. In cells control the release of chemical-bond energy from organic molecules (such as glucose) through enzyme controlled chemical reactions
Plants must carry out both photosynthesis and cellular respiration. They can use the oxygen released from photosynthesis to run respiration?
Why can’t we just use glucose as a direct source of energy? Why do we have to convert it to ATP first? [Read the last paragraph on page 131]
Car bomb – lots of light, heat but over fast
ATP is nucleotide = adenine base +ribose + Phosphate group
In cells, transfer of chemical energy is handled by a single molecule called adenosine triphosphate (ATP). Like money, you have to make it before you can spend it! Phosphorylation impt mech for controlling activity of enzymes, other cellular proteins
Now we are going to move into cellular respiration Tell you a strange story to show you how concentration camps, cellular respiration and the scientific method are related… View of the Camp at Struthof with the Vosges mountains in the background. It should be noted that this photo depicts most of the buildings which were used to house the inmates - June 1953. Only CC built on French soil (Alsace) Courtesy Jacques Nadeau. The camp was opened in May 1941 The camp was evacuated by the SS in September 1944 as Allied troops approached. You have all heard of the atrocious conditions of the camps and know that most people lucky enough to be released or rescued from them were severely, chronically malnourished, many in a state of starvation. Allied troops liberated the camps throughout Europe, and the former prisoners were given food and medical care. However, a surprising number of these people died shortly after their rescue. Medical personnel were grieved and baffled. Why??? What was happening inside these people??? No one found the answer immediately, but the problem was investigated and eventually solved. After we talk more about cellular respiration, I will tell you how…
Remember we are breaking down glucose – oxidizing = removing electrons, therefore removing energy
Intricate, elegant system designed to extract the maximum energy from food! Carbon skeletons can be used for biosynthesis reactions in the cell
Water held back by dam has great potential energy and is eager to rush over the dam. This potential energy can be converted to useable energy by having the water turn turbines as it falls (kinetic energy) and generate electricity. In the cell, potential energy is generated by concentration gradient, and useful energy in the form of ATP can be made as the H+ travel down their concentration gradient (kinetic energy) through ATP synthase, a protein in the inner membrane.
Doesn’t work with Mac
1. The kinetic energy converted ADP ATP.
Draw on board. Remark at end about NADH from glycolysis only making 2/molecule
Glucose is phosphorylated when it enters cells (uses 2 ATP molecules) Lots of glucose, lots of ATP, lots of phosphate used Starved people had very low levels of phosphate in body Didn’t have enough phosphate to make ATP after cellular respiration – supplies were overwhelmed People died because they couldn’t make any more ATP, cellular processes came to a halt, starting with muscles. Cells died, burst, proteins in them overwhelmed kidneys, died of kidney failure. PHosphorus found in milk, meat, eggs, nuts, beans, peas
Many alcoholics malnourished because get most calories from EtOH. Frequently alcoholics come into hospital w/DT (withdrawal), liver probs (cirrhosis and infections), so medical personnel give them IV fluids, often with glucose included because they are malnourished. If they don’t include phosphate (usually potassium phosphate), same thing happens to them – muscle pain, kidney failure http://images.search.yahoo.com/images/view?back=http%3A%2F%2Fimages.search.yahoo.com%2Fsearch%2Fimages%3F_adv_prop%3Dimage%26fr%3Db1ie7%26va%3Dalcohol%26sz%3Dall&w=216&h=325&imgurl=www.okinawa.usmc.mil%2FPublic%2520Affairs%2520Info%2FImages%2520Complete%2FIMAGES%2F060519-alcohol.jpg&rurl=http%3A%2F%2Fwww.okinawa.usmc.mil%2FPublic%2520Affairs%2520Info%2FArchive%2520News%2520Pages%2F2006%2F060519-alcohol.html&size=70.7kB&name=060519-alcohol.jpg&p=alcohol&type=JPG&oid=66677796eddcd448&no=13&tt=1,237,000&sigr=1339j1uap&sigi=12op9u08a&sigb=12n68rilm
L.a. builds up during anaerobic exercise
Relationship of cell respiration and photosynthesis. Respiration releases chemical energy by using the reduction of O2 to water to drive the oxidation of sugar to carbon dioxide. Photosynthesis stores chemical energy by using the oxidation of water to O2 to drive the reduction of CO2 to sugar.
