unit 1: cell membranes Flashcards
what are membranes and what are they made of?
they are partially permeable barriers made up of phosolipid molecules arrnged in abilayer with embeded proteins
describe the fluid mosaic model
FLUID: phospholipids (and proteins) are free to move laterally (side to side)
MOSAIC: proteins have a scattered arrangement within the hospholid bilayer
what are phospholipids and their roles?
hydrophgobic tail facing inwards with a hydrophilic head facing outwards arranged in a bilayer.
make the membrane flexiable and self-sealing
what is cholesterol and its role?
found in eukaryotic cells for fluidity and stability.
bind to the hydrophobic tails.
stop the membrane being to fluid a high temperatures and stop the membrane being to solid at low temperatures
what are glycolipids and their role?
phospholipids with attached carbohydrates.
inter cell signalling and recognision.
cell adhesion: helps to stick cells together.
what are intrinsic channel proteins and their role?
channel proteins on the inside of the cell that allow transport hydrophillic and large molecules through the phospholipid bilayer.
what are extrinsic channel proteins and their roles?
channel proteins on the outside of the cell.
cell recognision
receptors for signalling between cells and cell adhesion
what are glycoproteins and their role?
proteins with attached carbohydrates.
cell signalling and recognision receptors.
binds cells to basement membrane.
what is cell signalling?
processes that lead to communication and coordination between cells so that they can work together to trigger a response.
receptors have complementry hormones (insulin receptors
Is osmosis active or passive?
Osmosis is a passive process (doesn’t require ATP).
what is the definition of osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from an area of high water potential to low water potential
What affects the rate of osmosis?
Temperature/ amount of aquaporins / size of water potential gradient
Where can osmosis occur?
Through special channel proteins or through the phospholipid bilayer
What is facilitated diffusion?
Easy diffusion of large molecules or charged ions from an area of nigh concentration to low concentration through channel or carrier proteins
What affects the rate of facilitated diffusion?
Temperature/ concentration gradient / the number of channel proteins in the membrane.
What is simple diffusion?
Passive diffusion from an area of high concentration to an area of low concentration acrossa partially permeable membrane through the phospholipid belayer
What is active transport?
The movement of ions or polar molecules from low to nigh concentration against the concentration gradient using ATP
What does ATP stand for?
Adenosine tri phosphate
What is needed for active transport?
Carrier proteins/protein pumps that only change shape to transport molecules/substances across the membrane
What is exocytosis?
The movement of molecules out of the cell using ATP
Describe the steps of exocytosis.
1) vesicles made at the Golgi apparatus body to package molecules for transport
2)vesicle moves to the plasma membrane and fuses with it
3)phospholipids now added into plasma membrane and molecules released
What is endocytosis?
The movement of molecules into cells
How does endocytosis occur?
Molecules adhere to membrane or they can bind to receptors causing vesicle formation
