Biology Notes 2024-2025 PDF

BIOLOGY Semester | A.Y. 2024-2025 Microorganism Prevention: The twists and bends in the necks COURSE OUTLINE t...

BIOLOGY Semester | A.Y. 2024-2025 Microorganism Prevention: The twists and bends in the necks COURSE OUTLINE trapped microorganisms. I. Cell Theory II. Cell Organelles Predictions: III. Cell Cycle IV. Cell Modifications Sterility: Sterilized broth remains V. Animal Tissues and Plant Tissues sterile if the swan necks are intact. VI. Transport Mechanism Contamination: If the necks are VII. Endocytosis vs. Exocytosis broken, microorganisms from the air can contaminate the broth, leading to microbial growth. Cell Theory States that all organisms are composed of similar units of Outcome: organization called cells. Support for Pasteur’s Theory: Spontaneous Living things come from non Confirmed that microorganisms, not Generation living things. a "life force," are responsible for microbial growth in the broth. SPONTANEOUS GENERATION ➔ Francisco Redi proved that CELL THEORY macroorganisms do not spontaneously generate through his ➔ Theodor Schwann and Matthias controlled experiment of three jars Schleiden are credited with coming (Open jar, Gauze-covered jar, Sealed up with the Cell Theory. Jar) ➔ 1. All organisms are made of cells. ➔ Pasteur proved that microorganisms do not spontaneously generate. ➔ 2. All existing cells are produced by other living cells. (No spontaneous Experiment Design: generation) Swan-Neck Flasks: Flasks with long, ➔ 3. The cell is the most basic unit of twisted necks. life. Boiled Broth: Sterilized to kill microorganisms. ➔ These were discovered between Purpose: 1665-1838. Air Exchange: Allowed air to enter ★ Key Note - it took over 173 years for without letting airborne the CELL THEORY to be formulated. microorganisms in. LECTURE # | COURSE – TITLE CONTRIBUTORS TO THE CELL THEORY ➔ 4. The activity of an organism ★ The Cell Theory would not exist if it depends on the total activity of wasn’t for the development of the independent cells. microscope and the work of others. ➔ 5. Energy flow (metabolism and biochemistry) occurs within cells. ★ Janssen - invented the first compound microscope ➔ 6. Cells contain DNA which is found specilically In the chromosome and ★ There are 5 contributors: the RNA found in the cell nucleus and cytoplasm. ★ Robert Hooke (1665) - used a compound microscope to observe ➔ 7. All cells are basically the same in cork, coined the term “cell” from chemical composition in organisms Latin ‘cellula’ which means small of simllar specles. compartment. ➔ 8. Heredity Information (DNA) is passed on from cell to cell. ★ Anton van Leeuwenhoek - used a single lens microscope to observe ➔ 9. All cells have the same basic live cells in a sample of pond water, chemical composition. called cells animacules (plants & ➔ 10. All living organisms are composed animals). of and depend on cells to function normally. ★ Matthias Schleiden - projected plants are made of cells. TYPES OF CELLS ★ Theodor Schwann - determined all ★ Cell - smallest unit that is capable of animals are made of cells. Published performing life functions. the 1st statement of the CT. Two types of Cells: ★ Rudolf Virchow - stated all cells - Prokaryotic - Do not have come from pre-existing cells (2nd membrane bound organelles. statement of CT) Few internal structures. One-celled organisms, MODERN CELL THEORY Bacteria. ➔ 1. All known living things are made up - Eukaryotic - Contain of one or more cells. membrane bound organelles. ➔ 2. All living cells arise from Most living organisms. pre-existing cells by division. Multicellular. ➔ 3. The cell is the fundamental unit of PARTS OF THE CELL (ORGANELLES) structure and function in all living ★ Organelles - small specialized organisms. structure inside of a cell. LECTURE # | COURSE – TITLE Surrounding the Cell ★ Mitochondria - produces energy through chemical reactions - ★ Cell Membrane - Outer membrane of breaking down fats & carbohydrates. cell