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N106 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

Cell theory

A

Four basic concepts of cell theory

  1. Cells are the building blocks of all plants and animals
  2. Cells are the smallest functioning units of life
  3. Cells are produced through division of preexisting cells
  4. Each cell maintains homeostasis
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2
Q

Cells in the human body

A
  • trillions of cells in the human body
  • homeostasis of body maintained by coordinated action of cells
  • cells come in variety of shapes and sizes
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3
Q

The study of cell

A
  • cytology
  • study of the structure and function of cells
  • studied using microscopes
  • light microscopy (LM)
  • electron microscopy (EM)
  • transmission electron microscopy (TEM)
  • scanning electron microscopy (SEM)
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4
Q

Overview of cell anatomy

A
  • wide variety of cell anatomy
  • all cells have a plasma membrane or cell membrane
  • separates cell contents (cytoplasm) from surrounding environment (extra cellular fluid)
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5
Q

Four key functions of plasma membrane

A
  1. Provides cell with physical isolation from extra cellular fluid
  2. Regulation of exchange with the environment
  3. Allows for sensitivity to the environment
  4. Provides for structural support
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6
Q

The plasma membrane structure

A
  • extremely thin (6nm-10nm)
  • components
  • lipids
  • proteins
  • carbohydrates
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7
Q

Membrane lipids

A
  • Phospholipids are major components of plasma membrane
  • cholesterol gives “stiffness” to plasma membrane
  • makes it less fluid and less permeable
  • membrane also contains small amounts of other lipids
  • lipid-soluble materials cross membrane easily
  • ions and water-soluble compounds do not cross lipid portion
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8
Q

Phospholipid bilayer

A
  • chemical properties of phospholipids results in formation of phospholipid bilayer
  • hydrophilic nonlipid “head” in each layer faces watery environment (extra cellular fluid on outside or intracellular fluid on inside of the cell)
  • hydrophobic “tails” of phospholipids move away from watery environment and face each other
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9
Q

Membrane proteins

A
  • several types of proteins associated with plasma membrane
  • most common are transmembrane proteins that span width of membrane
  • proteins can “drift” within membrane or remain in specific position
  • membrane composition can change over time
  • membrane protein functions
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10
Q

Six major functions

A
  1. Receptors
  2. Channels
  3. Carriers
  4. Enzymes
  5. Anchors
  6. Identifiers
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11
Q

Membrane carbohydrates

A
  • join with proteins and lipids to form complex molecules on outer surface of membrane
  • combine with lipids to form glycolipids
  • combine with proteins to form glycoproteins
  • function as lubricants and adhesives,receptors, and part of immune system “self” recognition
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12
Q

Permeability

A

-Ease with which substances can cross a membrane
-in cell, determines which substances can enter or leave cytoplasm
Impermeable membrane = nothing can cross
Freely permeable = anything can cross
Selectively permeable = some things can cross; others cannot
(Describes plasma membranes)

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13
Q

Movement across the membrane

A

Passive processes
- require no energy
Eg. Diffusion, osmosis, facilitated diffusion

Active processes
-require energy, usually from ATP
Eg. Active transport, vesicular transport

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14
Q

Diffusion

A
  • molecules are in constant motion
  • random collisions spread out molecules
  • this movement from area of high concentration to a area of low concentration called diffusion
  • difference between concentrations called concentration gradient
  • diffusion proceeds “down concentration gradient”
  • Molecules eventually uniformly distributed
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15
Q

Diffusion across plasma membranes

A
  • Plasma membrane selectively restricts diffusion
  • Diffusion possible through:
  • Crossing lipid portion of membrane
  • Lipid-soluble drugs, alcohol, fatty acids, steroids, and dissolved gases (e.g., oxygen and carbon dioxide)
  • Passing through channel proteins
  • Small water-soluble compounds, water, ions
  • Large water-soluble molecules will require a carrier
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16
Q

