2/3/2015 Anwar Sohail Mohammad

1

The Plasma Membrane

&

Homeostasis

GPS

SB1 (a) Explain the role of cell membrane

in maintaining homeostasis.

SB1 (d) Explain the impact of water on

life processes (i.e., osmosis,

diffusion).

Learning Targets 1. I can label the Structure of plasma membrane.

2. I can describe the functions of plasma membrane and

the role of its parts.

3. I can classify and explain two types of Homeostasis.

4. I can describe how diffusion and facilitated diffusion

takes place.

5. I can describe 3 types of Osmosis; and 3 types of

solutions.

6. I can determine the type of osmosis in real life

situations.

7. I can describe how vesicle mediated transport works.

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1. LT-2: I can describe the functions of plasma membrane and

the role of its parts.

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Phospholipid

molecule

Transport

Protein

Carbohydrate

Chain

Cholesterol

molecule

LT-1: I can label the Structure of plasma membrane.

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The plasma membrane is a thin, flexible boundary

between the cell and its environment, composed of the

phospholipid bilayer.

1. Phospholipid molecules

Chapter 7

A phospholipid molecule consists of a hydrophilic head

(phosphate group) and two hydrophobic tails (fatty acid

chains) connected by means of Glycerol backbone. Hydrophilic Head

Hydrophobic

Tail

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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Fluid Mosaic Model

The phospholipid bi-layer is flexible.

It allows other molecules (like H2O, O2, CO2 etc.)

to “float” in and through the membrane;

therefore, this model is called “Fluid Mosaic

Model”.

Other Components

Proteins

Cholesterol

Carbohydrates

7.2 The Plasma Membrane

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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Cholesterol prevents fatty acid tails from sticking

together.

Cellular Structure and Function

Carbohydrates identify Chemical Signals

7.2 The Plasma Membrane

Carbohydrate

Chain

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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Proteins

Cellular Structure and Function

Transmit signals inside the cell

Act as a support structure

Provide pathways for substances to enter and leave

7.2 The Plasma Membrane

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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Selective Permeability

Cellular Structure and Function

What does it do?

Chapter 7

Plasma membrane determines

1.What should enter the cell

and how much

2.What should exit the cell

and how much

Due to this, plasma

membrane is called

selectively permeable.

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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How do things pass through it? 1. Small molecules like water, carbon dioxide,

oxygen etc. pass through the tiny gaps between

the spherical heads.

2. Larger molecules pass through channel proteins

3. Some other molecules pass through carrier

proteins by means of a mechanism called

“Facilitated diffusion”

#1 and 2 are called simple diffusion.

4. Another process called “Active transport” forces material across the

plasma membrane against concentration gradient.

LT-2: I can describe the functions of plasma membrane and the role of its parts.

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Cellular Transport

ACTIVE TRANSPORT

PASSIVE TRANSPORT

Cells need to take in or throw out materials like oxygen or

carbon dioxide gas, food particles or molecules of

chemicals or water to maintain Chemical balance in the cell

called homeostasis.

This refers to “Cellular Transport”.

It is of two types:

and

LT-3: I can classify & explain two types of Homeostasis.

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Osmosis

Diffusion

Facilitated Diffusion By means of transport proteins

Ex: Sodium Potassium Pump

Vesicle mediated Transport

Cellular Transport (Homeostasis)

PASSIVE TRANSPORT

Energy is not required

According to concentration gradient.

(High Concentration to low

concentration)

ACTIVE TRANSPORT

Energy is required in the form of ATP

Against the concentration gradient.

(Low Concentration to high

concentration)

LT-3: I can classify & explain two types of Homeostasis.

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Diffusion (Passive Transport)

• Diffusion is the net movement of a substance (liquid or gas) from an area of higher concentration to one of lower concentration.

• Ex: Air freshener quickly diffuses in the air.

• Dye spreads in the water and quickly distributes itself uniformly.

• Sugar diffuses in the water and make it taste sweet.

LT-4: I can describe how diffusion & facilitated diffusion take place.

