the first microscopes. 1674: Anton Van Leeuwenhoek observed tiny living organisms in drops of pond water through his simple microscopes. 1683: Leeuwenhoek discovered bacteria. 1838: Matthias Schleiden concluded that all plants are made up of cells. 1839: Theodor Schwann concluded that all ROUGH ENDOPLASMIC RETICULUM - the animals are made up of cells. molecules in charge of protein production, 1855: Rudolf Virchow proposed that all cells proteins made in the rough endoplasmic reticulum come from existing cells, completing the cell as destined to either be a part of a membrane or to theory. be secreted from the cell membrane out of the cell. LEVELS OF BIOLOGICAL PEROXISOME - it protects the cell from ORGANIZATION reactive oxygen species (ROS) molecule which 1. Cells 8. Ecosystem could seriously damage the cell. 2. Tissues 9. Biosphere 3. Organs GOLGI BODY / GOLGI APPARATUS - it is 4. Organ Systems responsible for packing proteins from the rough 5. Organisms endoplasmic reticulum into membrane-bound 6. Population vesicles. 7. Community CYTOSKELETON - protein framework to build CHLOROPLAST - where photosynthesis occur. cell on. CELL MEMBRANE - protect, boundary, allows passage into and out of the cell. CELL WALL - provides structure and support. CYTOPLASM - holds the internal components of cells in place and protects them from damage. CILIA AND FLAGELLA - propel fluids over cellular surface and enable certain cells to move. MITOCHONDRIA - creates and supplies energy in cell respiration (ATP). BOTH PRESENT IN PLANTS AND ANIMALS CELL RIBOSOME - make proteins and convert genetic CYTOPLASM code into an amino acid sequence. ROUGH ENDOPLASMIC RETICULUM SMOOTH ENDOPLASMIC RETICULUM NUCLEUS - controls the activities of the cell; RIBOSOMES holds DNA and genetic information (chromatin) NUCLEUS NUCLEAR ENVELOPE LYSOSOMES - filled with enzymes for DNA intracellular digestion (breakdown/recycling) VACUOLE MITOCHONDRIA VACUOLES - storage for cells; store food, water CELL MEMBRANE and waste material. ANIMAL CELL ONLY SMOOTH ENDOPLASMIC RETICULUM - LYSOSOMES makes lipids and steroids, instead of being CENTRIOLE involved in protein synthesis; responsible for detoxifying the cell. PLANT CELL ONLY fission, where the cell divides into two genetically PLASTIDS identical cells, and they exhibit a wide range of CELL WALL metabolic pathways, allowing them to thrive in CHLOROPLAST diverse environments, from hot springs to the human gut. THREE MAIN PARTS OF CELL 1. NUCLEUS Eukaryotic cells, on the other hand, are more 2. CYTOPLASM complex and larger than prokaryotic cells, making 3. CELL MEMBRANE up all plant, animal, fungal, and protist organisms. A defining feature of eukaryotic cells is the presence of a well-defined, membrane-bound nucleus that houses the cell's genetic material (DNA). These cells are generally larger, typically ranging from 10 to 100 micrometers in diameter. While all eukaryotic cells have a cell membrane, only plant cells, fungi, and some protists have a cell wall, with plant cell walls composed of cellulose. Eukaryotic cells contain numerous membrane-bound organelles, each with specific functions, such as mitochondria (the powerhouse of the cell, responsible for energy production), the endoplasmic reticulum (involved in protein and lipid synthesis), the Golgi apparatus (modifies, sorts, and packages Prokaryotic vs. Eukaryotic Cells: A proteins and lipids for transport), lysosomes Comparative Overview (contain enzymes for digestion and waste removal), and chloroplasts (present in plant cells and Cells are the basic building blocks of all responsible for photosynthesis). Eukaryotic cells living organisms, and they come in two primary also have a complex cytoskeleton that provides forms: prokaryotic and eukaryotic. Understanding structure, support, and aids in intracellular transport. the differences between these two types of cells is They can reproduce sexually through meiosis and fundamental to the study of biology. fertilization or asexually through mitosis. Prokaryotic cells are simpler and smaller In summary, prokaryotic cells are than eukaryotic cells, found in organisms classified characterized by their simplicity and efficiency, as prokaryotes, which include bacteria and archaea. thriving in a wide range of environments, while One of the key features of prokaryotic cells is the eukaryotic cells, with their complexity, allow for absence of a membrane-bound nucleus; instead, specialized functions and the development of their genetic material (DNA) is located in a region multicellular organisms. These fundamental called the nucleoid, which is not enclosed by a differences highlight the diversity of life and the membrane. These cells are generally smaller, intricate cellular processes that underpin it. typically ranging from 0.1 to 5.0 micrometers in diameter. Most prokaryotic cells have a rigid cell wall that provides shape and protection, with bacterial cell walls composed of peptidoglycan. Additionally, prokaryotic cells lack membrane- bound organelles, instead having simple structures such as ribosomes, responsible for protein synthesis. Prokaryotes reproduce asexually through binary  TYPES OF ANIMAL TISSUES EPITHELIAL TISSUE Covers and protects body surfaces Lines organs and cavities TISSUES Functions in absorption, secretion, and filtration A group of cells that have similar structure and Skin, lining of the digestive tract, glands that function together as a unit. Plants and Animals are made up of cells and NERVOUS TISSUE tissues. Receives, processes, and transmits information Coordinates body functions TYPES OF PLANT TISSUES Enables sensation and movement Examples: brain, spinal cord, nerves MUSCLE TISSUE Enables movement Generates force Maintains posture Three types: skeletal muscle, cardiac muscle, smooth muscle PARENCHYMA - Thin-walled cells involved in photosynthesis, storage, and other metabolic functions. Commonly found in leaves. CONNECTIVE TISSUE COLLENCHYMA - Thick-walled cells providing Supports and binds other tissues support and flexibility to young plant parts. Provides structure and protection Commonly found in stem, petioles, and leaf veins. Stores energy SCLERENCHYMA - Thick-walled cells Examples: bone, cartilage, blood, adipose tissue providing rigidity and strength to plant parts. Commonly found mature regions of plants (Stem, Fruit, Seed, Roots, and Leaves).  