functions: – structural support & protection – helps maintain homeostasis – selective...
TRANSCRIPT
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The Cell Membrane & Transport
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The Cell Membrane• Functions:– Structural support & protection– Helps maintain HOMEOSTASIS– Selective barrier –SEMIPERMEABLE
• Water, food, oxygen, waste and nutrients are transported through the cell membrane.
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Structure• Lipid Bilayer = Double
layer of phospholipids• Each Phospholipid has:– 2 non-polar tails:
Hydrophobic (Repels water, Water FEARING)
– 1 polar head: Hydrophilic (Attracted to water, Water LOVING)
• Proteins, carbohydrates, and cholesterol are also in the membrane
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Homeostasis• The maintenance of stable internal conditions
within the cell or organism. • The body’s ability to maintain equilibrium
BALANCE
• Conditions within and around organisms are constantly changing (temperature, water, oxygen), so our cells need a way to adjust to the changing conditions.
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Semipermeable
• Some substances can pass across it and others can not• Also called “Selectively Permeable” • Large molecules such as proteins and sugars don’t pass
freely and must be transported into the cell
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Passive Transport
Allows some particles to move in or out of cell without the use of energy.
•Using Diffusion
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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.htmlDiffusion-
– particles spread from high concentration to low concentration until equilibrium is reached
– movement of Solutes (sugar, salt, minerals) – No energy required
Concentration Gradient- difference in concentration between two areas across
from each other.Molecules will move with the gradient from a high concentration to a lower
concentration .“Rolling down a hill doesn’t require
energy”
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Solutions
• Solute is the material that is being dissolved (sugar)
• Solvent is doing the dissolving (water)
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Types of Diffusion
• Simple—unassisted diffusion of small particles or lipid-soluble molecules
• Osmosis—unassisted diffusion of water
• Facilitated diffusion—diffusion with the help of carrier proteins
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• Osmosis:– diffusion of water from an area of high to low water
concentration – Occurs continuously (all the time) in the cell– No energy required
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•HYPERTONIC solution: 1. Solute concentration outside the cell is higher (less water)2. Water diffuses out of the cell 3. Cell will shrink
Plant cell-cell membrane pulls away from the cell wall (wilts)
•HYPOTONIC solution:1. Solute concentration greater inside the cell (less water)2. Water moves into the cell3. Cell will swell & burst (Lysis)
Plant cell-pressure on cell wall increases- (Turgor)
•ISOTONIC solution: 1.Concentration of solutes is the same
inside & outside the cell
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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html
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• Facilitated Diffusion – transport proteins embedded in cell membrane
“carries” the substance across the membrane.– Substances like glucose, amino acids, and ions use
these – No energy required
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html
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Cell in Isotonic Solution
CELL
10% NaCL90% H2O
10% NaCL
90% H2O
What is the direction of water movement?The cell is at __________.
ENVIRONMENT
NO NET MOVEMENT
Equilibrium
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Cell in Hypotonic Solution
CELL
10% NaCL90% H2O
20% NaCL
80% H2O
(More H20 outside of cell than inside)
What is the direction of water movement?
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Cell in Hypertonic Solution
CELL
15% NaCl85% H2O
5% NaCl95% H2O
(More H20 inside than outside)
What is the direction of water movement?
ENVIRONMENT
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Active Transport• Movement of substances from a lower
concentration to a higher concentration • Energy is needed – ATP (adenosine triphosphate) is the source of the energy.
• Transport goes AGAINST concentration gradient (going up a hill requires energy)
• Carrier Proteins (Transport Proteins)– Endocytosis– Exocytosis
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• Carrier Proteins (Transport Proteins)– Use ATP to pump molecules into or out of the cell– Low concentration to high concentration
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• Endocytosis – Cell membrane folds inward surrounding the material
to transport it INTO the cell– Once inside the cell it’s transported to a lysosome
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Two Types of Endocytosis
Phagocytosis • “Cell Eating”• Engulfs large materials like
bacteria
Pinocytosis• “Cell Drinking”• Engulfs extracellular fluid,
including sugar and proteins
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• Exocytosis – Materials, like waste, are surrounded by a vesicle and
transported to the cell membrane– Vesicle fuses with the cell membrane and releases its
contents OUTSIDE the cell
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