Unit 1: Cell metabolism/Membrane transport Flashcards
metabolism
the sum of all physical and chemical reactions occurring within a living system
anabolism VS catabolism
1st law of thermodynamics
energy cannot be created or destroyed
2nd law of thermodynamics is that all things tend towards:
disorder (= entropy)
activation energy
litle bit of energy is always required for all reactions
enzyme function is based on
shape
also- (how charges are distributed + size)
enzymes are NOT _____________________ in the reaction
altered or used up
[may be re-used multiple x]
enzymes are able to change ______ during reaction
shape
what are the different types of regulation of enzyme function?
- control of enzyme synthesis
- control of enzyme activity [competitors/ allosteric]
- Cofactors [usually minerals] & coenzymes [usually vitamins]
2 types of cellular respiration
A. Aerobic respiration
-requires oxygen
-most efficient (36-38 ATP)
B. Anaerobic respiration
-does not require oxygen
-less efficient
Glycolysis
location:
reactants:
products:
ctyoplasm
Glucose
>
2 ATP, 2 NADH, pyruvates
Citric acid cycle
AKA Krebs / TCA cycle
location:
reactants:
products:
mitochondria
pyruvate (2)
>
2 ATP
10 NADH
6 Co2
Electron transport system
location:
reactants:
products:
mitrochondria
12 NADH [10 NADH & 2 FADH2]
O2
>
32 ATP
6 H2O
Anaerobic cell metabolism
[lactic acid fermentation]
location:
reactants:
products:
Cytoplasm
glucose
>
2 ATP [per glucose]
Lactic acid
enzymes can increase the odds that a reaction will occur by lowering the :
activation energy of the reaction
Binding a molecule to an enzyme at a location different from the enzymes active site results in inhibition of the enzymes function. This type of interaction is called:
non-competitive inhibition
allosteric binding
Which of the three major steps of aerobic respiration does NOT occur in the mitochondria?
glycolysis
The point when increasing the amount of substrate no longer increases reaction rate because the active site of every enzyme is continually refilled with substrate, is a point described as:
saturation
What type of bond, if any, is broken when an enzyme is denatured?
hydrogen bond
A solution is a mixture of:
solvent [the fluid medium]
&
solutes [molecules dissolved into the fluid]
the plasma membrane acts as a selectively permeable barrier that regulates:
what may cross into / out of the cell
passive transport
Movement due to physical law (high > low)
cell not required to contribute
—Diffusion—
[simple diffusion]
simple diffusion
type of passive transport
net movement of molecules from a region of high concentration to low concentration until equilibrium is reached
In facilitated diffusion, a _______ ________ is needed to carry the molecule across a membrane.
protein carrier
[molecules still move high to low]
osmosis is a type of ______ transport
passive
_________ is the net movement of water across a selectively permeable membrane from a region of LOW solute concentration to HIGH solute concentration until equilibrium is reached
Osmosis
Tonicity
relative osmotic pressure
Osmotic pressure measures the ________ driving the movement
force/energy
hypertonic VS hypotonic
hypertonic- high concentration; high osmotic pressure
hypotonic- low concentration; low osmotic pressure
isotonic
same concentration & osmotic pressure
enzymes are not _______ __ ______ ____ in the reaction
altered or used up
enzymes are able to change ______ during reaction
shape
Enzyme function is dependent on their 3d shape which can be disrupted by:
temperature (heat)
pH
enzyme function can be regulated by controlling the # of active enzymes by:
controlling rate of synthesis or removal
using regulators to inhibit/activate enzymes
Enzyme-regulated reactions can be regulated by :
controlling substrate availability
-by sequestration
-by coenzymes
or by controlling ATP availability
A coffee maker is an example of a _________ gradient
pressure
A pressure gradient is
AKA filtration
movement due to a pressure difference
[hydrostatic pressure]
active transport requires
energy from the cell
in active transport, molecules are pushed across the membrane at the expense of :
energy [against the flow]
[using ATP]
primary VS secondary active transport
primary- protein pump uses ATP; ATP is used to move molecules from low to high concentration area
secondary- also relies on ATP; similar, but molecule A diffuses causing movement of molecule B
endocytosis
AKA phagocytosis
taking in of matter by a cell by invagination of its membrane to form a vacuole.