that controls movement in and Controls level of water and other out of the cell. Phospholipid bilayer materials in the cell. Recycles and (Hydrophilic head, Hydrophobic tail) decomposes proteins, fats, and carbohydrates. ★ Cell Wall - most commonly found in plant cells & bacteria. Supports & ★ Golgi bodies - protein ‘packaging protects cells. plant’. Move materials within the cell. Move materials out of the cell. Inside the Cell ★ Lysosome - digestive ‘plant’ for ★ Nucleus - Directs cell activities. proteins, fats, and carbohydrates. Separated from cytoplasm by Transports undigested material to nuclear membrane. Contains genetic cell membrane for removal. Cell material - DNA. breaks down if lysosome explodes. ★ Nuclear Membrane - Surrounds ★ Vacuoles - membrane-bound sacs nucleus. Made of two layers. for storage, digestion, and waste Openings allow material to enter and removal. Contains water solution. leave the nucleus. Help plants maintain shape. ★ Chromosomes - In the nucleus, ★ Chloroplast - usually found in plant made of DNA, contain instructions for cells, contains green chlorophyll, traits & characteristics. where photosynthesis takes place. ★ Nucleolus - Inside the nucleus, PLANTS & ANIMAL TISSUES contains RNA to build proteins. ★ Tissues - form organs which ★ Cytoplasm - gel-like mixture, combine to allow organisms to exist. surrounded by cell membrane, A group of cells, in close proximity, contains hereditary material. organized to perform one or more specific functions. ★ Endoplasmic Reticulum - moves materials around in the cell. Smooth ★ Histology - study of cells, tissues and type: lacks ribosomes. Rough type: organs as seen through the micro- ribosomes embedded in the surface. scope. It also includes cellular detail down to the molecular level that can ★ Ribosomes - each cell contains be observed using an electron thousands, make proteins, found on microscope. ribosomes & floating throughout the cell. LECTURE # | COURSE – TITLE 3 MAJOR TYPES OF PLANT TISSUES regulate their opening and closing. Plant Tissues can be classified by following ways. ○ Epidermis - the exchange of matter between the plant and I. On the basis of the part of the plant they the environment. are present. (a) the epidermis on above ground organs (leaves ★ Dermal Tissue - covers the outside of and stems) is involved a plant in a single layer of cells called with gas exchange. the epidermis. (b) the epidermis on below ground organs (roots)is ○ Epidermal cells secrete a waxy involved with water and substance called cuticle, ion uptake. which coats, waterproofs, and protects the aboveground GROUND TISSUE parts of plants. Location: Makes up much of the interior ○ Tissue Types: of a plant. Pavement Cells: Large, Functions: irregularly shaped Basic Metabolic Functions: Supports parenchymal cells various metabolic processes. without chloroplasts. Support: In stems, ground tissue Function: Form provides structural support. the majority of Storage: the epidermis ○ Stems: Stores food and water. and are involved ○ Roots: Stores food. in swelling and ○ Parenchyma shrinking by ○ Collenchyma osmosis. Stomata: Tiny pores in VASCULAR TISSUE the epidermis that control the exchange of ★ Vascular tissue - runs through the gases (oxygen and ground tissue inside a plant. carbon dioxide). ○ Xylem Guard Cells: ○ Phloem Bean-shaped sclerenchyma cells that II. On the basis of kind of cells they contain surround stomata and LECTURE # | COURSE – TITLE SIMPLE PERMANENT TISSUES Difference between Meristematic and Permanent Tissues PARENCHYMA TISSUE 1. They are living cells, polygonal, round Meristematic Tissue Permanent Tissue or irregular in shape. The cells have thin cell walls. 1. Capable of 1. Lost power of cell division cell division 2. Have large intercellular spaces in between the cells. 2. Undifferentiate 2. Differentiated cells 3. Forms the basic ground tissue and d Cells stores food. 3. Have not 3. Have attained 4. When the cells contain chlorophyll, attained definite form and size they can carry photosynthesis and definite form and size. are called chlorenchyma. 