The Study of the cellCell: the smallest unit that can carry on all of life’s processes

CELL THEORY

A theory resulting from many scientists’ observations & conclusions

CELL THEORY 2. All living things are made of 1 or more cells.

Matthias Schleiden (botanist studying plants)

Theodore Schwann (zoologist studying animals) stated that all living things were made of cells

Schleiden

Schwann

CELL THEORY 3. All cells divide & come from old cells. (Virchow)

Virchow

Body Tube

Nose Piece

ObjectiveLenses

Stage Clips

Diaphragm

Light Source

Ocular Lens

Arm

Stage

Coarse Adj.

Fine Adjustment

Base

Skip to Magnification Section

Magnification

To determine your magnification…you just multiply the ocular lens by the objective lens

Ocular 10x Objective 40x:10 x 40 = 400

Objective Lens have their magnificationwritten on them.

Ocular lenses usually magnifies by 10x

So the object is 400 times “larger”

TOTAL MAGNIFICATION Powers of the eyepiece (10X) multiplied by objective

lenses determine total magnification.

Using a Microscope

Start on the lowest magnification Don’t use the coarse adjustment knob on high

magnification…you’ll break the slide!!! Place slide on stage and lock clips Adjust light source (if it’s a mirror…don’t

stand in front of it!) Use fine adjustment to focus

FROM CELL TO ORGANISM

CellThe basic unit of life

TissueGroup of cells working together

OrganGroup of tissues working together

OrganismAny living thing made of 1 or more cells

Organ SystemGroup of organs working together

Eukaryotic Cellhttp://www-class.unl.edu/bios201a/spring97/group6/eukcell.jpg

Parts of Eukaryotic Cells

Endoplasmic Reticulum

Nucleolus

Cytoplasm

DNA

Mitochondria

Vesicles

Golgi Complex

Ribosomes

Nucleus

Cell Membrane

- Parts of Eukaryotic Cells

CELL MEMBRANE (Plasma membrane)

Outer covering, protective layer around ALL cells

Allows food, oxygen, & water into the cell & waste products out of the cell.

CELL MEMBRANE (Plasma membrane)

The boundary of the cell…separates inside from outside of cell

Is Semipermeable Membrane: allows some substances into cell and keeps others out of cell.

CELL MEMBRANE (Plasma membrane)

Has a phospholipid bilayer. The lipid molecules are fluid and can move past one another in a fluid manner…also allows proteins to move and change in this layer thus scientist explain cell membrane and call it a Fluid Mosaic Model

Cell Membrane are made of a phospholipid bilayer

A Phospholipid BilayerPhospholipids can form:

BILAYERS

-2 layers of phospholipids with hydrophobic tails protected inside

by the hydrophilic heads.

The PHOSPHOLIPIDBILAYER is the basicstructure of membranes.

NUCLEUS Directs all cell activities Contains instructions for

everything the cell does These instructions are

found on a hereditary material called DNA

Usually the largest organelle

Parts of the nucleus

Nuclear envelope Nuceolus Nucleoplasm chromosomes

Actual Cell Nucleus

NUCLEOLUS

Aka “little nucleus” Found in the nucleus Contains RNA and

proteins for ribosome synthesis

CHROMATIN

contains genetic code that controls cell made of DNA & proteins Condenses to form chromosomes

during cell division

Made of DNA and proteins

Parts include: 2 sister chromatids

held together by the centrally

located centromere

Cytoplasm

gelatin-like inside cell membrane constantly flows aka protoplasm It contains the various

organelles of the cell

Contains the various organelles

Internal Organization:

Organelles = perform specific functions.- function like tiny organs, analogous to organs of a multicellular body.

Centrioles

Short cylinder near nuclear envelope There generally are 2 at right angles to

each other They control cell division

ENDOPLASMIC RETICULUM A series of folded

membranes that move materials (proteins) around in a cell like a conveyor belt

Smooth ER – ribosomes not attached to ER, functions in lipid synthesis

Rough ER – ribosomes attached to ER, functions in producing proteins

RIBOSOMES

Make proteins Float freely or attached to

the endoplasmic reticulum (ER)

Ribosomes are made in the nucleolus and are small particles of RNA

GOLGI BODIES (GAWL jee)

Stacked flattened membranes

Sort and package proteins

LYSOSOMES (LI suh sohmz)

The word "lysosome" is Latin for "kill body." The purpose of the lysosome is to digest things.

