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Chapter 4 Physiology of Cells. Movement through cell membranes. Substances move through cell membranes in two ways: Passive Transport: does not require any energy activity from the cell membrane Active Transport: requires expenditure of metabolic energy by the cell. PASSIVE TRANSPORT.

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movement through cell membranes
Movement through cell membranes
  • Substances move through cell membranes in two ways:
    • Passive Transport: does not require any energy activity from the cell membrane
    • Active Transport: requires expenditure of metabolic energy by the cell
passive transport
  • Diffusion:
    • The spreading of molecules from an area of high concentration to an area of low concentration
    • Simple Diffusion: molecules travel across the phospholipidbilayer
      • Makes the membrane permeable.


    • Diffusion of water through a selectively permeable membrane
    • Osmotic Pressure
      • Develops from the water pressure during Osmosis
        • Potential Osmotic Pressure-the maximum osmotic pressure that could develop when separated from pure water by a selectively permeable membrane
  • Isotonic
    • Two fluids have the same osmotic pressure
  • Hypertonic
    • Water flows out of the cell and the cell shrivels as a result
    • Solute concentration greater outside of the cell
  • Hypotonic
    • Water flows into the cell and the cell swells up as a result
    • Solute concentration greater inside the cell


    • Selectively permeable membrane separates larger solute particles into smaller solute particles
  • Facilitated Diffusion
    • Transports substances down a concentration gradient
    • The collision energy of the solute provides required energy
active transport
Active Transport

movement of solute particles from an area of low concentration to high

concentration and up a concentration gradient by the use of a carrier molecule

  • Endocytosis- bringing extracellular material into the cell
    • Phagocytosis- large particles engulfed by the plasma membrane and fuse with lysosomes, where the particles are digested
    • Pinocytosis- fluid and the substances dissolved in it enter the cell
  • Exocytosis- large molecules (proteins) are pulled by the cytoskeleton and leave the cell through the plasma membrane

This is one of multiple images that display receptor-mediated endocytosis.

cell metabolism
Cell Metabolism

the chemical reactions that occur within the cell

  • ENZYMES – a protein that changes the rate of a chemical reaction
    • Structure
      • Proteins
      • Lock-and-Key Model: active site where the enzyme molecule fits into the substrate molecule
    • Chemical catalysts
      • Speed up reaction by reducing the amount of energy needed to start reaction
    • Regulate cell metabolism
    • Continually destroyed and replaced
    • Catalyze a chemical reaction in both ways

CATABOLISM – operates on the pathway of cellular respiration (breakdown of glucose to carbon dioxide and water)

    • Glycolysis
      • Net yield of 2 ATP
      • Anaerobic (does not require oxygen)
      • Occurs outside mitochondria
      • Glucose is broken down into pyruvic acid molecules and that energy is transferred into ATP and NADH
    • Citric Acid Cycle
      • Also known as Krebs Cycle
      • Net yield of 2 ATP
      • Pyruvic acid is converted into acetyl and enters the cycle after losing CO2 and transferring some energy into NADH, ATP, and FADH2
      • Occurs inside the inner chambers of the mitochondria
    • Electron Transport System (ETS)
      • Net yield of 32 ATP
      • Energized electrons are embedded in the cristae of the mitochondria

ANABOLISM – protein synthesis

    • Deoxyribonucleic acid (DNA)
      • Shape of a double helix
      • Polymer (large molecule made up of many smaller molecules) made up of nucleotides
      • Genes contains the codes for synthesizing one polypeptide
    • Transcription
      • mRNA forms along a segment of DNA to copy a portion of the DNA code and undergoes editing
    • Translation
      • mRNA links with a ribosome
      • tRNA transfers amino acids to the ribosome
      • Joined by peptide bonds which then eventually produces an entire polypeptide chain
cell growth reproduction
Cell Growth/Reproduction
  • Cell Life Cycle.
  • Kind of important… just a tiny bit.
  • Humans are simple people.
  • So 2 phases.
cell growth
Cell Growth
  • Cell is already made. Start here.
  • Produce Cytoplasm and Plasma Membrane
    • Protein Synthesis (anabolic process)
      • Amino Acids to Polypeptide to larger more comple
  • = structural proteins and Enzymes
dna replication
DNA Replication
  • RNA synthesized by enzyme
  • Larger cell triggers mechanisms
  • Synthesizes entire set of DNA
  • Steps of synthesis?
  • Before Reproduction: Chromatids attached by Centromere
cell reproduction
Cell Reproduction.
  • No, cells do not have sex to reproduce.
  • 1 parent cell = 2 daughter cells.
  • Cytokinesis
  • Mitosis
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Meiosis
  • Haploid and Diploid