cell transport across plasma membrane Flashcards
where is Na+ most abundant
outside the cell
where is K+ most abundant
inside the cell
what are Na+ ions balanced by
Cl- ions
what are K+ ions balanced by
charges of organic molecules
what is a voltage difference
small excesses of positive or negative charge on two sides of plasma membrane
membrane potential
the voltage difference across the membrane
resting membrane potential
the steady exchange of anions and cations across the membrane for a cell at rest
what creates membrane potential
ion channels
how do ion channels create membrane potential
ion channels create openings for passive movement of inorganic ions
which channel is responsible for the resting membrane potential
K+ leak channels
Na+-K+ pumps also contribute
what is the range of the charge of resting membrane potential in animal cells (mV)
-20 to -200 mV
AT REST, what is the plasma membrane most permeable to
K+
Most channels in the cell are what kind of channels?
ion channels
what do ion channels do
facilitate passage of select inorganic ions
ion channels vs. pores
- ion selectivity
- open/closure state
(T/F) ion channels are continuously open
FALSE
ion channels fluctuate between closed and open conformations
(T/F) most ion channels are gated
TRUE
what kind of gate ion channels are there
- ligand-gated
- voltage gates
- mechanically gated
- always open (leak channels)
voltage-gated ion channels
controlled by changes in the voltage across the membrane
moves down concentration gradient
ligand gated ion channels
controlled by the binding of a molecule
- polar substance more concentrated on outside
- binding of stimulus molecule (ligand) causes pore to open
- polar substance can diffuse across membrane
mechanically gated ion channels
controlled by physical stimuli
ex. light, sound waves, pressure, stretch, touch, vibration
moves down concentration gradient
what is a neuron made up of
cell body, axon, dendrites
what does an electric signal consist of
changes in the membrane potential across neuron’s plasma membrane
(T/F) liposomes are impermeable to most water-soluble molecules
TRUE
what do membrane transport proteins do
facilitate the passage of selected small water-soluble molecules
what affects diffusion rate
molecule’s size and solubility
(T/F) lipid bilayers are impermeable to ions and most uncharged polar molecules
TRUE
only small nonpolar molecules can pass through
what are the two classes of membrane proteins
- transporter
- channel
transporter protein
transfer small organic molecules/inorganic molecules
channel proteins
form tiny hydrophilic pores and allow substances to pass by diffusion
passive vs. active transport
active transport requires energy/ATP
downhill movement
molecules flow from a region of high concentration to low concentration
passive transport
requires no energy
downhill movement
–> moves solute down its gradient
change conformation to mediate transport
active transport
requires energy
uphill movement
–>against concentration/electrical gradient
transport of uncharged molecule
movement direction determined ONLY by concentration gradient
transport of charged molecule
both concentration gradient and membrane potential exert forces
electrochemical gradient
net driving force moving a charged solute
force from membrane potential + force from concentration gradient
osmosis
diffusion of water across membranes
what channels do water molecules diffuse through
diffuse rapidly through aquaporin channels in the plasma membrane of some cells
what are aquaporin channels responsible for
water reabsorption in kidneys
3 types of proteins for active transport
- uniporter : transports one substance in one direction
- symporter : transports 2 different substances in the same direction
- antiporter : transports 2 different substances in opposite directions
uniporter
transports one substance in one direction
symporter
transports 2 different substances in the same directionan
antiporter
transports 2 diff substances in opposite directions
3 types of energy sources in active transport
- ATP (primary at)
- electrochemical gradient (secondary at)
- light
what is plasma membrane made of
thin fatty film studded w proteins and coated with carbs
plasma membrane functions
- cell communication
- import/export of molecules
- cell growth
- motility
phospholipid structure
hydrophilic head, hydrophobic tails
saturated vs. unsaturated fatty acid
saturated = no double bond
triacyglycerol
main constituents of animal fats and plant oils
–> completely hydrophobic
amphipathic
both hydrophilic and hydrophobic parts
first law of thermodynamics
total amt of energy in the universe must always be the same
what do all animals live off of
energy stored in chemical bonds of organic molecules
where does energy ultimately come from
the sun
photosynthesis
process that converts the electromagnetic energy in sunlight into chemical-bond energy in organic molecules
how is energy extracted from organic molecules
gradual oxidation
oxidation
addition of oxygen atoms to a molecule
second law of thermodynamics
in the universe, the degree of disorder can only increase
entropy: measure of a system’s disorder
how do cells follow the second law of thermodynamics
