Download Solution Worksheet Respiration

Enzymes and Cellular Respiration Worksheet
The first law of Thermodynamics states that matter cannot be created not destroyed ; it can only
change form
The second Law of Thermodynamics states that chaos in the universe increases. Another name
for chaos is entropy.
The reason : energy conversions result in the production of heat, which mostly is an un-usable
energy form for organisms.
A reaction that show a net loss of energy are called exergonic reactions. The opposite, an
endergonic reaction, requires addition of energy to proceed.
Enzymes are molecules that act as catalyst for chemical reactions; they lower the activation
energy for enzyme reaction and thus accelerate/increase reaction speed.
A substance used by an enzyme is called a substrate, which the enzyme turns into a product.
The area where the substance binds to the enzyme, and where chemical conversion happens, is
called the active site of the enzyme.
Enzymes are proteins ( a class of biomolecules) and temperature and pH can affect their 3dimensional configuration. The loss of enzymatic function by high temperature or pH is called
denaturation.
In-organic elements (individual atoms) such as Iron, magnesium that aid in the function of an
enzyme are called co-factors.
Organic elements (larger carbon based molecules) that aid in the function of enzymatic
reactions are called co-enzymes.
Chemical reactions that involve the loss of hydrogen and electrons are called oxidation
reactions.
Chemical reactions that result in the uptake of hydrogen and electrons are called reduction
reactions.
In general, the breaking down of larger molecules into smaller molecules are oxidation
reactions.
A phosphorylation reaction occurs when a phosphate is transferred from one molecule to
another. When a substrate transfers a phosphate to ADP to make ATP, it is referred to as
substrate phosphorylation.
What are the 2 metabolic pathways a cell can use and what determines which pathway is used?
Aerobic respiration & anaerobic respiration; they depend on the presence or absence of oxygen
Write the overall equation for cellular respiration.
Aerobic: C6H12O6 + 6O2 yields 6CO2 + 6H2O + Energy (ATP)
What are the 3 phases of the cellular respiration process ?
Anaerobic: Glycolysis, resulting in the formation of pyruvate
Aerobic: Complete oxidation of pyruvate into CO2 via formation of acetylCoA and entrance into
Citric Acid (Krebs) Cycle
Transfer of energy onto NADH and FADH2 and formation of ATP via electron transport chain
and ATP synthase (= oxidative phosphorylation)
Where in the cell does the glycolysis part of cellular respiration occur? Why?
Cytoplasm; the necessary enzymes are located there
Where in the cell does the Krebs (Citric Acid) cycle part of cellular respiration occur?
Occur inside the mitochondria, more specifically within the matrix of the mitochondria. Pyruvate needs
to enter mitochondria first and be oxidized to acetyl CoA for complete oxidation within Krebs Cycle.
Where in the cell does the electron transport part of cellular respiration occur?
Along the inner mitochondrial membrane (thus inside the mitochondria). NADH and FADH2 are
formed inside mitochondrial matrix and thy are passed to the ETC enzymes on the inside of the inner
mitochondrial membrane.
How many ATP are made in the glycolysis part of cellular respiration?
2 ATP are needed to energize glycolysis but 4 ATP’s are produced. So, the net effect is 2 ATP
produced ( via substrate phosphorylation = direct enzymatic transfer of a phosphate from a substrate
to ADP to form ATP)
How many ATP are made in the Kreb’s cycle part of cellular respiration? What else is important here ?
2 ATP (via substrate phosphorylation along Krebs cycle). The carbon skeleton is completey oxidized,
4 CO2 are released and the liberated energy is captured in the form of electrons/hydrogens and passed
onto the co-enzymes NAD+ and FAD
How many ATP are made in the electron transport part of cellular respiration?
About 28 ATP via the process of chemiosmosis. NADH and FADH2 pass their Electrons to the
Electron Transport Chain (ETC). When the electrons are passed down the ETC, it creates a hydrogen
gradient between inter mitochondrial space and matrix part of the mitochondria. When these
Hydrogens pass back into the mitochondria via the ATPsynthase, enough energy is released to make
ATP. ( 3 ATP’s for each NADH and 2 ATP’s for each FADH2)
Oxidation of Pyruvate to oxaloacetate generates 2 NADH = 2 x 3 = 6 ATP
The krebs cycle makes 6 NADH = 6 x3 = 18 ATP
The krebs cycle makes 2 FADH2 = 2 x 2 = 4 ATP
In which phase of cellular respiration is carbon dioxide made?
Pyruvate oxidation to oxaloacetate and Kreb’s cycle ( all happen inside the mitochondria; see 3rd
figure below)
What are NAD+ and FAD? What do they do and what do they become? Where are most made ?
They are co-enzymes and function as electron carriers; they become NADH and FADH2. 2 NADH
are formed during glycolysis (outside the mitochondria) , 2 NADH formed during pyruvate
oxidation and 6 NADH formed during the Krebs Cycle (TCA cycle). 2 FADH2 are also made
during Krebs cycle.
In which phase of cellular respiration is water made? WHY ?
In the electron transfer chain (ETC); more specifically, oxygen is the final electron acceptor in that
chain and becomes water ( oxygen becomes reduced to water)
What would happen to the cellular respiration process if the enzyme (aka catalyst) for one step of the
mitochondrial process was missing or defective?
The mitochondrial process would stop and no more products would be made. Pyruvate would
accumulate in cytoplasm and lots of lactic acid would start forming. Energy yield of the cell would
drop dramatically
Where does the process of fermentation take place?
Glycolysis is the process of Glucose break-down into pyruvate. It occurs in the cytoplasm. When
pyruvate is further oxidized within the cytoplasm, we call it fermentation. Since the mitochondria are
not involved, it is also referred to as anaerobic fermentation or anaerobic metabolism.
What are the products of fermentation?
For all mammals and most land dwelling vertebrates (animals with bones such as humans, cats,
reptiles,..), the process of fermentation results in the making of Lactic acid ( lactic acid fermentation). It
will occur when mitochondria do not have oxygen available to keep the ETC going. Hence, everything
backs up and pyruvate accumulates in the cytoplasm. The enzyme Lactate Dehydrogenase (LDH) will
then convert Pyruvate into Lactic Acid.
For yeasts and some other critters, LDH is missing but replaced with an enzyme called Alcohol
Dehydrogenase. It will convert Pyruvate into ethanol and CO2. ( also in the cytoplasm)
Anaerobic metabolism (aka fermentation) only produces 2 ATP per glucose molecule. Aerobic
metabolism (via mitochondrial oxidative phosphorylation) produces 32 ATP per glucose. Obviously, the
energy production goes down dramatically during anaerobic metabolism. One reason that it cannot
sustain activities for a prolonged period (unless the demand of metabolism is reduced dramatically as
well).