Molec Cell Exam 2 Flashcards
Explain simple diffusion
Simple diffusion is when molecules spread from an area of high to low concentration without a protein
Which ion is the most abundant inside the cell and which ion is abundant outside the cell
Na+ is the most plentifully positively charged ion outside the cell and K+ is the most abundant inside the cell
What are two main classes of membrane transport proteins
Channels discriminate mainly basis on size and electrical charge when channels are open only ions of appropriate size and charge can pass through.
Transporter transfers only those molecules
or ions that fit into specific binding sites on the protein. Transporters bind
their solutes with great specificity
Active versus passive transport
Passive transport is when substances moves from high to low concentration or down the concetration without expenditure of energy by the transmembrane protein
Active transport is the movement of a solute against its concentration gradient and is carried out transporters called pumps which harness source an energy to power the transport process
What determines the direction in which each solute will flow across the membrane?
The electrochemical gradient
Explain the process of osmosis
movement of water down its concentration gradient—from an area
of low solute concentration (high water concentration) to an area of high
solute concentration (low water concentration)
What are the major functions of the transporters
Transporters are responsible for the movement of most small, water
soluble, organic molecules and a handful of inorganic ions across cell
membranes.
Each transporter is highly selective, often transferring just
one type of solute.
To guide and propel the complex traffic of substances
into and out of the cell, and between the cytosol and the different mem
brane-enclosed organelles, each cell membrane contains a characteristic
set of different transporters appropriate to that particular membrane
3 ways transmembrane proteins can carry out active transport
Gradient-driven pumps link the uphill transport of one molecule across the cell membrane to the downhill transport of another
ATP-driven pumps use the energy released by the hydrolysis of ATP to drive uphill transport
Light driven pumps use energy dervied from sunlight to drive uphill transport
How do channels and transporters mediate transfer
Transporters: shift small organic molecules or inorganic ions from one side of the membrane to another by changing shape
Channels: form tiny hydrophilic pores across the membrane through which substances can pass by diffusion (most only permit ions to pass through ion channels)
Explain facilitated transport
Facilitated transport is the process by which specialized membrane transport proteins accelerate the passage of molecules across the membrane
Explain the permeability of small nonpolar molecules and uncharged polar molecules
Small nonpolar molecules such as molecular oxygen and carbon dioxide dissolve readily in lipid bilayers and diffuse rapidly
Uncharged polar molecules uneven electrical charge distribution can cross readily IF they are small enough.
Larger uncharged polar molecules like glucose barely cross
Describe membrane potential
electrical imbalances generate a voltage difference across the membrane
describe resting membrane potential
Resting membrane potential happens when a cell is unsimulated the movement of anions and cations across the membrane are precisely balanced
what is the electrochemical gradient
the net driving the charged solute across the membrane and is composed of two forces, one due to the concentration gradient and the other due to the membrane potential.
determines the
direction in which each solute will
flow across the membrane by passive transport
What are ways that solutes move across the cell membrane passively
Simple diffusion is the movement of substances along a concentration gradient. It does not require the involvement of carrier proteins or other molecules
Channel-mediated transport is a spontaneous passage of molecules or ions across the biological membrane passing through specific transmembrane integral proteins
Transporter mediated happens if the membrane needs transport water rapidly then it opens or channels in the membrane aquaporins
what are gradient-driven pumps
A gradient of any solute across the membrane can drive the active transport of another molecule
They can couple the
movement of one inorganic ion to that of another, the movement of an
inorganic ion to that of a small organic molecule
The downhill movement of the first solute, so [high] → [low] of the first solute, can be used to power the uphill movement of the second solute AGAINST its concentration gradient.
What is the differnce between a symport, uniport, and antiport
If the pump moves both
solutes in the same direction across the membrane, it is called a symport.
If it moves them in opposite directions, it is called an antiport.
A transporter that ferries only one type of solute across the membrane down
its concentration gradient (and is therefore not a pump) is called a uni
port
explain one of the antiport Na+ - H+ exchanger
For example, the
Na+–H+ exchanger in the plasma membrane of many animal cells uses
the downhill influx of Na+ to pump H+ out of the cell
explain how a sodium-potassium pump works
Sodium binds inside the cell
ATP → ADP
Pump phosphorylates
Conformational change
Releases Sodium and Binds potassium
How does the Electrochemical H+ Gradients Drive the Transport of
Solutes such as sugars and amino acids in Plants, Fungi, and Bacteria
H+ gradient is generated by H+
pumps in the plasma membrane that use the energy of ATP hydrolysis
to pump H+ out of the cell; these H+ pumps
Define channel proteins
Channel proteins, or
channels, perform this function in cell membranes, forming transmem
brane pores that allow the passive movement of small, water-soluble
molecules and ions into or out of the cell or organelle.
How can you distinguish ion channels from simple holes in the membrane
First, they show ion selectivity, permitting some inorganic
ions to pass but not others. Ion selectivity depends on the diameter and
shape of the ion channel and on the distribution of the charged amino
acids that line it
ion channels are not continuously open. Instead, ion channels open only briefly and then close again, most ion channels are gated: a specific stimulus triggers them to
switch between a closed and an open state by inducing a change in their
conformation
What are 3 ways ion channels can be gated and respond to a specific stimulus to be open and closed
For a ligand-gated channel, opening is controlled by
the binding of some molecule (a ligand) to the channel and causing conformational change
Stress/ Mechanically gated when there is physical pressure that physically changes the conformation of that protein
The auditory hair cells in our ears are mechanically gated.Sound vibrations pull the chan
nels open, causing ions to flow into the hair cells; this ion flow sets up
an electrical signal that is transmitted from the hair cell to the auditory
nerve, which then conveys the signal to the brain
Voltage-gated ion channels have domains called voltage sensors that
are extremely sensitive to changes in the membrane potential: changes above a certain threshold value exert sufficient electrical force on these
domains to encourage the channel to switch from its closed to its open
conformation
What happens during resting membrane potential
Equilibrium Condition no net flow of ions across the membrane
What is the fundamental task of a neuron
to receive, integrate,
and transmit signals. Neurons carry signals from sense organs, such as
eyes and ears, to the central nervous system—the brain and spinal cord
Describe the structure of a neuron
, a
neuron has one long extension called an axon, which conducts electrical
signals away from the cell body toward distant target cells;
several shorter, branching extensions called dendrites, which radiate from the cell body like antennae and provide an enlarged surface area
to receive signals from the axons of other neurons
The
axon commonly divides at its far end into many branches, each of which
ends in a nerve terminal, so that the neuron’s message can be passed
simultaneously to many target cells—
How does neurons solve a long distance communication problem
by employing
an active signaling mechanism. In this case, a local electrical stimulus
of sufficient strength triggers a burst of electrical activity in the plasma
membrane that propagates rapidly along the membrane of the axon,
continuously renewing itself all along the way.
