Cell Theory

Cell theory has three main principles1. All organisms are composed of one

or more cells 2. Cells are the smallest units of life3. All cells come from preexisting cells

Discrepancies: the cell theory( explain) Striated muscle cells

Algae

fungi

Unicellular Organisms

One cell only(move, drift, fixed) Must carry on life functions. Nutrition Metabolism Growth Response Excretion Homeostasis Reproduction

Limitations on cell size

Metabolism=large number of chemical reactions taking place within a living organism.

The rate of these reactions is proportional to the cell.

The rate and amount of materials absorbed and removed depend on the surface to volume ratio

Small ratio: cell can’t absorb or excrete materials quickly, the cell will also overheat easily because heat produced can’t be eliminated fast enough,

Limitations on cell size

Metabolic rate is proportional to cell volume.

Used materials (absorbed) Waste products(removed) Small cells overheat, slow entrance

of materials and wastes accumulate quickly

Multicellular organisms

Organisms consisting of a single mass of cell fused together.

Cooperative groups No one group is leader, they organize

themselves and interact with other groups to have one distinct purpose

Emergent properties

These are characteristics of the whole organism

Interaction of component parts of a complex structure

Cell differentiation

Different cells=different functions (job or role)

Groups of cells that specialize in the same way to perform the same function = tissue

Tissues= more efficient job Differentiation: development of cells

to carry out specific functions.

Gene expression and differentiation Every cell contains the same set of

genes. Some genes are activated (switched

on or being used) = production of a certain cell type.

Differentiation: different sets of genes are expressed and active. This is the key to development

Stem cells

Versatile and can differentiate along any pathway to produce any type of cell or tissue

1. divide many times = large quantities of new cells. Used to grow tissues or replace lost or damaged cells.

2. not fully differentiated so they can produce any cell type.

Embryonic stem cells

1. regenerate tissues for burn victims 2. type 1 diabetes treatment 3. grow replacement organs Therapeutic use: therapies or

treatments for disease or health issues.

Non therapeutic use: Production of meat without the cow.

Stem cells: early stages are very versatile.

Later stages they begin to commit to a growth pattern or differentiate.

They will still divide but all will develop in the same way. No longer a stem cell

Stem cells: found in adults Much repair: bone marrow, skin, liver Limited repair: brain, kidney, heart

Uses of stem cells Stargardt’s disease (genetic) Progressive loss of vision until blindness.

Use embryonic stem cells to treat. Leukemia: Cancer: several specific mutations occur

in one cell and that cell divides. Remove patients stem cells by needle

aspiration Chemotherapy Return stem cell to patients bone marrow

Ethical objections

1. informed consent 2. clear understanding by the patient

of the treatment involved P15 take your own notes in class

regarding the sources of stem cells 1. create an embryo( for that

purpose only IVF) (abortions) 2. cord blood 3. Adult tissue (e9 Bone marrow)

When does life begin

1. sperm fertilizes the egg (IVF) 2. early stage embryo has no human

characteristics, can’t feel pain so its ok 3. heartbeat, bone tissue, brain activity.

Usually seen a few weeks into development.

4. fetus stage = viable outside the uterus (24 to 28 weeks) Positive= reduction of the suffering of

diseased individuals.

Ultrastructure of cells resolution of microscopes Resolution: making an objects parts

distinguishable. Light microscope limited by the

wavelength of light Electron microscope ; higher

resolution the beams of electrons have shorter wavelengths to provide more resolution.

Used for viewing the ultrastructure of cells

Ernst Ruska: 1939 developed the first electron microscope. Used beams of electrons instead of light.

Difference between prokaryotes and eukaryotes

PROKARYOTES EUKARYOTES

No nucleus Simple cell structure Small in size Found everywhere

even in extreme conditions

Have cell walls Filled with cytoplasm No organelles

Nucleus: contains chromosomes

Nuclear membrane Cytoplasm that contains

organelles (analogous to organs) specialized functions.

Multicolor Ingest materials

(pinocytosis, phagocytosis)

prokaryotes eukaryotes

Do contain ribosomes Lack membrane bound

organelles DNA called a nucleoid Plasmid: an extra piece of

DNA, circular, contains nonessential genes that may be needed later

Gene for antibody resistance

Contain cilia and flagella

Sexual reproduction (The sperm is the only eukaryotes with flagella)

Compartments within the cell where the organelles are located

Advantage to compartments: concentration of molecules in one area

Prokaryotes Eukaryotes

Reproduction by binary fission (asexual reproduction) (mitosis)

EXAMPLES bacteria single celled organisms

Diffusion thru the cell wall

No compartments all cytoplasm

Contain ribosomes

Keep material separated

Maintains pH easily Organelles can move

around See page 21 for a

picture and description of each organelle

Activity

Draw both a Eukaryotic and Prokaryotic cell.

You will be given a whit piece of paper fold it in half. One half for each cell.

Draw the cell, Label the cell parts, annotate the organelles or parts of each cell.

Phospholipid layers

Hydrophilic: water attracting (phosphate) (head)

Hydrophobic: does not attract water (hydrocarbon chain) (tails)

Amphiphatic: has both properties. Proteins are dark in electron

micrographs and phospholipids appear light.

