Chapter 7: Cell Membrane (Test 2) Flashcards

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1
Q

Phospholipids are the most abundant lipid in the plasma membrane​

Phospholipids are ___ molecules, containing hydrophobic and hydrophilic regions​

The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

A

amphipathic

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2
Q

___ studies of the plasma membrane supported the fluid mosaic model​

Freeze-fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer

A

Freeze-fracture

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3
Q

Phospholipids in the plasma membrane can move within the bilayer​

Most of the phospholipids drift laterally, but rarely does a molecule flip-flop transversely across the membrane​

Some proteins drift within the phospholipid bilayer​

Other proteins never move and are anchored to the cytoskeleton below

A
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4
Q

As temperatures cool, membranes switch from a fluid state to a solid state​

Components of membrane types of lipids​

Membranes rich in unsaturated fatty acids are more fluid that those rich in saturated fatty acids

A
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5
Q

Cholesterol acts as a “temperature buffer” for the membrane​

At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids​

At cool temperatures, it maintains fluidity by preventing tight packing

A
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6
Q

___ proteins penetrate the hydrophobic core ​

___ proteins are bound to the surface of the membrane

A

Integral

Peripheral

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7
Q

Six major functions of membrane proteins:​

  • Transport​
  • Enzymatic activity​
  • Signal transduction​
  • Cell-cell recognition​
  • Intercellular joining​
  • Attachment to the cytoskeleton and extracellular matrix (ECM)
A
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8
Q

___ molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly​

___ molecules, such as sugars and ions do not cross the membrane easily

A

Hydrophobic (nonpolar)

Hydrophilic (polar)

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9
Q

___ is the tendency for molecules to spread out evenly. (molecules move from areas of higher to lower concentration)​

Although each molecule moves randomly, diffusion of a population of molecules may exhibit a net movement in one direction​

At ___ , as many molecules cross one way as cross in the other direction

A

Diffusion

dynamic equilibrium

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10
Q

Substances diffuse down their ___, the difference in concentration of a substance from one area to another​

No work must be done to move substances down the concentration gradient​

The diffusion of a substance across a biological membrane is ___ because it requires no energy from the cell to make it happen

A

concentration gradient

passive transport

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11
Q

___ is the diffusion of water across a selectively permeable membrane​

Water diffuses across a membrane from the region of lower solute(higher water molecules) concentration to the region of higher solute (lower water molecules) concentration

A

Osmosis

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12
Q

___ is the ability of a solution to cause a cell to gain or lose water

A

Tonicity

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13
Q

___: Solute concentration is less than that inside the cell; cell gains water

A

Hypotonic solution

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14
Q

___: Solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

A

Isotonic solution

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15
Q

___: Solute concentration is greater than that inside the cell; cell loses water

A

Hypertonic solution

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16
Q

Hypertonic or hypotonic environments create challenges for organisms​

___, the control of water balance, is a necessary adaptation for life in such environments

A

Osmoregulation

17
Q

In ___, transport proteins speed the passive movement of molecules across the plasma membrane

A

facilitated diffusion

18
Q

___ allow passage of hydrophilic substances across the membrane​

___ provide corridors that allow a specific molecule or ion to cross the membrane​

  • Aquaporins- for facilitated diffusion of water​
  • Ion channels- open or close in response to a stimulus (gated channels)
A

Transport proteins

Channel proteins

19
Q

___ undergo a subtle change in shape that translocates the solute-binding site across the membrane

A

Carrier proteins

20
Q

___ moves substances against their concentration gradient​

Active transport requires energy, usually in the form of ATP​

Active transport is performed by specific proteins embedded in the membranes

A

Active transport

21
Q

Active transport allows cells to maintain concentration gradients that differ from their surroundings​

The ___ is one type of active transport system

A

sodium-potassium pump

22
Q

Large molecules, such as polysaccharides and proteins cross the membrane in bulk via packaging in vesicles​

Bulk transport requires energy

A
23
Q

In ___, transport vesicles migrate to the membrane, fuse with it, and release their contents out of cell​

Many secretory cells (like those in the pancreas secreting insulin) use exocytosis to export their products

A

exocytosis

24
Q

In ___, the cell takes in macromolecules by forming vesicles from the plasma membrane​

Endocytosis is a reversal of exocytosis, involving different proteins​

There are three types of endocytosis:​

Phagocytosis (“cellular eating”)​

Pinocytosis (“cellular drinking”)​

Receptor-mediated endocytosis

A

endocytosis

25
Q

In ___ a cell engulfs a particle in a food vacuole​

The vacuole fuses with a lysosome to digest the particle

A

phagocytosis

26
Q

In ___, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles

A

pinocytosis

27
Q

In receptor-mediated endocytosis, vesicle formation is triggered by signals from outside the cell that bind to receptors on plasma membrane

A