Chapter 3 - Cells Complete Student Version

advertisement
Early Earth Review
Early Earth
3 Possibilities for Origin of Life
•
•
•
ET origin
Divine/Supernatural
Evolution – from inanimate & inorganic
matter  Natural Selection
Which one do we study?
• No ET – don’t have tools to investigate
• No Supernatural/Divine – can’t study in
science
• Yes Evolution! We, as scientists, attempt
to understand and explain these forces!
Origin of Organic Molecules
• Primitive Atmosphere
– Reducing atmosphere:
H2S, NH3, CH4, CO2, H2O  Lots of H+!
– Energy Sources:
UV & Solar radiation, lightning, and
radioactive decay
– Oxidizing atmospheres:
Cannot form complex organic molecules
spontaneously
Formation of Carbon-Based
Molecules
• Miller & Urey – 1953
– Demonstrated complex organic molecules can
form under hypothesized primitive Earth
conditions
Miller & Urey’s
Set-up
• Atmosphere:
• Ocean:
CH4, CO2,
H2O, NH3, H2
Pool of H2O
• Energy:
Electrical sparks
Ran Overnight…
“Primordial Soup!”
• Yellow “soup” with >30 complex organic
molecules
– a.a. and purines (Adenine & Guanine)
(>50% of a cell’s dry weight comes from a.a.)
Major theories:
• Hydrothermal vents (in ocean floor)
– Archaebacteria like hot environments; protected
from UV under H2O
• Pyrite or Clay Creation
– Crystalline solid replication mimics cellular
replication. Problem…
• Space invaders brought a.a.
Chapter 4:
Cells
What the cell are we talking
about?
• Cell = membrane-bound unit containing
hereditary machinery and other
components which allow cells to
metabolize, grow, and reproduce
2 Basic Cell Types
• Prokaryotes - bacteria
• Eukaryotes
Common Characteristics of
Pro- and Eukaryotes
• Plasma membrane - lipid bilayer
• Nuclear region
– prokaryotes - not membrane-bound;
circular DNA
– eukaryotes - double membrane =
nuclear envelope
• Cytoplasm = semi-fluid matrix
– contains a.a. and proteins, sugars, etc.
• Ribosomes - manufacture proteins
Cell Theory
• All organisms are composed of one or more
cells.
• Cells are the smallest living things; the
basic unit of life.
• All cells arise from previously existing
cells.
Scientists to Know
(and love)
• Robert Hooke - 1665 - cork under
microscope; first to describe cells
• Antonie von Leeuwenhoek - 1670-1690 –
improved lenses; “animalcules”
• Mathias Schleiden - 1838 - 1st cell theory:
plants are aggregates of cells
• Theodor Schwann - 1839 - added to
theory: animals are aggregates of cells
Size means EVERYTHING!
• Small cell sizes have advantages
– such as… more efficiency
– Diffusion is s-l-o-w
• Surface area:Volume
– surface area increases as the d2
– volume increases as the d3
– i.e. volume increases MUCH faster
1
3
1
3
Total volume
Total surface
area
Surface-tovolume ratio
27 units3
27 units3
54 units2
162 units2
2
6
SA and Volume v. Cell Diameter
SA/Volume
250
200
150
Volume
Surface Area
100
50
0
1
2
3
4
Cell Diameter
5
6
Characteristics of Prokaryotic
Cells
• small
• strong cell wall
• no internal membrane-bound organelles
– Cyanobacteria – have chlorophyll and extensions of the
plasma membrane = thylakoids
• DNA forms single, circular molecule
• have ribosomes
• nucleoid region
• The surface of prokaryotic cells may
– Always are surrounded by a chemically complex
cell wall,
– have a capsule surrounding the cell wall,
– have short projections that help attach to other cells
or the substrate, or
– have longer projections called flagella that may
propel the cell through its liquid environment.
Fimbriae
Ribosomes
Nucleoid
Plasma membrane
Cell wall
Bacterial
chromosome
A typical rod-shaped
bacterium
Capsule
Flagella
A TEM of the bacterium
Bacillus coagulans
Origin of Eukaryotic Cells
Endosymbiotic Theory Eukaryotic cells arose from symbiotic
associations between prokaryotic and
ancestral eukaryotic cells
Lynn Margulis
new organelles = endosymbionts
ex. mitochondria, chloroplasts, & centrioles
E=mc2
Comparison of Pro- and
Eukaryotes
• Differ in #, shape, and composition of
chromosomes
• Eu’s have membranes dividing cell into
compartments
• cell wall - no cell wall?
