Homeostasis the Plasma Membrane Structure of the Plasma
Homeostasis & the Plasma Membrane
Structure of the Plasma Membrane v 2 layers of lipids with proteins embedded within each layer v. The lipids are called “phospholipids” v. They have a polar head and a non-polar tail v. HEAD v Is a phosphate group which is soluble in water (hydrophilic) v. TAIL v. Is made of 2 fatty acid chains that are not soluble in water (hydrophobic)
Structure of the Plasma Membrane
Structure of the Plasma Membrane
Maintaining a Balance v. Living cells maintain a balance by controlling what goes into and out of the cell v. The plasma membrane is a selectively permeable membrane – it has the ability to allow some materials to pass through while keeping others out v. This also allows some cells to carry out different jobs than other cells
Maintaining a Balance v. Some molecules can readily (easily) pass across the membrane while others cannot. v. The size, polarity, and nature of the molecules will determine whether it passes through easily or not
MOVEMENT ACROSS THE CELL MEMBRANE – Can be either passive or active – “Passive Transport” requires no energy from the cell – “Active Transport” needs cell energy in order to work
Passive Transport • Types: • 1. ) Diffusion – An overall (net) movement of substances from a region of high concentration to a region of low concentration. – This is how gases move into and out of the cell.
Examples of diffusion • Example 1 • Example 2
2. ) Facilitated Diffusion ØUses proteins as doorways into the cell ØDoes not require energy. ØMolecules attach to the proteins and are brought into the cell. ØThis is how GLUCOSE enters the cell.
Facilitated Diffusion
Video of Facilitated Diffusion • Example 1 • Example 2
3. ) Osmosis – diffusion of water across a membrane. – Water moves towards the higher solute concentration. – “Solutes” are particles dissolved in the liquid.
Osmosis • Osmotic concentration - concentration of all solutes in solution. • TYPES OF OSMOTIC SOLUTIONS: – Hypertonic -more solute outside the cell than inside. – Hypotonic - more solute inside the cell than outside. – Isotonic - solute concentrations inside and outside are equal
Maintaining Osmotic Balance
Effects of different solutions on red blood cells
Active transport v. The transport of materials against a concentration gradient which requires energy.
Active Transport • Uses energy from the cell to move molecules from a low concentration to a high concentration. • Types: • 1. ) Active transport • involves the use of energy to move substances against their concentration gradient (uphill). • Often involves highly selective protein carriers within the membrane – Example: • sodium-potassium pump
Active Transport • Vocab: – Endo- = into – Exo- = out of – 2. ) Endocytosis - the movement of material into the cell. – Examples: » phagocytosis - solids are taken into the cell. » pinocytosis - Liquids are taken into the cell. – 3. ) Exocytosis – – discharge of material out of the cell from vesicles at the cell surface
Endocytosis vs Exocytosis video • Click here
Cell Transport Review
#1 • Why is passive transport called “passive”? • A. ) It requires energy • B. ) It decreases the activation energy of a reaction. • C. ) It moves from low concentration to high concentration. • D. ) It does not need the support of mitochondria.
#2 • Which of the following is a type of passive transport? • • A. ) Diffusion B. ) Pinocytosis C. ) Exocytosis D. ) Reticulated transport
#3 • What is the relationship between osmosis and diffusion? • A. ) Osmosis is the diffusion of gases. • B. ) Osmosis is the diffusion of water from low concentration to high concentration. • C. ) Diffusion and osmosis have no relationship. • D. ) Osmosis is the diffusion of water down a concentration gradient.
#4 • Why is active transport called “active”? • A. ) It requires energy • B. ) It decreases the activation energy of a reaction. • C. ) It moves from high concentration to low concentration. • D. ) It does not need the support of mitochondria.
#5 • What active transport process is used to bring large substances into the cell? • • A. ) Exocytosis B. ) Facilitated diffusion C. ) Endocytosis D. ) All of the above are true.
#6 • If an animal cell is placed into a hypotonic solution of distilled water, what will happen to the cell? • • A. ) the cell will shrink B. ) the cell will undergo lysis C. ) the cell will stay the same size D. ) the cell will do all of the above.
#7 • If a human red blood cell is placed into a hypertonic solution of 1% salt, what will happen to the cell? • • A. ) the cell will shrink B. ) the cell will undergo lysis C. ) the cell will stay the same size D. ) the cell will do all of the above.
#8 • What type of osmotic solution is “normal” for an animal cell? • • A. ) Osmosis B. ) Hypertonic C. ) Isotonic D. ) Hypotonic
#9 • What type of osmotic solution is “normal” for a plant? • • A. ) Osmosis B. ) Hypertonic C. ) Isotonic D. ) Hypotonic
10 • What type of organic macromolecule is the cell membrane mainly composed of? • • A. ) Glycoproteins B. ) Proteoglycans C. ) Amino acids D. ) Phospholipids
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