1.3 & 1.4-Cell Membrane

Hydrophobic (non-polar)

hates water, repel water (the non-polar tails)

Hydrophilic (polar)

loves water, interacts well with it (the polar head)

Cholesterol

-Besides phospholipids and proteins, animal cell membranes also contain cholesterol -Cholesterol is a steroid (lipid that is not a fat or oil) and is mostly hydrophobic but has one hydrophilic hydroxyl group -Cholesterol plays a role in... --Fluidity: cool temperatures maintain fluidity to prevent tight packaging --Restriction: at warm temps, cholesterol restricts movement (pillar of strength)

Problems with the Sandwich Model (Davson-Danielli) -Protein -Hydrophilic zone -Hydrophobic zone -Hydrophilic zone -Protein

-Freeze-etched electron micrographs led to discovery of transmembrane proteins, which went against the Davson-Danielli model -Structure of membrane proteins, new technology allowed scientists to extract proteins and they were found to be irregularly shaped

Membrane Proteins

-the primary function of the cell membrane is to form a barrier through which ions and hydrophilic molecules cannot easily pass --done primarily by the phospholipid bilayer -All other jobs are carried out by membrane proteins --integral proteins~span the membrane, go through the entire membrane --peripheral proteins~are bound to the outer edges of the membrane -Functions of membrane proteins (TEACAR) --Transportation (integral) --Enzymatic Activity --Adhesion (cell-cell) --Communication (cell-cell [sugar-ID card]) --Attaching the cytoskeleton & the ECM (extracellular matrix) --Receptor Proteins

Explain the difference between Carrier and Channel proteins

Carrier- Undergo a subtle change in shape to transport materials (cooty-catcher analogy) Channel- Ion channels open/close in response to a stimulus (gated channels and aquaporins)

Define Endo- and Exo- cytosis

Endo- enters the content into the vesicle Exo- exits the content into the vesicle

How are vesicles formed? (Endo- and Exo-)

Endo- the cell takes in macromolecules by forming vesicles from the plasma membrane, reduces surface area Exo- transport vesicles migrate to their membrane, fuse with it, and release their content, increase cell membrane SA

Describe dynamic equalibrium

Equal concentration of particles on both parts of a membrane

Describe Hyper- Hypo- and Iso- tonic solutions (what happens to the cell)

Hyper- solute concentration is greater outside than that on the inside of the cell (the cell loses water) Hypo- solute concentration is greater inside than that on the outside of the cell (the cell gains water) Iso- solute concentration is the same on the outside and inside of the cell (no net water movement)

What happens to a cell (animal/plant) when it is in a (hypertonic/hypotonic/isotonic) solution

Hypertonic (A)- Shriveled Hypotonic (A)- Lysed Isotonic (A)- Normal (ideal) Hypertonic (P)- Plasmolyzed Hypotonic (P)- Turgid (ideal) Isotonic (P)- Flaccid

BE ABLE TO DRAW THE STRUCTURE OF THE PLASMA MEMBRANE

INCLUDE INTEGRAL AND PERIPHERAL PROTEINS, CHOLESTEROL, and the PHOSPHOLIPID BILAYER

Why is our current model of the plasma membrane called a fluid mosaic? (The Singer-Nicolson Model)

It is called that because it has the consistency of oil and has many different components to it

Define Diffusion

Molecules following their concentration gradient (high -> low), smaller non-polar molecules slipping through the phospholipids

Define Active Transport

Moves substances against their concentration gradient, requires energy (ATP), performed by specific protein pumps (integral) embedded in the plasma membrane (typically used for large/non-polar molecules BUT if it goes against the concentration gradient...ACTIVE!!!)

KNOW THE DIFFERENT PASSIVE VS ACTIVE TRANSPORTS

Quick fact: aquaporins-water channel proteins

Define Vesicle (used for Bulk Transport)

Sphere of phospholipid, mini bilayer, formed in the Rough Endoplasmic Reticulum and the Golgi Apparatus for export

Define Osmoregulation

The control of water balance (specifically done in the kidneys for humans)

What is a concentration gradient?

The difference in the amount of particles on either side of a barrier and the will of the particles to balance the amount on both barrier sides

Define Tonicity

The strength of a solution in relationship to osmosis, ability of a solution to cause a cell to gain or lose water

Define Osmolarity

Total concentration of osmotically active solutes

Define Facilitated Diffusion

Uses transport proteins to move molecules down the concentration gradient (STILL PASSIVE TRANSPORT)

Define Osmosis

a form of diffusion, where water moves towards the higher concentration to dilute it (solute [gets dissolved] vs solvent [does the dissolving])

Amphipathic

molecules with both hydrophilic and hydrophobic regions