Cellular Transport Processes The Plasma Membrane Solutions and

Cellular Transport Processes The Plasma Membrane, Solutions, and Movement of Materials 1

Homeostasis § Homeostasis is the maintaining the same internal state when the external is changing. • Example – Sweating maintains proper body temperature. 2

Homeostasis & the Cell Membrane § The cell membrane maintains cell homeostasis by being semipermeable. § These are membranes that allow some substances to pass through, but not 3

Homeostasis & Cell Membrane § Why? § Cells to get rid of wastes while keeping other molecules in. • Endocytosis – take in or ingest nutrients • Exocytosis – to release or remove waste § Likewise, they must let things in (like nutrients) while keeping others out (like toxins). 4

Endocytosis § Receptor Mediated Endocytosis 5

Endocytosis § Pinocytosis – “cell drinking” 6

Endocytosis § Phagocytosis – “cell eating” 7

Structure of the Cell Membrane § The cell membrane is a phospholipid bi-layer • Phospho = phosphate heads Ø Hydrophilic – “water loving” • Lipid = fatty acid tail Ø Hydrophobic – “water scared” § Bi = two 8

Structure of the Cell Membrane § The cell membrane is fluid, not rigid 9

Membrane Proteins § Each layer is made up of a sheet of lipid (fat) molecules with protein molecules embedded in the lipid bi-layers. • Carrier Proteins allow substances that are too large to fit through the bi-layer into the cell • Example – Like raisins in a slice of raisin 10 bread.

11

Diffusion § Movement of particles/ “Stuff” from more concentrated to an area of lesser concentration. § Particles tend to distribute themselves evenly within a solution § Occurs until equilibrium is reached 12

Diffusion § An example of diffusion • Spraying perfume in an area. It is very strong in that area at first, and then it spreads out through the room and is not as strong. 13

Types of Diffusion § Passive Transport • Simple vs. Facilitated Diffusion • No energy • May or may not need a protein 14

Types of Diffusion § Active Transport • Requires energy - ATP • Requires a membrane protein 15

Osmosis § The diffusion of water molecules. § Water molecules moves from an area of high concentration to an area of low concentration. 16

Solutions § There are 3 types of solutions: 1. Hypotonic (“hypo” = below/low) 2. Hypertonic (“hyper” = excessive) 3. Isotonic (“iso” = 17

Hypotonic solutions § A solution whose solute concentration is lower than the solute concentration inside a cell • Example: Distilled water • High concentration of water = outside • Low concentration of water = inside So the water will flow from outside inside cell 18

Hypertonic solutions § Are solution whose solute concentration is higher than the solute concentration inside the cell. • Example: Salt Water…the ocean! • High concentration of water = inside • Low concentration of water = outside So the water will flow from inside outside Cell will shrivel. 19

20

Isotonic solutions § An isotonic solution is a solution whose solute concentration outside the cell is equal to the solute concentration inside the cell. • Cells are in equilibrium • Example: Our blood! 21