5. In aquatic plants they contain air 4. Dense and 4. Thin layer of cavities to help the plant to remain abundant cytoplasm around cytoplasm vacuole (if living) afloat, there they are called aerenchyma. 5. Always living 5. May be living or 6. In stems and roots they may store dead. nutrients. 7. Example: Caladium Plant and Taro Plant COLLENCHYMA TISSUE 1. They are living cells, round, oval and elongated in shape. The cells have cell walls thickened unevenly at the corners. LECTURE # | COURSE – TITLE 2. Have little or no intercellular spaces Cell Structure: as the corners of cell walls are ○ Consists of dead cells. thickened with pectin. ○ Lacks end walls between 3. Present below the epidermis in leaves adjacent cells. and stems. ○ Side walls are thick and 4. They give mechanical support to the reinforced with lignin (stiff and plant. water-proof). 5. Can carry photosynthesis if Phloem: chlorophyll is present. Function: Transports food (sugar dissolved in water) from SCLERENCHYMA TISSUE photosynthetic cells to other parts of 1. They are dead cells, long and narrow the plant for growth or storage. cells, appear angular in cross section. Cell Structure: The cells have highly thick cell walls. ○ Consists of living cells. 2. Cells do not have intercellular spaces ○ Cells are separated by end as the cell walls are thickened with walls with tiny perforations or lignin. Lignin is like a strong cement holes. that binds the cells together. Often there is no space and cytoplasm left PROTECTIVE TISSUES - EPIDERMIS AND CORK in the cells. 3. Present in the vascular bundles in Protective tissue covers the surface of xylem and phloem in stem, roots and leaves and the living cells of roots and in the veins of leaves. Also present in stems. Its cells are flattened with their top the hard seed coat covering. and bottom surfaces parallel. The upper 4. Provide strong mechanical support, and lower epidermis of the leaf are rigidity and flexibility to the plant. examples of protective tissue. 5. Cells are dead but are connected through the pits, pits are places ANIMAL TISSUES where lignin is absent. EPITHELIAL TISSUE (COVERING) COMPLEX PERMANENT TISSUES A. Naming or Classifying Epithelial Tissue: VASCULAR TISSUE 1. First Name (Number of cell layers) Xylem: a. Simple b. Stratified Function: Transports water and c. Pseudostratified dissolved minerals from roots to 2. Second name (Cell Shape) stems and leaves. LECTURE # | COURSE – TITLE a. Cuboidal NERVOUS TISSUE (CONTROL) b. Squamous c. Columnar ➔ Tightly-joined closely-packed cells ➔ First to evolve during evolution and were first formed during embryonic development. ➔ One side of epithelium exposed to air or internal fluid, other side attached to a basement membrane, a dense - Senses stimuli and transmits signals mat of extracellular matrix called nerve impulses from one part (connective tissue) of an animal to another ➔ Covers the outside of the body and - Consists of a cell body and long lines the internal organs and cavities. extensions called dendrites (towards ➔ Barrier against mechanical injury, cell body) and axons (towards invasive microorganisms, and fluid another cell or an effector) loss. ➔ Provides surface for absorption, A. General Traits excretion and transport of molecules 1. Irritable 2. Conductive A. GENERAL TRAITS OR CHARACTERISTICS B. Two Cell Types 1. found on a 1. Neurons body surface A. Cell Body either internal B. Axon or external C. Dendrite 2. tightly 2. Glia Cells (caretakers) packed cells MUSCLE TISSUE (MOVEMENT) 3. free border or free surface A. General Traits 4. rest on a 1. Excitable Tissue basement 2. Can shorten membrane 3. Composed of long cells called 5. Nonvascular muscle fibers 4. Contraction →movement B. Types of Muscle Tissue 1. Skeletal Muscle A. Multinucleate LECTURE # | COURSE – TITLE B. Voluntary 4. Analogy C. Striated 2. Smooth Muscle