Chapter 8 -- Cellular Respiration

Order of Glycolysis

1. Phosphate groups from two ATP molecules are transferred to a glucose molecule. 2. A six-carbon compound is broken down into two three-carbon compounds. 3. Two NADH molecules and four ATP molecules are produced. 4. Each 3-carbon compound is converted into a 3-carbon pyruvate (there are two 2ATPs and two NADhs because the glucose that was split in half--there are two sides, so 2ATP is on the left, and 2 ATP is on the right, which equals 4 ATP total. And there is 1 NADH on each side, so there are 2 total)

Steps of the Krebs cycle

1. The Krebs cycle begins with acetyl CoA combining with a 4-carbon compound to form a 6-carbon compound known as citric acid. 2. Citric acid is then broken down in the next series of steps, releasing two molecules of carbon dioxide and generating one ATP, three NADH, and one FADH2. (FAD is another electron carrier similar to NAD+ and NADP+.) 3. Acetyl CoA and citric acid are generated and the cycle continues.

What is the net yield of ATP produced by glycolysis

2 ATPs

What is the net yield of ATP produced by the Krebs cycle

2 ATPs

What is the total net yield of ATP from one molecule of glucose

36 ATPs

How many total ATP molecules are produced from the glycolysis of one six-carbon glucose?

4 ATP's are produced

Which molecule is released when ATP becomes ADP? A. phosphate group B. water molecule C. ribose sugar D. energy cells

A - Phosphate group

Which stage of cellular respiration is the anaerobic process? A. glycolysis B. Krebs cycle C. electron transport

A - glycolysis

What prevents pyruvate from entering the Krebs cycle and instead results in this pathway?

A lack of oxygen

Anaerobic Respiration

A metabolic process that does not require energy. This pathway follows glycolysis, but instead of going to the Krebs cycle it goes through fermentation.

Aerobic Respiration

A metabolic process that requires oxygen. This includes processes like the Krebs cycle and Electron Transport. This is typically just referred to as cellular respiration.

Where does cellular respiration occur in the cell?

Cellular respiration occurs in 3 main parts and in two different places in the cell: glycolysis occurs in the cytoplasm, and the Krebs Cycle and the electron transport occur in the mitochondria.

What is another name for the Krebs cycle?

Citric Acid cycle

Step 2 of glycolysis

Cleavage - Splits into two different processes, which basically means that the glucose divides so what's happening in the energy harvest is done twice and at the same time. So it was a 6-carbon molecule and now its split into two 3-carbon molecules called G3P

Step 3 of glycolysis

Energy Harvest - Takes 1 electron and 2 phosphates from G3P, aka "harvesting" energy from the G3P. It then adds an electron to NAD+ to make NADH, and adds two phosphates to 2ADP to get 2ATP. When this happens the two 3-carbon compounds (G3p) are converted into 2 molecules of pyruvate--because it lost that one electron and 2 phosphates, it's no longer G3p and now it is pyruvate. At the same time 4 molecules of ATP are produced and 2 molecules of NADH. In the end, the net gain of ATP is only 2 because, although it gained 4 molecules at the end, it also used 2 in the beginning → 4-2=2. These new pyruvates will go on to the next cycle, the Kreb Cycle (IF there is oxygen. If there is not oxygen it will go to fermentation instead)

Lactic Acid Fermentation

Enzymes convert the 2 pyruvates (aka pyruvic acids) into lactic acid. This involves the transfer of high energy electrons and protons from NADH. Skeletal muscles produce periods of strenuous exercise. While humans muscles can do aerobic respiration, it can shift to lactic acid fermentation if they experience an oxygen debt, such as when you are exercising really hard. First an organism goes through glycolysis like normal, which makes 2 net ATP, 2 pyruvate, and 2 NADH. Now it needs to regenerate the NAD+. The 2 pyruvate on the reactant side will ultimately yield 2 lactate. The pyruvate can act as an electron acceptor, allowing NADH to be oxidized to NAD+ so that glycolysis can start over. After an intense workout, lactic acid can build up in the muscle cells, causing muscles to become fatigued and feel sore. Lactic acid also is produced by several microorganisms that often are used to produce many foods like cheese, yogurt, sour cream--the bacteria that are involved in making yogurt use lactic acid fermentation. Similar to lactic acid fermentation, Alcohol fermentation happens after the organism goes through glycolysis, and NADH oxidizes to NAD+.

