세포막은?     1. Unit Membrane Hypothesis - "all membranes look alike*"                         photomicrographs:          EM*       SEM*       2. Source for study (plasma membrane - RBC ghosts)                                    RBC-bw*,  RBC-color  and   RBC ghosts*           Two Ways to Study Membranes & Transport of Solutes      a.  NATURE OF MEMBRANE ITSELF             - "its Molecular Makeup"      b.  PERMEABILITY STUDIES            - "Physiological Properties of Membranes

This discussion will focus on selected examples of transport catalysts for which structure/function relationships are relatively well understood. Transporters are of two general classes: carriers and channels. These are exemplified by two ionophores (ion carriers produced by microorganisms): valinomycin (a carrier) gramicidin (a channel).

세포막 현미경 사진

적혈구

내용물이 빠진 적혈구 막

적혈구 막 현미경 구조

적혈구막 성분 분리 장치

세포막에 부착된 당단백질

운반체 단백질의 분류 Uniport (facilitated diffusion) carriers mediate transport of a single solute. An example is the GLUT1 glucose carrier. The ionophore valinomycin is also a uniport carrier.

유동모자이크모델 1. lipids = mostly phospholipids* & cholesterol*                               lipid fluidity - viscous vs. fluid* 2.  proteins  =          a)  Integral (intrinsic) proteins  -  denatured upon release      b)  Peripheral (extrinsic)            -  easily extractable    Structural Models... (a historical look at membrane structures)           troughs*                   bilayer model*            Davson-Danielli model* Singer-Nicolson model*  = glycoproteins secreted by cell = a cell "wall“ Fluid Mosaic model* & Extra-cellular Matrix*common to animal cells     Functions of Membrane Proteins *

세포막 모델의 변천

유동모자이크모델 The membrane is composed of a phospholipid bilayer in which proteins are embedded. The hydrophilic heads of phospholipids are part of both the outside surface and the inside surface of the membrane. The hydrophobic tails make up the interior of the membrane. Note the plasma membrane’s asymmetry – carbohydrate chains are attached to the outside surface, and cytoskeleton filaments are attached to the inside surface.

유동모자이크모델

세포막 인지질 배열 모습

인지질 배열

세포막의 통로

Gas exchange in lungs occurs by diffusion Oxygen diffuses from the alveoli into the capillaries because there is a higher concentration of oxygen in the alveoli than in the blood of the capillaries.

저장액 속의 동물과 식물세포 In hypotonic solution, a cell gains water. The animal cell may undergo lysis (burst). In the plant cell, vacuoles fill with water, turgor pressure develops, and chloroplasts are seen next to the cell wall.

삼투

용액의 농도에 따른 삼투 현상

식물과 동물 세포의 삼투 비교

물 분자 이동 통로

물 분자 전용 통로 구조 모습

용질이 막을 통하는 방법은? 1. through a PORE* ..proteins embedded in bilayers* allows ions & small hydrophilics  to move through  a pore 2.   by DISSOLVING IN* membrane...   hydrophobic solutes via bilayer 3.   by CARRIER PROTEINS* ...       proteins embedded in membrane w specificity for a solute      results in transport of solute through a lipid bilayer by diffusion 4.   by membranes ENGULFING particles* into membrane vesicles...       ENDOCYTOSIS-phagocytosis  (forms a phagosome - solid)       &  pinocytosis (makes a liquid vesicle)       EXOCYTOSIS    -  export vesicles  

세포막을 통해 분자들은 어떻게 이동하는가? The small, curved arrows indicate that these structures cannot cross the plasma membrane, and the large arrows indicate that these substances can cross the plasma membrane.

세포막을 통한 물질 수송

물질 수송 방식

물질 수송

용질에 따른 막 투과도

물질 수송 방식

단백질을 통한 물질 수송 Alternates between two conformations so that the solute binding site is sequentially accessible on one side of the bilayer and then the other

운반체 단백질을 통한 물질 수송

물질수송을 전담하는 단백질 모습

막 단백질의 구조와 배열                                                 Membrane Proteins figure  - proteins are amphipathic  containing hydrophilic & hydrophobic aa's   figure  - amphipathic proteins   can integrate into membrane bilayers                                          a

세포막의 역동적 연속성

개폐형 채널 단백질 작동 과정

포도당 이동 과정

Na-K 펌프

Na-K 펌프

양성자 펌프

설탕 이동 과정

융모에서 양분 이동 과정

양분 이동 과정

식세포 Phagocytosis occurs when the substance to be transported into the cell is large; amoebas ingest food by phagocytosis. Certain types of human white blood cells are amoeboid and engulf worn-out cellular debris or bacteria using phagocytosis. When an endocytic vesicle fuses with a lysosome, digestion of the vesicle contents occurs.

식세포 Pinocytosis occurs when a macromolecule, such as a polypeptide, is to be transported into the cell. The resulting vesicle or vacuole is small. Pinocytosis occurs continuously, but the loss of plasma membrane due to vesicle formation is offset by exocytosis.

식세포

음세포