This traveling wave of
electrical excitation, known as an action potential, can carry a message, without weakening, all the way from one end of a neuron to the other
describe the process of depolarization when it comes to the action potential
depolarization is sufficiently large, it will cause voltage-gated Na+
channels in the membrane to open transiently at the site. As these channels flicker open, they allow a small amount of Na+ to enter the cell down
its steep electrochemical gradient.
The influx of positive charge depolarizes the membrane potential even less negative), thereby opening additional voltage-gated Na+ channels and causing still further depolarization.
The depolarized axonal membrane is helped to return to its resting
potential by the opening of voltage-gated K + channels.
As the
local depolarization reaches its peak, K+ ions (carrying positive charge)
therefore start to flow out of the cell, down their electrochemical gradient
The Na+ channels remain in this inactivated state until the membrane potential has returned to its resting,
negative value.
K+ channels close as they bring the membrane back to its resting state Na+ channels reset and open and K+ diffuses out the cell and depolarizes the membrane
Describe the process of voltage gated channels in nerve terminals converting an electrical signal to a chemical signal
When an action potential reaches the nerve terminal some of the synaptic vessels fuse with the plasma membrane releasing neurotransmitter into the synaptic cleft
Which involves the activation of voltage gated Ca2+ channels located in the plasma membrane presynaptic nerve terminal
Ca2+ rushes into the nerve terminal through open channels increasing the concentration of Ca2+ concentration in the cytosol of terminal triggers the fusion of the synaptic vessel with the plasma membrane and releases the neurotransmitter into the synaptic cleft and been converted into a chemical signal
Explain the function of transmitter gated ion channels
These constitute a subclass of ligand-gated ion
channels and their function is to convert the chemical signal carried by a neurotransmitter back into an electrical signal.
The channels open transiently in response to the neurotransmitter’s binding, thus changing the postsynaptic membrane’s ion
permeability.
This in turn causes a change in the membrane potential
What is the difference between excitatory and inhibitory transmitters
Excitatory neurotransmitters open transmitter-gated cation channels
that allow the influx of Na+, which depolarizes the postsynaptic cell’s
plasma membrane and encourages the cell to fire an action potential.
Inhibitory neurotransmitters open transmitter-gated Cl– channels in
the postsynaptic cell’s plasma membrane, making it harder for the
membrane to depolarize and fire an action potential.
why does glucose have the lowest rate of diffusion across an artificial membrane ?
Glucose because it is large and needs assitance from transporters protein
K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated fashion. What do they accomplish in a resting state
They keep the electrochemical gradient for K+ at zero
What are the function of Ion channels
Ion channels allow inorganic ions of appropriate size and charge to
cross the membrane. Most are gated and open transiently in response
to a specific stimulus.
Ion channels also allow the passage of ions in both directions
Assume that a pump transports one Na+ ion in one direction and one K+ ion in the other direction during each pump cycle
What would happen if the vesicles inside and outside of the vesicles contain both Na+ and K+ ions but no ATP
The pump will not work because the pumps use free energy released from ATP hydrolysis to move the solutes across the cell membrane against an electrochemical gradient
The solution outside the cell the vesicles containing both Na+ and K+ ion the solution inside contains both Na+ and K+ ions and ATP
ATP will be used to pump Na out and K+inside. Thiis will stop once Na+ inside is all out of there in no more K+ outside.
Describe the two forces that drive Ions across the plasma membrane
Concentration gradient and membrane potential are the two forces
The solution outside contains Na+ the solution inside contains Na+ and ATP
Phospholation of goes on like normal kicking out Na, but will get stuck on this step because no K+ in there to bind to the conformational change
Which molecule in eachj pair is more likely to diffuse through the lipid bilayer
Amino acids or CO2
CO2 because it is a small uncharged molecule
Which molecule in eachj pair is more likely to diffuse through the lipid bilayer
Ethanol or Cl-
Ethanol because Cl- cannot directly pass through the lipid bilayer due to their charged nature and needs specialized protein channels
Describe ion channels
Ion channels are integral membranes proteins that allow certain ions to cross
Describe the behavior of a gated channel
It opens more frequently in response to a given stimulus
What typr of ion channels are found in the hair cells of mamalian cells
Mechanically gated
What are the most common type of receptors of neurotransmitters
Ligand gated ion channels
What are the transporters involved in relaying a neuron cell signal
Ligand gated
The high intracellular cincetration of K+ in a resting animal cell is mostly due to
the Na+ K+ pump in the plasma membrane
Ca2+ pumps in the plasma membrane and endoplasmic reticulum are important for
preventing Ca2+from altering behaivor of molecules in the cytosol
What mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential
by opening Cl- channels
How do voltage gated channels work
They open and close in response to changes in membrane potential
What effect does the action potential cause along the neuronal plasma membrane
Depolarization
Which channels open at repolarization
Voltage gated potassium channels
The acteylcholine receptor in skeletal muscle is what type of channel
A ligand gated ion channel
Chapter 13
What are acrtivated carriers ?
Activated carriers are molecules that can be split to release free energy such as ATP, NADH, and FADH2
What are two processes wherby sugars are broken down to generate energy ?
In both cases, the organism’s cells
harvest useful energy from the chemical-bond energy locked in sugars as
the sugar molecule is broken down and oxidized to carbon dioxide (CO2)
and water (H2O)—a process called cell respiration
How do animal cells make ATP
First, certain energetically favorable,
enzyme-catalyzed reactions involved in the breakdown of food-derived
molecules are coupled directly to the energetically unfavorable reac
tion ADP + Pi → ATP.
