Download Cell Structure PPT

Cell Theory:
1. Every organism is composed of one or
more cells.
2. The cell is the smallest unit that has the
properties of life.
3. The continuity of life arises directly from
the growth and division of single cells.
Prokaryotic cell
Animal Cell
The Plasma Membrane
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Plasma membranes control what goes into
and out of the cell.
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Extremely thin
Fluid, fatty makeup
Flexible
Dynamic
The Components
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Phospholipid bilayer
Cholesterol
Protein
Glycocalyx
The Phospholipid bilayer
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Chief component of the plasma membrane
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Two fatty-acid chains
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Phosphate group
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Hydrophobic
Hydrophilic
Gives membrane its fluid nature
Only hydrophobic substances can pass
through
Cholesterol
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Keep membrane fluid
Act as a patching substance
Proteins
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Embedded within, lying on the phospholipid
bilayer.
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Structural support
Recognition, binding sites
Communication
Transport
Glycocalyx
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Simple carbohydrate chains, act as binding
sites for signaling molecules.
The Fluid - Mosaic Membrane
Model
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A conceptualization of the cell’s outer or
plasma membrane as a fluid, phospholipid
bilayer that has moving laterally within it a
mosaic of proteins.
Diffusion
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Random movement
Diffusion – movement from a region of higher
to lower concentration
Osmosis – the net movement of water across
a semi-permeable membrane from an area of
lower solute concentration to an area of
higher solute concentration.
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Hypertonic – when a fluid has a higher concentration of
solutes than the cell, water will flow out of the cell
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Isotonic – when a fluid has an equal concentration of solutes
than a cell, water be balanced
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Hypotonic– when a fluid has a lower concentration of solutes
than a cell, water will flow into the cell
Moving substances in and out of the cell
without the expenditure of energy
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Passive Transport
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Does not require expenditure of energy
O2 and CO2
Steroid hormones
Facilitated Diffusion
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Aided by a concentration gradient and transport
protein molecules
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Water
Active Transport requires the
expenditure of energy
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Generally requires the molecules to be
pumped against their concentration gradient
The energy source is ATP
Sodium-Potassium Pump
Exocytosis – movement out
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Movement of materials out of the cell through
the fusion of a vesicle with the plasma
membrane
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Exporting proteins
Exporting waste products
Endocytosis – movement in
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Pinocytosis – cell drinking
Receptor- mediated endocytosis – binds
specific molecules to receptor sites, forms a
vesicle and the substance is moved into the
cell.
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Cholesterol
Phagocytosis – getting rid of
the big stuff
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The cell sends out extensions called
pseudopodia which surrounds the food.
Lysosomes move in, breaking down what is
inside the vesicle.
The path of protein
production in a cell.
The Nucleus
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The DNA contains the recipe to make the
protein. These recipes are called genes.
These instructions are copied onto a
messenger RNA molecule which moves to
the cytoplasm through the nuclear envelope’s
pores.
Nuclear Membrane
Ribosomes
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Where protein synthesis takes place.
The messenger RNA is transcribed into protein
language
Some ribosomes are free-floating, others migrate
towards the Endoplasmic Reticulum.
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Free floating ribosomes produce proteins used in the cells
cytoplasm or nucleus.
Rough Endoplasmic Reticulum manufactures proteins that
are secreted or exported out of the cell.
Endoplasmic Reticulum
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Rough ER has ribosomes.
Smooth ER does not have ribosomes.
The RER are responsible for modifying the
newly formed protein molecules.
Nucleolus
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Ribosomes are made of a
type of RNA called
ribosomal RNA. These are
manufactured in the
nucleolus and pass through
the nuclear pores into the
cytoplasm.
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Organelles are membrane bound
Organelles work together
One piece can bud off and float to a second
organelle
Fuse with a second organelle, releasing its
proteins
The Golgi Complex
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Distributes the proteins from the endoplasmic
reticulum
Proteins are sorted and packaged into
vesicles
The vesicles move to the plasma membrane
and the proteins are ejected (exocytosis)
Other Cell Structures
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Smooth Endoplasmic Reticulum
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Synthesis of lipids, site of detoxification of harmful
substances
Testosterone and estrogen, alcohol
Lysosome
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An organelle that digests worn out cell parts,
foreign materials (cellular recycling)
As many as 40 enzymes that can break down
larger molecules
Mitochondria
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The organelle responsible for energy
conversion in eukaryotic cells.
Some cells have a few, some cells have
thousands
Mitochondria use oxygen
Theory of Endosymbiosis
The Cytoskeleton
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A network of protein filaments that function in
cell structure, movement, transport.
Some of the fibers are static (permanent) and
some are assembled and disassembled
rapidly.
Microfilaments, Intermediate filaments,
Microtubules.
Microfilaments
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The tiniest of the filaments of a cell.
Made of the protein actin.
Grow on one end and decompose on the
opposite end.
Responsible for changes in cellular shape.
Structure of microfilament
Intermediate Filaments
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Intermediate in diameter
Most permanent of the fibers.
Stabilize the position on organelles like the
nucleus.
Structure of intermediate filament
Microtubules
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The largest of the cytoskeletal filaments
Made of the protein Tubulin
Act as a structural filament, act as transport
for materials within the cell, Cilia and Flagella
are made of microtubules
Structure of microtubule
Flagellum composed of microtubules
The Plant Cell
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Similarities - Animal cell
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Nucleus, smooth and
rough endoplasmic
reticulum, other
organelles
Cytoskeleton
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Differences - Animal
cells
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No Lysosome
Thick cell wall
Large central vacuole
Chloroplasts
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The Cell Wall
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Can be very thick.
