Cell Membranes and Transport Flashcards
What is meant by the term ‘fluid mosaic model’?
fluid describes the movement of phospholipids and proteins by diffusion in the bilayer, mosaic refers to the appearance of scattered proteins
What is the structure of a membrane?
a phospholipid bilayer consisting of hydrophobic tails facing towards each other, hydrophilic heads facing outwards, cholesterol molecules, proteins
What is a phospholipid?
a molecule consisting of two hydrophobic fatty acid tails and a hydrophilic phosphate head
What is cholesterol?
a molecule made of a hydrophobic and hydrophilic region
What are membrane proteins?
intrinsic or extrinsic proteins in the membrane, intrinsic found on the inside, outside, or whole membrane (transmembrane)
What are glycoproteins?
carbohydrate chains attached to membrane proteins, the chains form a glycocalyx and project into the watery fluid outside the membrane, forming hydrogen bonds
What are channel proteins?
a gated, water filled pore that forms a hydrophilic channel for ions to pass through
What are carrier proteins?
can flip between two shapes, opening at different sides of a membrane
What are cell surface receptors?
glycoproteins/lipids which bind to substances at cell surface, three types are signalling receptors, endocytosis receptors, cell adhesion receptors
What are cell surface antigens?
glycoproteins/lipids acting as markers, allowing cell-to-cell recognition
What is cell signalling?
the process of sending a message from one place to another over a signalling pathway
What are the different cell signalling pathways?
- hydrophobic signalling molecule diffuses directly across membrane and binds to intracellular receptor somewhere else in the cell
- signalling cascade
- open ion channel
- act as membrane bound enzyme
- cell-cell contact
What is diffusion?
process of substances moving across membrane down a gradient from a place of high to low concentration
What is active transport?
molecules use ATP to move across membrane against concentration gradient through carrier proteins
What is osmosis?
diffusion of water across a membrane from a dilute to concentrated solution
What is endocytosis?
the engulfing of material into cell by pino/phagocytosis, making phagocytic vacuoles
What is exocytosis?
secretion of material out of cell by vesicles
What is the surface area: volume ratio?
the larger the cell, the smaller its surface are in relation to its volume
What is water potential?
the tendency of water to move out of a solution, from a solution of high water potential to low
What is solute potential?
the extent to which solute molecules decrease the water potential of a solution
What is pressure potential?
the contribution of pressure on the water potential of a solution
What happens to animal cells when they are placed in a solution of lower water potential?
cells shrink
What happens to plant cells when they are placed in a solution of higher water potential?
cell becomes turgid as cell wall regulates pressure
What is the signalling cascade?
polar signalling molecule binds to specific receptor, signal transduction, G protein, many second messengers (amplification), enzymes activated, final enzyme produced