Membrane transport falls into 3 main categories:
enzymes
recognition / cell identity markers
cell to cell binders
receptors
transporters are all functions of:
membrane proteins
Osmosis is the movement of _________
across a selectively permeable membrane from an area of ______concentration to ____concentration until equilibrium is reached.
solvent
low
high
What are the similarities and differences between passive diffusion and osmosis?
similarities- both do not require energy
difference- which molecular class is moving?
diffusion- solute molecule is moving from high - low
osmosis- solvent molecule moving from low to high solute concentration [low osmotic conc/pressure > high osmotic conc/pressure]
the _____________[1]____________ describes the effect of membrane permeability to different ions on membrane potential. This equation can be used to determine the ________[2]_______at any given time.
[1] Goldman-Hodgkin-Katz equation
[2] membrane potential [electrical charge difference from one side to another]
The Nernst equation is derived from Goldman-Hodgkin-Katz equation and indicates the effect of the permeability of :
one ion alone.
The________ ___________can be used to determine the equilibrium potential that could be reached if the membrane became permeable to the given ion, which in turn indicates the driving force (chemical and electrical) influencing ion movement.
Nernst equation
According to the Goldman-Hodgkin-Katz (GHK) equation ions will have no effect on membrane potential if they are :
not permeable across the membrane.
The Nernst equation is a simplification of the Goldman-Hodgkin-Katz (GHK) equation – what is the Nernst equation used to determine?
the “equilibrium potential” for an ion when it was permeable
Gated ion channels need a trigger (often described as a key) to cause them to open. These gated ion channels may be identified by the ion that they transport or by the key that opens them. The labels that describe a gated channel by the type of key needed to open a channel includes:
ligand gated
voltage gated
mechanically gated
chemically gated
true or false-
When a cell is at rest (at its resting membrane potential) it is inactive and is not using any energy.
false
true or false-
The membrane potential of a cell is due exclusively to the distribution of ions on either side of the membrane.
false
___________ are solute particles that are not permeable across a membrane
osmoles
ex) NaCl > Na+, Cl- becomes to 2 ion particles
binding affinity determines:
effectiveness of an enzyme
osmoles are solute particles that
are not permeable through membrane
always use osmolarity when describing:
osmosis
hydrolysis VS condensation
condensation- joining of 2+ molecules to form a larger molecule
hydrolysis - breaking of a large molecule into smaller molecules by the addition of a water molecule.
Explain the lock and key model of enzyme action.
a lock and a key fit together precisely like a specific substrate fits in an active site of an enzyme
~function is dependent on a specific fit
Explain how temperature influences enzyme activity.
~reaction rate increases as temperature/heat increases [up to the critical amount/threshold temperature of 40 C, then slows and can denature enzyme]
Explain the roles of cofactors and coenzymes
Cofactors- typically minerals, must be present as the substrate is interacting with the enzyme
ex) acting as an allosteric binder needed for the active site to be right shape to match the correct substrate
ex) may also interact within the active site, producing the same outcome of altering the shape of the active site to allow it to interact with the substrate
Coenzymes- typically vitamins
-acts the same as cofactors
-another role: may be necessary for carrying away a product away from the enzyme
What does allosteric binding mean?
AKA non-competitive
non-competitive inhibitor latches on to a site different than the active site, but the shape of the active site then changes so the substrate cannot fit; the enzyme’s function is turned off [deactivated].
What does competitive binding mean?
~a close fit can get in the way
~Similarly shaped substrate can nest up against enzyme and almost fit, so it is getting in the way of correct substrate binding
What are the three major steps in aerobic cellular respiration?
1) Glycolysis
2) Citric acid cycle AKA Krebs Cycle AKA TCA cycle
3) Electron transport system
What are the different names for the “citric acid cycle”?
Krebs Cycle
TCA cycle- tricarboxylic acid cycle
What is the function of NAD in “aerobic respiration”?
