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Anatomy & Physiology I > Ch. 3 - Part 1, The Plasma Membrane > Flashcards

Ch. 3 - Part 1, The Plasma Membrane Flashcards

1
Q

Cell Theory (4 items)

A
  1. A cell is the basic structural and function unit of living organisms.
  2. activity of an organism depends on the individual and combined activities of its cells
  3. Principle of structure and function - activities of cells are dictated by their shapes and by relative number of subcellular structures they contain
  4. cells can only arise from other cells
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2
Q

Three main parts in all human cells

A
  1. Plasma Membrane
  2. Cytoplasm
  3. nucleus
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3
Q

plasma membrane

A

selectively permeable outer boundary of the cell, separating intracellular fluid and extracellular fluid.
Made of a double layer of phospholipids, proteins, cholesterol, and glycolipids (on surface)

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4
Q

cytoplasm

A

intracellular fluid packed with organelles

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5
Q

nucleus

A

organelle that contains the controls of the cell

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6
Q

extracellular materials

A

substances that contribute to body mass that are found outside of cells. Include:

  1. body fluids
  2. cellular secretions
  3. extracellular matrix
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7
Q

interstitial fluid

A

an example of a body fluid, this is the fluid in tissues that bathes all cells. Like a nutrient rich ‘soup’ containing amino acids, sugars, fatty acids, regulatory substances, and wastes. Cells extract what they need from this mix.

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8
Q

cellular secretions

A

an extracellular material including fluids that aid in digestion (intestinal and gastric fluids) and lubricants (saliva, mucus, and serous fluids)

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9
Q

extracellular matrix

A
  • most abundant extracellular material.
  • jelly like substance made of proteins and polysaccharides, these assemble into a mesh where
  • they are a ‘cell glue’ holding body cells together
  • Particularly abundant in connective tissue
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10
Q

Phospholipid Molecule

A

molecule that makes up PM.
contains a polar, hydrophilic (water-loving) head and a nonpolar hydrophobic (water fearing) tail of two fatty acid chains. The layer lie tail-to-tail, since the polar heads are attracted to the water in the EM and IM

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11
Q

glycolipids

A

lipids with attached sugar groups, found only on the outer P.M. surface. Their role is for membrane stability and aid in cellular recognition (as part of glycocalyx)
makes up ~5% of the PM

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12
Q

Cholesterol

A

~20% of the P.M. lipids. This molecule also has a polar and nonpolar region.
it wedges it’s platelike hydrocarbon rings between the phospholipid tails, helping to stabilize and decrease the mobility and fluidity of the membrane

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13
Q

integral proteins

A

proteins of the P.M. that are firmly inserted into the lipid bilayer. They can protrude from one surface of the PM but typically transmembrane (span entire length and protrude on both sides)
Have both a polar and non polar region.
They can form a channel through the PM, act as carriers for a certain substance, or be receptors for hormones/chemical messengers and relay messages to interior (signal transduction)

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14
Q

signal transduction

A

The process of a membrane protein exposed to outside of the cell has a binding site that fits a specific chemical messenger (like a hormone).
when bound the chemical messenger may cause a change in shape of the protein that initiates a chain of chemical reactions in the cell

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15
Q

Peripheral proteins

A
  • P.M. proteins that attach loosely to integral proteins and are easily removed without disturbing P.M.
  • can attach to the cytoskeleton or extracellular matrix
  • include a network of filaments that help support the membrane on cytoplasmic side
  • Can also be enzyme, motor proteins, or link cells together
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16
Q

Glyococalyx

A

glycoprotein + glycolipids = fuzzy, sticky, carb-rich area at cell surface (sugar coats your cell)
This is a highly specific biological marker for the cell and is distinct for cells, so helps cells recognize each other (like sperm looking for ovum).
Also plays a function in binding adjacent cells

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17
Q

Ways that cells can be bound together

A
  1. glycoproteins in the glycocalyx
  2. wavy contours of adjacent cell membranes
  3. the 3 special cell junctions (tight junctions, desmosomes, gap junctions)
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18
Q

Tight Junctions

A

series of integral proteins in PM of adjacent cells that fuse together forming an impermeable junction that is continuous and encircles the cell.
these junctions prevent molecules from passing through intercellular space