disorder increases when useful energy that could be harnessed to do work (free energy) is dissipated as heat
Gibbs free energy (G)
amount of energy available in a molecule to do work in a system when the temp and pressure are uniform
what is free energy measured in
joules
how can chemical reactions in a cell cause disorder
- by breaking apart a long chain of molecules or by disrupting an interaction that prevents bond rotations
- charges of bond energy of the reacting molecules can cause heat to be released
formula for free energy change
A+B –> C+D
(delta)G = free energy (C+D) - free energy (A+B)
what does delta G represent
amt of disorder created when a reaction involving these molecules takes place
what does a negative delta G represent
disorder of the universe increases
what does delta G at 0 mean
system is at equilibrium
standard free change
delta G^0
used to predict the outcome of a reaction
endergonic reactions
reaction with a positive change in free energy
exergonic
reaction with a negative change in free energy –> release energy
spontaneous reactions
reaction product has a lower free energy level = more stable
are exergonic or endergonic reactions energetically favorable
exergonic
endergonic reactions
require energy, can store energy in bonds
non-spontaneous
reaction product has a higher free energy level than substrate
transferable chemical group/readilt transferable election
as a readily transferable chemical group or as readily transferable electrons
what are the most important activated carriers
ATP, NADH, NADPH
what is the most widely used activated carrier
ATP
what group does ATP carry
phosphate
what group does NADH, NADPH, FADH2 carry
electrons and hydrogens
what group does acetyl CoA carry
acetyl group
what group does carboxylated biotin carry
carboxyl group
what group does S-adenosylmethionine carry
methyl group
what group does uridine diphosphate glucose carry
glucose
what do enzymes do
act as catalysts and lower activation energy
2 sets of metabolic pathways
catabolic and anabolic
catabolic metabolism
process of cellular respiration
anabolic metabolism
process of photosynthesis
where do light-reactions take place
thylakoid membrane
where does the carbon-fixation take place
stroma
how to light reactions convert light energy into chemical energy
form of ATP and reduced electron carrier NADPH
carbon fixation reactions
light-independent reactions –> use ATP, NADPH, and CO2 to produce carbohydrates
what is light
electromagnetic radiation
photons
particles of light
shorter wavelength = ?
greater energy
what light do chlorophylls absorb
light of blue and red wavelengths
photosystem
complex of proteins and pigments in thylakoid membrane
2 parts of the photosystem
- antenna system
- reaction center
what does the antenna system do
pigments absorb light energy and transfer it to chlorophyll a in the reaction center
what are electrons from chlorophylls in the reaction center transferred to
electron acceptor
where are electrons transported in photosynthesis
thylakoid membrane
what provides electrons for chlorophylls in the reaction center
water molecules split to provide electrons
protons are transferred from the stroma to where?
interior of the thylakoids
what do the light reactions of photosynthesis lead to the production of
- ATP
- NADPH
- O2
carbon fixation
uses ATP and NADPH to convert CO2 into sugar
what does carbon fixation consume ATP/NADPH to form
glyceraldehyde-3-phosphate
glyceraldehyde-3-phosphate (G3P)
3 CO2 + 9 ATP + 6 NADPH
glycolysis
converts glucose –> 2 pyruvate and some ATP
anaerobic
cellular respirationg
uses O2 to convert 1 pyruvate –> 3 CO2
fermentation
converts pyruvate into lactic acid or ethanol
oxidizing agent
reactant that becomes reduced
when do redox reactions occur
during the formation of a salt
between glucose and O2, which is the REDUCING agent
glucose
key electron carrier in redox reactions
coenzyme NAD+
aerobic metabolic process
- glycolysis
- pyruvate oxidation
- citric acid cycle
- electron transport/ATP synthesis
anaerobic metabolic processes
- glycoysis
- fermentation
where does glycolysis take place
cytoplasm, 10 steps
net result of glycolysis
2 pyruvate + 2 ATP + 2 NADH
3 phases of glycolysis
- energy consuming phase –> requires ATP
- cleavage phase
- energy-releasing phase –> produce ATP and NADH
what pathways does cellular respiration include
- pyruvate oxidation
- citric acid cycle
- ETC/ATP synthesis
where does cellular respiration take place
in the mitochondria
where does pyruvate oxidation occur
mitochondrial matrix
results of one citric acid cycle
2 CO2 + 3 NADH + 1 GTP + 1 FADH2
** cycles operates 2 times for 1 glucose
what is the starting point for the citric acid cycle
acetyl coa
citric acid cycle
8 reactions, acetyle group oxidized to 2 CO2
step 8 of citric acid cycle
oxidation of malate, NAD+ –> NADH, malate –> oxaloacetate
results of the oxidation of 1 glucose
- 6 CO2
- 10 NADH
- 2 FADH2
- 4 ATP
oxidative phosphorylation
2 steps:
- electron transport : electrons from NADH and FADH2 pass through respiratory chain –> create concentration gradient
- chemiosmosis” protons diffuse back to mitochondrial matrix –> ATP is made
where does proton pumping create an electrochemical gradient
inner mitochondrial membrane
electron transfers cause movement of protons where?
