Transport Transport Across the Across the

Plasma Plasma MembraneMembrane

Plasma Membrane TransportPlasma Membrane Transport

• Molecules move across the plasma Molecules move across the plasma membrane by:membrane by:

What are three types of What are three types of passive transport?passive transport?

1)1) DiffusionDiffusion

2)2) Facilitated DiffusionFacilitated Diffusion

3)3) OsmosisOsmosisATP energy is ATP energy is notnot

needed to move the needed to move the molecules through.molecules through.

Passive Transport 1: DiffusionPassive Transport 1: Diffusion

• Molecules can move directly Molecules can move directly through the phospholipids of the through the phospholipids of the plasma membraneplasma membrane

This is called …This is called …

What is Diffusion?What is Diffusion?

• Diffusion is the net Diffusion is the net movement of molecules movement of molecules from a high from a high concentration to a low concentration to a low concentration until concentration until equally distributed.equally distributed.

• Diffusion rate is related Diffusion rate is related to temperature, to temperature, pressure, state of matter, pressure, state of matter, size of concentration size of concentration gradient, and surface gradient, and surface area of membrane.area of membrane.

http://www.biologycorner.com/resources/diffusion-animated.gif

What molecules pass through the What molecules pass through the plasma membrane by diffusion?plasma membrane by diffusion?

• Gases (oxygen, carbon Gases (oxygen, carbon dioxide)dioxide)

• Water molecules (rate Water molecules (rate slow due to polarity)slow due to polarity)

• Lipids (steroid Lipids (steroid hormones)hormones)

• Lipid soluble molecules Lipid soluble molecules (hydrocarbons, alcohols, (hydrocarbons, alcohols, some vitamins)some vitamins)

• Small noncharged Small noncharged molecules (NHmolecules (NH33))

Why is diffusion important to cells Why is diffusion important to cells and humans?and humans?

• Cell respirationCell respiration• Alveoli of lungsAlveoli of lungs• CapillariesCapillaries• Red Blood CellsRed Blood Cells• Medications: time-Medications: time-

release capsulesrelease capsules

Passive Transport 2: Facilitated Passive Transport 2: Facilitated DiffusionDiffusion

• Molecules can move through the Molecules can move through the plasma membrane with the aid of plasma membrane with the aid of transport proteinstransport proteins

This is called …This is called …

What is Facilitated Diffusion?What is Facilitated Diffusion?

• Facilitated diffusion Facilitated diffusion is the net movement is the net movement of molecules from a of molecules from a high concentration to high concentration to a low concentration a low concentration with the aid of with the aid of channel or carrier channel or carrier proteinsproteins..

What molecules move through the plasma What molecules move through the plasma membrane by facilitated diffusion?membrane by facilitated diffusion?

• IonsIons (Na(Na++, K, K++, Cl, Cl--))

• Sugars (Glucose)Sugars (Glucose)

• Amino AcidsAmino Acids

• Small water soluble Small water soluble moleculesmolecules

• Water (faster rate)Water (faster rate)

How do molecules move through the How do molecules move through the plasma membrane by facilitated diffusion?plasma membrane by facilitated diffusion?

• Channel and Carrier proteins are specific:Channel and Carrier proteins are specific:• Channel Proteins allow ions, small solutes, and water Channel Proteins allow ions, small solutes, and water

to passto pass• Carrier Proteins move glucose and amino acidsCarrier Proteins move glucose and amino acids• Facilitated diffusion is rate limited, by the number of Facilitated diffusion is rate limited, by the number of

proteins channels/carriers present in the membrane.proteins channels/carriers present in the membrane.

Specific Types of Facilitated Specific Types of Facilitated DiffusionDiffusion

Counter TransportCounter Transport – the transport – the transport of two substances at the same time of two substances at the same time in opposite directions, without ATP. in opposite directions, without ATP. Protein carriers are called Protein carriers are called AntiportsAntiports..

Co-transport Co-transport – the transport of – the transport of two substances at the same time in two substances at the same time in the same direction, without ATP. the same direction, without ATP. Protein carriers are called Protein carriers are called SymportsSymports..

