Anaphy

• Cell Theory:

  • Cell is the basic structural and functional unit of living organisms
  • The activity of an organism depends on the collective activities of its cells
  • Principle of complementarity: the biochemical activities of cells are dictated by their structure which determines their function
  • Continuity of life has a cellular basis
• Overview of Cellular Basis of Life:

  • Cells are composed of carbon, hydrogen, oxygen, and nitrogen
  • Cells are 60% water
  • A cell has three main regions: nucleus, cytoplasm, and plasma membrane
• The Nucleus:

  • Control center of the cell
  • Contains genetic material (DNA) needed for building proteins and cell reproduction
  • Three regions: nuclear envelope (membrane), nucleolus, chromatin
  • Nuclear envelope is a double membrane that bounds the nucleus and has nuclear pores for material exchange
  • Nucleolus has dark-staining nucleoli and is the site of ribosome assembly
  • Chromatin is composed of DNA found around histones, scattered throughout the nucleus, and condenses to form chromosomes during cell division
• The Plasma Membrane:

  • Transparent barrier for cell contents
  • Contains cell organelles and separates cell contents from the surrounding environment
  • Constructed of 2 layers of phospholipids, cholesterol, proteins, and sugar groups forming glycolipids
  • Role of proteins: enzymes, receptors, transport channels
  • Role of sugars: glycoproteins, glycocalyx
• Cell Membrane Junctions:

  • Tight Junctions: impermeable, bind cells together into leakproof sheets
  • Desmosomes: anchoring junctions, prevent cells from being pulled apart
  • Gap Junctions/Communicating Junctions: allow communication between cells
• The Cytoplasm:

  • Cellular material outside the nucleus and inside the plasma membrane
  • Site of most cellular activities, includes cytosol, inclusions, and organelles
  • Major components: cytosol, inclusions, organelles
• Organelles in the Cytoplasm:

  • Mitochondria: powerhouse of the cell, carry out reactions to produce ATP
  • Ribosomes: sites of protein synthesis
  • Endoplasmic Reticulum: fluid-filled tunnels/canals for substance transport, rough ER synthesizes proteins
  • Golgi Apparatus: modifies and packages proteins from the rough ER
• Lysosomes:

  • Membranous bags containing digestive enzymes
  • Digest worn-out cell structures and house phagocytes

  Peroxisomes:

  • Membranous sacs of oxidase enzymes, detoxify harmful substances
  • Break down free radicals and replicate by budding from ER
• Cytoskeleton:

  • Network of protein structures throughout the cytoplasm
  • Determines cell shape, supports organelles, and provides machinery for transport
  • Three elements: microfilaments, intermediate filaments, microtubules

  Centrioles:

  • Rod-shaped bodies made of microtubules, generate microtubules and direct cell division
• Cell Extensions:

  • Cilia: move materials across cell surface
  • Flagella: propel the cell, enables movement
  • Microvilli: increase surface area for absorption
• Cell Diversity:

  • There are 200 different cell types varying in size, shape, and function
  • Cells reflect function in their size and shape
• Cells with Specialized Functions:

  • Fibroblast, Erythrocyte, Epithelial Cell, Skeletal Muscle & Smooth Muscle Cells, Fat Cells, White Blood Cells, Nerve Cell, Oocyte, Sperm
• Cell Physiology:

  • Cells can metabolize, digest food, dispose waste, reproduce, grow, move, respond to stimulus
• Membrane Transport:

  • Two basic methods: active and passive transport
  • Cells transport nutrients and materials through membrane transport
• Definition of Terms:

  • Solution: a homogenous mixture of two or more components
• Basic methods of transport: active and passive
• Passive transport: substances are transported across membranes without any input from the cell, don't need energy
• Passive processes include diffusion and filtration
• Diffusion:

  • Molecule movement from high concentration to low concentration gradient
  • Particles tend to distribute evenly
  • Kinetic energy causes molecules to move randomly
  • Size of molecule and temperature affect this process
  • Molecules can pass through if small enough, lipid-soluble, or assisted by membrane carriers
  • Three types: simple diffusion, osmosis, facilitated diffusion
• Osmosis:

  • Unassisted process where solutes are lipid-soluble or small enough to pass through membrane pores
  • Simple diffusion of water across plasma membranes
• Facilitated diffusion:

  • Transport lipid-insoluble and large substances
  • Glucose is transported by protein membrane channels or protein molecules acting as carriers
  • Highly polar water molecules easily cross through aquaporins
  • Water moves down its concentration gradient
• Filtration:

  • Water and solutes are forced through a membrane by fluid or hydrostatic pressure
  • Pressure gradient pushes solute-containing fluid from high-pressure to low-pressure area
  • Critical for kidneys to work properly
• Active transport: ATP is used to move substances across membranes
• Active processes are used when substances are too large, lipid-insoluble, or need to move against a concentration gradient
• Active processes include active transport and vesicular transport
• Active transport:

  • Amino acids, sugars, ions are transported by a protein carrier (solute pumps)
  • ATP energizes solute pumps
  • Substances are moved against concentration gradients
  • Sodium-Potassium Pump is important for nerve impulse
• Vesicular transport:

  • Substances are moved across membranes in bulk without actually crossing the plasma membrane
  • Two types: exocytosis and endocytosis
• Exocytosis:

  • Mechanism in cells to secrete hormones, mucus, and others
  • Vesicles are membranous sacs that carry materials and are emptied outside
  • Docking proteins on vesicles bind the plasma membrane
• Endocytosis:

  • Extracellular substances are enclosed or engulfed in a vesicle
  • Vesicle detaches from the plasma membrane and moves into the cell
  • Vesicle fuses with a lysosome for digestion
  • Two types: phagocytosis and pinocytosis
• Cell division:

  • Cell life cycle involves a series of changes from formation to division
  • Preparations include DNA replication
  • Two major periods: interphase and cell division (mitotic division)
• Process of DNA Replication:

  • DNA uncoils into two nucleotide chains serving as a template
  • Nucleotides are complementary (adenine bonds with thymine, guanine bonds with cytosine)
• Events of Cell Division:

  • Mitosis and cytokinesis occur together
  • Cytoplasm is not divided in some cells, leading to binucleate or multinucleate cells
  • Mitosis results in the formation of two daughter nuclei and consists of four phases: Prophase, Metaphase, Anaphase, Telophase
• Cytokinesis:

  • Division of the cytoplasm that begins when mitosis is near completion
  • Formation of two daughter cells with a cleavage furrow
• Protein synthesis:

  • DNA is the blueprint for making proteins
  • Gene is a DNA segment carrying the blueprint for building one protein or polypeptide chain
• Varieties of RNA:

  • Transfer RNA (tRNA) transfers amino acids to the ribosome
  • Ribosomal RNA (rRNA) helps form the ribosomes
  • Messenger RNA (mRNA) carries instructions for building proteins from the nucleus to the ribosome
• Phases of Protein Synthesis:

  • Transcription transfers information from DNA to mRNA
  • Translation translates the base sequence of nucleic acid to an amino acid sequence
  • Involves three varieties of RNA: tRNA, rRNA, mRNA
• Translation:

  • Occurs in the cytoplasm and involves the three varieties of RNA
  • Steps include mRNA leaving the nucleus, incoming tRNA recognizing complementary mRNA codons, ribosomes adding new amino acids to the protein chain, and released tRNA reentering the cytoplasmic pool