august 27-28, 2014. selectively permeable barrier between the cell and the environment
TRANSCRIPT
Selectively permeable barrier between the cell and the environment.
What does ‘selectively permeable’ mean?
Plasma Membrane
Selectively permeable barrier between the cell and the environment.
What does ‘selectively permeable’ mean? Only some materials can cross the membrane
Selective permeability is necessary for the cell to maintain the correct internal environment for physiological functions.
Plasma Membrane
Phospholipids◦ Make up the majority of
the membrane
◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside
Plasma Membrane components
Phospholipids◦ Make up the majority of
the membrane
◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside
Plasma Membrane components
Hydrophilic = ___________Hydrophilic molecules are __________ like water.
Hydrophobic = ____________Hydrophobic molecules are __________ like oil.
Phospholipids◦ Make up the majority of
the membrane
◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside
Plasma Membrane components
Hydrophilic = water lovingHydrophilic molecules are polar like water.
Hydrophobic = water fearingHydrophobic molecules are nonpolar like oil.
Phospholipids
The structure of phospholipids is the key to their function!
Plasma Membrane components
Hydrophilic heads can interact with watery external environment and watery cytoplasm.
Hydrophobic tails reduce the diffusion of water and other charged or polar substances across the membrane.
Cholesterol◦ Makes the cell membrane more rigid and less permeable to water
Proteins◦ Act as enzymes, pores, carriers, and hormone
receptors, and structural elements
Plasma membrane components
Glycoproteins and Glycolipids◦ Glyco = sugar!◦ Influence cell interactions (e.g. identifying cell as
‘self’) and molecule transport
Plasma membrane components
Talk with a partner then share as a class
Scholar on the left answers …◦ What are the 4 membrane components?◦ Which component has most functions? Why?
Scholar on the right answers …◦ Name 4 functions of membrane proteins◦ Which two components are primarily responsible
for reducing fluid loss through the cell? What do those components have in common?
Quick Review: Plasma Membrane Structure
____________ a dissolving agent (water, usually)
____________ substances dissolved in a solution
____________ watery environment outside cells
____________ lower solute concentration
____________ higher solute concentration
____________ equal solute concentration
Cell Transport Vocabulary
Solution: a dissolving agent (water, usually)
Solute: substances dissolved in a solution
Interstitial fluid: watery environment outside cells
Hypotonic: lower solute concentration
Hypertonic: higher solute concentration
Isotonic: equal solute concentration
Cell Transport Vocabulary
Transport of materials across the cell membrane can be characterized as passive or active.
Transport mechanisms
Transport of materials across the cell membrane can be characterized as passive or active.
Passive mechanisms require NO ENERGY from the cell. ALL passive mechanisms transport molecules down their concentration gradient.
Active mechanisms require energy from the cell.
Transport mechanisms
Diffusion is the net movement of molecules down their concentration gradient. Results from the random movement of molecules.
Diffusion animation
Passsive Transport - Diffusion
Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules.
Examples:
Passsive Transport - Diffusion
Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules.
Examples: fats, fat-soluble vitamins, O2, CO2, Cl-
Passsive Transport - Diffusion
Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules.
Examples: fats, fat-soluble vitamins, O2, CO2, Cl-
Osmosis is simple diffusion of water.
Passsive Transport - Diffusion
Facilitated diffusion - diffusion using a protein carrier; used for large polar molecules◦ Example: glucose
Passsive Transport - Diffusion
Filtration occurs when water and solutes are pushed through a membrane by hydrostatic (fluid) pressure.
Water and solutes move down pressure gradient.
Process by which blood is filtered in the kidney.
Passsive Transport - Filtration
Wait 30 sec, then show answer with your fingers
What 2 things do all passive transport mechanisms have in common?1) Membrane proteins are always involved and no
energy is required2) Membrane proteins are always involved and energy is
required3) Molecules move down a gradient and no energy is
required4) Molecules move down a gradient and energy is
required
Quick Review: Passive Transport
Wait 30 sec, then show answer with your fingers
What 2 things do simple and facilitated diffusion have in common?1) Membrane proteins are always involved and no
energy is needed2) Membrane proteins are always involved and energy is
required3) Molecules move down their concentration gradient
and no energy is needed4) Molecules move down their concentration gradient
and energy is required
Quick Review: Passive Transport
How is each molecule transported? Show1) Simple diffusion through lipids2) Simple diffusion through protein pores3) Facilitated diffusion using carrier proteins
a) Waterb) CO2
c) Glucosed) Cl-
Quick Review: Passive Transport
How is each molecule transported? Show1) Simple diffusion through lipids2) Simple diffusion through protein pores3) Facilitated diffusion using carrier proteins
a) Water - 2b) CO2 - 1
c) Glucose - 3d) Cl- - 2
Quick Review: Passive Transport
Use the picture to answer.
In which direction will ions diffuse?1) into the cell2) out of the cell
In which direction will osmosis occur?
1) into the cell2) out of the cell
Quick Review: Passive Transport
Use the picture to answer.
In which direction will ions diffuse?1) into the cell2) out of the cell
In which direction will osmosis occur?
1) into the cell2) out of the cell
Quick Review: Passive Transport
Active transport requires the use of energy (ATP) to transport material across the cell.
Active transport is used for◦ Solutes moving against the concentration gradient - or - ◦ Very large substances
Active Transport
Solute Pumping (aka active transport) Membrane proteins (called solute pumps) use ATP to carry solutes against their concentration gradient.
Examples: amino acids and most ions
Active Transport
Exocytosis - movement of materials out of the cell by vesicle
Examples: hormones, neurotransmitters, mucus, some wastes
Active Transport
Endocytosis – movement of materials into the cell by vesicle◦ Phagocytosis (cell eating) – white blood cells engulf bacteria, dead cells, and foreign debris◦ Pinocytosis (cell drinking) – used to take up droplets of fats and dissolved proteins
Animation
Active Transport
Many diseases are caused by malfunctions in cell membrane transport.
Examples: Cystic Fibrosis: a Cl- channel is missing,
causing Cl- to build up within the cell Familial hypercholesterolemia – cholesterol
receptors on cell membrane missing, so cholestrol builds up in the blood
Burned tissue ‘weeps’ fluids, proteins, ions, etc.
Homeostatic Imbalance
Draw a detailed picture of the cell membrane.
Include, and label: The structural components
Phospholipids, cholesterol, membrane proteins, glycoproteins, glycolipids
The transport mechanisms Simple diffusion, osmosis, facilitated diffusion, solute
pumping, exocytosis, pinocytosis, phagocytosis
When done, compare with a neighbor, but don’t add to it.
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