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19
Q

desmosomes

A
  • anchoring junctions that hold adjacent cells together with thin linker protein filaments (cadherins) that extend from the plaques and fit together like a zipper
  • This keeps the cells from ‘tearing’ apart, so abundant in tissues that could be under mechanical stress like skin and heart muscle
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20
Q

gap junction

A
  • communicating junction between adjacent cells that allow ions and small molecules to pass.
  • Cells are connected by connexons (hollow cylinders)
  • These are present in electrically excitable tissues where ions need to pass between cells
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21
Q

Diffusion

A

Tendency of molecules/ions to move from an area of higher concentration to lower concentration (down/along their concentration gradient).
Once equilibrium is reached there is no net movement (still constant movement but equal in both directions)

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22
Q

What influences the speed of diffusion

A
  1. Size of the molecule (the smaller, the faster)

2. Temperature (the warmer, the faster)

23
Q

Simple diffusion

A

Type of passive diffusion (no ATP needed) of nonpolar and lipid-soluble substances diffusing directly through the lipid layer down their concentration gradient
(Examples - oxygen, CO2, and fat-soluble vitamins)

24
Q

Facilitated Diffusion

A
  • Type of passive diffusion for molecules that can’t pass through lipid bilayer like glucose/other sugars, some amino acids, and ions. They cannot diffuse through lipid bilayer themselves because they are polar/too big/because of their charge
  • Instead they are transported by binding to a protein in the carrier membrane (carrier-mediated) or passing through a water-filled protein channel (channel-mediated)
25
Q

Carrier-Mediated Facilitated Diffusion

A

A passive diffusion.
carrier proteins are integral proteins in the PM that transport specific polar molecules (like sugars and amino acids) by enveloping the molecule, then the carrier changes shape, which moves the binding site to interior side of the PM, releasing it inside the cell

26
Q

Channel-Mediated Facilitated Diffusion

A

A Passive diffusion
Transmembrane proteins that transport substances (usually ions/water) through aqueous channels through PM
These channels are selective due to pore size and the charge of the amino acids lining the channel.
leakage channels are always open - constantly letting ions move down concentration gradient
Gated channels - controlled by chemical/electrical signals to be open/closed

27
Q

Osmosis

A
  • Passive diffusion of a solvent, like water through selectively permeable membrane.
  • Water can either move through gaps in the PM or through aquaporins (AQP, water-specific channels).
  • Once homeostasis is reached (concentration is the same) then no net movement of water occurs.
  • AQP are particularly abundant in kidney cells
28
Q

Osmolarity

A

total concentration of all solute particles in a solution

29
Q

Hydrostatic pressure on a cell

A

The pressure of water inside the cell pushes on the interior of the PM

30
Q

Osmotic Pressure

A

pressure of water on outside of PM to move in

31
Q

Tonicity

A 
ability of a solution to change the shape/tone of cells by altering the cells' internal water volume through osmosis. Depends on the concentration of solute and the permeability fo the plasma membrane (if solute is also permeable).
Three types:
Isotonic Solutions
Hypertonic Solutions
Hypotonic Solutions
32
Q

Isotonic solution

A

solution that cell is in, has same solute concentration as inside of cell, therefore no change to shape and no net loss/gain of water via osmosis

33
Q

Hypertonic Solution

A

Solution cell is in has a higher solute concentration than inside of the cell of non-penetrating solute, so cells shrink via osmosis

34
Q

Hypotonic solution

A

solution cell is in has a lower concentration of non-penetrating solute than inside the cell, causing water to enter the cell until it finally bursts (lyse)

35
Q

active transport

A

transportation of molecules into cell requiring ATP, which is needed because:

  • the molecule is too big to pass through channels
  • unable to dissolve in the lipid bilayer
  • or is moving against it’s concentration gradient (low to high)
  • Requires carrier proteins to combine specifically and reversibly with the molecule.
  • There can be primary AT, when energy to do work comes directly from hydrolysis of ATP or secondary AT, when driven indirectly by energy stored in concentration gradients of ions that are created by primary AT
36
Q

Couple System

A

transportation of more than one substance at a time

37
Q

symport system

A

Active secondary transport when two transported substances move in the same direction
example: Sodium glucose symport - uses the kinetic energy of sodium moving down its concentration gradient into the cell, to also transport glucose into the cell against its concentration gradient

38
Q

antiport system

A

Active secondary transport when the two substances cross membrane in opposite directions
Example the Na+-H+ . When pH is out of normal range, this is activated and the kinetic energy from sodium moving into the cell down its gradient is used to remove H+ ions out of the cell, against their concentration gradient

39
Q

Primary active transportation

A

hydrolysis of ATP results in phosphorylation of the transport protein, which causes protein to change in shape in a way that it ‘pumps’ the bound solute across the P.M.
Examples include the calcium, hydrogen pumps, and sodium-potassium pump

40
Q

Na+-K+ ATPase

A

An example of active transport. Sodium-Potassium pump moves Na+ out of the cell and K+ into the cell (with use of ATP).

