bio chap 6

Krebs cycle produces ATP

As citrate is converted, each turn of the cycle produces 1 ATP via substrate-level phosphorylatio

How much ATP is produced

So far, aerobic respiration of one glucose molecule has yielded only four ATP.

aerobic cellular respiration

Aerobic cellular respiration is a series of chemical reactions that break down glucose. The reactants are glucose and oxygen. It is aerobic respiration because it is oxygen dependent (that's why we breath to stay alive). The products are carbon dioxide, water, and ATP. Overall: C6H12O6+O2→CO2+H2O+ATP Know this equation. Notice that it is the reverse of the equation for photosynthesis. Know that C6H12O6 is glucose and that it's breakdown releases CO2. We breath in O2 and breath out CO2. Remember plants take in CO2 and releaseO2.

Krebs cycle transfers energy to NAD+, FAD

As citrate is converted, each turn of the cycle transfers electrons to different electron carrier molecules, yielding 3 NADH and 1 FADH_2.

The ETC creates a H+ gradient

As electrons travel through the transport chain, carrier molecules use the potential energy of the electrons to transport hydrogen ions into the intermembrane compartment.

ETC requires oxygen

At the end of the transport chain, electrons are donated to an oxygen atom, which combines with hydrogens to form water Oxygen is the final electron acceptor. Without it, the chain shuts down ETC requires oxygen At the end of the transport chain, electrons are donated to an oxygen atom, which combines with hydrogens to form water. Oxygen is the final electron acceptor. Without it, the chain shuts down.

Photosynthesis and respiration are ancient pathways

Both of these chemical processes arose in unicellular organisms over 3 billion years ago Photosynthesis and respiration are ancient pathways Both of these chemical processes arose in unicellular organisms over 3 billion years ago.

Electrons hold the rest of the energy

But 10 NADH molecules have been produced, as well as two FADH2. These molecules carry electrons to the electron transport chain. Electrons hold the rest of the energy But 10 NADH molecules have been produced, as well as two FADH2. These molecules carry electrons to the electron transport chain. It is the energy stored here that will be used in electron transport to build a chemiosmotic gradient of H+ (protons) for making ATP.

cell need atp

Cells need ATP ATP is the form of energy cells are able to use. Cells use the ATP formed during cellular respiration to: •Do work, such as active transport or muscle contractions; •Power chemical reactions. In this slide Cellular respiration's role in muscle function is an example: a.Cellular respiration produces ATP by breaking down the covalent bonds of glucose. Muscle contraction uses that energy stored in ATP

how does cellular respiration

Cellular respiration releases energy from glucose in a series of small steps

Krebs cycle regenerates oxaloacetate

Citrate is converted into isocitrate, a-ketoglutarate, succinyl CoA, succinate, fumarate, malate, and finally oxaloacetate. This allows the cycle to start again.

Fermentation generates ATP only in glycolysis

During fermentation only some of the energy from glucose is extracted. The oxidation of a glucose molecule yields only 2 ATP. Fermentation generates ATP only in glycolysis During fermentation only some of the energy from glucose is extracted. The oxidation of a glucose molecule yields only 2 ATP. a.Alcoholic fermentation b.Lactic acid fermentation

pyvuvate

Each pyruvate has now been reduced to form 2 acetyl molecules. Each of these acetyl groups are only 2 carbon atoms long. Each acetyl group attaches to a carrier molecule called Coenzyme A (CoA for short). If oxygen is available this Acetyl CoA complex enters the mitochondria and passes its acetyl group (2 carbons) into the Krebs Cycle. The Krebs Cycle will continue oxidizing the acetyl groups to completely break down the remaining carbon to carbon bonds from the original glucose molecu

overview electron tranport chain

Electron transport chain (ETC): overview Long Description Oxygen accepts electrons and combines with hydrogen atoms to form water at the last protein complex in the electron transport chain. Nearby the electron transport chain, the A T P synthase channel protein is also embedded in the inner mitochondrial membrane

Eukaryotes - Krebs cycle takes place in mitochondria Section 6.3 Between the mitochondrial membranes is an intermembrane compartment (outer chamber). The space within the inner membrane (inner chamber) is the mitochondrial matrix, which houses the enzymes of the Krebs cycle.

