Quiz 2 Flashcards
metabolic pathways
coordinated series of reactions that convert molecules into different one
Five principles of metabolic pathways
1) Complex transformations occur in a series of separate reactions. 2) Each reaction catalyzed by enzyme. 3) Many metabolic pathways are conserved across countless organisms. 4) In eukaryotes, metabolic pathways are compartmentalized in specific organelles (why they are larger). 5) Key enzymes in each pathway can be regulated (metabolism occurs within cells). Each pathway can be inhibited or activated.
Anabolic
Simple molecules built up into more complex ones (endergonic)
Catabolic
Complex molecules built down into smaller molecules (exergonic). Energy harnessed back into ATP.
ATP structure
sugar (ribose), base (Adenine), phosphate. Nucleotide holds energy.
Phosphate Groups
Phosphate groups have negative charges so when brought together they repel each other (they need lots of energy to break). When broken they will release a lot of energy. 3 Phosphate groups
ADP
when theres only two phosphate groups (one broke down)
AMP
When there is only one phosphate group (
Hydrolysis
addition of water. ATP+H20–> ADP +Pi (the Pi is the phosphate group that had their bond broken). Exergonic reaction because energy is being released from broken bond of phosphate group.
What is ATP+H20–> ADP +Pi catalyzed by?
ATPase
Exergonic reactions
Releases energy which can be harnessed to make ATP.
Endergonic reactions
requires energy from ATP
Coupling
Coupling exergonic reactions with endergonic. Energy from exergonic reaction drives endergonic reaction.
Is the same phosphate broken down in exergonic reactions being used in endergonic reactions?
No, there are a bunch of different phosphates floating around so there will be different phosphates being used
reduction
gain of one or more electrons (RIG)
oxidation
loss of electrons (OIL)
redox reactions
one substance transfers electrons to another substance be able to label oxidation and reduction compounds. Reduced electron carriers capture and transfer energy.
How do you keep track of electrons moving?
Whenever an electron is being moved it will go along with a Hydrogen ion. Transfer of hydrogens=transfer of electrons
Coenzyme NAD+
electron carrier in redox reactions. They carry energy in cells which means that they have high energy. This is reversible.
cellular respiration
metabolic pathway to release energy from carbon bonds with the END GOAL of generating ATP. That ATP will be used to drive the rest of reactions within cells
Mitochondrial structure
2 membranes (outer membrane and inner membrane). Squiggles are foldings of inner membrane.
glycolysis
breaks up one glucose to two pyruvate. 10 separate reactions which takes place in the cytosol. for one glucose, 2 molecules of pyruvate are produced. Produces 4 ATP and 2 NADH (2 net ATP). Takes place in cytoplasm
Glycolysis Steps 1-5
Energy investing reactions (put energy in). Put a phosphate group on glucose with 6 carbon and break it into 2 Pyruvate molecules (3 carbon each)
Glycolysis Steps 6-10
yield NADH and ATP (energy harvesting). Pulling energy out (NAD+ to NADH) from each molecule. Receive an ATP from each as well. Then form to 3 carbon molecules
Step 6 Glycolysis
Redox reaction. reducing NAD+ to NADH. Reduction was getting the NAD+ hydrogen and moving it to NADH. Phosphate group is added.
Step 7 Glycolysis
substrate level phosphorylation. A phosphate is taken from ADP (2 phosphates) and moved to ATP (3 phosphates)
Pyruvate oxidation
Takes the pyruvate from cytoplasm to the mitochondrial matrix. Produces acetate and CO2. Coenzyme A forms Acetyl CoA. Exergonic reaction. Pyruvate loses electrons (2 times for each pyruvate)
Citric Acid Cycle
8 reactions in the mitochondrial matrix. Starts with Acetyl CoA (2). Oxaloacetate is regenerated each cycle (carbon is attached throughout until fully regenerated). Acetyl group is completely oxidized to two molecules of CO2. Energy released is captured by NAD+, FAD+, and GDP. Operates twice for every glucose molecule that enters glycolysis (2 times bc 2 Acetyl CoA).
First steps of citric acid cycle
Two carbon attach to oxaloacetate (4c) then this becomes a 6 carbon molecule. 2 carbons from CoA. NAD+ to NADH
outputs of citric acid cycle and pyruvate oxidation
6CO2, 8 NADH, 2 FADH, 2 GDP (this is from two rounds of citric acid cycle)
Where does the CO2 go after oxidation?
Discarded as waste product
How does GTP defer from ATP?
Almost exactly the same as ATP but has a guanine base
goal of cellular respiration
main goal is capturing energy from breaking carbon-carbon bonds
Oxidative Phosphorylation
ATP is synthesized by oxidation of electron carriers in the presence of O2.
Stage 1 of Oxidative Phosphorylation
series of redox reactions which release a small amount of energy at each step. Proton Gradient is generated (H+) which is a form of potential energy.
respiratory chain
big chain of proteins apart of electron transport chain. NADH and FADH2 give up electrons (becoming oxidized). Oxidation reactions are exergonic. Protons are being moved against concentration gradient using energy from the protein chain (potential energy stored in proton gradient). Oxygen is the final electron acceptor (reduced).
Oxidative Phosphorylation: Chemiosmosis
Protons flow back across the membrane through a channel protein, ATP synthase, which couples the diffusion with ATP synthesis. Hydrogen ions cannot flow back through membrane because of their charge so they go through ATP synthase
ATP synthase
bringing together ADP and a phosphate (Pi) to create ATP
proton motive force
potential energy. protons constantly undergoing cellular respiration
How is pyruvate oxidation and the citric acid cycle regulated?
regulated by concentrations of starting materials (acetyl CoA and oxidized electron carriers)
what are the oxidized form of NADH and FADH2?
