Download Ch. 3 Cells Power Point

Chapter 3:
Cells
Cell Theory
•
Term “cell” was coined in 1665 by Robert
Hooke when he looked at a slice of dried
cork. He also observed that:
1. All living things are comprised of cells.
2. Cells are the smallest “living” unit in an organisms.
3. Cells come from previously existing cells.
Other points:
Cells of all living things carry on similar chemical
activities.
All cells carry on their metabolic activities in organelles
There are two types of cells:
1. Prokaryotic- cells that DO NOT have a
nucleus or other cell ORGANELLES
2. Eukaryotic- cells with a NUCLEUS &
cell ORGANELLES
•
Which is more complicated?
•
REMEMBER YOU ARE EUKARYOTIC!
Cell Diversity
• Lots of shapes and sizes
Typical Cell
Cell Organization
Cell Organization
•
The cell includes two basic parts:
1. Cell Membrane (outer covering of cell)
2. Cytoplasm
• Cytosol (fluid portion of the
cytoplasm)
• Organelles (cell “organs” or
functional parts)
Cell (Plasma) Membrane
• Cell Membrane Video
– Cell Membrane by Bozeman Science
• http://www.youtube.com/watch?v=S7CJ7xZOjm0
– Identify 3 key characteristics of the plasma
membrane (13, 14, 15)
Cell (Plasma) Membrane
• Outer boundary
• Comprised of two layers of
lipids/fat – Phospholipid bilayer
(Outer and inner layers)
– Hydrophilic- attracts water
– Hydrophobic- repels water
Forming a bilayer
satisfies the water
preferences of both the
“heads” and “tails” of
phospholipids: the
hydrophilic heads face
the watery regions inside
and outside the cell, and
the hydrophobic tails
face each other in a
water-free junction. The
bilayer forms
spontaneously because
this situation is so
favorable.
Cell (Plasma) Membrane
• The cell membrane is SEMI-PERMEABLE
– selectively regulates the flow of materials to
and from the cell--thus maintaining chemical
homeostasis within the cell
– The membrane acts like a BOUNCER only
allowing certain things in and out of the cell
Cell (Plasma) Membrane:
Globular Proteins
• Contain globular proteins
– Proteins give the cell its unique “personality” or function
– transport through the plasma membrane likely occurs
through these globular proteins (Fluid mosaic model)
– According to the fluid-mosaic model of the cell
membrane, special proteins called membrane proteins
float in the phospholipid bilayer like icebergs in a sea.
– The sea of phospholipid molecules and gatekeeper
membrane proteins is in constant motion. The
membrane’s fluidity keeps the cell from fracturing when
placed under strain.
Cell (Plasma) Membrane:
Globular Proteins
• Proteins embedded in membrane serve different
functions
1. Channel Proteins - form small openings for molecules
to diffuse through
2. Carrier Proteins- binding site on protein surface
"grabs" certain molecules and pulls them into the cell
3. Receptor Proteins - molecular triggers that set off cell
responses (such as release of hormones or opening of
channel proteins)
4. Cell Recognition Proteins - ID tags, to identify cells to
the body's immune system
5. Enzymatic Proteins - carry out metabolic reactions
Cell (Plasma) Membrane:
Globular Proteins
Cell Membrane
Cell (Plasma) Membrane:
Junctions
• plasma membranes of adjacent cells are pressed
together. Four kinds of junctions occur
– tight junctions – impermeable junctions that bind
cells together into leak proof sheets that prevent
substances from passing through the extracellular
space between cells (prevent digestive enzymes
from seeping into blood stream)
– desmosomes– anchoring junctions that prevent cells
subjected to mechanical stress from being pulled
apart (skin cells)
Cell (Plasma) Membrane:
Junctions
– gap junctions – allows communications to pass
directly through gaps (hollow cylinders) from one
cell to another (heart and embryonic cells)
– adheren junctions -provides strong mechanical
attachments between adjacent cells, holds cardiac
muscle cells tightly together as the heart expands
and contracts, holds epithelial cells together
Cell Organization
Cytoplasm
• fluid like material between the cell membrane
and the nucleus
• over 80% water
• “HOLDS” cell organelles in place
• site of most organelles and cellular chemical
reactions
• Is comprised of:
1. Cytosol - fluid portion of the cytoplasm
2. Organelles - cell “organs” or functional
parts
Cytosol
• Intracellular fluid
• Contains inclusions - nonliving
components of the cell that do not possess
metabolic activity, may or may not be
present, nonfunctioning, are commonly
stored nutrients or cell products (glycogen
granules, fat droplets, skin pigmentmelanin)
Organelles
• little “organs” of the cell
• Carry out cellular functions!
