Cell membrane (L08) Flashcards
What is the properties of biological membrane?
- Semi-permeable membrane
- Made up of phospholipid bilayer
Able to enter/leave the cell membrane:
- Very small molecules
- Lipid-soluble molecules
- Gases
Unable to enter/leave the cell membrane:
- Large molecules
- Water-soluble molecules
What is the function of biological membrane?
Maintain different environment inside and outside of the cell/organelles
What does it mean when a solution is hypotonic?
- Net flow of water into the cell
- Cell gains volume
- Solute concentration outside of the cell is lower than inside of the cell
- Solute cannot enter the cell
What does it mean when a solution is isotonic
- No net flow of water into/out of the cell
- Cell volume remain stable
- Solute concentration outside of the cell is the same as inside of the cell
- Solute cannot leave/enter the cell
What does it mean when a solution is hypertonic?
- Net flow of water out of the cell
- Cell loses volume
- Solute concentration outside of the cell is higher than inside of the cell
- Solute cannot leave the cell
What is the function of membrane transport system?
Facilitates the movement of charged/polar molecules across the membrane
What is a channel protein?
It forms a protein-lined passageway across the membrane
Multiple water molecules/ions are able to move simultaneously at a very rapid rate
What is a transporter protein?
Binds to only one/ a few substrate molecules at a time
Undergoes a conformational change so that bound substrate molecules are transported across the membrane
What is secondary active transport?
Energy for secondary active transport is obtained from the transportation of the co-transported molecule down its concentration gradient
What is primary active transport?
Energy for primary active transport is obtained from the hydrolysis of ATP
What is an uniport?
Carrying out passive transport of a single substrate down its concentration gradient
What is symport?
Co-transport of 2 substrates by a membrane transport protein
Substrates cross the membrane in the same direction
What is an antiport:
Co-transport of 2 substrates by a membrane transport protein
Substrates cross the membrane in opposite directions
What is a coupled transporter?
Transmembrane protein that transports one substrate against its concentration gradient, by coupling it to a transport of a second substrate down its concentration gradient
What is endocytosis?
Movement of particles into the cell
Vesicles carry essential materials into the cell
What is exocytosis?
Movement of particles out of the cell
Vesicles carry materials for secretion out of the cell
How does enzyme move in and out of the cell?
IN:
Cell imports enzymes into the cell via endocytosis
Vesicles will carry the enzymes into the cell
OUT:
Cells export enzymes out of the cell via exocytosis
Vesicles will carry the enzymes out of the cell
How does water move in and out of the cell?
Free water molecules are able to pass through the plasma membrane by osmosis
Water is also able to enter and leave the cell through pores in aquaporins
How does potassium move in and out of the cell?
Potassium ions move in and out of the cell through a specific ion channel
Potassium ion move by diffusion (passive transport)
How does sodium move in and out of the cell?
Sodium continuously move through ion channels, to achieve a balance on both sides of the membrane
When there is a need for a low concentration of sodium inside the cell and a low concentration of potassium ion outside of the cell, the cell uses the sodium-potassium pump.
This is to export sodium ions and import potassium ions via primary active transport.
How does glucose move in and out of the cell?
Glucose travels into the cell with the help of GLUT2 transporter, via facilitated diffusion (passive transport)
Inside the cell:
An enzyme binds to the glucose molecule, preventing it from passing through the GLUT2 transporter, hence glucose stays in the cell
The concentration of glucose outside of the cell remains higher than inside of the cell, hence glucose molecules are able to enter the cell via diffusion
How does carbon dioxide enter/leave the cell?
Carbon dioxide is able to pass through the lipid bilayer
When the cell generates carbon dioxide, there is a higher concentration of carbon dioxide in the cell than outside of the cell.
Carbon dioxide leaves the cell via diffusion
How does oxygen leave/enter the cell?
Oxygen is able to pass through the lipid bilayer
Concentration of oxygen within the cell is lower than outside of the cell
Oxygen is able to enter the cell via diffusion
