Biology- Cellular Respiration Flashcards
Cellular respiration
An ATP generating process that occurs within cells. Energy is extracted from energy-rich glucose to form ATP from ADP and Pi
What’s the chemical equation for cellular respiration?
C6H12O6 + 6 O2 => 6 CO2 + 6 H2O + energy
Aerobic Respiration
cellular respiration in the presence of O2. It is divided into 3 parts: glycolysis, the Krebs cycle (includes pyruvate Decarboxylation), and oxidative phosphorylation
Glycolysis (Aerobic Respiration)
the decomposition (lysis) of glucose (glycol) to pyruvate (or pyruvic acid). Magnesium ions (Mg2+) are cofactors that promote enzyme activity in most steps of glycolysis.
- 2 ATP are added.
- 2 NADH are produced. NADH, a coenzyme, forms when NAD+ combines w/ 2 energy-rich e- and H+ (obtained from an intermediate molecule during the breakdown of glucose). As a result, NADH is an energy-rich molecule
- 4 ATP are produced.
- 2 pyruvate are formed.
In summary, glycolysis?
It takes 1 glucose and turns it into 2 pyruvate, 2 NADH, and a net of 2 ATP (made 4 ATP, but used 2 ATP). This process occurs in the cytosol.
The Krebs Cycle (Aerobic Respiration)
1⃣ Pyruvate to acetyl CoA.
2⃣Kreb’s Cycle: 3 NADH, 1 FADH2, 1 ATP, 2 CO2 made per turn. Krebs begins when acetyl CoA combines with OAA (oxaloacetate) to form citrate. FADH2, like NADH, is a coenzyme, accepting electrons during a reaction.
Oxidative Phosphorylation (Aerobic Respiration)
the process of extracting ATP from NADH and FADH2.
-Electrons from NADH and FADH2, pass along an ETC. The chain consists of proteins that pass these electrons from one protein to the next. Some carrier proteins, such as the cytochromes, include nonprotein parts containing iron. Along each step of the chain, the electrons give up energy used to phosphorylate ADP to ATP. NADH provides electrons that have enough energy to generate about 3 ATP, while FADH2, generates about 2 ATP. The final electron acceptor of the ETC is oxygen. The 1/2 O2 accepts the 2 electrons and together w/ 2 H+, forms water.
Where do the Krebs cycle and oxidative phosphorylation?
They occur in mitochondria
Krebs/ pyruvate Decarboxylation- matrix
Oxidative phosphorylation- inner membrane
How many ATP in the Krebs Cycle?
The Krebs cycle produces 6 NADH, 2 FADH2, and 2 ATP. If each NADH produces 3 ATP during oxidative phosphorylation, and FADH2 produces 2 ATP. Krebs cycle 2 ATP 6 NADH X 3 =>18 ATP 2 FADH2 X 2 => 4 ATP
How many ATP in glycolysis?
2 ATP (made 4 ATP, but used 2 ATP to change glucose to 2 PGAL)
What are the four distinct areas of a mitochondria?
- Outer membrane- this membrane, like the plasma membrane, consists of a double layer of phospholipids.
- Intermembrane space- narrow area between the inner and outer membranes. H+ ions (protons) accumulate here.
- Inner membrane- this second membrane, also a double phospholipid bilayer, has convolutions called cristae. Within the membrane and its cristae, the electron transport chain, consisting of a series of protein complexes, removes electrons from NADH and FADH2 and transports H+ ions from the matrix to the intermembrane space. A protein complex called ATP synthase, is responsible for the phosphorylation of ADP to form ATP.
- Matrix- the matrix is the fluid material that fills the area inside the inner membrane. The Krebs cycle and the conversion of pyruvate to acetyl CoA occur here.
Where does oxidative phosphorylation occur in the mitochondria?
inner membrane
Chemiosmosis
the mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane
Step 1 of Chemiosmosis
- The Krebs cycle produces NADH and FADH2 in the matrix. CO2 is also made and substrate-level phosphorylation occurs to produce ATP
Step 2 of Chemiosmosis
- Electrons are removed from NADH and FADH2. Protein complexes in the inner membrane remove electrons from these two molecules (2A, 2B). The electrons move along the electron transport chain, from one protein complex to the next
Step 3 of Chemiosmosis
- H+ ions (protons) are transported from the matrix to the intermembrane compartment. Protein complexes transport H+ ions from the matrix, across the inner membrane, and to the intermembrane space (3A, 3B, 3C)
Step 4 of Chemiosmosis
A pH and electrical gradient across the inner membrane is created. As H+ are transferred from the matrix to the intermembrane space, the concentration of H+ increases in the intermembrane space and decreases in the matrix (pH increases). The concentration of H+ in the matrix decreases further as electrons at the end of the ETC (PC IV) combine w/ H+ and oxygen to form water. The result is a proton gradient (equivalent to a pH gradient) and an electric charge (or voltage) gradient.
-These gradients are potential energy reserves in the same way as water behind a dam is stored energy
Step 5 of Chemiosmosis
ATP synthase generates ATP. ATP synthase, a channel protein in the inner membrane, allows the protons in the intermembrane compartment to flow back into the matrix. The protons moving through the channel generate the energy for ATP synthase to generate ATP.
-It is similar to how turbines in a dam generate electricity when water flows through them
What are the two types of Phosphorylation?
- Substrate level phosphorylation
2. Oxidative phosphorylation
Substrate level phosphorylation
occurs when a phosphate group and its associated energy is transferred to ADP to form ATP. The substrate molecule (the one w/ the phosphate group) donates the high energy phosphate group. Such phosphorylation occurs during glycolysis
Oxidative phosphorylation
occurs when a phosphate group ➕ ADP to form ATP, but the energy for the bond does not accompany the phosphate group.
Instead, electrons in the ETC of oxidative phosphorylation supply the energy 〽️
The energy is used to generate the H+ gradient which, in turn, supplies the energy to ATP synthases to generate ATP from ADP and a phosphate group
What happens if oxygen is not present for aerobic respiration?
No electron acceptor exists to accept the e- at the end of ETC. If this happens, then NADH accumulates. After all the NAD+ has been converted to NADH, the Krebs cycle and glycolysis both stop (both need NAD+ to accept e-). When this happens, no new ATP is produced, and the cell soon dies.
Anaerobic respiration
a form of cellular respiration that occurs when oxygen is scarce or absent; takes place in the cytosol
What are the two common metabolic pathways of anaerobic respiration?
alcohol and lactic acid fermentation; the objective of both processes is to replenish NAD+ so that glycolysis can continue once again.
Alcohol Fermentation
occurs in plants, fungi (such as yeasts), and bacteria.
1. Pyruvate to acetaldehyde. For each pyruvate, 1 CO2 and 1 acetaldehyde are produced. The CO2 formed is the source of carbonation in fermented drinks like beer and champagne.
2. Acetaldehyde to ethanol. The important part of this step is that the energy in NADH is used to drive this reaction, releasing NAD+.
For each acetaldehyde, 1 ethanol is made and 1 NAD+ produced. The ethanol (ethyl alcohol) produced here is the source of alcohol in beer and wine.
In alcohol fermentation, why does the energy in an energy-rich molecule like NADH that is removed, put into the formation of ethanol, which is essentially a waste product that eventually kills the yeast (and other organisms) that produce it?
The goal of the pathway is to free NAD+ for use by glycolysis since w/o oxygen the NAD+ is bottled up in NADH. The pathway isn’t really focused on making ethanol. The reward is 2 ATP from glycolysis for each 2 converted pyruvate, which is not much but better than having 0 ATP
Lactic Acid Fermentation
A pyruvate is converted to lactate (or lactic acid) and in the process, NADH gives up its e- to form NAD+, where NAD+ can now be used for glycolysis.
In humans and other mammals, most lactate is transported to the liver where it is converted back to glucose when surplus ATP is available
What’s the final product of aerobic respiration?
Water
Pyruvate Decarboxylation
Pyruvate to acetyl coenzyme A; happens in the mitochondrial matrix
Makes 2 NADH and 2 CO2, catalyzed by PDC enzyme (pyruvate dehydrogenase complex)
