1. Phosphate

2. Carbon

What are the major functions of Cell Membrane Proteins?

(6)

1. Transport

2. Recognition

3. Signal Reception

4. Attachment

5. Generation of Electrical Potentials

6. Membrane-Attached Enzymes

1. Protein Pores & [Gated] Channels, which are water-filled channels

2. Carrier Proteins (which are essentially transporters), and are sometimes coupled to...

3. Na+/K+ ATPase Enzyme proteins (for active transport across membrane)

Describe the Major Function of Cell Membrane Proteins: Recognition (2)

What is Recognition important for?

1. Surface Glycoproteins as Markers for "self & non-self antigens"

2. Antigen-Recognition Receptors on immune cells

Recognition is important in immunology and development

1. Protein Junctions attach cell to cell

2. Adhesion Proteins stick cell to surface for crawling (wbs's), anchoring (tendon to bone), association of cells into tissues

Describe the Major Function of Cell Membrane Proteins:

Generation of Electrical Potentials

1. Proteins

2. Amino Acids

3. Peptide Bonds

How many different amino acids are used in human proteins?

How many amino acids can plants have up to?

21

26

1.What is is called when several proteins bind together to form a single large assembly?

2.Within this assembly, each protein component is then called what?

1. Multimeric Protein

2. Sub-unit

1. Phosphate

2. Glycerol

3. Alcohols

1.Substance move by lipid solubility through the phospholipid bilayer

2. Substance moves through water-filled pores (=channels)

3. Substance moves by carrier proteins in membrane ("Facilitated Diffusion" or "Carrier-mediated passive transport")

Pores or channels are transmembrane proteins that have a lipophilic exterior and a hydrophilic core to transport small water-soluble molecules or ions.

H+ ion, K+ ion, Cl- ion, urea, WATER (small ions or small molecules)

These are transmembrane proteins with a lipophilic exterior and a hydrophilic core with one or more "pockets" which carry larger, water-soluble molecules. The carrier protein pocket -- binding sites-- are specific for the substances carried.

Glucose, other simple sugars, amino acids, and nucleic acids

1. Passive Transport does not require added energy

2. The membrane must be selectively permeable to a given substance.

3. Molecules may move in both directions during passive trasport; i.e. passive transport is bidirectional.

4. Molecule, ions, or atoms always move from higher concentration to lower concentration,  if the outside=inside, there is no net movement of particle.

5. The movement of each species of particle by passive transport is considered separately.

6. The rate of passive diffusion of a particular substance is proportional to the permeability factor and to the difference in concentrations on each side of a membrane.

Not permeable

Review page 6

1. Passive

2. Membrane Pores

1. Osmoles per liter of solution

2. Osmolarity

Look at p. 7

1. less

2. swell

* Because there is more particles on the outside of the cell, and therefore a higher [H₂O] on the outside, the H₂O will move into the cell from [high] to [low] and cause the cell to swell. 

1. greater

2. Shrink

* Because there is a greater [dissolved particles] in solution, the solution will have a lower [H₂O]. Therefore, H₂O from the cell will diffuse into the solution, causing the cell to shrink.

When a solution is Hypotonic, there is less water within the cell than outside the cell.

When a solution is Hypertonic, there is more water within the cell than outside the cell.

1. Added energy is required for active transport, and supplied by ATP via an ATPase enzyme.

2. Active transport requires specific carrier proteins couple to an ATPase enzyme

3. Unlike carrier proteins for passive transport, the carrier proteins for active transport are only able to bind and carry the molecule or ion in ONE DIRECTION.

1. Transport of solutes is usually from low concentration to high concentration; uni-directional.

2. The greater the difference in concentration, the greater the energy required to maintain it.

Glucose and other Simple Sugars

Amino Acids

Nucleic Acids

Ca²⁺ ion

Fe³⁺ ion

Na⁺ion

Cl^-ion

K⁺ion

H⁺ion

Glucose

Amino Acids

Ca²⁺ion

HCO₃^-(bicarbonate) ion

1. Na⁺

2. K⁺

3. Na⁺/K⁺ ATPase

"sodium-potassium pumps"

The potential to do electrical work (measured in volts)

The potential flow

The movement of electrical charges (+ or - ions), as they do electrical work (measure in amperes). IN ceels, the electric current is carried by ions instead of electrons. The current is created when separated positive and negative charges come back together.