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Semi permeable membrane

(Plasma membrane) Solute molecules,

High Concentration Solute molecules,

low Concentration

Diffusion Animation

In “Diffusion” Solute molecules move across a semi permeable

membrane from the region of high concentration to low

concentration until the concentration on either side becomes equal.

LT-4: I can describe how diffusion & facilitated diffusion take place.

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LT-4: I can describe how diffusion & facilitated diffusion take place.

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Facilitated Diffusion (Passive Transport)

• Large molecules like glucose can’t pass

through the plasma membrane.

• The protein molecules, called channel

proteins or Transport proteins or carrier

molecules, span and allow them to pass

through.

• This is called facilitated diffusion.

• Energy is not needed in the process.

Click HERE for Facilitated Diffusion animation (Its really cool)

LT-4: I can describe how diffusion & facilitated diffusion take place.

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Cellular Structure and Function Chapter 7 LT-4: I can describe how diffusion & facilitated diffusion take place.

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Osmosis (Passive Transport)

• Osmosis is the movement of a liquid

(most often assumed to be water, but it

can be any liquid solvent) through a semi

permeable membrane from a region of

low solute concentration to a region of

high solute concentration.

-:Continued

LT-5: I can describe 3 types of Osmosis & 3 types of solutions.

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Osmosis (Passive transport)

10 mg/L

sugar solution

15 mg/L

sugar solution

A B

More Concentrated Less Concentrated

Water

LT-5: I can describe 3 types of Osmosis & 3 types of solutions.

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Types of solutions (Hypertonic, Hypotonic and Isotonic)

Hypertonic solutions are those in which more solute (and

hence lower water potential) is present.

If a cell is placed in Hypertonic solution, water moves out of

the cell, this is called exosmosis.

Hypotonic solutions are those with less solute (again read as

higher water potential).

If a cell is placed in Hyportonic solution, water moves in to

the cell, this is called endosmosis.

Isotonic solutions have equal (iso-) concentrations of

substances. Water potentials are thus equal, although there

will still be equal amounts of water movement in and out of

the cell, the net flow is zero.

If a cell is placed in Isotonic solution, osmosis doesn’t take

place.

LT-5: I can describe 3 types of Osmosis & 3 types of solutions.

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Cellular Structure and Function Chapter 7 LT-5: I can describe 3 types of Osmosis & 3 types of solutions.

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Cells placed in Hypotonic and

Hypertonic solutions

(Hypotonic) (Hypertonic)

LT-5: I can describe 3 types of Osmosis & 3 types of solutions.

Learning check: Determine

Exosmosis/endosmosis/dynamic equilibrium

1. An ocean fish placed in fresh water tank._____

2. A fresh water fish placed in salt water aquarium. _____

3. A pond fish placed in fresh water aquarium. _________

4. Cherios soaking milk. _________

5. Raisins swell in water. ______________

6. Blood cells placed in distilled water __________

7. Blood cells placed in salt water. _____________

8. Celery placed in salt water shrinks over time _______

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LT-6: I can determine the type of Osmosis in real life situation.

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ACTIVE TRANSPORT

Active transport requires the cell to spend

energy, usually in the form of ATP. Examples

include transport of large molecules (non-

lipid soluble) and the sodium-potassium

pump.

LT-7: I can describe how vesicle mediated transport works.

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Vesicle-mediated transport When particles are so large that they cannot pass through

any carrier protein, then cells use vesicle-mediated

transport. Energy is required in the form of ATP.

LT-7: I can describe how vesicle mediated transport works.

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Vesicle-mediated transport

Animation

LT-6: I can describe how vesicle mediated transport works.

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Vesicle-mediated transport • Vesicles and vacuoles that fuse with the

cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell.

• Exocytosis When the cell removes something from the cell (Exo = Exit).

• Endocytosis When some thing is taken in (Endo = Taken in)

• Phagocytosis is the type of endocytosis where an entire cell is engulfed.

• Pinocytosis is when the external fluid is engulfed.

LT-7: I can describe how vesicle mediated transport works.