2 Types of cell membrane transport Factors affecting transportCell membraneChemical gradientElectrical gradientRate of transportPassive transportDiffusionOsmosisFacilitated diffusionActive transportPumpsphagocytosisEndocytosis/exocytosis
3 Factors affecting transport: cell membrane The cell needs to absorb and excrete various compounds throughout its life.These compounds need to pass through the membrane which is made from a phospholipid bilayerThe phospholipid bilayer is formed by phospholipid molecules bipolar molecule: the fatty acid side is hydrophobic, the phosphoric side is hydrophilic
4 The membrane is impermeable to: The membrane is permeable to: Small, charged molecules“large molecules” such as amino acids, glucose and largerThese compounds must go through channels present in the membrane in order to enter or exit the cellH2OGases (O2, CO2, N2)LipidsSmall, neutral molecules (such as urea)
5 Factors affecting transport: Chemical gradient Compound moves from an area of high concentration to low concentration (or concentration gradient)All compounds permeable to the phospholipid bilayer will move this way
6 Factors affecting transport: Electrical force Positive ions are attracted to negative ions and vice versaIons are repelled by ions of the same charge (+ against + and – against -)
7 Movement across the cell membrane Both chemical and electrical forces (electrochemical force) drive the movement of compounds across the cell membrane
8 Factors affecting the rate of transport The rate of transport will depend on:The concentration gradientThe compound permeability to the membraneThe type and number of charges present on the compound
9 Crossing of cell membrane fats and oils can pass directly throughlipidinside cellsatwastesugaraaH2Ooutside cell
10 Types of Transport Proteins Channel proteins are embedded in the cell membrane & have a pore for materials to crossCarrier proteins can change shape to move material from one side of the membrane to the other
11 Cell membrane channels Need to make “doors” through membraneprotein channels allow substances in & outspecific channels allow specific material in & outH2O channel, salt channel, sugar channel, etc.inside celloutside cell
12 Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membraneHIGHLOW
13 Passive transportCompounds will move from area of high concentration toward area of lower concentrationNo ATP is needed for this type of transportPassive transport mainly TWO typesA-OsmosisB-Diffusion-diffusion again two typesa-simple diffusion- no energy neededb- facilitated diffusion- no energy needed-help through a protein channel
14 Osmosis Each compound obeys the law of diffusion diffusion of water from HIGH concentration of water to LOW concentration of wateracross a semi-permeable membraneHowever, some compounds are unable to cross the cell membrane (glucose, electrolytes…)Water can cross will enter or exit the cell depending its concentration gradient.
17 NO NET MOVEMENT OF H2O (equal amounts entering & leaving) PLASMOLYSISIsotonic SolutionHypotonic SolutionHypertonic SolutionNO NET MOVEMENT OF H2O (equal amounts entering & leaving)CYTOLYSISPLASMOLYSIS
18 Diffusion Simple diffusion- no energy needed Movement across higher to lower concentration gradient.Facilitated diffusion-Some compounds are unable to diffuse through the membrane.They will be allow to cross if the membrane has proteins that can bind these compounds and enable to cross toward the area of lower concentration
20 Simple Diffusion Doesn’t require energy Moves high to low concentrationExample: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.
21 Simple DiffusionThe rate of diffusion will be increased when there is :Concentration: the difference in between two areas (the gradient) causes diffusion. The greater the difference in concentration, the faster the diffusion.Molecular size: smaller substances diffuse more quickly. Large molecules (such as starches and proteins) simply cannot diffuse through.Shape of Ion/Molecule: a substance’s shape may prevent it from diffusing rapidly, where others may have a shape that aids their diffusion.Viscosity of the Medium: the lower the viscosity, the more slowly molecules can move through it.
22 Movement of the Medium: currents will aid diffusion Movement of the Medium: currents will aid diffusion. Like the wind in air, cytoplasmic steaming (constant movement of the cytoplasm) will aid diffusion in the cell.Solubility: lipid - soluble molecules will dissolve through the phospholipid bilayer easily, as will gases like CO2 and O2.Polarity: water will diffuse, but because of its polarity, it will not pass through the non-polar phospholipids. Instead, water passes though specialized protein ion channels
23 Facilitated diffusion Doesn’t require energyUses transport proteins to move high to low concentrationExamples: Glucose or amino acids moving from blood into a cell.
26 Active Transport - Pumps - phagocytosis - Endocytosis/exocytosis
27 Active transport ATP (energy) is needed pump Moves materials from LOW to HIGH concentrationAGAINST concentration gradient
28 Example-1 ATPase pumpsThe most common: Na/K pumps reestablish membrane potential. Present in all cells.Two K+ ions are exchanged with 3 Na + ions
29 EXAMPLES OF ACTIVE TRANSPORT Example 2: the thyroid gland accumulates iodine as it is needed to manufacture the hormone thyroxin.The iodine concentration can be as much as 25 times more concentrated in the thyroid than in blood.
