Topic 5: Energetics and Metabolism Flashcards
_______ (generally) are proteins made by cells that act as catalysts.
They catalyze specific reactions
Enzymes
________ are RNA enzymes
ribozymes
Different enzymes produced to catalyze the different reactions involved in a cell’s ___________.
metabolism
In the absence of a catalyst, a reaction won’t occur at any rate. Why?
Because bonds need to be broken to initiate reaction.
Needs activation energy
Enzymes work by lowering the _______ ______ of a reaction
activation energy
Enzymes ____(do/ do not) change the energetics (ΔG) or the equilibrium of the reaction
do not
By lowering the activation energy, enzymes ______ the rate of a reaction.
increase
_______ concentrations of substrates are increased at the active site of the enzyme.
Local
Molecules at the active site are __________ properly for the reaction to take place.
oriented
Many enzymes alter the _________ _______ and ________ _______ of the substrates, which enhances reactivity.
electronic distribution and
conformational structure
Most biological reactions will not occur at a significant rate in the absence of an _________
enzyme
In metabolic pathways, products from one reaction are the reactants in the next. What is the reason for this?
This prevents the accumulation of products of the individual reactants. Accumulation of products promotes the reverse reaction.
Enzyme activities can be controlled by regulating the amounts of the _______ or by controlling their activity.
enzymes
__________ ___________ of an enzyme “fit” in the same active site as the substrates.
They inhibit substrate binding and thus the reaction
This is the way many drugs work
Competitive inhibitors
__________ regulation of an enzyme: Catalytic activity of an enzyme controlled by a molecule (“effector”) that binds the enzyme at a location other than the active site.
Binding alters structure of the enzyme to control its activity
Allosteric
In allosteric regulation of an enzyme, effector binds reversibly to the _______ site.
The binding causes conformational changes in the _______ site
allosteric, catalytic
Allosteric _________ promote binding of substrate/catalysis
activators
Allosteric _________ prevent substrate binding/catalysis
inhibitors
In allosteric activators,
- Effector binds to allosteric site
- Causes conformational change in _____ site
- Substrate fits into active site
- Substrate will be converted into _______
active, product
What happens in the absence of effector?
- Substrate binds to active site
- catalysis proceeds
In allosteric inhibitors,
Effector binds at _________ site:
- Causes conformational change in ____ site
- Substrate can not bind
- Reaction inhibited
regulatory, active
_______ ________ is a common strategy to control metabolic pathways.
A strategy to prevent too much product from being made
feedback inhibition
In feedback inhibition, the _____ product acts as an inhibitor of an early step in pathway.
end
Microbial metabolism is essential for the way that organic elements (carbon, nitrogen) cycle through the ________.
environment
What is an example of an essential molecule that microbes produce for us?
Vitamin B12
Microbial metabolism in the ____ of animals (including us) plays an important role in their health
guts
4 Metabolic requirements for all life
- Liquid water
- Nutrients (sources of carbon, nitrogen, etc.)
- A source of energy to do work
- A source of electrons for biochemical reactions
All cells need a ______ source of the basic elements (C, N, P) that make up core molecules in the cell (DNA, protein, lipids)
usable
What is a possible reason why some microbes are hard to grow in the lab?
Many microbes have evolved in environments where certain nutrients are available and have lost (or never had) the ability to make them.
First law of ________ states that energy is neither created nor destroyed.
Thermodynamics
________ break down high energy molecules to lower energy molecules- use excess energy to power cell functions
Chemotrophs
Example of a chemotroph microbe
Escherichia coli
_________ capture energy from sunlight
Phototrophs
Example of a phototroph microbe
Rhodobacter capsulatus
What are two classification of microbes by where they get their carbon
- Autotrophs
- Heterotrophs
Two classifications of microbes by where they get their energy
- Chemotrophs
- Phototrophs
_______ use CO2 to build cell materials
- takes a lot of energy
- most chemolithotrophs and phototrophs are autotrophs
- primary producers- very important- synthesize the organic molecules that heterotrophs use.
Autotrophs
________ obtain carbon from organic compounds
- nearly all chemoorganotrophs
Heterotrophs
_____ is the energy currency of the cell. The conversion of this to ADP is used to power synthesis of cell components (proteins, membranes, cell wall) and to power other cellular functions (transport)
ATP.
Example of an energy source for group translocation. This is produced by e. coli
This energy can be used in similar manner as ATP hydrolysis for some reactions
Phosphoenolpyruvate (PEP)
__________ is a series of biochemical reactions needed to sustain life.
Metabolism
In _____________, reactions obtain energy and break down complex molecules.
reactants -> products
produce ATP
Catabolism
In _________, reactions used to synthesize cellular material (use energy)
precursors -> cellular materials
breakdown ATP
Anabolism
________ is the free energy change of a reaction under standard conditions.
Can be calculated based on nature of reactants/products.