Thus the oxidation of food molecules can provide
energy for the immediate production of ATP.
Most ATP synthesis, how
ever, requires an intermediary. In this second pathway to ATP production,
the energy from other activated carriers is used to drive ATP synthesis.
This process, called oxidative phosphorylation, takes place on the inner
mitochondrial membrane of eukaryotic cells
Describe the three stages on how food molecules are broken down
This breakdown process—in which enzymes
degrade complex organic molecules into simpler ones—is called
catabolism.
In stage 1 of catabolism, enzymes convert the large polymeric molecules
in food into simpler monomeric subunits: proteins into amino acids,
polysaccharides into sugars, and fats into fatty acids and glycerol.
digestion—occurs either outside cells (mainly in the
intestine) or in specialized organelles within cells (called lysosomes. After digestion, the small organic molecules
derived from food enter the cytosol of a cell, where their gradual oxidative breakdown begins.
In stage 2 of catabolism, a chain of reactions called glycolysis splits each
molecule of glucose into two smaller molecules of pyruvate. Sugars other
than glucose can also be used, after first being converted into one of the
intermediates in this sugar-splitting pathway. Glycolysis takes place in
the cytosol and, in addition to producing pyruvate, it generates two types
of activated carriers: ATP and NADH. The pyruvate is transported from
the cytosol into the mitochondrion’s large, internal compartment called
the matrix. There, a giant enzyme complex converts each pyruvate molecule into CO2 plus acetyl CoA
Stage 3 of catabolism takes place entirely in mitochondria. The acetyl group in acetyl CoA is transferred to an oxaloacetate molecule to form
citrate, which enters a series of reactions called the citric acid cycle.
In these reactions, the transferred acetyl group is oxidized to CO2, with the
production of large amounts of NADH. Finally, the high-energy electrons
from NADH are passed along a series of enzymes within the mitochondrial inner membrane called an electron-transport chain, where the energy
released by their transfer is used to drive oxidative phosphorylation—a
process that produces ATP and consumes molecular oxygen (O2 gas
What is the definition of glycolysis
Glycolysis takes place in the cytosol
glycolysis splits a molecule of glucose, which has six carbon atoms, to form two molecules of pyruvate, each of which contains three carbon atoms.
ultimately generate pyruvate release
energy because the electrons in a molecule of pyruvate are, overall, at
a lower energy state than those in a molecule of glucose.
Nevertheless,
for each molecule of glucose that enters glycolysis, two molecules of ATP
are initially consumed to provide the energy needed to prepare the sugar
to be split.
This investment of energy is more than recouped in the later
steps of glycolysis, when four molecules of ATP are produced.
During this
“payoff phase,” energy is also captured in the form of NADH.
Thus, at the
end of glycolysis, there is a net gain of two molecules of ATP and two molecules
of pyruvate and 2 NADH
What are the steps of glycolysis
Step 1: In the first step, a phosphate group from ATP gets transferred to the glucose molecule present in the cell cytoplasm, producing glucose-6-phosphate. This step is catalyzed by the enzyme hexokinase.
Step 2: Next, the glucose-6-phosphate gets converted into its isomer, fructose-6-phosphate by the action of phosphoglucomutase.
Step 3: Another phosphate group gets transferred from ATP to fructose-6-phosphate to produce fructose-1,6-bisphosphate, under the influence of phosphofructokinase.
Step 4: In this step, the enzyme aldolase acts on the fructose-1,6-bisphosphate and splits it into dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate
Step 5: As DHAP cannot directly take part in the consecutive steps of the process, it gets converted into its isomer glyceraldehyde-3-phosphate by the enzyme triose-phosphate isomerase.
Step 6: Next, the enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) adds a phosphate from the cytosol to the glyceraldehyde 3-phosphate to form 1,3-bisphosphoglycerate. The same enzyme also dehydrogenates glyceraldehyde 3-phosphate by transferring one of its hydrogen (H⁺) molecules to the oxidizing agent NAD⁺ to form NADH and H
Step 7: After this, the 1,3-bisphosphoglycerate donates one of its phosphate groups to ADP, making a molecule of ATP and turning into 3-phosphoglycerate (3 PGA) in the process. As there are two molecules of 1,3-bisphosphoglycerate, the reaction yields two 3 PGA, and 2 ATPs.
Step 8:
3-phosphoglycerate gets converted into its isomer, 2-phosphoglycerate by the action of phosphoglyceromutase.
Step 9: In this step, the enzyme enolase acts on 2-phosphoglycerate and removes a molecule of water from it, thus producing phosphoenolpyruvate (PEP).
Step 10: As PEP is an unstable molecule, it loses one of its phosphate group in this step. The lost phosphate group gets to ADP under the influence of the enzyme pyruvate kinase. This step yields 2 molecules of pyruvate and 2 ATPs in the end. As this pyruvate enters the next phase of cellular respiration, it is considered as the end product of glycolysis
What happens to the 2 molecules of NADH after glycolysis
In eukaryotic organisms, these NADH
molecules are transported into mitochondria, where they donate their
electrons to an electron-transport chain that produces ATP by oxidative
phosphorylation in the inner mitochondrial membrane,
. These electrons pass along the electron-transport
chain to O2, eventually forming water
describe anaerobic microrganisms produce ATP in the presence of oxygen
many anaerobic microorganisms, which can grow and divide in the
absence of oxygen, glycolysis is the principal source of ATP.
.
In these anaerobic conditions, the pyruvate and NADH made by glycolysis remain in the cytosol
NAD+ required to maintain the reactions of glycolysis
What is fermentation ?
Such energy-yielding pathways that break down sugar in the absence
of oxygen are called fermentations
Glucose is taken and pyruvate and is converted into ethanol
What is pyruvate converted into in skeletal muscle
Lactate
Describe the two phases of glycolysis
- The energy requiring phase
2.Energy releasing phase
In the first phase 2 ATP molecules are used to split the glucose into glyceraldehyde 3 phosphate.
In the second phase the intermediate sugar is further catabolized to produce 4 ATP, 2NADH and 2 pyruvate molecules.
