Midterm 2 Study Guide Flashcards
How is chemical energy “stored?”
- Potential energy; energy stored as chemical bonds, concentration gradient, charge imbalance
- What is the first law of thermodynamics?
- Energy cannot be created or destroyed
- What is the second law of thermodynamics?
- All energy transfers or transformations make the universe more disordered (increasing entropy)
- What is free energy and how is it abbreviated?
- The portion of a system’s energy that is able to perform work when T is uniform throughout system; abbreviated as G
- If the difference in free energy is a negative number, what does that imply about the reaction in question?
- ∆G = negative, spontaneous reaction
What if the change in free energy for a reaction is a positive number?
G = positive, nonspontaneous reaction
- What is a spontaneous vs. a non-spontaneous reaction?
- Spontaneous: can occur without outside help; increases the stability of a system
- Nonspontaneous: can only occur in energy is added; decreases the stability of a system
- What do endergonic and exergonic mean?
- Exergonic: ∆G is negative, spontaneous, stability of system increases, net release of free energy, catabolism
- Endergonic: requires energy from its environment, ∆G is positive, not spontaneous, stability of system decreases, anabolism
- What are the parts of the structure of a molecule of ATP?
- 5 carbon sugar (ribose), nitrogenous base (adenine), 3 phosphate groups
- What happens when ATP is hydrolyzed to ADP?
- Exergonic (energy is released) ∆G = -7.3 kcal/mol
- What are the main kinds of work that ATP can do in the cell?
- Source of energy for cellular work; can hold and transfer free energy; releases a large amount of energy when hydrolyzed; can become phosphorylated, or donate phosphate groups to other molecules
- What do enzymes do?
- Speed up the rate of reaction; lower the energy barrier by bringing the reactants together
- What are some factors that affect enzymatic activity?
- Presence of inhibitors/types of inhibition
- Allosteric regulation:
- Reversible phosphorylation:
- pH:
- Temperature:
What is irreversible inhibition?
irreversible inhibition: inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme
What is reversible inhibition?
reversible inhibition: inhibitor bonds non-covalently to the active site and prevents substrate from binding
What is competitive inhibition?
competitive inhibition: inhibitors compete with the natural substrate for binding sites
What is uncompetitive inhibition?
uncompetitive inhibitors: bind to enzyme-substrate complex, preventing release of products
What is noncompetitive inhibition?
noncompetitive inhibitors: bind to enzyme at a different site (not the active site): keeps enzyme open or changes conformation so active site is closed
What is allosteric regulation?
an effector binds enzyme at a site different from the active site, which changes its shape (active form can bind substrate, inactive form cannot bind substrate but can bind an inhibitor
What is reversible phosphorylation?
enzymes can be activated when protein kinase adds a phosphate group and deactivated by protein phosphatase
- How can you tell if a molecule has been reduced? Oxidized?
Reduced = more hydrogens have been added
Oxidized = more bonds to oxygen
- What is NADH (and NAD+)?
Electron carrier used to in oxidative phosphorylation to generate ATP
NAD+=oxidized from
An electron carrier in redox reactions; oxygen accepts e- from NADH
- What kind of enzyme removes hydrogens from NADH?
Dehydrogenase
- How does an electron transport chain work?
Leverages a series of redox reactions and transport of electrons which generate a concentration of protons to drive chemiosmosis via a proton motive force
- What are the three major processes involved in fully oxidizing glucose?
1)Glycolysis: glucose is converted to pyruvate (can occur under both anaerobic or aerobic conditions) - cytosol
2)Cellular respiration: pyruvate is converted to 3 molecules of CO2: aerobic - mitochondria
3)Fermentation: converts pyruvate into lactic acid or ethyl alcohol (anaerobic) - cytosol
- What are all the products from the process of glycolysis?
2 ATP, 2 NADH + 2H+, 2 Pyruvate
- Pyruvate has three fates after glycolysis. What are they?
- Citric Acid cycle (under aerobic conditions)
- Alcohol Fermentation (anaerobic conditions)
- Lactic Acid Fermentation (anaerobic conditions)
- What enzyme decarboxylates pyruvate before the Krebs cycle can begin?
- Pyruvate dehydrogenase COMPLEX
- Which molecule donates carbon to the Kreb’s cycle?
- Acetyl CoA
- Which molecule is the carbon acceptor of the Kreb’s cycle?
- Oxaloacetate
- Which molecule is the product formed immediately after the 2-carbon fragment from Acetyl Co-A is donated to Kreb’s cycle?
