Biology Unit 3 - Chapters 6-8
Step 2: Reduction of Carbon Dioxide
The first 3-carbon molecule in the Calvin cycle is called 3PG (3-phosphoglycerate). Each of two 3PG molecules undergoes reduction to G3P (glyceraldehyde-3-phosphate) in two steps: Energy and electrons are needed for this reduction reaction, and they are supplied by the ATP and NADPH that were made during the light reactions. The difference between 3PG, BPG, and G3P (all with 3 carbons) is that G3P is reduced, has more electrons, and is now more chemically able to store energy and form larger organic molecules, such as glucose.
where does glycolysis occur
cytoplasm
where does the calvin cycle occur
in the stroma
where does pyruvate oxidation occur
mitochondrion
Energy to move electrons down the electron transport chain during the light reactions of photosynthesis comes from
sunlight
photosynthesis
- life on earth depends on photosynthesis for food - photosynthesis produces oxygen - plants take up carbon dioxide from the atmosphere - reactants and products of photosynthesis - there are several different photopigments - effects of different colors of light on photosynthesis - location of the reactions within the chloroplast
which are method(s) to measure the activity of an enzyme
- measuring how much substrate is used - measuring how much product is made
the activity of catalase can be measured as the rate of
- oxygen formation - hydrogen peroxide breakdown
arrange the steps of protein breakdown for cellular respiration
- proteins are broken down into single amino acids - amino groups are removed from amino acids - remaining carbon chains enter glycolysis or the Kreb's cycle
arrange the steps that occur in a photosystem in order
- sunlight excites electrons in a chlorophyll molecule - energy is passed to the reaction center of the photosystem - energy is passed to an electron harvested from water - an electron acceptor captures the high energy electron - the high energy electron is used to produce ATP and NADPH
at very high temps enzymes can exhibit less activity or none at all. which of the following could explain this
- the active site has changed shape so that the substrate no longer fits properly - the enzyme has denatured and cannot interact with the substrate
catalase is the enzyme that catalyzes the reaction that breaks down hydrogen peroxide to oxygen and water. what will happen as the reaction between catalase and hydrogen peroxide proceeds
- the amount of oxygen gas formation increases - the amount of hydrogen peroxide decreases
what will happen if the test tubes are left to react for an hour instead of 20 seconds
- the bubbles will burst - all the tubes will have produced approximately the same amount of bubbles - the bubbles will no longer be formed
Why is enzyme concentration not used to measure the rate of the enzyme-catalyzed reaction
- the concentration of an enzyme does not change - an enzyme is not used up in a chemical reaction
Most enzymes end with the suffix
-ase
place in order the steps of demonstrating the effect of temperature on enzyme activity.
1. let catalase equilibrate to a given temp. 2. wait at least 1 minute 3. add hydrogen peroxide 4. wait 20 seconds 5. measure height bubble column
Inputs and Outputs of Glycolysis
All together, the inputs and outputs of glycolysis are as follows: Notice that, so far, we have accounted for only 2 of the 36 to 38 ATP molecules that are theoretically possible when glucose is completely broken down to CO2 and H2O. When O2 is available, the end product of glycolysis, pyruvate, enters the mitochondria, where it is metabolized. If O2 is not available, fermentation, which is discussed in Section 8.3, occurs.
Light reactions
Are so named because they occur only when the sun is out During the light reactions, solar energy energizes electrons, which move down an electron transport chain As the electrons move down the chain, energy is released and captured to produce ATP molecules. Energized electrons are also taken up by NADP+, which is reduced and becomes NADPH. This equation can be used to summarize the light reactions, because during the light reactions solar energy is converted to chemical energy: Solar energy → chemical energy (ATP, NADPH)
Energy Investment Step
As glycolysis begins, two ATP are used to activate glucose by adding phosphate. Glucose eventually splits into two C3 molecules known as G3P, the same molecule produced during photosynthesis. Each G3P has a phosphate group, each of which is acquired from an ATP molecule. From this point on, each C3 molecule undergoes the same series of reactions.
Which of the following is not common to the chloroplast and mitochondria?
Both use sunlight as a source of energy.
complete the formula for cellular respiration
C6H12O6 + 6O2 --> 6O2 + 6 H2O ADP + P ---> ATP
CAM Photosynthesis
CAM stands for crassulacean-acid metabolism; the Crassulaceae is a family of flowering succulent (water-containing) plants, such as a jade plant, that live in warm, dry regions of the world. CAM was first discovered in these plants, but now it is known to be prevalent among other groups of plants as well, such as pineapples. Whereas a C4 plant represents partitioning in space—carbon dioxide fixation occurs in mesophyll cells, while the Calvin cycle occurs in bundle sheath cells—CAM is partitioning by the use of time. During the night, CAM plants use PEPCase to fix some CO2, forming C4 molecules, which are stored in large vacuoles in mesophyll cells. During the day, C4 molecules (malate) release CO2 to the Calvin cycle when NADPH and ATP are available from the light reactions (Fig. 7.17). The primary advantage for this partitioning again has to do with the conservation of water. CAM plants open their stomata only at night; therefore, only at that time does atmospheric CO2 enter the plant. During the day, the stomata close; this conserves water, but CO2 cannot enter the plant. Photosynthesis in a CAM plant is minimal, because a limited amount of CO2 is fixed at night, but it does allow CAM plants to live under stressful conditions.
Select all of the products produced during the citric acid cycle of cellular respiration
CO2, NADH, ATP, FADH2
The stomata of a plant allow ___ ____ to enter the leaf tissues
Carbon dioxide
Select the reactants for the process of photosynthesis
Carbon dioxide and Water
Beginning with the influx of CO2 from the air, list the three steps of the calvin cycle in the correct order
Carbon dioxide fixation, carbon dioxide reduction, regeneration of RuBP
stomata
Carbon dioxide in the air enters a leaf through small openings called
which step of cellular respiration produce ATP
ETC, glycolysis, Kreb's cycle
The second law of thermodynamics explains that ____ is always increasing in the universe
Entropy
Which of the following is not produced by glycolysis?
FADH2
When 3PG becomes G3P during the light reactions, carbon dioxide is reduced to carbohydrate. _______
FALSE
Which of these is an advantage of lactic acid fermentation over cellular respiration
Fermentation provides a rapid burst of energy when oxygen supplies are limited
the main product of the calvin cycle is a three-carbon molecule called
G3P
During the energy harvesting step of glycolysis, G3P is oxidized when ___ picks up hydrogen ions
NAD+
It is important that NAD+ is regenerated during fermentation because
NAD+ is required for glycolysis to continue
Fermentation is primarily involved in the recycling of
NAD+.
The reduction of NAD+ produces
NADH.
Electrons moving from water to NADP+ are in the ____ pathway
Noncylic
Match the following types of reactions with the proper description
Oxidation reaction = the loss of electrons or hydrogen ions Reduction reaction = the gain of electrons or gain of hydrogen ions
The final electron acceptor at the end of the electron transport chain is
Oxygen
Which process converts solar energy into chemical energy in the form of a carbohydrate?
Photosynthesis
Photosynthesis in Flowering Plants
Photosynthesis takes place in the green portions of plants. The leaves of a flowering plant contain mesophyll tissue, in which cells are specialized for photosynthesis The raw materials for photosynthesis are water and carbon dioxide. The roots of a plant absorb water, which then moves in vascular tissue up the stem to a leaf by way of the leaf veins. Carbon dioxide in the air enters a leaf through small openings called stomata After entering a leaf, carbon dioxide and water diffuse into chloroplasts, the organelles that carry on photosynthesis
Which molecular complex of the thylakoid membrane results in the production of oxygen during the light reactions
Photosystem ll (PSll)
During the prep reaction, _ is converted into acetyl-CoA
Pyruvate
The 3-carbon end product of glycolysis is
Pyruvate
First Law of Thermodynamics
States that energy cannot be created or destroyed, only transferred.
Electrons move along a series of carrier molecules from a higher to lower energy level during which phase of cellular respiration
The electron transport chain
Which two of the following are true about the relationship between the light reactions and the calvin cycle reactions
The outputs of the light reactions are the inputs for the calvin cycle AND some of the products of the calvin cycle reactions feed back into the light reactions so that carbohydrates production can continue
Cellular Respiration
The process by which cells make energy using oxygen and the nutrients produced during photosynthesis in order to produce ATP molecules.
Most often, cellular respiration involves the complete breakdown of glucose to carbon dioxide and water (H2O):
This equation shows that cellular respiration is an oxidation-reduction reaction. Recall that oxidation is the loss of electrons and reduction is the gain of electrons (see Section 6.4); therefore, glucose has been oxidized and O2 has been reduced. Also remember that a hydrogen atom consists of a hydrogen ion plus an electron (H+ + e-). Therefore, when hydrogen atoms are removed from glucose, so are electrons; similarly, when hydrogen atoms are added to oxygen, so are electrons. Cellular Respiration picture in notes on 37
Metabolism: Energy & Enzymes
To maintain their structural organization and carry out metabolic activities, cells—and organisms comprised of cells—need a constant supply of energy The general characteristics of life, including growth, development, metabolism, and reproduction, all require energy.
enzymes can be used over and over many times (T/F)
True
Plants use wavelengths of ____ to power the process of photosynthesis
Visible light
the krebs cycle begins when acetyl CoA is bonded to
a 4-carbon carrier
in this experiment you will study the CO2 up take due to photosynthesis. what should you use as a control sample
a tube without elodea
Fatty acids are broken down to
acetyl groups, which enter the citric acid cycle.
The role of an enzyme is to reduce the ___ ___ required to kickstart a chemical reaction
activation energy
what will cause the size of the space in the top of the small tube to change in volume
an increase in the production of carbon dioxide from fermentation
which type of process is alcoholic fermentation
anaerobic
which of the following types of organisms perform photosynthesis
bacteria, protists, plants
in the calvin cycle, the production of carbohydrates requires a source of __ atoms
carbon
which gas is given off by cell respiration
carbon dioxide
which of the fermentation products produced by yeast is a gas
carbon dioxide
which reactant is a gas and serves as a source of carbon atoms for photosynthesis
carbon dioxide
which product of yeast fermentation is used in the beer-making industry
carbon dioxide and ethanol
which of the following are end products of pyruvate oxidation (prep reaction)
carbon dioxide, NADH, acetyl CoA
in which tubes did hydrogen peroxide get broken down into water and oxygen
catalase + hydrogen peroxide
which of the following combinations demonstrates that the enzyme catalase is specific for the substrate hydrogen peroxide
catalase + water
Lab
catalase activity can be detected by observing the formation of oxygen bubbles
how is the temperature of the chemical reaction in this experiment controlled
catalase is either heated or cooled before adding to the substrate
Photosystem
consists of a pigment complex (molecules of chlorophyll a, chlorophyll b, and the carotenoids) and electron acceptor molecules within the thylakoid membrane. The pigment complex serves as an "antenna" for gathering solar energy.
