Study Questions # 5 Flashcards
September 24-28
What is metabolism, and what is the difference between anabolism and catabolism?
chemical reactions that occur in living cells.
anabolism builds bigger molecules and catabolism breaks them down
Why do cells need energy and what is the difference between potential energy and kinetic energy?
They need energy to do work. Potential energy is stored energy waiting to be used and kinetic energy is the energy that is being used.
What are the first and second laws of thermodynamics?
- energy can only be transferred, not created or destroyed
2. entropy is always increasing
What is free energy?
energy available to do work
- includes enthalpy (H) energy in chemical bonds
- 2 disordering influences: T and entropy
- ordering influences-disordering influences
- ΔG=ΔH-TΔS
How can you predict in which direction a reaction will proceed?
use ΔG
- exergonic reaction: -ΔG, products have less energy than reactants
- endergonic reaction: +ΔG, reactants have less energy than products
What is an exergonic reaction and how does it differ from an exothermic reaction?
exergonic reaction- releases energy, products contain less free energy or more disorder than reactants
exothermic-releases heat
Why can’t thermodynamics tell you how fast a reaction will go?
need to know activation energy to determine this; first need to break existing bonds; reactions with high activation energies proceed more slowly
What is activation energy?
energy needed to start a reaction
What is a catalyst?
substance that speeds up the rate of a chemical reaction
What is an enzyme and why do cells need enzymes?
biological catalyst
increases rate of reaction by lowering activation energy
controls metabolism
How do enzymes work?
Lower activation energy needed to start a chemical reaction
Why can some RNA molecules catalyze reactions?
ribozymes can change shape and put pressure on existing bonds
What is an active site?
the position in an enzyme where substrates bind
What is the difference between the lock and key and induced fit models?
lock and key is when the active site is an exact shape and the substrate has to fit just right. The induced fit model is that the active site changes shape to mold to the substrate
Why is the induced fit model favored?
explains how enzyme stresses bonds of substrate
explains why enzyme releases products
What is the catalytic cycle of an enzyme?
- free substrate and enzyme
- substrate binds enzyme
- active site changes shape
- reaction occurs
- products released, restart
Why do we know that binding and catalysis are separate activities?
some drugs prevent binding, some prevent catalysis
Why can we measure an enzymes activity by measuring the rate at which its products accumulate?
if enzyme works, products will form
What factors affect how well enzymes work?
pH and temperature, concentration of the substrate, concentration of the enzyme, presence of inhibitors, presence of coenzymes, rate of enzyme production
How does temperature affect enzyme activity?
temperature increases enzyme activity to a point until the enzyme breaks down
What is the difference between competitive and non-competitive inhibitors?
competitive inhibitors bind to active site and block it
noncompetitive inhibitors bind at allosteric site and active site changes shape
How can we tell whether an inhibitor is competitive or non-competitive
if it’s competitive, it can overcome inhibition by adding more substrate and it will out-compete the inhibitor
What is the difference between an active site and an allosteric site?
an active site is where the substrate binds and the allosteric site is where noncompetitive inhibitors or activators bind
What is an activator?
bind enzyme at the allosteric site, keeping enzyme in active configuration to increase enzyme activity
What is a cofactor?
a non protein part of the enzyme that some enzymes require to be active
What is a coenzyme?
type of cofactors that are organic
Why do you get pellagra if you don’t get enough Vitamin B3?
it’s a cofactor for redox reactions, it’s the active part of NAD
Why do cells have an energy currency?
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What is NAD and what does it do?
electron carrier/energy carrier
-strips electrons from glucose
What is ATP and why is it used in so many different reactions?
-main energy currency
-source of energy for driving endergonic reactions
-when phosphate is broken off ATP energy is released
-energy from glucose must be transferred to
ATP
How can cells perform endergonic chemical reactions?
the breakdown of ATP
What is a coupled reaction?
energy required by 1 process is supplied by another process
What is a biochemical pathway?
biological reactions that occur in a series
What is feedback inhibition and why is it useful?
final product of pathway binds to allosteric site of first enzyme in pathway and inhibits it, reaction stops
How do cells recover potential energy stored in reduced organic chemicals?
oxidize reduced bonds and the electrons are picked up by NAD+
What is electron transport (when talking about respiration)?
series of electron carriers embedded in inner mitochondrial membrane
increases electronegativity as they go along, energy released as they pass and the energy is used to make ATP
What is the role of oxygen in most eukaryotic cells?
it’s the final electron acceptor, will be converted to water
What is the difference between oxidative respiration and fermentation?
oxidative respiration needs oxygen as the final electron acceptor while fermentation has an organic as the final electron acceptor
Why does transporting electrons from H to O release energy?
as electrons flow from H to O they release energy because they’re moving to something more electronegative
What are the two ways that cells can make ATP?
substrate level phosphorylation and oxidative respiration
What is substrate level phosphorylation?
direct enzymatic transfer of a phosphate to ADP by kinase
What are the two distinct parts of oxidative respiration and how are they linked?
- oxidizing food 2. make ATP
rely on each other for substrate
What are the three stages of glucose oxidation?
- glycolysis
- pyruvate oxidation
- krebs cycles
What are the two stages of ATP generation in oxidative respiration?
- electron transport
2. chemiosmotic ATP synthesis
What is glycolysis?
breakdown of glucose to 2 pyruvate
What are the two stages and four steps of glycolysis?
- energy input (glucose to 2 G3P)
- payoff (2G3P to pyruvate)
- glucose priming(uses 2 ATP, glucose to fructose + 4 PO4)
- cleavage and isomerization (makes 2 G3P, breaks fructose into two 6 carbon sugars)
- oxidation(G3P gives NADH two electrons)
- ATP Generation (4 reactions change 13 G3P into pyruvate)
What are the substrates and products of glycolysis?
substrates:
- 1 glucose
- 2 ATP
- 4 ADP
- 2NAD+
products:
- 2 pyruvate
- 2ADP
- 4ATP
- 2 NADH
Where does glycolysis occur?
cytoplasm
Why do we need to consume ATP to start glycolysis?
prime glucose with P from ATP provides activation energy
How is G3P oxidation coupled to ATP synthesis?
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Why is it necessary to regenerate NAD+
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why do we accumulate lactic acid at the end of running a race
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Why do yeast make ethanol?
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Where is pyruvate oxidized?
mitochondrial matrix
What are the substrates and products of pyruvate oxidation?
substrates:
- pyruvate
- CoA
- NAD+
Products:
- acetyl-coA
- CO2
- NADH
Why is pyruvate oxidation considered a distinct stage of of oxidative respiration?
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Why is acetyl-CoA a central molecule of energy metabolism?
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Why do people who eat too much carbohydrate or protein get fat?
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How did you measure how well lactase worked in the enzyme lab?
the more yellow the solution was, the more product we had
Why did the ONPG change color in the enzyme lab?
a reaction occurred
Why can one lactase enzyme create thousands of products?
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