Ch. 5 Homeostasis & Cell Transport

Ch. 5 Homeostasis & Cell Transport

5.1 Homeostasis & Permeability

Homeostasis ability of cell to maintain balance needed for life To maintain balance: cells must transport needed materials into cells & waste materials out of cells Movement in or out of a cell depends on permeability

Permeability the ability of a molecule to move across a membrane If molecule can move across, membrane is permeable to molecule. If molecule cannot move across, membrane is impermeable to molecule.

most membranes are Selectively (semi) Permeable: some molecules move across, others can't Membrane is Choosy

Two Main Types of Cell Transport 1. Passive Transport 2. Active Transport

Passive Transport Movement of substances across a membrane without using energy Molecules move down the Concentration Gradient Concentration gradient - difference in concentration of molecules across a membrane

Molecules move HIGH TO LOW! 3 forms of Passive Transport: a. Simple Diffusion b. Osmosis c. Facilitated Diffusion

a. Simple Diffusion: Movement of SOLUTE across a membrane! No energy needed! HIGH TO LOW!

Which way will the purple molecules move? To the right!

Molecules move back and forth until balance is reached. Balance = Equilibrium When equilibrium is reached: molecules still move but concentration does not change. ex: 2 molecules in = 2 molecules out

5.2 Osmosis

b. Osmosis Diffusion of water across a membrane Passive: no energy needed Water is the solvent in cells BUT movement of water depends on concentration of solute

To determine which way water will move, 1 st describe the solution: 3 types of solutions: a. Hypertonic: MORE solute outside cell b. Hypotonic: LESS solute outside cell c. Isotonic: solute is EQUAL inside & outside

Hypertonic Solutions & Osmosis cell Which way will the water move? Water will move OUT of the cell Cell will shrivel Sugar molecule

Hypotonic Solutions & Osmosis cell Which way will the water move? Water will move INTO cell Cell will swell Sugar molecule

Isotonic Solutions & Osmosis cell Which way will the water move? Water will move IN & OUT of cell Cell will stay the same Sugar molecule

Osmosis & Red Blood Cells

What Makes Water Move? Osmotic Pressure: Pressure created by water molecules If water concentration is, osmotic pressure is If water concentration is, osmotic pressure is Water moves from an area of HIGH osmotic pressure to an area of LOW osmotic pressure HIGH TO LOW!

Osmosis in Plants Osmosis affects Turgor Pressure - pressure of water that presses cell membrane against the cell wall if soil is hypertonic (dry): water moves out of cell, turgor pressure, membrane pulls away from wall, plant wilts if soil is hypotonic (wet): water moves into cell, turgor pressure, membrane pushes against from wall, plant is crisp

c. Facilitated Diffusion passive transport molecules insoluble in lipids or too large molecules need help to cross 2 types: 1. Carrier proteins 2. Ion channels

Carrier Proteins Proteins in membrane Move substances from high to low Proteins are specific: transport only 1molecule Glucose moves this way

Ion Channels Na +, Cl -, ions are important to cell function Insoluble in lipid bilayer, can t cross alone Proteins form channels Passive transport: high to low Some channels always open, others have gates that open in response to stimuli

5.3 Active Transport

Active Transport Move substances up(or against) concentration gradient: from low to high concentration Requires input of energy 2 types: cell membrane pumps, and movement of vesicles

Membrane Pumps Protein pumps that move substances from low to high concentration Require energy of ATP ex: sodium-potassium pump: moves Na+ and K+ ions low to high important to nerve function

Movement in Vesicles move molecules too large to diffuse move large quantities at one time ex: nutrients & macromolecules 2 types: Endocytosis Exocytosis

Endocytosis cells ingest large materials INTO cell materials fill pouch in membrane pouch forms vesicle lysosomes attach & spill in enzymes Pinocytosis: endocytosis of liquids Phagocytosis: endocytosis of solids

Phagocyte: cell that ingests solid material ex: white blood cells ingest bacteria

Exocytosis Material moved OUT of cell Vesicle carries materials to membrane Fuses w/ membrane & opens to outside Proteins & wastes removed this way

Endo Exo