High-energy electrons, such as those made when light strikes a chlorophyll molecule, are passed from one carrier molecule to another along a chain, like a hot potato. Every time the electron is passed, some of its energy is released and can be used to build an ATP. There is a stepwise passage of energy from molecule to molecule. Some of this bond energy is put into the ATP bond. The rest of this energy is released as heat.
Cellular RespirationReleasing Chemical Energy Chapter 6
BIOCHEMICAL REACTIONS• All living organisms require a constant supply of energy to sustain life.• Cellular respiration - the chemical energy stored in glucose is converted into a more usable form – ATP – Requires the presence of oxygen and the correct enzymes – Carbon dioxide, water and heat are also released as by-products of this reaction.C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat)glucose + oxygen → carbon + water + energy dioxide
Why Cell “Respiration”?2. This process requires oxygen, which is supplied by breathing3. The mechanical movement of air or water through the lungs/gills is often referred to as ventilation to distinguish it from respiration.4. What about plants?
• Cellular respiration – slow, controlled release of energy (max. harvest of energy from food)
Review of ATP• ATP is the “energy currency/rechargeable batteries” of cells• When energy is harvested from a chemical reaction or sunlight, it is stored when a phosphate group is attached to an ADP to form ATP. – Called phosphorylation
• When the ATP is broken back down to ADP, stored chemical energy is released to do work in a cell – Called dephosphorylation – Some energy is lost as heat
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat)glucose + oxygen → carbon + water + energy dioxide
OXIDATION REACTIONS• Oxidation begins in the cytoplasm and is completed in the mitochondria• 3 parts to cellular respiration (each an enzyme-controlled pathway) – Glycolysis – Krebs cycle – Electron transport system
1. Glycolysis - a 6C glucose molecule is broken into 2 3C molecules of pyruvate (pyruvic acid) a. Occurs in the cytoplasm of the cell – near the mitochondria b. Yields: + 2 ATP (4 ATP – 2ATP - used to phosphorylate glucose when it enters cell) + 2 NADH (NAD+ is reduced to NADH) c. This process is anaerobic (without oxygen)…can happen even if there is an insufficient O2 level to carry out the rest of cellular respiration
If there is O2 present, respiration continues. Each 3C pyruvate will…2. Lose atoms of carbon and oxygen – CO2 released (…it is now called an acetyl group)4. Join to a molecule of coenzyme A (which is a B vitamin) – Acetyl CoA - CoA acts as a shuttle, carrying acetyl groups3. NAD+ (coenzyme that shuttles around hydrogen and electrons) is reduced to NADH.4. These reactions are often called the ‘Intermediate Reactions’
2. Kreb’s Cycle (Citric Acid Cycle) a. Acetyl CoA enters the mitochondrion and 2C acetyl group bonds to a 4C compound (oxaloacetate) to form a 6C compound called Citric Acid (citrate)
b. The 6C compound is broken down to a 5C compound 1 CO2 is produced 1 NAD+ is reduced to NADH
c. 5C compound is broken down into a 4C compound 1 CO2 is produced 1 NAD+ is reduced to NADHd. Oxaloacetate is regenerated (4C 4C)This yields: 1 ATP (ADP ATP) 1 FADH2 (FAD FADH2) 1 NADH (NAD+ NADH)
e. So, the total yield of just the Kreb’s cycle is: 2 ATP 6 NADH 2 FADH2 per glucose
3. Electron transport system (ETS) makes ATP a. Electrons from reduced coenzymes NADH and FADH2 are transferred through a series of redox reactions until the electrons are accepted by oxygen to make water.
