Membrane Transport Flashcards
solvent
dissolving medium
present in highest quantity
usually water
solute
substances dissolved in solvent
solute concentration
number of solute molecules in volume of solvent
penetrating solutes
move through membrane
non penetrating solutes
cannot move through membrane
concentration gradient
solute concentration difference on either side of membrane
passive transport
diffusion
movement from area of high solute concentration to area of low solute concentration due to kinetic energy of molecules
does not require energy
simple diffusion
small, lipid soluble molecules pass through lipid portion of membrane ex water (slowly), oxygen, carbon dioxide
facilitated diffusion
protein helps it across membrane
small, water soluble molecules (glucose) require membrane carriers
follow gradient
carrier binds molecule and changes shape to move molecule across membrane
(pac man)
osmosis
movement of water across semipermeable membrane high water (low solute) concentration to low water (high solute) concentration
tonicity
ability of a solution to cause a cell to gain or lose water
refers to a concentration of non penetrating solutes outside cell
hypotonic
solute concentration lower outside cell than inside
water moves into cell
cell enlarges
hypertonic
solute concentration higher outside cell than inside
water moves out of cell
cell shrinks
isotonic
equal solute concentrations in and out of cell
equal water movement in and out
filtration
movement of solutes through membrane along pressure gradient
ex: urine from blood
active transport
materials move against concentration gradient from low concentration to high
requires energy and carrier proteins
moves one of more substances in one direction or in opposite directions
ex: sodium/ potassium pump
group translocation
bulk transport in bacteria
phosphotransferase systen
requires ATP
cannot move back across membrane
bulk transport
active transport in eukaryotes
requires ATP
materials packaged into vesicles that merge with membrane or form from membrane
exocytosis
materials directed out of cell
endocytosis
materials directed into cell
phagocytosis
engulf substances outside cell
bring to inferior
ameoba, microphage
enzyme
increase rate of chemical reaction
lower energy of activation
bring reactants close together and properly orient reactants
enzymes are unchanged after reaction
energy of activation
amount of energy required for reaction to occur
substrate
substance modified by enzyme
active site
part of enzyme that binds to substrate
product
result of enzyme reaction
allosteric site
second binding site away from active site
binds inhibitors or activators
5 types of enzyme reactions
- functional group transfer
- electron transfer
- rearrangement
- dehydration (condensation, synthesis)
- hydrolysis reaction (cleavage, decomposition)
functional group transfer
from 1 molecule to another
ADP + P = ATP
electron transfer
from 1 compound to another
NADH
rearrangement
of 1 compound into another
glucose into 2 pyruvates
dehydration
forms large compounds from small compounds
anabolic
requires energy/ uses ATP
removes water from reaction- forms metabolic water from reactants
glucose + galactose = lactose + water
hydrolysis reaction
splits large compounds into small compounds
catabolic
releases energy/ forms ATP
uses water to form products, adds water to reaction
lactose + water = glucose + galactose
enzyme structure
globular proteins
apoenzyme
protein part only
cofactor and coenzyme
non protein structures required by some enzymes for function
cofactor examples
ions, iron, zinc, calcium
inorganic molecules
coenzyme examples
some vitamins niacin (NADH) riboflavin (FADH2) vitamin C organic molecules
holoenzyme
active enzyme
all parts combined
induced fit model
enzyme active site binds substrate
enzyme/ substrate binding changes shape of active site to exactly fit substrate
orients substrate so bonds can be broken or rearranged
enzyme examples
maltase, lactase, sucrase, catalase
catalase
neutralizes free radicals from hydrogen peroxide
antioxidants
production decreases with age
composed of 4 protein subunits
free radicals
atoms with unpaired elements
generated by chemical reactions, radiation, tobacco smoke, air pollution
may contribute to aging, cause some cancers
inhibitors
denature enzymes (lose 3D shape of active site)
inhibitor examples
temperature, pH, Na+
temperature inhibitors
reaction rate increases with increasing temperature
rate decreases above optimum temperature
pH
maximum reaction rate at optimum pH
above or below decreases rate- denatures enzyme
stomach- pH 2.0 small intestine- 8.0
Na+
high or low Na+ in external environment disrupts hydrogen bonds holding 3-D shape
competitive inhibitors
bind active site with a shape similar to substrate
permanent competitive inhibitor
binds permanently to active site
inactivates enzyme
antibiotics (penicillin) bind bacterial enzymes
temporary competitive inhibitor
temporarily binds active site
slows enzyme activity
sulfanilamide
temporary competitive inhibitor
blocks folic acid synthesis in bacteria
similar to PABA
carbon monoxide
temporary competitive inhibitor
competes with oxygen for hemoglobin
non competitive inhibitors
bind allosteric site changing shape of active site
temporary non competitive inhibitor
temporarily binds allosteric site
reaction products
temporary non competitive inhibitor
increasing product stops production
decreasing product turns it back on
permanent non competitive inhibitor
permanently binds allosteric site to inactivate enzyme
ex: cyanide
negative feedback
excess final product inhibits first enzyme in pathway
product controls own production
prevents excess products or intermediates from accumulating
does not waste substrate when product is not needed
enzyme activity resumes as product level decreases
ribozymes
non protein enzymes in eukaryotic cells and some viruses
acts as catalyst, has active site, is not used up during reaction
uses RNA as substrate
functions as genetic material and catalytic enzyme
