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BIOPHYSICS > LECTURE 5 (Membrane transport) > Flashcards

LECTURE 5 (Membrane transport) Flashcards

1
Q

What influences the internal concentrations of the molecules?

A

The movement of materials into and out of cells

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2
Q

Why are some transport mechanise considered “passive/inactive”?

A

Since the compounds move without requiring the expenditure of cellular energy, the force moving these molecules or ions is not external to them. It comes fro kinetic energy the particles already have.

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3
Q

What is absolute zero?

A

-213.16 degrees Celsius

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4
Q

Why is do molecules move from higher concentration to lower concentration?

A

The higher the concentration of molecules in the area -> The higher the total energy (some of kinetic energies) -> probability of molecules to a lower concentration is higher

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5
Q

What are the different types of Passive transport?

A
  • Simple diffusion
  • Facilitated diffusion
  • Osmosis
  • Filtration
    [uses hydrostatic pressure instead of kinetic energy]
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6
Q

What is Diffusion?

A

The movement of molecules from a higher concentration to a lower concentration

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7
Q

What is Fick’s law and what does it state?

A

Law of diffusion that states that molecules move from a higher to lower concentration

EQUATION:
- Increase concentration gradient -> diffusion increases
- Increase cross-sectional area -> diffusion increases
- Decrease thickness of membrane -> diffusion increases

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8
Q

What is Gay Lussac’s law?

A

States that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature

Heat the gas -> give the molecules more energy -> move faster -> more impacts on the walls of the container and an increase in pressure

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9
Q

What factors influence the rate of diffusion?

A
  • Temperature
  • State of solvent (solid, liquid, gas)
  • Size of molecules (smaller molecules -> faster diffusion)
  • Diffusion gradient (larger gradient -> faster diffusion)
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10
Q

What is Osmosis?

A

The movement of water molecules from a higher concentration to a lower concentration across a semi-permeable membrane

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11
Q

What is Osmotic pressure?

A

The hydrostatic pressure which is needed to block osmosis and determines the ability of a system to get the required amount of water by the way of Osmosis

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12
Q

What is the unit of Osmotic pressure?

A

The mechanical pressure (Hydrostatic pressure) which is responsible to equalise osmotic pressure and balance the flow of solution in both directions

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13
Q

What is the equation of Jet Flow?

A

J=L S [Δπ]

J = Jet flow during Osmosis
L = Hydrostatic penetration of the membrane
S = Surface area of membrane
Δπ = Osmotic pressure
[dependent on the concentration gradient of the dissolved compounds ΔC]

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14
Q

What is Osmolarity?

A

The concentration of a solution determined by the number of dissolves particles per kg of water

[concentration in solution]

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15
Q

What is the equation to calculate Osmolarity?

A

Osmolarity = Eφi ni Ci

φ = Osmotic coefficient
[depends on the degree of dissociation of the dissolved substance]
n = The quantity of the ionic particles which are made after the dissociation of molecules
C = molar concentration of dissolved substance
I = dissolved substances

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16
Q

As osmolarity of a solution increases, osmotic pressure of the same solution __________

A

increases

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17
Q

What is the difference between Osmosis of water and Diffusion of water?

A

Osmosis occurs because of a PRESSURE DIFFERENCE whereas diffusion occurs because of a CONCENTRATION DIFFERENCE of water

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18
Q

What is required to calculate Osmolarity?

A
  • Concentration of solute
  • Whether solute dissociates in solution
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19
Q

What is the difference between Osmolarity and Molarity?

A

Osmolarity is distinct from Molarity because it measures osmoses of solute particles rather than moles of solute -> Distinction arises because some compounds can dissociate in solution whereas others cannot

[NaCl dissociates into Na+ and Cl- so 1 mol of NaCl is 2 osmol since there’s two particles it dissociates into]

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20
Q

____-________ compounds do not dissociate so form only 1 ormolu of solute per 1 mole of solute

A

Non-ionic

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21
Q

What is Isotonic, Hypertonic and Hypotonic?

