Cell Boundaries Chapter 7.3 Strand: B2.5h
Review: Cell Membrane What is the role of the cell membrane within a cell? The cell membrane regulates what enters and leaves the cell and also provides protection and support. Do plants, animals, or both have cell membranes? BOTH! Plants have a cell wall that animal cells do not have.
7.2 Homeostasis: a balanced state maintained by all living things Ex. Blood, organs, systems All systems must work together to balance the body
How does the cell do this?
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane Cell Membrane: Thin, flexible boundary between the cell and its environment Allows nutrients into the cell Allows waste to leave the cell
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane Selective Permeability The membrane controls the movement of substances into and out of the cell.
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane The cell membrane is composed of the phospholipid bilayer.
Contains a: Hydrophilic head: water loving (polar) Hydrophobic tail: water avoiding (nonpolar)
Only lipid (fat) soluble substances can pass through the membrane Water is the exception
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane The phospholipid bilayer allows other molecules to float in the membrane. Other Components Proteins Cholesterol Carbohydrates
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane Proteins Transmit signals inside the cell Act as a support structure Provide pathways for substances to enter and leave
Protein Transport Channel and Carrier: Both aid in the movement of molecules in and out of the cell
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane Lipids Cholesterol: Prevents fatty acid tails from sticking together
Chapter 7 Cellular Structure and Function 7.2 The Plasma Membrane Carbohydrates Attached to the outside of the membrane Recognize chemical signals Allow other cells to identify it
Review: Cell Wall What is the function of the cell wall? The main function of the cell wall is to provide support and protection for the cell. Plant cell walls are mostly made of cellulose- a tough carbohydrate fiber. Cellulose is the main component in wood and paper- so the paper in your hand is actually made of cell walls!
Review: Concentration Solution- a mixture of two or more substances. Solute- substances dissolved in a solution. Concentration- the mass of solute in a given volume of solution, or mass/volume. Equilibrium- the concentration of the solute is the same throughout a system.
Which has a higher concentration? A A B
Movement Through Cell Boundaries 1. Diffusion 2. Facilitated Diffusion 3. Osmosis 4. Active Transport
Diffusion! In a solution particles are moving constantly they collide with one another and spread out randomly. Particles tend to move from an area of HIGH concentration to an area of LOW concentration- this process is called diffusion!
Diffusion (cont.) Diffusion depends upon random particle movements, and therefore substances across membranes without requiring the cell to use energy. High to Low Equilibrium
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport Diffusion is controlled by Temperature Pressure Concentration Dynamic Equilibrium Reached when diffusion of material into the cell equals diffusion of material out of the cell Molecules continue to move, but the overall concentration remains the same.
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport Diffusion in a Cell
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport 2. Facilitated Diffusion Movement of materials across the membrane using protein channels or protein carriers.
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport Channel Proteins Carrier Proteins
Osmosis! The diffusion of water through a selectively permeable membrane. Permeable- substances are able to diffuse across the membrane. Impermeable- substances cannot pass across the membrane.
Osmosis in Cells Solution Animal Cell Plant Cell Isotonic: Water in The concentration of solutes is the same inside and outside the cell. Hypertonic: Solution has a higher solute concentration than the cell. Hypotonic: Solutions has a lower solute concentration than the cell. Water in Water in Water out Water out Water in Water out Water out
Active Transport The movement of materials against the concentration gradient across the cell membrane. Requires energy. The active transport of small molecules or ions across a cell membrane is generally carried out by transport proteins, or pumps that are found in the membrane itself.
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport Types of Active Transport Pumps: Na + /K + ATPase pump Moves three Na + ions out of the cell and two K + ions into the cell
Chapter 7 Cellular Structure and Function 7.4 Cellular Transport: Active Endocytosis: Process by which the cell surrounds and takes particles into the cell Phagocytosis: endocytosis with very large molecules
Active Transport Exocytosis: Secretion of material out of the plasma membrane