Notes: Plasma Membrane pages 19 – 24

Fluid Mosaic ModelPlasma Membrane Anatomy

(Structure)

Function – regulates what goes in and out of the cell and holds the cell together.

Fluid Mosaic ModelPlasma Membrane Anatomy (Structure)

Structure - cell membrane is a phospholipid bilayer.

Fluid Mosaic ModelPlasma Membrane Anatomy (Structure)

What does that mean?

• it is bilayer – double layered

•the layers are composed primarily of a fat molecule (lipids) with one fatty acid replaced by a phosphate group

•if it dissociates it is easy for it to reform which also allows it to grow

Result of this anatomy of phospholipid bilayer is:

•plasma membrane has polar heads and nonpolar tails

http://www.ccs.k12.in.us/chsteachers/Amayhew/Biology%20Notes/transport%20notes_files/image001.gif

Result of this anatomy of phospholipid bilayer is:

• polar meaning water loving (hydrophilic)

• phosphate heads orient themselves towards the cytoplasm and extracellular fluids(fluids on outside of cell which contain water)

Result of this anatomy of phospholipid bilayer is:

•nonpolar meaning water hating (hydrophobic)

•lipid tails have an attraction for each other and orient themselves towards each other in the middle of the bilayer

Resulting in something like this:

Molecules found in plasma membrane:

1. Phospholipids – make up bilayer

Molecules found in plasma membrane:

2. Proteins float in the middle of the bilayerthere are three types

Molecules found in plasma membrane:2. Proteins

A. Channel proteins • protrude both sides• have channels through them thatlet things in and out

http://kentsimmons.uwinnipeg.ca/cm1504/Image133.gif

Molecules found in plasma membrane:

2. Proteins B. Glycoproteins - exterior

• composed of sugar and protein• used as markers for recognition

http://www.ideacenter.org/stuff/contentmgr/files/e27b080d92450837e43d44bf73780847/misc/glycoprotein.jpg

Molecules found in plasma membrane:

2. Proteins

C. Receptor proteins • receive messages by chemical means

from other cells• example type II diabetes

http://www.scq.ubc.ca/wp-content/uploads/2006/07/transduction.gif

Molecules found in plasma membrane:3. Cholesterol • composes 1/3 of layer• is nonpolar so found in middle• gives firmness to layer

http://www.uic.edu/classes/bios/bios100/lectf03am/cholesterol.jpg http://www.google.com/imgres?imgurl=http://people.csail.mit.edu/seneff/lipid_bilayer.jpg&imgrefurl=http://people.csail.mit.edu/seneff/statins_muscle_damage_heart_failure.html&usg=__tynxmR7yVcergl7D7HFAcPw8JnU=&h=375&w=449&sz=235&hl=en&start=5&sig2=NM3aH4MfKIzJCIJwCedN3A&um=1&itbs=1&tbnid=uMO9ybETB6CyuM:&tbnh=106&tbnw=127&prev=/images%3Fq%3Dcholesterol%2Bin%2Bplasma%2Bmembrane%26um%3D1%26hl%3Den%26rlz%3D1T4GZHY_enUS231US231%26tbs%3Disch:1&ei=s4MsTNb5I5GTkAXVgfWYCw

Membrane Transport

Physiology (functions) of plasma membrane

delimits cell – holds it together

provides receptors -sense the environment receiving messages

controls what moves in and out of the cell or selective permeability

Selective permeability – ability to let certain materials in or out while restricting others.

Membrane Transport

Membrane Transport – movement of substance into and out of the cell

Membrane Transport

There are two basic types of transport in the cells:

1. Passive transport and 2. Active transport

Membrane Transport

1. Passive transport

No energy is required includes diffusion, osmosis, and

facilitated or mediated transport

Passive Transport Processes

DiffusionParticles tend to distribute themselves evenly

Movement is from high concentration to low concentration,

or down a concentration gradient

Passive Transport Processes

Types of diffusion in the plasma membrane

A. Simple diffusion

unassisted process

solutes are lipid-soluble materials or small enough to pass through membrane pores

Types of diffusion in the plasma membrane

1. Simple diffusion

Remember most of membrane is lipid (nonpolar) and nonpolars dissolve nonpolars so fat molecules move easily through membrane

Types of diffusion in the plasma membrane

A. Simple diffusion

B. Osmosis simple diffusion of water Highly polar water easily

crosses the plasma membrane

Types of diffusion in the plasma membrane

A. Simple diffusionB. Osmosis

C. Facilitated/Mediated diffusion/transport

Substances require a carrier protein for passive transport

Carrier protein accepts a certain shaped molecule

Diffusion through the Plasma Membrane

Types of diffusion in the plasma membrane

A. Simple diffusionB. Osmosis C. Facilitated/Mediated diffusion/transport

3 conditions for regulating mediated transport:

i. Specificity – made for specific molecule

ii. Competition – similar shapes compete for same carrier, greater concentration wins

iii. Saturation – all carriers are full

Membrane TransportThere are two basic types of transport in the cells:

1. Passive transport

2. Active transport

The cell must provide metabolic energy

includes large non-lipid soluble molecules and the use of the sodium-potassium pump

Membrane TransportThere are two basic types of transport in the cells:

1. Passive transport2. Active transport

Metabolic energy comes from the molecule abbreviated ATP

ATP = Adenosine Triphosphate

Energy released when ATP looses a phosphate group and becomes ADP

Types of Active Transport

A. Pump – carrier protein will grab molecule and pump it against the concentration gradient (low to high)

Example: Sodium Potassium Pump

Types of Active Transport

B. Endocytosis – the process by which large molecules are taken into the cell

Types of Active Transport

Types of Endocytosis

i. Pinocytosis Means “water drinking” A mechanism by which cells

ingest extracellular fluid and its contents (proteins)

Membrane pinches to form vesicle containing protein

Pinocytosis

i

http://upload.wikimedia.org/wikipedia/commons/b/b7/Pinocytosis.svg

Types of Active Transport

Types of Endocytosis

ii. Phagocytosis Means “cell eating” The engulfing of microorganisms

or other cells and foreign particles

Not all cells can do this Most common in body are

white blood cells – defense

Phagocytosis

Types of Active Transport

C. Exocytosis the transportation of material from inside the cell to outside the cellGolgi apparatus plays a part

Exocytosis