Cellular Respiration
What is the maximum yield of ATP per glucose? What is the actual yield of ATP per glucose? Why?
- 38 ATP - 36 ATP - 2 ATP needed to move 2 NAD into mitochondria
What does the Krebs cycle produce within two turns?
- 6 NADH - 2 FADH2 - 2 ATP - 4 CO2
What are the four metabolic stages of cellular respiration?
1) Glycolysis 2) Conversion of Pyruvate to Acetyl CoA 3) Krebs Cycle 4) Electron Transport Chain and Oxidative Phosphorylation
For every molecule of glucose, what is the net yield of ATP from glycolysis?
2 ATP
What are the totals per molecule of glucose in the Krebs Cycle?
2 Acetyl CoA => 4CO2 + 6NADH + 2FADH2 + 2ATP
What are the totals per molecule of glucose in the conversion of pyruvate to Acetyl CoA?
2 Pyruvate => 2 Acetyl CoA + 2CO2 + 2NADH
How many turns of the Krebs cycle does one glucose molecule cause?
2 turns
In the Krebs cycle, what molecules acquires most of the energy that is released by the oxidation of acetyl CoA, and how many of these molecules are produced during each turn of the cycle?
3 NADH
What percent is the efficiency of glycolysis approximately?
3.5%
What is the approximate maximum efficiency of aerobic respiration?
66%
What is the net number of... A) ATP B) NADH produced by glycolysis?
A) 2 B) 2
What are the... A) Reactants B) Products of the Krebs Cycle?
A) Acetyl CoA B) CO2, NADH, FADH2, ATP
The Krebs cycle... A) Breaks down a two-carbon molecule into two molecules of carbon dioxide B) Produces a six-carbon molecule from six molecules of carbon dioxide C) Produces NAD+ from NADH and H+ D) Generates most of the ATP produced in aerobic respiration
A) Breaks down a two-carbon molecule into two molecules of carbon dioxide
What are the... A) Reactants B) Intermediate C) Products of glycolysis?
A) Glucose B) PGAL C) Pyruvic Acid, NADH, ATP
What are the... A) Reactants B) Products of the electron transport chain?
A) NADH, FADH2 B) H2O, ATP
What are the... A) Reactants B) Products of the conversion of pyruvate to Acetyl CoA?
A) Pyruvate B) CO2, NADH, Acetyl CoA
What are the... A) Reactants B) Products of alcoholic fermentation?
A) Pyruvate, NADH B) CO2, Ethyl Alcohol (Beer, wine, bread)
What are the... A) Reactants B) Products of lactic acid fermentation?
A) Pyruvate, NADH B) Lactic acid
What organisms use lactic acid fermentation?
Bacteria, muscles (sprinting, weight lifting)
During glycolysis, glucose is... A) Produced from two molecules of pyruvic acid B) Converted into two molecules of ATP C) Partially broken down and some of its stored energy is released D) Partially broken down and its stored energy is increased
C) Partially broken down and some of its stored energy is released
The electron transport chain of aerobic respiration... A) Generates oxygen from water B) Produces NADH by chemiosmosis C) Pumps electrons into the mitochondrial matrix D) Pumps protons into the space between the inner and outer mitochondrial membranes
D) Pumps protons into the space between the inner and outer mitochondrial membranes
Which reactions of aerobic respiration occur in the inner mitochondrial membrane?
Electron Transport Chain
What role does oxygen serve in aerobic respiration?
Forms water: O2 + 4e- + 4H+ => 2H2O (Oxygen is the final acceptor of electrons. By accepting electrons from the last molecule in the ETC, oxygen allows additional electrons to pass along the chain. As a result, ATP can continue to be synthesized by chemiosmosis. Oxygen also accepts the protons that were once part of the hydrogen atoms supplied by NADH and FADH2.)
MAIN IDEAS: GLYCOLYSIS AND FERMENTATION
I. Cellular respiration is the process by which cells break down organic compounds to release energy and make ATP. It includes anaerobic pathways, which operate in the absence of oxygen, and aerobic respiration, which occurs when oxygen is present. II. Cellular respiration begins with glycolysis, which takes place in the cytosol of cells. During glycolysis, one glucose molecule is oxidized to form two pyruvic acid molecules. Glycolysis results in a net production of two ATP molecules and four NADH molecules. III. Fermentation is a set of anaerobic pathways in which pyruvic acid is converted into other organic molecules in the cytosol. Fermentation does not produce ATP, but it does regenerate NAD+, which helps keep glycolysis operating. IV. In lactic acid fermentation, an enzyme converts pyruvic acid into lactic acid. V. In alcoholic fermentation, other enzymes convert pyruvic acid into ethyl alcohol and CO2. VI. Through glycolysis, only about 3.5 percent of the energy available from the oxidation of glucose is transferred to ATP. VII. The anaerobic pathways probably evolved very early in the history of life on Earth. For more than a billion years, they were the only pathways available for harvesting chemical energy.
