Download Topic 1: Cell Biology

Topic 1: Cell Biology
1.1-1.2
IB Biology Junior Year
Cell Theory
• 1. All organisms are
composed of one or
more cells.
• 2. Cells are the smallest
units of life
• 3. All cells come from
pre-existing cells
Functions of Life
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Metabolism
Growth
Reproduction
Response
Homeostasis
Nutrition
Excretion
Cells and Sizes
• Light Microscope
– Inexpensive and easy to
operate
– Simple specimen
preparation
– Magnifies up to 2000x
– Specimens may be living
or dead
• Electron microscope
– Expensive to purchase
and operate
– Complex specimen
preparation
– Magnifies over 50,000x
– Specimens are dead and
fixed in a plastic material
Microscopes
Limiting Cell Size
• Surface to volume ratio
– Limits cell size
– Processes dependent on
volume:
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Heat production
Waste production
Resource consumption
Rate of chemical
reactions
• More surface
area/volume, moves
more materials in and
out
• Large cell: less SA than
smaller one
• Large animals do not
have large cells, just
more cells.
Cell Reproduction and Differentiation
• Facilitates growth of
organism
• Replaces dead or
damaged cells
– Nerve cells and muscle
cells do not reproduce
• Multicellular organisms
begin from one cell as a
result of sexual
reproduction
• Unicellular- binary fission
• Cell Differentiation
– Result of gene expression
regulated by DNA
– Specificity of cell depends
on area of DNA that is
activated
Cell Reproduction
Emergent Concept
• Multicellular organisms
can carry out more
functions collectively
than the sum of each
cell’s specialty
• Non-living
moleculesfunction
together living
organism
Stem Cells
• 1. Pluripotentembryonic
• 2. Tissue specific
• Stem cells can divide
and differentiate into
any kind of cell
• Plants: meristematic
tissue
– Root and stem tips
• Stem cells divide
produce other stem
cells, as well.
– Continual production of
specialized cells and
stem cells
Germ Layer Derivatives
Stem Cell Research
• Embryonic stem cells
– Grown in culture
– Can replace cells that are
injured or diseased
– Therapeutic cloning
• Parkinson’s
• Alzheimer's
• Diabetes
• Tissue specific:
– Blood cells- replace
damaged bone marrow
– Stargardt’s disease• Inherited
• Defective vitamin A
processing
– Retinal function
– 20 years: loss of vision
– March 2010: use of
embryonic stem cells
designed to protect and
regenerate retinal cells
Ethics of Stem Cell Research
• Pluripotent:
controversial
– From embryos in IVF
clinics
– Harvesting requires
death of embryo
• Cultural and religious
traditions:
– Many nations ban
practice
What are the opposing
views?
Stem Cell Videos
• http://www.nyscf.org/about-us/watch-nyscfvideos/item/16-video-stem-cells-developingnew-cures
• https://www.youtube.com/watch?v=EWUqCl
H8oos
1.2 Ultrastructure of Cells
• Prokaryotes:
– Much smaller than
eukaryotic cells- less
than 1um in diameter
– “First” cells
– Features:
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Cell wall
Plasma membrane
Flagella
Pili
Ribosomes
Nucleoid
Features of Prokaryotic Cells
• Cell wall and cell
membrane:
– Cell wall- protects and
maintains shape of cell
• Made of peptidoglycan; a
carb-protein complex
• Some also have extra
layer- LPS (lipo-poly
saccharide) Induces
strong immune response
– Fever
– Shock
• Plasma membrane:
– Similar composition to
eukaryotes
– Controls what enters and
leaves
– Role in binary fission
– Contains cyctoplasm
– Role in cell metabolism
Gram + and Gram –
Bacterial Cells
Pili and Flagella
• Pili-
• Flagella-
– Hair-like growths used
for attachment
– Role in joining bacterial
cells in preparation for
sexual reproduction
• DNA transfer from one to
another through
conjugation tube
– Flagellum (singular)
– Role in movement
Ribosomes & Nucleoid
• Ribosomes– Size: 70s
– Protein synthesis
• Nucleoid– Non compartmentalized
– Long circular strand of
DNA
– Plasmids
• Not connected to
chromosome
• Confer virulence, antibiotic resistance
• Increase survival
advantage of cell
Reproduction: Binary Fission
• DNA copied
– Daughter chromosomes
attach to opposite ends
of plasma membrane
– Result is 2 identical
daughter cells
– Process includes
partitioning of new DNA
by microtubule fibers
called FtsZ
Harvard’s “Inner Life of the Cell”
• Non-narrated version:
• https://www.youtube.com/watch?v=wJyUtbn
0O5Y
• Narrated version:
• https://www.youtube.com/watch?v=FzcTgrxM
zZk
Eukaryotic Cells
• Protozoans, algae,
fungi, plant and animal
• 5-100um in size
• Organelles:
– Non-cellular membrane
bound structures that
carry out specific
functions to allow the
cell to function as a
whole
• Compartmentalization:
– Allows for:
• Incompatible chemical
reactions to occur
• Isolation of certain
chemical reactions
• Result: increased
efficiency
Animal and Plant
Eukaryotic Organelles
• Endoplasmic reticulum– Most cells have both rough
and smooth
– Transport throughout cell
– Smooth: no ribosomes
• Production of membrane
phospholipids, cellular
lipids
• Detoxification in liver
• Stores Ca2= in muscle cells
• Transports lipid based
compounds
• Helps liver release glucose
• Rough E.R.
