Saturday, October 10, 2015 1 The Cell Packet #11

Friday, April 21, 2023 1

The CellThe CellPacket #11Packet #11


CytologyCytology

The study of cells.There are two basic types

– Prokaryotic cells– Eukaryotic cells


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


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



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


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



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


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



Eukaryotic CellsEukaryotic Cells

Most organisms are composed of eukaryotic cells.

There are two basic types– Plant cells– Animal cells


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


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


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.




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


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




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




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



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



For Biology 1 Honors OnlyFor Biology 1 Honors Only

Cells are composed of filaments– Microtubules– Microfilaments– Intermediate filaments

Details to come in AP Biology


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



Cell to Cell ConnectionsCell to Cell Connections

Tight JunctionsGap JunctionsDesomeres

– Details to come in AP Biology




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



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.



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


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


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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Saturday, October 10, 2015 1 The Cell Packet #11