What happens to a pyruvic acid molecule in mitochondria leading up to the formation of Acetyl CoA? (this is part of the Krebs cycle)

First it's just a pyruvate molecule, and then 1 carbon is removed from it to make carbon dioxide and electrons are stripped from it to form NADH. When these things are taken away, the pyruvate is now only a 2 carbon fragment. From there Coenzyme A attaches to the 2 carbon fragment, forming Acetyl CoA.

Step 1 of glycolysis

Investment - Glycolysis phosphorylated (giving something a phosphate) a glucose molecule by having ATP lose a phosphate, turning to ADP, and then the glucose gets this phosphate. This happens twice and turns the glucose into fructose-1-6 Bisphosphate. Acts as activation energy.

Krebs Cycle/Citric Acid Cycle

Most of the energy from the glucose is still contained in the pyruvate. This is a series of reactions in which pyruvate is broken down into carbon dioxide. It takes place inside the mitochondria of the cell. As pyruvate, which is a 3-carbon molecule, moves to the krebs cycle, it loses a carbon molecule, which combines with something else and makes carbon dioxide. Carbon dioxide is then released as a waste product. Then pyruvate loses its other two carbons, which react with coenzyme A (CoA) to form a 2-carbon intermediate called Acetyl CoA. (after this happens CoA leaves the Krebs cycle) During this, NAD+ is also converted to NADH. (this all happens before the krebs cycle begins) Acetyl CoA then moves into the mitochondrial matrix and combines with a 4-carbon compound to form citric acid, a 6-carbon compound. The reaction results in the production of 1 carbon dioxide molecule and 1 NADH molecule. Citric acid continues to be broken down throughout the cycle, turning into a 5-carbon compound; resulting in 2 more carbon dioxide molecules, 4 more NADHs, 1 more FADH2 and 1 ATP. And lastly it breaks down into a 4-carbon compound, which starts the process all over again with that combining with Acetyl CoA. Two molecules of pyruvate are formed during glycolysis, resulting in two "turns" of the Krebs cycle for each glucose molecule. The net yield of TWO turns of the Krebs cycle (b/c there's 2 pyruvates): 6 CO2 molecules, 2 ATPs, 8 NADH, 2 FADH2--(NADH and FADH2 are electron carriers) Then the NADH and FADH2 go on to the electron transport chain. This is also called the citric acid cycle because it breaks pyruvate down into citric acid, which then breaks down into carbon dioxide, atp, nadh, and fadh2. which is broken down into 2 carbon dioxide molecules. *ALL I NEED TO KNOW HOW FOR QUIZ IS THE NET YIELD AND THAT THE NADH AND FADH2 GO ON TO CARRY ELECTRONS AND PHOSPHATES TO THE ELECTRON TRANSPORT CHAIN*

Fermentation

Occurs in the cytoplasm and regenerates the cell's supply of NAD+ while producing a small amount of ATP. This happens after glycolysis to anaerobic organisms--organisms who do not need oxygen to grow and reproduce. However, these organisms cannot rely solely on glycolysis. Glycolysis only provides 2 net ATP for each molecule of glucose, and a cell has a limited amount of NAD+. When all the NAD+ is used up, glycolysis will stop. This is why it needs fermentation--to make more NAD+ and ATP for the cell. The electron transport chain has to have oxygen, so after glycolysis, instead of the two pyruvic acids going to the krebs cycle and then the transport chain, it goes through fermentation.

Alcohol fermentation

Occurs in yeast and some bacteria. So first an organism goes through glycolysis like normal, which makes 2 net ATP, 2 pyruvate, and 2 NADH. This step is needed to generate the NAD+ so it can keep doing glycolysis. The two pyruvate molecules that were made are used in a chemical reaction which ultimately produces carbon dioxide and 2 ethanol (alcohol). The derivative of pyruvate, acetaldehyde, can act as an electron acceptor in the process so that the 2 NADH can be oxidized (when something loses electrons) to 2 NAD+ so that glycolysis can start all over again. Ethanol is a waste product in the process. Yeasts also can do alcoholic fermentation when making bread, and the carbon dioxide product helps the bread rise. And the tiny amount of alcohol produced in the short fermentation time of bread will evaporate in the baking process--in simple terms, when you make bread you add sugar to the yeast. The yeast eats the sugar and produces carbon dioxide in the form of gas, which causes the bread to rise. Similar to lactic acid fermentation, NADH donates electrons during this reaction and NAD+ is regenerated. In all this is used by microorganisms to produce alcohol, carbon dioxide, and NAD+