– Ribosomes (80s) on
exterior channels
• Protein synthesis
• Protein transport
• Proteins synthesized here
are transported out of the
cell
Ribosomes
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80s
No exterior membrane
On surface of rough E.R.
Free in cytoplasm
– Proteins synthesized
here are used inside the
cell
Composed of 2 sub-units
Sub-units not assembled
until there is a protein to
be translated
Lysosomes
• Intracellular digestive
centers
• Arise from Golgi
• No internal structures
• Single membrane sacs
with as many as 40
different hydrolytic
enzymes
• Break down carbs,
lipids, proteins, nucleic
acids
• Fuse with old and
damaged organelles
from within cell to
break them down
Golgi Apparatus
• Made of flattened sacs
called cisternae
• Collects, packages,
modifies and distributes
materials made in the cell
– Cis side- near the rough
E.R., receives products
from the E.R.
• Trans side- side opposite
cis where materials are
discharged
– Vesicles filled with
products exit to where
they are needed
• Golgi prevalent in
glandular cells (pancreas)
that manufacture and
secrete substances
Mitochondria
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Mitochondria- plural
Mitochondrian- singular
Rod shaped
Close in size to bacterial
cell
Have own DNA
Has own ribosomes (70s)
Circular chromosome
Double membrane
– Outer- smooth
– Inner- folded into cristae
• High surface area
• Filled with semi-fluid
matrix
• Has inner membrane
space
• Most reactions ATP
• Cells with high energy
requirements have more
mitochondria
• Mitochondria are
inherited from your
mother only
Mitochondrion
Nucleus
• Isolated region where
DNA resides
• Double membranenuclear envelope
– Has pores that allow
communication from the
cell
• DNA functions are
isolated from the rest of
the cell
• DNA in form of
chromosomes
– Vary in number
• Not dividing? –DNA in
form of chromatin
– Chromatin wound around
histone proteins
– Nucleosome=strand of
DNA + 9 histone proteins
– Chromosomes are highly
coiled structure of
nucleosomes
Nucleus, cont.
• Usually centrally located • Contains nucleolus
except in plant cells
– Ribosome manufacture
– Large central vacuole
• Can have single nucleus,
multiple nuclei, or no
nucleus at all
– RBC- anucleate, don’t
need to reproduce,
generated in bone
marrow
Chloroplasts
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Plant cells and algae only
Double membrane
Same size as bacterial cell
Has own DNA, circular
Can reproduce
independently
• Has 70s ribosomes
• Interior:
– Grana, thylakoids, stroma
• Grana:
– Thylakoids stacked like pile
of coins
• Thylakoids:
– Flattened membrane sacs
containing chlorophyll
• Stroma:
– Fluid filled area full of
enzymes and chemicals for
photosynthesis
Chloroplast
Centrosome
• Pair of centrioles
• Assembly of
microtubules
– Structure and movement
of cell
– Plants do have
microtubules but no
centrioles
• Located close to the
nucleus
Vacuoles
• Storage organelles that
arise from Golgi
• Membrane bound
• Can store:
– Food and water
– Metabolic waste
– Toxins
• Enable cells to increase
SA:V ratio
• Plants:
– Store water
– Provide structure to
plant
Cell Walls
• Plants:
– Cell wall of cellulose
(fiber)
– Humans cannot digest
cellulose because we
lack cellulase
• Fungi:
– Cell wall of chitin
– Water uptake and
structure
Cell Membrane
• Phospholipid bilayer
• Hydrophobic and
hydrophyllic
components
• ECM (extra cellular
matrix) of collagen and
glycoproteins
– Strengthens cell
membrane and anchors
it to adjacent cells
• ECM:
– Allows cell-cell
interactions
– Could alter gene
expression
– Enable coordination of
cell actions within tissue
– Directs stem cells to
differentiate
– Directs cell migration
and movement
Cell Membrane