They might be used to digest food or break down the cell when it dies.

Break down food molecules, cell wastes & worn out cell parts

MITOCHONDRIA Organelles that release

energy from food (power house of cell)

This energy is released by breaking down food into carbon dioxide

the powerhouse b/c they release energy (ATP) from food

Folds of mitochodria are called:

VACUOLES

Temporary storage spaces

Store food, water, waste

CYTOSKELETON

scaffolding-like structure in cytoplasm that gives cell its shape

helps the cell maintain or change its shape

made of protein microfilaments and microtubules

Microfilaments

Built from actin, a globular protein and function in support of cytoskeleton and localized contraction of cell

Microtubules

Found in cytoplasm of all eukaryotic cells and function in cell support

Microbodies

Various membrane bound organelles that contain specialized teams of enzymes for specific metabolic pathways

important types: 1. peroxisomes: break down H2O2 and

detoxify alcohol

Intermediate filaments

Size intermediate to microtubules and microfilaments.

Function in reinforcing cell shape

Cilia

Short hair like projections from the cell that by beating produce organized movement.

Found in the trachea

FlagellaLong whiplike organelle

whose action produces movement.

Extracellular material

Found outside cell

Material secreted by cell into the cell matrix, ranging from saliva, to gastric juices, ext…

Transport through cell membranes There are 5 basic mechanisms:

1. DIFFUSION

2. OSMOSIS

3. ACTIVE TRANSPORT

4. FILTRATION

5. ENDOCYTOSIS

Diffusion is the net movement of molecules (or ions) from a region of their high concentration to a region of their lower concentration.

The molecules move down a concentration gradient.

Ex oxygen diffuses from RBC to cells body

Osmosis = Water diffusion, moving “down” the gradient

The net direction of osmosis depends on the solute concentrations on both sides.

Hypotonic = lower solute concentration

Hypertonic = higher solute concentration Isotonic = equal concentrations on both

sides of the membrane

Osmosis in Red Blood Cells

Active Transport

requires energy use to move materials up their concentration

Moves from an area of low concentration to an area of high concentration

Example: sodium-potassium pump Ex nerve cells transport sodium ions to

extracellular environment

Ion Pump for Na+ and K +

process by which cells ingest external fluid, macromolecules, and large particles, including other cells

Two Types of Endocytosis

- Pinocytosis = Cell drinking

- Phagocytosis = Cell eating

Exocytosis of Vesicle Contents

Filtration

Molecules pass through a membrane by physical force during filtration

Ex blood pressure forces substances to leave circulation

The process by which cells reproduce themselves.

Two types (Mitosis and Meiosis)

I. Mitosis = produces body cells with identical genetic material as the original.

II. Meiosis = reduces the chromosome number by half in the sex cells. (haploid)

Chromosomes – composed of 2 sister chromatids connected by centromere

During cell division in eukarotic cells the DNA is coiled into very compact chromosomes, made of both DNA and proteins.

Chromatid – each chromosome consists of two identical halves called chromatids (= copies

Chromatin - Before cell division, the DNA is not tightly coiled, but loosely arranged, and its codes can then be read by the cell to direct the cell’s activities.

chromosome

centromere

chromatids

Homologues or homologous chromosomes

* The cycle = repeating set of events composing the life of a cell.* There are two periods: Interphase and Cell Division

Interphase is the time between divisions, and is divided into three phases.

1. G1 phase – offspring cells grow to mature size

(= Gap after division and before DNA replication)

2. S phase – The DNA is copied 3. G2 phase – Gap after DNA synthesis &

before division.(The cell is preparing for division.)

* Cells can exit the G1cell cycle at G1 and enter a

state called Go phase. (In G0 , nerve cells for example stop dividing.)