Eukaryotes - electron transport chain takes place in mitochondria Review mitochondria structure in detail. Mitochondria have two phospholipid bilayers: an outer membrane and an inner membrane. Many enzymes are embedded in the inner membrane, catalyzing the reactions of the electron transport chain.

Fermentation regenerates NAD^+

Fermentation uses pyruvate to oxidize NADH, and regenerate NAD^+ . The pyruvate is converted into alcohol, lactic acid, or other byproducts.Fermentation regenerates NAD^+ Fermentation uses pyruvate to oxidize NADH, and regenerate NAD^+ . The pyruvate is converted into alcohol, lactic acid, or other byproducts.

Cellular respiration of one glucose yields 36 ATP

Glycolysis and Krebs cycle each produce 2 ATP The electron transport chain produces 34 ATP. Transporting NADH into the mitochondrion requires 2 ATP, making the total production of ATP equal to 36. How much ATP is produced? So far, aerobic respiration of one glucose molecule has yielded only four ATP. Remember it is ATP the cell need to produce to survive!

whats produced

Glycolysis produces 2 molecules of ATP Section 6.4 Glycolysis occurs outside of the mitochondrion, in the cytoplasm. The enzymes of glycolysis extract some of the potential energy stored in glucose. Figure 6.4

Where does cellular respiration take place?

Glycolysis reactions occur in the cytosol of cells. The rest of the reactions depend on the cell type. For prokaryotic cells, Krebs Cycle occurs in the cytosol and the electron transport chain in the cell membrane.

Activatiion of glycolysis

Glycolysis: Glycolysis requires an input of two ATP to "activate" glucose. To begin the breakdown of glucose, the glucose molecule must be "activated" by adding some energy by the cell. This is done by using 2 ATP molecules to add 2 phosphates onto the glucose molecule. Adding this energy makes the glucose molecule less stable and more easily broken in two. The activated glucose is then converted into two 3-carbon intermediates called PGAL. PGAL is short for phosphoglyceraldehyde. Energy investment 1.Phosphates is transferred from ATP to glucose -ADP is released to be reused. 2.Glucose is rearranged 3.A second phosphate transferred from ATP 4.A 6-carbon intermediate splits into two different 3-carbon intermediates. 5.One of the 3-carbon intermediates is converted into the other type, so there are two molecules of PGAL from each glucose molecule.

A net gain of 2 ATP are produced

Glycolysis: a net gain of 2 ATP are produced In total, four ATP are produced. Recall that two ATP were used to start the reactions. The net yield is two ATP.

glycolysis

Glycolysis: a very small amount of energy is extracted during glycolysis Each half of the glucose molecule proceeds to the energy extraction reactions of glycolysis. Energy harvest from each half of the glucose molecule after it splits: 6.Each half undergoes oxidation ( stripping away an electron and its energy) and 2 phosphates are added to each half (phosphorylation). ● 7.Two phosphates from each half are then transferred to ADP to make 4 ATP. This is Substrate-level phosphorylation. ● 9.Remember this is a carbohydrate - H2O is released during the process. ● 10.Overall substrate-level phosphorylation yields 4 ATP and two molecules of pyruvate per glucose. But remember that 2 ATP had to be used to start the process so only 2 ATP were really gained during glycolysis.

glyclysis produces 2 NADH

Glycolysis: also produces 2 NADH molecules: NADH stands for "nicotinamide adenine dinucleotide (NAD) + hydrogen (H). First, an electron is taken from each half of the glucose. This is an oxidation reaction. This high energy electron is transferred to NAD , producing two NADH molecules. This is a reduction reaction. Notice that since an electron is negative a Proton (H+) usually goes along with it hence the H on NADH. NADH is an electron carrier molecule very similar to NADPH that was studied in photosynthesis. It carries and transfers electrons that store energy. NADH can be seen as a source of "reducing energy" since it can pass its high energy electrons off to other compounds. This reducing energy will be used later by oxidative respiration in making more ATP.

Glycolysis requires NAD^+ to pick up electrons

In aerobic cellular respiration NADH gives up its electrons in the ETC, regenerating the NAD^+ needed for glycolysis. The ETC requires oxygen, so what can cells do in anaerobic situations? In aerobic cellular respiration NADH gives up its electrons in the ETC, regenerating the NAD^+ needed for glycolysis. The ETC requires oxygen, so what can cells do in anaerobic situations?

