Plasma Membrane and Organelles Flashcards
What is a plasma membrane?
It is a semi-permeable barrier that allows passage of oxygen, nutrients and waste. It controls movements of substances in and out of the cell.
Plasma membranes : surface area to volume ratio
Small cell = greater surface area to volume ratio
Large cell= smaller surface area to volume ratio
What is the Phospholipid Bilayer?
- Double layer of phospholipids with embedded or attached proteins
- Has hydrophilic heads (likes water) and hydrophobic tails (doesn’t like water)
Saturation, Temperature and Cholesterol in the Plasma Membrane
Saturation : saturated cell = packed tightly, unsaturated = tails prevent tight packing, more fluidity
Temperature : high temps = more fluidity, lower temps = less fluidity
Cholesterol: stabilises membrane fluidity
What are plasma membrane proteins?
Proteins that determine function of the membrane, each cell can have many different cell specific proteins that have multiple functions
Functions of plasma membrane proteins
Signal Transduction : relays messages from body into cells
Cell Recognition : glycoproteins can detect shape of sugar
Intercellular Joining : proteins bind two cells (forms long lasting connections)
Linking cytoskeleton and ECM : holds cell to something else (cell can physically connect with protein structures outside the cell)
Membrane Transport : help molecules to move across membrane (can be passive or active)
What is Diffusion?
- Passive transport = no energy required
- Moves molecules down their concentration gradient
What is Facilitated Diffusion?
- Passive Transport = no energy required
- Movement of hydrophilic molecules requires membrane proteins (channels and carriers) to aid movement of specific substances down their concentration gradient
What is Osmosis?
Movement from a high water (low solute) concentration to a low water (high solute) concentration to prevent swelling or shrinking, requires channels called aquaporins
What is Active Transport?
Requires energy and transport proteins as moving against concentration gradient. Allows a cell to have an internal concentration different from its surroundings e.g sodium potassium pump
What is Co-transport?
Indirect active transport, one substance pumped across membrane and its concentration gradient used to power movement of second substance against its concentration gradient
How do different parts of the cell do different things?
Organelles provides special conditions for specific processes, allows specific substances to be concentrated and forms concentration gradients