Prokaryotic cellular respiration

Some prokaryotes also undergo aerobic respiration. Because prokaryotes do not have a mitochondria, there are differences in this process. The main difference involves the use of the prokaryotic cellular membrane as the location of the electron transport. In eukaryotic cells, pyruvate is transported to the mitochondria. In prokaryotes, this movement is unnecessary, saving the prokaryotic cell two ATP, and increasing the net total of ATP produced to 38.

Electron Transport Chain

The most ATP during cellular respiration is produced during this, with 32 ATPs being made. Produced from the Krebs cycle, NADH and FADH2 carry high energy electrons and hydrogen ions that are used to *convert ADP to ATP* in the electron transport. To start, electrons move along the mitochondrial membrane from one protein to another, so as NADH and FADH2 release electrons, the energy carriers are converted back to NAD+ and FAD (so they can go back to the beginning with glycolysis and begin this all over again--b/c they started as NAD+ and FAD). The energy released by electrons is used to pump H+ ions (positively charged hydrogens) into the mitochondrial matrix (basically the other side of the membrane) across the inner mitochondrial membrane, creating a concentration gradient. H+ ions then diffuse down their concentration gradient back across the membrane and into the matrix through ATP synthase molecules in chemiosmosis. The H+ ions are pumped into the cell using a protein pump to make a gradient, and then pumped back out again using the ATP Synthase to get rid of the gradient and re-create equilibrium again. The ATP synthase is like a water turbine, where the hydrogen ions are like water that spin the turbine. This activates the production of ATP by reattaching inorganic Phosphate to ADP to create ATP. The electron transport ends up generating the most ATP out of everything else. The electron transport and chemiosmosis act similarly in cellular respiration and photosynthesis. Oxygen is the final electron acceptor in the electron transport system in respiration, with oxygen gaining protons and electrons so that water is formed. In all, this produces 32 ATP molecules--each NADH molecule produces 3 ATP and each group of 3 FADH2 produces 2 ATP. In eukaryotes, one molecule of glucose yields 36 ATP under ideal conditions The final step in the breakdown of glucose in aerobic respiration.

Glycolysis

The process in which glucose is broken down in the cytoplasm of the cell. Glucose needs energy to break down so it uses previously stored energy to start its cleave (split). In the end it forms two pyruvates. This happens in both anaerobic and aerobic respiration. How this actually happens → one molecule of glucose is broken in half into two 3-carbon molecules (because glucose is a 6-carbon molecule, so 6 split in half is 3) But this needs energy to happen, so 2 ATP's that were made in the past must be used to give the energy to split glucose. Two molecules of NADH and two molecules of ATP are formed for each molecule of glucose that is broken down. Then electrons and phosphates taken from the G3p are used to make NAD+ into NADH and 2ADP into 2ATP. When this happens pyruvic acid is produced, along with a small amount of energy in the cytoplasm of the cell (kinda like how when ATP was broken down to ADP it released energy to power the Na+/K+ ATPase pump--when glucose is split it releases energy). First stage in cellular respiration. *Hint:* Glyco = glucose, lysis = split, and this is splitting glucose *This all happens in the different stages--investment, cleavage and energy harvest.*

True or False: Skeletal muscle produces lactic acid when the body cannot supply enough oxygen.

True

True or False: The two pyruvate molecules formed during glycolysis result in two Krebs cycles.

True

What are some things that go through Alcohol fermentation?

Yeast, alcohol, types of bacteria and microorganisms--this is why most alcohol is NOT gluten free; it contains yeast

Cellular respiration harvests electrons from carbon compounds, such as _________________________ , and uses that energy to make ___________________________ .

glucose, ATP

In __________________________ , glucose is broken down into pyruvate.

glycolysis

What is it called when something loses electrons

oxidized

What are some things that go through lactic acid fermentation?

yogurt, cheese, sour cream, humans (muscles, red blood cells)

What is it called when something gains electrons

reduced

Similarities and differences between photosynthesis and cellular respiration

*Photosynthesis:* reactants are carbon dioxide, water and products are oxygen and glucose *Respiration:* Reactants are oxygen and glucose, products are carbon dioxide and water *Both:* a process used for cells to retain energy, a metabolic pathway that produces and breaks down simple carbohydrates

Name the different parts of the mitochondria

- *Strands of mitochondrial DNA* → string og green circles that are connected to look kinda like a worm - *Outer membrane* → the wall on the outside of the mitochondria - *Inner membrane* →the wall on the inside of the mitochondria - *Intermembrane space* →a very small compartment between the outer and inner membrane - *Matrix* → blue gel like material inside the cristae, thicker than the cells cytoplasm, contains DNA - *Cristae* →the swirling wavy border thingy inside the mitochondria that holds the matrix

What is the net yield of ATP produced by the electron transport chain

32 ATPs

Two molecules of ________ and two molecules of ________________ are formed for every glucose molecule that is broken down.

ATP, NADH

Which process produces more energy—the anaerobic pathway or the aerobic pathway?

Aerobic pathway produces much more ATP's per glucose

Which molecule generated by the Krebs cycle is a waste product? A. CoA B. CO2 C. FADH2 D. NADH

B - CO2

Which represents the general sequence of cellular respiration? A. TCA cycle →chemiosmosis →glycolysis B. glycolysis →Krebs cycle → electron transport C. electron absorption →catalysis →phosphorylation D. aerobic pathway →anaerobic pathway →fermentation

B - glycolysis →Krebs cycle →electron transport

In which metabolic process are molecules broken down to produce carbon dioxide and water?: A. photosynthesis B. homeostasis C. cellular respiration D. fermentation

C - cellular respiration

Cellular respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O Glucose + oxygen = carbon dioxide (6) + water (6) + Energy (about 36 ATP)

During the Krebs cycle, pyruvate is broken down into what compound?

CO2

What is the final step of cellular respiration called?

Electron transport -- the electron transport is the last step to break down glucose in cellular respiration where high energy electrons and hydrogen ions from NADH and FADH2 that were produced in the Krebs cycle are used to convert ADP to ATP

True or False: fermentation occurs in the mitochondria

False - it occurs in the cytoplasm

True or False: Cellular respiration in eukaryotes is slightly more efficient than in prokaryotes

False -- it is slightly faster in prokaryotes than it is in eukaryotes

Cellular respiration

How organisms obtain energy. The equation for cellular respiration is the opposite of the equation for photosynthesis. Cellular respiration occurs in 3 main parts and in two different places in the cell: glycolysis, which occurs in the cytoplasm, and the Krebs Cycle and electron transport, which occur in the mitochondria.

Where does glycolysis occur?

In the cytoplasm of the cell

Name the two types of anaerobic respiration

Lactic Acid fermentation and alcoholic fermentation

How does NAD+ turn into NADH

NAD+ reduces, so it gains electrons and becomes NADH

How does NADH turn into NAD+

NADH oxidizes, which means it loses electrons so it can become NAD+

What is the final step of the electron transport chain in cellular respiration?

O2 and H+ form H2O

Why is there a net gain of only two ATP molecules in the glycolysis of one six-carbon glucose?

Only 2 ATPs are actually gained because 2 had to be used in the beginning to break the water molecule. So 4-2 =2

What is chemiosmosis?

The movement of ions across a semipermeable membrane, down their gradient. This includes harnessing protons and ATP synthase. Ex: the formation of ATP -- hydrogen ions move across a membrane during cellular respiration or photosynthesis.

What is the overall purpose of cellular respiration?

To make ATP

True or False: The anaerobic pathway that follows glycolysis in the absence of oxygen is fermentation.

True - in an anaerobic pathway there is not enough oxygen to go through the Krebs cycle and electron transport chain, so instead it goes through an alternate process called fermentation.

A ____________________ process requires oxygen

aerobic

Glycolysis is an __________________________ process because it does not require oxygen

anaerobic

Organisms obtain energy in a process called ___________________________ .

cellular respiration

ATP is used to provide ___________________________ for cells to do work.

energy

True or False: The hydrogen necessary in the electron transport chain comes from the splitting of carbon dioxide molecules.

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