(ΔG’) Standard Gibbs free energy
If you have a negative Gibbs free energy, reactants have more energy than products. This means that the reaction is _______ and _______
exergonic and spontaneous
If you have a positive Gibbs free energy, reactants have less energy than products. This means that the reaction is ________ and __________.
endergonic (requires energy) and not spontaneous
The actual ΔG is effected by: (3)
- temperature
- concentration of substrates
- concentration of products
Higher concentration of products than reactants leads to high ___ values, which increase ΔG values. This makes reaction less energetically favorable (in that direction)
K
In aerobic respiration of glucose, ATP production requires at least ___ kJ/mole
31.8
Some chemical reactions are _______ reactions (reduction/oxidation)
redox
Electrons captured from _____ energy state to ____ energy state can capture and use this energy.
high, lower
________ reactions are the basis for much cell metabolism- the source of energy of chemotrophs
Redox
Electrons are at a _____ energy state when they are associated with more electronegative atoms.
lower
C6H12O6 + 6 O2 ⇌ 6 CO2 + 6 H2O
Glucose is the electron ______, while O2 is the electron _____
donor, acceptor
C6H12O6 + 6 O2 ⇌ 6 CO2 + 6 H2O
Glucose loses electrons, is _______, while O2 gains electrons, is _________
oxidized, reduced
C6H12O6 + 6 O2 ⇌ 6 CO2 + 6 H2O
Glucose is oxidized to _______. O2 is reduced to _______
6 CO2, 6 H2O
C6H12O6 + 6 O2 ⇌ 6 CO2 + 6 H2O
In this redox reaction, _______ is a great source of high energy electrons. _______ is a great electron sink- leaves electrons at low energy state.
Glucose, Oxygen
________ is released by electrons moving to lower energy state. This is captured by the cell through a series of redox reactions.
Energy
_______ and ____ are an example of a redox couple (half reaction
Glucose (reduced form) and CO2 (oxidized form)
By convention, redox pairs are written as (oxidized form/reduced form), So: CO2/glucose
The ______ ______ of a redox couple indicates its propensity to act as an electron donor or acceptor.
reduction potential
redox couples with more negative values (top of redox tower) have a __________(stronger/weaker) tendency to act as electron donors (to be oxidized)
stronger
redox couples with more positive values (bottom of table) have a ____ tendency to act as electron acceptors (to be reduced)
strong
______ is a great electron donor, ___ is a phenomenal electron acceptor
Glucose, O2
Why is CO2/glucose a strong electron donor (-ve reduction potential)?
Glucose have several C-H bonds- electrons in high energy state.
In CO2 electrons have moved close to oxygen- lower energy state
Why is O2/H2O a strong electron acceptor (+ve reduction potential)
Oxygen is highly electronegative
- In O2, electrons equally shared
- In H2O, oxygen can “steal” electrons from hydrogen.
Electrons associated with oxygen are at a low energy state.
redox reactions between couples that have bigger differences in redox potential produce more __________
energy
Electrons are transferred from an initial electron donor to an ultimate acceptor over many ___________ reactions.
biochemical
Soluble electron carriers like ____________ are used to shuttle electrons around the cell. They are enzymatic cofactors.
NAD+/NADH
_______ is an oxidizing agent that gets reduced to NADH (reducing agent)
NAD+
NAD(P)H= reducing power
Used to power ____ synthesis or build cell materials
ATP
Electron carriers (such as NAD+/NADH) allow electrons donated in one reaction- stored in _______- and accepted in a different reaction
They are soluble
NADH
Reactant that _________ electrons
- e.g. - Glucose
- gets oxidized
- loss of electrons “electron donor”
- “reducing agent”
- often loses H atoms and/or gains O atoms
donates
Reactant that ________ electrons
- e.g. - O2
- gets reduced
- gain of electrons “electron acceptor”
- “oxidizing agent”
accepts
Metabolism is _________.
- can be thought of a set of inter-connected modules.
- a wide range of metabolites are shuttled into a limited number of central pathways (energy generation/ key biosynthesis reactions).
modular
What are the three ways to generate ATP?
- Substrate level phosphorylation
- Oxidative phosphorylation
- Photophosphorylation
This is a way to generate ATP in which ATP is generated as a product of a metabolic reaction. (exergonic reaction- use of excess energy to make ATP)
Substrate level phosphorylation
This is a way to generate ATP in which energy from electron transfer reactions generate a proton motive force, which is used to generate ATP.
Oxidative phosphorylation
This is a way to generate ATP in which energy captured from light is used to generate a proton motive, which is used to generate ATP
Photophosphorylation
What is a preferred energy source for many chemoorganotrophs?
sugars like glucose
From glucose to CO2, it is a ______ and _______ oxidation, not a single step.
slow and controlled
________ is broken down in a series of reactions in which high energy substrates are gradually oxidized into lower and lower energy molecules, ultimately CO2. Electron acceptors like _________ act as an electron sink- represent the ultimate electron acceptor in this reaction
Glucose, oxygen
_________ is a very important metabolic pathway found in all domains of life.
This is a quick way to produce some energy from glucose, also feeds into citric acid cycle
Glycolysis
In glycolysis, glucose is broken down into two _________ molecules over several steps.
pyruvate
Glycolysis ______(does/does not) require O2.
does not
