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
 Complete all assignments for deep
comprehension
 Respect
 Fellow students, instructors and self
Guiding Principles for the Course
 Looking at seemingly simple things deeply
 Conceptual understanding
 Practical Applications
 Contextualized
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
 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 – 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
Cy.
Down
gradient
Up
gradient
Osmosis
 Osmosis - flow of water from one side
of a selectively permeable membrane to
the other
 from side with higher water concentration to
.
Side A
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
(a) Start
Side B
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
.
ECF
ICF
1 A solute particle enters
3-10
the channel of a membrane
protein (carrier).
2 The solute binds to a receptor
site on the carrier and the
carrier changes conformation.
3 The carrier releases the
solute on the other side of
the membrane.
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
 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+
3 Na+ out
constantly leak through membrane
 half of daily calories utilized for
Extracellular
fluid
Na+ - K+ pump
ATP
ADP + P i
Intracellular fluid
2 K+ in
http://www.youtube.com/watch?v=RPAZvs4hvG
A
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
Nucleus
 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 - 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 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
 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 - 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
 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
Mitochondrion
 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
3-24
Matrix
Outer membrane
Inner membrane
Mitochondrial
ribosome
Intermembrane
space
Crista
Mitochondrion
Matrix
Outer membrane
Inner membrane
Mitochondrial
ribosome
Intermembrane
space
Crista
1 µm
3-25
http://www.youtube.com/watch?v=aczbMlSMr8U
Exit Quiz
 1).
 2).
 3).
 4).
 5).
What transport mechanism is responsible for moving water
molecules from an area of high concentration to low
concentration?
In order for active transport mechanism to work there must
be an input of what molecule? Why this molecule?
What part of the nucleus is responsible for producing rRNA
(ribosomes)?
What organelle is responsible for modifying proteins after
they are synthesized?
Why is the mitochondria known as the “powerhouse of the
cell”?