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Biology with Lynette > Membrane Transport > Flashcards

Membrane Transport Flashcards

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1
Q

What are the 3 fundamentally diff mechanisms involved in
the movement of solutes across membranes?

(S.F.A)

A

1 - Simple diffusion (passive transport)
2 - Facilitated diffusion (passive transport)
3- Active transport

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2
Q

How is the movement of a molecule w/ no net charge determined?

A
  • By the concentration gradient of that

molecule across the membrane.

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3
Q

What is Passive Transport/ Facilitated Diffusion?

A
  • Movement of molecules through the membrane
  • No energy is required
  • Molecules move in response to a concentration gradient
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4
Q

What is Diffusion?

A
  • movement of molecules from high concentration to low concentration.
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5
Q

What is simple diffusion?

A

Is the movement of many small molecules across the cell membrane.

  • Each substance (molecule) diffuses independently of others present.
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6
Q

What is the rate of diffusion affected by?

A
  • Concentration gradient – faster when steep

- Size of molecule – smaller molecules like O2 will diffuse faster than large molecules like carbs.

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7
Q

What is the permeability of the cell wall?

A

cell wall is selectively permeable

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8
Q

What does the selectively permeable cell wall let through?

A
  • Small Molecules
  • water
  • non charged molecules pass easily through the phospholipid bilayer of the membrane.
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9
Q

What is Osmosis in relation to passive transport? (see pics slide 9)

A

Is the passive movement of water across a semi - permeable membrane in response to the conc gradient.

It is the movement of water from a region of high water conc to a region of low water conc.

  • movement of water toward an
    area of high solute
    concentration (dissolved
    substances are the solutes)
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10
Q

What is Tonicity?

A

the relative concentration of solutes between both extracellular and intracellular fluid.

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11
Q

If one fluid has a higher solute concentration (hypertonic) than the other
(hypotonic) then H2O moves from the hypotonic fluid to hypertonic one.

A

Read.

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12
Q

What is Isotonic?

A

If the conc of solute is equal in both fluids then they will have the same osmotic pressure and water will diffuse in and out of the cell at the same rate.

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13
Q

What are Integral Membrane Proteins?

A

They are transport proteins that recognize substances w/ great specificity and speed their movement across the membrane.

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14
Q

What is Facilitated Diffusion?

A
  • movement of a molecule from high to low concentration w/ the help of a protein.
  • Specific bc each protein transports a
    specific molecule.
  • Passive bc no energy needed
  • saturated when all carriers are occupied.
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15
Q

What are transport proteins? examples

A
  • Are specific bc each protein transports a specific molecule.
    e. g. Chanel + carrier proteins
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16
Q

What are Channel Proteins?

see pics slide 17

A
  • Forms a pore extending across the lipid bilayer.

- When pore is open, the Specific molecule enters and passes through lipid bilayer.

17
Q

What are Carrier Proteins?

see pics slide 17

A

Binds the specific molecule to be transported and the protein undergoes a change in shape in order to transfer the bound molecule across the membrane.

18
Q

What are the 2 Channel Proteins?

A
  • Ion Channels.

- Gated Channels.

19
Q

What is an Ion Channel?

A
  • Allow the passage of ions (charged atoms or molecules) which are associated with water.
20
Q

What is the Gated Channel?

A
  • Is opened or closed in response to a stimulus.

the stimulus may be chemical or electrical

21
Q

What are the 3 carrier proteins called in order? (U.S.A)

A
  • Uniports
  • Symports
  • Antiports
22
Q

What is the Uniport?

see pics slide 19

A
  • Transport a single particle in one direction.

e. g. Facilitated diffusion of glucose.

23
Q

What is the Symport?

see pics slide 19

A
  • Transport requires the binding of more than one substance to the transport protein
  • The substances are transported across the membrane together.
24
Q

What is the Antiport?

see pics slide 19

A
  • The transport proteins exchange one substance for another.

Eg: Na, K ATPase

25
Q

What is Active Transport?

A
  • The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
    Feedback.
26
Q

What are the functions of Active Transport?

A

1: Taking essential nutrients from the environment or surrounding fluid (even tho the conc in the cell is higher).
2: Removes secretory products + waste material from the cell/organelle ( even tho the conc outside is higher)

3: Allows the cell to maintain constant, nonequilibrium intracellular conc of specific inorganic ions ((potassium,
sodium, calcium, hydrogen).

27
Q

Sodium-potassium (Na+-K+) pump
▪ Found in virtually all animal cells
▪ This active transport mechanism uses an antiporter to move 3 Na+ out of the cell and 2 K+ into the cell
▪ Animal cells have high intracellular level of potassium ions about 31:1 ratio of internal: external levels and a low intracellular level of sodium ions, about 0.08:1 ratio of internal: external levels.
▪ Both the inward pumping of potassium ions and the outward pumping of sodium ions are therefore energy-requiring processes, as both ions are being moved up
their electrochemical gradients (ion charge difference on both sides of membrane)
▪ ATP energy is used to change the conformation of the carrier protein

A

read

28
Q

What are the 6 steps involved in the sodium potassium pump?

A
  1. Initial binding of three sodium ions to on the inner side of the membrane.
  2. The binding of sodium ions triggers phosphorylation of the transmembrane protein by ATP resulting in a conformational change.
  3. Bound sodium ions are moved through the membrane to the external surface, where they are released to the outside.
  4. Potassium ions from the outside bind to the transmembrane protein
  5. This triggers dephosphorylation of the protein.
  6. Dephosphorylation forces a return to the original transmembrane protein conformation. During this process, the potassium ions are moved to the inner surface, where they dissociate, leaving the carrier
    ready to accept more sodium ions.
29
Q

Products of the sodium potassium pump?

A
  • 3Na+ leave and 2K+ enter in every cycle
  • Changes in protein conformation that occur during the
    cycle are very rapid enabling each carrier to transport.
  • The Na+ concentration gradient established by the
    sodium potassium pump drives many other transport
    processes as well.
30
Q

How is Bulk Transport accomplished?

A

BY:

  • Endocytosis – movement of substances into the cell
  • Exocytosis – movement of materials out of the cell
31
Q

How many steps are involved in Endocytosis? and name these steps? (P.P.R)

A
  • 3 steps
  • Phagocytosis
  • Pinocytosis
  • Receptor-mediated endocytosis
32
Q

What is Phagocytosis?

A
  • When the cell ingests large solid particles e.g bacteria/food.
  • Lysosome attach and release enzymes to break down particle.
  • Folds of the membrane enclose the particle eg.
    Phagocytic W.B.C use endocytosis to destroy bacteria.
33
Q

What is Pinocytosis?

A
  • Transportation of liquid droplets into the cell.
  • When a cell absorbs small particles outside the cell and brings them inside. In this process, the cell surrounds particles “pinching off” part of its membrane to enclose the particles within vesicles.
34
Q

What is Receptor-mediated endocytosis?

A
  • When the Plasma membrane lined w/ receptors for specific molecules.
  • Receptor bound molecules migrate into coated pits - coated vesicles – coating dissociates leaving vesicle free in cytoplasm.
35
Q

What is Exocytosis? (Slide 35)

A
  • Occurs when material is discharged from the cell.

- Vesicles in the cytoplasm fuse with the cell membrane and release their contents to the exterior of the cell

36
Q

What is Exocytosis used for in both plants and animals?

see pics slide 35

A
  • Used in plants to export cell wall material.

- Used in animals to secrete hormones, neurotransmitters, digestive enzyme.

Biology with Lynette (11 decks)

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