AREOLAR CONNECTIVE TISSUE-LOOSE A. Involuntary IRREGULAR B. Visceral C. Structure 3. Cardiac Muscle-Mixture of Two A. One nucleus/cell B. Autorythmic C. Striated AAATENDON-DENSE REGULAR D. Intercalated Disc CONNECTIVE TISSUE (FRAMEWORK) ➔ Main function: binding and support other tissues ➔ Large amount of extracellular matrix with fewer cells ➔ Connective tissue cells secrete the extra-cellular matrix ➔ Extracellular matrix consists of LIGAMENT network of fibers in liquid, jelly-like or solid matrix BONE A, Common Traits 1. Possess fibers BLOOD 2. Widely scattered cells 3. Ground tissue (matrix) LECTURE # | COURSE – TITLE Characteristics: Contain ~30% water and exhibit minimal metabolic activity. CILIA AND FLAGELLA Cilia ADIPOSE TISSUE Structure: Hairlike projections extending from the cell body. Types: ○ Motile Cilia: Sweep mucus and particles (e.g., in bronchi and trachea). ○ Non-Motile Primary Cilium: Present on all mammalian cells; serves sensory functions. MEMBRANES A. Cutaneous B. Mucous 1. Function: Movement of materials and contain glands 2. open to outside C. Serous 1. sensing environmental changes. occur in paired sheets 2. don’t open to outside 3. Number: Numerous per cell. no glandular tissue Flagella CELL MODIFICATIONS Structure: Long, whip-like projections. 1. SPORES Types: Present in bacteria, archaea, and eukaryotes. ENDOSPORES Function: Propel single cells (e.g., Definition: Dormant structures swimming of protozoa and sperm). produced by some bacteria to Role in Prokaryotes: Movement survive harsh conditions. toward light, oxygen, or nutrients. Examples: Bacteria causing anthrax Number: Typically one or two per cell. and tetanus. Spore Formation: Defense PILI mechanism against heat, pressure, Structure: Hairlike projections made stress, chemicals, and UV radiation. of proteins. Survival: Can last for many years in Function: soil and other inanimate objects. ○ Attachment: Help bacteria Activation: Transform into active adhere to surfaces. bacteria when conditions become ○ Conjugation: Act as bridges favorable. for plasmid transfer between LECTURE # | COURSE – TITLE cells, facilitating genetic 6. ROOT HAIRS exchange (e.g., antibiotic Structure: Tiny, hair-like extensions resistance). growing from the surface of plant Role: Adhere to tissue surfaces and roots. assist in host cell invasion. Function: 4. DENDRITES AND AXONS OF THE NERVE CELLS Water and Nutrient Absorption: Collect water and mineral nutrients Dendrites: from the soil. Transport: Take the nutrient-rich Quantity: Several per neuron. solution up through the roots to the Function: Receive signals (impulses) rest of the plant. from other neurons. Conduction: Transmit these signals to the cell body of the neuron. 7. ENUCLEATED RED BLOOD CELL Axons: Red blood cells (RBCs, Red Cells,Red Blood Corpuscles, Erythrocytes) - Quantity: One per neuron. transport oxygen and carbon dioxide Structure: Long and thin. in the blood. Function: Carry nerve impulses away ○ Hemoglobin - iron-containing from the cell body to other neurons biomolecule that can bind and muscles. oxygen and is responsible for the blood’s red color. ○ Bends more than a nucleated 5. ACTIN AND MYOSIN one and can fit through Muscle Fibers - consist of many narrower capillaries. smaller units called myofibrils. Myofibrils - consist of even smaller 8. MICROVILLI units, myosin (thick filaments) and Microvilli (singular: microvillus) - actin (thin filaments) which are microscopic cellular membrane protein filaments. protrusions that increase the surface ○ These filaments slide past one area of cells for absorption. another as the muscle Thousands of microvilli form a contracts and expands for structure called the brush border that organism activity. is found on the apical surface of some epithelial cells, like those in small intestine. LECTURE # | COURSE – TITLE CELL CYCLE DNA Polymerase: Life of a eukaryotic cell: The way the Adds DNA cells grow, make new copies and nucleotides to divide. both strands (A Happens in all of somatic (body) pairs with T, C cells in order to get the same DNA pairs with G). inside each cell. Outcome: Results Regular sequence of growth and in two exact division that eukaryotic cells undergo. copies of the DNA. Prokaryotic cells are through binary G2 Phase: Prepares for fission. division and checks for STAGES: IPMATC errors. 