• Most plant cells have large dynamic central
vacuole filled with fluid
Comparison - cont.
• Plasma membranes composed of
phospholipids but have different proteins
embedded.
– Proteins = receptors, channels, markers
– FLUID MOSAIC MODEL - based on location
and dynamism of these proteins in the lipid
bilayer
FLUID MOSAIC MODEL
• First proposed by Singer and Nicholson
• Proteins change tertiary structure
– Channel proteins = admit specific molecules
• ex. Na+
– Receptor proteins = transmit info; induce
changes w/in cell when they come in contact w/
particular molecules
• ex. hormones
– Marker proteins = identify cell as being a
particular type; belong to particular individual
Putting it all together
The main component of the biological membranes is phospholipids. It consists of
1. The polar head (hydrophilic) made from glycerol and phosphate and
2. The non-polar part which has two fatty acid tails (hydrophobic).
Phospholipids spontaneously arrange in a bilayer.
• Hydrophobic tail regions face inwards and are shielded from the surrounding polar fluid
while the two hydrophilic head regions associate with the cytoplasmic and extracellular
environments, respectively.
• Phospholipids are held together in a bilayer by hydrophobic interactions (weak
associations).
• Hydrophilic/hydrophobic layers restrict entry and exit of substances.
• Phospholipids allow for membrane fluidity/flexibility (important for functionality).
• Phospholipids with short or unsaturated fatty acids are more fluid.
• Phospholipids can move horizontally or occasionally laterally to increase fluidity.
• Fluidity allows for the breaking/remaking of membranes (exocytosis/endocytosis).
Typical Eukaryotic Cell
Eukaryotic cells are partitioned into functional
compartments
The structures and organelles of eukaryotic cells
perform four basic functions.
1. The nucleus and ribosomes are involved in the genetic
control of the cell.
2. The endoplasmic reticulum, Golgi apparatus, lysosomes,
vacuoles, and peroxisomes are involved in the
manufacture, distribution, and breakdown of molecules.
3. Mitochondria in all cells and chloroplasts in plant cells are
involved in energy processing.
4. Structural support, movement, and communication
between cells are functions of the cytoskeleton, plasma
membrane, and cell wall.
Typical
Animal Cell
Rough
Smooth
endoplasmic endoplasmic
reticulum
reticulum
NUCLEUS:
Nuclear
envelope
Chromatin
Nucleolus
NOT IN MOST
PLANT CELLS:
Centriole
Lysosome
Peroxisome
Ribosomes
Golgi
apparatus
CYTOSKELETON:
Microtubule
Intermediate
filament
Microfilament
Mitochondrion
Plasma membrane
NUCLEUS:
Nuclear envelope
Chromatin
Nucleolus
Golgi
apparatus
NOT IN ANIMAL
CELLS:
Central vacuole
Chloroplast
Cell wall
Plasmodesma
Mitochondrion
Peroxisome
Plasma membrane
Cell wall of
adjacent cell
Rough
endoplasmic
reticulum
Ribosomes
Typical
Plant Cell
Smooth
endoplasmic
reticulum
CYTOSKELETON:
Microtubule
Intermediate
filament
Microfilament
Nucleus –
Described in 1831 by
Robert Brown
“Repository of genetic
information”  directs
all activities of the cell
Contains chromosomes
Bounded by 2 membranes
= nuclear envelope
Nuclear pores =
embedded proteins that
act as channels
Nucleolus –
Manufactures
ribosomes
Ribosomal subunits are
passed out of the
nucleus through the
nuclear envelope
Nucleus
Two membranes
of nuclear envelope
Chromatin
Nucleolus
Pore
Endoplasmic
reticulum
Ribosomes
Nucleus
Endoplasmic Reticulum
(ER)
Extensive system of
channels and
compartments
Rough ER - ribosomes
are attached
Smooth ER - few ribosomes; contain enzymes
that function in synthesis of lipids & carbs and
in detoxification of drugs
Ribosomes
ER
Ribosomes
Cytoplasm
Endoplasmic
reticulum (ER)
Free ribosomes
Bound
ribosomes
Colorized TEM showing
ER and ribosomes
mRNA
Protein
Diagram of
a ribosome
Nucleus,
Smooth, and
Rough ERs
Nuclear
envelope
Smooth ER
Ribosomes
Rough ER
Golgi Bodies
Collect, modify,
package, and
distribute molecules
synthesized in smooth
and rough ER
- molecules are
packaged in vesicles
for transport
Golgi at work
“Receiving” side
of Golgi
apparatus
Golgi
apparatus
1
Transport
vesicle
from ER
2
Transport
vesicle from
the Golgi
3
4
4
“Shipping”
side of Golgi
apparatus
Golgi apparatus
Lysosomes
Contain digestive enzymes
Derived from Golgi
Digests & recycles worn
out cellular components
Enzymes optimal at acidic
pH
Primary & Secondary
lysosomes
Animation
Lysosome Activity
Digestive
enzymes
Lysosome
Digestion
Food vacuole
Plasma membrane
Peroxisomes
Contain oxidative
enzymes
Derived from smooth
ER
Enzymes convert fats
to carbs and detoxify
harmful molecules
Many cell organelles are connected through the
endomembrane system
• Some of these membranes are physically
connected and some are related by the transfer of
membrane segments by tiny vesicles (sacs made
of membrane).
