Cell Membranes

Osmosis

"Osmosis is defined as: the diffusion of WATER MOLECULES across a SELECTIVELY PERMEABLE MEMBRANE, From a region where they (the water molecules) are in HIGH Concentration TO a region where they (the water molecules) are in LOWER Concentration

Equilibrim

(Equilibrium is DEFINED as having equal numbers of the same type of molecule on each side of a semi permeable membrane).

Phospholipids in the Cell Membrane

- The CELL MEMBRANE is also called The PLASMA MEMBRANE. - It is made up of two layers of a special kind of fat/lipid molecule called a phospholipid. - Because cell membranes are made up of two layers of phospholipid molecules the cell membrane (plasma membrane ) is called a lipid bi-layer (bi= two) - Heads are hydrophilic and two fatty acid tails are hydrophobic

Hypotonic

A Hypotonic solution is a solution with the lower concentration of solute. When a cell's cytoplasm is bathed in a hypotonic solution the water will be drawn out of the solution and into the cell by osmosis. If water molecules continue to diffuse into the cell, it will cause the cell to swell, up to the point that cytolysis (rupture) may occur. - Net water flow is into the cell

What properties of glucose prevent it from easily crossing a membrane?

A glucose molecule is both large and polar, and rarely crosses a membrane by simple diffusion

Hypertonic

A hypertonic solution is a solution with the higher concentration of solute. When a cell's cytoplasm is bathed in a hypertonic solution the water will be drawn into the solution and out of the cell by osmosis. If water molecules continue to diffuse out of the cell, it will cause the cell to shrink, or crenate - Net water flow is out of the cell

Vesicles

A small membrane sacs that specialize in moving products into, out of, and within a cell

Why does diffusion speed up with with increasing temperature

Because Molecules move faster with increasing temperature

What properties of carbon dioxide and oxygen allow them to easily cross a membrane?

Carbon Dioxide and Oxygen both easily pass through a membrane because they are both non polar molecules and small

Diffusion

Diffusion is defined as: "The movement of molecules From a region (area) where they are in a High concentration TO a region (area) where they are in a lower concentration." - After much time both molecules will become evenly spread throughout this solution (equilibrium)

Passive Transport

Doesn't require energy Ex: Oxygen and Water entering the cell

endocytosis

Endocytosis takes material into the cell within vesicles that bud inward from the plasma membrane. Larger membrane sacs are also formed by endocytosis when food particles are ingested

A benzene molecule is completely non polar and a little smaller than a glucose molecule. Would it cross a membrane faster, or slower, than glucose? Why?

Faster, a benzene molecule is non-polar, so it is not held back by attraction to water the way that glucose is. Because it is smaller, a benzene molecule fits between phospholipids more easily than a glucose molecule

exocytosis

In exporting protein products from a cell, a vesicle containing the protein fuses with the plasma membrane and spills it's contents outside of the cell

Plasma Membrane

Know that Plasma Membranes act as "selective barriers" to molecules. Think of a membrane as having "lots of small holes in it" Selective means that the membrane lets some types of molecules through it but not others. (Based on the size of the molecule!) SEMI-PERMABLE

Flaccid

Not firm, hard, or solid

Proteins in the Membrane

PROTEIN molecules (large purple shape) are embedded into the plasma membrane. These are really important for transporting substances from one side of a plasma membrane to the other - Functions: 1. Enzyme Activity 2. Cell to cell recognition 3. Cell signaling 4. Transport of materials

Plasmolysed

Plasmolysis is the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis. This occurs in a hypertonic solution. Plasmolysis is the contraction of the protoplast of a plant cell as a result of loss of water from the cell.

What property of the sodium ion prevents it from crossing a membrane?

Sodium ion is a charged particle, which prevents it from crossing the hydrophobic phospholipid bilayer

Isotonic

Solutions in which the concentrations of solute are equal. - Water flow is equal in both directions Ex: Saline Solution

Faclliclitated Diffusion

The transport protein allows the polar molecule to cross the membrane from greater concentration to lower concentration in the process of Falliclitated Diffusion

Selectively Permeable Membrane

This type of membrane allows some substances to cross the membrane than others and blocks the passage of some substances all together

Active Transport

Using energy actively to move something from high <-> low concentration