Download 6.1 A Tour Of the Cell - Pomp

Chapter 6: A Tour Of the Cell
Hierarchy of Biological organization:
Place in order from smallest to largest:
Tissue
Organisms
Communities
Organelles
Cells
Biosphere
Populations
Organ and Organ systems
Ecosystems
Molecules
Hierarchy of Biological organization:
 1. Molecules
 2. Organelles
 3. Cells
 4. Tissue
 5. Organs and Organ systems
 6. Organisms
 7. Populations
 8. Communities
 9. Ecosystems
 10. Biosphere
The Importance of Cells
The simplest form
Very diverse
Structural order – reinforcing the
themes of emergent properties
Correlation between structure and
function
Interactions with the Environment
How do biologists study cells:
Two methods:
1. Microscopy- investigations employing a
microscope
2. Cell Fractionation- using the tools of
biochemistry
Microscopy: Investigations employing
a microscope
A. Two important parameters:
Magnification- the ratio of an
object’s image size to its real size
Resolution- a measure of the
clarity of the image; the minimum
distance 2 points can be separated
and still be distinguished as 2
points
Resolution is inversely related to
wavelength
Microscopy: Investigations employing
a microscope
B. Two types:
Light microscopes (LMs)
Electron Microscope (EM)
Light Microscopy:
Passing visible light through a lens, then a
specimen, then to the eye.
Lens refracts the light to magnify the image
Limited by the shortest wavelength of
visible light used to illuminate the
specimen.
Electron microscope:
Focuses a beam of electrons either on the
surface or through a specimen
Much shorter wavelengths (remember the
relationship between resolution and
wavelength?)
Resolution of about 2nm- a hundred- fold
improvement over light microscopes
Electron microscope:
Two types:
Scanning Electron Microscope (SEM):
Transmission Electron Microscope(TEM):
Scanning Electron Microscope(SEM)
Useful in detailed study of surface
of specimen
Specimen is covered with a thin layer of gold
Great depth of field
3-D like image
Transmission Electron Microscope
(TEM):
Used to study internal structures of the cell
Uses electromagnets as lenses
Cell Fractionation:
Separating the organelles of a cell
Centrifuge
Separates according to particle size and density
Uses force of gravity
Ultracentrifuge
Enables the study of cell function and structure
Isolating Organelles by Cell Fraction
 Goal of cell fractionation
To take cells apart and separate the major organelles
from one another
 Centrifuge is used
Separates cell by size and density
Ultracentrifuges – the most powerful machines
 Enables the study of cells’ composition and
functions
Ex. Cellular respiration
PCA: State the obvious- 1. distinguish between prokaryotic
and eukaryotic. 2. Give two obvious differences.
Prokaryotic vs. Eukaryotic:
1. What are the basic features of
all cells:
Plasma membrane
Cytosol
Chromosomes
Ribosomes
Prokaryotic vs. Eukaryotic:
2a. The nucleus:
Prokaryote (pro = before, karyon =
kernel(nucleus)
Domains Bacteria and Archaea
Eukaryote (Eu = true, karyon =
kernel)
Domain Eukarya
Prokaryotic vs. Eukaryotic:
2b. DNA:Prokaryotes- DNA is
concentrated in the nucleiod
No membrane separates it from
the rest of the cell
Eukaryotes- DNA is located in a
double membrane
Prokaryotic vs. Eukaryotic:
3. Cytoplasm:
Present in both cells
Eukaryotes contain multiple
organelles and prokaryotes do not
Prokaryotes (as well as eukaryotes)
have ribosomes
Prokaryotic vs. Eukaryotic:
For other features see diagram:
The nucleus:
1. contains genes (most of them)
2. 5 micrometers in diameter
