Cells - Uplift Education

Cells - Uplift Education

Plasma membrane structure and function August 27-28, 2015 Plasma Membrane Selectively permeable barrier between the cell and the environment.

Plasma Membrane Selectively permeable barrier between the cell and the environment. What does selectively permeable mean? Plasma Membrane Selectively permeable barrier between the cell and the environment.

What does selectively permeable mean? Only some materials can cross the membrane Selective permeability is necessary for the cell to maintain the correct internal environment for physiological functions. Plasma Membrane Structure Plasma Membrane components

Phospholipids Make up the majority of the membrane Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside Plasma Membrane components

Phospholipids Make up the majority of the membrane Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside Hydrophilic = ___________ Hydrophilic molecules are __________ like

water. Hydrophobic = ____________ Hydrophobic molecules are __________ like oil. Plasma Membrane components Phospholipids Make up the majority of the membrane Arranged in a bilayer, with

hydrophilic heads outside, and hydrophobic tails inside Hydrophilic = water loving Hydrophilic molecules are polar like water. Hydrophobic = water fearing Hydrophobic molecules are nonpolar like oil. Plasma Membrane components

Phospholipids The structure of phospholipids is the key to their function! Hydrophilic heads can interact with watery external environment and watery cytoplasm. Hydrophobic tails reduce the diffusion of water and other charged or polar substances across the membrane.

Plasma membrane components Cholesterol Makes the cell membrane more rigid and less permeable to water Proteins Act as enzymes, pores, carriers, and hormone

receptors, and structural elements Plasma membrane components Glycoproteins and Glycolipids Glyco = sugar! Influence cell interactions (e.g. identifying cell as self) and molecule transport Quick Review:

Plasma Membrane Structure Talk with a partner then share as a class Scholar on the left answers What are the 4 membrane components? Which component has most functions? Why? Scholar on the right answers Name 4 functions of membrane proteins

Which two components are primarily responsible for reducing fluid loss through the cell? What do those components have in common? Cell Transport Vocabulary ____________ a dissolving agent (water, usually) ____________ substances dissolved in a solution

____________ watery environment outside cells ____________ lower solute concentration ____________ higher solute concentration

____________ equal solute concentration Cell Transport Vocabulary Solvent: a dissolving agent (water, usually)

Solute: substances dissolved in a solution Interstitial fluid: watery environment outside cells Hypotonic: lower solute concentration

Hypertonic: higher solute concentration Isotonic: equal solute concentration Transport mechanisms Transport of materials across the cell membrane can be characterized as passive or active.

Transport mechanisms Transport of materials across the cell membrane can be characterized as passive or active. Passive mechanisms require NO ENERGY from the cell. ALL passive mechanisms transport molecules down their concentration gradient. Active mechanisms require energy from the cell. Passsive Transport Diffusion Diffusion is the net movement of molecules

down their concentration gradient. Results from the random movement of molecules. Diffusion animation Passsive Transport Diffusion Simple Diffusion diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples:

Passsive Transport Diffusion Simple Diffusion diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples: fats, fat-soluble vitamins, O2, CO2, Cl-

Passsive Transport Diffusion Simple Diffusion diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples: fats, fat-soluble vitamins, O2, CO2, ClOsmosis is simple diffusion of water.

Passsive Transport Diffusion Facilitated diffusion - diffusion using a protein carrier; used for large polar molecules Example: glucose Passsive Transport Filtration Filtration occurs when water and solutes are pushed through a membrane by hydrostatic (fluid) pressure.

Water and solutes move down pressure gradient. Process by which blood is filtered in the kidney. Quick Review: Passive Transport Wait 30 sec, then show answer with your fingers What 2 things do all passive transport mechanisms have in common?

1) Membrane proteins are always involved and no energy is required 2) Membrane proteins are always involved and energy is required 3) Molecules move down a gradient and no energy is required 4) Molecules move down a gradient and energy is required Quick Review: Passive Transport Wait 30 sec, then show answer with your fingers

What 2 things do simple and facilitated diffusion have in common? 1) Membrane proteins are always involved and no energy is needed 2) Membrane proteins are always involved and energy is required 3) Molecules move down their concentration gradient and no energy is needed 4) Molecules move down their concentration gradient and energy is required

Quick Review: Passive Transport How is each molecule transported? Show 1) Simple diffusion through lipids 2) Simple diffusion through protein pores 3) Facilitated diffusion using carrier proteins a) b) c) d)

Water CO2 Glucose Cl- Quick Review: Passive Transport How is each molecule transported? Show 1) Simple diffusion through lipids 2) Simple diffusion through protein pores 3) Facilitated diffusion using carrier proteins

a) b) c) d) Water - 2 CO2 - 1 Glucose - 3 Cl- - 2 Quick Review: Passive Transport

Use the picture to answer. In which direction will ions diffuse? 1) into the cell 2) out of the cell In which direction will osmosis occur? 1) into the cell 2) out of the cell Quick Review: Passive Transport Use the picture to answer.

In which direction will ions diffuse? 1) into the cell 2) out of the cell In which direction will osmosis occur? 1) into the cell 2) out of the cell Active Transport Active transport requires the use of energy (ATP) to transport material across the cell. Active transport is used for

Solutes moving against the concentration gradient - or Very large substances Active Transport Solute Pumping (aka active transport) Membrane proteins (called solute pumps) use ATP to carry solutes against their concentration gradient.

Examples: amino acids and most ions Active Transport Exocytosis - movement of materials out of the cell by vesicle Examples: hormones, neurotransmitters, mucus, some wastes Active Transport

Endocytosis movement of materials into the cell by vesicle Active Transport Endocytosis movement of materials into the cell by vesicle Phagocytosis (cell eating) white blood cells engulf bacteria, dead cells, and

foreign debris Pinocytosis (cell drinking) used to take up droplets of fats and dissolved proteins Animation Homeostatic Imbalance Many diseases are caused by malfunctions in cell membrane transport. Examples: Cystic Fibrosis: a Cl- channel is missing, causing Cl- to build up within the cell

Familial hypercholesterolemia cholesterol receptors on cell membrane missing, so cholestrol builds up in the blood Burned tissue weeps fluids, proteins, ions, etc. Exit Ticket Draw a detailed picture of the cell membrane. Include, and label: The structural components Phospholipids, cholesterol, membrane proteins,

glycoproteins, glycolipids The transport mechanisms Simple diffusion, osmosis, facilitated diffusion, solute pumping, exocytosis, pinocytosis, phagocytosis When done, compare with a neighbor, but dont add to it.

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