• Many of these organelles work together in the
– synthesis,
– storage, and
– export of molecules.
© 2012 Pearson Education, Inc.
• The endomembrane system includes
–
–
–
–
–
–
the nuclear envelope,
endoplasmic reticulum (ER),
Golgi apparatus,
lysosomes,
vacuoles, and
the plasma membrane.
© 2012 Pearson Education, Inc.
Putting some
pieces together…
Transport vesicle
buds off
4
Secretory
protein
inside transport vesicle
mRNA
Ribosome
3
Sugar
chain
1
2
Polypeptide
Glycoprotein
Rough ER
• Vacuoles are large vesicles that have a variety of
functions.
– Some protists have contractile vacuoles that help to
eliminate water from the protist.
– In plants, vacuoles may
• have digestive functions,
• contain pigments, or
• contain poisons that protect the plant.
© 2012 Pearson Education, Inc.
All together now!
Nucleus
Nuclear
membrane
Rough ER
Transport
vesicle from
Golgi to
plasma
membrane
Smooth
ER
Transport
vesicle from ER
to Golgi
Golgi
apparatus
Lysosome
Vacuole
Plasma
membrane
DNA-containing Organelles
• All are endosymbionts.
– Why does that make sense…?
• Remind me:
– Who were the endosymbionts?
– What was that theory?
Mitochondrion
Nucleus
Endoplasmic
reticulum
Some
cells
Engulfing
of oxygenusing
prokaryote
Engulfing of
photosynthetic
prokaryote
Chloroplast
Host cell
Mitochondrion
Host cell
Mitochondria
Bounded by 2
membranes
Matrix - folding of inner
membrane - contains
DNA and ribosomes
Proteins involved in oxidative metabolism are
located in inner mitochondrial membrane =
Power House of Cell
Mitochondrion
Outer
membrane
Intermembrane
space
Inner
membrane
Cristae
Matrix
Chloroplasts -
(Not in diagram because not in animal
cells!)
Bounded by 2 membranes
Inner membrane defines stroma which
contains DNA and ribosomes
Light rxns of photosynthesis occurs in
thylakoids - stacks of folded membranes in stroma
Inner and
outer
membranes
Granum
Chloroplast
Stroma
Thylakoid
Centrioles (aka
centrosomes)
Associated with
assembly and
organization of
microtubules
(composed of tubulin;
influence cell shape,
move chromosomes in
cell division, provide
internal structure of
cilia and flagella)
Centrioles are only found in
ANIMAL cells!
Cytoskeleton - network of
protein fibers that support and
anchor organelles in the
cytoplasm
Characteristics of Cytoskeleton
• Made of 3 types of fibers:
– Actin filaments = long protein fibers; provide
mechanical support, shape
– Microtubules = hollow tubes; cell movement
– Intermediate fibers = protein ropes; intracellular
tendons
• Responsible for shape and organizing
enzymes and macromolecular complexes
w/in cytoplasm
Cilia & Flagella
• Used in locomotion and feeding
• Bacterial & Eukaryotic flagella differ in
internal organization and type of
movement
– Eu. flagella & cilia
• 9 pairs of microtubules surrounding 2 central
ones = “9 + 2” arrangement
• arise from basal bodies
• flagella - sometimes called undulopodia
• Cilia and Flagella increase SA!
Cross-Section of Eukaryotic
Flagella
Plasma
membrane
= microtubules
Electron Micrograph of Cross
Section of a Single Cilium
(courtesy of
Peter Satir)
Cilia and flagella move when microtubules bend
• While some protists have flagella and cilia that
are important in locomotion, some cells of
multicellular organisms have them for different
reasons.
