Cells: The Living Units

 

Cell Theory

•      basic structural and functional unit of life

•      organism’s activity depends on activity of cells

•      biochemical activities dictated by subcellular structure

•      life has a cellular basis

Structure of a Generalized Cell

    Plasma Membrane

•      separates intracellular fluids from extracellular fluids

•      plays a dynamic role in cellular activity

•      glycocalyx — cell recognition

        Fluid Mosaic Model

•      double bilayer of lipid; imbedded, dispersed proteins

•      phospholipids, cholesterol, and glycolipids

        Functions of Membrane Proteins

•      transport

•      enzymatic activity

•      receptors for signal transduction

•     intercellular adhesion

•      cell-cell recognition

•      attachment to cytoskeleton and extracellular matrix

        Membrane Junctions

•      tight junction

•      desmosome

•     gap junction

        Passive Membrane Transport

            Diffusion

•      simple diffusion

•      channel proteins

•      facilitated diffusion

•       protein carriers

            Osmosis

•     semipermeable membrane

•      osmolarity

            Filtration

•      hydrostatic pressure

            Tonicity

•      isotonic

•      hypertonic

•      hypotonic

        Active Transport

•      uses ATP

•      carrier proteins

•      symport system

•      antiport system

            Types of Active Transport

•      Primary active transport — phosphorylation

•      Secondary active transport — exchange pump (such as the Na⁺-K⁺–ATPase)

        Vesicular Transport

•    exocytosis

•   endocytosis

•    phagocytosis

•    bulk-phase endocytosis

•    receptor-mediated transport – uses clathrin-coated pits Chapter 3

        Membrane Potential

•      voltage across a membrane

•      resting membrane potential

•    ranges from –20 to –200 mV

        Cell Adhesion Molecules (CAMs)

•      anchor cells

•      assist in movement

•      recruit leukocytes

        Membrane Receptors

•      contact signaling

•      electrical signaling

•      chemical signaling

•      G protein-linked receptors – ligands; second messenger (cyclic AMP)

            Operation of a G protein

•      extracellular ligand

•      G protein

•      effector enzyme produces a second messenger

•      second messenger activates a kinase

•      activated kinase can trigger a variety of cellular responses

    Cytoplasm

•      cytoplasm

•      cytosol

•      organelles

•      inclusions

        Cytoplasmic Organelles

•     membranous

    •    mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, and Golgi apparatus

•      nonmembranous

    •    cytoskeleton, centrioles, and ribosomes

            Mitochondria

•      provide most of the cell’s ATP via aerobic cellular respiration

•      contain their own DNA and RNA

            Ribosomes

•      granules containing protein and rRNA

•      site of protein synthesis

•      free ribosomes

•      membrane-bound ribosomes

            Endoplasmic Reticulum (ER)

•      tubes and membranes enclosing cisternae

•      continuous with the nuclear membrane

•      rough ER and smooth ER

                Rough ER & the Signal Mechanism of Protein Synthesis

•      mRNA –  signal-recognition particle (SRP)

                Smooth ER

•    liver – lipid and cholesterol metabolism, breakdown of glycogen and, along with the kidneys, detoxification of drugs

•    In the testes – synthesis of steroid-based hormones

•    intestinal cells – absorption, synthesis, and transport of fats

•    skeletal and cardiac muscle – storage and release of calcium

            Golgi Apparatus

•      modification, concentration, and packaging of proteins

•      cis face

•     trans face

•      secretory vesicles

            Lysosomes

•      digestive enzymes

            Endomembrane System

•      System of organelles that function to:

•    Produce, store, and export biological molecules

•    Degrade potentially harmful substances

•   nuclear envelope, smooth and rough ER, lysosomes, vacuoles, transport vesicles, Golgi apparatus, and the plasma membrane

            Peroxisomes

•      oxidases and catalases

            Cytoskeleton

•      microtubules, microfilaments, and intermediate filaments

            Microtubules

•      tubulin

            Microfilaments

•     actin

            Intermediate Filaments

•      high tensile strength

            Centrioles

•      barrel-shaped organelles located in the centrosome near the nucleus

•      nine triplets of microtubules

•      mitotic spindle during mitosis

•      bases of cilia and flagella

            Cilia

 

        Nucleus

•      nuclear envelope, nucleoli, and chromatin

            Nuclear Envelope

•      selectively permeable double membrane barrier containing pores

•      nucleoplasm

            Nucleoli

•      dark-staining spherical bodies within the nucleus

•      site of ribosome production

            Chromatin

•      threadlike strands of DNA and histones

•      nucleosomes

        Cell Cycle

•      interphase

•    growth (G₁), synthesis (S), growth (G₂)  [G₀]

•      mitotic phase (M)

•    cytokinesis

•      helicase untwists the DNA double helix into two complementary nucleotide chains (replication bubble)

•      semiconservative replication

•      DNA polymerase

•      DNA ligase

•      histones associate with DNA and form chromatids that are united by a centromere

            Mitosis

•      prophase

•      metaphase

•      anaphase

•      telophase

            Cytokinesis

•      cleavage furrow

            Control of Cell Division

•      surface-to-volume ratio of cells

•      chemical signals such as growth factors and hormones

•      contact inhibition

•      cyclins and cyclin-dependent kinases (CDKs) complexes

        Protein Synthesis

•      DNA serves as master blueprint for protein synthesis

•      genes

•      triplets of nucleotide base specify coding for an amino acid

            Transcription

•      mRNA - transcription factors and RNA polymerase

•      codon

•      introns

            Translation

•      three types of RNA – mRNA, tRNA, and rRNA

        Protein Degradation

•      lysosomes

•      ubiquitin; proteasomes

    Extracellular Matrix