The ATP and NADPH from the light reactions are used to
convert 3PG to G3P.
The function of light reactions is to
convert light energy into a usable form of chemical energy.
if catalase is present in excess, reducing the amount of hydrogen peroxide in the reaction mix will ____ the amount of oxygen gas formed
decrease
if photosynthesis occurs in an aquatic plant like elodea, the carbon dioxide concentration in the surrounding solution will
decrease
enzymes heated up at a very high temp can lose activity due to which of the following
denaturation
Anaerobic
does not require oxygen
disorder in the universe is known as
entropy
what is the final product of anaerobic respiration
ethanol
cellular respiration releases energy, so it is an ___ reaction
exergonic
what happens to carbon dioxide produced during cellular respiration
exhaled from the lungs
when a molecule is reduced, it ___ energy
gains
which group of beans will require the most cellular energy in the form of ATP
germinating beans
which of the following are needed to begin the step of glyoclysis
glucose
ATP
is a molecule that carries energy within cells.
raising the pH or lowering the pH from the optimal pH of an enzyme will ____ the activity
lower
•The sum of all chemical reactions in a cell is called
metabolism
where does the Kreb's cycle occur
mitochondrion
where does the electron transport chain occur
mitochondrion
which of the following is another name for simple sugars
monosaccharide
an enzyme at its optimum pH will produce a column of bubbles that is higher than when it is not at its optimum pH because it is ___ active
more
C4 photosynthesis
occurs in plants whose bundle sheath cells contain chloroplasts. is an advantage when the weather is hot and dry. Both b and d are correct.**
Organization of a Thylakoid:
on page 27 of notes
•Oxidation-Reduction Reactions
oxidation is loss reduction is gain
•Each enzyme has an optimal temperature and optimal ___ at which the rate of the reaction that it catalyzes is highest
pH
•In which of the following processes is carbon dioxide is reduced to form carbohydrates?
photosynthesis
almost all enzymes are ____
proteins
which of the following are needed to begin the step of pyruvate oxidation (prep reaction)
pyruvate
The preparatory
reaction takes place in the matrix of the mitochondrion. Pyruvate is broken down from a 3-carbon (C3) to a 2-carbon (C2) acetyl group, and a 1-carbon CO2 molecule is released. Since glycolysis ends with two molecules of pyruvate, the prep reaction occurs twice per glucose molecule.
a ____ reaction involves transferring electrons by oxidizing one molecule and using the electrons to reduce another
redox
•The gain of electrons by a molecule is called
reduction
edergonic reactions
require an input of energy to occur
Aerobic
require oxygen
Carbon dioxide enters leaves through a small opening called the
stoma
The Calvin cycle takes place in the ___ of a chloroplast
stroma
the fluid matrix inside a chloroplast is called the
stroma
it is essential that the catalase is properly equilibrated to the cold, warm and hot temps before the experiment starts. why
temperature is the independent variable in the experiment and must be set accurately
NADH & FADH2 are __ ___ __
temporary electron acceptors
click the answer you think is right
the active site of an enzyme closely matches the shape of its substrate
why did the volume of gas in the volumeter with the germinating beans change
the beans took up oxygen for cellular respiration
compared to other test tubes, what did you observe when the catalase reached its optimum pH
the bubbles were at their highest
The greatest contributor of electrons to the electron transport chain is
the citric acid cycle.
The metabolic process that produces the most ATP molecules is
the electron transport chain.
The first law of thermodynamics
the law of conservation of energy—states that energy cannot be created or destroyed, but it can be changed from one form to another.
in the concentration exercise, which test tube produced the highest column of bubbles after the same amount of time
the one with the most enzyme
How many turns of the calvin cycle are necessary for one G3P to exit
three
why is it important to stir the yeast before adding it to the test tubes
to make the yeast concentration uniform so all the samples get the same amount
the first law of thermodynamics explains energy cannot be created or destroyed, only ______
transferred
True or false: when NADP+ is reduced, it accepts electrons; when NADPH is oxidized, it gives up electrons
true
catalase activity can be detected by observing the formation of oxygen bubbles
true
different types of enzymes may differ in optimal temperature and pH requirements, depending upon where and how they function
true
the amount of enzyme does not change. therefore enzymes can be re-used and convert more substrate to product
true
true or false, changing the pH of an enzyme reaction can alter how rapidly product is formed
true
three test tubes are set in a rack, and contain the following: Tube 1: 4 ml hydrogen peroxide and 3 ml catalase Tube 2: 4 ml hydrogen peroxide and 1 ml catalase Tube 3: 4 ml hydrogen peroxide and 7 ml catalase in which tube will you observe the highest column of bubbles
tube 3
which of the following describes the structure of a dissaccharide
two monosaccharides bonded together
electrons for the light reactions are provided by
water
which of the following are products created during cellular respiration
water, carbon dioxide, ATP
all of the wavelengths of visible light combine to form ____ light
white
the law of thermodynamics explains
why energy flows through ecosystems and through cells
in which organisms is ethanol produced as a result of fermentation
yeasts
•The reactants in the process of cellular respiration are
•Glucose •Oxygen
•Which of the following is incorrect regarding ATP?
•It is stable
•What happens to an enzyme after the reaction is completed
•It returns to its original shape
energy
•Obviously, plant cells do not create the energy they use to produce carbohydrate molecules; that energy comes from the sun. Is any energy destroyed? No, because the heat the plant cells give off is also a form of energy. Similarly, as a moose walks, it uses the potential energy stored in carbohydrates to kinetically power its muscles. As its cells use this energy, none is destroyed, but each energy exchange produces some heat, which dissipates into the environment
•The major difference between coenzymes and cofactors is that coenzymes are ___ molecules and cofactors are ___ molecules
•Organic / Inorganic
•Which of the following environmental conditions may have an influence on enzyme activity?
•Substrate concentration, temperature, pH
•Free Energy is
•The amount of energy left to do work after a chemical reaction has occurred
•Chloroplasts and Photosynthesis
•The chloroplasts in plants capture solar energy and use it to convert water and carbon dioxide into a carbohydrate
Temperature
•Typically as temperature rises, enzyme activity increases •This occurs because warmer temperatures cause more effective collisions between enzyme and substrate The body temperature of an animal seems to affect whether it is normally active or inactive (Fig. 6.8b, c). It has been suggested that mammals are more prevalent today than reptiles because they maintain a warm internal temperature that allows their enzymes to work at a rapid rate.
free energy
•is the amount of energy left to do work after a chemical reaction has occurred
What is the estimated ATP production from one glucose molecule
30 ATP
Identify the tissues and structures marked in the cross section of this leaf ON PAGE 20 OF NOTES
A = Leaf vein B = Stomata C = Cuticle D = Epidermis E = Mesophyll
thylakoids
A different membrane system within the stroma forms flattened sacs called
stroma
A double membrane surrounds a chloroplast, and its semifluid interior is called the
which of the following is an endergonic (energy-requiring) reaction
ADP + P --> ATP
ATP synthase produces
ATP
During the energy-investment step of glycolysis, ___ is invested to start the reaction
ATP
If an enzyme reaction requires energy, it uses ___
ATP
The electron transport chain produces 32-36 molecules of _____
ATP
•The molecule that cells commonly use for energy
ATP
•The molecule that provides the energy to drive endergonic reactions in the body is abbreviated
ATP
Which molecules are needed for the reduction of 3PG to G3P
ATP and NADPH
ATP Cycle
ATP cycle is powered by the breakdown of glucose and other biomolecules during cellular respiration. However, according to the second law of thermodynamics, this process is not very efficient. Only 39% of the free energy stored in the chemical bonds of a glucose molecule is transformed to ATP; the rest is lost as heat.
Which of the following are the products of the light reactions of photosynthesis
ATP, NADPH, O2
which of the following are products of the light reactions of photosynthesis
ATP, oxygen and NADPH
which of the following are end products of glycolysis
ATP, pyruvate, NADH
the purpose of the light reactions is to create __ and ___ which are then used to power the ____ ____
ATP; NADPH; calvin cycle
Which of the following is an input to the citric acid cycle
Acetyl groups
arrange the steps of the light reactions in order
- an electron harvested from water is placed in the reaction center of photosystem II - sunlight excites the electron in photosystem II and it is captured by a primary electron acceptor - the excited electron is passed to an electron transport chain that uses its energy to pump hydrogen ions across the membrane - they hydrogen ions flow back through ATP synthase which allows it to create ATP from ADP & P - the electron is re-energized in photosystem I and captured by NADPH - NADPH and ATP are sent to the calvin cycle
Enzymes
- are essential for chemical reactions - are never used up - activity is influenced by a number of factors
which is required for the reaction to work
- catalase solution - hydrogen peroxide solution
arrange the steps of fatty acid breakdown for cellular respiration
- fatty acids are broken into two-carbon acetyl molecules - CoA is added to the acetyl groups to make acetyl CoA - Acetyl CoA enters the krebs cycle for breakdown
Lab (enzymes)
- higher temperatures increase the rate of interaction of molecules
Lab (enzymes)
- hydrogen peroxide was the catalase - distilled water and catalse = nothing happened - distilled water + hydrogen peroxide = negative control (nothing happened)
which of the following unexpected results could occur if you used the catalase before it had a chance to reach your experimental temp
- in the experiment in which the enzyme was supposed to be boiled, you would get a higher bubble column than expected - in the experiment with cooled enzyme, you would get a higher bubble column than expected
what is the purpose of preparing a tube with water and hydrogen peroxide
- its a negative control experiment - it allows for a measurement with zero mL of catalase
heating up a solution of molecules will result in which of the following
- the molecules will bump into each other with a greater frequency - the molecules will move around faster
which of the following factors affect the rate of a chemical reaction
- the pH in which the enzyme is active - how much substrate is available - the temperature of the reaction - how much enzyme is available
what are the reasons to measure the height of the bubble column exactly 20 seconds after combining the catalase with the hydrogen peroxide
- the timing must be standardized between the tubes - at short or longer times the differences in enzyme concentration might not correlate to bubble height
During glycolysis, what is the net production of ATP per glucose molecule?
2
If oxygen is not present, pyruvate cannot be fully broken down. In this instance, what is the net gain in ATP for each glucose molecule that enters glycolysis
2 ATP
Select the inputs of fermentation
2 phosphate groups, 2 ADP, glucose
What is the efficiency of fermentation in regards to the total possible breakdown of glucose
2.1%
The preparatory reaction, citric acid cycle and the electron transport chain all occur in the presence of oxygen and therefore are _____
Aerobic
•Enzymatic Actions
After the reaction has been completed, the product or products are released, and the active site returns to its original state, ready to bind to another substrate molecule. Only a small amount of enzyme is actually needed in a cell, because enzymes are not used up by the reaction; they merely enable it to happen more quickly.
