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The Cell

Basic Unit of Life

Objective:

•  The student will become familiar with the structure and function of the basic cell :)

•  The student will know the differences between and animal cell and a plant cell

Question of the day:

•  Are you an animal or a plant?

The Cell Theory

•  Cytology: the study of cells

The Generalized Cell: Parts and Organelles:

•  Plasma (cell) membrane: outermost boundary of the cell  Communicates with surrounding environment  Communicates with other cells

The Plasma Membrane

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The Plasma Membrane:

•  Semi-permeable: lets certain things in but doesn’t let other things in

•  Made up of a phospholipid bilayer   “Fluid Mosaic Model”

Functions of the Plasma Membrane:

1.  Communication: enter and leave the cell from external environment

2.  Electrochemical Gradient: chemical imbalance •  Build up of electrons •  Charge: when an electrical impulse goes down a

cell there is a chemical change 3.  Shape and protection: allows a soft shape to

the cell •  Protects the cells inner workings

4.  Selective permeability •  Lipid soluble •  Size: large molecules can’t get in •  Charge: impermeable to all ions •  Presence of channels and transporters (proteins)

•  Cytosol/Cytoplasm: all cellular contents •  Organelles/”little organs”: individual parts

within the cytosol Plasma Membrane

Objective:

•  The student will apply their knowledge of the cell and it’s organelles and become familiar with the structure and function of the cell/plasma membrane.

Question of the day:

•  How do much needed nutrients get into each cell?

•  How do the waste products of metabolism get out of the cell?

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Plasma Membrane Structure: •  The plasma membrane is made up of a

phospholipid bilayer •  A phospholipid has two ends, one is the

hydrophilic (or water loving) head the other is the hydrophobic (or water fearing) tail.

Phospholipid bilayer:

http://sleekglobal.com/images/sg0065.jpg

So … which way does it go?

•  The phospholipids are arranged so that the hydrophobic "tail" regions are shielded from the surrounding polar fluid, causing the more hydrophilic "head" regions to associate with the cytoplasm and extracellular fluids.

•  This arrangement prevents polar solutes (e.g. amino acids, nucleic acids, carbohydrates, proteins, and ions) from diffusing freely across the membrane.   This allows the cell to control the movement of these

substances via transmembrane protein complexes such as pores and gates.

Integral membrane proteins

•  Functions of membrane proteins can include cell-cell contact and two-way communication, surface recognition, cytoskeleton contact, signalling, enzymic activity, or transporting substances across the membrane.

•  Other proteins on the surface of the cell membrane serve as "markers" that identify a cell to other cells.

Cell Organelles

Nucleus:

•  Controls all cell structures •  Contains: chromosome/chromatin (DNA/

RNA)  DNA stays in the nucleus  RNA moves outside the nucleus

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Nucleus (cont.)

•  Surrounding the DNA is a double layer envelope called the nuclear envelope   Nuclear envelope is semi-permeable and has nuclear

pores •  DNA and RN are not enclosed they are separate

structures that move freely within the membrane •  DNA -> chromatin -> chromosomes (genetic

information)

Endoplasmic Reticulum:

•  Has both rough and smooth components •  The rough ER is embedded with

ribosomes •  Intercellular transport system

Ribosomes:

•  Located on the walls of the rough ER or free-floating within the cell

•  Manufacture site of proteins •  Site of protein synthesis

Golgi Apparatus:

•  Modify, package, and deliver proteins made by the ribosomes

•  UPS of the cell

Lysosomes:

•  Maintain environment •  Cleanup after the Golgi Apparatus •  Digestion and recycling center of the cell

•  Custodial/cleanup crew

Mitochondria:

•  Supplies the power for the cell •  Converts energy into ATP for use by the

cell

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Vacuole

•  Store nutrients and wastes of the cell •  In plant cells the vacuole is centrally

located and contributes to the shape of the cell

•  Storage unit

Cytoplasm:

•  Jelly-like substance within the cell •  Houses all the organelles •  Provides a water based medium for the

chemical reactions within the cell

Centrioles:

•  Look like a bunch of sticks or straws bound together

•  These are found only in animal cells and they aid in cell division/mitosis

Chloroplasts:

•  Are found only in plant cells •  They are the site of photosynthesis

  The conversion of sun energy into glucose molecules

Cell Wall:

•  Found in plant cells (also in bacterial cells) •  Gives shape, structure and protection to

the cell •  Rigid framework

Cell movement:

•  Flagella  Whip-like tail projection

•  Cilia  Many little hair like projections

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Cell Transport:

Objective:

•  The student will become familiar with the methods of transportation of materials into and out of the cell.

Questions of the day:

•  How do much needed nutrients get into the cell?

•  How does the cell know what can come in and what should not?

•  How do the biproducts of metabolism exit the cell?

