Flashcards in Module 1 - Principles of Cell Function Deck (30):
Define amphipathic molecules and give and example
Molecules that have hydrophilic and hydrophobic parts e.g. phospholipids of the cellular membrane
Explain the fluid mosaic model of membranes
fluid - moving all the time
mosaic - lots of proteins embedded in it
Role of cholesterol in cell membrane
hold phospholipids apart when cold and together when hot
Saturated vs unsaturated
Saturated - max hydrogens, straight, single carbon carbon bonds, usually solid as can pack together tightly
Unsaturated - at least on double or triple carbon carbon bond, bent, more viscous as cannot pack together as tightly
What is a glycoprotein?
A membrane protein with a carbohydrate attached
What is a glycolipid?
A lipid with a carbohydrate attached
Where are the hydrophilic and hydorphobic regions of the membrane?
Hydrophobic - inside, neutral
Hydrophilic - outside, charged
How do we know that membranes are fluid?
Mouse and human cell test - proteins spread over entire cell (not one sided)
Six major functions of membrane proteins with examples
- transport (ions)
- enzymatic activity
- signal transduction (receptors)
- cell to cell recognition (antigen-antibody reactions)
- intercaellular joining (to form tissues)
- attachment to the cytoskeleton and extracellular matrix (ECM)
Passive vs active vs facilitated diffusion (examples)
Passive - along concentration gradient, no work (small neutral molecules)
Active - against concentration gradient, uses ATP (Na+/K+-ATPase pump)
Facilitated - along concentration gradient, molecules carried by transport proteins to speed up an otherwise passive process (aquaporins, ion channels)
What are channel proteins? Examples
Proteins in the cellular membrane that provide corridors that allow a specific molecule or ion to cross the membrane e.g. aquaporins for the facilitated diffusion of water, and ion channels which are gated so that they open and close in response to stimulus
Define and provide examples of osmotica
compounds that cause osmosis due to inability to cross the membrane e.g. ions, sugars, proteins
What is osomosis?
diffusion of water through a selectively permeable membrane into another aqueous compartment containing solute at a higher concentration
Define tonicity, isotonic, hypertonic and hypotonic and their effect on the cell
tonicity - the ability of a solution to cause a cell to gain or lose water
isotonic - inside and outside solute concentration is the same: no change in cell
hypertonic - solute concentration higher outside the cell, so water flows out of the cell causing shrivelling - crenation
hypotonic - solution concentration higher inside the cell, so water flows into the cell causing it to swell and lyse
What is crenation?
The shrivelling of a cell in hypertonic solution
What is hemolysis?
The bursting of a cell in hypotonic solution
Plant cell tonicity vs animal cell tonicity
Plants like hypotonic conditions as their cell wall saves them from lysing. These conditions make the cells turgid, rather than flaccid as in isotonic solution or plasmolysed as in hypotonic solution which is when the plasma membrane seperates from the cell wall
Are transport proteins specific for the substance it moves?
What kind of substances do transport proteins allow the pass across the membrane?
hydrophilic as they wouldn't be able to pass through the membrane otherwise
What is an electrogenic pump?
A transport protein that generates voltage across a voltage across a membrane e.g. sodium-potassium pump in animals and the proton pump in plants, fungi and bacteria
What is cotransport? Example
When the active transport of a solute indirectly drives the transport of another solute e.g. plants gradient of hydrogen drives active transport of nutrients
Types of endcytosis
Phagocytosis - engulfing particles
Pinocytosis - cells drinking (vesicle of extracellular fluid formed)
Receptor-mediated endocytosis - vesicle formation triggered by ligands binding to membrane receptors
3 stages of cell signalling
Reception - signalling molecule binds to receptor
Transduction - relay molecules pass on signal
Response - activation of cellular response
What is an agonist?
A substance that is similar to a naturally occuring chemical in the body e.g. drugs
4 receptor types in families with speed of neurotransmission
Plasma membrane receptors:
Ion channel receptors - fastest (milliseconds)
G protein-coupled receptors (e.g. adrenaline) - second fastest (seconds)
Tyrosine kinase linked receptors (e.g. insulin) - third fastest (minutes)
Steroid receptors - slowest reaction
facts about GPCR's
- most important receptor types due to abundance
- 7 transmembrane spanning domains (7 helix protein)
- over 1000 types
- activated by numerous stimuli inc. light, ions, odourants, gustative molecules, neurotransmitters, hormones, peptides, proteins
Adenylyl cyclase GCPR pathway
Adenylyl cyclase (enzyme) activated
+ ATP produces cyclic AMP (a second messenger)
acts on protein kinase A which initiates cellular response
What is a kinase?
An enzyme that transfers phosphates to activate or inactivate target proteins
3 roles of phosphorylation
- conformational change in protein
- protein-protein interactions
- change in cellular location