T1M1 Flashcards
(21 cards)
Streptococcus salivarius
a normal inhabitant of the upper
respiratory tract and oral cavity
Staphylococcus haemolyticus
Resides on skin
Bacteroides thetaiotaomicron
A predominant intestinal bacteria
Cell
A membrane bound structure containing macromolecules
Four Classes of Macromolecules
- Nucleic acids (DNA & RNA)
- Proteins
- Polysaccharides
- Phospholipids
Membranes
Separate an internal environment form the external environment. This allows these distinct environments to have different chemical composition.
Cell membrane is made up of
Lipids. Each of these macromolecules has hydrophobic and hydrophilic properties that allow “stacked” lipid bilayers to form.
Water molecules interact with
the head regions, but not the tails of phospholipids
lipid aggregates form with or without energy?
Spontaneously, without the use of any energy.
Factors affecting the fluidity of cell membranes (4)
- Unsaturated or saturated fatty acids
- Number of carbons in the fatty acid tails
- Temperature
- The presence or absence of cholesterol
Lower permeability
Less fluid membrane with fewer unsaturated fatty acids and more cholesterol.
Higher Permeability
More fluid membrane with more unsaturated fatty acids and less cholesterol.
Selectively permeable
The ability of cell membranes to control the traffic of substances into and out of the cell and its organelles
Passive diffusion
from areas of high to low concentration (along a
gradient)
Passive transport
or facilitated diffusion: from areas of high to low
concentration (along a gradient)
Active transport
molecules move against the concentration gradient
(fueled by energy from the hydrolysis of ATP)
Osmosis
the transport of water across membranes. Water diffuses from a less concentrated solution (hypotonic) to a more concentrated solution (hypertonic)
Aquaporins
Allow rapid transport of water, exclusively permeable to water, protein channels allow water to move across the cell membrane through osmosis. Movement across is concentration gradient dependent.
What moves across membrane easily
gases and hydrophobic molecules (O2, CO2, N2, steroid hormones)
what can trickle through the membrane
small uncharged polar molecules (urea, glycerole)
what cannot go through the membrane
large, charged polar molecules (glucose, sucrose, ions)
