Ch. 4: Cellular Respiration Flashcards
First law of thermodynamics
total amt. of energy in the universe remains constant –> energy is neither created nor destroyed, only converted to kinetic/ potential energy
Second law of thermodynamics
some energy is “lost” (unable to do work) in the form of heat when energy changes state
entropy is constantly increasing
Gibbs free energy/ Exergonic/ Endergonic
energy in a system that is available for conversions, change is ΔG
-ΔG means net loss of free energy (rxn gives off energy) and rxn is exergonic
+ΔG means net gain in free energy (energy added for rxn to occur) and rxn is endergonic –> most metabolic rxns
Why can’t photosynthesis occur spontaneously?
it is an endergonic rxn so energy in amt. of at least ΔG must be provided (sunlight)
Activation energy
energy needed for rxn to occur, reactants pass intermediate state. only if this energy is provided will an exergonic rxn occur spontaneously
catalyst speeds up chem. rxn by lowering activation energy
How do metabolic rxns get their energy?
ATP is hydrolyzed to ADP
2 processes that provide free energy (allow cells to maintain order, minimize entropy and remain alive)
Photosynthesis: energy from sun –> carbs
Respiration: extracting energy from those carbs
Phosphorylation
adding energy and an inorganic phosphate to ADP to make ATP
Ex. substrate level, oxydative
Substrate level phosphorylation
phosphate group and its energy transferred to ADP to form ATP. the substrate molecule donates high energy phosphate group
Ex. glycolysis
Oxidative phosphorylation
process of producing ATP from NADH and FADH2 in ETC
phosphate group added to ADP to form ATP but energy of bond doesn’t come w/ phosphate. instead, e- give up energy to make ATP during ETC
last step in aerobic respiration
Cellular respiration
ATP is generated from energy-rich glucose for energy
C6H12O6+6O2–>6CO2+6H20
Aerobic respiration steps
happens when oxygen is available
- Glycolysis
- Krebs Cycle (Citric Acid Cycle)
- Oxidative Phosphorylation
Anaerobic respiration types
- Alcohol fermentation
2. Lactic acid fermentation
Glycolysis
decomposition of glucose to pyruvate
- 2 ATP added
- 2 NADH produced
- 4 ATP produced by substrate level phosphorylation
- 2 pyruvate formed
summary: takes 1 glucose and turns it into 2 pyruvate, 2 NADH, and a net of 2 ATP (actually 4 ATP but use 2). occurs in cytosol
NADH
coenzyme
energy rich molecule
e- carrier when NAD+ combines w/ 2 energy rich electrons and H+ (obtained from intermediate molecule during glucose breakdown)
Krebs cycle
processing of pyruvate after glycolysis
- In cytosol, pyruvate + CoA –> acetyl CoA; 1 NADH and 1 CO2 produced
- Krebs Cycle: acetyl CoA + OAA (oxaloacetate) –> citrate; 7 intermediate products: 3 NADH and 1 FADH2, 1 ATP, 2 CO2 released (CO2 made in Krebs is what animals exhale)
Electron Transport Chain (ETC)
part of oxidative phosphorylation
e- from NADH and FADH2 pass along ETC consisting of proteins that pass e- from one carrier to the next like cytochromes. along each step of chain, e- give up energy used to phosphorylate ADP to ATP (NADH 3 ATP, FADH2 2 ATP). last e- acceptor is oxygen which accepts 2 e- and combines w/ 2H+ to form water
Cytochrome c
a carrier protein in the ETC which includes nonprotein parts like iron
present in lots organisms so this protein often compared among species to assess genetic relatedness
Where does the Krebs Cycle and Oxidative Phosphorylation take place?
Mitochondria
Outer membrane of Mitochondria
like plasma membrane, consists of double layer of phospholipids
Intermembrane space of Mitochondria
narrow area between inner and outer membranes
H+ ions (protons) accumulate here
Inner membrane of Mitochondria
double phospholipid bilayer w/ cristae
oxidative phosphorylation occurs here (ETC of protein complexes removes e- from NADH and FADH2 and transports H+ ions from matrix to intermembrane space)
ATP synthase found here: phosphorylation of ADP –> ATP
Mitochondrial Matrix
fluid material that fills the area inside the inner membrane
Krebs Cycle and conversion of pyruvate to acetyl CoA occurs here
Chemiosmosis (general)
mechanism of ATP generation that occurs when energy is stored in the form of a proton concentration gradient across a membrane
Chemiosmosis in Mitochondria
- Krebs Cycle produces NADH and FADH2 in the matrix (CO2 is made and substrate-level phosphorylation occurs to produce ATP)
- Electrons are removed from NADH and FADH2 (e- move along ETC)
- H+ ions are transported from the matrix to the intermembrane space
- A pH and electrical gradient across the inner membrane is created (potential energy reserve)
- ATP synthase generates ATP (protons move in direction of their concentration gradient, and ATP synthase turns ADP into ATP)
Theoretical vs. Actual amount of ATP created by aerobic respiration
36 theoretical, actual around 30
Anaerobic Respiration
goal is to replenish NAD+ so glycolysis can happen; occurs in cytosol alongside glycolysis
if oxygen not present, no e- acceptor exists to accept at end of ETC… NADH accumulates bc NAD+ –> NADH but Krebs and glycolysis both stop bc need NAD+ to accept e- so no ATP produced … DEATH
ex. alcoholic fermentation and lactic acid fermentation
Alcohol Fermentation
goal to replenish NAD+ for glycolysis
occurs in plants, fungi (yeast) and bacteria
Pyruvate –> acetylaldehyde –> ethanol
for each pyruvate, 1 CO2 (carbonation in beer) and 1 acetylaldehyde are produced; for each acetylaldehyde, 1 ethanol (alcohol in beer) and 1 NAD+ are made using energy from NADH
result: 2 ATP from glycolysis
Lactic Acid Fermentation
pyruvate –> lactate (lactic acid)
in this process, NADH gives up its e- to form NAD+ which can now be used in glycolisis
most lactate is transported to liver, where it is converted back to glucose when more ATP is available