Cell Membrane:

•  The function of the cell membrane is to regulate the flow of materials into and out of the cell.

•  The cell membrane is selectively permeable which allows only certain materials to be moved into and out of the cell.

Solutions:

• If we have a solution in which a solute is dissolved in a solvent that solution is said to have a certain concentration of the solute.

Solutions (cont.)

•  Isotonic state: when the concentration of a solute (usually salt) is the same as the normal cells of the body

•  Hypertonic: when the concentration of salt is higher than what is normal in body cells

•  Hypotonic: when the concentration of salt is lower than that of normal body cells

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Passive Transport:

•  Transport when no energy is expended by the cell

•  Transport proteins move substances down the concentration gradient (from an area of high concentration to and area of low concentration

Passive Transport:

•  Does not require energy  Diffusion  Osmosis   Facilitated Diffusion   Filtration

Diffusion:

•  Random movement of water molecules from areas of high concentration to areas of low concentration

Osmosis:

•  Osmosis is just the diffusion of water down the concentration gradient

Facilitated Diffusion:

•  Facilitator: encourages stuff to do things •  Integral membrane proteins enable things

to pass through the protein

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Filtration:

•  Bulk Transport •  Uses gravity or pressure to move

molecules

Active Transport:

•  requires energy •  Endocytosis:

 Movement of particles into the cell   Phagocytosis: cell eating   Pinocytosis: cell drinking

•  Exocytosis:  Movement of particles out of the cell   Elimination/pushing out of waste products

Phagocytosis: •  Phagocytosis is a form of endocytosis. •  In the process of phagocytosis the cell changes shape

by sending out projections which are called pseudpodia (false feet).

•  The phagocytic cell sends out membrane projections that make contact with some particle. The pseudopodia then surround the particle and when the plasma membrane of the projection meet membrane fusion occurs.

•  This results in the formation of an intracellular vesicle.

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phago.htm

Pinocytosis

•  Pinocytosis is the ingestion of dissolved materials by endocytosis.

•  The cytoplasmic membrane invaginates and pinches off placing small droplets of fluid in a pinocytic vesicle. The liquid contents of the vesicle is then slowly transferred to the cytosol.

http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/pinocyt.html

Cell Division:

Mitosis vs. Meiosis

Mitosis Remember the cell theory?

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Objective:

•  The student will become familiar with the steps involved with cellular division specific to mitosis.

Question of the day:

• Why do cells divide?

What is going on here? INQUIRY Mitosis:

•  Normal Cell Division •  All cells of the body (except gametes) undergo division

by mitosis •  Prophase, Metaphase, Anaphase, Telophase +

Cytokinesis = 2 new cells

•  Human cells have 23 pairs of chromosomes (46 total) •  In mitosis each successive cell continues to have 23

pair/46 total chromosomes

What is Mitosis? •  Mitosis is asexual

reproduction, the making of exact copies of cells (clones)

•  Cells division or doubling

•  The DNA must double first so each new cell gets the same DNA.

•  Mitosis occurs in eukaryotes.

•  Prokaryotes use a different method “fission” to divide.

Why do we need to make more cells?

•  Growth Injury Illness

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•  Chromosomes are single very long coiled strand of DNA found in the nucleus

•  This DNA contains all the genetic information for creating and running the organism.

•  Each chromosome has a central constricted region called a centromere that serves as an attachment point double DNA

•  Every organism has a set number of chromosomes:

•  Human=46 •  Corn= 20 •  Flies=10

Chromosomes More Chromosomes •  Chromosomes exist in 2

different states, before and after they replicate their DNA.

•  Before replication, chromosomes have one chromatid.

•  After replication, chromosomes have 2 sister chromatids,

•  They are held together at the centromere until mitosis is complete

The “C”s of Mitosis •  The chromosomes are

doubled and pulled apart by the spindle, which is made of microtubules.

•  Chromatids are single chromosomes. “sisters” are doubles

•  The centriole makes the spindle fibers for the DNA to attach to

•  a centromere is the center “button” where DNA attached to the spindle

•  There are 2 centrosomes, one at each end of the spindle. They pull the DNA apart.

C’s continued

Mitosis= I P M A T

•  5 SIMPLE STEPS TO REMEMBER

•  INTERPHASE •  PROPHASE •  METAPHASE •  ANAPHASE •  TELOPHASE

1. INTERPHASE

•  REST •  Cell is not doing

anything •  Chillin’

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Prophase Prophase

•  Prepare

•  1. DNA Doubles the nucleus gets dark and fat

•  2. The nuclear envelope disappears.

•  3. The spindle starts to form, growing out of the centriole

Metaphase

•  Metaphase

•  MIDDLE

•  Sister chromatids line up in the middle of the spindle

Anaphase

•  In anaphase

•  APART

•  Then the spindle fibers contract

•  The chromosomes are pulled to opposite poles.