Gated ChannelsGated Channels – receptors – receptors combined with channel proteins. combined with channel proteins. When a chemical messenger binds When a chemical messenger binds to a receptor, a gate opens to allow to a receptor, a gate opens to allow ions to flow through the channel. ions to flow through the channel.

Why is facilitated diffusion important Why is facilitated diffusion important to cells and humans?to cells and humans?

• Cells obtain food for Cells obtain food for cell respirationcell respiration

• Neurons Neurons communicatecommunicate

• Small intestine cells Small intestine cells transport food to transport food to bloodstreambloodstream

• Muscle cells contractMuscle cells contract

Passive Transport 3: OsmosisPassive Transport 3: Osmosis

• Water Molecules can move directly Water Molecules can move directly through the phospholipids of the through the phospholipids of the plasma membraneplasma membrane

This is called …This is called …

What is Osmosis?What is Osmosis?

• Osmosis is the diffusion of water through a Osmosis is the diffusion of water through a semipermeable membrane. Water molecules bound semipermeable membrane. Water molecules bound to solutes cannot pass due to size, only unbound to solutes cannot pass due to size, only unbound molecules. Free water molecules collide, bump into molecules. Free water molecules collide, bump into the membrane, and pass through.the membrane, and pass through.

Why is osmosis important to cells Why is osmosis important to cells and humans?and humans?

• Cells remove water Cells remove water produced by cell produced by cell respiration.respiration.

• Large intestine cells Large intestine cells transport water to transport water to bloodstreambloodstream

• Kidney cells form Kidney cells form urineurine

Osmosis and TonicityOsmosis and Tonicity

Tonicity refers to the total solute Tonicity refers to the total solute concentration of the solution outside the concentration of the solution outside the cell.cell.

What are the three types of tonicity?What are the three types of tonicity?1)1) IsotonicIsotonic

2)2) HypotonicHypotonic

3)3) HypertonicHypertonic

IsotonicIsotonic Solutions that have the Solutions that have the samesame concentration of concentration of

solutes as the suspended cell.solutes as the suspended cell.

What will happen to a cell placed in an Isotonic What will happen to a cell placed in an Isotonic solution?solution?

The cell will have no net movement of water and The cell will have no net movement of water and will stay the same size.will stay the same size.

Ex. Blood plasma has high concentration of Ex. Blood plasma has high concentration of albumin molecules to make it isotonic to tissues.albumin molecules to make it isotonic to tissues.

HypotonicHypotonic Solutions that have a Solutions that have a lowerlower solute concentration solute concentration

than the suspended cell.than the suspended cell.

What will happen to a cell placed in a Hypotonic What will happen to a cell placed in a Hypotonic solution?solution?

The cell will gain water and swell.The cell will gain water and swell. If the cell bursts, then we call this lysis. (Red blood If the cell bursts, then we call this lysis. (Red blood

cells = hemolysis)cells = hemolysis) In plant cells with rigid cell walls, this creates In plant cells with rigid cell walls, this creates

turgor pressure.turgor pressure.

HypertonicHypertonic Solutions that have a Solutions that have a higherhigher solute concentration solute concentration

than a suspended cell.than a suspended cell.

What will happen to a cell placed in a Hypertonic What will happen to a cell placed in a Hypertonic solution?solution?

The cell will lose water and shrink. (Red blood The cell will lose water and shrink. (Red blood cells = crenation)cells = crenation)

In plant cells, the central vacuole will shrink and In plant cells, the central vacuole will shrink and the plasma membrane will pull away from the cell the plasma membrane will pull away from the cell wall causing the cytoplasm to shrink called wall causing the cytoplasm to shrink called plasmolysis.plasmolysis.

Review: Passive TransportReview: Passive Transport

• DiffusionDiffusion – O – O22 moves in and CO moves in and CO22 moves out moves out during cell respirationduring cell respiration

• Facilitated DiffusionFacilitated Diffusion – glucose and amino – glucose and amino acids enter cell for cell respirationacids enter cell for cell respiration

• OsmosisOsmosis – cell removal or addition of water – cell removal or addition of water

Review TonicityReview Tonicity What will happen to a red blood cell in a What will happen to a red blood cell in a

hypertonic solution?hypertonic solution? What will happen to a red blood cell in an What will happen to a red blood cell in an

isotonic solution?isotonic solution? What will happen to a red blood cell in a What will happen to a red blood cell in a

hypotonic solution?hypotonic solution?

