Active and Passive Transport

Vocab: Hypertonic: More solutes than the other solution Hypotonic: Less solutes than the other solution Isotonic: Equal solutes as another solution

Describing a solution Hypotonic: when a solution is less concentrated than another solution Example: if around a cell is hypotonic, then water will move into the cell. Can cause a cell to get so large it may burst (cytolysis)

Hypertonic: When a solution is more concentrated than another solution If around a cell is hypertonic, water will move out of the cell Can cause the cell to get very small (in plants will see plasmolysis: wilting)

Isotonic: when two solutions have the same concentration (are at equilibrium) Causes water to move in and out equally The cell maintains its shape

Hypotonic solution Isotonic solution Hypertonic solution (a) (b) H2O Lysed Normal Shriveled Turgid (normal) Flaccid Plasmolyzed

Passive Transport

S-B-7-3_Passive Transport PPT Process that moves materials across the plasma membrane Does not require energy from the cell Materials move with the concentration gradient: high concentration low concentration 3 Kinds: Diffusion, Osmosis, and Facilitated Diffusion S-B-7-3_Passive Transport PPT

S-B-7-3_Passive Transport PPT Diffusion The movement of molecules across a membrane, with a net movement from high to low concentration Molecules tend to “spread out” to reach equilibrium. Source: http://upload.wikimedia.org/wikipedia/commons/1/15/Diffusion.en.jpg S-B-7-3_Passive Transport PPT

S-B-7-3_Passive Transport PPT Osmosis Diffusion of water across a selectively permeable membrane. Does not require energy from the cell. S-B-7-3_Passive Transport PPT

S-B-7-3_Passive Transport PPT The rule for osmosis: If the area outside the cell has more salt, then water will be sucked out of the cell. S-B-7-3_Passive Transport PPT

Facilitated Diffusion Carrier proteins help small molecules move across the plasma membrane. Does not require energy from the cell. Source: http://www.williamsclass.com/SeventhScienceWork/ImagesCellBricks/facilitatedDiffusion.jpg S-B-7-3_Passive Transport PPT

Passive Transport: Review Diffusion, Osmosis, Facilitated Diffusion Molecules move with the concentration gradient Does not require energy from the cell S-B-7-3_Passive Transport PPT

What if….. Environment around a cell is hypotonic. What direction will the water move? Salt?

What if….. The environment around a cell is hypertonic. What direction will the water move? Salt?

2. Active Transport Requires energy Goes against the concentration gradient (from lower concentration to higher concentration)

Active Transport: Molecules move across the cell membrane from ____low________ to ___high______ concentration. It uses __energy_______ or ATP. Carbon Dioxide molecules

__Molecular ____ ___transport____ (pumps)- proteins use ATP to _transport_____ molecules across the cell membrane from __low____ to _high____ concentration. This allows _small___ _molecules_ and _ions__ (such as K+_, __Ca__, _Na___) to be transported across the membrane.

_Endocytosis__ - the _cell___ _membrane_ surrounds substances and moves them _INTO_ the cell.

Ex: White Blood Cells, which are part of the immune system, surround and engulf bacteria by endocytosis.

__Phagocytosis__- surrounds a _food__ _molecule_. Cell “__eating___” _Pinocytosis__ - surrounds __liquid_. Cell “__drinking___”

_Exocytosis__ - a _vacuole__ joins with the cell membrane and _releases_ its contents.

What leaves through exocytosis? Cell products: _lipids_ and _proteins__ Cell _wastes__ Excess _water_: through _contractile__ _vacuole_

Figure 7.16 The sodium-potassium pump: a specific case of active transport Cytoplasmic Na+ binds to the sodium-potassium pump. 1 Na+ binding stimulates phosphorylation by ATP. 2 K+ is released and Na+ sites are receptive again; The cycle repeats. 3 Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside. 4 Extracellular K+ binds to the protein, triggering release of the Phosphate group. 6 Loss of the phosphate restores the protein’s original conformation. 5 EXTRACELLULAR FLUID [Na+] high [K+] low CYTOPLASM [Na+] low [K+] high Na+ P ATP ADP P i K+

Sodium Potassium Pump Cells usually have more sodium ions outside and more potassium ions inside Pump increases number of ions where concentration is already high

When substances are too large to pass through the cell membrane, use endocytosis or exocytosis Membrane folds around substances and release into cell or out of cell

Figure 7.20 Exploring Endocytosis in Animal Cells EXTRACELLULAR FLUID Pseudopodium CYTOPLASM “Food” or other particle Food vacuole 1 µm of amoeba Bacterium Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM). PHAGOCYTOSIS PINOCYTOSIS Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM). 0.5 µm Plasma membrane Vesicle

Endocytosis Material moved into cell Forms vesicle Pinocytosis: Liquids Phagocytosis: Solids

Exocytosis Material released to outside of cell