生理学英文课件(细胞)Basic Function of the Cell

1) Extrinsic protein (peripheral protein) To attach only to one surface of the membrane, and do not penetrate. Function: almost entirely as enzyme
Intrinsic protein (integral protein)

The molecules move concentration to low one.
from
higher

This continual movement of molecule among one another in liquid, or in gases, is called diffusion.
Facilitated diffusion (易化扩散)

carrier – mediated diffusion need a specific carrier protein helping it to do so

Characteristic of facilitated diffusion
Functions of membrane proteins
① structural elements (commisure protein)
② enzyme ③ receptor ④ transporter: channel and carrier
Membrane carbohydrates


These differences are important to the life of the cell <1> Chemical components and Molecular structure of the Cell Membrane
(1) Fluid- mosaic Model The cell membrane and membranes of organelles are composed of Lipids and proteins: Protein : Lipid = 4:1 – 1:4 Depending on the functional activities of membranes

Diffusion depends on concentration difference and potential difference, without the necessity of supplying energy, called passive transport.
Simply diffusion
a lipid bilayer

1890, Overton, cell membranes have higher permeability to fatty – soluble substances. Suggesting : cell membrane is composed of lipid. 1925, Gorter and Grender Based on the experimental results about area of the red blood cells, believed the membrane Lipids were arranged in a bilayer manner

A simple physic diffusion without the necessity of bind with carrier proteins in the membrane.
Characteristics of simple diffusion
① Only fat-soluble substances (O2 CO2 NO etc.) can diffuse through the lipid bilayer in the membrane



Golgi apparatus (高尔基体)

Lysome (溶酶体)： digest aging or damage structures Microtuble(微管)


The components of cytoplasma: Water: 80% Protein: 14% Lipid: 2% Others: 4%
Transport of substances through the membrane

Passive transport (被动转运)
All molecules and ions in the body fluid are in constant motion. The greater the motion is, the higher the temperature will become.

① many of them give most cells an overall negative surface charge (repels other negative objects ② glycocalyx (糖蛋白结合复合物) attaching cells one to another ③ act as receptor substances for binding hormones (insulin) ④ some carbohydrate moieties enter into immune reactions
Section I

Transport of Substances through the Cell Membrane
The chemical compositions of extracellular fluid are different from those of intracellular fluid

The phosphate end of phospholipids is soluble in water (hydrophilic), and the fatty acid portion is soluble only in fat (hydrophobic), so, the hydrophilic ends cover the surface in contact with the surrounding water; the hydrophobic ends are mutually attracted to each other, line up in the center of membrane .


Review the basic structure of Cell
Cell membrane protoplasm :water etc. cytoplasma Organelle: Mitochondria etc. Nuclear membrane Neucleus Neucleolus : Contain RNA, DNA

Fluid mosaic model


1972, Singer and Nicholson Main point: a lipid bilay as the frame of cell membrane; Interspersed in a lipid bilayer are larger globular protein molecules.
② diffusion is a passive process, needn’t energy
③the rate of diffusion is determined by the concentration difference (concentration gradient), the velocity of kinetic motion, the number and size of openings in the cell membrane through which the molecules or ions can move, by the potential difference for ions ④ the time for diffusion is direct proportion to square of diffusion distance
Compositions of lipids of cell membrane
Phospholipid > 70% Cholesterol < 30% Sphingolipid glyclipid

Membrane proteins

A. Types of membrane proteins
cell
Mitochondria : provide energy, ATP
Endoplasmic reticulum

rough endoplasmic reticulum: contains ribosome (核蛋白体) related to protein synthesis
smooth endoplasmic reticulum related to production of lipid and glucose
Occur almost in combination with proteins or lipids to form glycoproteins or glycolipids. The carbohydrate moieties attached to the outer surface of the cell have following functions:
Extracellular fluid Na+ K+ ClPhosphates 142 mEg/L 4 mEg/L 103 mEg/L 4 mEg/L Intracellular fluid 10 mEg/L 140 mEg/L 4 mEg/L 75 mEg/L
Proteins
5 mEg/L
40 mEg/L

Compositions of cell membrane:
Protein 55% Other lipids 4% Phospholipid 25% Carbohydrates 3% Chlesterol 13%
Lipid barrier of the cell membrane prevents water penetration
Chapter 2.
Basic Function of the Cell
2012年9月2日星期日
Fra Baidu bibliotek
There are about 100 trillion (万亿) cells in a human being ( red blood cells about 25 trillion).
Each of 100 trillion is a living structure that can survive and reproduce itself. If to understand the function of organs and other structures of the body, it is essential that we first understand the basic organization of the cell and the function of its component parts.

To penetrate all the way through membrane

Function: ① provide structural channels for water molecules, water-soluble substances especially ions; ② act as carrier proteins for transporting substances not penetrating the lipid bilayer; ③ act as enzymes