Download Bioenergetics Test Study Guide - Mater Academy Lakes High School

Mr. Ramos
Bioenergetics Study Guide
Students, here is a study guide for the Bioenergetics Test. Read it and study it carefully in conjunction
with your class & book notes. The Bioenergetics test has 50 Multiple Choice questions worth 50% of
your total class grade. The test is curved. Also, take advantage of this generous study guide. I will NOT
always do these nice things for you all.
Enzymes
SC.912.L.18.11
Explain the role of enzymes as catalysts that lower the activation energy of biochemical reactions. Identify factors,
such as pH and temperature, and their effect on enzyme activity.
Introduction
Enzymes are proteins known as biological catalysts.
In chemistry, a catalyst is a substance that speeds up a chemical reaction but is not consumed in the
reaction.
However, since this is not chemistry, we call them enzymes instead. We also call them enzymes because
they are inside your body.
Activation Energy
Enzymes speed up chemical reactions by lowering the energy of activation.
The energy of activation (aka activation energy) is the amount of energy needed
to get a reaction going.
In simple terms, imagine that you need to climb a very steep mountain. The
amount of energy that you need to go over the mountain is the energy of
activation. Now, imagine having a good friend called “enzyme.” Your friend,
enzyme, has the ability of lowering the mountain-top. Thus, you will now go over
the mountain without having to sweat about it.
This mountain is so
high! Please enzyme,
bring it down!
Activation Energy
Enzyme Naming
Enzymes are specific to the reaction that they catalyze (speed up). Therefore,
their names have something to do with the reaction that they catalyze.
Lactase, for example, is the enzyme that breaks down the sugar in milk, lactose.
Lactase only works for this type of reaction. Other reactions need their own
specialized enzymes.
Amylase is another type of enzyme that is present in human saliva. It is in charge
of breaking down starch into simple sugars.
Notice that both lactase and amylase end with the suffix –ase. This is true for the
majority of enzymes. If you see the “-ase” ending, then it is an enzyme.
Keep in mind that every rule has an exception. Not all enzymes end in –ase.
Pepsin is an enzyme found in your stomach that does not end in –ase.
Trypsin is an enzyme found in your small intestines that does not end in –ase.
Enzymatic Activity
Enzymes attach themselves to a substance called the substrate.
The enzyme and the substrate combine in a way similar to a lock-and-key.
This is called the enzyme-substrate complex. There is a slight change in
enzyme shape as it attaches to the substrate. This slight enzymatic change is
known as an induced fit.
Only a part of the enzyme called the active site catalyzes a reaction. By the
way, the fancy words catalyzes, catalysis, catalyst, etc…just mean speed up a
chemical reaction.
The substrate will bind to the enzyme’s active site to perform catalysis.
Factors Affecting Reaction Rates
Many things can affect enzymatic activity, but we will focus on three things: temperature, pH, and the
amount of enzyme or substrate.
Enzymes happen to work best at certain temperatures. For example, the enzymes in your body work
best at 37°C or 98.6°F. This is called the optimal temperature for these particular enzymes found in your
body. It is the temperature where these enzymes are working at their best (optimum). If you have a very
high fever, the enzymes will speed up, but then they may stop working.
Heat increases enzymatic activity. But too much heat denatures the enzymes (looses 3D shape).
On the other hand, cooling an enzyme may simply put the enzyme in a “sleep-like” state (inactive).
Enzymes also work better under optimal pH
concentrations. Remember that pH is a measurement
of the acid/base. The enzyme pepsin, found in your
stomach, has an optimal pH of about 1 or 2. Pepsin
may not work if the pH increases to become basic.
When an enzyme is outside its temperature and pH
range, it may lose its 3-dimensional protein shape
and become denatured.
Normally, a reaction will speed up if there are more enzymes to get
the job done. The converse is also true (less enzymes = slower
reaction).
Sometimes reaction rates can increase when you add substrates to a
reaction because it becomes easier for an enzyme to attach itself to
the substrate since there are so many of them. Thus, adding more
substrates may increase the reaction rate. However, if you continue
adding more substrates, the enzyme will come to a point where it
cannot work any faster, and the reaction continues at a steady speed.
Energy
SC.912.L.18.10
Connect the role of adenosine triphosphate (ATP) to energy transfers within a cell.
SC.912.P.10.1
Differentiate among the various forms of energy and recognize that they can be transformed from one form to
others.
Introduction
The first law of thermodynamics states that the energy in the universe cannot be created nor
destroyed. Energy in the universe is constant.