30 Example 3: In order to make ATP in the mitochondria, a proton pump (hydrogen ion) is required.
32 Endocytosis Endocytosis: (“Endo” means “in”). Endocytosis is the taking in of molecules or particles by invagination of the cell membrane forming a vesicle. Integrity of plasma membrane is maintained.This requires energy.Endocytosis is fallowed by exocytosis on the other side. – Transcytosis, vesicle trafficking, or cytopempsis.
33 Types of endocytosis 1. pinocytosis (cell drinking): small molecules are ingested and a vesicle is immediately formed. This is seen in small intestine cells (villi)2. phagocytosis (cell eating): large particles, (visible with light microscope) are invaginated into the cell (ie: white blood cells ‘eat’ bacteria
35 PhagocytosisUsed to engulf large particles such as food, bacteria, etc. into vesiclesCalled “Cell Eating
36 Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)
37 Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.
38 Exocytosis Exocytosis: (“Exo” means “out”.) Exocytosis is the reverse of endocytosis.This is where a cell releases the contents of a vesicle outside of the cell.These contents may be wastes, proteins, hormones, or some other product for secretion.This also requires energy.Example: vesicles from the Golgi fuse with the plasma membrane and the proteins are released outside of the cell.
40 Fusion of vesicle with plasma membrane is mediated by a number of accessory proteins- SNARE protein. Require stimulus and Ca.Exception- Renin from JG cells and PTH from parathyroid gland by decrease in intracellular Ca.Constitutive Secretion- Immunoglobulin from plasma Cells and collagen from fibroblast.Regulated- endocrine gland, pancreatic acinar cells
41 Membrane Transport Proteins 1. Water Channels or Aquaporins (AQPs) –12 typesAmount of water is regulated by No. of AQPsThey are known as gated channel althoughthey are pores.Two types a) Aquaporins- only water.b) Aquaglyceroporins- also forsmall molecules.
42 2- Ion Channels-All cells specially on excitable cells – Neurons and muscle cellsSelective and non selectiveGated – voltage gated and extracellular agonist or antagonist gated ex – acetylcholine gated cationic specific channel at motor end plate of skeletal muscle.Conductance- 1-2 picosimens and > 100 picosimens.Ex- Na, K, Ca, Cl, Anion , cation.
43 3.Solute Carriers- > 40 types , > 300 transporters. three gps-1. Uniporters- single molecule across the membrane (GLUT )2. Symporters- Two or more moleculesEx- Na-k-cl Symporter (Kidney)Na - Glucose Cotransporter.3. Antiporters- Two or more molecules inopposite directionsEx :Na- H antiporter ( PH regulation)3Na- Ca , Cl- HCO3
44 4.ATP DEPENDENT TRANSPORTERS 1. ATPase Ion Transporters1. P- Type- gate phosphorylted duringtransport. Na- K ATP ase.2. V- Type- Vacuolar H- ATPase – urineacidification on Vacules like endosomesand lysosomes.2. ATP – binding cassette (ABC) transporters – 7 subgroups transport diverse group of ions ex- Cl, Cholesterol, bile acids, drugs, iron and organic anions.EX:- Cystic fibrosis transmembrane regulator.Multidrug Resistance Protein.organic Anions..
