Molec and Cell 2 Flashcards
(229 cards)
1
Q
Competitive inhibition
A
An inhibitor molecule is similar enough to a substrate that it can bind to an active site to prevent substrates from bonding
2
Q
Noncompetitive inhibition
A
An inhibitor molecule binds to an enzyme in a location other than it’s active site
3
Q
Allosteric site
A
A site that allows molecules to either activate or inhibit enzyme activity but is not the active site
4
Q
Allosteric inhibition
A
Inhibitor molecules bind to enzymes in a location where binding induces a confirmational change that reduces an enzymes affinity for its substrate
Substrates bond with less efficiency
5
Q
Cofactors
A
Inorganic ions that act as helper molecules to enzymes. They promote optimal conformation and function
6
Q
Coenzymes
A
Organic helper molecules with a basic structure of carbon and hydrogen required for enzyme action. They help promote optimal conformation and function
7
Q
Feedback inhibition
A
A reactant to regulate its own further production
8
Q
Induced fit
A
A mild shift that occurs at an active site to optimize reactions and fit to substrates
9
Q
Active site
A
The location within an enzyme where the substrate finds to the enzyme and a reaction occurs
10
Q
What affects the active site’s micro-environment?
A
The different properties depend on the unique combination of amino acid residues, R group, their possessions sequences, structures and properties
11
Q
Denature
A
A process that changes the substances, natural properties, and may affect function
12
Q
Increasing the substrate concentration in an enzymatic reaction could overcome what?
A
Competitive inhibition
13
Q
According to the induced fit hypothesis of enzyme catalysis, what can be deduced?
A
The binding of the substrate changes the shape of the enzymes active site
14
Q
The lock and key analogy for enzymes applies to the specificity of enzymes….doing what?
A
Binding to their substrate
15
Q
What is the difference in Delta G (Gibbs Free Energy) between a catalyzed reaction to the same reaction without a catalyst?
A
The catalyzed reaction will have the same Delta G
16
Q
Delta G stands for what
A
Change in Gibbs Free Energy
17
Q
What is the active site in an enzyme?
A
It is the region involved in the catalytic reaction of the enzyme
18
Q
Fluid mosaic model
A
The plasma membrane is made up of many parts, including carbohydrates, proteins, cholesterol and phospholipids, made up of even smaller parts.
These parts are in constant motion.
19
Q
The function of phospholipids in it the cell membrane
A
Phospholipids help the cell membranes to function and keeping it toxins out and organelles in
20
Q
Cholesterol in the plasma membrane
A
Cholesterol helps act as a buffer where the plasma membrane is not too tight or too loose when made a phospholipids, either saturated or unsaturated
21
Q
The function of protein channels in the plasma membrane
A
Protein channels exists as paths in and out of the cell
22
Q
Carbohydrates in the plasma membrane
A
Carbohydrates bond with glycoproteins and glycolipids for cell receptors to initiate cell responses and adhesion to cells
23
Q
The two types of proteins associated with plasma membranes
A
Integral protein and peripheral protein
24
Q
Peripheral protein
A
The protein found on a membrane surface that helps with many functions of the cell, including communication with other cell parts. It may also help with enzymes acting as catalysts for reactions in the cell
25
Integral protein
The protein found inside of the plasma membrane made of hollow tubes. They allow nutrients in or toxins out of the cell. Different parts of the protein may be hydrophobic or hydrophilic.
26
Glycerol in the plasma membrane
The sugar that is the backbone to phospholipids and helps create the hydrophilic characteristic of a membrane.
27
Glycoprotein
This protein may act as a receptor on the plasma membrane to help cell to cell recognition and attachments. They may also initiate immune responses but can be co-opted by viruses, such as HIV.
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Passive transport
This transport requires no energy as a type of diffusion, but it is only able to allow small non-polar molecules through protein channels in the membrane. These include molecules like lipid hormones, carbon dioxide, and oxygen.
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Active transport
The type of transport through the plasma membrane used for a larger or polar molecules. This requires energy or ATP.