b. Mitochondrial structure 1) Double membrane- bound organelle 2) Inner membrane folded into christae a) Increase surface area for reactions b) ETS located here • Intermembrane space • Matrix - Kreb’s cycle
c. ATP synthesis 1. H atoms from coenzymes dropped off at ETS (inner membrane) 2. H atoms split into a proton (H+) and an electron (e-) - Electrons go through ETS - Energy from electrons is used to pump the H+ out into the intermembrane space 3. H+ concentration in this space increases 4. The H+ RUSH back into the matrix (because of concentration gradient) through an H+ channel (ATP synthetase complex) making ATP 5. Called chemiosmosis
d. Happy endings… 1. H+ and e- (now low energy) are rejoined 2. H atoms bond to available oxygen atoms and form water: H+ + e - + O2 H2O This is why you breathe!! The O2 is merely a hydrogen dump! O2 allows the continual movement of H+ through the ATP synthetase No O2, no rushing H+ movement, no ATP, no life!
e. ETS produces: (per glucose) 2 NADH (from glycolysis) 2 NADH (from intermediate reactions) + 6 NADH (Krebs cycle)______________ 10 NADH x 3 ATP/NADH = 30 ATP 2 FADH2 x 2 ATP/ FADH2 = 4 ATP____ for a total 34 ATP/glucose from ETS
Cellular Respiration Energy Summary34 ATP/glucose from ETS +2 ATP (glycolysis) +2 ATP (Krebs cycle)_______________ 38 ATP per glucose!!!
• Other nutrients can be used for energy – Lipids fatty acids, enter Krebs Cycle – Proteins amino acids • NH3 removed urea • Carbon portions enter Krebs Cycle as oxaloacetate – Carbon skeletons can be used for biosynthesis of amino acids, nucleic acids and fatty acids
Alternatives to Aerobic RespirationWhat if there’s not enough oxygen?
Glycolysis still happens (since it’s anaerobic anyway…). - Yield is 2 ATP + 2 NADH + 2 pyruvic acid (3 C molecule). - Fate of the pyruvic acid depends on what type of organism you are…
If you are a plant or yeast cell…Pyruvic acid will become ETHANOL in a process called alcoholic fermentation.
If you are a bacterial cell… Your pyruvic acid can be fermented to vinegar or to start the process of cheesemaking.
If you are an animal cell…Your pyruvic acid becomes LACTIC ACID in a process called lactic acid fermentation.
Photosynthesis and Cellular Respiration• Cellular respiration and photosynthesis share several features: – They are enzyme-controlled biochemical pathways. – They make use of ATP for energy transfer – They use an Electron Transport System to help make ATP.
CELLULAR RESPIRATION• Breakdown of glucose molecules in the presence of oxygen.• The oxidation of glucose (by many enzymes) results in carbon dioxide and water.C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat) glucose + oxygen → carbon + water + energy dioxide
A Definition of Cellular RespirationThe energy stored in glucose (with the presence of oxygen and the correct enzymes) is converted into a more usable form – ATP. Carbon dioxide and water are also released as by-products of this reaction.C6H12O6 + 6 O2 6 CO2 + 6 H2O + ATP[Read the last paragraph on page 131]
GLYCOLYSIS• Glucose (6 carbons) is broken into two 3 carbon molecules called pyruvate (pyruvic acid).• This makes enough energy to make 2 ATP molecules.• In addition, an NADH molecule is also made and transferred to the electron transport chain.
3. Electron transport system (ETS), located in the membranes of mitochondria (and chloroplasts) makes ATP. – High-energy electrons are passed stepwise through a series of oxidation- reduction reactions from one carrier molecule to another. • Every time the electron is passed, some of its energy is released and can be used to make ATP • The rest of the energy is released as heat
How much energy do you get from 1 molecule of glucose?Glycolysis – 2ATP and 2 NADH (each x3)Intermediate – 2 NADH (each x3)Kreb’s Cycle – 2 ATP, 6 NADH (each x3), and 2 FADH2 (each x2)The ETS yields 8 ATP from glycolysis, 6 ATP from the Intermediate Reactions, 24 ATP from the Kreb’s CycleFor a total of…38 ATP per initial molecule of glucose
Throughout the process, coenzymesare being reduced so, in the end, they can all be oxidized (so ATP can be generated!) – sort of like POKER!
CELLULAR RESPIRATION SUMMARY• Glucose is broken down to carbon dioxide and water, making 4 ATPs directly and another 32 ATP via the electron transport system.