2. Mitosis: CELL DIVISION ○ Purpose: Distribution of replicated DNA into two Cell Division daughter cells. ○ Outcome: Each daughter cell Cell Origin: All cells come from receives an identical copy of pre-existing living cells. the parent cell’s DNA. Growth and Replacement: Cells grow 3. Cytokinesis: by increasing in size and number; ○ Function: Division of the they also divide to replace old or cytoplasm and organelles dead cells. between the two new cells. Cell Cycle Stages Chromosome Information 1. Interphase: Diploid Cells: ○ Duration: Largest phase, where ○ Definition: Cells with two sets 95% of cell growth occurs. of chromosomes. ○ Functions: ○ Chromosome Count: 2n = 46 G1 Phase: Cell growth (23 pairs in humans). and development; differentiation (cell's role ○ PROPHASE is determined). S Phase (Synthesis): Prophase: DNA replication. Process: Chromosomes: Visible as two Helicase: Unzips chromatids joined at the centromere. the DNA double Nuclear Envelope: Begins to dissolve. helix. LECTURE # | COURSE – TITLE Centrioles: Present and start forming Telophase spindle fibers. Chromosome Location: Sister Prometaphase chromatids reach opposite poles of the cell. Nuclear Envelope: Completely Nuclear Envelope: Reforms around fragments and dissolves. each set of chromosomes. Spindle Fibers: Chromosomes: Uncoil and become ○ Kinetochore Microtubules: less visible. Attach to kinetochores at the Spindle Fibers: Disappear. centromeres of chromatids. Cleavage Furrow: Forms in animal ○ Non-Kinetochore cells, indicating the start of Microtubules: Extend from cytokinesis. centrosomes and overlap at the cell equator. Cytokinesis Kinetochores: Specialized centers at the centromere where spindle fibers Definition: Division of the cytoplasm. attach. Result: Two separate daughter cells, each with an identical nucleus. Metaphase Animal Cells: Microfilaments pinch the cell into two. Chromosomes: Line up along the Plant Cells: A cell plate forms middle (equatorial plane) of the cell. between the two daughter nuclei. Nuclear Envelope: Completely gone (no nucleus) Key Terms Spindle Fibers: Extend from opposite poles towards the chromosomes. Chromosomes: Structures containing genetic information made of DNA. Anaphase Chromatin: DNA and proteins that make up chromatid. Chromosome Separation: Spindle Chromatid: Each chromosome fibers pull chromosomes toward consists of two identical chromatids opposite poles. joined at the centromere. Chromatid Separation: Centromere: The point where Chromosomes split into two sister chromatids are joined. chromatids, which are now individual Genes: DNA segments that code for chromosomes. proteins. LECTURE # | COURSE – TITLE Additional Information Historical Discovery Human Somatic Cells: Have 23 pairs 1882: Pierre-Joseph van Beneden of chromosomes, called homologous discovered different chromosome chromosomes. numbers in different cells, leading to Chromosome Formation: Chromatin understanding of meiosis. condenses into chromosomes during mitosis; the centromere is created Gametes during the S phase of interphase. Males: Meiosis produces 4 sperm cells. Females: Meiosis produces 1 viable egg and 3 polar bodies. ○ Polar Bodies: Give up their cytoplasm to nourish the single viable egg. Timing of Meiosis Males: Meiosis begins at puberty and continues throughout life. Females: Meiosis begins before birth; all eggs are produced before birth, and they mature starting at puberty. Meiosis Purpose: Produces sex cells (haploid FERTILIZATION gametes) with half the number of chromosomes compared to somatic Fusion of gametes cells. Van Beneden proposed that an egg Outcome: Four daughter cells, each and a sperm fuse to produce a with half the chromosome number of zygote. the original cell. The zygote contains two copies of Chromosome Number: each chromosome (one copy from ○ Diploid (2n): Contains two sets the sperm and one copy from the of chromosomes (46 in egg). These are called homologous humans). chromosomes. ○ Haploid (n): Contains one set of chromosomes (23 in humans). LECTURE # | COURSE – TITLE REDUCTION DIVISION exchanged between nonsister or sister chromatids. This increases Cells undergoes 2 rounds of cell genetic variation which is why division: Meiosis 1 and Meiosis 2 siblings look different. They only contain half the number of chromosomes as somatic cells. METAPHASE I The homologous chromosomes line UNIQUE FEATURES OF MEIOSIS up in the center of the cell and are Feature #1 - Synapsis - homologous still held together. chromosomes pair all along their length. Feature #2 - Crossing Over - ANAPHASE I exchange of genetic material from Spindle fibers shorten homologous chromosomes which Homologous chromosomes are causes genetic variation. separated but the sister chromatids Feature #3 - Reduction Division - are still paired. chromosomes are not copied in Independent assortment - random between the two divisions. One half of chromosomes move to each pole; the genetic material only. MEIOSIS 1 Preceded by TELOPHASE I Interphase-chromosomes are Nuclear membrane reforms around replicated to form sister chromatids. each daughter nucleus. Sister chromatids are genetically Each new cell now contains two sister identical and joined at centromere. chromatids that are NOT IDENTICAL Single centrosome replicates, due to crossing over. forming 2 centrosomes. AT THE END OF MEIOSIS I, PROPHASE I 2 cells with each containing a haploid Individual chromosomes first # of chromosomes. becomes visible. No DNA replication. ○ Homologous chromosomes Meiosis II resembles normal, mitotic become closely associated in division. synapsis. ○ Crossing over occurs. MEIOSIS 2 Crossing over is a complex series of events in which DNA segments are LECTURE # | COURSE – TITLE PROPHASE II Multicellular - cell cycle is how they become an adult from only one Nuclear membrane breaks down fertilized zygote cell. again. CELL CYCLE IN MULTICELLULAR ORGANISMS METAPHASE II GROWTH: increase in number of cells Chromosomes line up in the middle and the size of cells ( interphase G1) of the cell. DIFFERENTIATION: cells are told by a gene to become specialized (ex. ANAPHASE II Muscle cells are told to do that job) Spindle fibers shorten and the sister MORPHOGENESIS: the patterned chromatids move to opposite poles. formation of specialized cells to become TISSUES TELOPHASE II CELL DIVISION IN EUKARYOTES Nuclear envelope re-forms around the four sets of daughter Chromosomes and Chromatin chromosomes. Chromosomes: Consist of a AT THE END OF MEIOSIS II, DNA-protein complex called chromatin. 4 haploid cells Chromatin: No two of these haploid cells are alike ○ Composition: DNA and due to crossing over (genetically proteins. unique). ○ Proteins: Includes histones, CHROMOSOME NUMBER which help in coiling DNA into dense, visible structures called Chromosome number is unique to chromatids. each kind of organism and all cells (except sex cells) have the same kind Mitosis and number of chromosomes. This is why the chromosome number Purpose: Duplicates chromosomes in sex cells must be reduced in half into pairs of sister chromatids. by meiosis. Precision: Duplication is highly accurate, with only about 1 error in IMPORTANCE OF THE CELL CYCLE 100,000. Chromatid Distribution: Each pair of Unicellular - cell cycle is how they sister chromatids is separated and reproduce offspring sent to opposite poles of the cell. LECTURE # | COURSE – TITLE Cell Cycle they do not pass the restriction point. Interphase: ○ Characteristics: Cells are in a ○ Duration: Accounts for about non-dividing, resting state. 