Flow of Energy
Although energy flows through organisms, chemicals cycle within natural systems. Aerobic organisms utilize the carbohydrate and oxygen produced by chloroplasts to generate energy within the mitochondria to sustain life. Likewise, the carbon dioxide produced by mitochondria returns to chloroplasts to be used in the manufacture of carbohydrates, producing oxygen as a by-product. Therefore, chloroplasts and mitochondria are instrumental in not only allowing a flow of energy through living organisms but also permitting a cycling of chemicals.
The process by which cells make energy using oxygen and the nutrients produced during photosynthesis in order to produce ATP molecules is called
Cellular respiration
Phases of Cellular Respiration
Cellular respiration involves four phases: glycolysis, the preparatory reaction, the citric acid cycle, and the electron transport chain (Fig. 8.2). Glycolysis takes place outside the mitochondria and does not require the presence of oxygen. Therefore, glycolysis is anaerobic. The other phases of cellular respiration take place inside the mitochondria, where oxygen is the final acceptor of electrons. Because they require oxygen, these phases are called aerobic
NAD+ and FAD
Cellular respiration involves many individual metabolic reactions, each one catalyzed by its own enzyme. Enzymes of particular significance are those that use NAD+, a coenzyme of oxidation-reduction (sometimes called a redox coenzyme). When a metabolite is oxidized, NAD+ accepts two electrons plus a hydrogen ion (H+), and NADH results. The electrons received by NAD+ are high-energy electrons that are usually carried to the electron transport chain: NAD+ + 2e- + H+ → NADH
Overview of cellular respiration
Cellular respiration is the process by which cells acquire energy by breaking down nutrient molecules produced by photosynthesizers. Cellular respiration requires oxygen (O2) and gives off carbon dioxide (CO2), which, in effect, is the opposite of photosynthesis In fact, it is the reason any animal, such as an ocelot or a human, breathes (Fig. 8.1) and why plants require a supply of oxygen. This chemical interaction between animals and plants is important, because animals, like humans, breathe the oxygen made by photosynthesizers
The term used to describe the method by which ATP is produced by the flow of H+ from high concentration to low concentration is
Chemiosmosis
The green pigment that absorbs solar energy and is important in algae and plant photosynthesis
Chlorophyll
match each color band with the photosynthetic pigment that corresponds to it
Chlorophyll A: Blue-green Chlorophyll B: Yellow-green Carotenes: yellow-orange Xanthophylls: yellow
The organelle in plant cells that contains chlorophyll and is the site of photosynthesis is the
Chloroplast
Which of the following are produced during cellular respiration; select all that apply
Carbon dioxide, energy (ATP), water
While chlorophyll is the major pigment used in photosynthesis, plants also use yellow and orange accessory pigments called
Carotenoids
Advantages and Disadvantages of Fermentation
Despite its low yield of only two ATP made by substrate-level ATP synthesis, lactic acid fermentation is essential to certain animals and tissues. Typically, animals use lactic acid fermentation for a rapid burst of energy, such as a cheetah chasing a gazelle. Also, when muscles are working vigorously over a short period of time, lactic acid fermentation provides them with ATP, even though oxygen is temporarily in limited supply.
Select the characteristics of fermentation that distinguish it from aerobic respiration
Does not require oxygen, results in the formation of lactate in animal cells, produces a limited amount of ATP
During the production of ATP, H+ ions move ________ a gradient from the intermembrane space into the matric
Down
Light Reactions
During light reactions solar energy is absorbed, water is split so that oxygen is released, and ATP and NADPH are produced. Light reactions only occur when the sun is out and is where solar energy is converted to chemical energy.
which step of cellular respiration produces the most ATP
ETC
Chemiosmosis occurs during which stage of cellular respiration
Electron transport chain
During cellular respiration NAD+ and FAD usually carry high energy electrons to the ____ to produce ATP
Electron transport chain
The first law of thermodynamics states that:
Energy cannot be created or destroyed
Energy
Energy is the ability to do work or bring about change.
Match each phase of cellular respiration to its description below
Glycolysis = occurs outside the mitochondria with or without oxygen present The Prep Reaction = occurs in the matrix of the mitochondria; occurs twice per glucose molecule The Citric Acid Cycle = occurs in the matrix of the mitochondria; produces one ATP per turn The Electron Transport Chain = occurs in the cristae of the mitochondria; carries electrons carried by NADH and FADH2 releasing energy
Select the four phases of cellular respiration
Glycolysis, citric acid cycle, preparatory reaction, electron transport chain
what do protein pumps in the ETC move across the membrane
H+
The oxygen given off by photosynthesis comes from
H2O
The oxygen required by cellular respiration is reduced and becomes part of which molecule?
H2O
which of the following are end products of the ETC
H2O, ATP
•A ribozyme is a biological catalyst that is made of up
RNA
Electron carriers transport both electrons and _______ ions
Hydrogen
what is your strategy for this experiment
I will measure the height of bubbles with different enzyme concentration
what is your strategy
I will measure the height of the bubble column in tubes where the same amount of enzyme is prepared at different temperatures
The Citric Acid Cycle
The citric acid cycle, also called the Krebs cycle, is a cyclical metabolic pathway located in the matrix of mitochondria (Fig. 8.7). At the start of the citric acid cycle, the (C2) acetyl group carried by CoA joins with a C4 molecule, and a C6 citrate molecule results. During the cycle, oxidation occurs when electrons are accepted by NAD+ in three instances and by FAD in one instance. Therefore, three NADH and one FADH2 are formed as a result of one turn of the citric acid cycle. Also, the acetyl group received from the prep reaction is oxidized to two CO2 molecules. Substrate-level ATP synthesis is also an important event of the citric acid cycle. In substrate-level ATP synthesis, you will recall, an enzyme passes a high-energy phosphate to ADP, and ATP results. *picture on page 49 of notes*
Which of these is not true of the citric acid cycle?
The citric acid cycle includes the prep reaction.
Krebs Cycle
The citric acid cycle, also called the Krebs cycle, is a cyclical metabolic pathway located in the matrix of mitochondria
An enzyme reduces the energy necessary to start a chemical reaction. This means that the rate of the reaction will
Increase
•Which of the following is incorrect regarding the active site of an enzyme?
Is not affected by environmental factors, such as pH and temperature
What happens to the end product of glycolysis, pyruvate, if oxygen is not available
It is broken down in the cytoplasm in a process called fermentation
What happens to the amount of enzyme during a chemical reaction
It stays the same
Metabolism
Key metabolic pathways routinely draw from pools of particular substrates needed to synthesize or degrade larger molecules. Substrates like the end product of glycolysis, pyruvate, exist as a pool Page 141that is continuously affected by changes in cellular and environmental conditions (Fig. 8.10). Degradative reactions, termed catabolism, that break down molecules must be dynamically balanced with constructive reactions, or anabolism. For example, catabolic breakdown of fats will occur when insufficient carbohydrate is present; this breakdown adds to the metabolic pool of pyruvate. When energy needs to be stored as fat, pyruvate is taken from the pool. This dynamic balance of catabolism and anabolism is essential to optimal cellular function.
•The sum of all chemical reactions that occur in a cell is called ___
Metabolism
Inside the Mitochondria
Mitochondria Structure & Function *picture on page 47 of notes * Figure 8.6 Mitochondrion structure and function. A mitochondrion is bound by a double membrane with an intermembrane space between the outer and inner membranes. The inner membrane invaginates to form the shelflike cristae.
Mitochondria
Mitochondria are known as the powerhouses of the cell and they oxidize carbohydrates and use the released energy to build ATP molecules
•Substrate Concentration
Molecules must collide to react. Generally, enzyme activity increases as substrate concentration increases, because there are more collisions between substrate molecules and the enzyme. As more substrate molecules fill active sites, more product results per unit of time. But when the active sites are filled almost continuously with substrate, the rate of the reaction can no longer increase. Maximum rate has been reached.
Members of the chain
When NADH gives up its electrons, it becomes oxidized to NAD+, and when FADH2 gives up its electrons, it becomes oxidized to FAD. The next carrier gains the electrons and is reduced. This oxidation-reduction reaction starts the process, and each of the carriers, in turn, becomes reduced and then oxidized as the electrons move down the chain. *picture on page 50 of notes *
which type of substance should travel the shortest distance along the chromatography paper
a substance attracted to cellulose in the paper
•After enzyme-catalyzed reaction has been completed, the product(s) is/are released and the ____ site on the enzyme will return to its original shape
active
•Competitive inhibition occurs when the inhibitor and substrate compete for the ___ site
active
•The location on the enzyme where the substrate binds is called the ___ site
active
the region of an enzyme that binds to its substrate is called
active site
what are you doing to the solution when you blow onto the surface
adding carbon dioxide
the cell respiration pathway that occurs in the mitochondria is
aerobic
ETC and Chemiosmosis
Most ATP is produced by the electron transport chain and chemiosmosis. Per glucose molecule, ten NADH and two FADH2 take electrons to the electron transport chain. For each NADH formed inside the mitochondria by the citric acid cycle, three ATP result, but for each FADH2, only two ATP are produced. Figure 8.8 explains the reason for this difference: FADH2 delivers its electrons to the transport chain after NADH, and therefore these electrons do not participate in as many redox reactions and don't pump as many H+ as NADH. Therefore, FADH2 cannot account for as much ATP production.
Match each coenzyme to its description during the process of cellular respiration
NADH = three ATP results from each of these formed inside the mitochondria FADH2 = two ATP are produced from each of these formed inside the mitochondria
Which of these is not true of fermentation?
NADH donates electrons to the electron transport chain.
___ and FADH2 bring high energy ____ to the electron transport chain. Their energy is used to pump ___ ions (H+) across a membrane. The hydrogen ions flow back across the membrane through an enzyme called ___ ___ which powers it to build ATP
NADH; electrons; hydrogen; ATP synthase
The final acceptor of electrons during the light reactions of the noncyclic electron pathway is
NADP+.
Which of the following are the products of the light reactions that then serve as reactants for the calvin cycle
NADPH and ATP
Because 2 ATP are used to "just-start" glycolysis, when the number of ATP produced overall is discussed, it is referred to as a ____ gain in ATP
NET
•During noncompetitive inhibition, the inhibitor will bind to the ___ site
allosteric
The citric acid cycle
also takes place in the matrix of the mitochondrion. Each 2-carbon acetyl group matches up with a 4-carbon molecule, forming two 6-carbon citrate molecules. As citrate bonds are broken and oxidation occurs, NADH and FADH2 are formed, and two CO2 per citrate are released. The citric acid cycle is able to produce one ATP per turn. Because two acetyl groups enter the cycle per glucose molecule, the cycle turns twice.