30
Three types of active transport
Uniporter
Symporter
Antiporter
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Uniporter
One molecule passes through one way through a plasma membrane
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Symporter
Two molecules pass the same way through the plasma membrane
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Antiporter
One molecule goes in one way and another goes up the other way through a plasma membrane
34
Three factors that affect diffusion rates
Temperature
Concentration gradient
Pressure
35
Two types of transport proteins
Carrier protein
Channel protein
36
Channel protein definition
Protein tubes through a plasma membrane that allow ionized and polar molecules in and outs through opposite sides. These molecules tend to be small and may require specific signals.
37
Two types of channel proteins for polar molecules
Aquaporin
Ion channels
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Aquaporin channels
Channels used for water to travel through membranes quickly
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Ion channels
Channels in specific tissues where molecules need to pass quickly under specific circumstances for bodily functions to occur. One example is calcium passing through these channels quickly for muscle tissues
40
Carrier proteins
Turnstile type channels that exist for specific molecules. A molecule will fuse to this protein in the protein. Carries it to the other side of the membrane. o
Once it is dropped off another molecule is capable of fusing to this protein to be carried to the other side.
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One example of carrier proteins
Glucose transporter
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Two types of active transport
Primary
Secondary
43
Primary active transport
ATP is the energy source. One example is an ion or molecule moving from a low concentration to a high concentration gradient using a uniporter
Sodium potassium pump
44
Secondary active transport
Energy is required as molecules, ions or atoms are trying to go from a low electrochemical gradient to a high electrochemical gradient. The energy comes from the electrochemical gradient.
One example is the sodium glucose symporter
45
Two types of metabolic pathways
Anabolic
Catabolic
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Metabolism
All chemical reactions of a cell
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Anabolic pathway
Taking small molecules and converting them into large molecules that are usable for energy such as glucose. The stored energy will typically have a greater output of energy.
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Catabolic pathway
Taking large molecules and breaking them down into small molecules to release energy
49
Two types of energy
Kinetic
Potential
50
Kinetic energy
Objects in motion. Examples in the cell include chemical and electrochemical gradients as plasma membranes are dynamic
51
Potential energy
Potential to move and energy may be stored. And human cells cellular respiration helps to store energy in the form of ATP, which is potential energy. It will later be broken down for kinetic energy.
52
Endergonic reactions
Energy is added to a chemical reaction and has a positive Delta G
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Exergonic reactions
Energy is really released in chemical reactions. Delta G is less than zero.
54
Catabolism is to anabolism as x is to y
Exergonic is to endergonic x is to y
55
What is one deducement of the second law of thermodynamics?
Cells require a constant input of energy to maintain their high level of organization
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What is a logical consequence of the second law of thermodynamics?
Every chemical reaction must increase the total entropy of the universe
57
What type of reaction would decrease the entropy within a cell?
Anabolic reaction
58
For a living organism, what is an important consequence of the first law of thermodynamics?
The organism ultimately must obtain all of the necessary energy for life from its environment
59
What structure is most similar to ATP?
An RNA nucleotide
60
When ATP releases some energy, it also releases inorganic phosphates. What happens to the inorganic phosphate in the cell?
And maybe used to form phosphorylated intermediate
61
10,000 molecules of ATP are hydrolyzed to ADP and inorganic phosphate in a test tube. About half as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Why?
The reactant and production concentrations in the test tube are different from those in the cell
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What happens to the heat generated when chemical transport or mechanical work is done by an organism?
The heat is lost to the environment
63
What is the structure of ATP?
Adenine base
Five carbon ring
Ribose
Three phosphate groups (alpha, beta, gamma from low to high energy bonds)
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ATP hydrolysis reaction
ATP + water → ADP + inorganic phosphate + free energy
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If ATP hydrolysis is not coupled with an inorganic reaction, what will happen to the free energy?
This energy is lost as heat
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If ATP hydrolysis is coupled with an inorganic reaction, what happens to the free energy?
The free energy can be used to drive the endergonic reaction
67
What are enzymes?
