Advanced Cell Biology

2014 1nd Semester

Department of Animal Science

Chungbuk National University

4nd Lecture

1st week : Introduction

3rd week :Research Strategies For Cell Biology

5nd week : Nucleus, Transcription and Splicing

7nd week : Membrane and Channel

9nd week : Membrane Trafficking

11nd week : Cell Signaling

13nd week : Cytoskeleton

15nd week : Cell Cycle

Membrane

- Barrier between each cell and its environment

- Partition of the cytoplasm into compartments

* Nucleus* organelles

- All biological membranes have much in common

• Fluid bilayer of lipid molecules• Integral membrane proteins• Pheripheral membrane proteins

Development of Ideas about Membrane Structure

“ Fluid Mosaic Model” of biological Membrane

Lipids : Framework of biological membrane

Hydrophilic (Water lovers )

Hydrophobic (Water haters)

Phosphoglycerides

• Main lipid constitutes of membranes• Glycerol + two fatty acids + phosphoric acids + alchohol

• Depend on alcohols esterified to the phosphates

- Phosphatidic acid [PA]

- Phosphatidylglycerol [PG]

- Phosphatidiylethanolamine [PE]

- Phosphatidylcholine [PC]

- Phosphatidylserine [PS]

- Phophatidylinositol [PI]

Sphingolipid : N-containing charge head

Cholresterol is the essential component of biological membrane

Cholresterol give ‘rigidity’ in membrane, therefore help to maintain integrity

Lipid rafts

Sphingolipids and cholestrol form small islands (50nm)Involved in signalings

Integral Membrane Proteins

Transmembrane segment

- Mostly alpha-Helix- Hydrophobics

Hydrophaty Plots

Plot based on the hydrophobility of amino acids in a protein

C-terminal isoprenoid

N-terminal myristoyl tail

Membrane Potential (Ion-gradient as energy)

Pump : enzymes that utilize energy from ATP or light or other sources to movie ions and other solutes across membranes

- Formation of gradients expense of chemical energy- Convert chemical energy to electric energy

Carrier : enzyme-like proteins provide passive pathway for solute to move across membranes

- From higher concentration and lower concentration- Carriers uses ion gradient as a source of energy

Channel : ion-specific pores which can open and close transiently

- Channel open : ion passes quickly across membrane- Channel close : stop- Movement of ions through channel is basis of control of electric potential across mebrane

Light-driven Proton Pump : Bacteriorodopsin

Convert Light energy as chemical energy (Formation of proton gradients)

Mitocondrial F1 ATPase (ATP Synthase)

P-Type Cation Pumps : Ca2+-ATPase (SERCA1)

Ca2+ acts as important second messenger in cells

Therefore, Ca2+ concentrations should be

Pumps Ca2+ out of cytoplasm into the endoplasmic reticulum

Carrier : enzyme-like proteins provide passive pathway for solute to move across membranes

- From higher concentration and lower concentration- Carriers uses ion gradient as a source of energy

- Uniproters

GLUT carrier for glucose

- Antiporters

Driving ion moves in one direction, then drive substrate in the others

- Symporters

ion and substrates goes to the same directions

Channels

Channel : integral membrane proteins with transmembrane pores that allow particular ions or small molecules

Selectivity filter of Ion Channel

Potassium (K+) channel should allow pass-through of Potassium, but Sodium

Voltage-gated K+ Channel

- voltage-gated K+ and Na+ channels produce action potentials in excitable cells

Nature 2013EM reconstitution of TRPV1

Ion Channel Gated by Extracellular Ligands

Glutamate Receptor

Aquaporin (Water Channel)

Xenopus oocyte injected by Aquaporin cRNA

Cooperation of Channel, Pump and Carrier in Cell

1. Chemical Energy from ATP was converted as concentration gradients of C+

2. Carrier uses electrochemical gradient of C+ to drive transport C+ and S

Epithelial Transport