The net yield of glycosis is 2ATP 2PYRUVATE AND 2 NADH
What happens to pyruvate after glycolysis
Pyruvate is further oxidized in the mitochondria and converted into Acetyl COA and then enter into the citric acid cycle producing more NADH molecules and all NADH donate the electrons to the electron transport chain producing more ATP completing the oxidation of glucose.
How is pyruvate converted to Acetyl COA
Pyruvate is converted to Acetyl COA by the enzyme pyruvate dehydrogenase and takes place in the mitochondrial matrix
Pyruvate + NAD+ CoA gives us acetyl COA + NADH+ CO2
. This enzyme
complex removes a CO2 from pyruvate to generate NADH and acetyl CoA. Pyruvate and its products including the waste product, CO2—
What is the difference between the pyruvate kinase and phosphate
Pyruvate dehydrogenase kinase— deactivate
Pyruvate dehydrogenase phosphatase— activate
Define the citric acid cycle
The citric acid cycle, a series of reactions that takes place in the mito
chondrial matrix of eukaryotic cells, catalyzes the complete oxidation of
the carbon atoms of the acetyl groups in acetyl CoA.
The final product
of this oxidation, CO2, is released as a waste product
Describe the process of the Citric acid cycle
Acetyl COA comes into the 2-carbon molecule and combines with oxaloacetate the resident molecule of the citric acid cycle to form citrate.
All these high-energy molecules are going to be used to donate electrons to the electron transport chain in the mitochondria
Carbon dioxide is given off as waste product and for every 2 carbon acetyl CoA two carbon dioxide molecule are given off as a waste
For every cycle 3 water molecules are split 1 turn of a cycle 3 NADH and 1 GTP and 1FADH2 are produced and releasing carbon dioxide as a waste product
What’s an important molecule that the citric acid cyle needs
he cycle, however, requires O2 to proceed because
the NADH generated passes its high-energy electrons to an electron
transport chain in the inner mitochondrial membrane, and this chain
uses O2 as its final electron acceptor.
Oxygen thus allows NADH to hand
off its high-energy electrons, regenerating the NAD+ needed to keep the
citric acid cycle goin
What is the end products for citric acid cycle ?
6 NADH because ach glucose molecule is split into two molecules of pyruvate during glycolysis.
Each pyruvate is converted into acetyl-CoA, which enters the citric acid cycle.
For each acetyl-CoA, the citric acid cycle produces 3 NADH molecules.
Since one glucose molecule generates two acetyl-CoA molecules 2x3=6
2FADH2
r each acetyl-CoA molecule that enters the citric acid cycle, one molecule of FADH₂ is produced. Since one glucose molecule generates two acetyl-CoA molecules, the total FADH₂ produced per glucose molecule is:
2 acetyl-CoA
× 1 FADH₂
= 2FADH₂
In the citric acid cycle, one molecule of GTP (or ATP, depending on the cell type) is produced per acetyl-CoA molecule. Since one glucose molecule generates two acetyl-CoA molecules, the total GTP (or ATP) produced per glucose molecule is:
2 acetyl-CoA
× 1GTP (or ATP)
= 2GTP (or ATP)
4CO2
For each acetyl-CoA molecule that enters the cycle, two molecules of CO₂ are released. Since one glucose molecule generates two acetyl-CoA molecules, the total CO₂ produced per glucose molecule is:
2 acetyl-CoA
×2 CO₂= 4CO₂
Describe anabolic pathways
anabolic pathways, in which the inter
mediates are converted by a series of enzyme-catalyzed reactions into
amino acids, nucleotides, lipids, and other small organic molecules that
the cell needs.
describe the 8 steps of the citric acid cycle
After the enzyme removes
a proton from the CH3 group on acetyl CoA, the negatively charged CH2–
forms a bond to a carbonyl carbon of oxaloacetate.
The subsequent loss of the coenzyme A (HS–CoA) by
hydrolysis drives the
reaction strongly forward.
STEP 2
An isomerization reaction,
in which water is first
removed and then added
back, moves the hydroxyl
group from one carbon
atom to its neighbor
STEP 3
In the first of four
oxidation steps in the
cycle, the carbon carrying
the hydroxyl group is
converted to a carbonyl
group. The immediate
product is unstable, losing
CO2 while still bound to
the enzyme.
STEP 4
The α-ketoglutarate dehydrogenase
complex closely resembles the large
enzyme complex that converts
pyruvate to acetyl CoA, the pyruvate
dehydrogenase complex in Figure
13–10. It likewise catalyzes an
oxidation that produces NADH, CO2,
and a high-energy thioester bond to
coenzyme A (CoA).
STEP 5
An inorganic phosphate
displaces the CoA, forming a
high-energy phosphate
linkage to succinate. This
phosphate is then passed to
GDP to form GTP. (In bacteria
and plants, ATP is formed
instead.)
STEP 6
In the third oxidation step of the
cycle, FAD accepts two hydrogen
atoms from succinate.
STEP 7
The addition of water to
fumarate places a hydroxyl
group next to a carbonyl
carbon
In the last of four oxidation
steps in the cycle, the carbon
carrying the hydroxyl group is
converted to a carbonyl group,
regenerating the oxaloacetate
needed for step 1.
What is the final stage in the oxidation of food molecules
Oxidative phosphorylation isoxidative phosphorylation.
It is in this stage that the chemical energy
captured by the activated carriers produced during glycolysis and the citric acid cycle is used to generate ATP.
During oxidative phosphorylation,
NADH and FADH2 transfer their high-energy electrons to the electron
transport chain a series of electron carriers embedded in the inner mitochondrial membrane in eukaryotic cells (and in the plasma mem
brane of aerobic prokaryotes).
As the electrons pass through the series of
electron acceptor and donor molecules that form the chain, they fall to successively lower energy states.
At specific sites in the chain, the energy
released is used to drive protons (H+) across the inner membrane, from
the mitochondrial matrix to the intermembrane space
This movement generates a proton gradient across the inner membrane,
which serves as a source of energy
At the end of the transport chain, the electrons are added to molecules of
O2 that have diffused into the mitochondrion, and the resulting reduced
oxygen molecules immediately combine with protons from the surround
ing solution to produce water
How do you increase the availability of glucose
One way to increase available glucose is to synthesize it
from pyruvate by a process called gluconeogenesis.
