Fluid Mosaic Model• Current model of the membrane structure.• Phospholipids fluid sea in embedded with a

wide variety of protein molecules.

Cell Membrane• The cell membrane is also known as:

–Phospholipids bi-layer–Plasma membrane–Fluid mosaic membrane

What is a Solution?• Is a homogeneous mixture• A combination of a Solute and

Solvent.• Large part is the solvent (water)• Small part is the solute

What is a [ ] Gradient?

• Is the process of particles, which the solutes is moving through a solution from an area of higher number of particles to an area of lower number of particles.

[ High ] to [Low]

Concentration Gradient

Down

Low

High

Prot

ein

Carrier moleculeCa

rrie

r

What can diffuse through?

• Small & nonpolar molecules can diffuse through the cell membrane•CO2

•O2

Understanding solutions

• More Solvent• Less Solute

• Less solvent• More Solute

solute

solvent

Understanding solutions

Hypotonic solution Hypertonic Solution

solute

solvent

Understanding solutions

• Hypotonic Solution • Hypertonic solution

Cell

solvent

solute

Understanding solutions• The solution has solvent and solute• The cell has solvent and solute too.

solute

Who has more solute?

What type of solution is this cell in?

25% solute

75% solute

What will happen to this cell?

H2O

CellShrinks

Who has more solute?

What type of solution is this cell in?

85% solute

15% solute

H2OCell

Swells or burst

Lysis

Who has more solute?

What type of solution is this cell in?

40% solute

40% solute

Isotonic solution

40% solute

40% solute

60% water

60% water

60% water

60% water

The cell stays the same

Hypertonic Solution

Plant Cells Animal Cells

Hydrophobic vs Hydrophilic• Hydrophilic (attracted to water)

• Hydrophobic (not attracted to water but are attracted to other hydrophobic tails)

• They have a hydrophilic phosphate head and two hydrophobic hydrocarbon tails.

• Cell membranes are made up of a double layer of these phospholipid molecules.

• The phospholipid bilayer makes the membrane very stable but also allows flexibility.

• The phospholipid in the membrane are in a fluid state which allows the cell to change it’s shape easily.

Osmotic Pressure • The pressure of water moving

across a membranes cause by a concentration gradient.

Turgor Pressure

• Is a hydrostatic pressure due to a plant cell being placed in a hypotonic solution.• Is pressure on inside of a cell against

the cell wall.• Only in plant cells

What is Plasmolysis?• The Shrinking of cell membrane from

cell wall in a plant or bacterial cell, caused by loss of water through osmosis.

• from Greek lusis, a loosening.

What is Crenation?• Crenation is the contraction of a cell after

exposure to a hypertonic solution, due to the loss of water through osmosis.

• Crenation occurs because in a hypertonic environment, osmosis .

• As a result the cell shrinks and forms abnormal notchings around its edges.

What is cytolysis?• Cytolysis, or osmotic lysis, occurs when a cell bursts

due to an osmotic imbalance that has caused excess water to move into the cell.

• It occurs in a hypotonic environment. • Where water moves into the cell by osmosis where

the volume exceeds the membrane's capacity and the cell bursts.

• The presence of a cell wall prevents the membrane from bursting, so cytolysis only occurs in animal and protozoa cells which do not have cell walls.

Active or Passive Transport• Endocytosis • Diffusion• Exocytosis• Osmosis• Oxygen• Carbon dioxide• Sugar• Water• Pinocytosis• Phagocytosis

Active

Passive

Active

Passive

Passive

Passive

Passive

Passive

Active

Active

Leaf Anatomy