Protein globules were also discovered so the previous model was disproved (Davson-Danielli)

Singer Nicolson : fluid mosaic model

Evidence that falsified the Davson Danielle model

P27,28 Freeze etched electron micrographs Structure of membrane proteins Fluorescent antibody tagging

Membrane proteins

Proteins in the membrane prevent and slow the passage of materials

Active cells with have a higher protein content in the membrane

1. Integral Protein: hydrophobic and found on the hydrocarbon portion of the chain

Transmembrane: extends across the membrane. Hydrophilis part project thru the phosphate head on either side.

Channel protein Carrier protein

Peripheral protein these are not embedded in the membrane

Hydrophilic (they are attached to the surface of

an integral protein or to the hydrocarbon chain.

Internal cell communication

Lipid bound proteins: found within the bilayer of phospholipids

Glycoproteins: found anywhere and it consists of a sugar and protein together allows for cell communication

Cholestrol in membranes

Found only in anmial cell membranes Lipid = steroid category Hydrophobic = attracted to the

hydrocarbon chain Contain OH (hydroxyl group) so that

portion is hydrophilic and attracted to the phosphate head portion

Found between the phospholipids (p31)

FLUIDITY Distance between molecules

Temperature increases

increases Increases (molecules are lose

Temperature decreases

decreases Decreases (molecules cluster crystalize)

Cholesterol/ low temp

Fluidity increases Increases distance between Phospholipids

Cholesterol/ high temp

Fluidity decreases molecules are drawn in tighter

Saturated fats (single bonds between the carbon atoms)

Fluidity decreases Stacked together and closely

Unsaturated fats (double bonds between the carbon atoms

Fluidity increases The molecules don’t stack up together

The amount of cholesterol present varies amongst cells

Keeps the cells in a fluid state (from becoming crystallized)

Reduces permeability ( to other hydrophilic particles)

Allows(helps) the membrane to change shape so vesicles can be formed for transport.

Endocytosis

When a small region of the membrane is pulled in and pinched off.

Energy (ATP) is needed for the process

Vesicle formed contains materials from outside the cell (large molecules)

Can contain food (amoeba) Pathogens (WBC)

Vesicle

Allows movement of material and the vesicle itself within the cell membrane

Contents are taken to the area of need.

When you have an increased membrane size then you will see an increased size in the organelle

exocytosis

The vesicle fuses with the cell membrane and the contents are released outside the cell

Secretion: useful substances only Expel waste products Contractile vacuole: expels excess

water that has accumulated within the cell

Movement across the membrane by: Simple diffusion: materials move

from an area of high concentration to an area of lower concentration.

Down or with the concentration gradient

Materials pass thru the lipid layers charges on the molecule (atom) limits diffusion

Concentration gradient ?

Passive diffusion: no energy is needed.

Polar molecules have little or no charge on them so they diffuse easily.

2. Facilitated diffusion

Channels or holes are present in the cell membrane.

Properties of the proteins that line the channels decide which ions can pass and how many.

Osmosis

The movement of water freely in or out of the cell.

When an equal number of ions is reached there will be no movement

High solute content = low water Low solute content = high water Passive: movement of water with the

gradient (low solute=high water) low water = high solute

Small materials pass thru the phospholipid bilayer

Aquaporin: water channel (slightly wider than a water molecule so passage is easy)

Active Transport

Taking in of substances even though there is a high concentration already.

Materials are moving against the gradient

Define concentration gradient? This type of transport requires

energy (ATP which is a result of cellular respiration)

Sometimes material is pumped out inspite of the concentration difference.

Pump proteins carry out this type of transport (p38 note how it works)

P 39 and 40 Na K pump take notes.

Na/K pump Active transport Neurons Nerve impulses involve the rapid

movement of Na and K ion exchange.

3Na out and 2K in and this process uses 1 ATP

3Na enter the pump from inside the cell

The ATP causes the pump to change shape and close with the Na inside

The pump opens to the outside and the 3 Na ions are released into the environment

2K from the outside( enter and attach to the binding site) ( release a phosphate from the ATP)

The pump changes shape and opens - allowing the K ions to pass into the axon.

Potassium pump (facilitated diffusion) 4 proteins with a narrow passage

(material can pass either way) The potassium is bonded to water

which is too large to pass. The bonds must be broken and the K attaches to an amino acid.

K passes thru the membrane and reattaches to water, the amino acid will then block the opening

Voltage gated

More + outside (more – inside) the channels will be closed

More + inside (more – outside) the channels are open and rapidly close due to the presence of the amino acid.

Estimation of Osmolarity

= the total concentration of osmotically active solutes (These solutes are osmotically active: since they cannot pass through the membrane water has to move in order to equilibrate the osmotic pressures.)