The second law of thermodynamics is the law of entropy. Entropy is a fancy
word for disorder. A system tends to want to be in disorder. For example, an ice
cube placed on a kitchen top could represent a system. Eventually the ice-cube
begins to melt causing a mess in your kitchen.
This disorder, or entropy, is a result of heat being released. Every chemical
reaction produces some heat that is lost to the surrounding.
Energy is constantly changing forms. For example, plants harvest the energy
from sunlight and transfer it to chemical energy found within sugars. Then,
an animal, such as a cow, may eat the plant and gather its chemical energy.
Finally, the cow is able to transform the chemical energy from the plant into
mechanical energy, which allows the cow to move around. In addition, the
cow will release heat to the environment.
ATP
ATP stands for adenosine triphosphate.
ATP is a high energy molecule composed of a ribose sugar, an
adenine base, and three high energy phosphate groups.
The energy in ATP is found in the bonds that connect each
phosphate. Energy is released when a phosphate is broken off.
ATP – 1 phosphate = ADP (adenosine diphosphate)
ADP – 1 phosphate = AMP (adenosine monophosphate)
(Most Energy)
ATP …………ADP…………AMP
(Least Energy)
ATP is the energy currency of the cell. Cell’s use ATP to carry out all biological
process, such as breathing, movement, talking, etc…
Photosynthesis
SC.912.L.18.7
Identify the reactants, products, and basic functions of photosynthesis.
Introduction
Photosynthesis is a process by which plants, green algae, cyanobacteria, and some protists use to
convert sunlight into chemical energy.
For this biology class we will focus on plant photosynthesis only.
6CO2 + 6H2O + sunlight  C6H12O6 + O2
(memorize this formula)
carbon dioxide + water + sunlight  sugar + oxygen
Photosynthesis mainly occurs in the leaves of plants in an organelle called the
chloroplast. Inside the chloroplast is a special pigment called chlorophyll. Pigments absorb light.
Chlorophyll is capable of absorbing red, violet, and blue. Chlorophyll,
however, cannot absorb green! Whatever is not absorbed will be
reflected. This is why plants are mainly green because green is
reflected onto your eyes.
There are two reactions that occur during photosynthesis:
light-dependent reaction and light-independent reaction.
The light-dependent reaction of photosynthesis occurs within the
chloroplast in disk-like structures called thylakoids.
The light-independent reaction of photosynthesis (sometimes called
the dark reaction) occurs within the chloroplast’s jelly-like substance
called the stroma.
The general concept of photosynthesis begins in
the thylakoids. (Light-dependent reaction)
*Water and light enter the thylakoids. The light
splits the water into oxygen gas, which is
released as a byproduct, and ATP & NADPH are
formed.
Light-dependent
Light-independent
The second part of photosynthesis will now
continue in the stroma (Light-independent
reaction)
*The ATP and NADPH made in the lightdependent reaction are used in conjunction with
carbon dioxide to power the Calvin cycle.
* Once the Calvin cycle is powered, sugars are
made. Since the energy in ATP and NADPH has
been used, these molecules are recycled as ADP
and NADP+.
Do not confuse the words stroma and stoma
The Light-dependent Reaction: Photoysystem II and Photosystem I
The light-dependent reaction occurs in the thylakoids of the chloroplast and is made possible by a
machinery of pigments and proteins called photosystem II and photosystem I. Notice that photosystem
II occurs first.
The products of the light-dependent reaction are oxygen, ATP, and NADPH.
PS II
Light and water enter the thylakoids within the photosystem II machinery. The light is absorbed by a
special chlorophyll pigment which absorbs light at 680 nanometers. We call this pigment P680.
The light splits the water, which causes the release of oxygen. This process also produces hydrogen ions
(H+ ions) and high energy electrons.
The high energy electrons are then passed down an electron transport
chain to produce energy in the form of ATP. As electrons pass down the
electron transport chain, hydrogen ions are pulled into the thylakoids
space. The high concentration of H+ ions are then forced out of an
enzyme called ATP synthase. When H+ ions pass through the ATP
synthase, energy is formed by combining a phosphate group to ADP to
produce ATP. This process of going from ADP to ATP with the help of
light is called photophosphorylation.
PS I
By the time the electrons from photosystem II reach photosystem I, they have very little energy. A
second light source must re-charge these electrons when they reach photosystem I. The pigment that
absorbs light in photosystem I is called P700 because it absorbs light at 700 nanometers.