Protein catalysts that speed up reactions by lowering the required activation energy by binding with reactant molecules
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Activation energy
Energy required for a reaction to proceed
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What is heat energy the main source for in a cell
Activation energy in a cell to reach the transition sites for a reaction
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Metabolic pathway
A series of biochemical reactions that converts one or more substrates into a final product
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Transition in a reaction
And unstable state which happens quickly in a reaction, especially as the heat energy increases
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The law of thermodynamics
The study of energy and energy transfer involving physical matter
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The two rules of the law of thermodynamics
Energy cannot be created or destroyed
Some energy is lost and unusable energy forms such as heat energy. This results an increased entropy
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Four different ways active sites can lower an EA barrier
1. Orienting substrates properly
2. Straining substrate bonds
3. Providing a favorable micro environment
4. Covalent bonding to the substance
75
Allosteric enzyme regulation is usually associated with _____.
An enzyme with more than one subunit
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Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
Localization of enzymes into specific organelles or membranes
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Six major functions of membrane proteins
Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachment to the cytoskeleton and extracellular matrix (ECM)
78
Membrane potential
the voltage difference across a membrane
Voltage is created by differences in the distribution of positive and negative ions across a membrane
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Two combined forces, collectively called the electrochemical gradient, drive the diffusion of ions across a membrane
A chemical force (the ion’s concentration gradient)
An electrical force (the effect of the membrane potential on the ion’s movement)
80
An electrogenic pump
a transport protein that generates voltage across a membrane
help store energy that can be used for cellular work
81
Two types of electrogenic pump
The sodium-potassium pump is the major pump of animal cells
The main pump of plants, fungi, and bacteria is a proton pump
82
Phagocytosis
A cell membrane surrounds the particle and engulfs it.
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Pinocytosis
the cell membrane surrounds a small volume of fluid, and pinches off
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Receptor-mediated endocytosis
the cell's uptake of substances targets a single type of substance that binds to the receptor on the cell membrane's external surface to carry it in vesicles
85
Exocytosis
vesicles containing substances fuse with the plasma membrane. The contents are then released to the cell’s exterior.
86
Bioenergetics
the study of energy flow through a living system
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Metabolism
all chemical reactions of a cell or organism
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A metabolic pathway
series of biochemical reactions that converts one or more substrates into a final product
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Two types of reactions/pathways
Anabolic and catabolic
90
Anabolic
Those that require energy and synthesize larger molecules
91
Catabolic
Those that release energy and break down large molecules into smaller molecules
92
Is photosynthesis an anabolic or catabolic pathway?
Anabolic
93
Thermodynamics
the study of energy and energy transfer involving physical matter
94
1st Law of Thermodynamics
The total amount of energy in the universe if constant: energy cannot be created or destroyed
95
2nd Law of Thermodynamics
The transfer of energy is not completely efficient.
With each chemical reaction, some energy is lost in a form that is unusable, such as heat energy. The result is increased entropy (disorder)
96
What provides the energy for a cell’s endergonic reactions?
Usually, the hydrolysis of ATP.
97
ATP Structure
An an adenosine backbone with three phosphate groups attached
98
ATP Hydrolysis
ATP + H2O → ADP + Pi + free energy
99
An example of energy coupling
The Sodium Potassium Pump
100
Enzymes
protein* catalysts that speed up reactions by lowering the required activation energy
bind with reactant molecules promoting bond-breaking and bond-forming processes
*ribozymes also exist
101
Substrate
reactants to an enzyme that interact at the enzyme’s active site
102
Induced fit
a mild shift in shape of an enzyme that optimizes reactions
103
Four ways an enzyme can affect a reaction
1. position two substrates so they align perfectly for the reaction
2. provide an optimal environment, i.e. acidic or polar, within the active site for the reaction
3. contort/stress the substrate so it is less stable and more likely to react
4. temporarily react with the substrate (chemically change it) making the substrate less stable and more likely to react.