3. Nuclear envelope: double membrane
structure(lipid bilayer)
Nuclear pore complex
Nuclear lamina-array of proteins providing
shape and support for the nucleus
4. Nucleolus- synthesis of ribosomes
5. Chromosomes- chromatin(complex of
DNA and proteins)
The Nucleus:
Function of:
Directs protein synthesis by
transcribing mRNA
Ribosomes:
Protein factories
23nm in diameter
Composed of half RNA and half protein
One large subunit and one small subunit
Synthesized at the nucleolus
Half million ribosomes per cell
Endomembrane System:
Functions of:
Protein synthesis
Transport of proteins
Metabolism of lipids
Movement of lipids
Detoxification of poisons
Endomembrane System:
Includes:
Nuclear envelope
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane (indirectly)
Endoplasmic Reticulum:
Endoplasmic = within the cytoplasm
Reticulum = little net
Continuous maze like sac(cisternae)
surrounded by a SINGLE membrane
Lumen- internal cavity- provides storage
Continuation of nuclear envelope
Lumen of nuclear envelope is continuous with lumen
of ER
Endomembrane System:
Two distinct regions:
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Endomembrane System:
1. rough endoplasmic reticulum
Contains ribosomes
Synthesizes proteins to be secreted
2. smooth endoplasmic reticulum
Synthesis of lipids(for membranes)
Metabolism of carbs
Detoxification
Ships proteins from RER to golgi apparatus
Endomembrane System:
Golgi Apparatus:
A stack of flat, membranous sac
Has a polarity or sideness:
Receives transport vesicles from the endoplasmic
reticulum(Cis face)
Modifies, processes, sorts, packages and ships
proteins(Trans face)
Produces secretory vesicles that pinch off, fuse
with the plasma membrane and secreted by
exocytosis
A stack of flat, membranous, polar sac
Golgi Apparatus cont…
Produces and modifies polysaccharides
that will be secreted
Endomembrane system:
Lysosomes:
Single membrane bound sac containing
hydrolytic digestive enzymes
Used to digest macromolecules
Synthesized in the rough endoplasmic
reticulum, sent to the golgi apparatus and
pinched off as a vesicle with over forty digestive
enzymes
Recycle the cells organic material
Lipid digestion enzyme in this organelle can
lead to Tay- Sachs disease
Endomembrane System:
Peroxisomes:
Single membrane organelles that function in the
synthesis of fatty acids
Produce hydrogen peroxide as a by-product
Function in detoxifying alcohol and other
poisons in the liver
Break down fatty acids into smaller molecules
which can be transferred to the mitochondria for
cellular respiration
Break down molecules through oxidation
Endomembrane System:
Glyoxosomes:
Specialized peroxisomes
Found in fat storing tissues of plant seeds
Convert fatty acids to sugars for the emerging
seedling
Capable of increasing in numbers by splitting in
two when they reach a certain size
Endomembrane System:
Mitochondria:
 Double membrane organelle with a smooth
outer membrane and rough inner membrane
(matrix)which contains inner foldings (cristae)
Only source of DNA that is different and separate
from nuclear DNA
Contains ribosomes in its matrix
Functions in respiration and produces ATP
Metabolism of glucose and fatty acids
Endomembrane System:
Chloroplasts:
Belongs to a group of organelles called plastids
Functions in the photosynthetic production of
glucose(used to make ATP)
Convert light energy to chemical energy
Double membrane structure that contains
thylakoid sacs
Stacks of thylakoid membranes = granum(grana)
Stroma- fluid surrounding thylakoid, contains
DNA, ribosomes and enzymes.
