Unit 3: Movement in and out of Cells

The History of the Cell Theory (p 172) Compound Light microscopes Invented by Anton van Leeuwenhoek 1500 x Electron microscopes Scanning electron microscope (SEM, 扫描电镜 ) Surface of 3D objects Transmission electron microscope (TEM, 透射电镜 ) Inside a cell Scanning Tunneling microscope (STM) Viewing atoms

The History of the Cell Theory Robert Hooke- first to use the word “cells” The Cell Theory: 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of structure and organization of organisms. 3. All cells come from preexisting cells.

Two Basic Cell Types Prokaryotes: Cells that do not contain any membrane-bound organelles Cells that do not contain any membrane-bound organelles - no nucleus, mitochondria, goli, etc.. Most unicellular (one cell) organisms; bacteria

Two Basic Cell Types Eukaryotes: Cells that do contain membrane- bound organelles (nucleus) Cells that do contain membrane- bound organelles (nucleus) Most multicellular (many cells) organisms; plants, animals, etc. Some unicellular organism too; algae

Prokaryote Vs. Eukaryote ProkaryoteEukaryote No membrane-bound organelles Membrane-bound organelles No nucleusNucleus Small ( mm)Large ( mm) Small RibosomesLarge Ribosomes Small, normally circular DNA Large, chromosome DNA

Review Organelles Cell labeling practice sheet

Cellular Transport Cells must move things inside and outside to maintain homeostasis What might they need to take in: –Food molecules –Signals –Ions What might they need to release: –Waste material –Proteins –Signals

Cellular Transport 2 Types of transport: 1)Passive Movement –Does not require the cell to use energy to move 2)Active Movement –Does require the cell to use energy –Cell uses energy units (ATP)

Passive Movement: Diffusion Diffusion  movement of molecules from areas High concentrations to areas of Low concentrations; down a concentration gradient Food coloring in water, sugar in water, fart fills a room, etc… Where does the energy come from for this movement? –Kinetic energy in molecules (random movement)

Passive Movement: Diffusion What is the barrier that surrounds all cells? –Plasma membrane Why can the plasma membrane let in some material and not others? –It is partially (selectively) permeable What materials do you think can diffuse into and out of a cell membrane? –O 2, CO 2, Water, etc…

Diffusion Factors What factors should effect diffusion rate? 1) Distance traveled  membrane is thin; cells are tiny 2) Strength on concentration gradient 3) Surface area of membrane  folding of membranes increase surface area 4) Temperature  higher temp= faster random motion 5) Size of molecule  smaller molecules move faster

Passive Movement: Facilitated Diffusion Facilitated diffusion  diffusion through a protein channel or carrier protein that is specific for 1 type of substance (Na+, Cl -, glucose, etc…) Still follow concentration gradient Can become saturated  meaning the movement is at its maximum rate and can not go any faster

Passive Movement: Osmosis The diffusion of water across a selectively permeable membrane （选择 is called osmosis H 2 O is small enough to fit between phospholipids but moves very slow, why? –Hydrophobic center of membrane pushes it back Aquaporins  transport channels just for H 2 O

Solutions: Solutes and Solvents Solute  the material that dissolves (disappears into) the solvent –Salt in salt water Solvent  the material that breaks apart and dissolves the solute –Water in salt water Soluble  a solute that CAN dissolve in a solvent –“like dissolves like” –Sugar dissolves in water –Fat CANNOT dissolve in water

Osmotic Pressure: Movement of water can increase and decrease pressure inside the cell Hypotonic Solution  – concentration of solute is low (high H 2 O) on the outside and high (low H 2 O) on the inside of the cell –Water moves into the cell causes it to swell (best for plant cells) –High Water Potential (water leaves solution) –Turgid pressure  keeps plants upright

Osmotic Pressure Hypertonic Solution  –concentration is high (low H 2 O) on the outside and low (high H 2 O) on the inside –Low Water Potential (water enters solution) –Water rushes out of the cell causing it to shrink –Plasmolysis  shrinking inside plant cells

Osmotic Pressure Isotonic solution  –concentration inside and outside the cell are equal (equilibrium) –Movement of water in and out of the cell is at equal rates; best for animal cells

Active Movement Energy is required to move molecules AGAINST their concentration gradients ATP must be used to make carrier proteins (pumps) move molecules to the other side Cell uses active transport to create concentration gradients to be used later by passive transport; nervous system

Active Movement: Large Particles Endocytosis  –Cell folds around large particle and pulls it in; plasma membrane makes vacuole Exocytosis  –Vacuole fuses with plasma membrane and release large particles

Know The Difference!

Homework Read p Questions on p. 27, 29, 31, 33, and 34 Quizlet Unit 3 Vocab Vocab books for Lab reports on egg and plant osmosis