Lab (enzymes)
an enzyme converts substrate to product most quickly at optimum pH
___ respiration occurs when no ___ is available for aerobic respiration
anaerobic; oxygen
Calvin Cycle Reactions
are named for Melvin Calvin, who in 1961 received a Nobel Prize in Chemistry for discovering the enzymatic reactions that reduce carbon dioxide to a carbohydrate in the stroma of chloroplasts The enzymes that speed the reduction of carbon dioxide during both day and night are located in the semifluid substance of the chloroplast stroma.
exergonic reactions
are spontaneous reactions that release energy
prodcuts
are substances that form as a result of a reaction
reactants
are substances that participate in a reaction
___ are able to produce their own organic molecules for energy, but __ must obtain organic molecules for energy from other organisms
autotrophs; heterotrophs
Second Law of Thermodynamics
Every time energy is transferred from one form to another, some of it is lost as heat.
In vertebrates, the carbon dioxide produced during the prep reaction is eventually ___
Exhaled
Why does denaturation prevent an enzyme from being able to catalyze its reaction
Denaturation changes the shape of the enzyme's active site so that it cannot bind correctly with its substrate
to determine the activity of an enzyme, you can compare the concentration of the enzyme before and after the chemical reaction
False
The anaerobic process that proceeds when oxygen is not available for cellular respiration is called
Fermentation
Summary ** page 21 of notes **
Figure 7.6 summarizes our discussion so far and shows that during the light reactions, (1) solar energy is absorbed, (2) water is split so that oxygen is released, and (3) ATP and NADPH are produced.
3PG, BPG and G3P are similar 3-carbon molecules. Which of these molecules produced during the calvin cycle is reduced, is more chemically able to store energy, and can form larger organic molecules such as glucose
G3P
The product of the calvin cycle and the first reactant in many metabolic reactions sin a plant cell is
G3P
The importance of the Calvin Cycle
G3P is the product of the Calvin cycle that can be converted to other molecules a plant needs. Notice that glucose phosphate is among the organic molecules that result from G3P metabolism (Fig. 7.13). This is of interest to us because glucose is the molecule that plants and animals most often metabolize to produce the ATP molecules they require for their energy needs.
Glycolysis is the breakdown of the sugar named
Glucose
Match each molecule to its description during the process of glycolysis
Glucose = broken down into two 3-carbon pyruvate molecules Pyruvate = 3-carbon molecule; two are produced from each glucose molecule broken down NADH = formed from the oxidation of glucose 4 ATP = produced as a result of the oxidation of glucose 2 ATP = used during the process
Match the carbohydrate on the left to the correct function in plants on the right
Glucose = substrate for ATP Sucrose = energy transport Cellulose = cell wall structure Starch = energy storage
The production of all plant carbohydrates begins with the formation of
Glucose and G3P
G3P is the product of the calvin cycle and the first reactant in many metabolic reactions in a plant cell leading to production of which other molecules
Glucose phosphate, sucrose, fatty acids, amino acids
Which stage of cellular respiration breaks down glucose into two 3-carbon pyruvate molecules and also produces two ATP
Glycolysis
Outside the Mitochondria: Glycolysis
Glycolysis takes place within the cytoplasm outside the mitochondria, is the breakdown of C6 (6-carbon) glucose to two C3 (3-carbon) pyruvate molecules. Since glycolysis occurs universally in organisms, it most likely evolved before the citric acid cycle and the electron transport chain. This may be why glycolysis occurs in the cytoplasm and does not require oxygen. There was no free oxygen in Earth's early atmosphere. Glycolysis is a series of ten reactions, and just as you would expect for a metabolic pathway, each step has its own enzyme. The pathway can be conveniently divided into the energy-investment step and the energy-harvesting steps. During the energy-investment step, ATP is used to "jump-start" glycolysis. During the energy-harvesting steps, four total ATP are made, producing two net ATP overall.
most G3P produced during photosynthesis is broken down through the process of __ __ to produce energy for a plants cell
cellular respiration
most G3P produced from photosynthesis is broken down into __ __ to power cells
cellular respiration
in this experiment, what does a change in the volume of gas in a volumeter indicate
cellular respiration is occuring
__ __ is the process organisms use to transfer energy from ___ to ATP
cellular respiration; glucose
glucose created during photosynthesis can be used to build two polysaccharides. the first is __ which is used for cell walls. the second is __ which is used for energy storage
cellulose; starch
what causes the movement of manometer fluid in the control vial
changes in barometric pressure
potential energy for living organisms is stored in ___ bonds
chemical
which cell organelle is the site of photosynthesis
chloroplast
•The process of photosynthesis occurs in organelles called
chloroplasts
what is added to the 2-carbon acetyl during pyruvate oxidation
coenzyme A
•The substance that can help to increase the rate of an enzymatic reaction by helping a substrate bind to the active site is called a ___-
cofactor
Chemiosmosis
depends on complexes in the thylakoid membrane. depends on an electrochemical gradient. depends on a difference in H+ concentration between the thylakoid space and the stroma. results in ATP formation. All of these are correct.****
photopigments differ from each other in what way
each absorbs light most efficiently at different wavelenghts
during cellular respiration, NADH & FADH2 harvest high energy ___ from ___and deliver them to the last step of cellular respiration called the __ __ __
electrons; glucose; ETC
reactions that require energy are called __ reactions
endergonic
reactions that require energy are ____ and reactions that release energy are ____
endergonic; exergonic
reduction reactions are _______ and oxidation reactions are ___
endergonic; exergonic
Cells need ___ to do work
energy
when a photon of light hits an electron, the electron jumps to a higher ___ level
energy
living organisms require a constant input of _____ to maintain ______
energy homeostasis
•The overall equation for photosynthesis can be written like this:
energy + carbon dioxide + water --> glucose + oxygen •This equation shows that during photosynthesis, hydrogen atoms are transferred from water to carbon dioxide to form glucose •In this reaction, therefore, carbon dioxide has been reduced and water has been oxidized. It takes energy to reduce carbon dioxide to glucose, and this energy is supplied by solar energy. Chloroplasts are able to capture solar energy and convert it to the chemical energy of ATP, which is used along with hydrogen atoms to reduce carbon dioxide. Oxygen is a by-product that is released
the opposite of homeostasis is
entropy
•The presence of a particular ___ determines the rate of metabolism as well as which product is produced
enzyme
a graph constructed to show the relationship between enzyme concentration and enzyme activity would have ___ plotted on the x-axis and ____ plotted on the y-axis
enzyme concentration / bubble column height
___ are molecules that catalyze reactions in living organisms
enzymes
•Protein molecules that catalyze chemical reactions in cells are called
enzymes
___ act on a ___ to create a ___
enzymes; substrate; product
Anaerobic respiration produces more energy than aerobic respiration
false
NADPH and ATP cycle between the Calvin cycle and the light reactions constantly. _______
false
True or false: plants are the only organisms that are autotrophs
false
True or false: the flow of water molecules fuels the synthesis of ATP
false
any enzyme can bond to many different types of substrates (T/F)
false
when an enzyme speeds up a chemical reaction, it is consumes in the process
false
when the enzyme catalase is mixed with water, oxygen bubbles are produced
false
why are the respirometers incubated at 37 degrees C in this experiment instead of a cooler temp
fermentation occurs faster at warmer temps
what would happen if you let the respirometers incubate at room temp instead of 37 degrees C
fermentation would still occur, but more slowly
which carbohydrate is the primary or preferred starting compound for glycolysis and the fermentation pathway
glucose
which sugar is most readily used in fermentation by yeasts in this experiment
glucose
•During energy transformations, the majority of energy is converted to
heat
what do NADH and FADH2 bring to the electron transport chain
high energy electrons
if enough substrate is present, adding more enzyme to a reaction mixture will ____ the rate of product formation
increase
•Increasing the temperature of a reaction toward an enzyme's optimal temperature would ___ the rate of an enzymatic reaction
increase
what is your hypothesis for this experiment
increasing enzyme concentration increases the reaction rate
what is your hypothesis for this experiment
increasing temp will increase the reaction rate, up to a certain temp
Electron Transport Chain
is a series of carriers on the cristae of the mitochondria
The electron transport chain (ETC)
is a series of carriers on the cristae of the mitochondria. NADH and FADH2 give up their high-energy electrons to the chain. Energy is released and captured as the electrons move from a higher-energy to a lower-energy state during each redox reaction. Later, this energy is used for the production of between 32 and 34 ATP by chemiosmosis. After oxygen receives electrons at the end of the chain, it combines with hydrogen ions (H+) and becomes water (H2O).
CAM photosynthesis.
is prevalent in desert plants that close their stomata during the day.
potential
is stored energy whose capacity to accomplish work is not being used at the moment. The food we eat has potential energy because the energy stored in chemical bonds can be converted into various types of kinetic energy Food is a form of chemical energy because it is composed of organic molecules, such as carbohydrates, proteins, and fat.
energy
is the ability to do work or bring about change
Glycolysis
is the breakdown of glucose (a 6-carbon molecule) to two molecules of pyruvate (two 3-carbon molecules). Oxidation results in NADH and provides enough energy for the net gain of two ATP molecules.
what is the function of potassium hydroxide in this experiment
it absorbs CO2 so only O2 affects the volume
when photosynthesis is occurring, what should happen to the amount of carbon dioxide in the solution
it decreases
why is phenol red used in this experiment
it indicates approximate pH
which of the following is true about the color of a photopigment
it is the color of the light it does not absorb
why doesn't vial 3 contain soybeans
it is the control
how does carbon dioxide cause phenol red to turn yellow
it reacts with water to form a weak acid
which of the following is not true regarding an enzyme at cold temp
it will bind with substrate more frequently
if you have a constant amount of substrate, and add an increasing concentration of enzyme, what will happen to the reaction rate
it will increase
what is the purpose of preparing a tube with water and hydrogen peroxide
its a negative control experiment
two forms of energy are
kinetic potential
what is the final product of anaerobic respiration of animal cells
lactic acid
enzymes below their optimum temp will show __ activity
less
at higher temperatures molecules move ___ rapidly
more
increasing the concentration of enzyme at the beginning of the experiment results in ____ substrate interacting with the enzyme per unit of time
more
All of the following are examples of organisms that can photosynthesize EXCEPT
mushrooms
C4 Photosynthesis
n a C3 plant, the mesophyll cells contain well-formed chloroplasts and are arranged in parallel layers (Fig. 7.15). In a C4 leaf, the bundle sheath cells, as well as the mesophyll cells, contain chloroplasts. Further, the mesophyll cells are arranged concentrically around the bundle sheath cells. C4 plants fix CO2 to PEP (phosphoenolpyruvate, a C3 molecule) using the enzyme PEP carboxylase (PEPCase). The result is oxaloacetate, a C4 molecule: PEP +CO2 --(PEPCase)--> Oxaloacetate In a C4 plant, CO2 is taken up in mesophyll cells, and then malate, a reduced form of oxaloacetate, is pumped into the bundle sheath cells (Fig. 7.16). Only here does CO2 enter the Calvin cycle. Because it takes energy to pump molecules, you would think that the C4 pathway would be disadvantageous. Yet in hot, dry climates, the net photosynthetic rate of C4 plants, such as sugarcane, corn, and Bermuda grass, is about two to three times that of C3 plants (e.g., wheat, rice, and oats). Why do C4 plants enjoy such an advantage? The answer is that they can avoid photorespiration, discussed previously. Photorespiration is wasteful, because it is not part of the Calvin cycle. Photorespiration does not occur in C4 leaves because PEPCase, unlike RuBP carboxylase, does not combine with O2. Even when stomata are closed, CO2 is delivered to the Calvin cycle in the bundle sheath cells.
