ch. 9- cellular respiration ppt · chapter 9- cellular respiration. monday 11/27 • welcome back!...
TRANSCRIPT
Chapter 9- Cellular Respiration
Monday 11/27
• Welcome back!
• Test correction work day • Study tips!
• Paper pass back
Test Correction Format
1. Rewrite question 2. Write correct answer 3. Scientifically explain the right answer 4. Scientifically explain why your answer was
incorrect
CELLULAR RESPIRATION
−QUESTION: Why is breathing necessary?
ANSWER: We (heterotrophs) can't make our own food We must break down food made by autotrophs We use oxygen to release energy stored in those organic molecules
Types of Reactions• Catabolic reactions-
Break down substances • Ex. cellular
respiration
• Anabolic reactions- Build up substances
Types of Reactions
● Oxidation-Reduction Reactions (redox) − transfer of electrons from one reactant to another − because one substance loses the electron and
another gains it, redox reactions always go together
OIL RIG ● Oxidation is loss of e-
● Reduction is gain of e-
CELLULAR RESPIRATION
● occurs primarily in mitochondria ● catabolic process
organic cmpds. + oxygen --> carbon dioxide + water + energy C6H12O6 + O2 --> CO2 + H2O + ATP
● glucose is oxidized ● oxygen is reduced
Cellular Respiration
Some helpful hints: − when you think of electrons, think of hydrogen atoms − electrons start out with food, end up with oxygen
− Why oxygen??
− glucose is our example, but fats, proteins and other sugars work, too
CELLULAR RESPIRATION
● Some helpful hints: − electrons “fall” to oxygen step-by-step,
not all at once − ATP = energy − ATP can donate phosphate group so other
molecules can do work (ATP = ADP + Pi)
● Why is this process so in depth? − Energy must be harnessed in steps; too much
would be lost if occurred all at once
CELLULAR RESPIRATION
● Occurs in stages: 1. glycolysis 2. intermediate step (pyruvate oxidation) 3. Kreb's cycle/citric acid cycle 4. electron transport chain (ETC) & chemiosmosis
NAD+
● nicotinamide adenine dinucleotide (no, you do not need to know this!)
● derivative of niacin (vitamin) ● functions as electron acceptor/carrier ● becomes NADH (reduced)
● Gains H atom or electrons! (RIG)
NAD+ —> NADH
First process: Glycolysis
GLYCOLYSIS● “splitting sugar” ● catabolic process ● occurs in cytosol (cytoplasm) ● breaks down glucose (6C) into two molecules of
pyruvate (3C) ● occurs with or without oxygen ● uses 2 ATP ● produces 4 ATP (2 net ATP) and 2 NADH
Glycolysis
Substrate level phosphorylation • Phosphate transferred from substrate to ADP by
enzyme • Forms ATP • 4 created from glycolysis
ATP
GLYCOLYSIS
● IF oxygen is present, pyruvates and NADH can go on to generate more energy ----------->>> INTERMEDIATE STEP
Second process: Intermediate step (pyruvate oxidation)
INTERMEDIATE STEP (pyruvate oxidation)
● Junction between glycolysis and Kreb's cycle ● Occurs when pyruvates enter mitochondrial
membrane (matrix) ● Each pyruvate is converted to acetyl CoA
INTERMEDIATE STEP
● Process: 1. carboxyl group is removed and released as CO2 2. remaining molecule is oxidized; NAD+ becomes NADH 3. coenzyme A attaches to remaining molecule
● Benefits of this step??
Third process: Kreb’s/Citric Acid cycle
KREBS CYCLE
● also known as citric acid cycle ● occurs in mitochondrial matrix ● starts with acetyl CoA (2C) ● acetyl CoA (2C) combines with
oxaloacetate (4C) to make citrate (6C) ● eventually citrate (6C) is decomposed back to
oxaloacetate (4C) ● CO2 is released
KREBS CYCLE
● EACH acetyl CoA to go through produces: 1 ATP (substrate level phosphorylation) 3 NADH 1 FADH2 (electron carrier; INFO 2 CO2
x2 for a glucose molecule!!!
Fourth process: Electron transport chain (ETC) and chemiosmosis
ELECTRON TRANSPORT CHAIN
● Occurs in mitochondrial membrane (cristae) ● Does not directly make ATP
− Coupled with chemiosmosis to produce ATP ● Summary: electrons are transferred from one
molecule to another until reaching oxygen ● NADH inputs electrons at beginning of chain ● FADH2 inputs lower energy electrons at second complex
Molecules of the ETC
● Made up mostly of integral proteins − Exception = ubiquinone is
lipid ● Most are cytochromes
− Contain heme to transfer e-
ETC• As electrons are transferred from carriers, H+
ions pumped into inner membrane space • Effects on pH?
• Creates hydrogen ion gradient
Chemiosmosis
● Occurs in mitochondrial membrane ● Uses H+ gradient to power reaction of ADP + Pi
(CREATES ATP) ● Requires ATP synthase
= integral protein acting as enzyme
Oxidative Phosphorylation
● Coupling of ETC and chemiosmosis ● each NADH = 3 ATP ● each FADH2 = 2 ATP
Fermentation
● What happens if oxygen is not available? ● What becomes the final electron acceptor? ● What phases of cellular respiration still occur? ● How much ATP is produced? ● In what organisms does this commonly occur?