생리학 ( 生理學 , Physiology)

• General Physiology

• Organ Physiology

• Integrative Physiology

Physics (P

hysical Chem

istry, B

iophysics)

Claude Bernard: 내환경의 항상성 (Homeostasis) ----- 온도 , 삼투압 , pH,

세포외액의 조성을 일정하게 유지하는 기능을 중요시 .

세포

Common molecular mechanisms in all forms of life

• Store genetic information in nucleic acids• Employ proteins to catalyze chemical reactions• Synthesize proteins on ribosomes• Drive energy by breaking down simple sugars• Use ATP as energy currency• Separate cytoplasm from their environment by

means of phospholipid membranes containing pumps, carriers, and channels

세포막• Davson-Danielli 모델 :

두겹의 지방층 안팎으로 연속적인 단백질층 .

• Singer-Nicolson 모델 :구형단백질이 인지질에 끼어 있는 lipid-globular protein mosaic model.

• 2003 년 : 세포막 단백질들의 다양한 기능과 구조가 밝혀져 가고 있음 .

Membrane proteins

• Receptors• Enzymes• Transporters: pump,

carrier, ion channels

세포막을 통한 물질이동• Homeostasis 유지• Electrical signalling (membrane potential)

Membrane Lipid

기능 • framework of biological membrane• cell signalling: hormone, second messenger • 전기적 특성 : 높은 절연성 , 축전능 (1 F/cm2) – 막전압 발생 가능

종류• Phosphoglycerides• Sphingolipids• Cholesterol• Glycolipids

Phosphoglycerides (phospholipids)

구성• 3-carbon backbone of glycerol• 2 long-chain fatty acids esterified

to C1 and C2• phosphoric acid esterified to C3

분류 : Alcohol head group 에 따라 .• Phosphatidylethanolamine• Phosphatidylcholine• Phosphatidylserine• phosphatidylinositol

Lipid asymmetry

Intercellular Junctions4 types, each composed of a different transmembrane protein, connect the plasma membrane of adjacent cells

Molecular components of cell-cell and cell-matrix junctions

Adherens junctions and desmosomes

• Adherens junctions (zonula adherens): cadherins anchored to actin filaments.

• Desmosomes (macular adherens): cadherins anchored to intermediate filaments.

Tight junctions (zonula occludens)• Occlude the extracellular space between epithelial cells, formin

g a tight, belt-like seal that limits diffusion of water, ions, and solutes (larger than 1.8 nm).

Tight junctions

• Tightness of the seal, reflected in electrial resistance, varies depending on cell type (extremely tight in frog skin; leaky in blood vessel); regulated by hormones (ADH, cytokines).

• Define the boundary between apical and basolateral membranes: two surfaces differ in lipid and protein compositions and functions.

Gap junctions

• Two ways of intercellular communications: 1) by secreting chemical messengers; 2) direct communication by gap jucntion (electrical synapse).

• Connexins: proteins with 4 transmembrane helices

• Connexon: half channel in each membrane, made by lateral association of 6 connexins

• Each connexon pairs with a connexon from the adjacent cell, forming a gap junction

Gap junction channels

• 10 nm long/1,2 nm diameter; size filter up to 1kD

• pass ions to establish electrochemical continuity (electrical synapse); second messengers to establish common network of information; and metabolites to allow sharing of resources

• Conductance: 30 to 300 pS• Open/close is regulated by trans

junctional potential, cytoplasmic Ca2+, pH, cAMP-protein kinase.

• Gap junction closing -- terminates communication with neighboring cells that are damaged or metabolically compromised.

Body Fluid Compartment

모세혈관을 통한물질이동 세포막을 통한물질이동