Post on 18-Dec-2015
Section ObjectivesExplain how the processes of diffusion,
passive transport, and active transport occur and why they are important to cells.
Predict the effect of a hypotonic, hypertonic, or isotonic solution on a cell.
Diffusion• Move from HIGH to LOW concentration
– passive transport– no energy needed
diffusion osmosis
diffusion of water
Simple Diffusion • Move from HIGH to LOW
inside cell
outside cell
Which way will fat move?
fat
fat
fat
fat
fat
fat fat
fatfat
fat
fat
fat
fat
fat
LOW
HIGH
Movement through the channel
• Why do molecules move through membrane if you give them a channel?
?
?
HIGH
LOW
Facilitated Diffusion• Move from HIGH to LOW through a channel
inside cell
outside cell
sugar
sugar
sugar
sugar
sugarsugar
sugarsugar
sugarsugar
sugar
Which way will sugar move?
sugar
sugar
LOW
HIGH
Diffusion• Move from HIGH to LOW concentration
– directly through membrane• simple diffusion• no energy needed
– help through a protein channel• facilitated diffusion (with help)• no energy needed HIGH
LOW
Simple vs. facilitated diffusion
inside cell
outside cell
lipidinside cell
outside cell
H2O
simple diffusion facilitated diffusion
H2O
protein channel
Facilitated Diffusion
Cellular Structure and Function
Movement of materials across the plasma membrane using protein channels.
Osmosis
Cellular Structure and Function
Diffusion of water across a selectively permeable membrane
Aquaporins are water channel proteins that allow water to pass through cell membrane through facilitated diffusion.
Osmosis is the passive transport of water
• In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration – Hypertonic: [hyper=above, over]
• Solutions in which more solute present (concentrated solution)
– Hypotonic: [hypo= below, under]• Solutions in which less solute is present (dilute
solution)
– Isotonic: [ iso= equal]• Solutions have equal concentrations of substances
Blood CellPlant Cell
Isotonic Solution
Cellular Structure and Function
Water and dissolved substances diffuse into and out of the cell at the same rate.
11,397x
Blood Cell
Hypotonic Solution
Cellular Structure and Function
Solute concentration is higher inside the cell. Water diffuses into the cell.
Plant Cell
13,000x
Plant Cell
Hypertonic Solution
Cellular Structure and Function
Solute concentration is higher outside the cell. Water diffuses out of the cell.
Blood Cell
13,000x
Water balance between cells and their surroundings is crucial to organisms
• Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution– The control of water
balance(osmoregulation) is essential for organisms
ISOTONIC SOLUTION
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
ANIMALCELL
PLANTCELL
Active transport
• Requires the cell to spend energy [ATP][ATP]
• Transport proteins can move solutes across a membrane against [up] a concentration gradient
Active Transport
Cellular Structure and Function
Movement of particles across the cell membrane using energy
Active Transport Using Carrier Proteins
Active Transport
• active transport :Movement of materials through a membrane against a concentration gradient and requires energy from the cell. ATP
Concentration gradient
Plasma membrane
Carrier proteins
Cellular energy
Cellular energy
Active transport• Cells may need molecules to move against
concentration “hill”– need to pump “uphill”
• from LOW to HIGH using energy
– protein pump– requires energy
• ATPATP
Exocytosis and endocytosis transport large molecules
1. Exocytosis [ exo = outside]movement of large materials OUT of the cell~a vesicle may fuse with the membrane and expel its contents
CYTOPLASM
FLUID OUTSIDE CELL