Exam 1- Chapter 6 Flashcards
What does the extracellular environment include?
All constitutes of the body outside of the cells
How much of the total body H20 is in the intracellular environment?
67%
How much of the total body H20 is in the extracellular environment?
33%
How much of the extracellular environment is blood plasma?
20%
How much of the extracellular environment is interstitial fluid?
80%
What is interstitial fluid contained in?
gel like matrix in the extracellular environment (hydrated gel of ground substance)
What are integrins?
glycoprotein adhesion molecules that link intracellular and extracellular compartments
Describe the composition of the extracellular matrix.
- A meshwork of collagen and elastin fibers
- linked to molecules of gel-like ground substance
- substance and to plasma membrane integrins
Plasma membrane is ______ permeable
selectively
What does it mean when we say the plasma membrane is selectively preamble?
allows only certain kinds of molecules to pass
Many important molecules have____ and _____
- Transporters
2. Channels
Describe carrier-mediated transport.
involves specific protein transporters
Describe non-carrier mediated transport.
occurs by diffusion
Passive transport moves compounds _____ concentration gradient.
Down
Does passive transport require energy and transporters?
NO
Active transport moves compounds _____ a concentration gradient
Against
Does active transport require energy and transporters?
YES
Diffusion is a ____ motion of molecules. Net movement is from a region of ____ to ____ concentration.
- Random
- High
- Low
Gas exchange occurs via ____.
Diffusion
What 2 compounds/molecules can diffuse through the cell membrane?
- Non-Polar compounds
2. Small molecules (CO2 and H2O)
Cell membranes are impermeable to _______ and most ______ compounds
- Charged
2. Polar
What must charged molecules have to move across a membrane?
An ion channel or transporter
How many factors does diffusion depend on?
4
What are the 4 factors that diffusion depends on?
- Magnitude of its concentration gradient
- Permeability of membrane to it
- Temperature
- Surface area of membrane
Define osmosis.
Net diffusion of H2O across a selectively permeable membrane
H2O diffuses ____ its concentration gradient
Down
H2O is less concentrated where there are more _____
Solutes
Solutes must be ____ ____ for osmosis to occur.
Osmotically active
What does osmotically active mean?
cannot freely move across membrane
When does osmosis stop?
When H2O has an equal concentration on both sides
Some cells have water channels to facilitate osmosis. What are these water channels called?
aquaporins
What is osmotic pressure?
The force that would have to be exerted to stop osmosis
What does osmotic pressure indicate?
How strongly H2O wants to diffuse
What is osmotic pressure proportional to?
proportional to solute concentration
How is osmotic pressure proportional to solute concentration?
more solute (the higher the solute concentration) the higher the osmotic pressure. (directly proportional)
What is the abbreviation for 1 molar solution?
1.0M
What is the abbreviation for 1 molal solution?
1.0m
What is the problem with using molar when talking about osmosis?
Dosent specify exact amount of H2O
What exactly is 1 molar solution? (what is it dissolved in)
1 mole of solute dissolved in 1L of solution
What exactly is 1 molal solution? (what is it dissolved in)
1 mole of solute dissolved in 1 kg H2O
What is the abbreviation for osmolality?
Osm
What is osmolality (Osm)?
total molality of a solution
What is the osmolality of 1.0m of NaCl? Why?
- 2 Osm
2. Because NaCl dissociates into Na+ and Cl-
What is tonicity?
The effect of a solution on osmotic movement of H2O
What is a isotonic solution?
Solutions have same osmotic pressure
What is a hypertonic solution?
- Solutions have higher osmotic pressure and are osmotically active
- More solute/less water
What is a hypotonic solution? Describe the solute to water ratio.
- Has a lower osmotic pressure
2. Less solute/more water
What is a isomotic solution?
solutions have same osmolality as plasma
What is a hyper-osmotic solution?
have higher pressure than plasma
What is a hypo-osmotic solution?
solutions have lower osmotic pressure than plasma
If a blood cell is placed in a hypotonic solution what will happen?
It will expand and possibly burst due to H2O coming in
If a blood cell is placed in a hypertonic solution what will happen?
It will shrink due to H2O leaving
Describe why a blood cell in a hypotonic solution will expand and possibly burst.
Since the osmotic pressure is lower in a hypotonic solution (less solute/more water), water will enter the blood cell to make the concentration of water equal.
Describe why a blood cell in a hypertonic solution will shrink.
Since the osmotic pressure is higher in a hypertonic solution (more solute/less water), water will leave the blood cell to make the concentration of water equal.
What is the narrow range that blood osmolality is maintained at?
300mOsm
If dehydration occurs ______ in the _____ stimulate ____ release.
- Osmoreceptors
- Hypothalamus
- ADH
What does the release of ADH cause?
Causes kidney to conserve H2O and causes thirst.
What types of molecules is carrier mediated transport needed for? What are these molecules transported by?
- Molecules too large and polar to diffuse
2. Transported across membrane via PROTEIN CARRIERS
How many features do protein carriers exhibit?
3
What are the 3 features protein carriers exhibit?
- Specificity
- Competition
- Saturation
Describe specificity when talking about protein carriers.
Specificity for a single molecule
Describe competition when talking about protein carriers.
Competition among substrates for transport
Describe saturation when talking about protein carriers.
When all carriers are occupied (Transport maximum/Tm)
What is it called when saturation occurs with proteins carriers?