Gluconeogenesis is, in many ways, a reversal of glycolysis: it builds
glucose from pyruvate, whereas glycolysis breaks down glucose and produces pyruvate.
Why is glucogenesis the least efficient way to get energy
Altogether, producing a single molecule of
glucose by gluconeogenesis consumes four molecules of ATP and two
molecules of GTP.
What are some special reservoirs cells use to store food molecules
Glycogen -This large polysaccharide is stored as small granules in the
cytoplasm of many animal cells, but mainly in liver and muscle cells . Glycogen is a branched polymer of glucose
Fats are generally stored as droplets of water-insoluble triacylglycerols
inside cells
Most animal species
possess specialized fat-storing cells called adipocytes.
Plants convert some of the sugars they make through photo
synthesis during daylight into fats and into starch, a branched polymer
of glucose very similar to animal glycogen.
What are 2 ways plants store food
The embryo inside a plant seed must live on stored food reserves for a
long time, until the seed germinates to produce a plant with leaves that
can harvest the energy in sunlight. The embryo uses these food stores as
sources of energy and of small molecules to build cell walls and to syn
thesize many other biological molecules as it develops
In plant cells, fats and starch are both stored in chloroplasts—specialized
organelles that carry out photosynthesis These energy
rich molecules serve as food reservoirs that are mobilized by the cell
to produce ATP in mitochondria during periods of darkness.
How do plant cells and animal cells store food
Glucose is stored in animal cells as glycogen, whereas plant cells
store glucose as starch; both animal and plant cells store fatty acids
as fats (triacylglycerols). The food reserves stored by plants are major
sources of food for animals, including humans.
Where does oxidative phosphorylation take place ?
oxidative phosphorylation on the inner
mitochondrial membrane.
What happens after pyruvate converted into Acetyl COA
In the presence of oxygen, eukaryotic cells convert pyruvate into acetyl CoA plus CO2 in the mitochondrial matrix. The citric acid cycle
then converts the acetyl group in acetyl CoA to CO2 and H2O, cap
turing much of the energy released as high-energy electrons in the
activated carriers NADH and FADH2.
Where do NADH and FADH2 pass their high energy electrons to ?
In the mitochondrial matrix, NADH and FADH2 pass their high-energy
electrons to an electron-transport chain in the inner mitochondrial
membrane, where a series of electron transfers is used to drive the
formation of ATP. Most of the energy captured during the breakdown
of food molecules is harvested during this process of oxidative phosphorylation
where does the process of glycosis happen
In the cytosol
How does fermentation keep going
It provides NAD+
What is needed to start glycolysis
Glucose and 2ATPS
Glycolysis results in what products
Pyruvate ATP and NADPH
What is the net gain of ATP in glycolysis
2 ATP
In a eukaryotic cell where does the citric acid cycle take place?
Matrix of the mitochondria
How many molecules of carbon dioxide are generated one round of citric acid cycle
2 carbon dioxide
Two molecules of CO2 are produced after one round after citric acid cycle. Where does the required oxygen come from
water
T or F. One mole of oxaloacetate is required for every acetyl COA that is metabolized via the CAC
FALSE BECAUSE ONLY ONE MOLE OF OXALOACETATE IS REQUIRED FOR ONE acetyl COA
What is the essential energy carrying particle that is actually used to produce ATP
high energy electrons
The FINAL METABOLITE PRODUCED BY GLYCOSIS
PYRUVATE
FATTY ACIDS CAN BE BROKEN DOWN TO FORM MORE ENERGY THAN GLUCOSE . WHAT ARE FATTY ACIDS BROKEN DOWN INTO
ACETYL COA
WHAT IS PRODUCED IN THE CITRIC ACID CYCLE
GTP
FADH2
NADH
WHICH OF THE FOLLOWING STPES OR PROCESSES IN AEROBIC RESPIRATION INCLUDE THE PRODUCTION OF CARBON DIOXIDE
KREB CYCLE
IS KREB CYCLE THE ONLY WAY TO BREAKDOWN CO2
NOPE THE, also conversion of pyruvate to acetyl COA
The advantage of the gradual oxidation of glucose compared to the combustion of CO2 and H20 in a single step
energy can be extracted in usable amounts
Starch is a polymer of glucose in plant cels is similar to what in animal cells
glycogen
T or F Fats store twice amount of energy as glycogen and take up twice amount of space
False
In ferementation reaction in skeletal muscle cells pyruvate is broken down into
lactae and NAD+
The main goal of glycosis is to produce energy by breaking down glucise but it produces many other molecules to T or F
True
Wherew do the following carbon atoms from pyruvic acid end up in the Kreb cycle
The carbon atoms become partt of the carbon dioxide molecule and end up in the atmosphere as a waste product
Yeast fermentation is what kind of process
aneorobic process that converts pyruvate into ethanol
Muscle cells convert pyruvate into what
lactate
Immediatly after pyruvate is formed through glycolysis it enters the mitochondria
What products do it form after undergoing s rection
Acetyl COA and Nadh
and pyruvate dehydrogenase is responsible for taking pyruvate and converting it into acetly COa
Why does glycoysis only occur in the cytosol
Because in mitochondrua it does not have the enzyme to perform glycosis
Why does glycolysis occur under aneorbic conditions
Becuase of limited oxygen availibity and energy production
Rapid energy products
Why can nearly all exisiting organisms perfrom glycolysis
Glucose is a universal energy source
Glycolsis is essential for life
evolutionary conservation
where does oxidative phosphorylation takes place ?
. In eukaryotic cells,
oxidative phosphorylation takes place in mitochondria, and it depends
on an electron-transport process that drives the transport of protons (H+)
across the inner mitochondrial membrane.
What is the membrane-based process for making ATP ( there are two stages )
one sets up an electrochemical proton gradient, and the other
uses that gradient to generate ATP
describe the two stages of the electron tansport chain
In stage 1, high-energy electrons—derived from the oxidation of
food molecules or from sunlight or other chemical sources are transferred along a series of electron carriers, called an electron-transport chain, embedded
in a membrane. These electron transfers release energy that is used
to pump protons, derived from the water that is ubiquitous in cells,
across the membrane and thus generate an electrochemical proton
gradient
In stage 2, protons flow back down their electrochemical gradient
through a membrane-embedded protein complex called ATP synthase,
which catalyzes the energy-requiring synthesis of ATP from ADP and
inorganic phosphate
describe chemiosmotic coupling
Chemiosmotic coupling is the idea that the proton concentration gradient across the inner mitochondrial membrane, which is generated by the electron transport chain, is ultimately what drives ATP production via ATP synthase.
