Lecture 3: Cell Membranes and Transport Flashcards

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1
Q

Selective Permeability

A

Allows some substances to cross it more easily than others

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2
Q

Fluid Mosaic Model

A
  • Cellular mebranes are fluid mosaics of lipids and proteins
  • Phosolipids are he most abundant lipid in the plasma membrane, forming a phospholipid bilayer
  • Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions
  • The fluid mosaic model states that a membrane is a fluid structure wth a “mosaic” of various proteins embedded in it
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3
Q

Steroid cholesterol

A
  • Acts as essential building blocks of the plasma membranes, plays pivotal roles in maintaining the structural integrity and regulating the fluidity of cell membranes
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4
Q

Cholesterol has different effects on membrane fluidity at different temperatures;

A
  • Cholesterol restrains movement of phospholipids at warm temperatures
  • Cholesterol maintains fluidity by preventing tight packing at cool temperatures
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5
Q

Membrane Proteins (and functions-ish)

A

-Peripheral proteins (are not embedded)
- Integral proteins (penetrate the hydrophobic core and often span the membrane)
- Transmembrane proteins (integral proteins that span the membrane)

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6
Q

6 Major functions of membrane proteins”

A
  • Transport
  • Enzymatic activity
  • Signal transduction
  • Cell-cell recognition
  • Intercellular joining
  • Attachment to the cytoskeleton and extracellular matrix (ECM)
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7
Q

3 different Movements across membranes

A
  1. Passive Transport
    a) Diffusion
    b) Facilitated diffusion
  2. Active Transport
    a) Primary
    b) Secondary
  3. Excoytosis and Endocytosis
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8
Q

Osmosis

A

The diffusion of water across a selectively permeable membrane (direction detrmined only by a difference on total solute concentration)

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9
Q

Isotonic Solution:

A

Solute concentration is the same as that inside the cell; no net water movement across the PM

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10
Q

Hypertonic Solution:

A

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

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11
Q

Hypotonic Solution:

A

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

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12
Q

Active tansport:

A
  • Active transport moves substances against their concentration gradient
  • Active tranport requires energy, usually in the form of ATP
  • Active transport is performed by specific proteins embedded in the membranes
  • The sodium-potassiumm pump is one of the most important active transport system in animal cells
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13
Q

Uniport

A

Movement of 1 molecule across a cell membrane inependant of the oher moleculles is known as a uniport

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14
Q

Symport

A

Movement of 2 molecules in the same direction through a protein channel is known as symport

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15
Q

Antiport:

A

Movement of 2 molecules in the opposite direction through a protein channel known as antiport (exchanger or counter-transporter)

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16
Q

Cotransport

A

Cotranpost occurs when active transport of a solute indirectly drives transport of another

17
Q

2 Types of Active Transport:

A

Primary (direct) Active Transport- in which the energy is derived directly from the breakdown of adenosine triphosphate (ATP)
Secondary (Indirect) Active Transport- (co-transport) tha uses an electrochemical gradient created by the primary active transport

18
Q

Exocytosis

A

An active process of moving materials from within a cell to the exterior of the cell (many secretory cells use exocytosis to export their products)

19
Q

Endocytosis

A

An active cellular process in which substances are brought into the cell (is a reversal of exocytosis, involving different proteins)
3 types

20
Q

3 types of endocytosis:

A
  • Phagocytosis (“cellular eating”): Cell engulfs particle in a vacuole
  • Pinocytosis (“cellular drinking”): Cell creates vesicle around fluid
  • Receptor-mediated endocytosis: Binding of ligan to receptors triggers vesicle formation