Microbes carry out alcoholic fermentation

In alcoholic fermentation, NADH reduces pyruvate to ethanol. NAD^+ is re-created Microbes carry out alcoholic fermentation In alcoholic fermentation, NADH reduces pyruvate to ethanol. NAD^+is re-created

Microbes carry out alcoholic fermentation Long Description

In alcoholic fermentation, glycolysis first converts one glucose molecule to 2 molecules of pyruvate and yields 2 A T P and 2 N A D H molecules. Then, the 2 pyruvate molecules are converted into 2 molecules of ethanol, which yields 2 C O 2 molecules and oxidizes the 2 N A D H molecules back into 2 N A D + plus 2 H +. In lactic acid fermentation, glycolysis first converts one glucose molecule to 2 molecules of pyruvate and yields 2 A T P and 2 N A D H molecules. Then, the 2 pyruvate molecules are converted into 2 molecules of lactic acid or lactate, and in the process, the 2 N A D H molecules are oxidized back into 2 N A D + plus 2 H +.

Bacteria and muscle cells both carry out lactic acid fermentation

In lactic acid fermentation, NADH reduces pyruvate to lactic acid.〖 NAD〗^+is re-created Bacteria and muscle cells both carry out lactic acid fermentation In lactic acid fermentation, NADH reduces pyruvate to make lactic acid.〖 NAD〗^+is re-created. a.Alcoholic fermentation b.Lactic acid fermentation

Glycolysis: ATP is produced from ADP

In substrate-level phosphorylation, an enzyme transfers a phosphate from a donor molecule to ADP. In glycolysis the donor is each half of the original glucose molecule.

Cells have alternative pathways

In the absence of oxygen, a cell can re-create NAD^+ in other pathways, called anaerobic respiration and fermentation Cells have alternative pathways In the absence of oxygen, a cell can re-create NAD^+ in other pathways, called anaerobic respiration and fermentation

kreb cycle produces what?

Krebs cycle produces Co_2 Section 6.5 Inputs and outputs reflect total yield for one glucose molecule. Step 1 - Acetyl CoA combines with a 4-carbon molecule called oxaloacetate, yielding 6-carbon citrate. Step 2 - Citrate is rearranged and oxidized, converting it into several intermediates. For each turn of the cycle, these reactions give off 2 molecules of carbon dioxide. Step 3 - As citrate is converted, each turn of the cycle produces 1 ATP via substrate-level phosphorylation. Step 4 - As citrate is converted, each turn of the cycle transfers electrons to different electron carrier molecules, yielding 3 NADH and 1 FADH_2. Step 5 - Krebs cycle regenerates oxaloacetate. Citrate is converted into isocitrate, a-ketoglutarate, succinyl CoA, succinate, fumarate, malate, and finally oxaloacetate. This allows the cycle to start again. So far, aerobic respiration of one glucose molecule has yielded only four ATP. But 10 NADH molecules have been produced, as well as two FADH2. These molecules carry electrons to the electron transport chain.

Krebs cycle overview

Krebs cycle: overview During the Krebs cycle, the two acetyl CoA molecules are oxidized, yielding : 4 CO2, 2 ATP, 6 NADH, and 2 FADH2. FADH2 is another electron carrier molecule very similar to NADH. For our purposes it does the same thing as NADH being involved in the redox reactions of the Krebs Cycle. Do not get lost in the details of the Krebs Cycle. I do not expect you to memorize or know all the steps of this cycle. I know it is visually complicated, especially to a non-biology major. I will point out the few key things I want you to know about the cycle as I go through this.

Cellular respiration is not always aerobic

Many organisms can survive in the absence of oxygen. Glycolysis produces ATP without requiring oxygen. Cellular respiration is not always aerobic Many organisms can survive in the absence of oxygen. Glycolysis produces small amounts of ATP without requiring oxygen

Fermentation allows glycolysis to produce ATP

Many prokaryotes and some eukaryotic cells use fermentation.. There is no Krebs cycle or ETC in fermentation. Fermentation simply allows glycolysis to continue, producing small amounts of ATP. Fermentation allows glycolysis to produce ATP Many prokaryotes and some eukaryotic cells use fermentation.. There is no Krebs cycle or ETC in fermentation. Fermentation simply allows glycolysis to continue, producing small amounts of ATP