Transport maximum (Tm)
What is facilitated diffusion?
Passive transport down concentration gradient by carrier proteins
What is an active transport pump?
Transport of molecules against a concentration gradient
What two things are required to achieve an active transport pump?
- ATP
2. Carrier protein
Primary active transport relies ____ on ATP
directly
Secondary active transport relies _____ on ATP
indirectly
What is an example of primary active transport?
Na+/K+ Pump
The Na+/K+ Pump uses ATP to move _ Na+ ___ and _ K+ ___.
- 3
- Out
- 2
- In
The Na+/K+ Pump works _____ the concentration gradient
against
How does the Na+/K+ Pump rely on ATP?
Directly
How does secondary active transport get its energy?
Relies on the ATP created by the Na+ going BACK into the cell DOWN its concentration gradient AFTER primary active transport has been achieved
Secondary active transport is going ____ its concentration gradient.
against
Primary active transport is going ____ its concentration gradient.
against
What is another name for cotransport?
symport
What is another name for countertransport?
antiport
What is cotransport (symport)?
secondary transport in the same direction as Na+
What is countertransport (antiport)?
moves molecule in opposite direction to Na+
What is absorption?
is transport of digestion products across intestinal epithelium into blood
What is reabsorption?
transports compounds out of urinary filtrate back into blood
What is transcellular transport ?
moves material from 1 side to other of epithelial cells
What is paracellular transport ?
moves material through tiny spaces between epithelial cells
When discussing transport across epithelial membranes, what limits transportation between cells?
junctional complexes
What is the function of junctional complexes?
connect adjacent epithelial cells
Plasma membranes can join together to form ______
tight junctions
What are the 3 types of junctional complexes?
- Tight junctions
- Adherens junctions
- Desmosomes
Describe adherens junctions.
membranes are “glued” together by proteins that pass through both membranes and attach to cytoskeletons
Describe desmosomes?
proteins “button” two membranes together
What is the function of bulk transport, and what does it occur by?
- Moves large molecules and particles across plasma membrane (multiple at a time)
- Occurs by endocytosis and exocytosis
What is membrane potential?
Is difference in charge across membranes
What is membrane potential a result from/how does it work specifically?
- Results in part from presence of large anions being trapped inside cell
- Diffusable cations such as K+ are attracted into cell by anions
- Na+ is not permeable and is actively transported out
What is the equilibrium potential?
Describes voltage across cell membrane if only 1 ion could diffuse
What is the charge on the inside of a cell?
negative charge of about -90mV
If membrane permeable only to K+, it would diffuse until it reaches its __________
equilibrium potential
K+ is attracted inside by trapped anions but also driven out by its __________
concentration gradient
At K+ equilibrium, electrical and diffusion forces are_____ and _____
- Equal
2. Opposite
What is the function of the Nernst Equation (Ex)?
Gives membrane voltage needed to counteract concentration forces acting on an ion
What is the Nernst Equation (Ex)?
Ex = 61 log [Xout]
z [Xin]
What is the RMP of most cells?
–65 to –85 mV
What is the RMP?
membrane voltage of cell not producing impulses
What does the RMP depend on?
- Concentrations of ions inside and out
2. permeability of each ion
What is RMP affected by the most?
Affected most by K+ because it is most permeable.
Why is the RMP less than Ek+?
Some Na+ diffuses in so RMP is less negative than EK+
What is the role of Na+/K+ Pumps in RMP?
- Because 3 Na+ are pumped out for every 2 K+ taken in, pump is electrogenic
- It adds about –3mV to RMP
What is cell signaling?
How cells communicate with each other
Some cells use _______ thru which signals pass directly from 1 cell to next.
gap junctions
To respond to a chemical signal, a target cell must have a _____ for it.
receptor protein
How does paracrine signaling work?
cells secrete regulatory molecules that diffuse to nearby target cells
How does synaptic signaling work?
1 neuron sends neurotransmitter messages to another cell via synapses
How does endocrine signaling work?
cells secrete chemical regulators that move thru blood stream to distant target cells
How do nonpolar regulatory molecules affect their target cell?
Pass DIRECTLY through plasma membrane, bind to receptors in the nucleus, and affect transcription.
Give 3 examples of non polar regulatory molecules in terms of target cells.
- Steroid hormones
- Thryroid hormones
- Nitric oxide
How do polar regulatory molecules affect their target cell?
- Bind to cell surface receptors
2. Activated receptors send second messengers into cytoplasm to mediate actions of regulatory molecule
What can second messengers be?
May be ions (e.g. Ca++) or other molecules such as cyclic AMP (cAMP) or G-proteins
How many subunits do g-proteins have?
3
When a cell surface receptor is activated what happens to g-proteins?
subunits disassociate
After the g-proteins subunits disassociate what happens next?
subunit binds to an ion channel or enzyme, changing their activity
What parts of the g-protein subunits disassociate?
Alpha disassociates from the other 2
Describe the cycle g-proteins play in polar regulator molecules and target cells.
- Unstimulated state: subunits are all in tact
- Regulatory molecule binds to surface receptor: alpha takes IN GTP/releases GDP
- Alpha disassociates
- Alpha binds to effector OR beta-gamma binds to effector
- Subunits become back intact when reverted to unstimulated state.
Tight junctions are _____ proof.
Leak