90% of the cell cycle. Cell Size: ○ Activities: Cell growth, DNA ○ Requirement: Ratio of replication, and preparation cytoplasm to genome must be for division. high enough to proceed past M Phase (Mitosis): the restriction point. ○ Duration: Accounts for about ○ Importance: Ensures the cell 10% of the cell cycle. has sufficient resources and ○ Activities: Actual division of genetic material to support the cell into two daughter cells. successful division. CONTROL OF CELL DIVISION THE MITOTIC CLOCK Cues for Cell Cycle Regulation Cell Cycle Phases: G1, S, G2, M Growth Factors: (mitosis) ○ Function: Bind with membrane Protein Kinases - rhythmic changes receptors to promote cell in regulatory proteins that division. synchronize cell cycle events. Density-Dependent Inhibition: Phosphorylation - activates or ○ Influences: Affected by inhibits the target protein’s activity. available nutrients and space. Cyclins: Regulatory proteins. ○ Effect: Cells stop dividing when Produced throughout the cell cycle, they reach a certain density. accumulates during interphase. Restriction Point: Cyclin-Dependent Kinases (Cdks): ○ Location: G1 phase of the cell Protein kinases that regulate cell cycle. cycles. Concentration stay the same ○ Significance: The 'point of no throughout the cell cycle but activity return' after which the cell is varies. committed to enter the S Maturation Promoting Factor (MPF): phase. Cyclin-Cdk complex which peaks in ○ Outcome: If the cell passes this concentration with the peak in cyclin. point, it must proceed to DNA MPF: Initiates mitosis synthesis (S phase). Cyclin Accumulation: Peaks during G0 Phase: interphase ○ Definition: A state of stasis where cells exit the cell cycle if LECTURE # | COURSE – TITLE Cyclin Destruction: At end of mitosis, covered; they grow back if cyclin is degraded cells are removed. CANCER CELLS CELL CYCLE REGULATORS Cancer Cells: Lack division control Cyclins: Response to Controls: Do not respond to ○ Discovery: Identified in the standard cellular controls 1980s; present in dividing cells. Transformation: Process by which normal ○ Function: Cyclins initiate cell cells become cancerous division when introduced to Immune System: Typically destroys non-dividing cells. cancerous cells INTERNAL CELL REGULATORS Tumors: ○ Function: Respond to internal Benign Tumor: Cells remain localized events; enforce checkpoints. Malignant Tumor: Cells spread ○ Examples: (metastasis) Chromosome Cancer Causes: Alteration of genes replication must be controlling cell division (p53) complete before division. REGULATING THE CELL CYCLE Chromosomes must be attached to mitotic Rate of Cell Division: fibers for anaphase. ○ Non-Dividing Cells: Muscle and nerve cells typically do not EXTERNAL CELL REGULATORS divide after creation. ○ Function: Respond to external ○ Constantly Dividing Cells: Skin, signals; can speed up or slow bone marrow, and digestive down the cell cycle. cells cycle every ~4 hours. ○ Growth Factors: Stimulate cell CONTROLS ON CELL DIVISION growth and division, crucial during development and Controls on Cell Division: healing. ○ Contact Inhibition: Cells stop ○ Surface Molecules: Can inhibit dividing when they touch other cell growth. cells. ○ Petri Dish Experiments: Cells UNCONTROLLED CELL GROWTH cover the dish but stop Cancer: growing when the surface is LECTURE # | COURSE – TITLE ○ Characteristics: Cells lose oxygen (O₂), carbon dioxide growth control; do not respond (CO₂), and glycerol. to regulatory signals. 2. Facilitated Diffusion ○ Tumors: Result from ○ Definition: Passive transport of uncontrolled growth; can molecules across the cell damage surrounding tissue. membrane with the help of ○ Causes: membrane proteins. Smoking ○ Molecules Involved: Large, Radiation exposure polar molecules and ions that Viral infections cannot freely cross the ○ Gene p53: Defects in p53 gene phospholipid bilayer. impair cell cycle control, ○ Transport Proteins: preventing proper response to Channel Proteins: Form growth signals. pores allowing specific Disruptions: molecules or ions to ○ Rapid Activation: If cell cycle pass. genes and enzymes activate Carrier Proteins: Bind to too quickly, it leads to molecules and change uncontrolled cell growth, i.e., shape to shuttle them cancer. across the membrane. 