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Cells
Cell Theory
• All organisms are composed of one or more
cells
• Cells are the smallest units of life
• All cells come from pre-existing cells
Functions of Life
• Metabolism – all chemical rxn occur in organism
• Growth – grows in any amount
• Reproduction – cells with offspring
• Response – seek survival
• Homeostasis – consistent internal environment,
pH and temp
• Nutrition – intake of energy
Order of Size in a Cell
• Organelles*
Largest
• Bacteria
• Membrane
• Viruses
• Molecules
Smallest
How can we see these
things?
• Light Microscope
• Electron Microscope
*Limiting Cell Size
• Surface area – intake of nutrients
• Volume – energy, waste
*Cell Reproduction
• Maintain life
• Pass down genes
• Replace dead cells
• Genes are segments of DNA on a chromosome
Types of Cells
• Bacteria*
• Animal*
• Plant*
*Mitochondria vs.
Chloroplasts
• ATP formation
• Double Membrane
• Its own DNA
• Ribosomes
• Mitochondria has crista
• Chloroplast has granum
Stem Cells
• Stem cells are cells that retain the ability to
divide and differentiate into various cell types.
*Prokaryotic Cells
• Cell wall
• Plasma membrane
• Flagella
• Pili
• Ribosomes
• Nucleoid
*Eukaryotic Cells
•
Larger and more complex than prokaryotic cells
•
Endoplasmic reticulum*
•
Ribosomes* Lysosomes
•
Golgi apparatus*
•
Mitochondria
•
Nucleus
•
Chloroplasts
•
Centrosomes
•
Vacuoles
*Magnification
• A student observes a cell and draws it, using a
high power lens of a light microscope. The
diameter of the drawing is 10mm. The actual
diameter of the cell is 10μm. What is the
magnification of the drawing?
• Magnification=size of image ÷ size of specimen
*Cell Division
• The Cell Cycle
• Mitosis
*The Cell Cycle
• Interphase
• G1 phase
• S phase
• G2 phase
• Mitosis
•
•
•
•
Prophase
Metaphase
Anaphase
Telophase
• Cell division
• Cytokinesis
• Cell division
*Tumour
• Cells that multiply rapidly form a solid mass of
cells is called a tumour.
• Damage or error occur within the cell will
cause this to happen
Interphase
• Longest phase in the cell cycle
• G1, S, G2
G1 is known as “Gap phase one” or “the growth phase
one” where cell increases in mass with increase
number of organelles
S phase is the “Synthesis phase” where main part of
replication occurs, replication of chromosomes
G2 is known as “Gap phase two” or “growth phase
two” where there is an increase in volume and mass in
the form of increase of organelles are development of
chromosomes and microtubules begin to form for
preparation for mitosis
Mitosis
• Mitosis is also known as the “M phase”
• There are four phases in mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
Tip: P-Mat is an easy way of memorizing this order
Prophase
• The chromatin fibers become more tightly coiled to
form chromosomes
• The nuclear envelope disintegrates and nucloli
disappears
• The mitotic spindle begins to form and is complete at
the end of prophase
• The centromere of each chromosome has a region
called the kinetochore that attaches to the spindle
• The centrosomes move toward opposite poles of the
cell due to lengthening microtubules
Metaphase
• The chromosomes are moved to the middle or
equator of the cell. Known as the metaphase plate
• The chromosome’s centromeres lie on the plate
• The movement of chromosomes is due to the
action of the spindle which is made of
microtubules
• The centrosomes are now at the opposite poles
Anaphase
• This is usually the shortest phase of mitosis. It begins when
the two sister chromatids of each chromosome are split
• These chromatids, now chromosomes, move toward the
opposite poles of the cell
• The chromatid movement is due to shortening of the
microtubules of the spindle
• Because the the centromeres are attached to the
microtubules, they move towards the poles first
• At the end of this phase , each pole of the cell has a
complete, identical set of chromosomes
Telophase
• The chromosomes are at each pole
• A nuclear membrane envelope begins to reform
around each set of chromosomes
• The chromosomes smart to enlongate to form
chromatin
• Nucleoli reappear
• The spindle apparatus disappears
• The cell is elongated and ready for cytokinesis
*Cytokinesis
• Cytokinesis is not part of mitosis but follows after
mitosis
• Animal cells the cell involves an inward pinching of
the plasma membrane to form cleavage furrow.
• Plant cells the cell involves a cell plate
• Results are two identical daughter cells that are
identical to the parents (contains same number of
chromosomes)
*Membranes
• The structure of cell membranes are
composed of proteins and
lipids(phospholipids)
• The outer cell membrane is called the plasma
membrane due to the phospholipid bilayer
member
Phospholipids
• Phospholipids are the back bone of the membrane
• Phospholipid structure is compose of glycerol
which is a three carbon compound with two of the
carbons having a fatty acid tail and third contains
an alcohol with a phosphate group attached to it
• Fatty acids are non-polar therefore resists water.