- Citrate
- Oxidative phosphorylation is actually composed of two processes. What are they?
- Electron transport
- Chemiosmosis
- Where does oxidative phosphorylation take place in the cell?
the inner membrane of the mitochondrion
- What does chemiosmosis involve?
- Diffusion of protons via a proton motive force back across the membrane which drives the spinning of ATP synthase to produce ATP
- What does ATP synthase look like? What are the parts?
F0= “lollipop” facing the intermembrane space
F1=faces matrix and poops out ATP
- What does fermentation mean?
Glucose is broken down in the absence of oxygen (anaerobic) to produce 2 ATP and lactic acid or ethanol (not humans)
- What is the by-product of alcohol fermentation?
- 2 lactic acid (humans), 2 ethanol, 2 CO2, 2 ATP
- Where in the cell does fermentation take place?
- Cytosol
- What are the two phases of photosynthesis?
- Light-dependent (thylakoid membrane)-uses light energy to generate ATP and NADPH)
- Light-independent (Calvin Cycle) (Stroma) - fixes carbon to form 3 carbon sugars utilizing Rubisco (enzyme). Converts 3PG to G3P
- How do plants broaden the spectrum of light they can accept from the sun?
Accessory pigments absorb light in other wavelengths, increasing the range of light that can be used
- Why do chloroplasts (thylakoids specifically) appear green to us?
The chloroplasts scatter light in the wavelength of green and absorb red, blue, orange.
Which color has higher energy, violet or red?
Violet: shorter wavelength
- What is a light harvesting complex (LHC)?
The LHC is a complex composed of a large number of pigment molecules, with two central chlorophyll A, bound to proteins. PS II = P680 central; PS I= P700
The function of the light energy complex is to trap the light and transfer it to reaction centers or photosystems, where absorbed light energy is converted into chemical energy
- What is a photosystem?
Photosystems are the functional units for photosynthesis, defined by a particular pigment organization and association patterns, whose work is the absorption and transfer of light energy, which implies transfer of electrons. Physically, photosystems are found in the thylakoid membranes
- What is a reaction center?
Light energy is captured in the light harvesting complexes and transferred to the reaction centers
Drives photolysis of H2O -> 1/2 O2 + H2 providing electrons and protons for ETC
What molecule is the electron donor for PSII?
H2O
- What is the byproduct (waste product) of the light reaction?
NADPH
- What is the difference between photosystem I and photosystem II?
Photosystem II comes first and is P680, while Photosystem II comes second and is P700.
- What are the main products produced from the light reactions?
ATP and NADPH
- What is the main product of cyclic photophosphorylation?
ATP
- Why are there two types of photosystems?
Photosystem I and photosystem II are the two multi-protein complexes that contain the pigments necessary to harvest photons and use light energy to catalyze the primary photosynthetic endergonic reactions producing high energy compounds
- Where does chemiosmosis take place in chloroplasts?
The thylakoid membrane
- What is the main purpose of the Calvin Cycle (dark reactions)?
Use RuBP in addition to ATP and NADPH (from the light reactions) to fix carbon (CO2) into 3 carbons sugars
- What is the primary carbon acceptor of the Calvin Cycle?
RuBP
- What is the function of Rubisco?
Fix carbon to RuBP to create a six carbon intermediate
- What does it mean to “fix” carbon?
CO2 is reduced by adding hydrogens and forming additional bonds to a carbon backbone resulting in a product with higher energy
- How is the newly added carbon atom reduced in the Calvin cycle? What donates the H?
Energy in ATP and NADPH are used to reduce CO2. NADPH donates the H
- What are the energy requirements of fixing carbon in the Calvin cycle?
It takes (6) turns of the Calvin cycle to fix (6) carbon atoms from (6) CO2. These (6) turns require energy input from 12 ATP (2 per turn) molecules and 12 NADPH (2 per turn) molecules in the reduction step and 6 ATP molecules in the regeneration step
- The establishment of a proton gradient across the thylakoid membrane is assisted by:
Functioning ETC between PSII and PSI
What is the deal with anaplerotic reactions?
Anaplerotic a reactions that (re)form intermediates of a metabolic pathway
oxolacetate = Kreb’s Cycle
RuBP = Calvin Cycle
What is the final electron acceptor in oxidative phosphorylation? Noncyclic photophosphorylation?
Final electron acceptor oxidative phosphorylation: Oxygen (O2 + 2e- + 2H+->H2O)
Final electron acceptor photophosphorylation:
NADP+ (NADP+ +e- +H+ -> NADPH)
