The Cell Learning Objectives
The Cell: Driving Questions • How do cells live up to the name, “the basic unit of structure and function”? • How do evolution and surface area : volume relationships drive cell structure and function? • How do the various parts of a cell work together? • How does molecular traffic move through cell membranes? • What are the basic components of cell-to-cell communication? • Why do cells divide, and how is the cell cycle regulated?
A word from the top… • This unit should be be straight forward • It should only take 2.5 weeks, even with lab work. • Make the lab work central to your cell unit • Diffusion Osmosis • ‘Scope Lab looking at different types of cells • AP Lab 3A (mitosis simulation and ID of phases of mitosis) • We should continue to develop students’ microscopy skills
Chapter 6, Students need to know… • The difference between prokaryotic and eukaryotic cells. • The structure and function of eukaryotic organelles • The way organelles work together to facilitate cell function, with particular emphasis on the endomembrane system and protein synthesis and secretion • How prokaryotes perform cellular functions without organelles • the essential concept of surface area to volume relationships (SA:Vol), and how that relationship drives the evolution of cell shape and the evolution of membrane-bound organelles. Surface area to volume also governs transport across membranes.
What is a cell? • Helpful to mention what a cell is not… • Prokaryotic • Eukaryotic
What is a cell? Can cells survive on their own?
Why Cells? • Division of Labor • Multiple metabolic functions in one cell • Multiple Functions within an organism • Repair and reproduction • Increased surface area to volume ratio!
INTERNAL MEMBRANES (Endo-Membrane System) Partition cell into compartments Internal Membranes have unique Lipid and Protein compositions, therefore… Participate in metabolic activities Provide Localized Environment for specific metabolic processes Sequester, or isolate, certain reactions so they don’t interfere with other metabolic processes How does a eukaryotic cell compensate for lower surface area to volume ratio?
Chapter 6 cont, Students need to know… • The structure and function of the following: • the various components of the cytoskeleton, • plant cell walls, • the animal Extra Cellular Matrix (ECM) • intercellular junctions (plasmodesmata, tight junctions and gap junctions). • Why: the cytoskeleton and the intercellular space is the place where cells communicate.
Cytoskeleton = Mechanical Support and Cell Motility Continuing with the theme of what a cell is not. Check out Table 7.1
Microtubules • largest • made of tubulin • Easy to make, easy to break • Essential for moving things around the cell
Microtubule Monorails! • Vessicles don’t move by magic… • Chromosomes aren’t “pulled” by microtubles, they walk during anaphase
Microtubules = Cilia and Flagella • This is a great place to discuss Unit and Diversity
9 + 2 Ultrastructure • The parts matter… • Pairs of microtubles connected by Dynein, • Everyone pulls one way…and the whole thing “falls over” tension and release”
“9+2” + Cross linked Proteins = • Beating of cillia and • Undulation of flagella
Microfilaments: Actin Filaments • The smallest components of the cytoskeleton • Provide tension for pulling…can’t mention actin with-out myosin
Microfilaments = cell motility • Sliding filaments of skeletal muscles* • The reason for cytoplasmic streaming
Microfilaments = cell motility • Microfilaments provide the possibilitity of pseudopodia • Microfilaments are the reason for cytokinesis/cleavage
Intermediate Filaments • The name says it all… • The toughest components of the cytoskeleton
Extra Cellular Matrix • The integrins • The Fibronectins and Collagen • The Interstitial fluid
Extra Cellular Matrix: Plants • 1º Cell Wall • 2º Cell Wall • Middle Lamella • Plasmodesmata
Cell-To-Cell Junctions • Tight Junctions • Desmosomes • Gap Junctions • Plasmodesmata
Chapter 7, Students need to know… • The fluid mosaic model of cell membranes and the constituent parts. • Cell membranes are ambiphatic and semi-permeable • Membrane proteins give cell membranes their specific functions • Membrane proteins have varied, yet crucial, roles in cell function
Cell Membranes • Irving Langmuir (1917) • Davidson and Danelli (1935) • Singer and Nicholson (1972) = • Fluid Mosaic Model of Cell Membranes
Cell Membranes are Selectively Permeable • Why? • What’s Moving?
Fluid Mosaic:The Lipids Why the change in lipid components? What organelle is responsible for these changes?
Fluid Mosaic Model of Cell Membranes SO WHAT? The cell is able to take up many varieties of small Molecules and ions and exclude others. The fluid mosaic model helps explain how membranes regulate the cell’s molecular traffic.
Chapter 7, Students need to know… • The concept of diffusion • The concept of tonicity, and they need to be able to differentiate between hypotonic, isotonic and hypertonic environments. They need to do this for the cytoplasm as well as the extracellular space. • How to predict if a molecule will move across the cell membrane and which direction it will move across the cell membrane • The difference between diffusion, osmosis, facilitated diffusion, and active transport • Two or three examples of active transport • Bulk transport including endo- and exocytosis
What is osmosis? What the heck is “water potential”?
What is Tonicity? What is water balance?
How do molecules move across a membrane? • Diffusion: Net movement of molecules along a concentration gradient from an area of [hi] to [lo] • Osmosis: The net movement of watermolecules along a [gradient] across a (semi-permeable) membrane
Facilitated Diffusion • This is still passive transport…with a twist. • Specific solutes move through specific integrins • Think of integrins as “phsyical catalysts”
Active Transport • What? • The cell uses energy (ATP) to pump a molecule across a membrane, against its concentration gradient. • So What? • Examples: Speeds the tran- sport of a solute (by providing an efficient passage), does not change the direction of diffusion
Na/K Pump = Membrane Potential • How it works: • Membrane Potential is… A chemo-electric gradient
Proton Pumps: A more “primitive” Active Transport • What it is: • It also generates a… • Electrochemical gradient: