Chapter 9 - Cellular Respiration: Harvesting Chemical Energy Flashcards
Life is what?
Life is work
Living cells require what to survive?
Living cells require energy from outside sources
Organic compounds have what?
organic compounds have potential energy due to arrangement of atoms
when compounds are broken down into simpler compounds?
some energy is used as work the rest dissipates as heat
Anabolic and Catabolic Pathways are…?
Anabolic and Catabolic pathways are interconnected
An overview of Metabolism?
- In stage 1, macromolecules are hydrolyzed into their building blocks
- In stage 2, building blocks are further degraded into a few common metabolites
- In stage 3, small molecular weight metabolites like acetyl-CoA are degraded yielding ATP
The breakdown of molecules is?
an exergonic reaction
what is fermentation?
is a partial degradation of sugar that occurs without O2
what is aerobic respiration?
consumes organic molecules and O2 and yields ATP
what is anaerobic respiration?
is similar to aerobic respiration except it consumes compounds other than O2
what is cellular respiration?
includes both aerobic and anaerobic respiration but is OFTEN used to describe AEROBIC RESPIRATION
- it is helpful to trace cellular respiration with the sugar glucose
C6H12O6 + O2 -> 6CO2 + 6H2O + Energy (ATP + Heat)
The cellular respiration of glucose is…?
is a spontaneous reaction releasing -686kcal/mol
what are redox reactions?
chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions or redox reactions
The transfer of electrons during cellular respiration does what?
The transfer of electrons during chemical reactions releases energy in organic molecules
- this energy is ultimately used to synthesize ATP
what is oxidation?
a substance loses electrons or is oxidized
what is reduction?
a substance gains electrons, or is reduced (the amount of positive charge is reduced)
what is a reducing agent?
The electron donor is called the reducing agent
what is the oxidizing agent?
the electron acceptor is called the oxidizing agent
what do some redox reactions do?
Some redox reactions do not transfer electrons but change the electron sharing inc covalent bonds
during cellular respiration the fuel is…?
during cellular respiration the fuel (glucose) is oxidized and O2 is reduced
Energy Harvesting via NAD+?
- electrons from organic compounds are usually first transferred to NAD+, a coenzyme
- electrons travel attached to protons, which in turn do not get transferred directly to oxygen, but to NAD+
- As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration
- each NADH (reduced from NAD+)represents stored energy that is tapped to synthesize ATP
what is the electron transport chain (ETC)?
NADH passes the electron to the electron transport chain
- the ETC passes electrons in a series of steps instead of one explosive reaction
- The energy yielding is used to regenerate ATP
Cellular Respiration has 3 stages, what are they?
- Glycolysis
- The Citric acid Cycle (Krebs Cycle)
- Oxidative phosphorylation
what is glycolysis?
breaks down glucose into two molecules of pyruvate
what is the citric acid cycle?
completes the breakdown of glucose, pyruvate goes to CO2
what is oxidative phosphorylation?
accounts for most of the ATP synthesis because it is powered by redox reactions
- accounts for almost 90% of ATP synthesis during cellular respiration
what is substrate-level phosphorylation?
A smaller amount of ATP (10%) is formed in glycolysis and the citric acid cycle
Glycolysis happens with or without?
oxygen, it does not make CO2
- in the presence of O2, the energy produced is further used by the citric acid cycle and oxidative phosphorylation
Where does glycolysis occur?
in the cytoplasm
What are the two phases of Glycolysis?
- Energy investment phase
2. Energy Payoff Phase
The driving forces of glycolysis are?
Are these three reactions
- glucose
- G6P (glucose-6-phosphate)
- F6P (fructose-6-phosphate)
What happens during the Energy investment phase of glycolysis?
- Glucose is phosphorylated by enzyme, hexokinase
- Isomerization of glucose into fructose by the enzyme phosphoglucoisomerase
- sugar broken down into 2 smaller sugars of each other by Aldolase(breaks sugars) and isomerase(converts sugars into 2 small sugars)
What happens during the energy payoff phase of glycolysis?
- Enzyme catalyzes 2 reactions (oxidation and transfer of protons to NAD+, second phosphorylation)
- substrate-level phosphorylation creates 2 moles of ATP (Exergonic reaction, product is carboxylic acid)
- Enolase removes water to form PEP (Very high energy substrate)
- substrate-level phosphorylation creates ATP (Final Product Pyruvate with net gain of 2 ATP)
what is Acetyl-CoA?
before the citric acid cycle can begin, pyruvate must be converted into Acetyl-CoA, which links the cycle to glycolysis
Where does the Citric Acid Cycle occur?
within the mitochondrial matrix
What does the Citric Acid Cycle do?
The cycle oxidizes organic fuel derived from pyruvate, generating 1ATP, 3NADH, 1FADH2 per turn
An overview of The Citric Acid Cycle?
- The citric acid cycle has eight steps, each catalyzed by a specific enzyme
- The Acetyl-CoA joins the cycle by combining with oxaloacetate, forming citrate
- The next 7 steps decompose citrate back to oxaloacetate, making the process a cycle
- The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
what Happens after glycolysis and the citric acid cycle?
NADH and FADH2 account for most of the energy extracted from food
- These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation
The Electron Transport Chain?
- The ETC is in the cristae of the mitochondria
- most of the chains components are proteins, which exist in multiprotein complexes
- Electrons drop free energy as the go down the chain and are finally passed to O2, forming H2O
- ETC generates NO ATP
what are cytochromes?
Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2
What is ATP synthase?
ETC causes proteins to pump H+ from the mitochondrial matrix into the inter-membrane space, H+ then moves back across the membrane, passing through channels in ATP synthase
What type of flow does ATP synthase use?
ATP Synthase uses the EXERGONIC FLOW of H+ to drive phosphorylation of ATP
What is Chemiosmosis?
the use of energy in H+ gradient to drive cellular work
- an energy coupling system, that uses energy stored in the form of of a proton gradient to drive work
What is the proton-motive force?
The H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work
During Cellular respiration most energy flows in this sequence?
glucose -> NADH -> ETC -> proton-motive force -> ATP
Fermentation does what?
fermentation uses phosphorylation instead of ETC to generate ATP
What is Alcohol Fermentation?
pyruvate is converted to ethanol in two steps, with the first releasing of CO2
- Alcohol fermentation by yeast is used in brewing, winemaking and baking
what is Lactic Fermentation?
pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2
What do human muscle cells do?
Human muscle cells use lactic acid fermentation to generate ATP when O2 is limited
Cellular respiration and fermentation?
cellular respiration produces 38 ATP per glucose molecule and fermentation produces 2 ATP per glucose molecule
what are obligate anaerobes?
They carry out fermentation or anaerobic respiration and CANNOT survive on the presence of O2
what are facultative anaerobes?
They can survive using either fermentation or cellular respiration
- ie) yeast and many bacteria
Metabolic Regulation?
Cellular activity is regulated as needed
- Regulation may involve controlling key enzymes of metabolic pathways
How are enzymes controlled?
- Enzymes are controlled by alteration in active sites
What are the different types of alterations in active sites do enzymes undergo?
- Covalent Modification of enzymes regulated by phosphorylation such as protein kinases
- Allosteric Modulation by enzymes regulated by compounds binding to allosteric sites
what is feedback inhibition (a type of Allosteric Modulation)?
The product of the pathway allosterically inhibits one of the first enzymes of the pathway
- most common mechanism for control
