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anatomy & physiology I > membrane function, structure and transport > Flashcards

membrane function, structure and transport Flashcards

1
Q

two types of cells

A

sex and somatic

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2
Q

sex cells

A

sperm, egg, germ
- contain 23 chromosomes (1n)
- haploid

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3
Q

somatic cells

A

all other cells in the body (non sex)
- contain 46 chromosomes, 23 pairs (2n)
- diploid (b/c they have pairs)

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4
Q

cytoplasm

A

inside of the cell where the cytosol and organelles reside (two subcomponents

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5
Q

extracellular fluid

A

interstitial fluid (solutes dissolved in it), surrounds the cell

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6
Q

fluid mosaic model of the PM

A
  • fluid because its dynamic and not static; in aq. environment, changes with time
    -mosaic because there are proteins, lipid and carbs embedded within
  • phospholipid bilayer with mosaic proteins scattered throughout
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7
Q

membrane lipids

A
  • mostly from fatty acid tails
  • prevent water soluble molecules from freely passing through the membrane
  • anything lipid soluble can freely pass through
    ie. testesterone, estrogen, fatty acids, alc., cholesterol, small grass, water (special)
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8
Q

membrane proteins

A
  • account for about half of PM
  • results in “mosaic” aspect of PM
  • integral (transmembrane) & peripheral proteins
  • integral = cannot be removed w/o damage to PM
  • peripheral = bound to inner or outer surfaces; easily separated, fewer than integral
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9
Q

membrane carbohydrates

A
  • extend beyond outer surface of PM forming a layer known as the glycocalyx
  • proteoglycans, glycoproteins, glycolipids
  • this helps cells from damaging each other
  • function as lubrication and protection of PM; anchoring & location of cell; specificity in binding; recognition of normal vs abnormal cells
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10
Q

functions of membrane proteins

A
  • anchoring proteins: attach PM to other structures & stabilize structures
  • recognition proteins: help ID normal vs abnormal cells (often glycoproteins)
  • enzymes: catalyze membrane-bound reactions
  • receptor proteins: binds w ligand and triggers changes in cellular activity
  • carrier proteins: binds solutes & transport across PM smaller molecules
  • channels: central pore forms passageway, permits movement of water and small solutes across PM, very specific
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11
Q

function of PM

A
  1. physical isolation - different conditions inside v outside; via phospholipid heads and fatty acid tails
  2. regulation of exchange w environment - controls entry of ions & nutrients, eliminates waste, and releases secretions
  3. sensitivity to environment - contains receptors which allow cell to recognize and respond specific molecules
  4. structural support - specialized connections between PM that gives tissues stability, often via proteins
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12
Q

what type of molecules can simply diffuse across the PM?

A

non-polar, hydrophobic molecules
- soluble in lipids
- can easily pass through or dissolve in
ie. alc., fatty acids, steroids, O2, CO2

PM is selectively permeable and it is dependent on size, electrical charge, shape, lipid solubility

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13
Q

what type of molecules require assistance to get across the PM?

A

polar molecules and ions
- not soluble in lipids, water soluble
ie. sodium potassium pump

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14
Q

what is meant by having a PM that is selectively permeable?

A

regulate what is going in and out of the cell as the proteins and molecules determine what can go through and what cannot

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15
Q

diffusion

A

random movement of molecules moving down the gradient from a high to low concentration
- high solute concentration to low solute concentration to eliminate concentration difference (this is where diffusion stops)

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16
Q

simple diffusion

A

passes through PM; lipid soluble
- alc., fatty acids, steroids, lipid-soluble compounds, dissolved gasses, water

17
Q

channel mediated diffusion

A

requires transmembrane protein channels to pass though PM
- sodium, calcium, potassium, water soluble compounds

18
Q

factors involved in diffusion rate across a cell membrane

A
  1. distance - shorter distance, faster diffusion
  2. molecules size - smaller size, faster diffusion (ie. oxygen vs. sugar)
  3. temperature - higher temp., faster diffusion
  4. gradient size - greater concentration gradient, faster diffusion (diffuses faster b/c greater gradient
  5. electrical forces - like charges repel, opposites attract
19
Q

osmosis

A

special case of diffusion for water that occurs across a selectively permeable membrane that is freely permeable to water, but not freely permeable to solutes
- can always move down the concentration gradient
- will always move down the concentration gradient (high H2O to low H2O)
- eliminates solute concentration differences faster than solute diffusion
- can use aquaporins if it wants

20
Q

carrier mediated transport

A

pumps or transporter
- requires specialized integral membrane proteins w the binding site
- can be passive or active

characteristics (shared w enzyme):
- specificity: each carrier protein binds & transports specific substances
- saturation limits: availability of substrate molecules & carrier proteins limit transport rate (all pumps are filled/working) - when all carrier proteins are = saturation; can not increase despite concentration gradient
- regulation: binding of other molecules (hormones) can effect activity of carrier protein

2 Main Types: facilitated diffusion and active transport

21
Q

facilitated diffusion

A
  • no energy; passive transport requiring protein carrier
  • move substances down the concentration gradient (high to low)
  • substance binds to receptor site on protein –> protein changes shape moving substance across PM (channel is no formed)
  • used to stuff that is insoluble to lipids but to large to pass through transmembrane protein channels
22
Q

active transport

A
  • requires energy (ATP) & protein carrier always
  • move substances against the concentration gradient (low to high)
  • *ATP is hydrolyzing (ATP –> ADP + inorganic phosphate + energy for heat and usable energy)
    ie the Na+ & K+ pump
23
Q

Na+/K+ Exchange Pump

A

pump maintains resting ion levels; need difference in concentration gradient
- Na high in extracellular
- K high in intracellular
Na diffuses into the cell and K diffuses out of cell
Pump maintains homeostasis as ion leak across PM
- take 3 Na from inside to outside
- take 2 K from outside to inside
- 1 ATP is required per 3 Na to 2 K (3:2:1)

these ions are crucial to keep Nervous System and Muscles in line; if they ever equilibrate you will die!

this pump is an example of active transport

24
Q

vesicular transport

A
  • moves materials in or out of a cell in vesicles
  • aka “bulk transport”

2 Main Types: endocytosis and exocytosis

25
Q

endocytosis

A

movement into a cell that requires ATP; packages in vesicles
- receptor-mediated endocytosis: specific (most cells)
- pinocytosis: “cell-drinking” (liquids)
- phagocytosis: “cell-eating” (piece of things - most cell don’t do this)

SA of PM decreases over time if doing this process a lot

26
Q

exocytosis

A

movement out of the cell; reverse of endocytosis
- vesicle created inside of cell –> fuses with PM
- released into ECF
ie secretory or waste products

think of how insulin in created, moves throughout a cell and its organelles, and released out

27
Q

tonicity

A

describes how a solution affects a cell
- osmolarity = solute concentration in aq. solution
1. isotonic
2. hypotonic
3. hypertonic

important as it helps maintain water balance of living cells; is what allows water to freely cross the PM

28
Q

isotonic solution

A

intracellular and extracellular have equal osmolarity
- solute in = solute out
- does not cause net movement in or out of cell

29
Q

hypertonic solution

A

solution has greater solute concentration than cell
- water will leave cell via osmosis leading to shrinking (grenatian) or dehydration
- solute out > solute in
- dehydrated = solute concentration goes up (ECF has high solute concentration)

30
Q

hypotonic solution

A

solution has less solute concentration than cell
- water will enter via osmosis leading to swelling or potential hemolysis (bursting)
- over-hydrated = solute concentration goes up (ECF has high water concentration)

anatomy & physiology I (5 decks)

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