Class Notes (806,820)
Canada (492,456)
Biology (6,676)

Summary 5-Cellular Respiration .doc

4 Pages
Unlock Document

Western University
Biology 1202B
Richard Gardiner

Cellular Respiration Summary • Cellular respiration – controlled mechanism of soring energy (rather than releasing as heat/light) ATP • Input of additional energy and a phosphate group “recharges” ADP to ATP Cellular Respiration • A catabolic, exergonic, oxygen requiring process that uses energy extracted from macromolecules (glucose) to produce energy (ATP) and water o Autotrophs: harvest sunlight to covert radiant energy into chemical energy  Plants, some bacteria and some protists o Heterotrophs: live off the energy produced by autotrophs (via digestion/catabolism)  Fungi, animals, some bacteria and some protists • Cellular respiration is opposite of photosynthesis (C6H 12+66O  62O + 6H 2 + 2 energy) Glucose Catabolism • Cells catabolize organism molecules/produce ATP in 2 ways: 1. Substrate-level phosphorylation – adding phosphate to a compound to energize it 2. Aerobic Respiration • In most organisms both are combined (glycolysis, pyruvate oxidation, Krebs cycle, ETC) Breakdown of Cellular Respiration (four main reactions) 1. Glycolysis (splitting of sugar) – cytosol, just outside of membrane 2. Grooming Phase – migration from cytosol to matrix 3. Krebs Cycle (Citric Acid Cycle) – mitochondrial matrix 4. ETC and Oxidative Phosphorylation (or chemiosmosis) – inner mitochondrial membrane Glycolysis • Ancient biochemical pathway that all organisms do (occurs in cytoplasm without oxygen) • Priming reactions – begins with addition of energy (2 high-energy phosphates from 2 molecules of ATP are added to glucose (6C) producing a 6C molecule with 2 phosphates • Cleavage reactions – 6C molecule with 2 phosphates is split, forming two 3C sugar phosphates • Energy Harvesting – each of the two 3C sugar phosphates is converted to pyruvate in a series of reactions while an energy-rich hydrogen is harvested as NADH and 2 ATP are formed • Recycling NADH – as long as food is available to be converted to glucose, ATP can be produced o Continual production creates NADH accumulation and NAD+ depletion  NADH must be recycled to NAD+ through aerobic respiration (oxygen as electron acceptor) or fermentation (organic molecule) • 2 Phases (10 steps) o Energy investment phase – preparatory phase (first 5 steps) Cellular Respiration Summary  2 ATP used (0 ATP or NADH produced) o Energy yielding phase – energy payoff phase (second 5 steps)  4 ATP and 2 NADH produced o Total Net Yield: 2 3C-pyruvate (PYR), 2 ATP (substrate-level phosphorylation) and 2 NADH • Substrate-Level Phosphorylation –enzyme transfers phosphate from substrate to ADP to form ATP • G3P – glyceraldehyde 3-phosphate or PGAL Citric Acid Cycle (Krebs Cycle) • Series of chemical reactions important to all living cells that use oxygen for cellular respiration Aerobic Metabolism (mitochondria) • Mitochondria oxidize glucose much more completely than in glycolysis • Mitochondria is found in almost all eukaryotic cells (abundant in active tissues like muscle/liver) Overview of Krebs Cycle • Metabolic pathway made up of series of enzymes in the mitochondrial matrix • Citrate is metabolized in a series of reactions that remove carbons along the way o Produces oxaloacetate (4C), NADH and ATP, and 2 molecule of CO 2 • Potential energy of glucose hydrocarbon bonds is transferred to NADH and ATP o This leaves the electrons in the C-O bond closer to O (more electronegative) but with a lower potential energy Transition Reactions (Pyruvate Oxidation) • Pyruvate is rearranged (COOH is removed as CO2), electrons are transferred to NAD+ forming NADH, Coenzyme A and acetate bind unstably (very reactive) o Acetyl CoA (molecule formed) is moved into mitochondria by facilitated transport o Another carbon is now oxidized and NADH is produced  Remember: 2 pyruvates/glucose, 2NADH + 2Acetely CoA/pyruvate, first 2 of 6 glucose carbons oxidized at this point Krebs Cycle • Some energy released by carbon oxidation converts ADP to ATP (substrate level phosphorylation) o Not much direct energy, but there are high energy electrons released that are used in ETC • NAD+  NADH release 3 molecule/cycle, FAD+  FADH2 release 1/cycle (oxygen not involved) • Steps of the Krebs Cycle 1
More Less

Related notes for Biology 1202B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.