This then results in a concentration of K+ way higher inside the cell than out and opposite for Na+. Then these ions can also leak by down their concentration gradient via channels in plasma membrane (pasive transport)

41
Q

Secondary active transport

A

Active transport not directly from ATP. Instead it’s energized by the concentration gradient created by primary active transport.
This concentration gradient means that an ion is going to move down its concentration gradient (kinetic energy), which energizes another ion to move against its gradient (same direction = symport, opposite directions = antiport)

The Na-K Pump builds up a CG (because it pumps against it), and then when either ion goes through a channel down the concentration gradient it will take along (cotransport) another substance in the same carrier protein
some sugars, amino acids, and many ions are cotransported via secondary

42
Q

Endocytosis

A

vesicular transport involved in coming into the cell.
Starts with an infolding portion of the PM called a ‘coated pit’ that encloses the substance, which then can combine with a lysosome (contains enzymes for digestion) OR will move across the cell and released on opposite side by exocytosis (process called transcytosis)
3 types of endocytosis: phagocytosis, pinocytosis, receptor-mediated cytosis

43
Q

phagocytosis

A

type of endocytosis in which a psuedopod forma by pinching off membrane into a phagosome (vesicle) fuses with a lysosome and its contents are digested
macrophages and white blood cells are experts at this process

44
Q

pinocytosis

A

aka fluid-phase endocytosis or “cell drinking”. Unfolding PM surrounds a small volume of extracellular fluid containing dissolved molecules. No receptors are used so this is a non-specific process

45
Q

Receptor-mediated endocytosis

A

specific endocytosis and transcytosis of most macromolecules in body is via this method. The receptors are internalized in one of the pits (a coat protein) on the vesicle
Enzymes, insulin/other hormones, low-density lipoproteins (cholestoeral) and iron travel into the cell by this means.

46
Q

exocytosis

A

vesicular transport process to eject substances from cell interior to exterior. The substance is enclosed in a secretory vesicle that goes to PM, fuses with it, and then ruptures, spilling sac contents. v-SNARE and t-SNARE proteins are used for the docking process at PM
Stimulated by a cell-surface signal like binding of a hormone or change of voltage of PM.
Accounts for hormone secretion, neurotransmitter release, mucus secretion, and sometimes ejection of wastes.

47
Q

membrane potential

A

voltage across the membrane.

The voltage is potential energy resulting from the separation of oppositely charged particles

48
Q

resting membrane potential

A

membrane potential of PM that cells exhibit, typically -50mV to -100mV (cells are polarized). The voltage only exists at the membrane - negative just inside the membrane and positive on outside
Main factor of RMP is concentration gradient of K+ and the differential permeability of the PM to K+ and other ions. K+ moves down its concentration gradient (via leakage channels) out of the cell, but then is attracted back by the growing negative charge on the interior of the PM (electrical gradient). Active transport (the Na+K+ pump) maintains this electrochemical gradient. Na+ is less permeable than K+ across the PM
The cell interior is electrically neutral

49
Q

Membrane receptors

A

group of integral proteins and glycoproteins that serve as binding sites and function in contact signaling or chemical signaling (mostly chemical signaling)

50
Q

Contact signaling

A

means by which cells recognize each other. Membrane receptors play a role.
Important for immunity.

51
Q

Chemical Signaling

A

What most plasma membranes proteins are involved with.
Ligands bind to membrane receptors. Different cells can react to the same ligand differently, based on its internal machinery. When a ligand binds to a membrane protein, the protein changes structure (might become activated enzymes, open/close ion gates which then affect membrane potential).

52
Q

G protein-linked receptors

A

membrane protein that is a middle man between extracellular first messengers (like hormones/neurotransmitters) and intercellular second messengers (cyclic AMP or ionic calcium) via an effector enzyme

53
Q

ligand

A

chemicals that bind to membrane proteins.
Examples include: neurotransmitters (nervous system), hormones (endocrine), and paracrines (chemicals that act locally and are rapidly destroyed)

Anatomy & Physiology I (7 decks)

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