Cellular Transport Notes (Text 7.2 p 175-178 & 8.1 p 194-200)
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Transcript of Cellular Transport Notes (Text 7.2 p 175-178 & 8.1 p 194-200)
Cellular Transport NotesCellular Transport Notes(Text 7.2 p 175-178 & (Text 7.2 p 175-178 &
8.1 p 194-200)8.1 p 194-200)
DefinitionsDefinitions
Cell membranes are completely permeable to water. The environment the cell is exposed to can
have a dramatic effect on the cell.
Solutions are made of solute and a solvent
Solvent - the liquid (water) into which the solute is poured and dissolved.
DefinitionsDefinitions
Solute: substance that is dissolved or put into the solvent (water). Common cell solutes include salts, sugars,
some minerals (iron ions and calcium ions) and protons (electrons from acids).
Eg. Sodium chloride dissolved in water makes a saline solution. The sodium chloride is the solute. The water is the solvent.
ConcentrationConcentration
amount of solute per unit volume of solution.
expressed in mass/volume (g/100ml - percentage), ppm (parts per million), and moles/volume (molarity).
The greater the mass or moles per unit volume, the more concentrated the solution.
Concentration GradientConcentration Gradient
Difference in concentration between solute molecules from area high concentration to area of low concentration.
The greater the difference the faster the rate of diffusion and vice versa i.e. the steeper the hill
Cellular MembraneCellular MembraneStructure and Structure and
FunctionFunction
All cells have a cell membrane Chiefly responsible for maintaining
homeostasis inside a living cell using different methods to transport molecules in and out of the cell.
TEM picture of a real cell membrane.
Cellular MembraneCellular MembraneStructure and Structure and
FunctionFunction
Too much water can burst the cell Too many wastes can poison the cell The cell cannot tolerate any great variations
in ion conditions.
TEM picture of a real cell membrane.
Jobs of the Cell Jobs of the Cell MembraneMembrane
1. Provides protection and support for the cell2. Regulate the exchange of substances (gases and
ions)
3. Communicates with other cells
4. Identification (proteins and carbohydrates on its surface)
TEM picture of a real cell membrane.
http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf
http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf
Proteins
Membrane movement animation
Polar heads love water & dissolve
Non-polar tails hide from water
Carbohydrate cell markers
Fluid Mosaic Model of the
cell membrane
Lipid Bilayer
- 2 phospholipid layers
a. Phosphate head is polar (hydrophilic – water loving)
b. Fatty acid tails non-polar (hydrophobic – water fearing)
c. Proteins embedded in membrane
Fluid PortionFluid Portion
Phospholipid
Lipid Bilayer
a. Selectively permeable: Allows some molecules in and keeps other molecules out
b. The structure helps it be selective!
Cell Membrane Pores Cell Membrane Pores
Pores
Outside of cell (interstitial)
Inside of cell (cytoplasm)
Proteins
Transport Protein Phospholipids
Carbohydratechains
Lipid Bilayer
Go to Section:
Animations of membrane of membrane
structurestructure
http://www.goldiesroom.org/AP%20Biology/AP%20Lecture%20Notes%20pdf/LN014--Ch05--Cell%20Transport.pdf
The different components of a plasma membrane are integral proteins, peripheral proteins, glycoproteins, phospholipids, glycolipids, and in some cases cholesterol, and lipoproteins.
Construction of the Cell Membrane - Learning Activity
detailed cell membrane animation
Proteins Embedded in Membrane Proteins Embedded in Membrane Serve Different FunctionsServe Different Functions
Transport Proteins regulate movement of substance
Channel Proteins form small openings for molecules to diffuse
through like water
Carrier Proteins binding site on protein surface "grabs" certain
molecules and pulls them into the cell animation
Gated ChannelsGated Channels similar to carrier proteins, not always "open"—
eg. Bind and pull in calcium ions when needed. This requires cell energy—active transport.
Receptor ProteinsReceptor Proteins
molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins)
e.g. The junction between nerve cells e.g. The junction between nerve cells requires the transmission of requires the transmission of neurotransmitters between synaptic gapsneurotransmitters between synaptic gaps—these chemicals bind onto receptor —these chemicals bind onto receptor proteins.proteins.
Recognition Proteins - ID tags, to identify cells to the body's immune system (called antigens)
TRANSPORT MECHANISMSTRANSPORT MECHANISMS
1. PASSIVE TRANSPORT
2. ACTIVE TRANSPORT1. ENDOCYTOSIS
2. EXOCYTOSIS
Types of Cellular TransportTypes of Cellular Transport
Passive Transport
doesn’t use energy
1. Diffusion
2. Facilitated Diffusion
3. Osmosis
Active Transport
uses energy
1. Protein Pumps
2. Endocytosis
3. Exocytosis
high
low
This is gonna
be hard
work!!
high
low
Weeee!!!
•Transport Animations
Passive Transport (p 198)Passive Transport (p 198) cell uses no energy molecules move randomly Molecules spread out from an area of
high concentration to an area of low concentration.
i.e. down a concentration gradient (High Low) Passive Transport Animation
3 Types of Passive Transport3 Types of Passive Transport
1. Diffusion – high conc. to low conc.
2. Facilitative Diffusion – diffusion with the help of transport proteins
3. Osmosis – diffusion of water
1. Diffusion1. Diffusion
random movement of particles from an area of high concentration to an area of low concentration.
(High to Low) Diffusion continues until all
molecules are evenly spaced (equilibrium is reached) Note: molecules will still move around
but stay spread out.
http://bio.winona.edu/berg/Free.htmhttp://bio.winona.edu/berg/Free.htm
Animation
1. Diffusion1. Diffusion
2. Facilitated Diffusion2. Facilitated Diffusion diffusion that is enabled
by proteins (channel or carrier proteins) which bind onto required molecules so that they flow into the cell. Transport Proteins are
specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules
Animation: How Facilitated Diffusion Works
Facilitated diffusion (Channel Protein)
Diffusion (Lipid
Bilayer)
Carrier Protein
A B
http://bio.winona.edu/berg/Free.htmhttp://bio.winona.edu/berg/Free.htm
High Concentration
Low Concentration
Cell Membrane
Glucosemolecules
Proteinchannel
2. Facilitated Diffusion
Go to Section:
Transport Protein
Through a
Cellular Transport from an area of High
Low
Channel Proteins animationsanimations
Diffusion of water through a selectively permeable membrane
From high to low concentrations
•Water moves freely through pores.
•Solute (green) too large to move across.
Animations3. Osmosis3. Osmosis
3. Osmosis
Factors Affecting Rate of Diffusion Factors Affecting Rate of Diffusion
1. Size1. Size small molecules can slip through
phospholipids bilayer easier than large molecules
very large molecules may not be able to diffuse at all
2. Concentration2. Concentration
the greater the concentration gradient (bigger range) the quicker a material diffuses (makes the molecules want to move faster) – think of a crowded room
3. Temperature In general as temperature increases – molecules move
faster which translates into faster diffusion
4. Polarity of molecules4. Polarity of molecules
Water-soluble (polar) molecules will not easily move through the membrane because they are stopped by the middle water-insoluble (nonpolar) layer
5. Surface Area5. Surface Area As a cell’s size increases its volume increases much
quicker than it’s surface area. If you double individual lengths (1 cm to 2 cm) the surface
areas increases 4 times, and the volume increases 8 times.
If cell size is doubled, it would require 8 times more nutrients and have 8 times s much waste. SA only increases by a factor of 4 – not enough surface area through which nutrients and wastes could move. Cell would either starve or be poisoned (waste products)
Cells divide before they come too large to function.
Active TransportActive Transport Involves moving molecules "uphill" against
the concentration gradient, which requires energy. Uses carrier protein molecules as receptors.
One may transport calcium ions another glucose molecules.
Hundreds of these types of protein molecules. Each one changes shape to accommodate a
specific molecule.
(Low High)
2. Active Transport2. Active Transport (cont’d) (cont’d)
Their activity can be stopped from transporting molecules with inhibitors (unfortunately, these are usually poisons) which: either destroy the membrane protein or just plug it up (e.g. for your neurons – tetanus &
botulinum-B secrete a poison that
suppress the Na/K pump)
Three types: active transport animation
http://www.biology4kids.com/files/cell2_activetran.html
1. Protein Pumps1. Protein Pumps
•transport proteins that require energy to do work•Example: Na+/K+ pumps are important in nerve responses.
Sodium Potassium Pumps
Protein changes shape to move molecules: this requires energy!