– Cells that sweep mucus out of our lungs have cilia.
– Animal sperm are flagellated.
© 2012 Pearson Education, Inc.
Outer microtubule doublet
Central
microtubules
Radial spoke
Dynein proteins
Plasma membrane
Problems with sperm motility may be
environmental or genetic
• In developed countries over the last 50 years,
there has been a decline in sperm quality.
• The causes of this decline may be
– environmental chemicals or
– genetic disorders that interfere with the movement
of sperm and cilia. Primary ciliary dyskinesia (PCD)
is a rare disease characterized by recurrent infections
of the respiratory tract and immotile sperm.
© 2012 Pearson Education, Inc.
The extracellular matrix of animal cells functions in
support and regulation
• Animal cells synthesize and secrete an elaborate
extracellular matrix (ECM) that
– helps hold cells together in tissues and
– protects and supports the plasma membrane.
© 2012 Pearson Education, Inc.
The extracellular matrix of animal cells functions in
support and regulation
• The ECM may attach to a cell through
glycoproteins that then bind to membrane
proteins called integrins. Integrins span the
plasma membrane and connect to microfilaments
of the cytoskeleton.
© 2012 Pearson Education, Inc.
Glycoprotein
complex
with long
polysaccharide
EXTRACELLULAR FLUID
Collagen fiber
Connecting
glycoprotein
Integrin
Plasma
membrane
CYTOPLASM
Microfilaments
of cytoskelton
Three types of cell junctions are found in animal
tissues
• Adjacent cells communicate, interact, and adhere
through specialized junctions between them.
– Tight junctions prevent leakage of extracellular
fluid across a layer of epithelial cells.
– Anchoring junctions fasten cells together into
sheets.
– Gap junctions are channels that allow molecules to
flow between cells.
© 2012 Pearson Education, Inc.
Tight junctions
prevent fluid from
moving between cells
Tight junction
Anchoring
junction
Gap junction
Plasma membranes
of adjacent cells
Extracellular matrix
Cell walls enclose and support plant cells
• A plant cell, but not an animal cell, has a rigid
cell wall that
– protects and provides skeletal support that helps
keep the plant upright against gravity and
– is primarily composed of cellulose.
• Plant cells have cell junctions called
plasmodesmata that serve in communication
between cells.
© 2012 Pearson Education, Inc.
Plant cell
walls
Vacuole
Plasmodesmata
Primary cell wall
Secondary cell wall
Plasma membrane
Cytoplasm
Review: Eukaryotic cell structures can be grouped
on the basis of four basic functions
• Eukaryotic cell structures can be grouped on the
basis of four functions:
1.
2.
3.
4.
genetic control,
manufacturing, distribution, and breakdown,
energy processing, and
structural support, movement, and communication
between cells.
© 2012 Pearson Education, Inc.
You should now be able to:
1. Describe the importance of microscopes in
understanding cell structure and function.
2. Describe the three parts of cell theory.
3. Distinguish between the structures of
prokaryotic and eukaryotic cells.
4. Explain how cell size is limited.
5. Describe the structure and functions of cell
membranes.
© 2012 Pearson Education, Inc.
You should now be able to:
6. Explain why compartmentalization is important
in eukaryotic cells.
7. Compare the structures of plant and animal
cells. Note the function of each cell part.
8. Compare the structures and functions of
chloroplasts and mitochondria.
9. Describe the evidence that suggests that
mitochondria and chloroplasts evolved by
endosymbiosis.
© 2012 Pearson Education, Inc.
You should now be able to:
10. Compare the structures and functions of
microfilaments, intermediate filaments, and
microtubules.
11. Relate the structure of cilia and flagella to their
functions.
12. Relate the structure of the extracellular matrix
to its functions.
13. Compare the structures and functions of tight
junctions, anchoring junctions, and gap
junctions.
© 2012 Pearson Education, Inc.
You should now be able to:
14. Relate the structures of plant cell walls and
plasmodesmata to their functions.
15. Describe the four functional categories of
organelles in eukaryotic cells.
© 2012 Pearson Education, Inc.
Structural Differences between
Plant
and Animal Cells
•
•
•
•
Cell wall
MTOC?
Chloroplasts
Central vacuole
•
•
•
•
No cell wall - no need!
Centrioles
No chloroplasts
No central vacuole
End of Cells!
Download
Related flashcards
Create Flashcards