bio chapter 6 Flashcards
what happens in cellular respiration
oxygen is consumed as glucose is broken down to CO2 and H2O; the cell captures the energy released in ATP
where does cellular respiration take place
the mitochondria
what is cellular respiration
the aerobic harvesting of energy from food molecules by cells
what is the fundamental function of cellular respiration
generating ATP or cellular work
what are the reactants of cellular respiration
sugar and oxygen
what are the products of cellular respiration
carbon dioxide and water
is cellular respiration endergonic or exergonic
exergonic; them chemical energy of the bonds in glucose is released and stored in the chemical bonds of ATP
how is energy released in cellular respiration
a controlled descent of electrons; energy is released in small amounts that can be stored in the chemical bonds of ATP
what reactant is oxidized
glucose; loses hydrogen atoms (electrons) as it is oxidized to CO2;
what reactant is reduced
oxygen; gains hydrogen atoms (electrons) as it is reduced to h2o
what is the role of NAD+
use to shuttle electrons in redox reactions
how is breathing related to cellular respiration
in breathing, CO2 and O2 are exchanged between your lungs and the air. In cellular respiration, cells use the O2 obtained through breathing to break down fuel, releasing CO2 as a waste product
how many ATP molecules are generally produced from each molecule of glucose
32
what is a kilocalorie
the quantity of heat required to raise the temperature of one kilogram of water by 1 degree celsius
what is a redox reaction
the movement of electrons from one molecule to another
why do oxidation and reduction always go together
because an electron transfer requires both an acceptor and a donor
why do hydrogen movements represent electron transfers
because each hydrogen atom consists of an electron and a proton
what happens to electrons as they pass from glucose to oxygen
they lose potential energy
is NAD+ oxidized or reduced
reduced; accepts electrons and becomes NADH
what are the three main stages of cellular respiration
- glycolysis
- pyruvate oxidation and the citric acid cycle
- oxidative phosphorylation
where does glycolysis take place
the cytoplasm
what is the major function of glycolysis
breaks glucose into 2 molecules of a three carbon compound called pyruvate
where does the oxidation of pyruvate and the citric acid cycle take place
the fluid matrix of the mitochondria
what happens when pyruvate is oxidized
it becomes a 2 carbon compound
what does the citric acid cycle do
completes the breakdown of glucose to CO2
what is the main function of the first two stages of cellular respiration
to supply the third stage with electrons
what happens in chemiosmosis
the potential energy of the concentration gradient is used to make ATP
what does glycolysis begin with
a single molecule of glucose
what does glycolysis end with
2 molecules of pyruvate
what process is ATP formed by in glycolysis
substrate-level phosphorylation
what is substrate level phosphorylation
when an enzyme transfers a phosphate group from a substate molecule directly to ADP, forming ATP
how is glycolysis a metabolic pathway
each chemical step leads to the next one
ex: glucose 6-phosphate is the product of step 1 and the reactant for step 2
what is an intermediate
compounds that form between the initial reactant and final product
what are the 2 main phases of glycolysis
the energy investment phase
the energy pay off stage
what happens in the energy investment stage
ATP is used to energize a glucose molecule that is split into two sugars that are now primed to release energy
what happens in the energy payoff stage
2 NADH and 4 atp molecules are generated
how many molecules of ATP does one molecule of glucose need to make two molecules of G3P
2
how many phosphate groups and carbons does a G3P molecule have
1 phosphate 3 carbons
one molecule of G3P goes through a series of enzymatic reactions to ultimately make one molecule of what
pyruvate
what is the name of the hydrogen carrier used in glycolysis
NADH
what is the redox reaction that occurs during glycolysis with regard to the hydrogen carrier
NAD+ + H+ –> NADH
how many carbons does one molecule of pyruvate have
3
how many molecules of ATP are generated in the energy payoff phase of glycolysis
4
what is the net gain from glycolysis of one glucose molecule of molecules of ATP
2
what is the net gain from glycolysis of one glucose molecule of molecules of NADH
2
what is the net gain from glycolysis of one glucose molecule of molecules of pyruvate
2
what is the net gain from glycolysis of one glucose molecule of molecules of water
2
what is the chemical equation for cellular respiration
sugar + oxygen –> CO2 + water + energy
what reactant in cellular respiration is oxidized
glucose
what reactant in cellular respiration is reduced
oxygen
what reactant is used during glycolysis
sugar
what product is formed during glycolysis
water
what does anaerobic mean
doesnt require oxygen
what does aerobic mean
requires oxygen
is glycolysis aerobic or anaerobic
anaerobic
what happens when pyruvate is oxidized
- a carboxyl group is removed from private and given off as a molecule of CO2
- the 2-carbon compound remaining is oxidized while a molecule of NAD+ is reduced to NADH
- a compound called coenzyme A joins with the two-carbon group to form a molecule called acetyl CoA
how many molecules of pyruvate are oxidized for each molecule of glucose that enters glycolysis
2
how many molecules of acetyl CoA enter the citric acid cycle for each molecule of glucose that enters glycolysis
2
what part part of acetyl CoA actually enters the citric acid cycle
the 2-carbon acetyl part; coenzyme A splits off and is recycled
where does the citric acid cycle take place
the fluid matrix of the mitochondria
why is the krebs cycle also called the citric acid cycle
the first compound made in the cycle is the 6 carbon compound called citrate
how many ATP are made from one krebs cycle (1 pyruvic acid)
1
how many NADH molecules are made from one krebs cycle/pyruvate oxidation (1 pyruvic acid)
4
how many FADH2 molecules are made from one krebs cycle (1 pyruvic acid)
1
what does a cell have to do to be able to harvest the energy stored in NADH and FADH2
shut their high energy electrons to an electron transport chain
what happens in the electron transport chain
the energy from the oxidation of organic molecules is used to phosphorylate ADP to ATP
what begins the citric acid cycle
enzymes strip the CoA portion from acetyl CoA and combine the remaining two carbon acetyl group with the 4 carbon molecule oxaloacetate, which is already present in the mitochondrion; this creates the 6 carbon molecule citrate
how is energy from the acetyl group harvested
successive redox reactions; hydrogen atoms are stripped from organic acid intermediates and given to NAD+ to produce energy-laden NADH molecules
how many CO2 are produced in one krebs cycle
2
how many ATP are produced in one krebs cycle
1
what is present at the end of the citric acid cycle
the 4 carbon molecule oxaloacetate; it is regenerated and is ready for another cycle to start
how are FADH2 and NADH produced in the citric acid cycle
they are reduced by redox reactions from FAD to FADH2 and from NAD+ to NADH
where does the electron transport chain occur in the cell
in the inner membrane of the mitochondrion
what are the two carrier molecules that are the source of electrons for the electron transport chain
NADH and FADH2
what is the final electron receptor in the electron transport chain
oxygen
how many protein complexes are involved in the ETC
4, where most of the carrier molecules are
how many mobile carriers transport electrons between protein complexes in the ETC
2
in what direction are electrons passed through the ETC
down the energy staircase; energy is released
how do the protein complexes use the energy released from the electron transfers down the ETC
three of them use the energy released from the electron transfers to actively transport H+ across the membrane from where H+ is less concentrated to where it is more concentrated
what is chemiosmosis
a process that uses energy stored in a hydrogen ion gradient across a membrane to drive ATP synthesis
how does chemiosmosis work
the H+ gradient stores potential energy. this energy drives h+ ions through a channel in ATP synthase. The rush of H+ through the channel spins a component of the complex, activating catalytic sites that attach phosphate groups to ADP to generate ATP
how do many proteins produce their deadly affects
by interfering with some of the events in cellular respiration
what reactant is used in the ETC and what product is made
oxygen is used, water is made
what are three places where different categories of poisons obstruct the process of oxidative phosphorylation
- blocking the electron transport chain; ex: rotenone binds tightly with one of the electron carrier molecules in the first protein complex, which prevents electrons from passing to the next carrier molecule, ultimately preventing ATP synthesis and essentially starving a cell of energy; ex: cyanide and CO2 bind to an electron carrier in the 4th protein complex where they block the passage of electrons to oxygen. this means electrons can no longer flow, so no H+ gradient will be generated, so no ATP can be made
