cell transport
DESCRIPTION
Cell Transport. Homeostasis Cell Membrane Vocabulary Diffusion and Osmosis Active vs. Passive Transport. Homeostasis. Homeostasis means maintaining a balance internally (inside a cell or organism) despite what is going on externally (outside the cell or organism). - PowerPoint PPT PresentationTRANSCRIPT
Cell Transport- Homeostasis
- Cell Membrane- Vocabulary
- Diffusion and Osmosis- Active vs. Passive Transport
Homeostasis Homeostasis means maintaining a
balance internally (inside a cell or organism) despite what is going on externally (outside the cell or organism).
Organisms must adjust to changes in the environment in order to survive or they could die!
Homeostasis For example, when you need to drink
water, your brain tells your kidneys to use less water in making urine so you can keep your blood flowing nicely (and then your brain tells you that you’re thirsty!)
Homeostasis Another example, if it is
below freezing outside, you must put on a heavy coat, gloves, double socks, a warm hat, ear muffs, and lots and lots of layers to maintain a healthy INTERNAL body temperature despite the EXTERNAL temperature
Homeostasis What structure maintains homeostasis
in our cells? How does it maintain homeostasis?
How?
The Cell Membrane
By controlling the passage of molecules, such as water, salts (ions), amino acids, carbohydrates, etc in and out of the cell.(it regulates what enters and leaves)
-through passive transport, & active transport -cell to cell communication!
The Cell MembraneThe Cell Membrane is: A phospholipid bilayer
Two layers made of proteins and lipidsPhospholipid Structure:
Polar Head (hydrophilic—”water loving”) Nonpolar Tails—(hydrophobic—”water
fearing”)Draw:
The Cell Membrane proteins embedded in the phospholipid
layers› some go all the way through both layers
(integral)› some are just on the inside of the membrane
or just on the outside of the membrane (peripheral)
cholesterol is a second lipid that’s also found inbedded in the phospholipid bilayer› helps keep the membrane fluid
The Cell Membrane Bilayer arrangement Draw:
The Cell Membrane There are 3 types of membrane proteins
imbedded or “floating” in the lipid bilayer, each with a different function:› transport—help molecules enter or leave the
cell› marker—identify the cell› receptor—allow cells to communicate (send
and receive messages)
The Cell Membrane1. Transport Proteins function as “gates/passageway” allow sugars, salts (ions), amino acids and
carbohydrates to cross the membrane channel proteins
› gated ion channels—gates that open/close in response to charged particles these are important in nerve cell
function, but we will not study them in detail
› carrier proteins—change shape to allow specific molecule to pass through the membrane when it binds to the carrier protein; some require energy (ATP), others do not require energy carrier proteins are important in
getting glucose into the cells http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm
The Cell MembraneMarker Proteins Cell’s “Name Tag” Protein sticks out of phospholipid
layer Often has carbohydrates attached
to outside end Functions in cell identification to
identify the cell to other cells and molecules
Important in › immunity—so various white
blood cells in your body do not mistake your cells for foreign cells
- blood typing – so you can’t receive just any ol’ type of blood
Blood Typing Continued each blood type is based on the
glycoproteins (protein-carbohydrate molecule) that stick up from the cell membrane. › type A – has a glycoprotein named antigen A› type B – has a glycoprotein named antigen B› type AB – has both antigen A and antigen B› type O – has no marker proteins (no
glycoproteins/antigens)
The Cell MembraneReceptor Proteins- primary
molecules involved in cell communication
Function as messengers Receive information from
the environment (extracellular fluid, blood, interstitial fluid) and transmit that info to the inside of the cell
Protein has specific shape/charge to only allow certain molecules (like hormones) to bond
Triggers a response in cell
http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm
http://www.d.umn.edu/~sdowning/Membranes/signalinganim.html
Click, hold, and drag slider to move forward, bckword, or slow down
Cell Membrane in step 1 a signal molecule (sometimes called a ligand) binds
to a receptor protein in the cell membrane› examples of signal molecules include insulin and testosterone
in step 2 the receptor protein has changed shape as a result of the signal molecule binding, which can cause additional changes or reactions inside the cell
after step 2, there are 2 possibilities: › step 3 says “cellular response” – an example of a cellular response is an
enzyme being activated to make a reaction happen for example, insulin binding to a receptor in a liver or muscle cell membrane
would tell the cell to start hooking together glucose into glycogen for storage› step 4 says “change in gene expression” – this means that a gene in the
DNA is going to be “read” and mRNA made (transcription will occur); this will ultimately result in the cell producing a particular protein for example, testosterone binding to a receptor protein in a skin cell could
tell the cell to begin producing hair and a male would then begin growing a beard
Cell Membrane it’s important to note that the binding of the signal
molecule (like insulin or testosterone) to the receptor is temporary; when it unbinds, the signal stops and the cell response (enzyme reaction or gene expression) stops; this is another way organisms maintain homeostasis (you don’t always want to store sugar, sometimes you want to break it down, so insulin is not always bound to your cells but is only released into the blood from the pancreas when blood sugar levels are high; when they’re low, another molecule called glucagon is released and would tell the cells to break down glycogen and release the glucose)
The Cell MembraneThe Cell Membrane is: Selectively permeable/semipermeable
permeable means particles, like molecules, can travel through
selectively or semi permeable means it only allows SOME things through and not others
The Cell Membrane This represents a selectively permeable
membrane. It allows (selects) certain things to pass
through it.
