Chapter 8: Biological Membranes Flashcards Preview

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Flashcards in Chapter 8: Biological Membranes Deck (18):
1

Fluid Mosaic Model of Plasma Membranes

 

Components of plasma membranes?

Fluid Mosaic Model of Plasma Membranes

 

  • The plasma membrane of a cell is a mosaic of various components that move around like fluid.
    1. Lipids
      • Phospholipids = amphipathic molecules (hydrophillic head + hydrophobic tails)
        • Phosphate head
        • Glycerol backbone
        • 2 fatty acid tails
      • Cholesterol = steroid derivative that maintains the fluidity of the membrane
    2. Proteins
    3. Carbohydrates
  • It is a semipermeable barrier
    • Allows fat-soluble components to cross easily
    • Larger and water-soluble compounds must enter via channels or carriers

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2

Why are unsaturated fatty acids better for you than saturated fatty acids?

  • Unsaturated fatty acids have double bonds, thus they are more fluid at room temperature.
    • These are benefit the fluidity of our cell plasma membranes.
  • Saturated fatty acids have no double bonds, thus are more solid at room temperature
    • They prevent the fluidity of cell plasma membranes, which is bad.

 

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3

What is a wax?

Waxes in cell membranes

found in plant or animal cell membranes?

Waxes are only found in plant cell membranes

 

A wax is a long chain fatty acid with a long chain alcohol

 

They provide stability and rigidity in plant cell membranes

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4

Transmembrane proteins

Embedded proteins

Peripheral proteins

  • Transmembrane proteins = proteins that pass through the entire plasma membrane

 

  • Embedded proteins = proteins that pass through one side of the plasma membrane (interior or exterior)

 

  • Peripheral proteins = proteins that do not pass through any part of the membrane; instead, they are connected to it.
    • ex: G-proteins

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5

Carbohydrates and the cell membrane

Carbohydrates are generally hydrophilic

thus, they are found attached to the outside of plasma membranes.

 

used to identify certain cells

 

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6

Gap Junctions

 

Can water and solutes pass between cells in gap junctions?

Gap Junctions

  • Type of cell-cell communication
  • Protein channels on two cells combine to form a tunnel between the cells.
  • In gap junctions, water and solutes can pass between cells

 

example: electrical synapses

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7

Tight Junctions

 

can water molecules and solutes pass through?

Tight Junctions:

  • Cell-cell communication.
  • A very tight connection between two cells, which is so tight that it prevents any water molecules and solutes from passing though.

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8

Desmosomes

 

can water and solutes pass through?

 

are they involved in cell-cell communication?

Desmosomes

  • not involved in cell-cell communication
  • Cells connect by anchoring their cytoskeletons to each other.
  • Water and solutes can pass through

 

they care not involved in cell-cell communication

 

9

3 types of cell-cell junctions

 

which one(s) allow water and solutes to pass?

 

which type is involved in cell-cell communication

  1. Gap junctions = protein channels between cells form a tunnel between them.
    • Allow water and solutes to pass
    • only type that is involved in cell-cell communication
  2. Tight junctions = cells form a very tight layer between them.
    • Too tight
    • Water and solutes CANNOT pass
  3. Desmosomes = cells anchor their cytoskeletons to each other
    • Water and solutes can pass

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10

Thermodynamics of passive transport and activate transport

  • passive transport occurs when molecules pass through the membrane without using energy (ΔG = -)
    • spontaneous
    • and entropy increases
  • active transport occurs when molecules pass through the membrane by using energy (ΔG = +)
    • nonspontaneous

11

Passive transport

 

Simple diffusion

Osmosis

Facilitated difussion

 

what type of molecules are permeable to the membrane

  • Passive transport through cell membranes in which molecules move down their concentration gradients
    • from higher concentration to lower concentration
  • 3 Types:
    1. Simple diffusion = molecules that are permeable to the membrane freely pass down their concentration gradients
    2. Osmosis = water moves from areas of higher water concentration to lower water concentration
      • From low solute concentration to high solute concentration
    3. Facilitated diffusion  = the diffusion of molecules that are impermeable to the membrane via protein channels or transporters
      • (large, polar, and charged molecules

 

Small, nonpolar, and uncharged molecules are permeable to the membrane and can pass

 

 

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12

what types of molecules are permeable to the plasma membrane

 

 

what types of molecules are not?

Permeable to membrane:

Small, nonpolar, and uncharged molecules are permeable to the membrane and can pass

 

Non-permeable to membrane:

Large, polar. and charged molecules cannot pass through the membrane freely

 

13

Osmosis

 

Hypotonic solution

Isotonic solution

Hypertonic solution

 

what happens in these solutions?

Osmosis

Type of passive transport

  • Water flows from regions of high water concentration to lower water concentration through a semipermeable membrane
    • from regions of low solute concentration to high solute concentration

 

  • Hypotonic solution = solution in which cells have less water inside of them.
    • Thus, water rushes into them, causing the cell to swell up and burst
  • Isotonic solution = solution in which cells have a water concentration that is equal to the external environment.
  • Hypertonic solution = solution in which cells have more water inside of them.
    • Thus, water rushes out of them, causing the cell to shrivel up

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14

Osmosis:

 

Colligative properties

Osmotic pressure

Osmosis is a type of passive transport

Osmotic pressure is a colligative property

 

  • Colligative properties = physical property of solutions that is dependent on the concentration of dissolved particles
    • does not depend on the chemical identity of the dissolved particles
  • Osmotic pressure = the pressure that is caused when water moves from regions of high to low water concentrations

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15

Active transport

Active transport

the movement of molecules against their concentration gradients

Requires energy 

Involves membrane proteins

 

ex; sodium potassium pump moving sodium and potassium up their concentration gradients in order to restore resting membrane potential

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16

Endocytosis

 

Exocytosis

 

Endocytosis = when foreign material are brought into the cell

 

 

Exocytosis = when cellular material exits the cell

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17

how many membranes do mitochondria have?

 

describe the membrane(s)

 

2 membranes

 

Outer mitochondrial membrane:

  • Highly permeable due to many large pores that allow ions and small proteins to pass

 

Inner mitochondrial membrane:

  • Less permeable compared to the outer membrane.
  • Contains many infoldings called Cristae which increase surface area for ATP synthesis. 
  • The mitochondrial matrix is found inside the inner membrane

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18

define osmolarity

osmolarity = the concentration of solute in a certain amount of solution