ISOTONIC: same osmolarity as a tissue HYPERTONIC : higher osmolarity Many

dissolved solutes HYPOTONIC : lower osmolarity fewer

dissolved solutes

Preventing osmosis

Hypertonic high osmolarity Hypotonic low osmolarity

High solutes concentration low water. Water rushes from the cell causing it to shrink and crenellate

Low solutes concentration and high water. Water rushes into the cell causing it to swell and burst.

isotonicUses for normal saline

Water enters and leaves the cell at the same rate and no cell damage is seen

1. iv 2. wound rinsing 3. moisten skin 4. eye drops 5. frozen slush for

organ transplant

The origin of cells

Cells are formed from pre existing cells the genetic information was copied so that the two new cells had a full set of DNA (genes)

The zygote was the first cell of our life.

Scientists claim to have created a cell, however it was formed from the genes of a bacterium and merely modified to create a new species of bacterium

Spontaneous generation

Formation of living organisms from nonliving matter.

Many experiments designed to test this theory. Redi, Spallanzani, Pasteur.

Cells are highly complex, no way has been thought of to produce cells from simpler subunits

Cell division is the only way to increase the number of cells in an organism

Viruses are simpler subunits, they are not made of cells, they can only be produced inside a host cell that they have infected.

Origins of the first cell

Cells must have arisen from nonliving subunits.

Four hypothesis for the production of cells p48

Endosymbiosis and eukaryotic cells Mutualistic relationship: both parties

benefit Natural selection favors the organism

that can adapt and survive.

Endosymbiosis and eukaryotic cells Cellular organelles (mitochondria and

chloroplasts) were taken into larger cells thru endocytosis. (larger prokaryotes didn’t die)

They replicated themselves along or at the same rate as the larger cell (endosymbiosis)

Evolution now makes them a part of the cellular structure.

Symbiotic relationship: both organisms benefit from the contact.

Symbiotic and mutualistic relationship are the same thing.

This same theory applies to the presence of chloroplasts within a plant cell (the produce photosynthetic energy for eukaryotes

See page 50 for a diagram After much time these organelles are

no longer capable of independent living.

Features of mitochondria and chloroplasts that suggest they were capable of independent living.

1. 2. 3. 4.

Cell division Role of mitosis The cell divides into two daughter

cells, each with its own identical nuclei to the other.

The DNA must be replicated (during interphase) (before mitosis begins)

Double DNA replicated called chromatids.

INTERPHASE

The number of mitochondria and chloroplasts (PLANT CELLS AND ALGAE) increase. Synthesizing material to add to the cell wall (protein synthesis)

G1 phase: cellular contents other than DNA are duplicated

S phase: chromosomes are duplicated

G2 phase: Growth and preparation for cell division (lower SA to V so the cell can become bigger)

G0 phase: cells enter when they are not going to divide (temporary or permanent)

PROPHASE

Chromosomes undergo supercoiling (condensation) DNA becomes tighter and shorter more compact.

Nucleolus breaks down Microtubules form from MTOC

(microtubule organizing center) they will be linked to each pole of the cell.

End of phase nuclear membrane disappears. No nucleus can be seen, chromosomes are dispersed.)

METAPHASE

Microtubules grow and attach to centromere. Allows for the correct migration of the chromatids to opposite poles (sides of the cell)

Microtubules will shorten and contract, at this point if they are not attached the chromosome will remain in the center

ANAPHASE

Centromeres separate allowing for chromatids to separate.

Pulled rapidly by shortening of spindle fibers

TELOPHASE

Chromatids reached the poles now called chromosomes (uncoiled).

Pulled into a tight group and the nuclear membrane reforms around them.

Nucleolus reforms

CYTOKINESIS

Occurs when mitosis is complete. (starts a little before)

Animal cells plasma membrane pulls in forming a cleavage furrow.

Reaches the center pinches off and equal amounts of cytoplasm goes to each cell.

Plants cells the 2 plasma membranes are formed across the equator of the cell (cytoplasm has been divided)

Cell plates form and build into new cell walls for each of the daughter cell.

Please go online and look for different pictures of mitosis so you can begin to distinguish one phase from the next

CYCLINS

These are proteins that make sure everything moves to the next stage when the prior stage is complete

Cyclin dependent kinase: an enzyme that will bind to the cycline and become active

This allows the cell to be specific to one stage at a time.

Threshold concentration of cyclins is needed to proceed to the next level of mitosis

List the 4 cyclins and define what they do on the next slide

List the 4 cyclins and define what they do

Tumor formation

Tumor is any abnormal group od cells found in any part of the body at any age.

Benign tumor: the cells don’t spread and invade other tissues

Malignant when the tumor cells move to other tissues else where in the body. These are called secondary tumors.

The first tumor site is called the primary site.

Carcinogen: any chemical agent that causes cancer.

Mutagens are carcinogenic (chemicals, uv light, high energy x rays) These cause mutations which result in the formation of cancer.

Several mutations are needed to form a tumor cell.

The first tumor site is called the primary site ( first collection of tumor cells)

Metastasis : the movement of tumor cells to other tissues setting up a secondary site.

Smoking and cancer

Correlation: relationship between two factors

Positive correlation: one factor increases and so does the other

Negative correlation: one factor increases and the other factor decreases.

Correlation is a relationship Cause definite proved connection

between the two factors