/
 Lecture #  8: The Cell Surface (Part 2)  Lecture #  8: The Cell Surface (Part 2)

Lecture # 8: The Cell Surface (Part 2) - PowerPoint Presentation

alida-meadow
alida-meadow . @alida-meadow
Follow
355 views
Uploaded On 2020-04-10

Lecture # 8: The Cell Surface (Part 2) - PPT Presentation

Chapter 3 Objectives 1 Define a cell and distinguish between cytosol and cytoplasm 2 Explain the structure and molecular organization of the cell membrane and list factors determining its selective permeability ID: 776597

membrane concentration cell transport membrane concentration cell transport gradient solution diffusion osmosis solute pressure higher mediated solutes water energy

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document " Lecture # 8: The Cell Surface (Part 2)..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Lecture # 8: The Cell Surface (Part 2)

(Chapter 3)

Objectives:

1- Define a cell and distinguish between cytosol and cytoplasm.

2- Explain the structure and molecular organization of the cell membrane and list factors determining its selective permeability.

4- Explain and illustrate the following mechanisms of cell transport: diffusion, osmosis, facilitated diffusion, active transport endocytosis, and exocytosis.

3- Explain osmotic pressure and how isotonic, hypertonic, and hypotonic solutions affect cells.

Slide2

PASSIVE TRANSPORT

ACTIVE TRANSPORT

It moves ions or molecules across the plasma membrane with no expenditure of energy by the

cell (down gradient)

It requires that the cell expends energy, generally in the form of

ATP (up gradient)

Simple

Diffusion (down gradient)

Osmosis (a special case of simple diffusion)

Facilitated Diffusion (down gradient, carrier mediated)

The Sodium-Potassium Pump

Secondary Active Transport

Vesicular Transport

1- Endocytosis

2- Exocytosis

Receptor-Mediated Endocytosis

Pinocytosis

Phagocytosis

Membrane Transport

Filtration

(driven by hydrostatic pressure)

Slide3

1- Filtration

It is the process in which particles are driven through a selectively permeable membrane by hydrostatic pressure (force exerted on a membrane by water)

1- Filtration of nutrients through gaps in blood capillary walls into tissue fluids

Examples:

Blood pressure in

capillary forces

water and small solutes such as salts through narrow clefts between capillary cells.

2- Filtration of wastes from the blood in the kidneys while holding back blood cells and proteins

Slide4

It is the passive net movement of ions or molecules from the region of higher concentration to the region of lower concentration.

It is the difference between the high and low concentration areas

Lower concentration

Higher concentration

Concentration Gradient:

The tendency of ions and molecules in a concentration gradients is to move from the region of higher concen-tration to the region of lower concentration

Diffusion:

Diffusion tends to eliminate the concentration gradient

Brownian Movement:

It

is the irregular movement of particles suspended in a liquid or gas caused by the kinetic energy of these particles

Slide5

Concentration Gradient:

The natural tendency of a solute is to move

down

its concentration gradient, from higher concentration to lower concentration.

It is the difference between the high and low concentration areas of a solute within a given medium

5- Membrane permeability :  permeability,  rate

Factors affecting diffusion rate through a membrane

3- Temperature:

temp.,

motion of particles

1- Steepness of concentrated gradient:

difference,  rate

2- Molecular weight: larger molecules move slower

4- Membrane surface area:  area,  rate

The random molecular motion of particles (Brownian movement) provides the necessary energy

Slide6

Down gradient

Larger molecules move slower

Diffusion in a Concentration Gradient

Substance A is larger (higher molecular weight) than substance B

A

B

Slide7

Impermeable Membrane

It is a membrane through which none substance can pass

Slide8

It is a membrane through which any substance can pass

Freely Permeable membrane

Slide9

Selectively Permeable Membrane

It is a membrane that permits the free passage of some materials and restricts the passage of other

The plasma membrane works as a selectively permeable membrane

It allows some things through, such as nutrients and wastes, but usually prevents other things as proteins and phosphates, from entering or leaving the cell.