___ is the loss of electrons and ___ is the gain of electrons
oxidation; reduction
in living organisms, glucose is ____ to release energy that powers chemical reactions
oxidized
aerobic respiration requires which of the following
oxygen
metabolic processes like germination require energy in the form of ATP which is produced by cellular respiration. which gas is consumed by germinating beans to produce the ATP required
oxygen
what is the final electron acceptor in the electron transport chain
oxygen
how is oxygen concentration in the test tube related to cellular respiration in the beans
oxygen is consumed when cellular respiration is occuring
if you add more catalse (enzyme) to an excess amount of hydrogen peroxide (substrate)
oxygen will be produced faster
___ creates sugars using __ __, water, and __ from the sun
photosynthesis; carbon dioxide; energy
The Calvin cycle reactions
produce carbohydrate. convert one form of chemical energy into a different form of chemical energy. regenerate more RuBP. use the products of the light reactions. ALL OF THESE ARE CORRECT*
which of the following describe the calvin cycle of photosynthesis
produces carbohydrates, requires carbon dioxide, uses ATP and NADPH
which of the following describe light reactions of photosynthesis
produces oxygen, electron transport chain, capture sun energy, requires water, creates ATP and NADPH
when an enzyme is at its optimum pH
product is formed at the fastest rate
The two outer membranes of the chloroplast enclose a gelatinous matrix called the
stroma
•The reactants in an enzymatic reaction that binds to the active site of the enzyme is called a
substrate
at refrigerator temp catalase is expected to produce a few bubbles of oxygen. why is this
substrate molecules move more slowly and interact with the active site less frequently
which of the following carbohydrates is a dissacharide
sucrose
which sugar must first be broken down into two simple sugars before fermentation can take place
sucrose
The ultimate energy to fuel the process of photosynthesis comes from the ___
sun
all energy in living organisms originally comes from the __
sun
the thylakoid membrain is embedded with photosystems where clusters of chlorophyll capture ___ energy
sun
what is the original source for all energy in living organisms
sun
photosynthesis converts __ energy to __ energy
sun; chemical
increasing the concentration of hydrogen peroxide will increase the reaction rate of catalase if which of the following is the case
the concentration of the substrate is limiting the rate
The role of NADP+ / NADPH
the electrons needed to reduce carbon dioxide are carried by a coenzyme. NADP+ is the coenzyme of oxidation-reduction (redox coenzyme) active during photosynthesis When NADP+ is reduced, it has accepted two electrons and one hydrogen atom, and when NADPH is oxidized, it gives up its electrons: NADP+ + 2c- + H+ → NADPH Photosynthesis releases oxygen
kinetic
the energy of motion, as when water flows over a waterfall, a ball rolls down a hill, or a moose walks through grass When a moose walks, it converts chemical energy into a type of kinetic energy called mechanical energy
which substance in a chemical reaction will not change in concentration as the reaction proceeds
the enzyme
how does the volume of gas relate to the rate of cell respiration occurring in each of the volumeters
the faster the oxygen consumption, the greater the rate of cellular respiration
why are polyester fluffs used
the protect the seeds from touching the KOH because they do not soak it up
using the respirometer, how can you determine which carbohydrate is used most efficiently by yeast fermentation
the solution in the tube with the largest gas bubble has fermented most efficiently
how do you know the amount of carbon dioxide in the solution is decreasing
the solution turns pinkish-red
how will you know if one sugar is fermented more easily than another
the space in the top of the small tube will increase in volume more quickly
imagine three test tubes containing a constant amount of substrate but increasing amounts of enzyme. after ten minutes, which tube will show the highest column of bubbles
the tube with the largest enzyme concentration
how does the rate of oxygen uptake relate to the metabolic activity occurring in each volumeter
the volumeter with the greatest volume change indicates the greatest metabolic activity
why did the different photopigments migrate to different points on the chromatography paper
they differ in their solubility and affinity for the solvent and the paper
where do light reactions occur within the chloroplast
thylakoid membrane
why are movements in the manometer fluid in the control vial important to measure
to correct values in the experimental vials
phenol red turns ___ in acidic solutions and ___ in basic solutions
yellow;r ed
label the diagram (picture on page 13 of notes)
•A = substrate •B = products •C = recycled enzyme •D = enzyme substrate complex •E = enzyme before the reaction
Metabolic Pathway
•A is the substrate for E1, and B is the product. Now B becomes the substrate for E2, and C is the product. This process continues until the final product, D, forms. Any one of the molecules (A-D) in this metabolic pathway could also be a reactant in another pathway. Many of the metabolic pathways in living organisms are highly branched, and interactions between metabolic pathways are very common. It is important to note that each step in the metabolic pathway can be regulated because each step requires an enzyme • The specificity of enzymes allows the regulation of metabolism. The presence of particular enzymes helps determine which metabolic pathways are operative. In addition, some substrates can produce more than one type of product, depending on which pathway is open to them. Therefore, which enzyme is present determines which product is produced, as well as determining the direction of metabolism, without several alternative pathways being activated. As we will see, the ability to regulate these pathways gives our cells fine control over how they respond in a changing environment and helps maximize cell efficiency. Picture on 6 of notes
Structures of ATP
•ATP is a nucleotide composed of the nitrogen-containing base adenine and the 5-carbon sugar ribose (together called adenosine), and three phosphate groups. •The three phosphate groups of ATP repel each other, creating instability and potential energy •ATP is called a "high-energy" molecule, because a phosphate group can be easily removed •Under cellular conditions, the amount of energy released when ATP is hydrolyzed to ADP + Ⓟ is about 7.3 kcal per mole •A mole is a unit of measurement in chemistry that is equal to the molecular weight of a molecule expressed in grams.
ATP: Energy for Cells
•ATP is the common energy currency of cells; when cells require energy; they use ATP •A sedentary oak tree, a flying bat, and a human require vast amounts of ATP. The more active the organism, the greater the demand for ATP. However, cells do not keep a large store of ATP molecules on hand. •Instead, they constantly regenerate ATP using ADP (adenosine diphosphate) and inorganic cellular respiration this is called the ATP CYCLE
•An ATP molecule consists of a nitrogen-containing base called ___, a 5 carbon sugar called ____, and three ____ groups
•Adenine / Ribose / Phosphate
•Exergonic reactions
•Are spontaneous, have a negative delta G value, and release energy
•The reactants of a photosynthetic reaction are
•Carbon dioxide •Water
•Optimal pH
•Each enzyme also has an optimal pH at which the reaction rate is highest •The figure below shows the optimal pH for the enzymes pepsin and trypsin. At their respective pH values, each enzyme can maintain its normal structural configuration, which enables optimum function The globular structure of an enzyme is dependent on interactions, such as hydrogen bonding, between R groups. A change in pH can alter the ionization of these side chains, causing the enzyme to denature. Under extreme conditions of pH, the enzyme changes its structure and becomes inactive.
•The amount of energy that is needed to start a chemical reaction between molecules is called a
•Energy of activation
why does this experiment use distilled water instead of 3% sodium bicarbonate solution
because the pH of distilled water changes with CO2 content
energy is found in the __ or organic molecules
bonds
based on your results in this experiment, catalase has a pH optimum of
7
different wavelengths of light ___
have different colors
Identify the Structures of the Mitochondria
* picture on page 53 of notes * A = outer membrane B = inner membrane C = intermembrane space D = cristae E = matrix
Energy Yield from Glucose Metabolism
* picture on page 53 of notes* Figure 8.9 Accounting of energy yield per glucose molecule breakdown. Substrate-level ATP synthesis during glycolysis and the citric acid cycle accounts for four ATP. The electron transport chain accounts for 32 or 34 ATP, making the theoretical grand total of ATP between 36 and 38 ATP. Other factors may reduce the efficiency of cellular respiration. For example, cells differ as to the delivery of the electrons from NADH generated outside the mitochondria. If they are delivered by a shuttle mechanism to the start of the electron transport chain, six ATP result; otherwise, four ATP result.
Metabolic pool concept
* picture on page 56 of notes *
Which of the following are true of an enzyme-catalyzed reaction
- An enzyme speeds up the conversion of substrate to product - enzymes are not used up in the chemical reaction - an enzyme reduces the activation energy
arrange the steps an electron follows during the electron transport chain
- NADH and FADH2 deliver electrons to pump that used the energy to pump H+ across a membrane - The electrons are passed along a series of more pumps - The used electrons bond with oxygen and hydrogen to form water
complete the formula for photosynthesis
6 CO2 + 6 H2O --> C6H12O6 + 6 O2
Provide the correct reactant to complete this chemical equation: C6H12O6 + _____ → 6CO2 + 6H2O + 36ATP
6 O2
During the energy-harvesting step of glycolysis, a total of ____ molecules of ATP are assembled
4
Why is the net ATP production from one molecule of glucose undergoing substrate level phosphorylation during cellular respiration
4
During cellular respiration, how many molecules of CO2 will be produced from one molecule of glucose
6
Leaves and Photosynthesis
A double membrane surrounds a chloroplast, and its semifluid interior is called the stroma A different membrane system within the stroma forms flattened sacs called thylakoids, which in some places are stacked to form grana The thylakoid membrane contains chlorophyll and other pigments that are capable of absorbing the solar energy that drives photosynthesis. The stroma contains an enzyme-rich solution, where carbon dioxide is first attached to an organic compound and then reduced to a carbohydrate. Humans and other respiring organisms release carbon dioxide into the air. Some of the same carbon dioxide molecules enter a leaf through the stoma and are converted to carbohydrate. Carbohydrate, in the form of glucose, is the chief source of chemical energy for most organisms. Thus, an interdependent relationship exists between organisms that make their own food (autotrophs) and those that consume their food (heterotrophs)
Select the components of a photosystem from the choices below
A pigment complex and an electron acceptor
Pigment
A pigment is a substance that appears a certain color because it selectively absorbs wavelengths of light.