MAIN IDEAS: AEROBIC RESPIRATION
I. In the presence of oxygen, pyruvic acid is converted into acetyl CoA. In eukaryotic cells, this reactions occurs inside the mitochondrial matrix. II. Acetyl CoA enters the Krebs cycle, a biochemical pathway that also takes place in the mitochondrial matrix. Each turn of the Krebs cycle generates three NADH, one FADH2, one ATP, and two CO2 molecules. III. NADH and FADH2 donate electrons to the electron transport chain, which lines the inner mitochondrial membrane. Electrons are passed from molecule to molecule in the transport chain in a series of redox reactions. IV. As electrons pass along the electron transport chain, protons donated by NADH and FADH2 are pumped into the space between the inner and outer mitochondrial membranes. This pumping creates a concentration gradient of protons across the inner mitochondrial membrane. As protons move down their gradient and back into the mitochondrial matrix, ATP synthase uses the energy released by their movement to make ATP. V. During aerobic respiration, oxygen accepts both protons and electrons from the electron transport chain. As a result, oxygen is converted to water. VI. Aerobic respiration can produce up to 38 ATP molecules from the oxidation of a single molecule of glucose. This means that up to 66% of the energy released by the oxidation of glucose can be transferred to ATP. However, most eukaryotic cells produce only about 36 ATP molecules per molecule of glucose. VII. Besides transferring energy to ATP, cellular respiration also provides carbon skeletons that can be built up into larger molecules by cells.
What are the two major stages of aerobic respiration?
Krebs cycle and electron transport chain
What do both lactic acid fermentation and alcoholic fermentation produce?
NAD+ from NADH and H+
What are the energy-containing products of glycolysis?
NADH, ATP, Pyruvic acid
Explain the five main steps of the Krebs cycle.
Step 1) Acetyl CoA + Oxaloacetic Acid => Citric Acid; regenerates coenzyme A (A 2-Carbon molecule of acetyl CoA combines with a 4-Carbon compound, oxaloacetic acid, to produce a 6-Carbon compound, citric acid.) Step 2) Citric Acid => 5-Carbon Compound; releases carbon dioxide, converts NAD+ to NADH + H+ (Citric acid releases a carbon dioxide molecule and a hydrogen atom to form a 5-Carbon compound. By losing a hydrogen atom with its electron, citric acid is oxidized. The hydrogen atom is transferred to NAD+, reducing it to NADH.) Step 3) 5-Carbon Compound => 4-Carbon Compound; releases carbon dioxide, converts NAD+ to NADH + H+, produces ATP (The 5-Carbon compound formed in Step 2 also releases a carbon dioxide molecule and a hydrogen atom, forming a 4-Carbon compound. Again, NAD+ is reduced to NADH. A molecule of ATP is also synthesized from ADP.) Step 4) 4-Carbon Compound => (different) 4-Carbon Compound; converts FAD to FADH2 (The 4-Carbon compound formed in Step 3 releases a hydrogen atom to form another 4-Carbon compound. This time, the hydrogen atom is used to reduce FAD to FADH2.) Step 5) 4-Carbon Compound => Oxaloacetic Acid; converts NAD+ to NADH (The 4-Carbon compound formed in Step 4 releases a hydrogen atom to regenerate oxaloacetic acid, which keeps the Krebs cycle operating. The hydrogen atom reduces NAD+ to NADH.)
Explain the steps of the electron transport chain.
Step 1) Electrons Are Passed Along Series of Molecules (High energy electrons from NADH and FADH2 are passed along a series of molecules. As they move from molecule to molecule, the electrons lose some of their energy.) Step 2) Protons Are Pumped into the Inner Mitochondrial Membrane (The "lost" energy is used to pump the protons of the hydrogen atoms from the mitochondrial matrix to the other side of the inner mitochondrial membrane. This pumping builds up a high concentration of protons in the space between the inner and outer mitochondrial membranes. In other words, a concentration gradient of protons is created across the inner mitochondrial membrane.) Step 3) Chemiosmosis Occurs (The concentration gradient of protons drives the synthesis of ATP by chemiosmosis. ATP synthase molecules that are located in the inner mitochondrial membrane makes ATP from ADP as protons move down their concentration gradient into the mitochondrial matrix.)
Explain the four main steps of glycolysis.
