The 1st Unicram (2) Flashcards
What is polarity?
The separation of electrical charge within a molecule (Forms electric dipole, negative and positive charge)
Dipoles formed due to difference in electronegativity between bonded atoms
What properties does polarity lead to?
Increased boiling point
Increased solubility within other polar solvents
Increase surface tension
What are lipids?
Broad class of macromolecules, hydrocarbons
Hydrophobic
Functions of Lipids?
Separation of two polar environments via hydrophobic bilayer
Energy storage
Signalling through hormones
Vitamins
What are triglycerides made of?
3 Long chain fatty acid
Glycerol sugar
What are the different states of fatty acids?
Saturated (C-C)
Unsaturated (C=C)
Polyunsaturated (2x C=C)
(ALWAYS CONTAINS COOH)
What does altering the length of a fatty acid chain change?
Alters membrane fluidity
What are phospholipids made of?
Two fatty acid chains + Phosphate group
Why are phospholipids Amphipathic?
Have both a hydrophobic and hydrophilic section
Allows formation of a phospholipid Bi-layer
What is a spontaneous grouping of phospholipids called?
Micelles, polar heads face outwards and hydrogen bond to the surrounding water
non polar tails face inwards and make a hydrophobic central core
Phospholipid uses?
Make a semi-permeable barrier, separates cells from external environment and organelles from cytoplasm
Allows production of specific and regulated cell environments
Steroids properties?
Highly hydrophobic, insoluble in water
Uses of sterioids within organisms
Precursor to different steroid hormones
Precursor to vitamin D
Aids in stability and fluidity of animal cell membranes
function of cholesterol?
Alters the membrane fluidity, changes these properties of the plasma membrane:
Thickness
Water penetration
Curvature
Endo/exocytosis
Fluid Mosaic meaning
Fluid: Free movement of molecules
Mosaic: Plasma membrane is made of several different components
Physical conditions that affect the fluidity of the membrane?
Temperature:
Increased K.E allows for increased rearrangement of phospholipids
Phospholipid composition:
Shorter fatty acid chains have less points of movement, less intermolecular forces so less energy needed to freely move. If unsaturated fatty-acid, less packing of phospholipids so more mobility
Cholesterol:
Increases melting point of phospholipid bilayer
Prevents clustering of phospholipids in cold temps
FRAP method?
Label plasma membrane with fluorescent chromophore
View small region of cell surface through florescent microscope
Destroy fluorescent molecules with intense light pulse
Monitor region, undamaged chromophores will replace damaged ones.
What is the membrane composed of?
*Phospholipid:
- Main molecule
- Forms the cell membrane
*Carbohydrates:
- Attached to proteins which are on outside of membrane layers
- Aids in cell-to-cell recognition
*Cholesterol:
- Embedded between phospholipids of the bilayer
- Retains plasma membrane fluidity
*Proteins:
- Embedded within/surface/across membrane
- Relay signals between internal/external environments
- Transport proteins
- Aid in digestion
Use of plasma membrane?
Regulates cellular volume, maintains pH
Concentrates metabolic building blocks, removing toxic substances
Generates and maintains ionic gradients
What molecules can move across the membrane?
Gases
Small polar molecules
Small hydrophobic molecules
Charged ions
Large polar molecules
Channel proteins?
Channel proteins allow for facilitated diffusion of molecules which cant diffuse across the membrane or ones with slow diffusion rates
Can be opened and closed
Carrier proteins?
Bind to specific molecules, undergoes a conformational change and releases on the other side of the membrane
Polar molecules get transported via carrier proteins
Facilitated diffusion
Takes place through proteins embedded in plasma membrane
Proteins form water-filled channel where ion can pass down concentration gradient
channels can be opened or closed
Ligand gated channels?
Opened/closed by a small signalling molecule or ligand which doesn’t pass through membrane
Acetylcholine opens Na+ channels triggering depolarisation
Gamma Amino Butyric Acid binding at certain synapses in central nervous system admits Cl- ions into the cell and causes hyperpolarisation
Internal Ligands
Bind on site to channel protein exposed to cytosol
Secondary messengers regulate channels that initiate impulses in neurons responding to odours and light
ATP needed to open the channel that allows Cl- and bicarbonate ions out of the cell
Mechanically gated channels
Sound waves bend cilia on the hair cells of the Organ of Corti and open up K+ channels leading to creation of nerve impulses
mechanical deformation of the cells of stretch receptors open the ion channels leading to nerve impulse creation
Active vs Passive transport proteins
- Passive Transport (Facilitated diffusion) occurs without the need for a change in free energy (GLUT)
Can occur spontaneously with binding of transport molecule - Active Transport needs a change in free energy to allow movement
(NA+/K+ ion pumps need hydrolysis of ATP to cause conformational shape change)
Can use electrochemical gradient to aid transport of molecule
Exo/Endocytosis?
Active forms of transportation, a vesicle is used to engulf or export macromolecules through plasma membrane
In -> Exocytosis
Out -> Endocytosis
Na+/K+ ion pump key functions?
Formation of resting charge potential across the membrane
Na+ ions can be used as a secondary active transporter molecule to aid in importation of glucose, amino acids, nutrients
Maintains cellular osmolarity
