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Lecture Presentations for Integrated Biology and Skills for Success in Science Banks, Montoya, Johns, & Eveslage. Week # 9 Lecture – pp 129-133. Expectations for the course. Community Working with others—in class, in lab, in study groups Learning

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Lecture Presentations for Integrated Biology and Skills for Success in ScienceBanks, Montoya, Johns, & Eveslage

Week # 9 Lecture – pp 129-133

expectations for the course
Expectations for the course
  • Community
    • Working with others—in class, in lab, in study groups
  • Learning
    • Complete all assignments for deep comprehension
  • Respect
    • Fellow students, instructors and self
guiding principles for the course
Guiding Principles for the Course
  • Looking at seemingly simple things deeply
  • Conceptual understanding
  • Practical Applications
  • Contextualized
transport mechanisms organelles
Transport Mechanisms, Organelles,
  • By the end of the lecture today, students will be able to:
    • Explain the importance of and describe the processes of diffusion, osmosis, facilitated diffusion and active transport.
    • Describe which types of membrane transports require energy and which do not require energy.
    • List the major organelles in a eukaryotic cell and describe their major roles in the cell.
membrane transport
Membrane Transport
  • plasma membrane – a barrier and a gateway between the cytoplasm and ECF
    • selectively permeable – allows some things through, and prevents other things from entering and leaving the cell
  • passive transport mechanisms requires no ATP
    • random molecular motion of particles provides the necessary energy
    • diffusion, osmosis, facilitated diffusion
  • active transport mechanisms consumes ATP
    • active transport and vesicular transport
simple diffusion
Simple Diffusion
  • Simple Diffusion – the net movement of particles from area of high concentration to area of low concentration
    • due to their constant, spontaneous motion
  • Also known as movement down the concentration gradient – concentration of a substance differs from one point to another




  • Osmosis - flow of water from one side of a selectively permeable membrane to the other
    • from side with higher water concentration to the side with lower water concentration
    • reversible attraction of water to solute particles forms hydration spheres
    • makes those water molecules less available to diffuse back to the side from which they came
  • Aquaporins- channel proteins specialized for passage of water


Side A

Side B

(a) Start

facilitated diffusion
Facilitated Diffusion
  • facilitated diffusion – passive transport of solute through a membrane down its concentration gradient
  • does not consume ATP
  • solute attaches to binding site on carrier, carrier changes confirmation, then releases solute on other side of membrane




The solute binds to a receptor

site on the carrier and the

carrier changes conformation.

The carrier releases the

solute on the other side of

the membrane.


A solute particle enters

the channel of a membrane

protein (carrier).



active transport
Active Transport
  • active transport – carrier-mediated transport of solute through a membrane up (against) its concentration gradient
  • ATP energy consumed to change carrier
  • Examples of uses:
    • sodium-potassium pump keeps K+ concentration higher inside the cell
    • bring amino acids into cell
    • pump Ca2+ out of cell
sodium potassium pump
Sodium-Potassium Pump
  • each pump cycle consumes one ATP and exchanges three Na+ for two K+
  • keeps the K+ concentration higher and the Na+ concentration lower with in the cell than in ECF
  • necessary because Na+ and K+constantly leak through membrane
    • half of daily calories utilized for Na+ - K+ pump


3 Na+ out



Intracellular fluid

2 K+ in






the cell interior
The Cell Interior
  • structures in the cytoplasm
    • organelles, cytoskeleton, and inclusions
    • all embedded in a clear gelatinous cytosol
  • Organelles – internal structures of a cell that carry out specialized metabolic tasks
    • membranous organelles – those surrounded by one or two layers of unit membrane
      • nucleus, mitochondria, lysosome, peroxisome, endoplasmic reticulum, and Golgi complex
    • organelles not surrounded by membranes
      • ribosome, centrosome, centriole, basal bodies
  • Largest organelle (5 m in diameter)
    • most cells have one nucleus
    • a few cells are anuclear or multinucleate
  • nuclear envelope - two unit membranes surround nucleus
    • perforated by nuclear pores formed by rings of protein
      • regulate molecular traffic through envelope
      • hold two unit membranes together
  • nucleoplasm – material in nucleus
    • chromatin (thread-like matter) composed of DNA and protein
    • nucleoli – one or more dark masses where ribosomes are produced
endoplasmic reticulum
Endoplasmic Reticulum
  • endoplasmic reticulum - system of interconnected channels called cisternae enclosed by unit membrane
  • rough endoplasmic reticulum – composed of parallel, flattened sacs covered with ribosomes
    • continuous with outer membrane of nuclear envelope
    • produces the phospholipids and proteins of the plasma membrane
    • synthesizes proteins that are packaged in other organelles or secreted from cell
endoplasmic reticulum1
Endoplasmic Reticulum
  • smooth endoplasmic reticulum
    • lack ribosomes
    • cisternae more tubular and branching
    • cisternae are thought to be continuous with those of rough ER
    • synthesizes steroids and other lipids
    • detoxifies alcohol and other drugs
    • manufactures all membranes of the cell
  • rough and smooth ER are functionally different parts of the same network
  • Ribosomes - small granules of protein and RNA
    • found in nucleoli, in cytosol, and on outer surfaces of rough ER, and nuclear envelope
  • they ‘read’ coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code
golgi complex
Golgi Complex
  • Golgi complex - a small system of cisternae that synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis
    • receives newly synthesized proteins from rough ER
    • sorts them, cuts and splices some of them, adds carbohydrate moieties to some, and packages the protein into membrane-bound Golgi vesicles
      • some become lysosomes
      • some migrate to plasma membrane and fuse to it
      • some become secretory vesicles for later release
  • Lysosomes - package of enzymes bound by a single unit membrane
    • extremely variable in shape
  • Functions
    • intracellular hydrolytic digestion of proteins, nucleic acids, complex carbohydrates, phospholipids, and other substances
    • autophagy – digest and dispose of worn out mitochondria and other organelles
    • autolysis – ‘cell suicide’ – some cells are meant to do a certain job and then destroy themselves
  • mitochondria – organelles specialized for synthesizing ATP
  • variety of shapes – spheroid, rod-shaped, kidney bean-shaped, or threadlike
  • surrounded by a double unit membrane
    • inner membrane has folds called cristae
    • spaces between cristae are called matrix
      • matrix contains ribosomes, enzymes used for ATP synthesis, small circular DNA molecule – mitochondrial DNA (mtDNA)
  • “Powerhouses” of the cell
    • energy is extracted from organic molecules and transferred to ATP



Outer membrane

Inner membrane








Outer membrane

Inner membrane




1 µm

exit quiz
Exit Quiz
  • 1). What transport mechanism is responsible for moving water molecules from an area of high concentration to low concentration?
  • 2). In order for active transport mechanism to work there must be an input of what molecule? Why this molecule?
  • 3). What part of the nucleus is responsible for producing rRNA (ribosomes)?
  • 4). What organelle is responsible for modifying proteins after they are synthesized?
  • 5). Why is the mitochondria known as the “powerhouse of the cell”?