Slide10

It is the passive net diffusion of solvent (water), across a selectively permeable membrane, toward the solution that has the higher concentration of solutes

A

B

Osmosis:

OSMOSIS

Osmosis and Tonicity

Slide11

Osmosis

Reverse

osmosis

Side A

Side B

The

hydrostatic pressure

causes a filtration of water from A to B (

reverse osmosis

) , which produces that

net osmosis

slows down and stop

At this point, an equilibrium would exist

It is the hydrostatic pressure required to stop osmosis

Osmotic Pressure:

The higher the concentration of nonpermeating solute in A, the greater the osmotic pressure

Hydrostatic pressure

Slide12

Osmolarity and Tonicity

It is the total solute concentration (osmole/L) in an aqueous solution

Solution A has a lower osmolarity than solution B

Solution B has a higher osmolarity than solution A

OSMOSIS

A

B

If two solutions of different

osmolarity

are separated by a selectively permeable membrane, the solvent (water) will pass the membrane until equilibrium is attained and both solution contain equal concentration of solutes

One

osmole:

It is one mole of dissolve particles

Osmolarity:

Slide13

It is the ability of a solution to affect fluid volume and pressure in a cell

Isotonic solution

It is a solution with the same concentration of non-penetrating solutes as that found in the cells. (Intravenous solutions are isotonic solutions).

Hypertonic solution

It is a solution with a higher concentration non-penetrating solutes than that found in the cells.

Hypotonic solution

It is a solution with a lower concentration of non-penetrating solutes than that found in the cells.

water

water

water

water

Tonicity:

Slide14

Osmotic Flow across a Plasma Membrane

Slide15

Effects of Tonicity on RBCs

Hypotonic, isotonic and hypertonic solutions affect the fluid volume of a red blood cell. Notice the crenated and swollen cells.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a) Hypotonic

(b) Isotonic

(c) Hypertonic

© Dr. David M. Phillips/Visuals Unlimited

Swollen cell

Normal cell

Crenated cell

Slide16

Carrier-Mediated Transport

It is a process that employs transport proteins (carriers) in the plasma membrane that carry solutes from one side of the membrane to the other.

Carrier-Mediated Transport:

1- Facilitated Diffusion:

It is the carried-mediated transport of a solute through the membrane down its concentration gradient.

It is a passive transport process; that is, does not consume ATP (energy)

2- Active Transport:

It is the carried-mediated transport of a solute through the membrane up its concentration gradient, using energy provided by the ATP.

Carriers:

1- Uniport: It carries one solute at a time

2- Symport: It carries two or more solutes through the membrane simultaneously in the same direction (cotransport)

3- Antiport: It carries two or more solutes through the membrane in opposite directions (countertransport)

Slide17

1- Facilitated Diffusion:

It is the carried-mediated transport of a solute through the membrane down its concentration gradient.

It is a passive transport process; that is, does not consume ATP (energy)

Uniport:

It carries one solute at a time

Slide18

2- Active Transport:

It is the carried-mediated transport of a solute through the membrane up its concentration gradient, using energy provided by the ATP.

Sodium-Potassium Pump

2- Each pump cycle consumes one ATP and exchanges three Na+ for two K+ against (up) the gradient

1- Na

+

and K+ are constantly leaking through membrane down the gradient

3- The pump keeps the K+ concentration higher and the Na+ concentration lower with in the cell than in the extracellular fluid (ECF)

4- Half of daily calories is used for

the Na+ - K+ pump

Slide19

Vesicular Transport

It is when materials move into or out of the cell in vesicles, small membranous sacs that form at, or fuse with, the plasma membrane

1- Endocytosis

2- Exocytosis

Receptor-Mediated Endocytosis

Pinocytosis

Phagocytosis

Slide20

Phagocytosis (cell eating)

It is a process of bringing large materials (bacteria, dust, cellular debris) into the cell by means of pseudopodia that surround the material

Slide21

Phagocytosis or “Cell-Eating”

Keeps tissues free of debris and infectious microorganisms.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Particle

Pseudopod

Nucleus

Residue

Phagosome

Lysosome

Vesicle fusing

with membrane

Phagolysosome

1

2

3

4

5

6

7

A phagocytic cell encounters aparticle of foreign matter.

The cell surroundsthe particle with itspseudopods.

The particle is phagocytizedand contained in aphagosome.

The phagosome fuses

with a lysosome and

becomes a phagolysosome.

The indigestible

residue is voided by

exocytosis.

The phagolysosomefuses with theplasma membrane.

Enzymes from the

lysosome digest theforeign matter.

Slide22

Pinocytosis (cell drinking)

It is a form of endocytosis that brings into the cell a small volume of extracellular fluid (ECF)

Slide23

Receptor-Mediated Endocytosis

It involves the formation of vesicles at the surface of the plasma membrane, which contain specific receptors (ligand receptors) for the substance that will be interiorized (ligand)

Lipoproteins (cholesterol), iron ions (Fe 2+)

Slide24

Exocytosis

It is the movement of materials out of the cell through the fusion of a vesicle with the plasma membrane