Movement Across Membranes, Summaries of Biology

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Movement Across Membranes

Diffusion

• passive transport -move from an area of high to low concentration of molecules -no energy is involved
• as a result of thermal Energy, molecules will diffuse in accordance with the concentration gradient

Animation of Passive Transport

https://youtu.be/PRi6uHDKeW

osmosis

PROTEIN CARRIER-ASSISTED TRANSPORT

Only the smallest molecules such as H 2 O,

CO 2 , and O 2 can diffuse freely into an out of

cells. Larger more charged molecules such as

sugar and salt ions require active transport

across the membrane.

Transport (Carrier) Proteins

1. Specialized for the solute it transports

2. Specific binding site

3. Carrier proteins can be inhibited

4. Speed the transport of molecules across a

membrane

Active Transport

⚫ Transporting substances against a

concentration gradient

⚫ Requires ENERGY

⚫ Carried out by specific proteins inserted in the

membrane

⚫ Required by cell to keep the internal

environment of the cell different from the

external environment

Outside

Inside

Na+

K+

Against Concentration Gradient

Against Concentration Gradient

Na+/K+ Pump