Download Cells And Membranes Lecture

The Cell
Cells are Us—Nothing to Write
Cells are Us—Nothing to Write
Cilia on a protozoan.
Sperm meets egg.
Cells are Us
• A person contains about 100
trillion cells.
• There are about 200
different cell types in
mammals.
• Cells are tiny, ave.
diameter about 0.002 cm
(20 um) . That’s about
1250 cells per inch.
Red and
white blood
cells above
vesselforming cells.
nerve cell
The Cell Theory
The Cell Theory (proposed independently in 1838 and
1839) is a cornerstone of biology.
*All organisms are composed of one or more cells.
*Cells are the basic unit of structure and function.
* Cells arise only by division of previously existing
cells.
All organisms living today are descendents of an
ancestral cell.
A Sense of Scale and Abundance – Bacteria on the
Head of a Pin---Nothing to Write
Two Different Types of Cells
A prokaryotic cell
A eukaryotic cell
Prokaryotes
and
EukaryotesMake this
chart on
your paperno pictures
An Idealized Animal Cell
Plant Cell
Why Study Cells?
Cells  Tissues  Organs 
Organ Systems→Bodies
– bodies are made up of cells
– cells do all the work of life!
The Work of Cells
What jobs do cells have to do for an organism to live?…
• “breathe” -gas exchange: O2 in vs. CO2 out
• Eat-take in & digest food
• make energy-ATP
• build molecules-proteins, carbs, fats, nucleic acids
• remove wastes
• control internal conditions-homeostasis
• respond to external environment
• build more cells-growth, repair, reproduction &
development
The Job of Cells
• Cells have 3 main jobs
– make energy
• need energy for all activities
• need to clean up waste produced
while making energy
– make proteins
• proteins do all the work in a cell,
need lots of them
– make more cells
• for growth
• replace damaged or diseased cells
The Plasma Membrane – Gateway to the Cell
The Plasma Membrane is Selectively permeable
The physical properties of phospholipids account for membrane
assembly and many of its properties.
Small molecules and larger hydrophobic molecules move through.
Ions, hydrophilic molecules larger than water, and large molecules
such as proteins do not move through the membrane on their own.
Plasma Membrane Functions
Maintain a high concentration of materials in the cell.
Keep harmful materials out.
Control the movement of materials into and out of the cell.
Let the cell sense its
environment.
Membrane Components
Phospholipids
Proteins (peripheral and integral)
Cholesterol
Carbohydrates
Proteins Are Critical to Membrane Function
Transport Processes - Diffusion
Solutes move
down a
concentration
gradient until
even
distribution.
This is
diffusion.
Molecules move from high conc. to low conc. until
balance is achieved-Equilibrium. Diffusion of water=
Osmosis
Three Forms of Transport Across the Membrane
Three Forms of Transport Across the Membrane
Example: Oxygen or
water diffusing into a
cell and carbon dioxide
diffusing out.
*Passive
Three Forms of Transport Across the Membrane
Examples: Glucose or amino
acids moving from blood into a
cell.
*Passive
Three Forms of Transport Across the Membrane
Examples: Pumping Na+
(sodium ions) out and K+
(potassium ions) in against
strong concentration gradients.
*Active
Effects of Osmosis on Water
Balance
• Osmosis is the diffusion of water across a
selectively permeable membrane
• Water diffuses across a membrane from the
region of lower solute concentration to the
region of higher solute concentration
• This will “dilute” the higher concentration.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 7-12
Lower
concentration
of solute (sugar)
Higher
concentration
of sugar
H2O
Selectively
permeable
membrane
Osmosis
Same concentration
of sugar
Water Balance of Cells Without
Walls
• Isotonic solution: Solute concentration is the
same as inside the cell; no net water movement
across the plasma membrane
• Hypertonic solution: Solute concentration is
greater than inside the cell; cell loses water, will
shrivel.
