Material transport

The process of material transmembrane movement

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Material transport refers to the process of material moving across the membrane.

Chinese name: Material transport
Definition: The process of material transmembrane movement

Diffusive flux: Mmol/s.cm2
Substance transported: O2　，CO2

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Simple diffusion

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Diffusion flux: Mmol/s.cm2

Influencing factors: concentration difference of substances inside and outside the membrane, voltage difference, membrane permeability

Materials transferred: O2, CO2

Features: ① High concentration → low concentration

② No energy consumption

Facilitating diffusion

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1. Definitions

Non fat soluble small molecular substances Membrane protein With the help of, the process of transferring from high concentration to low concentration.

2. Features

① High concentration → low concentration

② No energy consumption

③ Selectivity

④ Permeability can be changed

3. Channel mediated facilitated diffusion -- ion channel

① Materials transported: ions: Na+, K+, etc

② Features:

a. Channel protein functional status can be changed (Fig.)

Activate (Open), Deactivate (Close), Standby (Rest)

b. Regulation through "gate"

c. Selectivity

③ Transfer result: electrochemical potential energy balance

Classification:

Chemical gated channel : N-Ach receptor

Voltage gated channel : Na+channel, mechanical gating channel

4. Carrier mediated facilitated diffusion (Fig.)

Transported substances: GS, AA enter general cells

Common features: ① structure specificity, ② saturation, ③ competitive inhibition

Active transshipment

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1. Definition: refers to cell membrane The process of transporting material molecules (or ions) against concentration difference and potential difference

2. Biological pump: essentially ATPase, such as "sodium potassium pump", "proton pump", etc

Sodium pump: sodium potassium pump or Na+- K+- ATPase (figure)

Activation: intracellular [Na+], extracellular [K+]

Function: 3 Na+move out of the membrane, 2 K+move into the cell

Physiological function: forming extracellular high Na+and intracellular high K+

a. Ion potential energy storage is the basis of bioelectricity generation; Promote the transmembrane transport of some substances against the concentration difference. E.g. GS

b. Intracellular high K+is necessary for some biochemical reactions

c. Prevent cell edema

3. Classification

Primary active transport

Secondary active transport: (figure) co transport and reverse transport

Characteristics of various transmembrane transport mechanisms