Anaerobic respiration produces ATP during ETC

Many prokaryotes use anaerobic respiration. Anaerobic respiration includes Krebs cycle and an ETC. The ETC uses electron acceptor molecules other than O2. Different electron acceptors allow for less ATP production than oxygen. Many prokaryotes use anaerobic respiration in the absence of oxygen. Anaerobic respiration includes Krebs cycle and an ETC. The ETC uses electron acceptor molecules other than O2. Different electron acceptors allow for less ATP production than oxygen

Electron transport chain (ETC): overview

NADH and FADH2 donate their electrons to the electron transport chain, where energy from the electrons is used to produce many ATP •Many electron transport chains are embedded in the inner mitochondrial membrane. • •At this point make sure you understand how electrons flow through transport chains by redox reactions due to electronegativity. • •Each protein in the chain is more electronegative then the one before - electrons are pulled through. •When an electron is lost the molecule that loses it is oxidized, the one that gained the electron is reduced. •So each transfer is one redox reaction. • •These electrons ultimately end up being added onto Oxygen - this is why we need to breath in O2. Without it the whole process cannot proceed and cells die from a lack of ATP in seconds. • •The oxygen atoms with an extra electron take up H+ protons and become water molecules. • •The energy of electron flow is coupled to pumping protons (H+) from the inner to the outer mitochondrial chamber forming a chemiosmotic gradient. • •The concentrated protons of the gradient are allowed to flow through ATP Syntase and their energy is used to make ATP from ADP. • •Finally the energy harvested from glucose is used to make the most of the cell's needed quantity of ATP.

Glycoloysis summary

Notice that glycolysis is only the beginning of the metabolic break down of the covalent bonds of glucose. Very little energy is recovered from glucose by the time pyruvate is produced. Most of the energy of the original glucose molecule is still stored in the covalent bonds of the 2 pyruvate molecules. Know this summary: Glycolysis requires: •1 glucose •2 NAD+ •2 ADP Glycolysis yields: •2 pyruvate •2 electron-carrying NADH molecules •2 ATP.

Photosynthesis and respiration are related pathways

Photosynthesis and respiration are connected in many ways: water, oxygen, carbon dioxide, sugars. Photosynthesis and respiration are related pathways Photosynthesis and respiration are connected in many ways: water, oxygen, carbon dioxide, sugars.

How do photosynthesis and respiration compare? TABLE 6.1 Photosynthesis and Respiration Compared Notice that respiration is the reverse of photosynthesis

Photosynthesis captures light energy and uses it to reduce CO2 to store energy in the covalent bonds between carbon atoms of glucose. Respiration oxidizes glucose to break covalent bonds between carbon atoms to release and harvest the energy to make ATP for cellular needs

Photosynthesis and respiration developed over time

Photosynthesis may have evolved from glycolysis, since some Calvin cycle reactions are the reverse of glycolysis reactions Since virtually all cells carry out glycolysis, it is probably the first of these energy pathways to arise Photosynthesis and respiration developed over time Photosynthesis may have evolved from glycolysis, since some Calvin cycle reactions are the reverse of glycolysis reactions. Since virtually all cells carry out glycolysis, it is probably the first of these energy pathways to arise.

Other carbohydrates enter the energy-extracting pathways

Polysaccharides such as glycogen and starch are composed of glucose Electrons hold the rest of the energy But 10 NADH molecules have been produced, as well as two FADH2. These molecules carry electrons to the electron transport chain. It is the energy stored here that will be used in electron transport to build a chemiosmotic gradient of H+ (protons) for making ATP.Other carbohydrates enter the energy-extracting pathways: Polysaccharides such as glycogen and starch are composed of glucose. Breakdown of large macro-molecules to simple molecules Breakdown of simple molecules to pyruvate and/or acetyl CoA, accompanied by production of limited ATP and NADH Complete oxidation of acetyl CoA to H2O and CO2 produces ATP and much NADH and FADH2, which in turn yield ATP via electron transport and chemiosmosis

Other food molecules enter the energy-extracting pathways

Proteins and fats are also used as energy sources for the cell •Components of fats can be converted to pyruvate or acetyl CoA. •Amino acids from proteins can be converted to pyruvate, Acetyl CoA or Krebs cycle intermediates. Other food molecules enter the energy-extracting pathways Proteins and fats are also used as energy sources for the cell. •Components of fats can be converted to pyruvate or acetyl CoA. •Amino acids from proteins can be converted to pyruvate, Acetyl CoA or Krebs cycle intermediates.