matric to intermembrane space
what kind of motor is the mitochondrial ATP synthase
rotary motor
results of lactate fermentation
2 lactate + 2 ATP
results of ethanol fermentation
2 ethanol + 2 CO2 + 2 ATP
how does the cycle of fermentation regulate itself
NADH gives up its electrons in the cytosol and converts back into NAD+ that glycolysis can use
metabolites
regulatory molecules
3 types of endocytosis
- receptor-mediated endocytosis (specific intake)
- pinocytosis (fluid)
- phagocytosis (particles)
2 types of exocytosis
release of large molecules
release of small molecules
2 types of membrane proteins
- integral : extend through lipid bilayer
- peripheral: interact with integral membrane proteins
how are integral proteins removed
can only be removed by disrupting the bilayer with detergents
(T/F) distribution of membrane proteins is asymmetrical
TRUE
transmembrane protein
integral protein that extends all the way through the phospholipid bilayer
how does an integral membrane protein cross the lipid bilayer
as an a helix
how do plasma membrane proteins move in the bilayer
laterally
how do cells confine particular proteins to localized areas
- binding meshwork of proteins inside cell
- binding proteins on surface of another cell
- diffusion barriers
- binding extracellular matrix molecules
membrane domains
functionally specialized regions
cell cortex
framework of proteins that support cell membrane
sugar coating on cell curface
carbohydrate layer/glycocalyx that functions in cell recognition and adhesion
3 types of cell junctions that connect adjacent cells
- desmosomal adhesion
- tight junctions
- gap junctions
desmosomal junctions
cell structure specialized for cell=cell adhesion
randomly arranged on lateral sides of cell
tissues faced with mechanical stress
tight junctions
protein complex between 2 cells that creates a seal to prevent leakage of content through membranes
gap junctions
allow intracellular flow of ions and molecules between cytoplasms
cell theory
- cells are the fundamental units of life
- all living organisms are composed of cells
- all cells come from preexisting cells
bright-field microscopy
light passes directly through cells
details not distinguished
phase contrast microscopy
contrast increased by emphasizing differences in refractive index
enhances light and dark regions in cell
differential interference contrast microscopt
2 beams of polarized light are used
looks as if cell is casting a shadow on one side
stained bright-field microscopy
stain enhances contrast, reveals details not otherwise visible
fluroescence microscopy
natural substance in cell that binds to a specific material is stimulated by a beam of light
confocal microscopy
fluorescence materials are used –> adds sustem of focusing both stimulating and emitted light
2D image
scanning electron microscopt (SEM)
electrons are directed to the surface of the sample where they cause other electrons to be emitted
nuclear lamina
involved in most nuclear activities
rough ER
site of protein synthesis
smooth ER
site of glycogen degredation, lipid/steroid synthesis, calcium ion storage
golgi apparatus
site of protein modification and sorting
adds carbs to proteins
lysosomes
site of macromolecule digestion
mitochondria
sites of energy transformation
chloroplasts
site of photosynthesis in plants
chromoplasts
make/store red, yellow, orange pigments
leucoplasts
store starch
peroxisomes
accumulate toxic peroxides
vacuols
storage compartment in plants
what happens at the nerve terminal
electric signal is converted to chemical signal
what happens at a synpase
chemical signal converted into electrical signal