104
Three ways enzymes are regulated
Modifications to temperature and/or pH
Production of molecules that inhibit or promote enzyme function
Availability of coenzymes or cofactors
105
Competitive inhibitors
Molecules that have a similar shape to the substrate, competing with the substrate for the active site rates but do not affect the maximal rate
106
Noncompetitive inhibitors
Molecules that bind to the enzyme at a different location, causing a slower reaction rates and affect the maximal rate
107
Maximal rate
speed of a reaction when substrate is not limited
108
Allosteric inhibitors
They modify the active site of the enzyme so that substrate binding is reduced or prevented
109
Allosteric activators
They modify the active site of the enzyme so that the affinity for the substrate increases
110
Feedback inhibition
Where the end product of the pathway inhibits an upstream step, is an important regulatory mechanism in cells
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Diffusion
The tendency for molecules to spread out evenly into the available space
112
Concentration gradient
the region along which the density of a chemical substance increases or decreases
no work must be done to move substances down the concentration gradient
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Facilitated transport
substances move down their concentration gradients
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Osmosis
water always moves from an area of higher water concentration to one of lower concentration
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Redox reactions
chemical reactions where electrons are transferred from one molecule to another
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Reducing agents
Molecules that can donate electron(s) in a redox reaction
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Oxidizing agents
Molecules that can accept electron(s) in a redox reaction
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The reduced product
Molecules that gain electron(s) after the reaction
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The oxidized product
Molecules that lose electron(s) after the reaction
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Electron carrier
Very important molecules in cellular respiration and photosynthesis.
They shuttle electrons to electron transport chains where ATP is produced.
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Dephosphorylation
The loss of a phosphate group from a molecule
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Phosphorylation
The process of adding a phosphate group is to a molecule
They tend to be less stable and more likely to react
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ADP undergoes what to create ATP
Phosphorylation
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Where does the energy for ADP to ATP come from
a coupled exergonic reaction (substrate-level phosphorylation) (10%)
a process called chemiosmosis, which requires the enzyme ATP synthase (90%)
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Where does ATP formation occur
Occurs in mitochondria, chloroplasts, and plasma membrane of aerobic prokaryotes
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What metabolic pathways are involved in cellular respiration
Glycolysis
Oxidation of Pyruvate and Citric Acid Cycle
Oxidative Phosphorylation
127
Glycolysis
the first metabolic pathway of glucose metabolism; includes 10 enzymatic reactions
Nearly all organisms perform glycolysis
occurs in the cytoplasm
O2 is not required
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What are the inputs of glycolysis
1 Glucose, 2 NAD+, 2 ATP, 4 ADP
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What are the outputs of glycolysis
2 Pyruvate, 2 NADH, 4 ATP, 2 ADP
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Substrate-level phosphorylation occurs where?
in both glycolysis and the citric acid cycle
131
When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is what? (Think oxidation and laws of thermodynamics)
reduced, and energy is released
132
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
100%
133
If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to the rates of ATP and carbon dioxide production?
The rates of ATP production and carbon dioxide production would both increase.
134
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle and what is released?
135
Which electron carrier(s) function in the citric acid cycle?
NADH and FADH2
136
Most of the CO2 from the catabolism of glucose is released during when?
the citric acid cycle
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What is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
acetyl CoA
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If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle?
2/3
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Pyruvate oxidation
2 pyruvate molecules enter mitochondria where each is converted to Acetyl CoA before entering the CAC
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Result of pyruvate oxidation
a CO2 is released
pyruvate is oxidized, transferring e- to NAD+ to create NADH
coenzyme A is attached
141
Pyruvate oxidation inputs
2 pyruvate, 2 NAD+
2 coenzyme A
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Pyruvate oxidation outputs
2 CO2, 2 NADH, 2 acetyl CoA
143
Citric Acid Cycle
a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins
144
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the what?
creation of a proton-motive force
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The electron transport chain _____.
is a series of redox reactions
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What takes place in the electron transport chain?
the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle
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Where are the proteins of the electron transport chain located for oxidative phosphorylation?
mitochondrial inner membrane
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During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
molecular oxygen (O2)
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During aerobic respiration, electrons travel downhill in which sequence?
glucose → NADH → electron transport chain → oxygen
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The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because it explains _____.
how ATP is synthesized by a proton motive force
151
During aerobic respiration, what donates electrons to the electron transport chain at the lowest energy level?
FADH2
152
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.
153
What occurs in the cytosol of a eukaryotic cell?
glycolysis and fermentation
154
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing what carbon sources for energy?
glucose
155
An organism is discovered that thrives in both the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight.
facultative anaerobe
156
New biosensors, applied like a temporary tattoo to the skin, can alert serious athletes that they are about to "hit the wall" and find it difficult to continue exercising. These biosensors monitor lactate, a form of lactic acid, released in sweat during strenuous exercise. Why?
