Homeostasis Transport Section 1 Diffusion Osmosis Homeostasis s

Homeostasis & Transport

Section 1: Diffusion & Osmosis

Homeostasis s Homeostasis: the biological balance between a cell or an organism and its environment s Cells maintain homeostasis by controlling and regulating what gets into and out of the cell.

Passive Transport s Passive Transport: the movement of any substance across a cell membrane without the use of cell energy s s Diffusion Osmosis Facilitated Diffusion Gated Channel

Diffusion s Diffusion: the process by which molecules move from an area of greater concentration to an area of lower concentration

Diffusion

Brownian Motion s Brownian Motion: molecules are in a constant state of random motion

Brownian Motion

Concentration Gradient s Concentration Gradient: the difference in concentration of a substance across a space

Review of Cell Membrane Structure

Diffusion Across Membranes s Not all molecules can diffuse through all membranes. s The ability of a molecule to pass through a membrane depends on the size and type of molecule and the molecular structure of the membrane. Small nonpolar molecules can diffuse through the cell membrane

Osmosis s Osmosis: the diffusion of water molecules through a selectively permeable membrane from an area of high water concentration to an area of lower water concentration

Osmosis

Three Types of Solutions 90% H 2 O 10% solute 85% H 2 O 15% solute 95% H 2 O 5% solute 90% H 2 O 10% solute Isotonic (no net movement of water) Hypotonic Hypertonic

Three Types of Solutions Plant Cells

Three Types of Solutions Animal Cells

Three Types of Solutions Hypotonic solution H 2 O Isotonic solution Hypertonic solution H 2 O (a) Animal cell Cytolysis H 2 O Normal H 2 O Shriveled H 2 O (b) Plant cell Turgid (normal) Flaccid Plasmolysis

Three Types of Solutions

Contractile Vacuoles s Contractile Vacuole: an organelle in microorganisms that excretes water s collect excess water → contract → squeeze out water

Study the diagram below. It represents a container that is divided by a semipermeable membrane. A different solution in its initial state is shown on each side of the membrane. 1. 2. 3. 4. Describe which molecule(s) will move through the membrane and which molecule(s) will not. Describe the relative rates at which the molecule(s) will move across the membrane. Describe in which direction the molecule(s) will move. Describe how long the molecule(s) will continue to move.

Review of Cell Membrane Structure

Review of Cell Membrane Structure

Facilitated Diffusion s Facilitated Diffusion: a process in which substances move down their concentration gradient across the cell membrane with the assistance of a membrane protein s Examples: glucose, fructose, water & ions

Two Types of Membrane Proteins: Channels & Carrier Proteins

Facilitated Diffusion

Aquaporins = Water Channels

Gated Channel s Gated Channel: a protein-lined gated passage making cell membranes permeable to certain large molecules as needed s Example: neuromuscular function

Gated Channel Protein key made by nucleus

Review of Passive Transport

Review of Passive Transport

Section 2: Active Transport

Active Transport s Active Transport: the movement of any substance across a cell membrane with the use of energy from ATP s Sodium-Potassium Pump s Endocytosis s Exocytosis

Sodium-Potassium Pump s Sodium. Potassium Pump: an active transport mechanism that moves ions in order to achieve polarization

Proton Pump s Proton Pump: an active transport mechanism that consumes ATP (energy) to force Hydrogen ions against the concentration gradient

Proton Pump

Proton Pump & Cotransport

Endocytosis s Endocytosis: the process by which a cell engulfs and surrounds large substances

Phagocytosis

Pinocytosis

Receptor. Mediated Endocytosis

Exocytosis s Exocytosis: the process by which wastes are packaged in vesicles and leave the cell

Exocytosis

Passive vs. Active Transport