Download Chapter 3: Cells

Chapter 3: Cells
Lectures by Mark Manteuffel, St. Louis Community College
Learning Objectives
Be able to describe:
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what a cell is & two main classes of cells.
structure & functions of cell membranes.
how molecules move across membranes.
how cells are connected & communicate
with each other.
9 important landmarks in eukaryotic cells.
Cell Theory
1.  All living organisms are made up of
one or more cells.
2.  All cells arise from other pre-existing
cells.
Cells
  most
basic units of organism
  can function independently
  perform all necessary life functions
  reproduce themselves.
All cells are either
A.  Prokaryotic cells = prokaryotes
–  NO nucleus (DNA free in cell)
–  first cells on earth
B. Eukaryotic cells = eukaryotes
-  Have a nucleus (contains cell’s DNA)
-  & other organelles
The 2 main classes of cells
1. Prokaryotic cells
a)  bacteria
b)  archaebacteria
2. Eukaryotic cells
a)  protists
b)  plants
c)  fungi
d)  animals
Eukaryotic cells have organelles.
Endosymbiosis Theory
Explains presence of 2 organelles in eukaryotes
  mitochondria in plants & animals.
  chloroplasts in plants & algae
endosymbiosis
invagination
What determines whether a protein resides on the
surface or extends through the bilayer?
4 primary types of membrane proteins
each performs a different function.
The Plasma Membrane
Fluid Mosaic
In addition to proteins and phospholipids,
two other molecules are found in the plasma
membrane:
1.  Short, branched carbohydrate chains
2.  Cholesterol
All can move laterally in membrane
3.7 Membrane surfaces have a
fingerprint that identifies the cell.
  Cells
with an improper fingerprint are
recognized as foreign and are attacked by
your body’s defenses.
Why is it extremely
unlikely that a person
will catch HIV from
casual contact—such as
shaking hands—with an
infected individual?
Membrane proteins
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act as receptors or channels
help molecules into & out of cell
–  send signals into cell & nucleus
–  communicate with other cells
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act as enzymes
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catalyze reactions on inner & outer cell
surfaces
Why are plasma membranes such
complex structures?
They perform several critical functions.
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Take in food & nutrients
Dispose of waste products
Build & export molecules
Regulate heat exchange
Regulate flow of materials in & out of cell
3-6. Faulty membranes can cause
disease.
3.8 Passive transport is the
spontaneous diffusion of molecules
across a membrane.
There are two types of passive transport:
1.  Diffusion
2.  Osmosis
Diffusion and Concentration Gradients
•  Solutes
•  Solvents
Simple Diffusion
Facilitated Diffusion
  Most
molecules can’t get through plasma
membranes on their own.
  Channels
  Carrier molecules
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Transport proteins
Defects in Transport Proteins
  Can
reduce or even bring facilitated
diffusion to a complete stop
  Serious
  Many
health consequences
genetic diseases
•  Cystinuria and kidney stones
3.9 Osmosis is the
passive diffusion of
water across a
membrane.
Cells in Solution
  Tonicity
•  The relative concentration of solutes outside of
the cell relative to inside the cell
Hypertonic
Hypotonic
Isotonic
The Direction of Osmosis
only by a difference in total
concentration of all the molecules
dissolved in the water
  Determined
  It
does not matter what solutes they are.
Two distinct types of active transport:
1.  Primary
2.  Secondary
(Differ only in the source of the fuel)
Primary Active Transport:
Uses Energy Directly from ATP
Secondary Active Transport
  An
indirect method many transporter
proteins use for fueling their activities
  The
transport protein simultaneously
moves one molecule against its
concentration gradient while letting
another flow down its concentration
gradient.
Secondary Active Transport
  No
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ATP is used directly.
energy from ATP was used to pump one
of the molecules involved against their
concentration gradient.
then that molecule crosses with its
gradient
and helps the other across against its
gradient
3.11 Endocytosis and exocytosis
are used for bulk transport of
particles.
Many molecules are just too big to get
into a cell by passive or active transport.
Three types of endocytosis:
1.  Phagocytosis
2.  Pinocytosis
3.  Receptor-mediated endocytosis
3.12 Connections between cells
hold them in place and enable them
to communicate with each other.
  Involves
numerous types of protein and
glycoprotein adhesion molecules
Tight Junctions
  form
continuous, water-tight seals around
cells and also anchor cells in place
  particularly
important in the small intestine
where digestion occurs
Desmosomes
  are
like spot welds or rivets that fasten
cells together into strong sheets
  function
like Velcro®: they hold cells
together but are not water-tight
  found
in much of the tissue-lining cavities
of animal bodies
Gap Junctions
pores surrounded by special proteins that form
open channels between two cells
Gap junctions are an important mechanism
for cell-to-cell communication.
Plasmodesmata
  Tube-like
channels connecting the cells to
each other and enabling communication
and transport between them
  Consider
a plant as one big cell?
The nucleus
the largest and most prominent organelle in
most eukaryotic cells.
has two primary functions:
genetic control center
storehouse for hereditary information
Chromatin
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a mass of long, thin fibers consisting of DNA
wound around proteins (histones)
packs DNA into nucleus tightly
when a gene is expressed
DNA unwinds
 open to nuclear machinery  RNA
RNA gets shipped out to cytoplasm
Nucleolus
area near the center of the nucleus
where subunits of the ribosomes are
assembled
  an
  Ribosomes
are little protein factories.
3.14 Cytoplasm and cytoskeleton:
the cell s internal environment,
physical support, and movement
Take-home message 3.14
  The
inner scaffolding of the cell, which is
made from proteins, is the cytoskeleton.
  It
consists of three types of protein
fibers―microtubules, intermediate
filaments, and microfilaments.
Cytoskeleton: Three Chief Purposes
Cilia and Flagellum
3.15 Mitochondria:
the cell s energy converters
Bag-within-a-Bag Structure:
the intermembrane space and the matrix
Which cell type contains the most
mitochondria per cell?
1.  Liver
2.  Muscle
3.  White blood cell
4.  Dermal cell
5.  White adipose cell
6.  Red blood cell
Please insert Figure 3-31
Take-home message 3.15
  In mitochondria, the energy contained within
the chemical bonds of carbohydrate, fat, and
protein molecules is converted into carbon
dioxide, water, and ATP—the energy source
for all cellular functions and activities.
  Mitochondria may have their evolutionary
origins as symbiotic bacteria living within
other cells.
3.16 Lysosomes are the cell s garbage
disposals.
Lysosomes
round, membrane-enclosed, acid-filled
vesicles that function as garbage disposals
The Endomembrane System
3.17 Endoplasmic reticulum: where
cells build proteins and disarm toxins
Rough Endoplasmic Reticulum
The Smooth Endoplasmic Reticulum
3.18 Golgi apparatus: Where the cell
processes products for delivery
throughout the body
3.19 The cell wall
provides additional
protection &
support for plant
cells.
3.20 Vacuoles:
multipurpose
storage sacs for
plant cells
The central vacuole can play an important
role in five different areas of plant life:
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Nutrient storage
Waste management
Predator deterrence
Sexual reproduction
Physical support
3.21 Chloroplasts: the plant cell s
power plant
The stroma and
interconnected
little flattened
sacs called
thylakoids
Endosymbiosis Theory Revisited
  Chloroplasts
bacteria
  Circular
  Dual
resemble photosynthetic
DNA
outer membrane
3.3 Eukaryotic cells have compartments
with specialized functions.