An autotrophic organism is best described as an organisms that
Can capture energy and synthesize organic molecules from inorganic nutrients
Step 1: Fixation of the Carbon Dioxide
Carbon dioxide fixation is the first step of the Calvin cycle. During this reaction, a molecule of carbon dioxide from the atmosphere is attached to RuBP (ribulose-1,5-bisphosphate), a 5-carbon molecule. The result is one 6-carbon molecule, which splits into two 3-carbon molecules. The enzyme that speeds this reaction, called RuBP carboxylase, is a protein that makes up about 20-50% of the protein content of chloroplasts. The reason for its abundance may be that it is unusually slow—it processes only a few molecules of substrate per second compared to thousands per second for a typical enzyme—so there has to be a lot of it to keep the Calvin cycle going.
Outside the Mitochondria: Fermentation
Complete glucose breakdown requires an input of oxygen to keep the electron transport chain working. So how does the cell produce energy if oxygen is limited? Fermentation is an anaerobic process that produces a limited amount of ATP in the absence of oxygen. In animal cells, including human cells, pyruvate, the end product of glycolysis, is reduced by NADH to lactate (Fig. 8.5). Depending on their particular enzymes, bacteria vary as to whether they produce an organic acid, such as lactate, or an alcohol and CO2. Yeasts are good examples of organisms that generate ethyl alcohol and CO2 as a result of fermentation. Fermentation Why is it beneficial for pyruvate to be reduced when oxygen is not available? Because the cell still needs energy when oxygen is absent. The fermentation reaction regenerates NAD+, which is required for the first step in the energy-harvesting phase of glycolysis. This NAD+ is now "free" to return to the earlier reaction (see return arrow in Fig. 8.5) and become reduced once more. Although this process generates much less ATP than when oxygen is present and glucose is fully metabolized into CO2 and H2O in the ETC, glycolysis and substrate-level ATP synthesis produce enough energy for the cell to continue working.
Photosynthesis
Converts solar energy into the chemical energy of a carbohydrate. Organisms use sunlight to synthesize foods from carbon dioxide and water.
Calvin Cycle
Melvin Calvin discovered that enzymatic reactions that reduce carbon dioxide to a carbohydrate in the stroma of chloroplasts. It is a set of chemical reactions that take place in chloroplasts during photosynthesis.
Organisms that cannot synthesize organic compounds from inorganic substances and therefore must take in organic molecules (food) are
Heterotrophs
When electrons move through an electron transport chain, they move from a __ to a _____ energy level
Higher to lower
•Enzyme Cofactors and Coenzymes
Many enzymes require the presence of an inorganic ion or a nonprotein organic molecule at the active site in order to work properly; these necessary ions or molecules are called cofactors •The inorganic ions include metals such as copper, zinc, or iron. The nonprotein organic molecules are called coenzymes •These cofactors participate in the reaction and may even accept or contribute atoms to the reactions. Examples of these are NAD+ (nicotinamide adenine dinucleotide), FAD (flavin adenine dinucleotide), and NADP+ (nicotinamide adenine dinucleotide phosphate), each of which plays a significant role in either cellular respiration or photosynthesis •Vitamins are often components of coenzymes Vitamins are relatively small, organic molecules that are required in trace amounts in our diet and in the diets of other animals for synthesis of coenzymes. The vitamin becomes part of a coenzyme's molecular structure. For example, the vitamin niacin is part of the coenzyme NAD+ and riboflavin (B2) is a component of the coenzyme FAD. If a vitamin is not available, enzymatic activity will decrease, and the result will be a vitamin-deficiency disorder. In humans, a niacin deficiency results in a skin disease called pellagra, and riboflavin deficiency results in cracks at the corners of the mouth.
Electron Flow in the Light Reactions
Noncyclic pathway: electrons move from water to NADP+ Energized electrons (replaced from water, which splits, releasing oxygen) leave photosystem II and pass down an electron transport chain, leading to the formation of ATP. Energized electrons (replaced by photosystem II by way of the ETC) leave photosystem I and pass to NADP+, which then combines with H+, becoming NADPH. An electron acceptor sends energized electrons, received from the reaction center, down an electron transport chain (ETC), a series of carriers that pass electrons from one to the other. As the electrons pass from one carrier to the next, energy is captured and stored in the form of a hydrogen ion (H+) gradient. When these hydrogen ions flow down their electrochemical gradient through ATP synthase complexes, ATP production occurs. Notice that this ATP is then used by the Calvin cycle reactions in the stroma to reduce carbon dioxide to a carbohydrate When the PS I pigment complex absorbs solar energy, energized electrons leave its reaction center and are captured by electron acceptors. (Low-energy electrons from the electron transport chain adjacent to PS II replace those lost by PS I.) The electron acceptors in PS I pass their electrons to NADP+ molecules. Each NADP+ accepts two electrons and an H+ to become reduced and forms NADPH. This NADPH is then used by the Calvin cycle reactions in the stroma along with ATP in the reduction of carbon dioxide to a carbohydrate.
Step 3: Regeneration of RuBP
Notice that the Calvin cycle reactions in Figure 7.12 are multiplied by 3 because it takes three turns of the Calvin cycle to allow one G3P to exit. Why? For every three turns of the Calvin cycle, five molecules of G3P are used to re-form three molecules of RuBP, and the cycle continues. Notice that 5 × 3 (carbons in G3P) = 3 × 5 (carbons in RuBP)
Energy-Harvesting Steps
Oxidation of G3P now occurs by the removal of electrons accompanied by hydrogen ions. In duplicate reactions, electrons are picked up by coenzyme NAD+, which becomes: When O2 is available, each NADH molecule carries two high-energy electrons to the electron transport chain and becomes NAD+ again. In this way, NAD+ is recycled and used again. The addition of inorganic phosphate results in a high-energy phosphate group on each C3 molecule. These phosphate groups are used to directly synthesize two ATP in the later steps of glycolysis. This is called substrate-level ATP synthesis, also called substrate-level phosphorylation, because an enzyme passes a high-energy phosphate to ADP, and ATP results (Fig. 8.3). Notice that this is an example of a coupled reaction: An energy-releasing reaction is driving forward an energy-requiring reaction on the surface of the enzyme.
Organization of the Thylakoid Membrane
PS II, which consists of a pigment complex and electron acceptor molecules, receives electrons from water as water splits, releasing oxygen. The electron transport chain (ETC), consisting of Pq (plastoquinone) and cytochrome complexes, carries electrons from PS II to PS I via redox reactions. Pq also pumps H+ from the stroma into the thylakoid space. PS I, which also consists of a pigment complex and electron acceptor molecules, is adjacent to NADP reductase, which reduces NADP+ to NADPH. The ATP synthase complex, which has a channel and a protruding ATP synthase, is an enzyme that joins ADP + Ⓟ.
Substrate-Level ATP Synthesis
Per glucose molecule, there is a net gain of two ATP from glycolysis, which takes place in the cytoplasm. The citric acid cycle, which occurs in the matrix of mitochondria, accounts for two ATP per glucose molecule. This means that a total of four ATP are formed by substrate-level ATP synthesis outside the electron transport chain.
Photosynthesis
Photosynthesis converts solar energy into the chemical energy of a carbohydrate. Photosynthetic organisms, including plants, algae and cyanobacteria, and called autotrophs because they produce their own food It has been estimated that all of the world's green organisms together produce between 100 billion and 200 billion metric tons of sugar each year. Imagine enough sugar cubes to re-create the volume of 2 million Empire State Buildings! No wonder photosynthetic organisms are able to sustain themselves and all other living organisms on Earth. With few exceptions, it is possible to trace any food chain back to plants and algae In other words, producers, which have the ability to synthesize carbohydrates, feed not only themselves but also consumers, which must take in preformed organic molecules Heterotrophs are called consumers Both autotrophs and heterotrophs use organic molecules produced by photosynthesis as a source of building blocks for growth and repair and as a source of chemical energy for cellular work.
Which of these is a molecular complex that uses light energy to reduce NADP+ to NADPH
Photosystem l
Which of these is a molecular complex that uses light energy to oxidize water molecules, releasing oxygen
Photosystem ll
Pigments and Photosystems
Pigment molecules absorb wavelengths of light. Most pigments absorb only some wavelengths; they reflect or transmit the other wavelengths. The pigments in chloroplasts are capable of absorbing various portions of visible light. This is called their absorption spectrum. Photosynthetic organisms differ in the type of chlorophyll they contain. In plants, chlorophyll a and chlorophyll b play prominent roles in photosynthesis Cartenoids play an accessory role. Both chlorophylls a and b absorb violet, blue, and red light better than the light of other colors. Because green light is transmitted and reflected by chlorophyll, plant leaves appear green to us. In short, plants are green because they do not use the green wavelength! The carotenoids, which are shades of yellow and orange, are able to absorb light in the violet-blue-green range. These pigments become noticeable in the fall when chlorophyll breaks down.
During the preparatory reaction of cellular respiration, a 3-carbon molecule called ___ is converted into acetyl-CoA
Pyruvate
Select the products of glycolysis
Pyruvate (pyruvic acid), NADH, ATP
In photosynthesis, the reaction that begins with CO2 and ends with CH2O is a(n) ____ reaction
Reduction
Which of the following are examples of heterotrophic organisms
Reindeer & Rabbit
The major inputs of the light reactions of photosynthesis include
Solar energy, ADP, H2O, NADP+
During glycolysis, ATP is produced by
Substrate-level ATP synthesis (phosphorylation)
living organisms follow the first law of thermodynamics by converting ___ energy into chemical energy in the form of __
Sun Glucose
RuBP carboxylase is the enzyme that fixes carbon dioxide to RuBP in the Calvin cycle. _______
TRUE
Plants fix Carbon Dioxide
The Calvin cycle is a series of reactions that can occur in the dark, but it uses the products of the light reactions to reduce carbon dioxide captured from the atmosphere to a carbohydrate. The Calvin cycle has three steps: (1) carbon dioxide fixation, (2) carbon dioxide reduction, and (3) regeneration of RuBP
Cycling of Carriers
The ETC Pumps Hydrogen Ions. Essentially, the electron transport chain consists of three protein complexes and two carriers. The three protein complexes are the NADH-Q reductase complex, the cytochrome reductase complex, and the cytochrome oxidase complex. The two other carriers that transport electrons between the complexes are coenzyme Q and cytochrome c (Fig. 8.8). We have already seen that the members of the electron transport chain accept electrons, which they pass from one to the other via redox reactions. So what happens to the hydrogen ions (H+) carried by NADH and FADH2? The complexes of the electron transport chain use the energy released during redox reactions to pump these hydrogen ions from the matrix into the intermembrane space of a mitochondrion. The ATP Synthase Complex Produces ATP. The ATP synthase complex can be likened to the gates of a dam. When the gates of a hydroelectric dam are opened, water rushes through, and electricity (energy) is produced. Similarly, when H+ flows down a gradient from the intermembrane space into the matrix, the enzyme ATP synthase synthesizes ATP from ADP + Ⓟ. This process is called chemiosmosis, because ATP production is tied to the establishment of an H+ gradient. Active Tissues Contain More Mitochondria. Active tissues, such as muscles, require greater amounts of ATP and have more mitochondria than less active cells. When a burst of energy is required, however, muscles still utilize fermentation.