Describe the location and its dynamic structure
Mitochondria in some cell types, mitochondria remain fixed in one location, where they supply ATP directly to a site of unusually high
energy consumption
An individual mitochondrion is bounded by two highly specialized
membranes—one inside the other. These membranes, called the
inner and outer mitochondrial membranes, create two mitochondrial compartments
a large internal space called the matrix where the conversion of fatty acids into acetyl COA
a much narrower intermembrane space
The outer membrane contains many molecules of a transport protein
called porin, which forms wide, aqueous channels through the lipid bilayer
Cristae These folds greatly increase the surface area of the membrane. In
a liver cell, the inner membranes of all the mitochondria
Where is the site of oxidative phosphorylation
The inner mitochondrial membrane is the site of oxidative phosphoryla
tion, and it is here that the proteins of the electron-transport chain and
the ATP synthase required for ATP production are concentrated.
how does the citric acid cycle generate high energy electron needed for ATP production ?
The generation of ATP is powered by the flow of electrons that are
derived from the burning of carbohydrates, fats, and other foodstuffs during glycolysis and the citric acid cycle
The citric acid cycle gets the fuel it needs to produce these activated car
riers from food-derived molecules that make their way into mitochondria
from the cytosol.
Both the pyruvate produced by glycolysis and the fatty
acids derived from the breakdown of fats can enter
the mitochondrial intermembrane space through the porins in the outer
mitochondrial membrane.
These fuel molecules are then transported
across the inner mitochondrial membrane into the matrix, where they
are converted into the crucial metabolic intermediate, acetyl CoA
The acetyl groups in acetyl CoA are then oxidized to CO2 via the citric acid cycle
Some of the energy derived from this
oxidation is saved in the form of high-energy electrons, held by the activated carriers NADH and FADH2
These two activated carriers can then
donate their electrons to the electron-transport chain in the inner mito
chondrial membrane
Describe the movement of electrons across the electrochemical gradient
The chemiosmotic generation of energy begins when the activated carriers NADH and FADH2 donate their electrons to the electron-transport
chain in the inner mitochondrial membrane, becoming oxidized to NAD+
and FAD, respectively, in the process
. The electrons are
quickly passed along the chain to molecular oxygen (O2) to form water
(H2O).
The stepwise movement of these electrons through the components of the electron-transport chain releases energy that can then be
used to pump protons across the inner mitochondrial membrane
The resulting proton gradient, in turn, is used to drive the synthesis of ATP.
What is the mechanism for ATP synthesis
oxidative phosphorylation
because it involves both the consumption of O2 and the addition of a
phosphate group to ADP to form ATP.
Where does the high energy electrons come from in photosynthesis?
In photosynthesis, the high-energy electrons
come from the organic green pigment chlorophyll, which captures the energy from sunlight
What are the three respiratory enzyme complexes, in the order in which they
receive electrons ?
(1) NADH dehydrogenase complex,
(2) cytochrome c
reductase complex, and
(3) cytochrome c oxidase complex
Each complex contains metal ions and other chemical groups that act
as stepping stones to enable the passage of electrons through the complex.
The movement of electrons through these respiratory complexes is
accompanied by the pumping of protons from the mitochondrial matrix
to the intermembrane space.
Describe the movement of electrons from one complex to the next and the flow of electrons
The first respiratory complex in the chain, NADH dehydrogenase, accepts
electrons from NADH.
These electrons are extracted from NADH in the form of a hydride ion (H–), which is then converted into a proton and two
high-energy electrons
That reaction, H– → H+ + 2e–,
is catalyzed by the NADH dehydrogenase complex itself.
After passing
through this complex, the electrons move along the chain to each of the
other enzyme complexes in turn, using mobile electron carriers to ferry
them between the complexes
.This transfer of electrons is energetically favorable: the electrons are passed from electron
carriers with a weaker electron affinity to those with a stronger electron
affinity, until they combine with a molecule of O2 to form water.
The final
electron transfer is the only oxygen-requiring step in cell respiration,
How does proton pumping produce a steep electrochemical proton gradient across the internal mitochonrial membrane
First, the
pumping of protons generates an H+ gradient—or pH gradient—across
the inner membrane. As a result, the pH in the matrix (around 7.9) is
about 0.7 unit higher than it is in the intermembrane space (which is 7.2,
the same pH as the cytosol).
Second, proton pumping generates a voltage gradient—or membrane potential—across the inner membrane; as
H+ flows outward, the matrix side of the membrane becomes negative
and the side facing the intermembrane space becomes positive
he force that drives the passive flow of an ion
across a membrane is proportional to the ion’s electrochemical gradient.
The strength of that electrochemical gradient depends both on the volt
age across the membrane, as measured by the membrane potential, and
on the ion’s concentration gradient
Because protons
are positively charged, they will more readily cross a membrane if there
is an excess of negative charge on the other side.
In the case of the inner
mitochondrial membrane, the pH gradient and membrane potential work together to create a steep electrochemical proton gradient that makes it
energetically very favorable for H+ to flow back into the mitochondrial
matrix.
The membrane potential contributes significantly to this proton motive force, which pulls H+ back across the membrane; the greater the
membrane potential, the more energy is stored in the proton gradient
Describe how ATP Synthase Uses the Energy Stored in the
Electrochemical Proton Gradient to Produce ATP
the electrochemi
cal proton gradient across the inner mitochondrial membrane is used to
drive the synthesis of ATP from ADP and Pi
The device
that makes this possible is ATP synthase, a large, multisubunit protein
embedded in the inner mitochondrial membrane.
ATP synthase can also operate in reverse—using the energy of ATP
hydrolysis to pump protons “uphill,” against their electrochemical gra
dient
In this mode, ATP synthase functions like the H+
pumps .