1) Active Transport1) Active Transport2) Exocytosis2) Exocytosis3) Endocytosis3) Endocytosis

– PhagocytosisPhagocytosis– PinocytosisPinocytosis– Receptor-Mediated Receptor-Mediated

endocytosisendocytosis

What are three types of What are three types of Active transport?Active transport?

ATP energy is ATP energy is requiredrequired to move the to move the molecules through.molecules through.

Active TransportActive Transport Molecules move from areas of low Molecules move from areas of low

concentration to areas of high concentration concentration to areas of high concentration with the aid of ATP energy.with the aid of ATP energy.

Requires protein carriers called Pumps.Requires protein carriers called Pumps.

The Importance of Active TransportThe Importance of Active Transport Bring in essential molecules: ions, Bring in essential molecules: ions,

amino acids, glucose, nucleotidesamino acids, glucose, nucleotides Rid cell of unwanted molecules (Ex. Rid cell of unwanted molecules (Ex.

sodium from urine in kidneys)sodium from urine in kidneys) Maintain internal conditions different Maintain internal conditions different

from the environmentfrom the environment Regulate the volume of cells by Regulate the volume of cells by

controlling osmotic potentialcontrolling osmotic potential Control cellular pHControl cellular pH Re-establish concentration Re-establish concentration

gradients to run facilitated diffusion. gradients to run facilitated diffusion. (Ex. Sodium-Potassium pump and (Ex. Sodium-Potassium pump and Proton pumps)Proton pumps)

The Sodium-Potassium PumpThe Sodium-Potassium Pump 3 Sodium ions move out of 3 Sodium ions move out of

the cell and then 2 the cell and then 2 Potassium ions move into Potassium ions move into the cell.the cell.

Driven by the splitting of Driven by the splitting of ATP to provide energy and ATP to provide energy and conformational change to conformational change to proteins by adding and then proteins by adding and then taking away a phosphate taking away a phosphate group.group.

Used to establish an Used to establish an electrochemical gradient electrochemical gradient across neuron cell across neuron cell membranes.membranes. http://www.biologie.uni-hamburg.de/b-online/library/biology107/bi107vc/fa99/terry/images/ATPpumA.gif

Active Transport 2: ExocytosisActive Transport 2: Exocytosis Movement of large Movement of large

molecules bound in molecules bound in vesicles vesicles out ofout of the cell the cell with the aid of ATP with the aid of ATP energy. Vesicle fuses energy. Vesicle fuses with the plasma with the plasma membrane to eject membrane to eject macromolecules.macromolecules.

Ex. Proteins, Ex. Proteins, polysaccharides, polysaccharides, polynucleotides, whole polynucleotides, whole cells, hormones, mucus, cells, hormones, mucus, neurotransmitters, wasteneurotransmitters, waste

Active Transport 3: EndocytosisActive Transport 3: Endocytosis

Movement of large molecules Movement of large molecules intointo the cell the cell by engulfing them in vesicles, using ATP by engulfing them in vesicles, using ATP energy.energy.

Three types of Endocytosis:Three types of Endocytosis:– PhagocytosisPhagocytosis– PinocytosisPinocytosis– Receptor-mediated endocytosisReceptor-mediated endocytosis

PhagocytosisPhagocytosis ““Cellular Eating” – engulfing large Cellular Eating” – engulfing large

molecules, whole cells, bacteria molecules, whole cells, bacteria Ex. Macrophages ingesting bacteria or worn Ex. Macrophages ingesting bacteria or worn

out red blood cells.out red blood cells. Ex. Unicellular organisms engulfing food Ex. Unicellular organisms engulfing food

particles.particles.

PinocytosisPinocytosis ““Cellular Drinking” – engulfing liquids and Cellular Drinking” – engulfing liquids and

small molecules dissolved in liquids; small molecules dissolved in liquids; unspecific what enters.unspecific what enters.

Ex. Intestinal cells, Kidney cells, Plant root Ex. Intestinal cells, Kidney cells, Plant root cellscells