Bio 101 cell biology

BIO 101 - CELL BIOLOGY

Introduction

  • Biology is the study of living things.

  • Encompasses various aspects:

    • Cellular basis of living things

    • Energy metabolism underlining life activities

    • Genetic basis for inheritance

    • Evolutionary relationships among organisms

    • Diversity of life on Earth

  • Covers microorganisms, plants, and animals.

  • Integrates structural and functional relationships of life activities.

  • Draws on chemistry and physics for foundational principles.

  • Divided into practical and theoretical biology.

Categories of Biology

Practical Biology

  • Includes areas like:

    • Plant breeding

    • Wildlife management

    • Medical science

    • Crop production

Theoretical Biology

  • Comprises fields such as:

    • Physiology (study of function)

    • Biochemistry (chemistry of organisms)

    • Taxonomy (classification)

    • Ecology (study of populations and interactions with environments)

    • Microbiology (study of microscopic organisms)

Cell Theory

  • Tenets of cell theory:

    • All living things are composed of cells.

    • Cells are the basic units of life.

    • All cells arise from preexisting cells.

  • Historical context:

    • Robert Hooke (1665) observed cork, naming cells.

    • Anton Van Leeuwenhoek observed living cells (animalcules).

    • Matthias Schleiden (1838) proposed all plants are made of cells.

    • Theodor Schwann (1839) stated all animals are made of cells.

    • Rudolf Virchow (1858) concluded all cells arise from existing cells.

Definition of a Cell

  • Cell: smallest unit of life responsible for all life processes.

    • Structural, functional, and biological unit of living beings.

    • Size ranges from 0.0001extmm0.0001 ext{ mm} to almost 150extmm150 ext{ mm} across.

    • Capable of independent replication, hence known as building blocks of life.

    • Contains cytoplasm enclosed by a membrane, housing organelles and biomolecules (proteins, nucleic acids, lipids).

    • Organisms can be unicellular or multicellular.

Discovery of Cells

  • Significant advancements in science:

    • Understanding all organisms made of cells.

    • Studying structure and function of cells enhances life comprehension.

Characteristics of Cells

  • Cells provide structural support and convert nutrients into energy.

  • Variations in shape and size like bricks in a building.

  • Components of Cells:

    • Organelles performing specialized functions.

    • Hereditary material in the nucleus.

  • Cells represent the lowest level of organization in life.

Functions of Cells

Supports and Structures

  • Cells form the basis structure in organisms (e.g., skin, xylem in plants).

Growth (Mitosis)

  • Cell division increases cell number.

Transport of Substances

  • Nutrient import and waste export via transport mechanisms:

    • Passive Transport: small molecules move along concentration gradient.

    • Active Transport: larger molecules require energy to move.

Energy Production

  • Energy produced through photosynthesis (plants) and respiration (animals).

Reproduction

  • Mitosis (asexual) leads to identical daughter cells.

  • Meiosis results in genetically diverse offspring.

Types of Cells

Prokaryotes

  • Simpler and older; single-celled organisms.

  • Examples: bacteria and archaebacteria.

  • Characteristics:

    • Cell membrane and possibly a cell wall.

    • Single round chromosome, no nucleus.

    • Can have plasmids (extra genetic material).

Eukaryotes

  • More complex; multidimensional organisms (plants, animals, fungi).

  • Compartments and internal structures like nucleus and organelles.

  • Complexity:

    • Multicellular cooperation.

    • Extensive internal organization.

Cell Structure

  • Components include cell wall, membrane, cytoplasm, nucleus, organelles.

Cell Membrane

  • Protective and selectively permeable.

  • Separates internal and external environments.

Cell Wall

  • Rigid structure found in plants, composed of cellulose.

  • Provides support and protection.

Cytoplasm

  • Jelly-like substance where reactions occur.

Nucleus

  • Contains hereditary material (DNA), controls cell activities.

Organelles and Their Functions

Vacuole

  • Maintains rigidity and storage in plant cells.

Lysosome

  • Contains enzymes for digestion; cleans and protects cell.

Endoplasmic Reticulum (ER)

  • Site for protein synthesis; two types: smooth and rough.

    • Smooth ER: Synthesizes lipids and detoxifies.

    • Rough ER: Studded with ribosomes; synthesizes proteins.

Ribosomes

  • Sites of protein synthesis.

  • Exist free in cytoplasm or bound to ER.

Golgi Apparatus

  • Modifies, sorts, and packages proteins for secretion.

Mitochondria and Chloroplasts

  • Mitochondria: energy production through oxidation.

  • Chloroplasts: photosynthesis in plants.

Microtubules

  • Support and transport system for cells; essential for movement (e.g., cilia, flagella).

Intercellular Communication

Plasmodesmata

  • Channels allowing communication between plant cells.

Cell Organelles and Their Functions

  • Nucleolus: Ribosome production; regulates cell activities.

  • Nuclear Membrane: Protects nucleus, regulates molecule transport.

  • Chromosomes: 23 pairs in humans, crucial for inherited traits.

Differences Between Plant and Animal Cells

  • Plant cells possess cell walls, chloroplasts, and large vacuoles.

  • Animal cells have centrioles and are more irregular in shape.

Cell Division and Growth

Cell Cycle

  • Phases: Interphase (G1, S, G2) and Mitosis.

    • G1: Cell growth.

    • S: DNA replication (92 chromosomes).

    • G2: Preparation for division.

Mitosis

  • Divided into phases: Prophase, Metaphase, Anaphase, Telophase.

Cytokinesis

  • Animal cells form cleavage furrow; plant cells form cell plates.

Meiosis

  • Reduction division; original diploid cell reduces to four haploid cells.

  • Phases: Meiosis I (homologous chromosomes separate) and Meiosis II (sister chromatids separate).

Classification of Living Things

  • Characteristics of Living Things:

    • Organized structure, requires energy, capable of reproduction, growth, metabolism, responds to stimuli, movement, and death.

  • Classification Levels: Kingdom, Phylum, Class, Order, Family, Genus, Species.

  • Five Kingdoms: Monera, Protista, Fungi, Plantae, Animalia.

  • Domains: Bacteria, Archaea, Eukarya.

    • Genetic similarities have changed classifications over time.

Bacteria and A Bacteria: Prokaryotes, diverse in metabolism, essential for ecosystems, can be pathogenic.

  • Archaea: Extremophiles, resemble eukaryotes more than bacteria.

Kingdom Protista

  • Diverse eukaryotic organisms; subdivided into algae and protozoa.

Kingdom Fungi

  • Major decomposers; unique structure (hyphae, mycelium); reproduction by spores.

Kingdom Plantae

  • Autotrophic multicellular organisms; undergo photosynthesis; classified into vascular and nonvascular.

Kingdom Animalia

  • Invertebrates (without backbones) and vertebrates (with backbones).