Plasma Membrane and Selective Permeability

What are the structures of a phospholipid

Phosphate Group, Glycerol, Hydrophilic Head, Fatty acid Hydrophobic tails.

Seperates internal cell environment form external environment

Plasma Membrane

What is the plasma membrane primarily composed of

Phospholipids

Phopshpolipids are _____

amphipathic

What does it mean to be amphipathic

Some parts are polar and others are nonpolar

What polarity is the head of a phospholipid

Polar

What polarity are the tails of phospholipids

Nonpolar

What do phospholipids naturally form in H2O based solutions such as the cytosol and extracellular fluid

Bilayers.

The ability of membranes to regulate the substances that enter and exit.

Selective permeability

Were are the hydrophilic heads of a membrane oriented?

Towards the aqueous environment

Hydrophobic tails are oriented towards were?

Away from the aqueous environment

A model to describe structure of cell membranes

Fluid Mosaic

How is the membrane held together?

Weak hydrophobic interactions

What do the hydrophobic interactions of a membrane allow it do?

Move and shift

What three factors effects the fluidity of a membrane

Temperature, Fatty acid tails, and Cholesterol

How does high temperature effect the fluidity of a membrane?

Higher thermal energy leads to more movement in lipids, increasing fluidity, but decreasing the selectiveness of the membrane.

How does cold temperature effect the fluidity of a membrane

Phospholipids move much less and pack tightly together, reducign the fluidity of the membrane.

How do unsaturated fatty acids help maintain fluidity at low temps

Kinked tails prevent tight packing of phosphoilipds.

How does cholesterol maintain fluidity despite temperatures?

It keeps phospholipids together at high temperatures and keeps them apart at low temperatures, keeping the fluidity more constant.

Comprised of many parts

Mosaic

What are the two major categories of proteins in the plasma membrane.

Integral Proteins and Peripheral Proteins

Proteins that embed into the lipid bilayer

Integral proteins

What are integral proteins also known as?

Transmembrane Proteins

What type of polarity are integral proteins?

Amphipathic

Proteins that are not embedded into the lipid bilayer

Peripheral

Peripheral proteins are bonded to what and how?

Loosely bonded to the surface.

Where does an intrinsic peripheral protein face?

Out into the cytoplasm

Where does an extrinsic peripheral protein face?

Out into the extracellular fluid.

What are the two types of membrane Carbohydrates?

Glycolipids, Glycoproteins.

What is the purpose of Glycoproteins and Glycolipids?

Cell-to-cell recognition. AKA cell tags.

Plants have _____ tgat covers their plasma membranes.

Cell wall.

What do cell walls provide?

Extracellular Structure (Not found in animal cells).

What is the purpose of the cell wall.

Shape/Structure, Protection, Minimal regulation of water intake.

What is the cell wall made up of.

Cellulose

What do cell walls contain?

Plasmodesmata

Hole-like structures in the cell wall filled with cytosol and connect adjacent cells.

Plasmodesmata.

Which molecules can easily pass through the cell membrane?

Small, nonpolar, hydrophobic molecules

What are examples of small nonpolar hydrophobic molecules?

Hydrocarbons, CO2, O2, N2

Why are small nonpolar hydrophobic molecules able to traverse cell membranes easily?

They are not repulsed by phospholipid tails.

Which substances have difficult passage or protein assisted passage across the cell membrane

Hydrophilic, Polar molecules, large molecules, ions.

What are examples of difficult passage or protein assisted passage substances

Sugar, water

Why do some substances have difficulty going through membranes?

They are repulsed or have size problems getting through the plasma mebrane.

What are the two types of membrane transport

Passive and active.

Transport of a molecule that does not require energy from the cell.

Passive transport

Why is passive transport passive?

Because a solute is moving with its concentration or electrochemical gradient.

What is passive transport involved in?

Import of materials and export of waste.

What are the three types of passive transport?

Diffusion, Osmosis, Facilitate diffusion

Spontaneous process resulting from the constant movement of molecules

Diffusion

What is the direction of diffusion

High to low concentration gradient

What is diffusion also known as?

Moving down the concentration gradient

MOlecules diffuse acrross

The direct membrane

Different molecules have different _____

rates of diffusion.

Even with diffusion the membrane is still ______

Selectively permeable

The diffusion of water down its concentration across a selectively permeable membrane.

Osmosis

Diffusion of water from areas of low solute concentraton to areas of high solute concentration

Osmosis

Diffusion of molecules through special proteins

Facilitated Diffusion

What are the names of the proteins involved in faciliated diffusion?

Transport proteins.

Faciliated diffusion increases the rate of diffusion for what?

Small ions, water, carbohydrates

What are the two categories of transport proteins?

Channel and Carrier

Each transport protein is ________ for substances it can facilitate movement for

Specific.