A

Isotonic = A solution that has the same osmotic pressure as body fluids

Hypertonic = Osmotic pressure greater than body fluids

Hypotonic = Osmotic pressure less than body fluids

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22
Q

How is the molar concentration determined?

A

By dividing the number of grams of solute used to make the solution by the molecular weight of the solute

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23
Q

What is Van’t Hoff’s factor?

A

A measure of the number of ions a solute will form when dissolved in water

24
Q

What is Van’t Hoff’s equation?

A

Calculates OSMOTIC PRESSURE

π = g C σ R T

π = Reflection coefficient
g = Number of particles per mole in solution
C = Concentration
σ = Reflection coefficient
R = Gas constant
T = Temperature

25
Q

What is σ ?

A

σ is the Reflection coefficient which is a dimensionless number ranging between 0 and 1 that describes the ease with which a solute crosses a membrane

σ = 1.0 -> effective osmotic pressure will be maximal and will cause maximal water flow

σ = 0 -> no effective osmotic pressure difference so no driving force for osmotic water flow

σ = 0-1 -> effective osmotic pressure lied between its maximal possible value and zero

26
Q

What is Filtration?

A

Fluid transmembrane relocation by membrane pores and by influence of hydrostatic pressure. Hydrostatic pressure gradients are necessary for filtration.

27
Q

What does Osmotic pressure equal?

A

The sum of osmotic pressure of all substances soluted in the blood plasma

28
Q

What is the function of Hydrostatic pressure?

A

Ensure small molecules and fluid movement from vessels into interstitial fluid through pores formed between endothelial cells

29
Q

What is Oncotic pressure/Colloid osmotic pressure?

A

A form of osmotic pressure exerted by proteins in blood plasma that tends to pull water into the circulatory system -> It provides reabsorption which prevents too much fluid from leaving capillaries

30
Q

What are the four primary forces that determine fluid movement through the capillary membrane?

A
  • CAPILLARY HYDROSTATIC PRESSURE (Pc) = force fluid outward through capillary membrane
  • INTERSTITIAL FLUID HYDROSTATIC PRESSURE (Pi) = in interstitial fluid which forces fluid either outward (+)/inward (-) through capillary membrane
  • BLOOD PLASMA COLLOID OSMOTIC PRESSURE (πc) = fluid inward
  • INTERSTITIAL FLUID COLLOID OSMOTIC PRESSURE (πi) = osmosis of fluid outward
31
Q

What is the Ultrafiltration law?

A

Fluid Movement = K (Pc + πi - Pi + πc)

FM = Filtration coefficient (outward + inward)

32
Q

What is the lymphatic system composed of?

A
  • Lymphatic capillaries
  • Lymphatic vessels
  • Lymph nodes
  • Lymphatic organs (e.g spleen and thymus)
33
Q

What effect does Hypotension due to heart total failure cause in the body?

A

Decrease in salts and water excretion in kidneys -> volume, hydrostatic pressure and filtration intensity in capillaries -> Development of swelling

34
Q

What is the meaning of Endogenic and Exogamy carriers?

A

Endogenic = proteins synthesised on ribosomes

Exogamy = non-ribosomal translated proteins

35
Q

What are the Endogenic carriers of facilitated passive transport?

A
  • Glucose carrier GLUT-1
  • Aquaporins
  • K+, Na+ and Ca2+ channels
36
Q

What are the Exogamic carriers of facilitated passive transport?

A
  • Valinomicine
  • Gramicidine A
37
Q

Describe Glucose transport in erythrocytes

A

Glucose transport is carried out by GLUT-1 which binds glucose from extracellular area and transports and releases glucose molecules on both sides of erythrocyte membrane in cell cytoplasm -> Glucose is moved via FACILITATED DIFFUSION since conc is higher extracellularly -> Glucose undergoes glycolysis for energy

38
Q

What are Glucose transporters?