CELL CYCLE The cell cycle is the series of events that a cell goes through as it grows, replicates its DNA, and divides into two daughter cells. It is a crucial process that allows organisms to grow, repair damaged tissues, and reproduce. WHAT ARE THE PHASES OF EUKARYOTIC CELL CYCLE? CELL MODIFICATION Interphase Adaptations or changes acquired by the cell G1 after cell division that aids the cell in various S PHASE beneficial ways. G2 Mitotic Phase CILIA - Hair -like organelles extending from the PMAT(C) cell surface. FLAGELLA - Long, whip -like, tail -like WHAT HAPPENS DURING INTERPHASE? structures made of protein filaments. Aids in movement. VILLI OR MICROVILLI - Small, slender, vascular, finger-like projections. Increases surface area to increase absorption. PSEUDOPODS - “False feet”. Temporary extension of cytoplasm. Movement and ingestion (Phagocytosis - cell eating).  IMPORTANCE OF DNA REPLICATION DNA replication is essential to the cell cycle because it ensures that each daughter cell gets an exact copy of the genetic material. Without DNA replication, cells would not have the correct genetic information, leading to HOW THE CELL CYCLE REGULATED? malfunction, disease, or cell death. MITOSIS MEIOSIS What would happen if mitosis and meiosis did not occur in living things? Lack of Growth and Repair (Mitosis) No Reproduction (Mitosis and meiosis) Potential Accumulation of Genetic mutations Stagnation of Evolutionary Processes DISORDERS AND DISEASES FROM CELL CYCLE MALFUNCTIONS 1. RB1 and Retinoblastoma SYNAPSIS AND CROSSING OVER The RB1 gene produces a protein that acts KEY CONCEPTS: as a brake during the G1 phase of the cell Synapsis is the connecting of homologous cycle, preventing the cell from entering the chromosomes to form a tetrad. S phase prematurely. If the RB1 gene is Crossing over is the sharing of genetic material mutated, this brake fails, leading to between two nonsister chromatids in a uncontrolled cell division and the homologous pair. development of Retinoblastoma, a type of KEY TERMS: eye cancer Tetrad 2. ATM Gene and Ataxia-Telangiectasia Recombinant chromosomes The ATM gene is responsible for detecting and repairing DNA damage during the S phase. Defects in the ATM gene prevent proper DNA repair, leading to cell malfunction and death. This results in Ataxia-telangiectasia, characterized by neurological issues, weakened immune systems, and an increased risk of cancer. 3. Xeroderma Pigmentsum and Skin Cancer Individuals with Xeroderma Pigmentosum have a defective DNA repair process during the G2 phase, specifically for UV-induced damage. This leads to the accumulation of DNA damage, increasing their risk of developing skin cancer due to their extreme sensitivity to sunlight. 4. Chromosomal Instability and Cancer During the M phase, chromosomal instability (CIN) occurs when errors in chromosome segregation led to an abnormal number of chromosomes (aneuploidy). These errors can drive the development of various cancers by creating genetic imbalances that promote uncontrolled cell growth. Bypassing Cell Cycle Checkpoints and Cancer Bypassing cell cycle checkpoints allows cells to continue dividing despite DNA damage or other errors. This uncontrolled cell growth is a hallmark of cancer, as the checkpoints that normally ensure healthy cell division are evaded, leading to the proliferation of abnormal cells. STRUCTURAL COMPONENTS OF CELL MEMBRANE Phospholipid Bilayer - Phospholipids are the primary building blocks of the cell membrane. Each phospholipid molecule has a hydrophilic (water- attracting) "head" and two hydrophobic (water- repelling) "tails." CELL MEMBRANE The cell membrane, also known as the plasma membrane, is a crucial structure that surrounds the cell, providing it with structural support and regulating the movement of substances in and out of the cell. KEY PROPERTIES OF CELL MEMBRANE Selective Permeability - The membrane selectively allows certain substances to pass while blocking others. Fluid Mosaic Model - Describes the membrane as a flexible, dynamic structure where lipids and proteins move laterally within the layer, giving the membrane a fluid nature. Cholesterol - This lipid molecule is interspersed within the phospholipid bilayer. It helps to stabilize the membrane's fluidity, making it less permeable to very small water- soluble molecules that might otherwise pass freely through. Proteins Integral Proteins - These span the entire membrane and can act as channels or transporters for molecules to pass through. Peripheral Proteins - These are attached to the exterior or interior surfaces of the membrane and often play roles in signaling or maintaining the cell's shape. Carbohydrates - Carbohydrates are attached to proteins (glycoproteins) or lipids (glycolipids) on the extracellular surface of the membrane. These carbohydrate chains play a key role in cell recognition, signaling, and adhesion. Glycocalyx (Sweet Husk) - The glycocalyx is a fuzzy- appearing coating around the membrane formed by the carbohydrate portions of glycoproteins and glycolipids. It protects the cell, facilitates cell-cell communication, and helps in immune responses. Cytoskeleton Filaments - The inner surface of the membrane is often supported by cytoskeletal filaments (such as actin) that attach to membrane proteins, providing structural support and helping to maintain the cell's shape.