Is the membrane permeable to ? Is the membrane permeable to ?
The Cell Membrane Molecules pass through the cell
membrane in one of two general ways:› Passive Transport
Diffusion Facilitated Diffusion Osmosis
› Active Transport Vesicles Pumps
Cell Transport Vocabulary Molecule- the smallest unit
of a compound/substance› Cannot be seen with the
naked eye› 1 drop of water has
16,700,000,000,000,000,000,000 molecules of H20
› 1 grain of salt has 120,000,000,000,000,000 molecules of salt
Cell Transport Vocabulary
Concentration Gradient- an area of high concentration next to an area of low concentration
Low Concentration of Molecules
High Concentration of Molecules
Cell Transport Vocabulary Equilibrium is when there is an EQUAL amount of molecules on each side of the membrane
There is no net movementof molecules (you won’t SEE a change) but there is continuous movement of molecules back and forth through the membrane.
Passive Transport Passive Transport is when molecules
move from an area of HIGH concentration to an area of LOW concentration until equilibrium is reached.
Requires NO ENERGY! Examples:
› Diffusion› Osmosis› Facilitated Diffusion
Passive Transport Diffusion- the process by which molecules (“stuff”) spread
from areas of high concentration, to areas of low concentration
Molecules are said to go “down” or “with” the concentration gradient.
Requires no energy
Air Freshener Diffusion in a Classroom
Where is the greatest concentration of cows? Where is the least concentration of cows? What will happen when the gate is opened?
This process is called…diffusion
Passive Transport Facilitated Diffusion
› What does facilitate mean?› When substances move from high to
low concentration (down the concentration gradient) using channel/carrier proteins located in membrane
› Does not require energy
Facilitated Diffusion Animation
http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.htmlClick, hold, and drag slider to move forward, bckword, or slow down
Passive Transport Osmosis- a special type of diffusion the process by which WATER
molecules move from an area with a high concentration of water to an area of low concentration of water across a membrane› the “diffusion of water”
Requires no energy
Passive TransportOsmosis- may be the passing of water through pores (spaces between the molecules of) in the
membrane -may be the passing of water through
special channel proteins called aquaporins (2003
Nobel Prize to Agre & McKinnon for this discovery)
Osmosis in biological systems, water is often the
only substance that can pass through a membrane
water moves INTO a solution with a HIGHER concentration of SOLUTE (molecules/particles)
water moves OUT OF a solution with a LOWER concentration of SOLUTE
Passive Transport water will move in where there is a low
concentration of SOLVENT (water), and a high concentration of SOLUTE (water)
› A solute = “stuff” (ions, glucose)› A solvent = “water” (you’ll learn about
different solvents in chemistry, but in biology the solvent is almost always water)
Osmosis
Semi-
Click to open web page with interactive animation
How osmosis works (click here or picture to go to video)
Passive Transport Animation
http://sites.sinauer.com/cooper5e/animation0202.html
Passive Transport There are three words use
to compare and describe solutions:› Hypotonic- water moves
INTO a cell and the cell swells (gets bigger)
› Hypertonic – water moves OUT of a cell and the cell shrinks (gets smaller)
› Isotonic- water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving)
Passive TransportHypotonic- describes a solution that is
less CONCENTRATED (has less solute, more water)
when a cell is placed in a hypotonic solution, the cell will swell as water moves INTO the cell
there is more solvent/less solute on the outside of the cell than the inside
the solvent (water) moves to an area of low solvent (water) concentration
the cell could burst (lyse)
Passive TransportHypertonic- describes a solution that is
more CONCENTRATED (has more solute, less water)
when a cell is placed in a hypertonic solution, water moves OUT of a cell and the cell shrinks(gets smaller)
there is less solvent/more solute on the outside of the cell than the outside
the solvent (water) moves to an area of low solvent (water) concentration
Passive TransportIsotonic: describes a solution that is of
equal concentration to another
water moves into AND out of a cell at an equal rate (remember- molecules are constantly moving)
No change in the size of the cell will be observed
the concentration of solvent and solute on the inside of the cell is equal to the concentration of solvent and solute on the outside of the cell
Practice Draw arrows to show the flow of water Label at the top if the solution is
isotonic, hypotonic or hypertonic
selectively permeable membrane
Where is the greatest concentration of solvent? Outside of the bag
What type of solution is this?Hypotonic
Which way does the water move?