During anaerobic respiration, lactate levels increase when muscles cells need more energy, however muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration.
157
Citric Acid Cycle
is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.
158
Outputs of the CAC
4 ATP (2 from glycolysis, 2 from CAC)
6 CO2 (2 from oxidation of pyruvate, 4 from CAC)
10 NADH (2 from glycolysis, 2 from oxidation of pyruvate, 6 from CAC)
2 FADH2 (from CAC)
159
In glycolysis, is most of the energy from glucose stored in the ATP, the CO2, or the electron carrier molecules?
Electron carrier molecules
160
Oxidative phosphorylation
a cellular process that harnesses the reduction of oxygen to generate high-energy phosphate bonds in the form of adenosine triphosphate (ATP)
The only pathway that uses O2 as an input
161
Two ways of generating ATP in oxidative phosphorylation
an electron transport chain and chemiosmosis, which generates ATP
162
The energy to power chemiosmosis in oxidative phosphorylation
A H+ concentration gradient created by the ETC
163
An Electron Transfer Chain
a series of electron transporters embedded in the inner mitochondrial membrane
164
The electron carriers in oxidative phosphorylation
NADH and FADH2 to O2
165
Chemiosmosis
kinetic energy from protons falling down its gradient to form ATP from ADP + Pi
the complex, integral protein ATP synthase mediates this reaction
166
The number of ATP generated by cellular respiration
30-36 per glucose
varies by species and how efficiently NADH from glycolysis enters mitochondria
167
Cellular respiration in total stores
34% of the energy from glucose in ATP
168
Glycolysis without O2
NAD+ is an input of glycolysis; regenerated during oxidative phosphorylation when O2 is present
When O2 is lacking, fermentation regenerates NAD+
169
Two common types of fermentation
Lactic acid fermentation
Alcohol fermentation
170
Lactic acid fermentation
Occurs in muscle cells when O2 is limited, mammalian red blood cells, & some bacteria, ex. those in yogurt
Pyruvate + NADH → lactate + NAD+
171
Lactic acid enzyme
Lactate dehydrogenase
172
Alcohol fermentation
anaerobic yeast species
involves:
First, catalyzed by pyruvate decarboxylase
Second, by alcohol dehydrogenase
Pyruvate → CO2 + acetylaldehide
acetylaldehide + NADH → ethanol + NAD+
173
Cellular respiration is regulated by many mechanisms, including
Hormonal control of glucose entry into the cell
Enzyme reversibility (functioning to substrate product equilibrium) or irreversibility (able to exceed equilibrium)
Enzyme sensitivity to pH changes due to lactic acid build-up
Feedback controls
174
Photosynthesis
the process that converts solar energy into chemical energy
directly or indirectly, photosynthesis nourishes almost the entire living world
175
Autotrophs
the producers of the biosphere, producing organic molecules from CO2 and other inorganic molecules
Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules
176
Photosynthesis occurs
plants, algae, certain other unicellular eukaryotes, and some prokaryotes
These organisms feed not only themselves but also most of the living world
177
Heterotrophs
the consumers of the biosphere
Almost all heterotrophs, including humans, depend on photoautotrophs for food and O2
178
Chloroplasts structure
structurally similar to and likely evolved from photosynthetic bacteria
the structural organization of these organelles allows for the chemical reactions of photosynthesis
179
The 3 Sites of Photosynthesis in Plants
Leaves are the major locations of photosynthesis
Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf
CO2 enters and O2 exits the leaf through microscopic pores called stomata
180
Stroma
the dense fluid in an envelope of two membranes in chloroplasts
181
Thylakoids
connected sacs in the chloroplast which compose a third membrane system
182
Grana
Stacks of thylakoids
183
Chlorophyll
the pigment which gives leaves their green colour, resides in the thylakoid membranes
184
Is photosynthesis ender or exergonic
Endergonic
185
What is oxidized and reduced in photosynthesis
H2O is oxidized and CO2 is reduced
186
Two Stages of Photosynthesis
Light Cycle and Calvin Cycle
187
The light reactions and products (in the thylakoids)
Split H2O
Release O2
Reduce the electron acceptor NADP+ to NADPH
Generate ATP from ADP by photophosphorylation
188
The Calvin cycle (in the stroma)
forms sugar from CO2, using ATP and NADPH
The Calvin cycle begins with carbon fixation