Whether ATP synthase primarily makes ATP
or consumes it to pump protons—depends on the magnitude of
the electrochemical proton gradient across the membrane
What is essential energy carrying particle that is actually harvested from these molecules to produce ATP
high energy electrons
ATP synthase is energized into to create ATP by what direct energy source
The proton gradient
Where does the electron chain pump protons
It pumps protons out of the mitochinrial matirx
Describe the review of the players in process all the way to oxygen as the terminal electron acceptor
Electrons are carried along the membrane through a series of protein carriers
Protons are translocated across the membrane from the matrix to intermembrane space
As NADH/FADH2 delivers more H+ and electrons into the ETS the proton gradient increases with H+ building up outside the inner mitochondrial membrane and OH- inside the membrane
Oxygen is the terminal electron acceptor combining with electrons and H+ ions to produce water
what are some similarities and differences regarding chloroplast and the mitochondria
Chloroplast has 3 compartments
Chloroplast is the larger organelle
Both are its own genome
Miochonria is its own inner membrane house ETC
Both have highly permeable outer mebranes
What does mitochondria use as fuel
pyruvate and fatty acids directly as fuel
What is produced in the citric acid cycle and donates electrons into the transport chain
NADH AND FADH2
What does the citric acid cycle oxidize and produce as a waste product
Oxidizes pyrivate and CO2 as a waste product
What is the final electon acceptor
Oxygen
What IS THE SYNTHESIS OF ATP ALSO KNOWN AS
oxidative phosphorylation
What type of reractions occur in the electron transfer chain
Redox reactions
What is the first mobile electron carrier in the respiratory chain
Ubiquinone
What is the small protein that acts as a mobile electron carrier in the electron transport chain
Cytochrome C
What transfers electrons to oxygen
Cytochrome oxidase
What is cytochrome C primary role in the electron transport chain?
Cytochrome C accepts the electrons from complex 3 / cytochrome oxidase and directly transfers these electrons to molecular oxygen
T or F only high energy electrons can be used to drive electrons in the ETC
False also FADH2
What substances are used as energy stores within your body
Fats inside the liver
Glycogen in liver
Glucise in glycogen
and glycogen is used in the absence of ingesting externa. sources and lasts for a period of months
What is true about the final acceptor in the electron transport chain?
It picks up electrons and protons
Where is the electron transport chain
The inner membrane of the mitochondria
In cellular respiration the products of the electron transport chain are
water and ATP
what is the fianl electron acceptoof the ellcetron transport chain
oxygen
Which one of the following best describes the electron transport chain
electrons are passed down the chain releasing enrgy
What dies does photosytem 2 and 1 generate
Photosysstem 1 geberates ATP
Photosystem 2 generates NADPH
Atp synthase is an example of which membrane protein
enzyme
The movemnt of protns throughtATP synthesus occurs drive ATP formation what is the direction of the proton movement
intermembrane space to the matrix
in carbon fixation process in chloroplats carbin dioxude us intially added to what sugar
ribulose 1,5 biphosphate
chloroplasts are to photsynrthesis as
mitochondria to cellular respiration
What is the photosynthesis equation
6H20+6o2———–> C6H12O6+6O2
where are the photosystems located
thylakoids
Explain the final producrts in cellular repsiration, glycolyis, citric acid, and the electron transport chain
Cellular respiration
Acetyl COA
2 pyruvate turns into 2 acetyl COA and 2 NADH
GLycolysis
1 glucose is split into 2 pyruvate + 2NADH + 2ATP
Citric Acid
2 acetyl COA —– 6 NADH + 2FADH2 + 2 GTP
Electron transport chain
Convert carrier molecules to ATP
what is the role of ubiquinone
. In the mitochondrial
respiratory chain, for example, a small, hydrophobic molecule called
ubiquinone picks up electrons from the NADH dehydrogenase complex
and delivers them to the cytochrome c reductase complex
What is the purpose of iron sulfur center
Iron–sulfur centers have relatively low affinities for electrons and thus are prominent in the electron
carriers that operate in the early part of the chain. An iron–sulfur center in the NADH dehydrogenase complex, for example, passes electrons to
ubiquinone. Later in the pathway, iron atoms that are held in the heme
groups bound to cytochrome proteins are commonly used as electron
carriers
Cytochrome c purpose
cytochrome c, a small protein that accepts electrons from the
cytochrome c reductase complex and transfers them to the cytochrome c
oxidase complex, has a redox potential
What is the purpose of cytichrome c oxidase
Cytochrome c oxidase, the final electron carrier in the respiratory chain,
has the highest redox potential of all. This protein complex removes
electrons from cytochrome c, thereby oxidizing it—hence the name
“cytochrome c oxidase
Hiw does the cytochrome c Oxidase Catalyzes the Reduction of
Molecular Oxygen
In total, four electrons donated by cytochrome c and four protons
extracted from the aqueous environment are added to each O2 molecule in the reaction 4e– + 4H+ + O2 → 2H2O. In addition to the protons
that combine with O2, four other protons are pumped across the mem
brane during the transfer of the four electrons from cytochrome c to O2.
This pumping occurs because the transfer of electrons drives allosteric
changes in the conformation of cytochrome c oxidase that cause protons
to be ejected from the mitochondrial matrix
Oxygen is useful as an electron sink because of its very high affinity for
electrons. However, once O2 picks up one electron, it forms the superox
ide radical O2–;
describe photosynthesis
photosynthesis—the series of light-driven reactions that creates organic
molecules from atmospheric carbon dioxide (CO2).
In the process,
water molecules are split, releasing vast quantities of O2 gas into the
atmosphere. This oxygen in turn supports oxidative phosphorylation
Where does phtosynthesis takes place ?
There, specialized intracellular organelles called chloroplasts capture light energy
and use it to produce ATP and NADPH.
These activated carriers are used
to convert CO2 into organic molecules that serve as the precursors for
sugars—a process called carbon fixation.
What are the characteristics of chloroplasts
Chloroplasts are larger than mitochondria, but both are organized along
structurally similar principles.
Chloroplasts have a highly permeable
outer membrane and a much less permeable inner membrane, in which
various membrane transport proteins are embedded
What are the 3 compartments of chloroplasts
The inner membrane surrounds a large space called
the stroma, which contains many metabolic enzymes and is analogous
to the mitochondrial matrix
The inner membrane of the
chloroplast does not contain the molecular machinery needed to pro
duce energy.
