Lecture 4: Plasma Membrane and Organelles Flashcards
What is the purpose of organelles?
To provide specialised compartments for specific processes. Keeping incompatible process apart. They also allow specific substances to be concentrated and create concentration gradients.
What structure bounds on cells?
The plasma membrane
What is the structure of the plasma membrane?
The plasma membrane is made of a phospholipid bilayer. The hydrophilic head faces the outside of the cell and interior. While the hydrophobic tails cover the space in-between.
What is meant by the plasma membrane being semipermeable?
This means the plasma membrane is only permeable to some substances while others it is not due to size and polarity.
Do organelles have there own membranes?
Organelles also have there own phospholipid bilayer to regulate what enters and exits the organelle.
What is the role of cholesterol in the plasma membrane?
The roll of cholesterol in the plasmamembrane is to increase stabilise membrane fluidity. Its most important job is to reduce the permeability of the plasma membrane by increasing the packing of phospholipids.
Active vs Passive Transport
Active requires ATP where as Passive does not.
What is diffusion?
Diffusion - membrane is permeable to hydrophobic molecules which can move down there conc. gradient into the cell. Type of passive transport.
What is facilitated diffusion?
Movement of hydrophilic molecules can move across a membrane protein down their conc. gradient. No energy is required but some membrane proteins open and close in response to stimuli e.g. potassium and sodium voltage gated channels.
What is osmosis?
Movement from a high water (low solute) concentration to a low water (high solute) concentration.
What is active transport?
Transport which requires ATP. Allows molecules to moves against their conc.gradient giving the cell a different internal conc. to its environment.
What is co-transport?
Indirect form of active transport where the movement of a molecule pumped across the membrane results in a different molecule being pumped into the cell.
What are membrane proteins?
Proteins which are found on the plasma membrane.
What is the role of a membrane protein?
Signal transduction, Cell recognition w/ glycoproteins, Linking cytoskeleton to extracellular matrix.