Electron Transport Chain
The electron transport chain (ETC) located in the cristae of the mitochondria and the plasma membrane of aerobic prokaryotes, is a series of carriers that pass electrons from one to the other. The high-energy electrons that enter the electron transport chain are carried by NADH and FADH2. Figure 8.8 is arranged to show that high-energy electrons enter the chain and low-energy electrons leave the chain. *pictures on page 50-51 of notes *
Which of these is not true of the electron transport chain?
The electron transport chain produces more NADH than any metabolic pathway.
The Energy Organelles Revisited
The equation for photosynthesis in a chloroplast is opposite that of cellular respiration in a mitochondrion: Energy + 6 CO2 + 6 H2O ←photosynthesis&Cell. Respiration-> C6H12O6 + 6 O2 While you were studying photosynthesis and cellular respiration, you may have noticed a remarkable similarity in the structural organization of chloroplasts and mitochondria. Through evolution, all organisms are related, and the similar organization of these organelles suggests that they may be related also. The two organelles carry out related but opposite processes (Fig. 8.11): Use of membrane. In a chloroplast, an inner membrane forms the thylakoids of the grana. In a mitochondrion, an inner membrane forms the convoluted cristae. Electron transport chain (ETC). An ETC is located on the thylakoid membrane of chloroplasts and the cristae of mitochondria. In chloroplasts, the electrons passed down the ETC have been energized by the sun; in mitochondria, energized electrons have been removed from glucose and glucose products. In both, the ETC establishes an electrochemical gradient of H+ with subsequent ATP production by chemiosmosis. Enzymes. In a chloroplast the stroma contains the enzymes of the Calvin cycle, and in mitochondria the matrix contains the enzymes of the citric acid cycle. In the Calvin cycle, NADPH and ATP are used to reduce carbon dioxide to a carbohydrate. In the citric acid cycle, the oxidation of glucose products produces NADH and ATP.
RuBP carboxylase is an enzyme found in chloroplasts and is also
The first enzyme in the calvin cycle
Chlorophyll
The green pigment that absorbs solar energy and is important in algae and plant photosynthesis.
Other types of Photosynthesis
The majority of plants, such as azaleas, maples, and tulips, carry on photosynthesis as described in Section 7.2 and are called C3 plants. C3 plants use the enzyme RuBP carboxylase to fix CO2 to RuBP in mesophyll (photosynthetic) cells. The first detected molecule following fixation is the 3-carbon molecule 3PG: RuBP + CO2 ___(RuBP carboxylase)--> 2 3PG As shown in Figure 7.2, leaves have small openings called stomata, through which water can leave and carbon dioxide (CO2) can enter. If the weather is hot and dry, the stomata close, conserving water. (Water loss might cause the plant to wilt and die.) Now the concentration of CO2 decreases in leaves, while O2, a by-product of photosynthesis, increases. When O2 rises in C3 plants, RuBP carboxylase combines it with RuBP instead of CO2. The result is one molecule of 3PG and the eventual release of CO2. This is called photorespiration, because in the presence of light (photo), oxygen is taken up and CO2 is released (respiration). *picture on page 32 of notes
Bio Now: Energy Part II-Photosynthesis What is the overall goal of this experiment?
The overall goal of this experiment is to build a human powered growth chamber in order to grow organic beets. The human powered growth chamber that was built is put to work by pedalling which runs a generator that sends energy to the battery and then the battery runs lights inside the box where there are plants growing. This specific part of the experiment is figuring out how to grow the plants and then how to get them to photosynthesize. The end goal overall is to complete the human powered growth chamber so sugar beets can grow inside. Before this part of the experiment, all that we managed to do is create the setup to transfer our energy into light energy. But since we have light we can now grow plants because they need light to perform photosynthesis.
The process of photosynthesis
The overall process of photosynthesis can be represented by an equation: 6 CO2 + 12 H2O ---(solar energy)--> 6 (CH2O) + 6 H2O + 6 O2 In this equation, (CH2O) represents carbohydrate. If the equation were multiplied by 6, the carbohydrate would be C6H12O6, or glucose.
The preparatory Reaction
The preparatory (prep) reaction is so called because it converts products from glycolysis into products that enter the citric acid cycle. In this reaction, the C3 pyruvate is converted to a C2 acetyl group and CO2 is given off. This is an oxidation reaction in which electrons are removed from pyruvate by NAD+ and NADH is formed. One prep reaction occurs per pyruvate, so the prep reaction occurs twice per glucose molecule: *picture on page 48 of notes* The C2 acetyl group is combined with a molecule known as CoA. CoA will carry the acetyl group to the citric acid cycle in the mitochondrial matrix. The two NADH carry electrons to the electron transport chain. What about the CO2? In vertebrates, such as ourselves, CO2 freely diffuses out of cells into the blood, which transports it to the lungs, where it is exhaled.
What is the purpose of this experiment and how does it relate to living organisms? Bio Now: Energy Part 1-Energy Transformations
The purpose of this experiment was to make a self sustaining human powered growth chamber that can grow sugar beets. The goal was to see if the growth chamber setup could transfer our own energy into light energy for the goal of growing some plants, specifically organic sugar beets. One of the characteristics of life is that living things require energy. Obtaining and using energy can involve energy transfers, photosynthesis, and cellular respiration. The whole experiment relates to living organisms because all living organisms need energy to survive. Some living organisms can complete this process on their own, but us humans cannot. Living organisms use photosynthesis to make food from sunlight, carbon dioxide and water in the atmosphere. It is their primary source of energy. Living organisms use cellular respiration as a metabolic pathway to convert nutrients into energy, or ATP. The oxygen they breathe is used to breakdown the nutrients consumed through food in order to make ATP, while carbon dioxide and water are generated as waste products.
Production of CO2
The six carbon atoms originally located in a glucose molecule have now become CO2. The prep reaction produces the first two CO2, and the citric acid cycle produces the last four CO2 per glucose molecule. We have already mentioned that this is the CO2 humans and other animals breathe out
ATP Production
The thylakoid space acts as a reservoir for many hydrogen ions (H+). First, each time water is oxidized, two H+ remain in the thylakoid space. Second, as the electrons move from carrier to carrier via redox reactions along the electron transport chain, the electrons give up energy, which is used to pump H+ from the stroma into the thylakoid space Therefore, there are more H+ in the thylakoid space than in the stroma. This difference and the resulting flow of H+ (often referred to as protons in this context) from high to low concentration provide kinetic energy that allows an ATP synthase complex enzyme to enzymatically produce ATP from ADP + Ⓟ. This method of producing ATP is called chemiosmosis, because ATP production is tied to the establishment of an H+ gradient
Efficiency of Fermentation
The two ATP produced per glucose during alcoholic fermentation and lactic acid fermentation are equivalent to 14.6 kcal/mol glucose. Complete glucose breakdown to CO2 and H2O represents a possible energy yield of 686 kcal/mol. Therefore, the efficiency of fermentation is only 14.6 kcal/686 kcal × 100, or 2.1% of the total possible for the complete breakdown of glucose. The inputs and outputs of fermentation are shown here: picture on page 46 The two ATP produced by fermentation fall far short of the theoretical 36 to 38 ATP molecules that may be produced by cellular respiration. To achieve this number of ATP per glucose molecule, it is necessary to move on to the reactions and pathways that occur with oxygen in the mitochondria.
Efficiency of Cellular Respiration
There is still considerable research into the precise ATP yield per glucose molecule. However, most estimates place the actual yield at around 30 ATP per glucose. Using this number we can calculate that only between 32 and 39 percent of the available energy is usually transferred from glucose to ATP. The rest of the energy is lost in the form of heat.
Enzyme
They are proteins that speed up the rate of chemical reactions.
Knowing that chickens tend to walk rather than fly, which muscles would you expect to have the greatest number of mitochondria
Thigh muscles
Catabolism
We already know that glucose is broken down during cellular respiration. However, other molecules like fats and proteins can also be broken down as necessary. When a fat is used as an energy source, it breaks down to glycerol and three fatty acids. As Figure 8.10 indicates, glycerol can be converted to pyruvate and enter glycolysis. The fatty acids are converted to 2-carbon acetyl CoA that enters the citric acid cycle. An 18-carbon fatty acid results in nine acetyl CoA molecules. Calculation shows that respiration of these can produce a total of 108 ATP molecules. This is why fats are an efficient form of stored energy—the three long fatty acid chains per fat molecule can produce considerable ATP when needed. Proteins are less frequently used as an energy source, but they are available as necessary. The carbon skeleton of amino acids can enter glycolysis, be converted to acetyl groups, or enter the citric acid cycle at some other juncture. The carbon skeleton is produced in the liver when an amino acid undergoes deamination, or the removal of the amino group. The amino group becomes ammonia (NH3), which enters the urea cycle and becomes part of urea, the primary excretory product of humans. Just where the carbon skeleton begins degradation depends on the length of the R group, since this determines the number of carbons left after deamination.
Anabolism
We have already seen that the building of new molecules requires ATP produced during breakdown of molecules. These catabolic reactions also provide the basic components used to build new molecules. For example, excessive carbohydrate intake can result in the formation of fat. Extra G3P from glycolysis can be converted to glycerol, and acetyl groups from glycolysis can be joined to form fatty acids, which in turn are used to synthesize fat. This explains why you gain weight from eating too much candy, ice cream, or cake.
a graph of the data from the enzyme concentration experiment should have the dependent variable, which is bubble height, plotted on the ___ axis
Y axis
Preparatory Reaction
converts products from glycolysis into products that enter the citric acid cycle.