3. Osmosis CELL TRANSPORT ○ Definition: Movement of water Purpose: Movement of materials into molecules across a and out of the cell for nutrient uptake, semi-permeable membrane waste elimination, gas exchange, and from low solute concentration cell signaling. to high solute concentration. ○ Purpose: To equalize solute TRANSPORT MECHANISMS concentrations on either side of the membrane. 1. Diffusion ○ Mechanism: Water moves to ○ Definition: Net movement of balance solute concentrations, molecules from a region of essentially the diffusion of free high concentration to low water molecules. concentration. 4. Active Transport ○ Nature: Passive, occurs along ○ Definition: Movement of a concentration gradient until molecules against the equilibrium is achieved. concentration gradient from ○ Examples: Small, nonpolar, low to high concentration. lipophilic molecules like  LECTURE # | COURSE – TITLE ○ Requirement: Requires energy encapsulate membrane to from ATP. extracellular release their ○ Purpose: Allows cells to obtain material and contents into the nutrients and remove waste bring it into the extracellular that cannot pass through the cell. space. membrane by other means. ○ Secondary Active Transport: Types - Phagocytosis: - Regulated Uses electrochemical Cellular eating, Exocytosis: gradients to move molecules, where large Requires external similar to diffusion but driven particles or cells signals to trigger by ion gradients. are engulfed. the fusion of vesicles with the ENDOCYTOSIS VS. EXOCYTOSIS - Pinocytosis: membrane. Cellular drinking, where small - Constitutive Feature Endocytosis Exocytosis particles and Exocytosis: fluids are taken Continuous in. process that Definition The process of The process of does not require taking particles or moving - specific signals. substances into substances out Receptor-mediat the cell by of the cell by ed Endocytosis: engulfing them in fusing vesicles Specific a vesicle. with the plasma molecules bind to membrane. receptors, leading to internalization. Purpose - Absorbing - Removing nutrients for toxins or waste cellular function products Examples - White blood - Neurons cells releasing - Eliminating - Repairing the (macrophages) neurotransmitter pathogens cell membrane engulfing and s into the destroying synaptic cleft. - Disposing of old - Facilitating bacteria. or damaged cells communication - Cells expelling between cells - Cells taking in waste products nutrients like or toxins. glucose. Mechanism Involves the Involves vesicles formation of fusing with the vesicles that plasma  LECTURE # | COURSE – TITLE cannot pass through the plasma Steps 1. Cell membrane 1. Vesicle forms in membrane by simple diffusion or folds inward to the endoplasmic active transport. form a vesicle. reticulum or Endocytosis helps cells acquire Golgi apparatus. 2. Vesicle engulfs nutrients, remove pathogens, and extracellular 2. Vesicle travels manage cell turnover. material. to the plasma Exocytosis enables cells to expel membrane. waste, secrete signaling molecules, 3. Vesicle and maintain or repair the plasma detaches and 3. Vesicle fuses membrane. moves into the with the plasma cell. membrane. 4. Vesicle may 4. Contents are fuse with released into the lysosomes for extracellular content space. processing. 5. Vesicle may be incorporated into the membrane or separated. Energy Yes, requires Yes, requires Requirement energy (active energy (active transport). transport). Vesicle Vesicles are Vesicles are Formation formed by the formed by inward folding of budding from the plasma the Golgi membrane. apparatus or endoplasmic reticulum. IMPORTANCE OF BULK TRANSPORT Endocytosis and exocytosis are crucial for transporting large molecules, particles, or fluids that