Sodium-Potassium PumpSodium-Potassium Pump Pumps out 3 sodium atoms for ever 2
potassium atoms taken in against gradient in the cell.
ATP and the Na/K Pump
Animation: How the Sodium Potassium Pump Works
The H+/K+ ATPaseThe H+/K+ ATPase
The parietal cells of your stomach (lining) use this pump to secrete gastric juice.
These cells transport hydrogen ions (H+) from a concentration of about 4 x 10-8 M within the cell to a concentration of about 0.15 M in the gastric juice (giving it a pH close to 2). Recall: pH – power of the H+ ion
Small wonder that parietal cells are stuffed with mitochondria and use huge amounts of energy as they carry out this three-million fold concentration of protons.
The H+/K+ ATPaseThe H+/K+ ATPase
3. Exocytosis3. Exocytosis
Moves large, complex molecules such as proteins out of the cell membrane.
Large molecules, food, or fluid droplets are packaged in membrane-bound sacs called vesicles. Cell changes shape – requires energy Ex: Hormones or wastes released from cell Transport Animations
Endocytosis & Exocytosis animations
2. Endocytosis2. Endocytosis
taking bulky material into a cell
• Uses energy• Cell membrane in-folds
around food particle• “cell eating”• forms food vacuole &
digests food• This is how white blood
cells eat bacteria!
EndocytosisEndocytosis
Endocytosis moves large particles (huge molecules or molecular conglomerates) into a cell.
endo & exocystosis animations
PhagocytosisPhagocytosis
Phagocytosis is another type of endocytosis used for massive transport.Cell membrane extends out forming pseudopods (fingerlike projections) that surround the particle.
Membrane pouch encloses the material & pinches off inside the cell making a vesicle.
Vesicle can fuse with lysosomes(digestive organelles) or release their contents in the cytoplasm
Animation: Phagocytosis HowStuffWorks "Phagocytosis"
Used by ameba to feed & white blood cells to kill bacteria.Known as “killer cells"
Pinocytosis is another type of endocytosis Cell membrane surrounds fluid droplets Fluids taken into membrane-bound vesicle Known as “cell drinking”
•Exocytosis is used to remove large products from the cell such as wastes, mucus, & cell products such as hormones and antibodies.
•Exocytosis is the process used by our memory cells (white blood cells that produce antibodies to fight infection).
•It is also used by our gland cells to secrete hormones when needed.
•Phagocytosisanimationanimation
In SummaryIn Summary
Essential Biochemistry - Membrane Transport
Transport FlowchartTransport FlowchartTransport of Materials
Across a Membrane
Active
Phagocytosis
Pinocytosis
Ion Pum
p
Facilitated
Diffusion
OsmosisSimple
Diffusion
Passive
Endocytosis
Exocytosis
Osmosis and TonicityOsmosis and Tonicity
Tonicity is a relative term Water molecules are so small, and there is
so much of it, that the cell can’t control it’s movement through the cell membrane.
Hypotonic SolutionHypotonic Solution
Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!
Osmosis Osmosis Animations for Animations for
isotonic, hypertonic, isotonic, hypertonic, and hypotonic and hypotonic
solutionssolutions
Hypertonic SolutionHypertonic Solution
Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)
Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!
Osmosis Osmosis Animations for Animations for
isotonic, hypertonic, isotonic, hypertonic, and hypotonic and hypotonic
solutionssolutions
shrinks
Isotonic SolutionIsotonic SolutionIsotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)
Osmosis Osmosis Animations for Animations for
isotonic, hypertonic, isotonic, hypertonic, and hypotonic and hypotonic
solutionssolutions
What type of solution are these cells in?
A CB
Hypertonic Isotonic Hypotonic
Plant and Animal Cells put into various solutions
How Organisms Deal with How Organisms Deal with Osmotic PressureOsmotic Pressure
Paramecium (protist) removing excess water video
•Salt water fish pump salt out of their specialized gills so they do not dehydrate.
•Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.
•Blood brain barrier allows some substances into the brain, but screens out toxins and bacteria
• Allows water, CO2, glucose, AA’s, alcohol, & antihistamines
• HIV and bacterial meningitis can also cross this barrier
How Organisms Deal with How Organisms Deal with Osmotic PressureOsmotic Pressure
Paramecium (protist) removing excess water video
•Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall by the central vacuole is called tugor pressure. (bike tire analogy)
•A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.