‘
Instead, the light-capturing systems, electron-transport
chain, and ATP synthase that convert light energy into ATP during photosynthesis are all contained in the thylakoid membrane.
This third
membrane is folded to form a set of flattened, disclike sacs, called the
thylakoids, which are arranged in stacks called grana
What is stage 1 of photosynthesis
Stage 1 In this stage,
an electron-transport chain in the thylakoid membrane harnesses
the energy of electron transport to pump protons into the thylakoid
space; the resulting proton gradient then drives the synthesis of ATP
by ATP synthase. What makes photosynthesis very different is that
the high-energy electrons donated to the photosynthetic electron
transport chain come from a molecule of chlorophyll that has
absorbed energy from sunlight. Thus the energy-producing reactions
of stage 1 are sometimes called the light reactions.
what happens in stage 2 of photosynthesis
. In stage 2 of photosynthesis, the ATP and the NADPH produced by
the photosynthetic electron-transfer reactions of stage 1 are used to
drive the manufacture of sugars from CO2 (see Figure 14–30). These
carbon-fixation reactions, which do not directly require sunlight, begin
in the chloroplast stroma. There they generate a three-carbon sugar
called glyceraldehyde 3-phosphate. This simple sugar is exported to
the cytosol, where it is used to produce a large number of organic
molecules in the leaves of the plant
how do both stages of photosynthesis depend on the chloroplast
n stage 1, a series
of photosynthetic electron
transfer reactions produce ATP
and NADPH; in the process,
electrons are extracted from
water and oxygen is released
as a by-product, as we discuss
shortly. In stage 2, carbon dioxide
is assimilated (fixed) to produce
sugars and a variety of other
organic molecules. Stage 1 occurs
in the thylakoid membrane,
whereas stage 2 begins in the
chloroplast stroma (as shown) and
continues in the cytosol
describe the 2 things the photosystem consists of
lecules are held in large multi
protein complexes called photosystems. Each photosystem consists of
a set of antenna complexes, which capture light energy, and a reaction
center, which converts that light energy into chemical energy.
In an antenna complex, hundreds of chlorophyll molecules are arranged
so that the light energy captured by one chlorophyll molecule can be
transferred to a neighboring chlorophyll molecule in the network
The chlorophyll special pair is not located in an antenna complex. Instead,
it is part of the reaction center—a transmembrane complex of proteins
and pigments that is thought to have first evolved more than 3 billion
years ago in primitive photosynthetic bacteria
Within the
reaction center, the special pair is positioned directly next to a set of
electron carriers that are poised to accept a high-energy electron from
the excited chlorophyll special pair
This electron transfer
converts the light energy that entered the special pair into the chemical
energy of a transferable electron—a transformation that lies at the heart
of photosynthesis.
how do the photsytems cooperste generate ATP and NADPH
When the first photosystem absorbs light energy, its reaction center passes
electrons to a mobile electron carrier called plastoquinone
This carrier transfers the high-energy electrons to a proton pump,
The electrochemical proton
gradient then drives the production of ATP by an ATP synthase located in
the thylakoid membrane
At the same time, a second, nearby photosystem—called photosystem
Icapturing the energy from sunlight.
The reaction
center of this photosystem passes its high-energy electrons to a different
mobile electron carrier, called ferredoxin, which brings them to an enzyme
that uses the electrons to reduce NADP+ to NADPH
How is Oxygen Generated by a Water-Splitting Complex
Associated with Photosystem II
photosystem II, the missing electron is replaced by a special manganese-containing protein complex that removes the electrons from water.
The cluster of manganese atoms in this water-splitting enzyme holds
onto two water molecules from which electrons are extracted one at a
time.
Once four electrons have been removed from these two water molecules and used to replace the electrons lost by four excited chlorophyll
special pairs—O2 is released
where do the light reactions generate ATP and NADPH in
The light reactions of photosynthesis generate ATP and NADPH in the
chloroplast stroma, as we have just seen
how are sugars Generated by Carbon Fixation Can Be Stored
as Starch or Consumed to Produce ATP
The glyceraldehyde 3-phosphate generated by carbon fixationt.
During periods of excess photosynthetic activity, much of the
sugar is retained in the chloroplast stroma and converted to starch. Like
glycogen in animal cells, starch is a large polymer of glucose that serves
as a carbohydrate reserve, and it is stored as large granules in the chloro
plast stroma.
. Other glyceraldehyde 3-phosphate molecules are converted to
fat in the stroma.
At night, this stored starch and fat can be broken down to sugars and
fatty acids, which are exported to the cytosol to help support the meta
bolic needs of the plant. Some of the exported sugar enters the glycolytic
pathway where it is converted to pyruvate.
Most of that
pyruvate, along with the fatty acids, enters the plant cell mitochondria
and is fed into the citric acid cycle, ultimately leading to the production
of ATP by oxidative phosphorylation
explain carbon fixation
. This production of sugar from CO2 and
water, which occurs during stage 2 of photosynthesis, is called carbon
fixation.
In the central reaction of photosynthetic carbon fixation, CO2 from
the atmosphere is attached to a five-carbon sugar derivative, ribulose
1,5-bisphosphate, to yield two molecules of the three-carbon compound
3-phosphoglycerate. This carbon-fixing reaction, which was discovered in
1948, is catalyzed in the chloroplast stroma by a large enzyme called ribu
lose bisphosphate carboxylase or Rubisco
deescribe the elaborate cycle of the calvin cycle
The elaborate series of reactions in which CO2 combines with ribulose
1,5-bisphosphate to produce a simple three-carbon sugar—a portion of
which is used to regenerate the ribulose 1,5-bisphosphate that’s consumed—forms a cycle, called the carbon-fixation cycle, or the Calvin cycle
.
For every three molecules of CO2 that enter the cycle, one
molecule of glyceraldehyde 3-phosphate is ultimately produced, at the expense of nine molecules of ATP and six molecules of NADPH, which are
consumed in the process. Glyceraldehyde 3 phospohate ism the final product of the cycle
whayt are the products of the citric acud cycle
Synthesis of glyceraldehyde 3 phosphate
Regeneration of ribulose biphosphate
Consumed for each CO2
3 ATP
2 NADPH
Net cost