Characteristics of osmosis

A
  1. Diffusion of water molecules across a selectively permeable membrane
  2. Occurs across a selectively permeable membrane that is freely permeable to water but not freely permeable to solutes (dissolved materials)
  3. Water flows from low solute concentration to high solute concentration
17
Q

Osmotic pressure

A
  • Indication of the force of the water movement into a solution as a result of solute concentration
  • Increase in solute concentration = increase in osmotic pressure
  • Can be measured as amount of hydrostatic pressure required to oppose flow of water
  • Water moves toward the higher concentration of solutes, until equilibrium is reached
18
Q

Tonicity

A

The effect of solute concentrations on the shape or tension of the cell membrane

19
Q

Isotonic solution

A
  • Does not cause net movement of water into or out of cell
  • Water molecules move in and out at equal rate
  • Cell retains normal appearance
20
Q

Hypotonic solution

A
  • Net flow of water into the cell
  • Causes cell to swell and perhaps burst (lyse)
  • In red blood cells, this is called hemolysis
21
Q

Hypertonic solution

A
  • Net flow of water out of the cell
  • Causes cell to shrivel and dehydrate
  • In red blood cells, shrinking is called crenation
22
Q

Carrier-Mediated Transport

A
  • Process using membrane proteins to move specific ions or organic substrates across plasma membrane
  • Can be passive (no ATP required) or active (ATP dependent)
  • Carrier proteins
  • Are specific to a substrate (e.g., glucose carrier will not carry other simple sugars)
  • Can be used repeatedly
23
Q

Types of Carrier-Mediated Transport

A

-Cotransport
-Carrier moves two substances in same direction
-Countertransport
-Carrier moves two substances in opposite directions
Examples of carrier-mediated transport
-Facilitated diffusion
-Active transport

24
Q

Facilitated diffusion

A
  • Uses carrier proteins to passively move larger compounds down concentration gradient
  • Compound binds to receptor site on carrier protein
  • Protein changes shape and moves compound across membrane
  • Limited number of carriers prevents diffusion rate from indefinite increase
  • No further increase in rate once all carriers are bound
25
Q

Active transport

A
  • Requires energy from ATP
  • Can move substances against concentration gradient
  • Ion pump transports essential ions across plasma membranes
  • Exchange pump is an ATP-driven countertransport mechanism
  • Best example is sodium–potassium exchange pump
26
Q

Vesicular transport

A

-Moves materials into or out of cell in small membrane-enclosed sacs called vesicles
-Vesicles fuse with plasma membrane
Two major categories
1. Endocytosis
2. Exocytosis

27
Q

Endocytosis

A
  • Packages extracellular materials in vesicles at cell surface and moves them into the cell
  • Active process that requires energy
  • Three major types
28
Q

Receptor-mediated endocytosis

A
  • Pinocytosis

- Phagocytosis

29
Q

Receptor-Mediated Endocytosis

A
  • Begins when receptors on plasma membrane surface bind to specific target molecules (ligands)
  • In-pouching of plasma membrane forms coated vesicle
  • Ligands are removed from the vesicle
  • Receptors recycled to be used again
30
Q

Pinocytosis

A
  • Pinocytosis or “cell drinking”
  • Pocket forms in plasma membrane
  • Forms small vesicles filled with extracellular fluid
  • No receptors involved
  • Process common to most cells
31
Q

Phagocytosis

A
  • Phagocytosis or “cell eating”
  • Produces vesicles containing solid objects
  • Cytoplasmic extensions (pseudopodia) surround an object outside the cell
  • Membrane fuses to form vesicle around object
  • Vesicle fuses with lysosomes inside the cell and contents are digested
  • Process unique to specialized cells that protect tissues
32
Q

Exocytosis

A
  • Reverse of endocytosis
  • Vesicle created inside the cell
  • Vesicle fuses with plasma membrane
  • Contents discharged to extracellular environment

N106 (6 decks)

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