Download Unit 3 cell - Kowenscience.com

The Study of the cell
Cell: 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
Schwann
Schleiden
CELL THEORY
3. All cells divide & come from old cells. (Virchow)
Virchow
Ocular Lens
Body Tube
Nose Piece
Arm
Objective
Lenses
Stage
Clips
Diaphragm
Stage
Coarse Adj.
Fine Adjustment
Light Source
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
So the object is 400 times “larger”
Objective Lens have
their magnification
written on them.
Ocular lenses usually magnifies by 10x
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
Cell
The basic unit of life
Tissue
Group of cells working together
Organ
Group of tissues working together
Organ System
Group of organs working together
Organism
Any living thing made of 1 or more cells
Eukaryotic Cell
http://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 Bilayer
Phospholipids can form:
BILAYERS
-2 layers of phospholipids with
hydrophobic tails protected inside
by the hydrophilic heads.
The PHOSPHOLIPID
BILAYER is the basic
structure 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
Flagella
Long 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 duplicate
 Chromosomes are not visible
 Nucleus 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 phase
 Looks 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)
Telophase (fourth)
Cytokinesis (fifth)
Interphase (sixth)
Prophase (first)
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