Step 1) Glucose => 6-Carbon Compound; uses 2 ATP (Two phosphate groups attach to glucose, which forms a new 6-Carbon compound. The phosphate groups came from two molecules of ATP, which are converted into two molecules of ADP in the process.) Step 2) 6-Carbon Compound => 2 Molecules of PGAL (The 6-Carbon compound formed in Step 1 is split into two 3-Carbon molecules of PGAL.) Step 3) 2 Molecules of PGAL => 2 Molecules of 3-Carbon Compound; converts 2 NAD+ to 2 NADH + 2 H+ (The two PGAL molecules are oxidized, and they each receive a phosphate group. The product of this step is two molecules of a new 3-Carbon compound. The oxidation of PGAL is accompanied by the reduction of two molecules of NAD+ to NADH. NAD+ is an organic molecule that accepts electrons during redox reactions.) Step 4) 2 Molecules of 3-Carbon Compound => 2 Molecules of Pyruvic Acid; produces 4 ATP (The phosphate groups added in Step 1 and Step 3 are removed from the three-carbon compounds formed in Step 3. This reaction produces two molecules of pyruvic acid. Each phosphate group is combined with a molecule of ADP to make a molecule of ATP. Because a total of four phosphate groups were added in Step 1 and Step 3, four molecules of ATP are produced.)
Which process produces more ATP- glycolysis or aerobic respiration?
aerobic respiration
How is acetyl CoA formed?
after entering mitochondrial matrix, pyruvic acid reacts with coenzyme A, forming acetyl CoA (this reaction also reduces a molecule of NAD+ to NADH)
What type of fermentation is the basis of wine and beer industries?
alcoholic fermentation
Of what importance are lactic acid fermentation and alcoholic fermentation to the cells that use these pathways?
allows glycolysis to continue due to their regeneration of NAD+
What is the Krebs cycle?
biochemical pathway that breaks down acetyl CoA (produces carbon dioxide, hydrogen atoms, and ATP)
What is cellular respiration?
biological pathway that breaks down sugar to form ATP
What is glycolysis?
breaks down glucose to form ATP and pyruvate
What is aerobic respiration?
cellular respiration that requires oxygen
Why is the mitochondrial matrix important when pertaining to the Krebs cycle?
contains enzymes needed to catalyze reactions of the Krebs cycle
What is lactic acid fermentation?
conversion of pyruvate to lactic acid (allows continuation of glycolysis through NAD+ production)
What is alcoholic fermentation?
conversion of pyruvate to two-carbon compound through release of carbon dioxide then conversion of two-carbon compound to ethyl alcohol (allows for continuation of glycolysis through production of NAD+)
Where do the reactions of glycolysis take place?
cytosol of cell
Where do the products of glycolysis go if oxygen is absent?
fermentation pathways (lactic acid, alcoholic)
Why are the fermentation pathways referred to as "anaerobic" pathways?
happens without oxygen
Where does glycolysis take place?
in the cytosol
What is the space called where there is a build up of H+ ions?
inner membrane space
Where does the reactions of aerobic respiration take place?
inside the mitochondria
Why does lactic acid cause pain?
lactic acid accumulates in the muscle cells (product of lactic acid fermentation), making the cells' cytosol more acidic, increased acidity reduces capacity of cells to contract which results in muscle fatigue, pain, and cramps
What type of fermentation plays an essential role in the manufacture of food products such as yogurt and cheese?
lactic acid fermentation
What organisms can have all of their energy needs met by anaerobic pathways?
many unicellular and some multicellular organisms
How is the structure of a mitochondrion well adapted for the activities it carries out?
membrane allows protons to be pumped against the concentration gradient and onto the other side, which allows CHEMIOSMOSIS (the synthesis of ATP through the pushing of protons out of ATP synthase) to take place
Chemiosmosis produces ATP molecules in what space?
mitochondrial matrix
What is FAD?
molecule that accepts electrons during redox reactions (flavin adenine dinucleotide)
What is the starting substance of the Krebs cycle (which is regenerated at the end of the cycle)?
oxaloacetic acid
What is the final electron acceptor at the end of the ETC?
oxygen
In the creation of water from oxygen at the end of the ETC, where do the H+ ions come from?
proton pump
What is the breakdown product of glucose that diffuses into the mitochondrial matrix for further breakdown?
pyruvic acid
What happens in alcoholic fermentation?
pyruvic acid from glycolysis is converted into ethyl alcohol; NADH is oxidized to NAD+ which goes back to glycolysis
What happens in lactic acid fermentation?
pyruvic acid from glycolysis is reduced to lactic acid; NADH is oxidized to NAD+ which goes back to glycolysis
What is the mitochondrial matrix?
space inside the inner membrane of a mitochondria
What organisms use alcoholic fermentation?
yeast, few other organisms