The electrons are now energized and ready to pass a second and shorter electron transport chain. The
electrons are picked up by NADP+ in the stroma, along with H+. This produces the final product of the
light-dependent reaction, NADPH.
Please LOOK at the picture below and try to see what is happening as you read the information above
The Light-independent Reaction: The Calvin cycle
The light-independent reaction is sometimes called the dark reaction
or the Calvin cycle. We do not call it the dark reaction anymore
because it is misleading. It does not need to be dark for it to happen.
During the light-independent reaction, ATP, NADPH, and carbon
dioxide are used to make high-energy sugars.
The Calvin cycle: C3 Pathway
Carbon dioxide enters the Calvin cycle and mixes with a sugar called
Bisphosphate (RuBP). This occurs because of the enzyme
(Ribulose Bisphosphate Carboxylase).
The first organic compound to be formed in the Calvin cycle
is PGA, a 3 carbon molecule.
PGA is then energized by ATP and NADPH to produce a
higher-energy molecular state called PGAL or G3P.
Since G3P is the first product made, and it contains 3
carbons, this form of photosynthesis is called the C3
pathway. Many plants undergo the C3 pathway.
Notice that glucose is NOT the first sugar made. The first
sugar made is G3P, which is later turned into a variety of
sugars, such as glucose, sucrose, etc.
Photorespiration
Plants close their stomata when it is too hot in order to conserve water. Therefore,
carbon dioxide is not able to enter the plant, and the oxygen made is stuck in the
plant. This is not good news.
At this point, the plant’s enzyme, RuBisCo, will bind to the oxygen. This method
does not produce any energy at all (it actually wastes energy).
No sugars are produced either.
In summary, photorespiration is bad for plants. It takes their energy and does not
really do anything good for plants.
Evolutionarily speaking, some plants have adapted ways to deal with intense light,
high temperatures, and low carbon dioxide levels.
Ribulose
RuBisCo
C4 Pathway
The C4 pathway occurs in plants that are under intense light, high temperatures, and low carbon
dioxide.
The C4 pathway requires extra energy in the form of ATP, and it is
common in corn, sugarcane, and sorghum.
The C4 pathway uses two cells to perform photosynthesis:
Mesophyll cell and Bundle-sheath cell.
Carbon dioxide and PEP combine thanks to the enzyme PEP
carboxylase to form a 4 carbon molecule called Oxaloacetate. The
Oxaloacetate is later converted to another 4 carbon molecule
called Malate. This all happens in the Mesophyll cell. Because
Malate is a 4 carbon molecule, we call this the C4 pathway.
The Malate is then transferred to the bundle-sheath cell where it is
broken down into carbon dioxide and pyruvate. The carbon
dioxide is used to power the Calvin cycle while pyruvate is recycled
back to the Mesophyll cell to later be turned back into PEP.
Crassulacean Acid Metabolism (CAM) Photosynthesis
CAM plants are similar to C4 plants because they are adapted to very
hot and dry environments.
Examples of CAM plants include pineapple trees and many desert
cacti.
CAM plants allow air to go in only at night when they open their
stomata. At night, carbon dioxide is combined with organic acids and
stored in the plant. During the day when the
stomata are closed, these acids release the
carbon dioxide into the Calvin cycle to
produce carbohydrates.
Cellular Respiration
SC.912.L.18.8
Identify the reactants, products, and basic functions of aerobic and anaerobic cellular respiration.
SC.912.L.18.6
Discuss the role of anaerobic respiration in living things and in human society
Introduction
All organisms get energy from food. The energy in food is expressed in a unit called the calorie.
Cellular respiration is the process by which energy is released from food in the presence of oxygen.
C6H12O6 + O2  6CO2 + 6H2O + ATP (memorize this formula)
sugar + oxygen  carbon dioxide + water + energy
Notice that the formula for cellular respiration is the same as photosynthesis but backwards. Also notice
that the energy in photosynthesis is solar while in cellular respiration it is chemical energy.
Cellular respiration can occur aerobically (with oxygen) or anaerobically (without oxygen).
The process of glycolysis is always first and is present in aerobic and anaerobic respiration.
OXYGEN
Glycolysis
No
OXYGEN
Fermentation
Krebs cycle (citric acid cycle)
Lactic Acid
Fermentation
Electron Transport chain
&
Oxidative phosphorylation
Alcoholic
Fermentation
Aerobic Respiration (with oxygen)
If oxygen is present, cellular respiration will begin with glycolysis, form an intermediate called acetyl
CoA, enter the Krebs cycle, and finish with the electron transport chain and oxidative phosphorylation.