• Cell Organelle Video
– A Tour of the Cell by Bozeman Science
• http://www.youtube.com/watch?v=1Z9pqST72is
Organelle: Nucleus
• Control center of cell
• Contains DNA/chromosomes
– Chromatin -scattered through the nucleus,
eventually form rod-like bodies-chromosomes
when cell divides
• self duplicating structure -divides when the cell
divides
• Genes control the synthesis of proteins in each cell.
• Red blood cells don’t have a nucleus.
• Skeletal muscle cells have multiple nuclei.
Nucleus
Nuclear membrane (envelope)
• surrounds nucleus allowing certain
materials to enter and leave (Semipermeable)
Organelle: Nucleolus
• round organelle in the nucleus
• involved with the synthesis of RNA in the
ribosomes
Organelle: Cytoskeleton
• Cytoskeleton –cell’s “bones and
muscles”, internal framework that
determines shape, supports other
organelles and provides for intracellular
transport and various cellular
movements.
Cytoskeleton
• Made up of three elements, from largest to
smallest elements
– microtubules – determine overall shape and
distribution of organelles
– intermediate filaments – help form
desmosomes and aids in resisting pulling
forces on the cell
– microfilaments – (such as actin and myosin)
involved in cell motility and producing
changes in cell shape
Cytoskeleton
Cytoskeleton
The following are two
fluorescence images of
cells stained to show
the cytoskeleton
http://www.microscopyu.com/small
world/gallery/index.html
Organelle:
Endoplasmic Reticulum (ER)
• A network of membrane-bound tunnels
throughout the cytoplasm - cytoplasmic
channels from the cell membrane to the
nuclear membrane
• associated with the storage, synthesis, and
transport of materials within the cell
• “HIGHWAY” for cell transport
Endoplasmic Reticulum (ER)
• There are two forms of ER
– Rough ER – the “membrane factory” studded
with ribosomes, essentially all building
materials of cellular membranes are formed
either in it or on it
– Smooth ER – plays no role in protein
synthesis, functions in cholesterol synthesis
and breakdown, fat metabolism and
detoxification of drugs
ER
Rough ER
Smooth ER
ER
Organelle: Ribosomes
• sites of protein synthesis in the cytoplasm
• may be free in the cytoplasm or attached to
the endoplasmic reticulum
Organelle: Golgi Apparatus (Body)
• usually located near the nucleus
• synthesizes, packages, and secretes cellular
products
• Packages waste & harmful materials
Golgi Apparatus
Organelle: Mitochondria
• Bean shaped
• Outer and inner membranes - Inner membrane folded
into cristae
• “Powerhouse of the cell"
• Carries on cellular respiration - contains respiratory
enzymes that make ATP
– Adenosine triphosphate (ATP) produced on
cristae.
– ATP is high energy compound. (energy molecule)
– ATP only produced in mitochondria.
• Found in greater #s in active cells
Mitochondria
Organelle: Centriole
• Centriole- a cylindrical structure found in
the cytoplasm which appears to function
during the division of certain animal cells
(usually near the nucleus)
• Helps animal cells divide
Centriole
Organelle: Lysosomes
• Lysosomes -“break down bodies” –
contains powerful digestive enzymes
and function as cell’s “demolition site”
capable of digesting worn-out or nonusable cell structures. Abundant in
white blood cells to rid body of harmful
substances
Lysosomes
Organelle: Peroxisomes
• Peroxisomes - disarm dangerous
chemicals (free radicals- highly reactive
chemicals that can have devastating
effects on cells) in the body
Peroxisomes
Organelle: Vacuole
• membrane bound cytoplasmic spaces
containing materials
Two Types:
– Food vacuole--store and digest ingested food
– Contractile vacuole-pumps excess water from
cells maintaining homeostasis
Vacuole
Types of Transport in Cells
Video:
Transport Across Cell Membranes
• By Bozeman Science
– http://www.bozemanscience.com/016-transport-across-cellmembranes
Types of Transport in Cells
• Passive transport - movement of
substances through a membrane from a
region of high to a region of low
concentration - no energy needed (ATP) diffusion and osmosis are examples of this
• Active transport - movement of substances
through a membrane from a region of low
concentration to a region of high
concentration - requires cellular energy
(ATP)
Whether passive or active transport
is needed depends on the
CONCENTRATION GRADIENT
• The concentration gradient is the
difference in the concentration of a
substance in two different spaces
• Concentration - the amount of a particular
substance in a contained area compared
with the amount of the same substance in
another area
• Translation: Amount of something in a
space (water, salt, sugar, iron,)
Passive Transport
• There are two types of passive transport:
Diffusion and Osmosis
• The goal of both diffusion and osmosis is
to reach EQUILIBRIUM within the cell
• Equilibrium is a condition in which the
movement in one direction is equal to the
movement in another direction
Diffusion
• the tendency of molecules to move from an
area of higher concentration to an area of
lower concentration
• (concentration gradient- different in
concentration between 2 regions)
Osmosis
• movement of water through a membrane
from a region of higher to lower con.
