Membranes Flashcards
What forms the basic structure of a membrane?
Phospholipid bilayer
The bilayer consists of hydrophilic heads facing water and hydrophobic tails avoiding water.
What is membrane asymmetry?
The outer and inner leaflets differ in lipid, protein, and carbohydrate composition
This difference contributes to the unique functions of each leaflet.
What model describes the fluid nature of membranes?
Fluid mosaic model
This model allows for flexibility and proper function of embedded proteins.
What factors influence membrane fluidity?
Temperature, phospholipid composition, cholesterol
The degree of unsaturation and tail length of phospholipids also affect fluidity.
What role does cholesterol play in membrane fluidity?
Acts as a fluidity buffer
It helps maintain membrane stability under temperature fluctuations.
What are the two main types of membrane proteins?
Integral and peripheral proteins
Each type serves various roles in the membrane.
What are transmembrane domains?
Stretches of non-polar amino acids that span the membrane
These are found in integral membrane proteins.
What is passive transport?
Transport that requires no energy
Includes simple diffusion and facilitated diffusion.
What is active transport?
Transport that requires energy (ATP)
This process moves molecules against concentration gradients.
Fill in the blank: The phospholipid bilayer has _______ heads and _______ tails.
hydrophilic; hydrophobic
True or False: Membrane proteins can function as signal receptors.
True
What is passive transport?
Movement down concentration gradients (high to low)
Includes diffusion and facilitated diffusion.
What is facilitated diffusion?
Requires transport proteins (channels, gated channels, carrier proteins) to help molecules cross the membrane
It is a type of passive transport.
What is active transport?
Moves molecules against gradients using energy
Includes primary and secondary active transport.
What is primary active transport?
Uses ATP to move molecules against a gradient (e.g., sodium-potassium pump)
It is a type of active transport.
What is secondary active transport?
Uses energy from electrochemical gradients to move molecules
Example: sodium-glucose co-transporter.
What is endocytosis?
Uptake of substances via vesicles
Includes receptor-mediated endocytosis, pinocytosis, and phagocytosis.
What is exocytosis?
Release of substances from cells through vesicle fusion with the membrane
It is the opposite of endocytosis.
What is osmosis?
The movement of water across a semi-permeable membrane toward regions of higher solute concentration.
What happens to cells in a hypertonic solution?
Cells can shrink.
What happens to cells in a hypotonic solution?
Cells can swell.
What happens to cells in an isotonic solution?
Cells remain stable.
What is primary active transport?
Uses ATP to maintain concentration gradients, e.g., proton pumps and sodium-potassium pumps.
What is secondary active transport?
Utilizes ion gradients, e.g., sodium-glucose cotransport.
What are the key roles in signal transduction?
Transporters, enzymes, and receptor proteins transmit signals across membranes.
What do signaling pathways often involve?
Phosphorylation cascades that amplify faint extracellular signals.
How is energy stored in gradients?
Concentration gradients across membranes store potential energy.
What is the role of electrochemical gradients?
Generate voltage across membranes, important for nerve function.
What do receptor proteins do in signal transduction pathways?
Activate intracellular pathways, e.g., phosphorylation cascades.
Fill in the blank: Small signals can be _______ to produce larger responses.
[amplified]