Hydrophobic
• The alcohol phosphate group is water tolerant
because it is polar. Hydrophilic
Cholesterol
• Only in animal
• Cholesterol is located in the bilayer of the cell
membrane, the hydrophobic region, where the
fatty acids are located
• These molecules role is membrane fluidity, which
changes with temperature
• Fluidity is the rate that objects can past through
the membrane, higher the temperature the more
easily things can past through
Proteins
• There are two major types of proteins: integral
protein and peripheral protein
• Integral protein is hydrophobic and
hydrophilic, the hydrophobic region hold the
protein in place
• Peripheral protein is only hydrophilic,
therefore remains outside the membrane,
these proteins are anchored to the member by
integral protein
*
*
*Membrane Protein
Function
• Hormone binding sites
• Enzymatic action
• Cell adhesion
• Cell-to-cell communication
• Channels for passive transport
• Pumps for active transport
Hormone binding sites
• Proteins that expose their exterior in a
particular way to fit perfectly with a
hormone(binding) to relate a message to the
interior of the cell.
Enzymatic Action
• Cells have enzymes attached to membranes
that catalyse many chemical reactions.
• Often relates to the metabolic pathway
Cell Adhesion
• Cell adhesion is provided by proteins when
they hook together various ways to make
connection.
• Gap Junctions or Tight Junctions
Cell-to-cell
Communication
• Includes many molecules of carbohydrates
• Provides an identification label representing
cells of different species
Channels for passive
transport
• Provides a channel for substances to pass
through the membrane from a high
concentration to low centration
Pumps for active
transport
• Proteins shuttle a substance from one side of
the membrane to the another by change
shape
• Requires energy
Passive Transport
• Passive transport does not require energy(ATP)
• Passive transport occurs when there is an area of
high concentration of a substance moves to an
area of low centration.
• The substance moves along what is called the
concentration gradient.
• Diffusion and Osmosis are examples of passive
transport
Diffusion
• Particles of any type move from a region of
high concentration to a region of low
concentration
• Examples are oxygen diffusing into the cell
while carbon dioxide diffuses out the cell
Osmosis
• Osmosis involves only the passive movement of water
molecule across a partially permeable membrane
• A partially permeable membrane is one which only
allows certain substances to pass through
• Hyperosmotic concentration is the concentration of
high solutes
• Hypo-osmotic concentration is the concentration of
low solutes
• Concentration exchange ends when everything
reaches equilibrium
Size and Charge
• Substances that are small in size and non-polar
move across membranes with ease. Gases like
oxygen, carbon dioxide, and nitrogen fit in this
category and water glycerol
• Substances that are polar and/or large in size
have difficulty passing through the membrane.
Examples of these are chloride ions, potassium
ions, sodium ions, glusose, and sucrose.
Active Transport
• Requires energy in the form of ATP
• Active transport moves against the
concentration gradient
• Facilitated diffusion is an example of active
transport
*Facilitated Diffusion
• Facilitated diffusion is a particular type of
diffusion involving a membrane with specific
carrier proteins that are capable of combining
with the substance to aid its movement.
• The carrier protein changes shape to bind to
the protein needed for transport.
• Carrier protein requires energy to move
against the concentration gradient
Sodium-Potassium Pump
• A specific protein binds to three intracellular sodium ions
• Binding of sodium ions causes phosphorylation by ATP
• The phosphorylation causes the protein to change its
shape, thus expelling sodium ions to the exterior
• Two extracellular potassium ions bind to different regions
of the protein and this causes the release of the phosphate
group
• Loss of the phosphate group restores the protein’s original
shape thus causing the release of the potassium ions into
the intracellular space
*Endocytosis
• Endocytosis allows macromolecules to cross
the cell membrane
• Endocytosis occurs when a portion of the
plasma membrane is pinch off to enclose
macromolecules or particulates
• The pinching of the membrane changes the
shape of the membrane
• The result of this is a formation of a vesicle
*Exocytosis
• Exocytosis usually begins in the ribosomes of the
rough ER and progresses through a series of four
steps until the produced substance is secreted to the
environment outside the cell.
• Protein produced by the ribosomes of the rough ER
enters the lumen of the ER
• Protein exits the ER and enters the cis side or face of the
Goli apparatus; a vesicle is involved
• As the protein moves through the Goli apparatus, it is
modified and exits on the trans face inside the vesicle
• The vesicle with the modified protein inside moves to
and fuses with the plasma membrane – this results in the
secretion of the contents from the cell