A
  • Integral membrane proteins that contain 12 membrane-spanning helices with both the amino and carboxyl termini exposed on the cytoplasmic side of the plasma membrane
  • Transport glucose/hexoses across membrane
39
Q

Describe GLUT-1

A
  • Highest levels in erythrocytes and endothelial cells of barrier tissues
  • Responsible for low level of BASAL GLUCOSE UPTAKE required for respiration
40
Q

Describe GLUT-2

A
  • Allows glucose to flow in 2 directions
  • Found in renal tubular cells, liver cells and pancreatic beta cells
  • Found in basolateral membrane of small intestine epithelium
  • Transports glucose, galactose and fructose from intestinal mucosa to portal circulation
41
Q

Describe GLUT-3

A

Expressed mostly in neurons and placenta

42
Q

Describe GLUT-4

A

Found in adipose tissue and striated muscle

43
Q

What is the rate of substrate transport (facilitated active transport) dependent on?

A
  • Concentration gradient
  • Number of carrier molecules
  • Rate
  • Affinity of transport molecules towards substrate molecule
44
Q

What is the maximum rate of reaction (Vmax)?

A

The rate of reaction when the enzyme is saturated with the substrate

45
Q

What is Km?

A

The concentration of substrate which allows the enzyme to achieve half Vmax

[an enzyme with a high Km has a low affinity for its substrate and requires a greater concentration of substrate to achieve Vmax]

46
Q

What is the difference between an enzyme with a low Km and high Km?

A

An enzyme with a low Km = normally saturated with substrate and will act more or less constant rate, regardless of variations in the concentration of substrate

An enzyme with a high Km = not normally saturated with substrate, activity varies as concentration of substrate varies
[rate of formation of product will depend on availability of substrate]

47
Q

How do you determine Km and Vmax?

A

1) Incubate enzyme with varying concentrations of the substrate
2) Plot results on graph with rate of reaction against concentration of substrate
3) It will yield hyperbolic curve or use MICHAELIS-MENTEN EQUATION
v = Vmax/(1+(Km/[S]))
v is rate of reaction

48
Q

What are Aquaporins?

A

Integral membrane proteins in the cell membrane that regulate the flow of water

[Endogenic]

49
Q

What are the characteristics of Aquaporins?

A
  • Six transmembrane helices joined together with amino and carboxylic terminals on cytoplasmic side
  • Found in all life forms
  • Allow efficient permeation of water
  • High specificity for water
  • Highly conserved
50
Q

What is significant about sodium ion channels?

A

Inner surfaces are strongly negatively charged -> -ve charge can pull small dehydrated sodium ions into the channels away from they hydrating water molecules

51
Q

What are the two major classes of sodium channels in mammals?

A
  • Voltage-gated sodium channel (found throughout body)
  • Epithelium sodium channel (found in skin and kidneys)
52
Q

What are the two gates that Voltage-gated sodium channels have?

A
  • Activating gate that is voltage-dependent
  • Inactivating gate that is time-dependent
53
Q

What is the difference between gated and non-gated potassium channels?

A

Non-gated = always open and transport potassium independent of condition of cell

gated = “closed” during resting state and “open” when membrane is excited

54
Q

What are the two types of Exogamic (non-ribosomal translated proteins) carriers?

A
  • Mobile carriers = diffuse into membrane together with ions
  • Fixed carriers = channels in the membrane and across of them ions are diffused
55
Q

What is an example of a Mobile exogamic carrier?

A

Valinomycin (an antibiotic)

PROPERTIES:
- binds K+ ions and facilitates their transfer across lipid bilayers
- antibiotic
- can induce apoptosis

56
Q

What is an example of a Fixed exogamic carrier?

A

Gramicidin A

PROPERTIES:
- peptide antibiotic
- disrupts transmembrane ion concentration gradient by forming an ion channel in a lipid bilayer -> K+ ions passive transport -> cell death

57
Q
A

BIOPHYSICS (15 decks)

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