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Friday, April 21, 2023 1
The CellThe CellPacket #11Packet #11
Friday, April 21, 2023 2
CytologyCytology
The study of cells.There are two basic types
– Prokaryotic cells– Eukaryotic cells
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The DiscoveryThe Discovery
Cells discovered by Robert Hooke in 1665– However the subcellular structures could not be
seen--the organelles
It wasn’t until the 1950’s, with the invention of the electron microscope that cell biology really took off
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Organelles IsolationOrganelles Isolation
Can be isolated by a process called cell fractionation– Taking cells apart and separating the major organelles
so that their individual function can be isolated– Centrifuge
Is the instrument that is used to fractionize cells Spins fast as much as 80,000 revolutions per minute and apply
forces on particles up to 500,000 times the force of gravity
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Organelle Isolation IIOrganelle Isolation II
Micromanipulation– Another technique for the removal of parts of the cell– Can also insert material into a living cell– Done while looking through a microscope
In-Vitro Fertilization In-Vivo Fertilization
Cell Cultures**– Isolate one type of cell and you grow it in large
numbers--bacteria for example
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Cell TheoryCell Theory
Observations and conclusions from various scientists– All living things are composed of cells– Cells are the basic units of structure and
function in living things– All cells come from preexisting cells
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Prokaryotic versus EukaryoticProkaryotic versus Eukaryotic
Prokaryotic– No nuclear membrane
No nucleus Lack membrane bound organelles
– No chromosomes--circular strands of DNA– May contain chlorophyll but not chloroplasts– Small Ribosomes– Cell wall is present**– No mitosis or meiosis occurs
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Prokaryotic versus Eukaryotic Prokaryotic versus Eukaryotic IIII
Eukaryotic Cells– Nuclear membrane is present
Nucleus is present Membrane bound organelles
– Chlorophyll when present, contained in chloroplasts
– Ribosomes are larger– Cell wall is present in some– Mitosis and meiosis occurs
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Friday, April 21, 2023 12
Eukaryotic CellsEukaryotic Cells
Most organisms are composed of eukaryotic cells.
There are two basic types– Plant cells– Animal cells
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Plant CellsPlant Cells
Cell wall that contains cellulose Large vacuole filled with cell sap Larger than animal cells Shape** Cilia and flagella absent in higher plants
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Animal CellsAnimal Cells
No cellulose cell wall-only membrane Some vacuoles but usually small and numerous Cytoplasm throughout the cell Nucleus anywhere in cytoplasm by often central Cilia common in higher animals
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Cell SpecializationCell Specialization{Animal Cell}{Animal Cell}
Cells are often uniquely suited to perform a particular function within the organism– Nerve Cells– Muscle Cells– Rods and Cones in the eye– Sex cells– Determined by complex processes of turning on
and off genes.
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Plant Cell vs. Animal CellPlant Cell vs. Animal Cell Similarities
– Both Eukaryotic Cells– Have membrane bound organelles
Differences– Plant cells are “generally” larger than animal cells– Plant cells have a cell wall of cellulose
Adds stability and protection to the plant cell
– Plant cells have vacuoles That are used as space fillers Fulfils digestive functions in plants--similar to lysosomes that
are also found in plant cells.
– Animal cells have centrioles
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Cell Structure and Function ICell Structure and Function IChromatin
– The complex of DNA and histome proteins which make up chromosomes in eukaryotic cells
Chromosomes– Long threadlike association of genes composed
of chromatin and found inside the nucleus of the cell
Nucleolus– The region of the eukaryotic nucleus that
engaged in ribosome synthesis
Cell Structure and Function IICell Structure and Function II Nucleus Structure
– Contains a eukaryotic cell’s genetic library
Nucleus Function– In eukaryotic cells, this is a membrane bound organelle that contains the
cell’s genetic material– Acts as the control center for the cell– Produce ribosomes and RNA*– Play an essential role in cell division
Nuclear Envelope– Surrounds the nucleus– Contains nuclear pores
Allow things in and out of the nucleus
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Cell Structure and Function IICell Structure and Function II Rough or Smooth? Rough or Smooth?
Rough Endoplasmic Reticulum– Functions in the synthesis and transport of proteins– This is where we find ribosomes
Smooth Endoplasmic Reticulum– Functions in the synthesis and transport of lipids– There are no bound organelles—that is why they look so
smooth Ribosomes
– Cytoplasmic organelle that is the site for protein synthesis– Small complex particles consisting of proteins and RNA
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Cell Structure and Function IIICell Structure and Function III Golgi Apparatus
– Stack of membranous sacs– Packages and distributes lipids and proteins that form
in the ER– If we have time we will have a closer look at this
process– Something inportant—know the ends and structure
Cis—entry; Trans—exit—People always forget this
– Vesicles enter and leave here Lysosome
– Contains digestive enzymes that degrades the cell and other malfunctioning organelles
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Friday, April 21, 2023 27
Cell Structure and Function IVCell Structure and Function IV
Peroxisome– Contains enzymes that carry out redox
reactions and is key in detoxification of drunks
Mitochondria– This is where we produce our energy—AKA
ATP– We’ll get all up in the Kreb’s cycle soon
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For Biology 1 Honors OnlyFor Biology 1 Honors Only
Cells are composed of filaments– Microtubules– Microfilaments– Intermediate filaments
Details to come in AP Biology
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Other Important Features in Other Important Features in the Cellthe Cell
Chloroplasts– In plants—used in photosynthesis– We’ll get to know this process later as well
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Cell to Cell ConnectionsCell to Cell Connections
Tight JunctionsGap JunctionsDesomeres
– Details to come in AP Biology
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Components of the Cell Components of the Cell MembraneMembrane
Microfilaments, Microtubules and Intermediate filaments—we have already touched—but what else is there?
Glycoproteins Carbohydrates Cholesterol
– Used in rigidity and fluidity of the membrane Peripheral Protein (small) and Integral (big) proteins
—useful in hormonal signals—later IT IS IMPORTANT TO KNOW WHAT
EVERYTIHNG LOOKS LIKE AND WHERE THEY ARE IN THE CELL MEMBRANE
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Friday, April 21, 2023 37
DiffusionDiffusion Ok, now that we know some of the ways proteins enter
organelles (from earlier), let’s have a closer look at some mechanisms in which how molecules and proteins are transported across the membranes of these organelles.
Firstly let’s define the word Diffusion– The three types of diffusion
Regular Diffusion—we travel down the concentration gradient—no energy is required
Facilitated Diffusion—we travel down the concentration gradient using a protein molecule--no energy is required
Active Transport—flow of molecules against the concentration gradient with the use of a protein molecule--ATP (energy) is required.
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Friday, April 21, 2023 39
Diffusion IIDiffusion IIWhich of the two previous are considered
passive transport and why?– Regular and facilitated—reason is because
there is no use of energy
Examples– Active transport—transport of proteins Active transport—transport of proteins
through nuclear poresthrough nuclear pores
Friday, April 21, 2023 40
Diffusion IIIDiffusion III
Migration of substances from regions or high concentration to regions of low concentration.– Occurs in our lungs--CO2 out O2 in
Regular Diffusion
Friday, April 21, 2023 41
Diffusion IVDiffusion IV
Special Diffusion Osmosis
– Notes from Previous Lecture Solution
– Solvent--Major– Solute--minor
– Transfer of a liquid solvent through a semi permeable membrane that does not allow dissolved solids (solutes) to pass.
– Osmosis refers only to the transfer of the solvent.– High Concentration to an area of low concentration.
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Friday, April 21, 2023 43
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