3. Chapter 5- Cell Membrane 2

Question 1

What are the two body fluid compartments?

What is the one further divided into?

Answer 1

Cells (intracellular fluid, ICF)
Extracellular Fluid (ECF)

ECF is divided into blood plasma and interstitial fluid

Question 2

What is interstitial fluid?

Answer 2

Lies between the circulatory system and the cells

Slide 3 on sept 12

Question 3

What rough percent of the body is water?

How many litres is intracellular fluid? What about extracellular?

Answer 3

Roughly 60% of the body is water 
1L ~ 1kg
Average male 70kg, 42kg is water 
28L is intracellular fluid
14L is extracellular (25% plasma, 75% interstitial fluid)

Question 4

How does your overall body water content percentage move as you get older?

Answer 4

Your body water percentage decreases over time which is a result of loss of muscle mass among others

Question 5

What is adipose tissues content of water compared to skeletal muscles content of water?

Answer 5

Adipose tissue- 90% lipids, majority TGs, small fraction water
Skeletal tissue- 75% water and 18% protein

Question 6

What are the 3 things that can alter water content in the body?

Answer 6

Age
Sex
Body fat composition

Question 7

What is osmosis?

What way does water move in osmosis?

Answer 7

The movement of water across a membrane in response to a solute concentration gradient

Water moves from a region of low solute concentration to a region of high solute concentration

Question 8

Does osmotic equilibrium mean chemical or electrical equilibrium?

Answer 8

No since each the intracellular fluid and the extracellular fluid have different amount of charged elements so the body compartments are in a state of chemical disequilibrium
Slide 8 sept 12

Question 9

What is osmotic pressure?

Answer 9

The pressure that must be applied to a solution that increased volume to do osmosis in order to oppose osmosis
Osmotic pressure prevents osmosis
Slide 9 sept 12

Question 10

What is osmolarity?
What are it’s units?
How do you use molarity and osmolarity in equations?

Answer 10

Describes the number of particles in a solution
This is not molarity since osmolarity is the number of dissolved particles in a solution while molarity is the number of particles in the solution period

osmol/L or mOsm/L

Example on slide 10 of sept 12

Question 11

What does isosmotic, hyperosmotic, and hyposmotic mean in osmolarity?

Answer 11

Isosmotic- solutions have identical osmolarities
Hyperosmotic- describes a solution with greater osmolarity (greater than)
Hyposmotic- describes a solution with the lower osmolarity (less than)

Question 12

What is tonicity?

What are the three types?

Answer 12

Tonicity is a term used to describe a solution and how that solution would affect cell volume of a cell were placed in the solution and allowed to come to equilibrium
Isotonic, hypertonic, hypotonic

Question 13

What does isotonic, hypertonic, and hypotonic mean in tonicity?

Answer 13

Isotonic solution- same amount of water leaves the cell as the amount that goes in
Hypertonic solution- more water enters the cell than water that leaves causing it to swell
Hypotonic solution- more water leaves the cell than water that enters causing it to shrivel

Question 14

What are the 3 differences between osmolarity and tonicity?

Answer 14

1. Osmolarity describes number of solute particles dissolved in a solution and can be measured while tonicity has no units
2. Osmolarity can be used to compare two solutions, tonicity compares a solution and a cell
3. Osmolarity does not tell you what happens to a cell placed in solution, tonicity tell you what happens to cell volume when placed in a solution
   EXAMPLE ON SLIDE 14 and 15 sept 12
   And slide 17!!

Question 15

What does tonicity depend on?

Answer 15

The concentration non-penetrating solutes

Basically when the cell enters solution tonicity comes in but when the cell is out of solution and you’re comparing it’s osmolarity

Question 16

What is the tonicity and osmolarity when the cell and solution have 3 non penetrating solution on each side? (Slide 16 sept 12)

Answer 16

Tonicity- isotonic

Osmolarity- isosmotic

Question 17

What is the tonicity and osmolarity when the cell has 3 non penetrating solution and the solution has 1 non penetrating solution and 2 penetrating solution? (Slide 16 sept 12)

Answer 17

Tonicity- hypotonic solution (water goes into cell and it swells since the solution has less non penetrating solution)
Osmolarity- isosmotic since they have same number of molecules

Question 18

What is the tonicity and osmolarity when the cell has 3 non penetrating solution and the solution has 3 non penetrating solution and 2 penetrating solution? (Slide 16 sept 12)

Answer 18

Tonicity- isotonic

Osmolarity- hyperosmotic solution since it has more molecules than cell

Question 19

What is osmolarity compared to osmolality?

Answer 19

Osmolarity- osmoles per litre of solution
Osmolality- osmoles per kg of solvent
In small concentrations they are nearly identical
Osmolarity is used when temp and pressure are constant since changes in temp and pressure can change volume not mass and osmolality is mass

Question 20

What is diffusion?

Answer 20

The movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached
Opposite of osmosis
Uses kinetic energy of molecular movement and does not require outside energy

Question 21

What does membrane permeability depend on?