The process of glycolysis occurs where in the cell?
cytoplasm
where does anaerobic respiration occur
cytoplasm
the first step of cellular respiration occurs in the ___ and the remaining steps occur in the ___
cytoplasm; mitochondria
•The overall equation for cellular respiration is the opposite of the one we used to represent photosynthesis:
glucose + oxygen --> carbon dioxide + water + energy •In this reaction, glucose has lost hydrogen atoms (been oxidized), and oxygen has gained hydrogen atoms (been reduced). •When oxygen gains electrons, it becomes water. The complete oxidation of a mole of glucose releases 686 kcal of energy, and some of this energy is used to synthesize ATP molecules. If the energy within glucose were released all at once, most of it would dissipate as heat instead of some of it being used to produce ATP. Instead, cells oxidize glucose step by step. The energy is gradually stored and then converted to that of ATP molecules, which is used in animals in the many ways listed in the figure above •The figure above shows us very well that chloroplasts and mitochondria are involved in a cycle. The carbohydrate produced within the chloroplasts becomes a substrate for the cellular respiration reaction that occurs in the mitochondria, while carbon dioxide released by mitochondria becomes a substrate for the photosynthesis reaction that occurs in the chloroplasts •These organelles are involved in a redox cycle, because carbon dioxide is reduced during photosynthesis and carbohydrate is oxidized during cellular respiration. Note that energy does not cycle between the two organelles; instead, it flows from the sun through each step of photosynthesis and cellular respiration until it eventually is released as unusable heat, while ATP is used by the cell.
which of the following are reactants needed for cellular respiration
glucose, oxygen
most extra G3P from photosynthesis is used to build what and what
glucose; fructose
Which one of these pathways would be active in an anaerobic condition?
glycolysis
which step of respiration still occurs even during anaerobic respiration
glycolysis
arrange the steps of cellular respiration from beginning to end
glycolysis pyruvate oxidation kreb's cycle ETC
A different membrane system within the stroma forms flattened sacs called thylakoids, which in some places are stacked to form
grana
•Enzyme Inhibition
•Enzyme inhibition occurs when a molecule (the inhibitor) binds to an enzyme and decreases its activity •The diagram below illustrates noncompetitive inhibition because the inhibitor (F, the end product) binds to the enzyme E1 at a location other than the active site •The site is called an allosteric site •When an inhibitor is at the allosteric site, the active site of the enzyme changes shape, which in turn changes its function In contrast to noncompetitive inhibition, competitive inhibition occurs when an inhibitor and substrate compete against each other for the active site of an enzyme. Product forms only when the substrate, not the inhibitor, is at the active site. In this way, the amount of product is regulated.
•Metabolic Pathways and Enzymes
•Enzyme is a molecule that speeds a chemical reaction without itself being affected by the reaction •The chemical reactions that constitute metabolism would not easily occur without the use of organic catalysts called enzymes •Ribozymes are an enzyme made of RNA and are involved in the synthesis of RNA and the synthesis of proteins at ribosomes •Enzymes allow reactions to occur under mild conditions, and they regulate metabolism, partly by eliminating nonspecific side reactions. •Chemical reactions do not occur haphazardly in healthy cells; they are usually part of a series of linked reactions called a metabolic pathway •Metabolic pathways begin with a particular reactant and end with a final product. Many specific steps can be involved in a metabolic pathway, and each step is a chemical reaction catalyzed by an enzyme. •Substrates are the reactants in an enzymatic reaction The substrates for the first reaction are converted into products, and those products then serve as the substrate for the next enzyme-catalyzed reaction. One reaction leads to the next reaction in an organized, highly regulated manner.
•Factors Affecting Enzymatic Rate
•Generally, enzymes work quickly, and in some instances they can increase the reaction rate more than 10 million times. The rate of a reaction is the amount of product produced per unit time. This rate depends on how much substrate is available to associate at the active sites of enzymes. •Therefore, increasing the amount of substrate and the amount of enzyme can increase the rate of the reaction. •Factors like a change in pH or temperature, as well as inhibitors, can alter the shape of the active site causing a change in the shape of the enzyme, called denaturation •Denaturation prevents an enzyme from binding to its substrate efficiently and thus can decrease the rate of a reaction •thus, enzymes require specific conditions to be met in order to be fully operational. In fact, some enzymes require additional molecules called cofactors, which help speed the rate of the reaction, because they help bind the substrate to the active site, or they participate in the reaction at the active site.
•The overall products of photosynthesis that are shown in the summary equation for the process are
•Glucose •Oxygen
•During cellular respiration, the substrate ____ is oxidized and the substrate _____ is reduced
•Glucose / Oxygen
Functions of ATP Cells
•In living systems, ATP can be used for the following: •Chemical work. ATP supplies the energy needed to synthesize macromolecules (anabolism) that make up the cell, and therefore the organism. •Transport work. ATP supplies the energy needed to pump substances across the plasma membrane. Mechanical work. ATP supplies the energy needed to permit muscles to contract, cilia and flagella to beat, chromosomes to move, and so forth. In most cases, ATP is the immediate source of energy for these processes.
•Enzyme-substrate Complex
•In most instances, only one small part of the enzyme called the active site, associates directly with the substrate • In the active site, the enzyme and substrate are positioned in such a way that they more easily fit together, seemingly as a key fits a lock •However, an active site differs from a lock and key because it undergoes a slight change in shape to accommodate the substrate This is called the induced fit model, because the enzyme is induced to undergo a slight alteration to achieve optimum fit for the substrates. •Some enzymes do more than simply form a complex with their substrate(s); they participate in the reaction. •Trypsin digests protein by breaking peptide bonds. The active site of trypsin contains three amino acids with R groups that actually interact with members of the peptide bond—first to break the bond and then to introduce the components of water. This illustrates that the formation of the enzyme-substrate complex is very important in speeding the reaction. Because enzymes bind only with their substrates, they are sometimes named for their substrates and usually end in -ase. For example, lipase is involved in hydrolyzing lipids.
•A ___ is a series of linked chemical reactions catalyzed by a specific enzyme for each reaction
•Metabolic pathway
Metabolic Reactions and Energy Transformations
•Metabolism is the sum of all chemical reactions that occur in a cell •Includes both spontaneous reactions and energy-requiring reactions •Reactants are substances that participate in a reaction •Products are substances that form as a result of a reaction •In the reaction A + B → C + D, A and B are the reactants, while C and D are the products •Whether a reaction occurs spontaneously—that is, without an input of energy—depends on how much energy is left after the reaction. Using the concept of entropy, or disorder, a reaction occurs spontaneously if it increases the entropy of the universe. •In cell biology, which occurs on a small scale, we are less concerned about the entire universe, which is vast. In such specific instances, cell biologists use the concept of free energy instead of entropy •Free energy is the amount of energy left to do work after a chemical reaction has occurred •The change in free energy after a reaction occurs is determined by subtracting the free energy content of the reactants from that of the products. A negative result (-∆G) means that the products have less free energy than the reactants causing the reaction to occur spontaneously. In our reaction, if C and D have less free energy than A and B, then the reaction occurs without additional input of energy. •Exergonic Reactions are spontaneous reactions that release energy •Endergonic Reactions require an input of energy to occur •In the body, many reactions, such as protein and carbohydrate synthesis, are endergonic. For these nonspontaneous reactions to occur during metabolism, they must be coupled with exergonic reactions, so that a net spontaneous reaction results •Many biological processes use ATP as an energy carrier between exergonic and endergonic reactions
•Mitochondria and Cellular Respiration
•Mitochondria, present in both plants and animals, oxidize carbohydrates and use the released energy to build ATP molecules •Cellular respiration therefore consumes oxygen and produces carbon dioxide and water, the very molecules taken up by chloroplasts
•Energy of Activation
•Molecules frequently do not react with one another unless they are activated in some way. In the lab, for example, in the absence of an enzyme, molecules may be heated in order to increase the number of effective collisions •Energy of Activation is the energy that must be added to cause molecules to react with one another •Activation energy is essential to keep molecules from spontaneously degrading within the cell The figure below shows that an enzyme effectively lowers Ea, thus reducing the energy needed for a chemical reaction to begin. It is important to note that the enzyme has no effect on the energy content of the product; rather, it only influences the rate of the reaction. Reducing the energy of activation increases the rate at which the reaction may occur. For this reason, enzymes are often referred to as catalysts of chemical reactions.
•During photosynthesis, water undergoes a loss of electrons called ___, while carbon dioxide undergoes a gain of electrons called ___
•Oxidation / Reduction
•During photosynthesis hydrogen atoms are transferred from water to carbon dioxide, thus, water has been ___ and carbon dioxide has been ____
•Oxidized / Reduced
cells and entropy
•Photosynthesizing producers use energy from sunlight to create organized structure in biological molecules. Organisms that consume producers are then able to use this potential energy to kinetically drive their own metabolic processes. Thus, the majority of living organisms depend on a constant supply of energy that is originally provided by the sun. The ultimate fate of all solar energy in the biosphere is to become randomized in the universe as heat. A living cell can function because it serves as a temporary repository of order, purchased at the cost of a constant flow of energy.
•The energy stored in the carbon-carbon bonds of glucose is an example of _____ energy.
•Potential and chemical
•______ use energy from the sun to store energy in carbohydrates
•Producers •Photosynthetic Organisms
•The substances that start the reaction are called the _____, whereas the substances that are present at the end of a reaction are _____
•Reactants / Products
•Enzymes regulate which metabolic pathways are utilized and therefore which products are formed because each enzyme works with a __
•Specific type of chemical reaction
•Enzymes regulate which metabolic pathways are utilized and therefore which products are formed because each enzyme works with a ______
•Specific type of chemical reaction
•The rate of a reaction can be increased by increasing the concentration of the _ or _ to a certain point
•Substrate / Enzyme
The second law of thermodynamics states that energy cannot be changed from one form to another without a loss of usable energy.
•The second law of thermodynamics can be stated another way: Every energy transformation makes the universe less organized, or structured, and more disordered, or chaotic. •Entropy is used to indicate the relative amount of disorganization. •Because the processes that occur in cells are energy transformations, the second law means that every process that occurs in cells always does so in a way that increases the total entropy of the universe. The second law means that each cellular process makes less energy available to do useful work in the future.
metabolism
•is the sum of all chemical reactions that occur in a cell Includes both spontaneous reactions and energy-requiring reactions
•In which of the following does an inhibitor bind to an allosteric site on an enzyme?
•noncompetitive inhibition •Enzymes catalyze chemical reactions by which of the following? •lowering the energy of activation in the reaction
•The fact that energy transformations increase the amount of entropy is the basis of which of the following?
•second law of thermodynamics