Cell Membrane + passive transport

roles of the cell membrane

´Create a physical barrier between the inside of the cell and the external environment (extracellular space).

´Regulate the passage of materials into and out of the cell.

´Sensitive to the external environment and has receptors to detect changes.

´Provide support: the membrane is attached to the microfilaments of the cytoskeleton.

what type of membrane does the cell membrane have? what does this result in?

• it is semi- permeable

• the cell membrane is fatty, thus water-soluble molecule substances will not pass through (except carbon dioxide and oxygen)

Structure of the phospholipid bilayer

• 55% of weight is proteins

  • carrier, channel, cell-identity markers, glycoprotein

• phospholipid molecules

Channel proteins

• ion channels

• open channels that carry out simple diffusion

Carrier proteins

• channels that carry out facilitated diffusion and active transport

What is the fluid mosaic model?

currently accepted model of the cell membrane

• fluid= the molecules of which it is made is constantly moving

• mosaic= representing how the cell membrane is made up of many parts

What are the requirements of a cell?

• a stable environment

• a constant supply / removal of materials

homestasis

• body systems working together to make sure that the cell and body environment is kept stable and constant

• To carry out functions, certain substances need to be taken in from the extracellular environment and waste must be removed

Active transport

• a form of transport that requires energy to take place. It often moves against the concentration gradient, from low to high

Carrier Mediated Transport

a form of transport that can be either active or passive.

• proteons in the cell membrane allow molecules to be tranported across the membrane.

passive transport

a form of cellular tranpsort which does not require energy to take place. it moves with the concentration gradient, from high to low.

diffusion + examples

the passive transport of gas and liquid molecules from an area of high to an area of low concentration.

carbon dioxide, water, oxygen, ions such as sodium, potassium and calcium, lipids and alcohols

Facilitated Diffusion

water soluble molecules pass through this pathway, VIA the channel protein

Osmosis

the passive transport of water across a differentially permeable membrane, from an area of high to an area of low concentration.

osmotic pressure

the measure of the tendency of a solution to take in water by osmosis

tonicity

the concentration of a solution as compared to another solution. It is a measure of the effective osmotic pressure gradient

isotonic

the concentration of a solution being the same as the inside of an RBC

hypotonic

the concentration of a solution is lower than an RBC

hypertonic

the concentration of the solution is higher than an RBC

Crenation

´If a living cell is placed in a hyper-tonic solution (higher solute concentration than the cytoplasm), the cell will LOSE water as a result of osmosis.

´The cell will “shrivel.”

Lysis

´cell is placed in a Hypo-tonic solution (solute concentration lower than the cells cytoplasm), water will enter the cell by Osmosis.

´Eventually the cell will expand and explode = lyse