• Hypotonic solution: Solute concentration is less
than inside the cell; cell gains water, expands.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 7-13
Hypotonic solution
H2O
Isotonic solution
Hypertonic solution
H2O
H2O
H2O
(a) Animal
cell
Lysed
H2O
Normal
H2O
Shriveled
H2O
H2O
(b) Plant
cell
Turgid (normal)
Flaccid
Plasmolyzed
Moving the “Big Stuff”
Exocytosis:
moving
things out.
Molecules are moved out of the cell by vesicles that fuse with the
plasma membrane.
Hormones secretion and nerve cells communication.
Exocytosis
Exocytic vesicle
immediately after fusion
with plasma membrane.
Moving the “Big Stuff”
Large molecules move in via one of two forms of endocytosis.
Pinocytosis
This is the most common form of endocytosis.
Pinocytosis takes up most proteins and other large molecules.
Pinocytosis
pinocytic vesicles forming
mature transport vesicle
Transport across a capillary cell (blue).
Endocytosis – Phagocytosis Transports Large Particles
Phagocytosis About to Occur
The Threshold
of Phagocytosis
- Capture of a
Yeast Cell
(yellow) by
Membrane
Extensions of
an Immune
System Cell
(blue)
The End!!
It’s Crowded In There
An artist’s conception of the cytosol - the region of a cell
that’s not in the nucleus or within an organelle.
Path of products (protein) in cell
• Ribosome, endoplasmic reticulum, golgi,
vesicle, plasma membrane, destination.
Animal and Plant Cells Have More
Similarities Than Differences
What Do Those Parts Do?
We’ll start
by seeing
what role
these parts
play in
making and
moving
proteins.
A Focus of Our Tour of the
Cell: The Path of Protein
Synthesis and Export
The
Nucleus
Think of the nucleus as the
cell’s control center.
Two meters of
human DNA fits
into a nucleus
that’s 0.000005
meters across.
Ribosomes and the Endoplasmic Reticulum
The Rough Endoplasmic Reticulum
Functions:
Protein synthesis
(about half the cell’s
proteins are made
here).
Protein movement
(trafficking)
Protein
“proofreading”
The Golgi Apparatus (or Complex)
Think of the Golgi apparatus as a busy airport receiving passengers
(proteins) and sending them to their destinations.
The Golgi Apparatus
Note how protein cargo
moves in vesicles.
Proteins moved through the
Golgi apparatus can travel to
the lysosome, the plasma
membrane, or outside the cell.
Proteins moved through the Golgi apparatus travel to the lysosome, the plasma
membrane, or outside the cell.
Off the Path of Protein Production: Lysosomes, Mitochondria,
Chloroplasts and the Cytoskeleton
The Lysosome
Functions:
Digesting food or cellular
invaders
Recycling cellular components
Cell suicide (suicide is bad
for cells, but good for us!)
Many diseases (e.g. TaySachs) are caused by
lysosome malfunction
(The lysosome is not found in
plant cells)
The
Lysosome
This bacterium
about to be
eaten by an
immune system
cell will spend
the last minutes
of its existence
within a
lysosome.
The Mitochondrion
Think of the mitochondrion as the
powerhouse of the cell.
Both plant and animal cells
contain many mitochondria.
(Mitochondria is the
plural of mitochondrion)
The Mitochondrion
A class of diseases that
causes muscle weakness
and neurological disorders
are caused by
malfunctioning
mitochondria.
Worn out mitochondria may be an important factor in aging.
Animal vs. Plant Cells – Chloroplasts Are a Big
Part of the Difference
Two Other Differences
Cells In a Leaf
A Consequence of Cell Walls –
the Great Strength of Woody
Plants
The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
Only plants have chloroplasts, but animals reap the benefits too.
The Cytoskeleton
The name is misleading.
The cytoskeleton is the
skeleton of the cell, but
it’s also like the
muscular system, able to
change the shape of
cells in a flash.
An animal cell cytoskeleton
The Cytoskeleton in Action
Cilia on a protozoan.
Beating sperm tail at fertilization.