Technically speaking, glycolysis does not need oxygen to function, so it is anaerobic. Memorize this. It is
usually asked on all tests.
Glycolysis occurs in the cytoplasm of cells where 1 molecule of glucose is broken down into pyruvic acid
(aka pyruvate), ATP, and NADH.
Notice that in photosynthesis we dealt with NADPH and NADP+, but in cellular respiration we deal with
NADH and NAD+.
After glycolysis, the pyruvic acid is converted into acetyl CoA, which then enters the Krebs cycle.
The Krebs cycle takes place in
the matrix of the
mitochondria of eukaryotic
cells.
Acetyl CoA mixes with
Oxaloacetate to produce
citric acid (aka citrate). Since
citric acid is the first product,
we also call the Krebs cycle
the citric acid cycle.
The Krebs cycle produces
very little energy, some
carbon
dioxide (which you breathe
out), and a lot of electron
carriers
(NADH, FADH2) which will later be used to make a lot of energy.
The electron carries NADH and FADH2 are ready to dump
their electrons onto the inner membrane of the mitochondria called
the cristae. This is where the electron transport chain is found.
The electrons that are dumped on the electron transport chain are
passed on from protein to protein. As this is happening, the
intermembrane space of the mitochondria becomes filled with hydrogen
ions. These hydrogen ions are then forced to go back
into the matrix through the enzyme ATP synthase. Energy (ATP) is produced
in the process when ADP is attached to a phosphate. This is called phosphorylation. Since
oxygen is the final electron acceptor in the chain, we specifically call this step oxidative
phosphorylation.
The electron transport chain and oxidative phosphorylation together produce the most amount of
energy (about 36 molecules of ATP from 1 sugar in eukaryotes).
Notice how the
electrons force the H+
to go to the
intermembrane space.
Then notice how the H+
is forced back into the
matrix of the
mitochondria by the
“red” enzyme ATP
synthase. This produces
ATP.
Keep in mind that while not all organisms perform photosynthesis, ALL organisms perform cellular
respiration, including plants (ALL ORGANISMS)
One last thing to note is that while eukaryotes perform cellular respiration in their mitochondria,
bacterial cells do not contain mitochondria! So how do they do cellular respiration? They perform the
same functions in their cell membrane.
Anaerobic Respiration (without oxygen)
What happens where there is no oxygen?
Glycolysis will continue to run, since it is an anerobic process. It will produce the same products, pyruvic
acid, energy, and NADH. Unfortunately, we cannot have all this high energy NADH running around, so
we need something to bring it back to its lower energy state,
NAD+.
In alcoholic fermentation, the products of glycolysis are turned
into an alcohol called ethanol, carbon dioxide, and NAD+ (look
we managed to bring that high energy NADH back down to
NAD+). Unfortunately, no ATP is produced =( ….but at least we
get alcohol and bread =)
By the way, humans cannot do alcoholic fermentation. This is
done by the fungus yeast.
In lactic acid fermentation, the products of glycolysis are turned into lactic acid and NAD+ (look we
managed to bring that high energy NADH back down to NAD+). The lactic acid may cause muscle
soreness after you exercise. More fascinating though, bacteria use lactic acid fermentation to produce
cheese, yogurt, buttermilk, and sour-cream. COOL!
Comparing photosynthesis and cellular respiration
SC.912.L.18.9
Explain the interrelated nature of photosynthesis and cellular respiration.
Photosynthesis Equation:
6CO2 + 6H2O + sunlight  C6H12O6 + O2
Notice that these are the same equations but in
reverse to each other.
Cellular Respiration Equation:
C6H12O6 + O2  6CO2 + 6H2O + ATP
In photosynthesis we have solar energy while in
respiration we have chemical energy (ATP)
Photosynthesis removes carbon dioxide from the environment
while cellular respiration puts it back in the environment.
Keep in mind that animals cannot do photosynthesis. Only
plants, some bacteria, and some protists can perform
photosynthesis.
Also, keep in mind that ALL organisms can perform cellular
respiration. Plants are fortunate because they can do both
photosynthesis and respiration.
Some factors affect the rate of photosynthesis. These factors
include light intensity, temperature, and water. If photosynthesis is affected, so will cellular respiration.
For the most part, high light intensity and temperature increases photosynthesis (and thus respiration).
The reverse is also true. Low light and low temperatures stop photosynthesis (and thus respiration).
One last thing, fungi cannot perform photosynthesis! I know these little guys look like plants but they
are not plants. Fungi are decomposers; they are Heterotrophs (consumers not producers).