Membrane structure and function II Flashcards
What way can lipid soluble molecules move?
Lipid soluble molecule can move either way through the membrane
What is the movement of lipid soluble molecules dependant on?
Movement of these molecules is dependant on their concentration
What is passive diffusion driven by?
Driven by concentration gradient
What is active transport driven by?
Driven by hydrolysis of ATP
What is an antiporter?
Antiporter transport 2 molecules in opposite direction
What is a symporter?
Symporter transport 2 molecules in the same direction
Passive transport with and without a carrier
Passive transport without a carrier is much slower compared to transport with a carrier.
What do different tissues have?
Different tissues have different glucose transporters
How are glucose transporters mediated?
Carrier mediated
What direction is glucose movement?
Bi-directional
How is glucose transported?
- Conformational change in the carrier protein shape resulting in transportation
- Glucose can now fit in the binding site
- Carrier protein changes shape again and this causes the release of glucose through the other side of the membrane
- Glucose is phosphorylated to maintain the glucose concentration gradient
a. This allows the cell to take in glucose continuously
Why is glucose phosphorylated and what is formed?
Glucose is phosphorylated to form G6P because there are more G6P transport proteins
What is Kt?
Kt is the measure of affinity of the transporter of the substrate
What does a low Kt mean?
It means a high affinity
Where is Glut 4L primarily found?
Primarily found in adipocytes and skeletal muscles
What are Glut 4L stimulated by?
Stimulated by insulin
What do cells usually have a reserve of?
Have a reserve of transporters
How can glucose uptake be increased?
Increased by increasing the number of transporters
What does active transport require?
Requires an integral membrane protein
How is the concentration gradient of an ion maintained in active transport?
Ion concentration gradient maintained by ATP
What is foxglove used to treat?
Used to treat dropsy(Congested heart disease)
What is the active ingredient in foxglove?
Active ingredient is digitalis(Cardiotonic steroid)
What does digitalis do?
Inhibits the Na+/K+ ATPase pump
Why is intracellular Na+ required?
Intracellular Na+ is required for correct regulation of the contraction of the heart
What does Ca2+ determine in the heart?
Ca2+ determine the strength of the contraction of the heart
What are SGLT-1 and 2?
They’re both glucose transporters
What gene is SGLT-1 and 2 members of?
Members of the SLC5A gene
What do the SGLT-1 and 2 use energy from?
Use energy from the Na+ gradient created by the ATPase pump to transport glucose across apical membrane
What is used to treat type 2 diabetes?
SGLT2 inhibitors, like glifiozins
What ingredients does oral rehydration therapy contain?
8 teaspoons of sugar, 1 teaspoon of salt and 1 litre of water
What is oral rehydration therapy used for?
Oral rehydration contains both sodium and glucose
Used to treat severe dehydration
How does oral rehydration therapy work?
- SGLT1 transports glucose and sodium across the cell membrane
- Hundreds of water molecules move into epithelial cell for each cycle of transport
- This can achieve rehydration
What do membranes act?
Act as partially permeable membranes
What is ATP production dependant on?
ATP production is dependant on the properties of membranes
What is cystic fibrosis a disease of?
Cystic fibrosis is a disease of transport across membranes
What does compartmentalisation do?
Separates reactions
What does compartmentalisation enable?
Enables the local environment to be regulated for instance, pH
What does compartmentalisation bring together?
Brings reactants together
What do proteins have which target them?
Proteins have particular signal sequences which target them to specific organelles
Where is Lysosomal hydrolase synthesised and transported?
Lysosomal hydrolase is synthesised in the ER and transported to Golgi where mannose is added forming Mannose 6 phosphate
What does mannose do to the protein?
Mannose directs the protein to the lysosomes
What does M6P do to its receptor?
Mannose 6 phosphate binds to its receptor
What happens once protein reaches the lysosome?
Reaches lysosome where it fuses and hydrolyses
What is I cell disease caused by?
Caused by the deficiency of GIcNAc phosphotransferase which phosphorylates mannose residues
What does is mean when there is a deficiency of GIcNAc phosphotransferase?
This means proteins cannot be marked and are excreted out the cell
What does this eventually lead to?
Lysosomes unable to function and results in a build up of substances within the lysosome which it’s unable to degrade.