45 Molecular Motors:Kinesin- over the microtubuleDynein- retrogate transportMyosin- over the microfilaments.- 18 types a
46 Q-1 all membrane processes, such as pumping and channelling of molecules are carried out by. a-lipidb-carbohydratec-nucleic acidd-proteinAns- d Difficulty Index- Pre Lecture- 54 % Post Lecture- 100%
47 Q-2 Which of the following statement about membrane transport protein is incorrect a-carrier proteins are similar to enzymes in that they show saturation b-carrier protein can facilitate both active and passive transport c-channel protein can facilitate both active and passive transport d-the Na+ /Glucose transport protein carries out secondary active transport.Ans- C Difficulty Index- Pre Lecture- 55 % Post Lecture- 96%
48 Q-3 Diffusion across the plasma membrane is more rapid if a substance is a-a protein b-hydrophilic c-high in its oil : water partition coefficient d-larger and globular in shapeAns- C Difficulty Index- Pre Lecture- 49 % Post Lecture- 87%
49 Q-4 the difference between simple diffusion and facilitated transport is that facilitated transport. a-is concentration dependent b-occurs across plasma membrane c-require membrane protein d-utilize a substance moving with its concentration gradientAns- C Difficulty Index- Pre Lecture- 25 % Post Lecture- 98%
50 Q-5 Erythrocyte glucose transporter specifically transports glucose down its concentration gradient and exhibit hyperbolic saturation kinetics .This is an example of a-active mediated transport b-passive mediated transport c-non- mediated transport d-group translocationAns- b Difficulty Index- Pre Lecture- 14 % Post Lecture- 76%
51 Q-6 which one of the following is a correct statement for Na-K ATPase Q-6 which one of the following is a correct statement for Na-K ATPase. a-it gives out 3 Na-ions and takes in 2 K-ions b- it gives out 2 Na-ions and takes in 3 K-ions c- it gives out 3 Ca-ions and takes in 2 K-ions d-it gives out 3 Na-ions and takes in 2 Ca-ionsAns- a Difficulty Index- Pre Lecture- 69 % Post Lecture- 99%
52 Q7-which of the following effects of the steroid digitalis is observed after treatment of congestive heart failure. a-decrease in cytosolic sodium levels b-inhibition of Na-K ATPase c-decrease in the force of heart muscle contraction d-stimulation of the plasma membrane ion pump.Ans- b Difficulty Index- Pre Lecture-12 % Post Lecture- 78%
53 Q8-you wish to design a new drug which will act as an ionophore to deliver Ca2+ across the nerve cell membrane .This drug would most likely be a-hydrophobic on the outside and hydrophilic on inside b-insoluble in lipid c-soluble in proteins d-smaller than nm in diameterAns- a Difficulty Index- Pre Lecture- 26 % Post Lecture- 89%
54 Q9- the process by which a cell secretes macro-molecule by fusing a vesicle to the plasma membrane is calleda-endocytosisb-exocytosisc-pinocytosisd-phagocytosisAns- b Difficulty Index- Pre Lecture- 59 % Post Lecture- 98%
55 Q10- free fatty acids enter cell by a-passive diffusion b-active diffusion c- through carrier protein d – Active transportAns- a Difficulty Index- Pre Lecture- 29 % Post Lecture- 88%
56 Q-11 Aquaglyceroporins transport- a. Water only b. water and small molecules.c. Water and Glucosed. Water and salt.Ans- b Difficulty Index- Pre Lecture- 06 % Post Lecture- 78%
57 Q-12 Which of the fallowing is responsible for PH Regulation- a. Antiporters.b. Symportersc. Uniporters.d. Co-porters.Ans- a Difficulty Index- Pre Lecture- 29 % Post Lecture- 92%
58 Q-13 V type – transporters are a. ATPase dependent. b. Symporters. c. Carrier Proteins.d. Receptor Proteins.Ans- a Difficulty Index- Pre Lecture- 18 % Post Lecture- 76%
59 Q-14 .GLUT is an example of- a. Antiporters. b. Symporters c. Uniporters.d. Co-porters.Ans- C Difficulty Index- Pre Lecture- 18 % Post Lecture- 89%
60 Q-15 Presence of Ion channels are must on a. Excitable tissue. b. Non excitable tissue.c. Renal tissued. Cardiac muscle.Ans- a Difficulty Index- Pre Lecture- 12 % Post Lecture- 84%
61 Q-16. Na- K ATPase transport Na- a. Towards Concentration gradient. b Q-16. Na- K ATPase transport Na- a. Towards Concentration gradient. b. Against Concentration gradient. c. Towards electro chemical gradient. d. Against electrochemical gradient.Ans- C Difficulty Index- Pre Lecture- 41 % Post Lecture- 98%
62 Q-17. Rennin secretion from JG cells is an example of- a.) Exocytosis b.) pincocytosisc.) Vacular movement.d.) Transcytosis.Ans- a Difficulty Index- Pre Lecture- 38 % Post Lecture- 94%
63 Q.- 18. PTH secretion fro parathyroid glands require- a.) low intracellular Ca.b.) high Intracellular Ca.c.) Low intracellular K.d.) high Intracellular K.Ans- a Difficulty Index- Pre Lecture- 27 % Post Lecture- 92%
64 Q-19. Transcytosis incudes- a. Endocytosis and phagocytosis. b. Endocytosis and pincocytosis.c. Endocytosis and exocytosis.d. Endocytosis only.Ans- C Difficulty Index- Pre Lecture- 29 % Post Lecture- 78%
65 Q-20. Transcytosis occurs at a). Epethelial Cells. b). Endocrine Cells Q-20. Transcytosis occurs at a). Epethelial Cells. b). Endocrine Cells. c). Nerve cells. d). None of the above.Ans-a Difficulty Index= Pre Lecture % Post Lecture-74 %