stage 1 of celluar resperation

Stage 1 is glycolysis Glycolysis means "splitting of glucose." This occurs in the cytosol of the cell. During glycolysis, 1 molecule of glucose is split into 2 three-carbon molecules of pyruvate. These reactions release 2 molecules of ATP.

stage 2 cellurar resperarion

Stage 2 is the Krebs cycle Inside mitochondria, the Acetyl CoA molecules are disassembled during the Krebs cycle. Energy from Acetyl CoA is transferred to electrons. These reactions release 2 molecules of CO2

Stage 3 of cellural resperation

Stage 3 is the electron transport chain Electrons are unloaded into the electron transport chain, where the potential energy in the electrons is used to produce more ATP. These reactions require oxygen and release water

Krebs cycle steps

The Krebs cycle is a series of steps. Figure explanation: •Carbon atoms are represented by grey balls with covalent links between them •Remember they are carbohydrates even though the details of the molecules are not shown. •This is a cycle because a carrier molecule (oxaloacetate) accepts the 2 carbons from the incoming acetyl CoA, carries them through the reactions to finish breaking down the bonds and then the carrier is reformed to be used again. •Notice CoA is released to be reused. •Places where you see NAD+ converted to NADH is where the molecule is oxidized to break a carbon bond. •You will see two CO2 molecules released at these oxidation points. Those are the last of the carbons from the original six carbon glucose molecule. •Notice that yet more NADH and some FADH2 is also made. These redox reactions are done to remake the carrier oxaloacetate to begin the cycle again. •Notice many NADH and FADH2 molecules are made to be used later but very little ATP is made during the Krebs Cycle. •Remember the original glucose was 6 carbon atoms long. Glycolysis cut it in two to yield 2 pyruvate molecules. Each pyruvate then produced a 2 carbon acetyl group that attached to CoA. Both are shuttled into the Krebs Cycle. However this diagram only shows one at a time. •So, the cycle must go around twice to finally breakdown one glucose molecule and harvest its energy. •So far very little ATP has been made. Most of the energy recovered from the breakdown of glucose is stored in the form of NADH and FADH2 reducing power to be used later to finally make the ATP needed by the cell. Inputs and outputs at the top left of the slide reflect total yield for one glucose molecule.

Aerobic respiration yields many ATP, 2

The electron transport chain produces 34 ATP Because this process uses oxygen is is called aerobic respiration (also oxidative respirations). Aerobic respiration yields many ATP The electron transport chain produces 34 ATP.

ETC: ATP synthase forms ATP

The hydrogen ions move down their concentration gradient from the intermembrane compartment into the matrix and pass through an enzyme called ATP synthase ATP synthase produces ATP via chemiosmotic phosphorylation ETC: ATP synthase forms ATP The hydrogen ions move down their concentration gradient from the intermembrane compartment into the matrix and pass through an enzyme called ATP synthase. ATP synthase produces ATP via chemiosmotic phosphorylation.

second stage of Metabolic breakdown

The second stage of the metabolic breakdown of glucose is aerobic respiration (also called oxidative respiration). Aerobic respiration takes place in the mitochondria to completely finish breaking down the original glucose covalent bonds. Aerobic respiration yields many ATP molecules representing the majority of the energy in the original glucose molecule. Aerobic respiration consists of the reactions of Krebs cycle, electron transport and chemiosmotic ATP synthesis. These reactions yield much more ATP than glycolysis. The reactions of Krebs cycle and the electron transport chain require oxygen gas.

Tansition step more detail

Transition step - 2 carbons from each pyruvate are transported into the mitochondria: overview The two pyruvate molecules produced in glycolysis undergo an oxidation reaction as they enter the mitochondrion (this is sometimes called the transition step).

next transition

Transition step follows glycolysis In the transition step, the 2 molecules of pyruvate are converted into 2 molecules of Acetyl CoA. This reaction releases 2 molecules of CO2.

Cellular respiration is the process that makes ATP Aerobic cellular respiration (uses oxygen) is used by all plants and animals, fungi and protozoa as well as many microbes. The energy from glucose (stored in covalent bonds by photosynthesis) is extracted and that energy is put into ATP, so that cells can use it for coupling to power other reactions.

cellular representation