NAD is a coenzyme and necessary for carrying away 2 hydrogen ion + electron products of chemical reactions
Almost all of the energy out of glucose is carried away by the NAD
Enzyme specificity - enzyme is specific to certain __________ and vice versa
substrates
Enzymes exhibit saturation: enzyme’s influence is determined by ___________ that can interact simultaneously
of enzymes
enzymes cannot force reactions to occur but can increase the :
frequency of reactions [odds of a reaction occuring]
Explain how pH influences enzyme activity.
enzymes have different optimal pH levels depending on their environment
pH affects # of hydrogen bonds
________ is the energy currency of the cell
ATP
Describe the two different forms of “anaerobic respiration”. What are the products of each
Lactic acid fermentation
products: lactic acid
&
Alcohol fermentation
products: ethanol or acetaldehyde & Co2
the plasma membrane acts as a ___________________________ that regulates what may cross into or out of the cell
selectively permeable barrier
Passive transport:
Simple Diffusion - net movement of molecules from a region of __________________________________ towards equilibrium
high concentration to a region of lower concentration
Passive transport/ simple diffusion is influenced by:
concentration gradient (molarity)
permeability
temperature
size (MW)
surface area.
Facilitated Diffusion involves :
a protein carrier = carrier mediated
Osmosis is influenced by:
concentration gradient (osmolarity)
solute permeability
water permeability (aquaporins)
temperature
size (MW)
surface area
Define “Potential”.
describes the differences between 2 solutions that can impart movement onto solute/solvent molecules or impart movement due to charge differences of 2 environments
-measures a electrical gradient/ difference
basically potential energy
Solute is
molecules dissolved into the fluid/solvent
Solvent is
the fluid medium, often water
List and describe the different functional types of membrane proteins. What do they do?
~Transporters: produce controlled/selective permeability of the membrane
~Receptors: respond to a molecule that fits into an active site and produce a shape change that can produce some response
~Enzymes: help catalyze chemical reactions
~Attachment/adhesion: attach cells together
~Recognition: identify cell and recognize similar cell types or cells that do/don’t belong to an organism
What are the 4 types of passive transport?
Simple diffusion
Facilitated Diffusion
Osmosis
Filtration/ Pressure gradient
Describe the different types of protein transporters
~Pore/leak channel- open protein with a hollow core that allows molecules to move through from high to low conc.
~Gated channel- requires “key” to open; rapidly opens/closes
~Facilitated transporter- no open passageway; never fully open; acts like a revolving door
~Active transporter “pump” uses ATP to go thru shape change; low to high conc.
What is osmotic pressure?
the force/energy of osmotic water movement due to a concentration (measured as the pressure needed to exactly oppose osmotic movement = equilibrium)
It’s actually a concentration, not really a pressure
Explain how “hypertonic”, “isotonic” and “hypotonic” solutions will affect the cell.
isotonic- no change to cell; same conc.
hypertonic solution- osmotic movement of water outside of cells; cells will shrivel/shrink/crenate
hypotonic solution- osmotic movement of water inside cell = cells swell up; may rupture (lysis).
What is filtration? What is the driving force for molecular movement?
AKA pressure gradient
~driven by movement from high to low hydrostatic pressure
Movement due to pressure difference
[hydrostatic pressure]
Define “active transport”. What do cells use active transport for?
Molecules moved from low to high conc. against their spontaneous flow, so ATP energy is required
~May need to purge things that leak into the cell to remove them
~sometimes so cell can accumulate things in high conc.
Name the different forms of bulk transport. Why is this sometimes NOT described as membrane
transport?
~Not true membrane transport because the molecules being moved never cross over the membrane, but moved from in/out of cell
REQUIRES ENERGY :
~Endocytosis AKA phagocytosis: movement in; plasma membrane creates folds/invagination; pocket closes and becomes a vesicle enclosed in the cell
~Exocytosis: movement out. Vesicle goes against the membrane and then opens to eject contents
In terms of molecular movement, what does “equilibrium” mean?
equal movement of materials in both directions
What is an “equilibrium potential”?
AKA Nernst potential, [way to calculate E.P.]