- inhibiting ATP synthesis; ex: oligomycin (used on the skin to combat fungal infections) blocks the passage of H+ through the channel in ATP synthase, preventing fungal cells from making ATP and thereby killing them (does not harm human cells bc it cant get through our outer layer of skin)
- make the membrane of the mitochondrion leaky to h+ ions; called uncouplers; electron transport continues as normally, but ATP cannot be made bc leakage of H+ through the membrane destroys the H+ gradient. cells continue to burn fuel and consume oxygen, but without making ATP; ex: DNP - all steps of cellular respiration proceed as normal except chemiosmosis and almost all energy is lost as heat
what is brown fat and how does it help hibernating organisms
an adaptation found in hibernating mammals and newborn babies. it’s cells are full of mitochondria and the inner mitochondrial membrane has an uncoupling protein that allows H+ ions to flow back down its concentration gradient without generating ATP. Instead there is ongoing oxidation of stored fuel stores and the generation of heat, which protects hibernating mammals and newborns from dangerous drops in body temp
when is brown fat more active in adults
in colder weather and in people who are skinnier; suggests that brown fat may cause lean people to burn calories faster; these tissues could be targeted for obesity-fighting drugs
how many ATP are made in glycolysis and the krebs cycle combined
4
how many ATP are made in oxidative phosphorylation
about 28
what is the total yield of ATP molecules per glucose
about 32
why is the exact number of ATP created in CR not known
- bc FADH2 adds its electrons later in the ETC, it contributes less to the H+ gradient and generates less ATP
- some energy of the H+ gradient may be used for work other than ATP production, such as the active transport of pyruvate into the mitochondrion
what % of a glucose’s potential energy can be harvested by the cell
about 34%
why does the ATP yield depend on an adequate supply of oxygen to the cell
bc most of the ATP generated by cellular respiration results from oxidative phosphorylation; without oxygen as the final electron acceptor, election transport and ATP production will stop
what is fermentation
a way of harvesting chemical energy that does not require oxygen
what is the metabolic pathway that generates ATP during fermentation
glycolysis
what must be present in order to oxidize glucose in glycolysis
NAD+ as an electron acceptor
how is there always NAD+ present for glycolysis under aerobic conditions
the cell regenerates its pool of NAD+ when NADH passes its electrons into the mitochondrion to the ETC
how is there NAD+ present under anaerobic conditions
fermentation provides an anabolic path for recycling NADH back to NAD+
what happens in lactic acid fermentation
NADH is oxidized to NAD+ as pyruvate is reduced to lactate; the lactate is carried in the blood to the liver where it is converted back to pyruvate and oxidized in the mitochondria of liver cells
when can muscle cells switch to lactic acid fermentation
when the need for ATP outpaces the delivery of oxygen via the bloodstream
how does the dairy industry use lactic acid fermentation by bacteria
to make cheese and yogurt
what happens in alcohol fermentation
yeasts and certain bacteria recycle the NADH made in glycolysis back to NAD+ while converting pyruvate to CO2 and ethanol
what is alcohol fermentation used for
brewing, winemaking, baking
can fermentation and cellular respiration happen simultaneously
yes
what are obligate anaerobes
many prokaryotes that live in stagnant ponds and in deep soil that require anaerobic conditions and are poisoned by oxygen
what are facultative anaerobes
can make ATP either by fermentation or by oxidative phosphorylation, depending on whether O2 is available; if O2 is available, the organism will always use aerobic respiration bc its more productive; ex: yeast and many other bacteria
are our muscle cells obligate anaerobes or facultative anaerobes
facultative
why are yeasts grown anaerobically to make wine and beer (why are the vats of beer and wine designed to keep air out)
so they will ferment sugars and produce ethanol because if there is any o2 present, they will use cellular respiration instead because it creates more energy
what are some characteristics of glycolysis that indicate it is an ancient metabolic pathway
- occurs universally (functions in both fermentation and respiration)
- does not require oxygen
- dose not occur in a membrane bound organelle
