Cell Respiration Outline | Date:
Mitochondrion

Structure
o Double membrane
o Cristae
o Matrix
Catabolic Pathways

Fermentation

Cellular respiration
o Aerobic respiration
Cellular Respiration Equation

Glucose

Equation

Exergonic

Occurs in all eukaryotes and some bacteria
ATP

ATP-ADP Cycle
Photosynthesis
Starting Molecules

Proteins and fats
Cell Respiration
o Potential cell damage

Phosphofructokinase (PFK) as an allosteric enzyme
Electron-Carrying Molecules

NAD and FAD
o Vitamins
o NAD+ = nicotinamide adenine dinucleotide
o FAD = flavin adenine dinucleotide
o Coenzymes
Oxidation-Reduction Reactions

Oxidation

Reduction
Cellular Respiration

Overview
o Electrons are stripped from glucose at key steps

NADH and FADH2
o Why so many steps?

3 Steps
o Glycolysis

Occurs in cytosol

Glucose  2 pyruvate (pyruvic acid)

Glycolysis = “sugar splitting”

Overall reaction

Two steps

ATP-consuming phase
o 2 ATP consumed

ATP-producing phase
o 4 ATP, 2 NADH, 2 pyruvates produced

Net gain of 2 ATP and 2 NADH
o Transition Step – Acetyl CoA

Pyruvate is oxidized to acetyl CoA

Pyruvate moves to mitochondrial matrix

CO2 and electrons are removed from pyruvate

Coenzyme A is added to form acetyl CoA

2 acetyl CoA are made per glucose
o Krebs Cycle (Citric Acid Cycle)

Occurs in mitochondrial matrix

Completes glucose breakdown

Releases CO2 as waste

Each turn of the cycle requires one acetyl CoA – must make 2 turns before glucose is
completely oxidized

Each turn produces 2 CO2, 3 NADH, 1 FADH2, 1 ATP

This makes a total of 4 CO2, 6 NADH, 2 FADH2, and 2 ATP

By the end of this cycle, all 6 original carbons in glucose are released as CO2

Only 2 ATP are produced – where is all the energy?
o Electron Transport Chain

Occurs in inner mitochondrial membrane

Consists of a series of proteins through which electrons pass – each time they are passed,
they give off a little energy

NADH and FADH2 drop off electrons

As electrons move, H+ ions are pumped to one side of the membrane

H+ ions diffuse through ATP synthase to convert ADP  ATP (chemiosmosis, or
the proton-motive force)

Oxygen is the final electron acceptor at the end of the electron transport chain – H+ and
electrons join O2 to form water.
o Total ATP yield: 30 – 32 ATP
Process
Location
Type of
Phosphorylation
FADH2
produced
NADH
produced
ATP
Yield
=
=
=
=
=
=
=
Theoretical yield of ATP:
Actual yield:
Why is it different?
Efficiency

Cell respiration is incredibly efficient

40% of energy in this process is converted to ATP
o This is very high – what happens to the rest of the energy?
Aerobic and Anaerobic Metabolism

Aerobic metabolism
o Mitochondria
o Oxygen reaches cells, provides maximum energy production
o Includes Krebs cycle and oxidative phosphorylation (electron transport chain)

Anaerobic metabolism
o Cytoplasm
o Demand for oxygen outweighs ability to receive it, low energy production
o Glycolysis occurs repeatedly
o By certain prokaryotes – generates ATP without O2 using an ETC
o Fermentation

Glycolysis and reactions that regenerate NAD+

O2 is not needed to accept electrons – NAD+ is the electron acceptor, so fermentation
pathways must regenerate it

Types

Alcoholic fermentation
o Pyruvate  acetaldehyde and CO2  ethanol and 1 NAD+
o Releases CO2, makes more NAD+, makes 2 ATP
o Occurs in…
o Uses

Lactic acid fermentation
o Pyruvate  lactate + NADH
o 2 ATP made
o Occurs in…
o Uses


Types of anaerobic organisms

Facultative anaerobes

Obligate anaerobes
Evolution of glycolysis

How do we know glycolysis evolved early?