The actual flow

Inside of the cell becomes more positive relative to the outside.

Look at p. 9

1.Nerve cells (voltage-gated and ligand-gated, Na⁺, Cl^-, Ca²⁺, K⁺channels)

2.Muscle Cells (voltage-gated and ligand-gated Na⁺, K⁺, Ca²⁺channels

3.Fertilized Ovum (gated Ca²⁺ channels)

4.Secretory Cells (gated Ca²⁺ channels)

1. Electrical Potential (measure in volts) is created in living cells by ions and can be used to create electrical current (in amperes)

2. Cell Membranes create electrical potential by separating positive and negative charges (separation of charges)

3. The separation of charges occurs as the result of a) an imbalance in passive transport ions, and b) the rules of electric charges (likes repel; opposites attract)

1. Soma

2. Dendrites

3. Axon

4. Myelin Sheath (some nerves)

5. Synapses & Chemical Transmitters

1. Motors nerves from the central nervous system to muscles

2. Sensory nerves from sensory receptors to the central nervous system

3. Interneurons, which have their processes (axons and dendrites) entirely within the CNS

What is the E_m of a :

1. Red Blood Cell

2. Motor Nerve

3. Skeletal Muscle

1. -10 mV

2. -80 mV

3. -50 mV

The resting potential is due to the movement of what ion?

Why?

Potassium ion

Potassium ions are actively pumped into the cell, so that the inside of potassium concentration is about 20x higher than outside potassium, and it leaks out again through potassium channels by passive transport.

1. Negative

2. -10 mV inside Red Blood Cells

3. -90 mV inside some muscle cells

1) Chemical stimulations by neruotransmitters such as ACh, E, NE, DA, glutamine, GABA, and many others

2) Electrical stimulation by the "shock" of a nearby action potential, or an artificial electric shock.

3) Physical stretching of nerve membrane, pressure, or high temperature.

How is propagation achieved?

What is propagation similar to?

By re-forming new action potentials along the length of the axon or muscle membrane.

A "chain-reaction"-- each action potentials acts as stimulus for the next action potential; each depolarization from one sodium cycle stimulates adjacent membrane sodium channels to open.

1. Big

2. Smaller

Node-to-node

100x

1. Oligodendrocytes

2. Schwann Cells

1. Multiple Sclerosis (MS)

2. Amyotrophic lateral sclerosis (ALS; Lou Gehrig's disease)

Motor nerves

Motor-end plates or myoneural junctions

Chemical (90-95% of total)

Electrical (5-10% of total, all in the CNS)

What is the process of the creation of the transmitter substance in chemical synapses?

What is the time involved in this process?

What is this process called?

It has been synthesized in the presynaptic nerve cell body, packaged in membrane vesicles, and transported to the nerve endings.

0.5 msec per synapse

Synaptic delay

a) nerve ---------------------> nerve

b) motor nerve -------------------------> muscle

c) neruosecretory nerve -------------------> capillary

a) chemical transmitter

b) chemical transmitter

c) hormone

Cells to be electrically connected, or electrically-coupled.

There is no synaptic delay and action potentials can travel both ways.

1. Action potential reaches synapse

2. Fusion and release of transmitter vesicles (require Ca²⁺ion, ATP, and ATPase enzyme)

3. Binding of transmitter chemical to post synaptic receptor membrane protein

4. Turning "on": opening of transmitter-gated channels

5. Turning "off" requires either a) transmitter inactivation or breakdown, at postsynaptic membrane (e.g. motor end-plate and ACh) or b) transmitter re-uptake by presynaptic ending (e.g. serotonin, dopamine) Reuptake blocker: SRI's block serotoninreuptake; cocaine blocks dopamine reuptake

What occurs at the gated-channels once turned "on"

Na⁺in

K⁺ out

Cl^-in

if Na⁺ Channels open ------> depolarization (+) (excitatory)

if K⁺ channels open -----> hyperpolarization (--) (inhibitory)

if Cl^- channels open -----> hyperpolarization (--) (inhibitory)