5a. Cell membrane transport and osmosis Flashcards
(26 cards)
What forms a complete boundary around the cell?
The plasma membrane
The plasma membrane is essential for maintaining the integrity of the cell.
What are the main components of the plasma membrane?
Phospholipids, proteins, cholesterol
These components contribute to the structure and function of the plasma membrane.
What is the basic structure of the plasma membrane?
Bi-molecular layer of phospholipid molecules
This bilayer is crucial for the membrane’s selective permeability.
How does cholesterol function within the plasma membrane?
Inserted between phospholipid molecules at regular intervals
Cholesterol helps to maintain membrane fluidity.
What types of proteins are incorporated in the plasma membrane?
Integral and peripheral proteins
These proteins play roles in transport and communication.
What does it mean that the plasma membrane is selectively permeable?
It allows certain substances to cross while blocking others
Selective permeability is essential for cell homeostasis.
What factors influence membrane permeability?
Solubility in liquids, driving forces, molecular size
These factors determine how substances move across the membrane.
What are the two types of transport across the membrane?
Active and passive transport
Active transport requires energy, while passive transport does not.
What are the three types of passive transport?
- Diffusion through the bilipid layer
- Diffusion through ion channels
- Facilitated diffusion using a carrier
These mechanisms allow substances to move without energy expenditure.
What substances can diffuse through the bilipid layer?
Lipid soluble substances (respiratory gases, lipids, small alcohols)
A concentration gradient is usually the driving force for this type of transport.
What is required for water soluble substances to cross the bilipid layer?
Integral membrane proteins
These proteins act as channels or carriers for transport.
How does facilitated diffusion work?
A solute binds to a specific transporter on one side and is released on the other
This process depends on the steepness of the concentration gradient and the number of transport proteins.
What characterizes ‘gated’ protein channels?
They open transiently in response to specific signals
Gated channels transport ions faster than facilitated diffusion.
What is active transport?
An energy-requiring process that moves solutes against a concentration gradient
Active transport is crucial for maintaining concentration gradients.
What is the primary active transport mechanism commonly found in cells?
Sodium-potassium ion pump
This pump is essential for maintaining cellular ion balance.
What is secondary active transport?
Transport driven by the energy stored in sodium or hydrogen concentration gradients
This mechanism involves symporters and antiporters.
What is exocytosis?
Movement of large molecules out of the cell
This process is often used in secretory cells.
What is endocytosis?
Movement of large molecules into the cell
This includes pinocytosis, phagocytosis, and receptor-mediated endocytosis.
How do water molecules penetrate the plasma membrane?
By diffusion through the bilipid layer or through aquaporins
Aquaporins are specialized channels that facilitate water transport.
What is osmosis?
Movement of water from a low solute concentration to a high solute concentration across a semi-permeable membrane
Osmosis is critical for maintaining cell integrity.
What factors drive water movement during osmosis?
Concentrations of solute dissolved in water
Water moves towards the solution with the highest osmotic pressure.
What is tonicity?
A measure of a solution’s ability to change cell volume by altering water content
Tonicity affects cell shape and function.
What happens to cells in an isotonic solution?
No net movement of water, cells maintain normal shape
RBC maintain normal shape
This is essential for cell survival.
What occurs to cells in a hypotonic solution?
Cells gain water, in danger of swelling or bursting
RBC undergo haemolysis
This can lead to a process called hemolysis in red blood cells.