Made of cellulose and lignin
Control absorption of water.
Give the cell shape, structure.
Protect plant cells from harmful outside
influences.
The Central Vacuole
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Composed of mostly of water but also
includes nutrients, waste products.
A large watery plant organelle with several
functions.
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Storage area for nutrients
Retention and degradation of waste products
Cellular Communication
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Cells are organized into structures called
tissues.
Cells have the ability to communicate with
each other.
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In plants they are called plasmodesmata
In animals they are referred to as a gap junction.
Terminology for an
Introduction to Genetics
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Genome – the complete collection of an
organism’s genetic information. Each cell
has a complete copy of the genome.
Genetics – the study of heredity
Gene – a segment of DNA that codes for one
single protein, it is transcribed into RNA.
Humans have about 30,000 genes.
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These genes carry the directions for making
proteins which are used for a variety of things.
The Physical Structure of DNA
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Deoxyribonucleic acid
The outer structure is a repeating series of
deoxyribose sugar and phosphate molecules.
These are held together by pairs of bases
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Cytosine, Guanine, Thymine, Adenine
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Cytosine always pairs with Guanine
Thymine always pairs with Adenine
Picture a ladder where the
sides are made of
alternating sugar and
phosphate molecules. The
rungs of the ladder are the
bases, joined in pairs
between the sides.
Each protein is coded for by
a unique series of bases.
Watson and Crick, 1953
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Using models and brainstorming, they
determined the structure of DNA.
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Rosalind Franklin and Maurice Wilkins
X-ray diffraction
Cell Division
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25 million cell divisions per second (in your body).
Cells die and need to be replaced.
More of a certain cell may be needed at one point in your
life.
The big picture
 DNA must be replicated, then divided into the two new
cells (mitosis)
 The cellular material must be duplicated and split among
the two new cells (cytokinesis).
DNA replication
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The strands of the double helix unwind and separate
between the bases.
Free-floating nucleotides bind to the original strand,
forming a complimentary copy of the DNA.
Each new DNA molecule will be made up of one old and
one new piece of DNA.
Chromosomes are only seen after the chromatin has
been duplicated, then condenses back into the
chromosome state. They are then ready to separate into
two new cells.
The importance of enzymes
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Helicase
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Unwind the DNA molecule
DNA polymerase
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Join the nucleotides as they are added.
Perform DNA editing.
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Error rate is 1 in 100,000 during replication
Error rate is 1 in billion after replication
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More on mutations later
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The Big Questions
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Why is it important to duplicate DNA exactly?
How is the structure of DNA versatile enough
to produce such a variety of proteins?
Chromosomes
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DNA is packaged in Chromosomes.
Different organisms have different numbers
of chromosomes.
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Humans have 46
Onions have 16
The DNA is bound up with protein molecules,
the resulting combination is called chromatin.
Chromosomes are made of chromatin.
Homologous pairs of
chromosomes
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We inherit one chromosome from our mother
and one from our father. The genes are
similar but not identical, the individual genes
can vary.
Each of us has 22 homologous pairs of
chromosomes called autosomes (non-sex).
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There is one set of sex chromosomes.
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If you are male you have 1 X and 1 Y chromosome.
Females have 2 X chromosomes.
Human Karyotype
A pictorial arrangement of a full set of chromosomes.
Mitosis and Cytokinesis
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The cell cycle or repeating pattern of growth,
genetic duplication, and division is seen in
most cells. There are two phases:
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Mitosis – the separation of the cell’s duplicated
chromosomal material.
Cytokinesis – physical separation of one cell into
two daughter cells.
The phases of Interphase
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G1 or gap-one – normal cell operations and
cell growth
S or synthesis phase –DNA replication.
G2 or gap-two - more cytoplasmic growth and
preparation for cell division
Phases of Mitosis
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Prophase
Metaphase
Anaphase
Telophase
Prophase
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Chromosomes become visible
The nuclear envelope begins to beak up
The centrosomes (duplicated) migrate to the
poles of the cell.
Spindle fibers begin to form
Metaphase
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The microtubules align the chromosomes at
the equator of the cell.
Anaphase
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The sister chromosomes separate, moving
toward the poles of the cell
Telophase
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Chromosomes unwind and lose their shape
Nuclear membranes reform
Cytokinesis
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Begins in Anaphase and completes in
Telophase
Filaments form a contractile ring along the
equator of the cell called the cleavage furrow.
Animal cell cytokinesis: Contractile ring
forms the cleavage furrow
How does cell division in Plant
cells differ from Animal cells?
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The plant cell does not divide using a
cleavage furrow.
The plant cell grows a new cell wall and
plasma membrane that run down the middle
of the parent cell.
This cell wall begins as a series of vesicles.
When the fuse they are called the cell plate.
Plant cell cytokinesis: Formation of cell plate
Prokaryotic cell division
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Bacteria have one single circular piece of
DNA, which is attached to their plasma
membrane
The cells grows a septum which will separate
the two cells.
The process is called Binary Fission.
The process is much faster, often a cell can
divide every 20 minutes.
Binary Fission in Bacteria
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Diploid – having two sets of chromosomes.
Haploid – Having one single set of chromosomes.
All the cells in an organism are somatic cells, cells
that will never become an egg or sperm. These
cells are diploid. (46)
Gametes are reproductive cells, they will become
either a sperm or an egg. (23)
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These cells undergo meiosis – a process in which a single
diploid cell divides to form haploid reproductive cells.
The egg (23) and the sperm (23) unite to form a
zygote (46).