Chapter 3 Flashcards
(62 cards)
cytoplasm
gel-like network made of proteins and other macromolecules
cell membrane
encloses the cytoplasm. The structure that defines the existence of the cell.
cell wall
covers the cell membrane, b/w inner and outer membrane.
nucleoid
non-membrane bound area of cytoplasm w/ chromosome in the form of looped coils
cell membrane made up of
•Double layer of phospholipids • Proteins embedded in membrane -Anchor membranes to envelope -Sense the outside world -Transport materials into cell
cell membrane functions
• Mechanical boundary • transport nutrients/waste • Site for electron transport chain -Respiration -Photosynthesis • Contain (“sensing”) receptor proteins • Most membrane proteins (~80%) are integral, the rest are peripheral
most membrane lipids are
phospholipids. Phospholipids are amphipathic = have a polar and non-polar end.
proteins float in
2-dimensional “sea” of phospholipids. membrane fluidity is required.
increase membrane fluidity
• Use lipid molecules with shorter chain lengths and that have more double bonds (unsaturation)– adds “kinks”
• Decrease membrane fluidity (increase rigidity)
• Use longer chain lengths (Van der Waals)
• Use fewer double bonds
• Use molecules that hinder movement of phospholipids
-Stiff planar rings
-Reinforcing agents
-Sterols (e.g.) cholesterol
-Eukaryotes
-Hopanoids
-Structurally similar to steroids
-ProkaryotesBacteria would adapt to increasing
temperature by?
Increase # of long chain lipids, decrease # of double bonds.
proteins form about
half the mass of the membrane
Transport across the cell membrane
- The cell membrane acts as a semipermeable barrier
- Selective transport is needed for survival
- weak acids/bases can cross membrane
diffusion
Small uncharged molecules, like O2 and CO2, permeate the membrane
transporters
pass material into and out of cell
• Polar/charged molecules need transport
concentration gradient
always going from high to low.
passive transport
molecules move along their concentration gradient
active transport
molecules move against their concentration gradient
• Requires energy
How do prokaryotes protect their cell membrane?
cell envelope includes structural support (cell wall.)
-some have S-layer
• prokaryotes like mycoplasmas have cell membrane w/ no outer layers
sacculus
bacterial cell wall w/ single interlinked molecule that covers cell.
• cage-like structure (flexible)
• has shape and withstands intracellular turgor pressure
Most bacterial cell walls are composed of
peptidoglycan (murein)
glycan chains
Long polymers of two disaccharides:
• N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Peptidoglycan
polymer of peptide-linked chains of amino sugars. unique to bacteria. good for antibiotics.
Gram-positive-
gram negative-
Mycobacteria-
– thick cell wall (e.g. firmicutes)
– thin cell wall (e.g. proteobacteria)
– multilayered envelope w/ defensive structures like mycolic acids (e.g. Mycobacterium tuberculosis)
