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Ch. 3 Cells
Cell Theory
1. Cells are the basic units of life
2. All organisms are made of one or more
cells
3. Cells arise from other cells
Figure 6.8a
ENDOPLASMIC RETICULUM (ER)
Flagellum
Nuclear
envelope
Nucleolus
Rough Smooth
ER
ER
NUCLEUS
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate filaments
Microtubules
Ribosomes
Microvilli
Golgi apparatus
Peroxisome
Mitochondrion
Lysosome
Cell Membrane
Cell membrane – gate, controlling what
comes in and out of the cells
• Phospholipid bilayer – phosphate head
and two fatty acid tails
• Phosphate head – hydrophilic (water
loving)
• Fatty tails – hydrophobic (water hating)
• Selectively permeable
• Cholesterol – stability at high
temperatures, flexibility at low temps.
Proteins
1.
2.
3.
4.
5.
6.
7.
Recognition proteins – identify the cell - glycoproteins
Channel proteins – passage of small, hydrophilic
substances in and out of the cell
Adhesion proteins – form junctions with other cells
Transport pumps – sodium/potassium pump
Receptor proteins – G-protein linked
Ion channels – Na/K channels
Carrier proteins – move specific substances through
membrane
Prokaryote Cell – Bacterial Cells
Prokaryote vs. Eukaryote
 Prokaryotes – bacterial cells
•
•
•
•
Do not have a nucleus
Have fewer parts, smaller ribosomes
Have DNA and reproduce
No membrane around organelles
 Eukaryotes – plants, animals
• Have a nucleus
• Have more parts
• Membrane bound organelles
Cytoplasm
 Cytosol and organelles
 Cytosol is mostly water
 Organelles – nucleus and other parts
floating in cytosol
Organelles
 Ribosomes – On the
rough endoplasmic
reticulum and free in
the cytoplasm
 make proteins
(manufacturer)
 Smooth endoplasmic
reticulum
 detoxification and
making lipids and
carbohydrates
Nucleus
 The control center –
“brain”
 Nuclear envelope –
covered in pores – send
proteins out
 Contains DNA coiled
around histone proteins
(nucleosome)
 DNA coils into chromatin
and chromatin condenses
into chromosomes
(blueprint)
Nucleolus
 Dark structure inside the nucleus
 Make ribosomes
 Disappears during mitosis (cell division)
Golgi and Lysosomes
 Golgi apparatus
 stack of pancakes
 Packages things and
sends them out of the
cell
 Lysosome
 digestion of food
particles
 contain enzymes
 Low pH
Mitochondria
 Powerhouse of the cell
 ATP – energy is
created
Cell Shape
 Cytoskeleton – internal
framework in an animal
cell that helps maintain cell
shape.
 Microtubules – hollow
tubes made of protein help maintain cell shape
and serve as tracks for
transport throughout the
cell.
 Cillia and Flagella are
made of microtubules.
 Microfilaments – smaller
proteins that help maintain
cell shape.
Euglena
Paramecium
Vacuoles and vesicles
 Transport vesicles – move materials within
the cells and through the endomembrane
system
 Food vacuoles – temp. food storage, merge
with lysosomes for digestive purposes
 Contractile vacuole – in some organisms for
pumping water
 Central vacuole – in plants, fills with water
creating turgor pressure
Figure 6.32
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
TEM
0.5 m
Tight junction
Intermediate
filaments
Desmosome
TEM
1 m
Gap
junction
Space
between cells
Plasma membranes
of adjacent cells
Extracellular
matrix
TEM
Ions or small
molecules
0.1 m
Plant Cells
 Plant cells have a cell wall – made of
cellulose
 They also have chloroplasts – where
photosynthesis occurs
 Chlorophyll – pigment that absorbs sunlight
energy
 Other functions of central vacuole – pg. 35
Plant Cells
Cell Transport



Semipermeable membrane – small,
lipid-soluble particles can pass, but
large, charged particles cannot
Diffusion – net movement of
particles from high to low
concentration
Concentration gradient – the
difference in concentration between
one area and another
Cell Membrane
Diffusion
Osmosis





Diffusion of water through
aquaporins
Moves from high water potential to
low water potential.
Hypertonic solution – higher solute
concentration
Hypotonic solution – lower solute
conc.
Isotonic soln. – solute conc. Equal
on both sides and equilibrium.
Osmosis
Figure 36.9
Initial flaccid cell:
0.4 M sucrose solution:
Plasmolyzed
cell at osmotic
equilibrium with
its surroundings
P  0
S  0.9
  0.9 MPa
P  0
S  0.9
  0.9 MPa
(a) Initial conditions: cellular   environmental 
P  0
S  0.7
  0.7 MPa
Pure water:
P  0
S  0
  0 MPa
Turgid cell
at osmotic
equilibrium with
its surroundings
P  0.7
S  0.7
  0 MPa
(b) Initial conditions: cellular   environmental 
Facilitated Diffusion





Passive transport – no Energy
required
Moves down concentration gradient
Moves through a carrier or channel
protein
Ex. Glucose
Lipid-insoluble substances
Facilitated Diffusion
Active Transport






Not passive
Goes up or against the concentration
gradient (needs energy)
Na+ out/K+ in
Involves specific carrier proteins
Important in muscle contractions, nerve
impulses – maintains resting potential
Ex. Plant roots, ion pumps
Active Transport – Sodium/Potassium
Pump
Endocytosis



Enodcytosis – cell taking materials
in
Pinocytosis – cell drinking
Phagocytosis – cell eating
Endocytosis
Receptor-mediated endocytosis
Exocytosis


Releasing molecules into the
extracellular matrix
Bulk flow – passage of substances
through vessels or xylem/phloem
Exocytosis
Countercurrent exchange




Movement of materials in bulk flow
in opposite direction
Ex. Fish gills and capillaries
Water(with fresh dissolved oxygen)
entering gills encounter capillaries
deficient in oxygen
Diffusion of oxygen is enhanced
Cell Junctions


Plasmodesmata –
tunnels between
plant cells
Junctions in
animal cells –
tight, anchoring,
communicating