Answer 21

The molecules lipid solubility
The molecules size
The lipid composition of membrane

Question 22

What is Ficks law of diffusion?

Answer 22

The rate of diffusion is proportional to the surface area, concentration gradient, and membrane permeability

Membrane permeability is proportional to lipid solubility and inversely proportional to molecular size

Question 23

What are channel proteins?

What type of channel protein is aquaporin?

Answer 23

Made of membrane spanning proteins that create cluster of cylinders with pore through the center (slide 7 sept 14)
Mainly smaller substances pass through like ions and water
Open channels are called leak channels, aquaporin is a leak channel
There can be gated channels too

Question 24

What are carrier proteins?

Answer 24

Proteins that change conformation to move molecules very slow
Binding of molecule is what start conformational change

Question 25

What is facilitated diffusion?

Answer 25

Where a carrier or channel is used to make simple diffusion for molecules that cannot simply diffuse across the membrane based on their chemical properties

Question 26

What is active transport?

What are the two types?

Answer 26

Moves molecules against their concentration gradients from low conc to high conc
Requires energy and uses carrier proteins
Primary AT- energy for it comes directly from hydrolyzing ATP (3Na out, 2K in)
Secondary AT- uses potential energy stored in concentration gradient of one molecule to push another molecule across their concentration gradient

Question 27

What is specificity, competition, and saturation?

Answer 27

Specificity- ability of a transporter to move a molecule (which structures it can transport)
Competition- Carrie meat move several members of substances but they compete with one another (may have preference for one family member)
Saturation- rate of transport depends on concentration and number of transporters (goes till maximum transport is reached)

Question 28

What are the three methods of vesicular transport for larger macromolecules?

Answer 28

Phagocytosis- creates absorbing vesicles using ATP using the cytoskeleton in a phagocyte
Endocytosis- requires ATP makes smaller vesicles indents the membrane (non selective pinocytosis and selective receptor mediated transport)
Exocytosis- requires ATP pushes wastes and such out of the cell by pushing a transport vesicles to the membrane and out

Reviews slides 16-18 on sept 14

Question 29

What is epithelial transport?

Answer 29

Epithelial cells are cells that line organs and separate them from the extracellular fluid (Skin kidneys etc)
Substances entering and exiting the body or organs must move across the layer of epithelial cells
ECF to lumen is secretion, Lumen to ECF is absorption
Apical surface is outside the epithial cells facing into organ
Basolateral is outside surface of epithelial cells facing towards ECF

Question 30

What are the 3 types of epithelial transport?

Answer 30

Transcellular- across epithelial cell
Paracellular- between the tight junctions between epithelial cells
Transcytosis- macromolecules are transported across the interior of a cell (capture din vesicles on one side of the cell then transported and released other side)

Transcellular and transcytosis require energy

Question 31

What is the resting membrane potential and it’s major cations and anions?

Answer 31

The body as a whole is electrically neutral, for every cation there is an anion
Major cations: 
intracellular K+
Extracellular Na+
Major anions:
Intracellular phosphate ions, proteins
Extracellular Cl-

Question 32

What are the overall charges in the intracellular fluid and extracellular?

Answer 32

Intracellular- slight excess of anions (-)
Extracellular- alight excess of cations (+)

Diagram on slide 11 sept 17

Question 33

What are conductors and insulators?

Answer 33

Conductor- material where positive and negative charges can move towards eachother (water or wire)
Insulator- material separating charges (membrane)

Question 34

What is the membrane potential and it’s symbol?

Answer 34

The electrical disequilibrium that exists between the ECF and ICF
Vm

Question 35

What is the equilibrium potential?

What is it’s equation to find it?

Answer 35

For any given concentration gradient of a single ion, the membrane potential that exactly opposes the concentration gradient is the equilibrium potential

Eion or Ek or ENa for example
Ek=RT/ZF ln[K+] outside / [K+] inside

Question 36

What is the resting membrane potential?

What maintains it?

Answer 36

The membrane potential of a cell when it is not active
Only so much cations can leave the cell before they are drawn back in creating an equilibrium
Cell membrane is 40 times more permeable to K+ so K+ decides the resting membrane potential

Maintained by Na-K ATPase sets up concentration gradients thag determines membrane potential (3Na+ out/ 2K+ in)

Question 37

Two factors that influence the cell membranes potential?

What is depolarization, hyperpolarization, and repolarization?

Answer 37

1. Concentration gradients of different ions across the membrane (Na+, K+, Cl-, Ca2+)
2. The permeability of the membrane to those ions

Depolarization- potential becomes less negative than the resting potential
Hyoerpolarization- potential becomes more negative than the resting potential
Repolarization- going back to the membrane potential

Question 38

What is normokalemia, hyperkalemia, and hypokalemia?

Answer 38

Normokalemia- when blood K+ is in the normal range
Hyperkalemia- increases blood K+ concentration brings the membrane closer to the threshold
Hypokalemia- decreases Blood K+ concentration, hyperpolarizes the membrane

Slide 5 sept 19