Endomembrane System:
Mitochondria and Chloroplasts:
Contain DNA, ribosomes and enzymes
Can change shape, grow and occasionally split
into two
mobile
Animals vs. Plant Cells
Similarities:
 Nuclear envelope, nucleolus
 Endoplasmic reticulum
 Ribosomes
 Golgi Apparatus
 Mitochondria
 Peroxisome
 Cytoskeleton
 Centrosome
Animals vs. Plant Cells
Differences
Animal cells:
Lysosomes
Centrioles
Flagella
Plant cells:
Chloroplasts
Central vacuole
Cell Wall
Plasmodesmata
Cytoskeleton:
a network of protein fibers that plays a
role in organizing the structure and
activities of the cell:
Cytoskeleton:
Role of:
1. mechanical support for the cell
2. maintains shape of cell
3. architecture
4. anchors many organelles
5. Involved in cell motility
6.manipulates the plasma membrane to form
food vacuoles during phagocytosis
7. regulation of biochemical activities in the cell
Cytoskeleton:
composed of:
1. microtubules
2. microfilaments
3. intermediate filaments
Microtubules:
hollow tubules composed of the protein
tubulin(α- tubulin, and β-tubulin)
25μm in diameter with 15μm lumen
maintains cell shape, cell motility,
chromosome and organelle movement
Types of Microtubules:
Centrosome – produce microtubules
Centrioles: found in animal cells only
 found in centrosome composed of a ring of
nine sets of triplet microtubules
Types of Microtubules:
Cilia- locomotor appendage
25 µm in diameter, 2- 20µm in length
on stationary cells, cilia move objects on the
cell surface
cilia propels cell in direction perpendicular to
cilia’s axis
Types of Microtubules:
Flagella: locomotor appendages much
larger than cilia
same diameter as cilia(.25µm) but much longer
10-200µm
propels cell in same direction as flagellum’s
axis
undulating, snake like motion
Types of Microtubules:
Basal body: anchors flagella or cilia to the
cell
structurally identical to centriole
Types of microfilaments:
Actin
can form 3-D structure to help support cell
shape
make up core of microvilli
found in skeletal muscle cells and used for
muscle contraction
Myosin
motor proteins
Actin/ Myosin Interactions:
slide filament theory- results in muscle
contraction
cytokinesis
amoeboid movement- pseudopodiaconverts cytoplasm from sol(liquid) to gel
cytoplasmic streaming
More on Intermediate Filaments:
 1. specialized for bearing tension
 2.formed from a family of proteins including
keratins
 3. more permanent fixtures
 4. reinforcing shape of cell
 5. fix position of organelles
 6. make up nuclear lamina inside nucleus
 7. axons of nerve cells are strengthened by
intermediate filaments
 8. may serve as a frame work for entire
cytoskeleton
Extracellular components and
connections
The Cell Wall (plants only):
extracellular structure not found in animal cells
also found in prokaryotes, fungi and some
protists
cell wall thickness= 0.1 µm to several
micrometers
Extracellular components and
connections
Role of the Cell Wall:
protects the plant cell
maintains shape
prevents excessive uptake of water
resist force of gravity
Extracellular components and
connections
cell wall design:
 polysaccharide cellulose microfibrils embedded
in a matrix of other polysaccharides and
proteins
primary cell wall- cell wall secreted by the
young plant
middle lamella: thin layer located between two
adjacent plant cells
secondary cell wall: added between the plasma
membrane and the primary cell wall
Extracellular components and
connections
The Extracellular Matrix(ECM) of animal
cells
Glycoproteins
Mainly collagen
Integrin
Fibronectin
functions in regulating passage of
materials
Example: blood platelets
Extracellular components and
connections
Intercellular Junctions: cell to cell
communication through direct physical
contact
plasmodesmata
tight junctions
desmosomes:
gap junctions:
Extracellular components and
connections
plasmodesmata: perforations of the cell
wall
chemical communication between the cytosol of
one cell to the next
unify plants into a living column
continuous from one cell to the next
allows water, solutes, specific proteins and
RNA molecules to move from cell to cell
Extracellular components and
connections
Tight Junctions: series of connections
between two animal cells that form a crisscross pattern
Interacts with proteins between cells
Extracellular components and
connections
. Desmosomes: made from a complex
series of proteins that extends into the
intercellular space
interacting and interlocking network that binds
two cells together
anchors plasma membrane
Extracellular components and
connections
Gap Junctions: channel between two
animal cells, forms a cytoplasmic bridge
activity is regulated by Ca++
high [Ca++]- gap junctions close
http://highered.mcgrawhill.com/sites/9834092339/student_view0/
chapter4/animation_-_endosymbiosis.html
Possible Essay Questions:
1. Discuss the endosymbiotic hypothesis.
2. Discuss the similarities and differences
between animal and plant cells.
3. How does information flow through the
cell for proteins destined to be secreted by
the cell.
4. How would you distinguish a prokaryotic
cell from an animal cell. What are the
similarities and differences?