Biology Unit 1: Part 5

Cell metabolism: respiration

ATP

adenosine triphosphate, “energy currency”

Redox reaction

energy in reducing agent is transferred to the reduced product

Oxidation

loss of one or more electrons (H), exergonic

Reduction

gain of one or more electrons (H), endergonic

Reducing agent becomes ____ in a redox reaction

the oxidized product (because it gave up its electron to reduce another compound)

Oxidizing agent becomes ____ in a redox reaction

the reduced product (because it accepted an electron from another compound to oxidize it)

Most reduced state → most oxidized state

Highest free energy → lowest free energy

NAD+

key electron carrier, oxidized form

NADH

key electron carrier, reduced form

Reduction of NAD+

highly endergonic, adds a H and 2 electrons = NADH

Oxidation of NADH

highly exergonic, = NAD+

Cellular respiration, glucose oxidized

carbohydrate + 6 O2 = 6 CO2 + 6 H2O + chemical energy

4 Steps of cellular respiration (oxidation of molecules to CO2 + H2O)

glycolysis, pyruvate oxidation, citric acid cycle, electron transport system

Glycolysis

ten reactions, takes place in cytosol, = 2 molecules of pyruvate + 2 net ATP + 2 NADH

Glucose + ADP + ATP + NAD+ → 2 pyruvate + 2 ATP + 2 NADH

Inputs and outputs of glycolysis

Pyruvate oxidation

occurs inside mitochondrial matrix = CO2 + Acetyl CoA (binded coenzyme A and acetate) + NADH

2 pyruvates + coenzyme A + NAD+ → acetyl CoA + NADH + CO2

Inputs and outputs of pyruvate oxidation

Anaerobic forms of metabolism

lactic acid fermentation, alcoholic fermentation, less efficient

Lactic acid fermentation

glucose → 2 pyruvate + 2 ATP + 2 NADH → 2 lactic acid (lactate) + NAD+: NAD+ and NADH cycle allows it to be cyclic

Alcoholic fermentation

glucose → 2 pyruvate + 2 ATP + 2 NADH→ 2 acetaldehyde + 2 + ethanol + 2 NAD+: NAD+ and NADH cycle allows it to be cyclic

Citric acid cycle

8 reactions, operates twice for every glucose. Acetyl CoA → CO2 + 4NADH + ATP + oxaloacetate

FAD + NAD+ + acetyl CoA + oxaloacetate → FADH2 + NADH + ATP + CO2 + oxaloacetate

Inputs and outputs of citric acid cycle

Citric acid cycle ____ Acetyl CoA into ____

oxidizes, CO2

Citric acid cycle ____ NAD+ into ____

reduces, NADH

Electron transport system

inside mitochondrial membrane, carries out oxidative phosphorylation to produce ATP through chemiosmosis, oxidizes O2 into H2O

Oxidative phosphorylation

transfers energy from NADH to ATP; the oxidation of NADH provides energy to synthesize ADP into ATP, how most of the ATP is produced

O2 + NADH + FADH + ADP → ATP + H2O + NAD+ + FAD

Inputs and outputs of oxidative phosphorylation

Chemiosmosis

diffusion of protons across a membrane

Chemiosmosis function and where it takes place

drives synthesis of ATP through the proton motive force, takes place in mitochondria

How proton gradient set up

energy from oxidation reactions (NAD+ → NADH) in citric acid cycle used to actively transport H+ ions out of mitochondrial matrix and create gradient

2 functions of O2

oxidative phosphorylation for ATP synthesis, and final electron receptor to create H2O

Substrate level phosphorylation

ADP → ATP during glycolysis, phosphate group carried to ADP to create ATP by enzyme, takes place in cell cytoplasm; does not require O2, proton gradient, or membrane pump