Chromosomes duplicateChromosomes are not

visibleNucleus has clearly defined

nucleus

LOOKS SPAGHETTI LIKE, longest phase

The DNA which was copied in S phase, now supercoils.

Nucleolus and nuclear membrane break down.

Centrosomes with centrioles move to poles. (Plants have no centrioles.)

Spindle fibers (microtubules) radiate from them.

Mitotic spindle is this array of fibers.

Metaphase – CHROMOSOMES line up in a straight line in the center ( equatorial plane) of the cell .

Centromere of each pair of chromatids attaches to a separate spindle fiber.

Anaphase – centromeres & chromatids separate.

(Each new chromosome moves slowly to opposite poles

Shortest phaseLooks like they have wiped out

waters skiing

Plant Anaphase 3-D

Telophase – spindle fibers disassemble, chromatin forms, nucleus reappears.

(new nuclear envelope forms for each set of chromosomes

Cell plate forms in plant cell Cleavage furrows appear in animal

cells

Mitosis

Telophase Metaphase Prophase Anaphase

Cell Division Puzzle: Mitosis Unscramble it by labeling & numbering the stages.

Metaphase (second) Cytokinesis (fifth) Prophase (first)

Telophase (fourth) Interphase (sixth) Anaphase (third)

Meiosis is a process in which gonad cells divide twice to produce haploid cells.

* Gonads are sex organs (ovaries and testicles).

* Gametes (sex cells – sperm and eggs) are the resulting haploid cells.

* Cells preparing for meiosis first undergo the G1, S, and G2 phases of interphase.

Meiosis I and Meiosis II are the names for the two divisions of Meiosis. There are some important differences in

the stages compared to mitosis.

Exploring Meiosis

Meiosis I – Has four stages, plus Cytokinesis(Prophase I, Metaphase I, Anaphase I, Telophase I)

*

Similar to mitotic prophase except for Synapsis.

Synapsis is where the homologues pair up & twist around one another.

Tetrads is the term for these paired homologues (4 chromatids).

Crossing-Over then occurs where parts of the chromatids exchange genes.

Genetic Recombination is the result, which increases variation.

tetrads line up randomly at the mid-line of cell

- Spindle fibers from one pole attach to one centromere of one homologue.

- Spindle fibers from the other pole attach to the other homologue’s centromere.

* the spindle fibers randomly pull the homologues to separate poles.

- Independent Assortment is the term for the random separation.

- Note that the centromeres do not split the chromatids at this point.

- The homologous chromosome (consisting of two chromatids) stays intact.

Telophase I – is the final phase of Meiosis I, and the chromosomes reach the poles.

Cytokinesis then begins to separate the cytoplasm into TWO new cells.

At this point, the TWO new cells contain a Haploid number of chromosomes, yet each has two sister chromatids (copies) attached by a centromere.

Meiosis II - the DNA is NOT duplicated in meiosis II.

* Prophase II – spindle fibers form and begin moving chromosomes to midline.

* Metaphase II – chromosomes are at the midline, facing the poles.

* Anaphase II – chromatids separate at the centromeres and move to opposite poles.

* Telophase II & Cytokinesis results in four haploid cells, each with a single chromatid.

Formation of Gametes-

* Spermatogenesis = male testes cell produces four gametes called spermatids.

* Oogenesis = female ovaries produce eggs (ova), but only one ova (not four) is produced from the meiotic divisions of each ovary cell.

- The other three “donate” most of their cytoplasm to the one mature ova, so that it has plenty of

energy reserves to grow once it is fertilized by a sperm.

Cell Growth and Reproduction

DNA transcription to RNA Translation to protein

DNA contains the genetic info for making proteins

Cells make protein by translating the genetic codes into protein

So DNA controls life by controlling protein synthesis

Replication: DNA copies itself

Transcription: DNA copies to mRNA Translation: mRNA copies to tRNA to protein

3 Types of RNA: mRNA: found in the cytoplasm and specifies the

exact sequence of amino acid tRNA: acts as an interpreter molecule which

recognize specific amino acids and nucleotide base sequences

rRNA: forms part of the protein synthesis site in the cytoplasm

Synthetase enzymes: attach the correct amino acids to its transfer RNA