• Solute - substance being dissolved in a
liquid (ex. salt)
• Solvent - substance doing the dissolving
(ex. water)
• Permeability - the extent to which a
membrane will allow particular sized
molecules to pass Semi-permeable
membrane (selectively permeable)-allows
some molecules to pass but not others
Osmosis
Think about it…
• So, describe how “Kool-Aid”® is made
with regard to the terms “solute” and
“solvent”. What is the “universal
solvent”?
And the answer is…
• Water is the solvent and the solute is the
kool-aid powder because it dissolves in
water resulting in a solution.
• Water is known as the “universal solvent”
Comparing Solutions
• Three possible relationships – based on determining
what would happen if a cell were placed in the
solution.
• Hypertonic- A solution that causes a cell to
shrink because of osmosis, meaning water
leaves the cell.
• Hypotonic- A solution that causes a cell to
swell because of osmosis, meaning water rushes
into the cell.
• Isotonic-A solution that causes no change in
cell size, meaning there is no movement of
water.
Hypertonic solution
Hypotonic solution
This can occur to such an extent that the cell actually
bursts to release its contents. This bursting of cells is
called lysis, and of a red blood cell, hemolysis
Isotonic solution
The normal Saline solution which is 0.9% NaCl is isotonic
with blood and is used in patients suffering from
dehydration or if they can't take any liquids or food.
Think about it…
• So, answer this question…. Why do
“establishments” offer free popcorn,
peanuts, and pretzels to their patrons if
they are serving beverages? What changes
are taking place in the body to initiate the
need for more beverages?
• What type of solution occurs?
• What form of membrane transport is taking place?
• What is the concentration gradient movement during
this membrane transport process?
Think about it…
• What type of solution occurs?
– Sodium in bloodstream creates a hypertonic solution
• What form of membrane transport is taking place?
– Osmosis
• What is the concentration gradient movement during
this membrane transport process?
– High to low movement of water across the cell membrane,
water form inside cell moving to outside cell.
And the answer is…
• After it is consumed, salt is absorbed into
your bloodstream. Salt acts as a magnet for
water, sucking it out of the body’s cells.
Water is polar and attracted to sodium's
electrical ions. The cells resist, but lose.
• Both your dehydrated cells and salty blood
send messages to the brain, asking for more
water to respectively quench and dilute. This
is why you become thirsty after eating salty
snacks
Facilitated Diffusion
• requires transport proteins in the cell
membrane to move materials into and out
of the cell either because the molecules
that are transported are too big or they are
polar (act against the nonpolar fatty acid
tail of the lipid bilayer)
Facilitated diffusion
• Channel proteins
provide corridors that
allow a specific particle
to cross the membrane.
• Carrier proteins undergo
a change in shape that
translocates the solutebinding site across the
membrane.
Active Transport
• the movement of a substance against the
concentration gradient. (uphill)
• Active transport requires cell to USE
ENERGY
Types of Active Transport
•
•
•
•
Sodium pump - transports three sodium
ions out of the cell and two potassium
ions into the cell
Both are against the concentration
gradient
The energy needed to perform this
activity is supplied by ATP (adenosine
tri-phosphate)
ATP is a unit of energy made by the cell
Types of Active Transport
• Endocytosis- the movement of a substance
into the cell by a vesicle. A vesicle is a
form of packaging that is used by cells.
– Phagocytosis- cytoplasm of cell surrounds
and engulfs particle--ex. ameba and white
blood cell
– Pinocytosis- plasma membrane "pinches in" to
permit entry of molecules too large to diffuse
through
• Exocytosis- the movement of a substance
out of the cell by a vesicle.
Endocytosis
Exocytosis