Into the Bag
10% salt90% water
Where is the greatest concentration of solvent?
In the bag
selectively permeable membrane
Which way does the water move?
Out of the bagWhat type of solution is this?
Hypertonic
What happens to the bag?
selectively permeable membrane
90 % solvent10% salt
What happens to the bag?
selectively permeable membrane
90 % solvent10% salt
What happens to the bag?
selectively permeable membrane
90 % solvent10% salt
What happens to the bag?
The bag shrinks.
selectively permeable membrane
90 % solvent10% salt
Passive Transport Recap! Passive transport:
› requires no energy› moves from high concentrations to low
concentrations› Moves down the concentration gradient› Includes diffusion, facilitated diffusion and
osmosis
Active Transport When molecules are moved from a low
concentration to a high concentration they must use active transport› Cells must transport certain amino acids, sugars,
etc. into their cytoplasm from the surrounding fluid.
› Some of these substances, however, are already in higher concentrations inside versus outside.
Forcing molecules to move against their concentration gradient requires energy (ATP!)
Active Transport Vesicles can transport molecules across
the cell membrane through:› Endocytosis- moving INTO the cell› Exocytosis- moving OUT of the cell
Requires energy
Active Transport Exocytosis can help get rid of wastes or
secrete products like hormones or insulin Requires energy
Types of Endocytosis
Pinocytosis (drinking) Phagocytosis (eating)
Active Transport Pumps force molecules to travel
against their concentration gradient For example, the sodium/potassium
pump actively transports sodium molecules and potassium molecules through the cell membrane
Requires energy
http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm
Active Transport
Na+ pumped out of a cell K+ pumped into a cell Important because it
prevents cells from bursting by lowering the sodium inside causing less water to enter through osmosis.
Requires energy
Sodium Potassium Pump
http://sites.sinauer.com/cooper5e/animation1302.html
Transport proteins Cell transport involves proteins that
require ATP for energy These carrier proteins change shape to
move molecules across the membrane Another important way to move
glucose into the cell uses transport proteins combined with an ion pump, this is called coupled transport
Active Transport Opposite of Passive Transport Molecules go against the concentration
gradient Energy is provided by the ATP made in
the mitochondria Active transport can involve pumps or
vesicles Requires energy
http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm
Reviewwith
Animations!
http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm
The Cell MembraneReceptor Proteins- primary
molecules involved in cell communication
Function as messengers Receive information from
the environment (extracellular fluid, blood, interstitial fluid) and transmit that info to the inside of the cell
Protein has specific shape/charge to only allow certain molecules (like hormones) to bond
Triggers a response in cell
http://personal.tmlp.com/Jimr57/textbook/chapter3/cms2.htm
Passive Transport Diffusion- the process by which molecules (“stuff”) spread
from areas of high concentration, to areas of low concentration
Molecules are said to go “down” or “with” the concentration gradient.
Requires no energy
http://www.d.umn.edu/~sdowning/Membranes/signalinganim.html
Click, hold, and drag slider to move forward, bckword, or slow down
Passive Transport Facilitated Diffusion
› What does facilitate mean?› When substances move from high to
low concentration (down the concentration gradient) using channel/carrier proteins located in membrane
› Does not require energy
Facilitated Diffusion Animation
http://www.d.umn.edu/~sdowning/Membranes/diffusionanimation.htmlClick, hold, and drag slider to move forward, bckword, or slow down
Click to open web page with interactive animation
How osmosis works (click here or picture to go to video)
Passive Transport Animation
http://sites.sinauer.com/cooper5e/animation0202.html
http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm
Sodium Potassium Pump
http://sites.sinauer.com/cooper5e/animation1302.html
Types of Endocytosis
Pinocytosis (drinking) Phagocytosis (eating)
http://www.goldiesroom.org/Note%20Packets/06%20Transport/00%20Transport--WHOLE.htm