Week 7

Exam 3 will be everything from here until right before the exam

The cell and Organelles ppt

Polysaccharide cell walls:

• plants have cell walls made of cellulose

• Fungal cells have a cell wall made of glucans, Mannans, and chitin

• Most bacteria have a cell wall made of a peptidoglycan called Murein

• Have cellulose with beta-linkages- which we can’t break down

• Repeating units are bacteria cell walls

• Chitin also have repeating cell walls

Membrane Transport ppt

Solvent= a substance (like water) in which solutes (like a sugar) can be dissolved

Osmolarity = the total concentration of all solute particle in a solution

Osmolality = the number of solute particles dissolved in 1 kg (1 Liter) of water, and reflects a solution’s ability to cause osmosis

Osmosis= the diffusion of a solvent through a selectively permeable membrane

• water is capable of diffusing though a plasma membrane, en though it is highly polar

• Occurs when:

  • The water concentration differed on 2 sides of a membrane

  • The osmalality differs on the 2 sides of a membrane

    • We have more of a particular solute on one side of the cell

  • The cell membrane is permeable to both solute molecules and water- both sides of the membrane are equal

  • The cell membrane is impermeable to solute molecules, but permeable to waster - the water will diffuse through, resulting a dilution on one side, until both side of the wall have equal concentrations

Osmalality:

• in bio systems, it is measure in milliosmols (mOsm)

  • Normal osmolality of blood plasma is 300 mOsm/l

  • Sea water is 1,000 mOsm/

    • Cartilaginous salt water fish have a blood plasma of 1035 mOsm/l

  • Gatorade is ~ 330 mOsm/l

    • Don’t give it to kids under 12

Tonicity:

• Isotonic: the osmolalities of fluid on sides of a membrane are equal

• Hypertonic: concentration on one side of the membrane is higher

• Hypotonic: the side of the membrane that has a lower concentration

• The tonicity is the ability of a solution to change the shape or tone of cells by altering their internal water volume

  • If an animal cell is placed in a hypertonic solution, the cell will shrivel and die

    • If placed in a Hypotonic solution, the cell will swell and burst

  • If a plant cell is placed in a hypertonic solution it will plasmolyzed

    • If placed in a hypotonic solution it will Turgid

Cellular Transport:

• in addition to water, There are many solutes that also travel across the membrane

  • Gases, ions, small organic molecules

• Many drugs are also capable of crossing membrane to reach their intracellular targets

• Inside the cell, there are also things that can travel through the membranes of organelles

Solute Transport:

• solutes cross membranes by 3 different mechanisms:

  • Simple diffusion = passive movement of suite molecules through a membrane

    • Is exergonic (down the concentration gradient)

    • Like Na+ and K+

  • Facilitated diffusion = passive movement of suite molecules with the assistance of a transport protein embedded in the membrane

    • Is exergonic

  • Active transport = similar to facilitated diffusion but requires energy (from ATP), and also needs a transport protein)

    • Is endergonic (up the concentration gradient)

    • Like NaK pump

Simple diffusion:

• transport of gases, non polar molecules and very small polar molecules 9water, glycerol, ethanol)

• The ability of gases to disuse passively enables erythrocytes in blood to easily take up O2 and CO2.

  • For example, when Exercising:

    • CO2 goes from outside cells to the blood plasma and the erythrocyte where it turns into H2CO3, then dissociates

    • Hemoglobin carrying O2 gets rid of the O2 and sends it out of the erythrocyte and blood plasma

    • Chloride shift also occurs from plasma to erythrocyte

    • This makes your blood acidic

  • The opposite also occurs during breathing, when CO2 is released in the lungs so your body can get rid of it

• The rate of simple diffusion is directly proportional to the concentration difference for that substance on opposite sides of the membrane

  • There are plenty of places for these substances to move in and out of the cell, so it is a linear relationship

Facilitated Diffusion:

• for substances that are too large or too polar to cross the membrane through simple diffusion

• These solutes can move into and out of cells and organelles only with the help of transport proteins

• The movement of solutes by this process always follow the concentration (uncharged molecules) or electrochemical (ions) gradient

  • Opposites attract

• The rate is limited by the umber of transport proteins specific for the solute being moved.

  • This is Hyperbolic

• 2 types of transport proteins utilized:

  • Channel proteins

  • Carrier proteins

Channel proteins:

• contains a fluid-filled tube that allows ions and molecules to rapidly moved into or out of the cell

• Ion channels are remarkably selective base on the charge and size of the ion

• Some are always open, some are gated (voltage gated channels) or specific signal molecules (ligand-gated), or even stretching or compressing the membrane (mechanically-gated)

• Crucial for maintaining proper salt balance

• Special types:

  • Aquaporins: allow water to flow more rapidly into and out of the cell

  • Porins: involved in passive transport of hydrophilic molecules of various sizes and charges

    • Allows passage of nutrients into a cell, while allowing passage of toxins and waste out of the cell