~balance point for ions (like sodium, potassium, chloride, or calcium) across a cell’s membrane; It’s the point where ions stop moving because the forces pushing them in and out of the cell, based on their concentration and electrical charge, are in perfect balance
~helps understand how cells maintain electrical balance and how signals are transmitted in our bodies.
The Nernst potential for sodium is +65mv and for potassium it is –90mv. At rest cells are not very permeable to sodium and have a membrane potential of -70mv. What does this tell you about potassium permeability?
The cell’s normal resting state is at -70 mV (millivolts).
Sodium’s “happy place” is at +65 mV, and potassium’s is at -90 mV.
Since the cell is resting at -70 mV, the cell is more open to letting potassium in and out compared to sodium.
So, potassium can move more freely across the cell membrane at rest while sodium has a harder time because it’s further away from its happy place. The cell is more permeable to potassium at rest.
A real solution will be __________ to light & will not separate
transparent
Protein transporters exhibit which characteristics?
specificity
competition
saturation
[same as enzymes]
Describe the structure and characteristics of phospholipids. How do phospholipids interact with water and each other?
Phospholipid structure
~Hydrophilic head [w/ polar phosphate group and glycerol molecule]
~2 hydrophobic tails [long hydrocarbon chains made of fatty acids]
~Hydrophilic head is attracted to water, allowing a boundary between watery and non water space
while the tail avoids water and interacts with each other, creating stable bilayer
What other components make up the cell membrane? Describe the overall structure of the cell membrane. Identify all of the components and their orientation in the membrane.
Phospholipid Bilayer: basic structural framework- head & 2 tails
Proteins: embedded within bilayer or near membrane surface
Cholesterol: spacers between the layers to keep the membrane strong and flexible.
Carbohydrates: attached to lipids or proteins; help the cell identify other cells and communicate with them.
Are all of the steps of aerobic cellular respiration “one way”? What is the significance of this?
No, not one way
Glycolysis is reversible, [glucose & glycogen]
Do proteins and fats enter the metabolic pathway at the same point as carbohydrates?
Carbohydrates: Enter at the front end of the pathway
Proteins: First, they have to be taken apart into amino acids. Then, these pieces join the energy-making process at different spots. enter further down the pathway. [enter during step 2]
Fats (Lipids): First, they need to be broken down into glycerol/ fatty acids, and then enter the energy-making process at different stages. [enter in between 1 -2 ]
When is the sodium-potassium pump actively pumping?
What is the significance of the sodium-potassium pump?
it uses ATP;
pumps sodiums that leaked into the cell right out; pumps potassium that leaks out get pumped back in
compensates for any leakiness to maintain the concentration differences of Na and K
~going on all the time
~maintaining ion distribution responsible for electrical charges of the cell
~regulates excitability, neuronal signaling, muscle contraction, and overall cellular function.
What 3 molecules are always involved in the activity of a gated channel?
1) the protein molecule that is the gated channel
2) ion moving through the gated channel when open
3) the key that opens/closes gated channel
a ligand-gated channel is opened by:
a chemical key
AKA chemical gated channel
ex) a neurotransmitter can act as a key to open channel
How does a voltage-gated channel work?
If reaches a minimum voltage quantity it will cause the protein structure of the gated channel to change and open
Membrane protein types:
Transporters: these proteins produce:
controlled/selective permeability of the membrane
Membrane protein types:
Receptors: These proteins respond to a molecule that fits into an active site and produce :
a shape change that can produce some response
Membrane protein types:
Enzymes: These proteins help :
catalyze chemical reactions
Membrane protein types:
Attachment/adhesion: These proteins work to:
attach cells together
Membrane protein types:
Recognition: These proteins identify:
cells and recognize similar cell types or cells that do/don’t belong to an organism
[Protein transporter type]
Pore/leak channel- has :
an open protein with a hollow core that allows molecules to move through from high to low conc.
[Protein transporter type]
Gated channel-
requires “key” to open; rapidly opens/closes
[Protein transporter type]
Facilitated transporter-
no open passageway; never fully open; acts like a revolving door
[Protein transporter type]
Active transporter -
“pump” uses ATP to go thru shape change; low to high conc.