•  Sisters split

Telophase •  In telophase

•  TWO

•  The cell actually divides.

•  The spindle disintegrates

•  The nuclear envelope re-forms around the two sets of chromosomes.

Cytokinesis

•  Cell membrane cleaves in the middle forming two cells

Cytokinesis during telophase

•  Cell cleavage

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Summary of Mitosis

•  Interphase: Rest

•  Prophase: Prepare

•  Metaphase: Middle

•  Anaphase: Apart

•  Telophase: Two

Cell Cycle •  The 3 stages of interphase

•  G1 (“Gap”1) is a rest before DNA doubles

•  The S phase (“Synthesis”) is the time when the DNA is replicated

•  G2 (“Gap” 2) is a rest before mitosis

Cancer: •  Cancer: uncontrolled cell/tumor growth •  Tumor: accumulation of cells when triggering device

doesn’t work well •  Oncology: study of cancer •  Oncologist: one who studies cancers •  Neoplasm: new growth •  Benign: non-cancerous growth •  Malignant: cancerous tumors •  Hyperplasia: abnormally high number of cells •  Metaplasia: change in cell •  Metastasis: spreading of cancer cells •  Carcinogens: agents that cause or trigger cancer (i.e.

Cigarettes, tobacco, formaldehyde, asbestos, radiation, the sun, etc.)

Cancer •  Cancer is a disease of uncontrolled cell division or mitosis . It starts

with a single cell that loses its control mechanisms due to a genetic mutation. That cell starts dividing without limit, and eventually kills the host.

Cancer Treatment

•  Two basic treatments: surgery to remove the tumor, and radiation or chemicals to kill actively dividing cells.

•  It is hard to remove all the tumor cells. Tumors often lack sharp boundaries for easy removal, and metastatic tumors can be very small and anywhere in the body.

•  Radiation and chemotherapy are aimed at killing actively dividing cells, but killing all dividing cells is lethal: you must make new blood cells, skin cells, etc. So treatment must be carefully balanced to avoid killing the patient.

Meiosis:

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Objective:

•  The student will become familiar with the steps necessary for meiosis which is responsible for the formation of gametes

•  The student will be able to compare mitosis and meiosis

Question of the day:

Meiosis:

•  Occurs only in reproductive cells or gametes  Male: sperm   Female: ovum

•  Results in haploid cells  Haploid: cells with 23 total chromosomes

How is the unique individual formed?

Gamete formation •  Gametes or sex cells are formed by

meiosis •  Meiosis is different from mitosis because it

results in what’s known as haploid cells  Haploid cells are cells that contain only half

the number of chromosomes that a normal body cells does (normal body cells are called diploid cells) Forma&on of Reproduc&ve Cells 

6.3 Gametes are Reproduc&ve Cells 6.4 Gametes have half the chromosomes  of body cells 

So, what is meiosis?

•  Meiosis is one replication of chromosomes followed by two divisions of chromosomes.

•  The replication of chromosomes occurs during the S phase of the cell cycle

•  The first division is called Meiosis I, the second is Meiosis II

6.5 Gametes are formed by Meiosis 

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Meiosis I •  Prophase I

  During prophase I the chromosomes “cross-over”   “Crossing over” results in a new combination of the

genes of the organism

h@p://www.phschool.com/science/biology_place/labbench/lab3/images/crossovr.gif 

Metaphase I

•  Toward the end of prophase I the chromosomes move toward the center of the cell, Metaphase marks the point at which the chromosomes line up along the midline of the cell

h@p://www.sci.sdsu.edu/classes/bio100/Lectures/Lect05/Image183.gif 

Anaphase I

•  In anaphase I the matching chromosomes of each pair separate and begin to move towards opposite ends of the spindle

h@p://www.phschool.com/science/biology_place/biocoach/images/meiosis/meana1.gif 

Telophase I

•  The chromosomes move to opposite ends of the cell and cytokinesis (cell splitting) occurs

h@p://www.phschool.com/science/biology_place/biocoach/images/meiosis/metel1.gif 

Meiosis II

•  Meiosis continues with a very brief Prophase II during which NO crossing over occurs

•  After Prophase II, Metaphase II occurs where the chromosomes again move toward the center of the cell and line up along the midline

h@p://www.synapses.co.uk/gene&cs/mandaii.gif 

Anaphase II

•  In anaphase II the centromeres divide and the two chromatids gather at opposite poles

h@p://www.synapses.co.uk/gene&cs/mandaii.gif 

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Telophase II. •  The chromosomes move to opposite ends

of the cell and cytokinesis (cell splitting) occurs

•  Each new cell has only half as many chromosomes as the body cell and therefore contains half of the parents total genetic information   This split and consequent reduction in the

number of chromosomes is known as a reduction division

Telophase II:

http://www.phschool.com/science/biology_place/biocoach/images/meiosis/metel2.gif