189
Carbon Fixation
In photosynthesis, incorporating CO2 into organic molecules
190
Light
a form of electromagnetic energy, also called electromagnetic radiation
191
Wavelength
the distance between crests of waves
wavelength determines the type of electromagnetic energy
192
electromagnetic spectrum
the entire range of electromagnetic energy, or radiation
193
Visible light
wavelengths that we can see
194
photons
Discrete particles of light
195
Pigments
substances that absorb visible light
196
Wavelengths that are not absorbed
Colors reflected back
197
absorption spectrum
a graph plotting a pigment’s light absorption versus wavelength
198
absorption spectrum of chlorophyll a
suggests that violet-blue and red light work best for photosynthesis
199
action spectrum
the relative effectiveness of different wavelengths of radiation in driving a process
200
chlorophyll b
Accessory pigments that broaden the spectrum used for photosynthesis
201
The difference in the absorption spectrum between chlorophyll a and b
to a slight structural difference between the pigment molecules
202
carotenoids
Accessory pigments that absorb excessive light that would damage chlorophyll
203
An excited pigment
a pigment absorbs light which is unstable
204
fluorescence
excited electrons fall back to the ground state, photons are given off
205
illuminated
an isolated solution of chlorophyll will fluoresce, giving off light and heat
206
photosystem
of a reaction-center complex (a type of protein complex) surrounded by light-harvesting complexes that transfer the energy of photons to the reaction center
207
reaction-center complex
a type of photosynthesis protein complex
208
light-harvesting complexes
pigment molecules bound to proteins
209
primary electron acceptor
the reaction center for photosynthesis accepts excited electrons and are reduced as a result
210
Photosystem II (PS II) best wavelength
best at absorbing a wavelength of 680 nm
211
reaction-center chlorophyll a of PS II
P680
212
Photosystem I (PS I)
best at absorbing a wavelength of 700 nm
213
reaction-center chlorophyll a of PS I
P700
214
During the light reactions, there are two possible routes for electron flow
cyclic and linear
215
Linear electron flow
the primary pathway, involves both photosystems and produces ATP and NADPH using light energy
216
Step 1 in linear electron flow
A photon hits a pigment and its energy is passed among pigment molecules until it excites P680
217
Step 2 in linear electron flow
An excited electron from P680 is transferred to the primary electron acceptor (we now call it P680+)
218
Step 3 in linear electron flow
H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680
P680+ is the strongest known biological oxidizing agent
O2 is released as a by-product of this reaction
219
Step 4 in linear electron flow
Each electron “falls” down an electron transport chain from the primary electron acceptor of PS II to PS I
220
Step 5 in linear electron flow
Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane
Diffusion of H+ (protons) across the membrane drives ATP synthesis
221
Step 6 in linear electron flow
In PS I (like PS II), transferred light energy excites P700, which loses an electron to an electron acceptor
P700+ (P700 that is missing an electron) accepts an electron passed down from PS II via the electron transport chain
222
Step 7 in linear electron flow
Each electron “falls” down an electron transport chain from the primary electron acceptor of PS I to the protein ferredoxin (Fd)
223
Step 8 in linear electron flow
The electrons are then transferred to NADP+ and reduce it to NADPH
The electrons of NADPH are available for the reactions of the Calvin cycle
This process also removes an H+ from the stroma
224
Cyclic Electron Flow
electrons cycle back from Fd to the PS I reaction center
Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH
No oxygen is released
225
Which light reaction (cyclic and linear) is thought to have come first
Cyclic electron flow
226
ATP and NADPH are produced on the side facing the stroma, where at in the cycle of photosynthesis
Calvin cycle
227
The Calvin cycle has three phases
Carbon fixation (catalyzed by rubisco)
Reduction
Regeneration of the CO2 acceptor (RuBP)
228
Calvin cycle reactants
Take place in the stroma
Use ATP and NADPH to convert to CO2 to the sugar G3P
Return ADP, inorganic phosphate, and NADP+ to the light reactions
229
CAC Input
Acetyl CoA