NAD+ and FAD
what happens when there is no oxygen present in glycolysis ?
Fermentation
cellular respiration can best be described as ?
Converting the energy in glucose to energy available from the hydrolysis of ATP.
35 Molecules of ATP are generated per molecule of glucose oxidized in cellular respiration. The main function of oxygen in respiration is to…
Accept electrons released by glucose oxidation, forming H2O.
Fermentation
no oxygen is present. Occurs in the cytosol. Main goal is to regenerate the NAD+ and keep glycolysis going (have endless supply of NADH). Two main types: Alcoholic and Lactic Acid Fermentation. DOES NOT GIVE US ATP
Alcoholic Fermentation
Two enzymes to metabolize pyruvate to ethanol. 2 CO2 released. NADH is turned into NAD+.
Lactic Acid Fermentation
Pyruvate is the electron
acceptor and lactate is
the product. Occurs in
microorganisms and
some muscle cells. 2 Lactate (makes bloodstream more acidic). Lactate can be converted back into glucose from the liver.
How are Metabolic Pathways Regulated and Interrelated ?
Metabolic pathways do not operate in isolation (can share intermediate molecules). Pathways are regulated by enzyme inhibitors/activators.
Why do we inhibit enzyme action? Negative Feedback/Regulation
If we make too much of something we need to regulate it by stopping production. Can inhibit by binding to a molecule to stop it from converting to another molecule.
Positive Feedback/Regulation
Excess product of one pathway can activate an enzyme in another pathway, diverting raw materials away from synthesis of the first product.
Control Point in cellular respiration (step 3)
phosphofructokinase. inhibited by ATP and citrate (from TCA). ATP can be a signal which inhibits phosphofructokinase. Citrate can also inhibit phosphofructokinase which slows down cellular respiration
How does ADP act as an activator?
ADP can kickstart glycolysis/notify phosphofructokinase to speed up citric acid cycle
Citrate Synthase (Step 1)
inhibited by NADH and ATP
isocitrate dehydrogenase (Step 3)
inhibited by NADH and ATP
* Activated by ADP (not enough ATP)
Can ATP be synthesized by other macromolecules?
Yes, ATP can be synthesized using the chemical bond
energy in all macromolecules
Polysaccharide and glycolysis
Polysaccharides can be broken down through catabolic pathways into monosaccharides (hydrolyzed). Glucose then enters Glycolysis
lipids and glycolysis
Lipids are broken down to
glycerol → DHAP → glycolysis
fatty acids → acetyl CoA → citric acid cycle.
Proteins and glycolysis
Proteins are hydrolyzed to
amino acids, which feed
into glycolysis or the citric
acid cycle. Proteins are very diverse and can feed into both glycolysis and citric acid cycle
nucleic acid conversions
can be converted into amino acids which then go into citric acid cycle. Nucleic acids are a small percentage of molecules
consumed in food, so seldom
used as energy source
Anabolic Pathways (Reversal of catabolic pathways)
Can start taking components out of cellular respiration and turn those into amino acids and built back up into proteins. Energy input is ATP/NADH. Building back up molecules while catabolic breaks things down to put into cellular respiration.
How is a balance maintained between cells?
Organisms regulate enzymes to maintain balance between catabolism and anabolism. Balance of biochemical molecules is relatively constant
Which is an accurate representation of the
flow of energy?
Catabolic reactions–>
reduced electron carriers–>
ATP–>anabolic reactions
photon
“packet” of energy. When a photon hits a molecule it can: Bounce off: scattered or reflected
* Pass through: transmitted
* Be absorbed, adding energy to the molecule (excited
state)
* Certain molecules absorb photons of specific
wavelengths
cholorphyll
pigment that absorbs wavelengths of specific lengths. Chlorophyll A: absorbs blue and red wavelengths
thylakoid
sacs within the chloroplast that capture light energy for photosynthesis
Photosynthesis Pathway: Light Reactions
Takes place in thylakoid. light reactions, take light energy and convert to chemical energy. Using the energy for second part of photosynthesis. ATP and NADPH energy used + CO2 to produce carbohydrates. Electrons and hydrogens are removed from water and oxygen is left
Goal of Photosynthesis
make glucose from light energy and convert to ATP and NADPH
What does light energy do to electrons?
light energy excites electron (photosystem II)
Electron Transport Chain Photosynthesis
Electrons passed through chain and then go through different photosystems. Proton gradient is created. NADPH
moving down concentration gradient
high concentration to low and ATP is made from that.
photophosphorylation
Proton gradient used to make ATP
Outputs of Photosynthesis
ATP, NADPH, and O2
How Is Chemical Energy Used to
Synthesize Carbohydrates?
occurs in stroma. Referred to as the Calvin Cycle. The pathway of CO2 fixation is cyclic (enzyme rubisco)
Calvin Cycle Step 1
Carbon fixation (carbon brought in from atmosphere). Carbon is attached to helper molecule RuBp (used over and over again). Breaks up into 2 molecules and forms 3Pg all done by Rubisco.
Calvin Cycle Step 2
3Pg is reduced and forms G3P (energy is used from ATP and NADPH). G3P is used to make sugars
Calvin Cycle Step 3
Regenerate RuBP using extra carbons
G3P used to make carbs
- Depending on time of day and needs of plant:
1. Some G3P exported out of
chloroplast into cytoplasm
and converted to hexoses
(then used in glycolysis)
2. Some G3P used to synthesize
glucose inside the chloroplast
(used or stored as starch)
