Cellular respiration Workshop
Key points regarding the following processes
1.Glycolysis
2.Krebs cycle
3.Oxidative phosphorylation
The purpose of cellular respiration
Provide the cell with energy in the form of ATP (Adenosine Tri-Phosphate)
ATP is a temporary energy store
When bonds break they release energy, and it is this energy that drives the cell’s
processes.
ATP----> ADP + iP (inorganic phosphate) + energy
The overall reaction
C6H12O6 + 6 O2 + 38 ADP +38 Pi →
6 CO2 + 6H20 + 38 ATP
2 types of cellular respiration
Aerobic respiration – uses oxygen (like when
you do aerobic exercises you use a lot of
oxygen – breath hard during running)
●Anaerobic respiration- does not use oxygen less
(ATP) produced
●Reduction – loss of electron
●Oxidation – gain of electron
●
Glycolysis
The hormone insulin signals to the cell’s plasma membrane to transport
glucose into the cell
●Glycolysis means the breakdown of the glucose molecule
●Glucose contains 6 carbons C6H12O6
●The process breaks glucose down into 2 molecules of Pyruvate
●Pyruvate is the ionized form of pyruvic acid
●Each molecule of pyruvate contains 3 carbons
●Ion = electrically charged atom or molecule
●Anion = negative charged atom
●Cation = positively charged atom
●
Glycolysis
This process occurs in the cytosol
●This process does not require oxygen and produces no CO2
●Produces 4 molecules of ATP
●However 2 ATP are used so only 2 of the original 4 are made available to the cell
●the process also produces
● 2 NADH + 2 H+
●NAD+ is a co-enzyme that becomes reduced
●Reduction is the addition of an electron to a molecule
●Most of the electrons from glucose are initially transferred to NAD+
●Glucose has hydrogen and the hydrogen gives up electrons to NAD+
●2 H = 2e- + 2H+
●2 NAD+ + 4 e- + 4 H+ → 2 NADH + 2 H+
●
●
GLYCOLYSIS
The overall reaction
●Glucose + 2 NAD+ +2ADP + 2Pi →
●2 pyruvate + 2 NADH + 2 H+ + 2 ATP
●Lets break it down looking at which reactants become which
products
●In this overview we will ignore H2O
●
Glucose → 2 pyruvate
●4 ATP – 2 ATP used → 2 ATP or
●2 ADP + 2 Pi → 2 ATP
●2 NAD+ + 4 e- + 4 H+ → 2 NADH + 2 H+
●
The linking step
Occurs in the mitochondria- pyruvate can only enter the mitochondria in the
presence of oxygen
●The linking step turns pyruvate into Acetyl Co-enzyme A so it can enter the
krebs cycle
●The two pyruvate from glycolysis continue to the linking step that converts
each molecule into Acetyl Co-enzyme A
●2 pyruvate -→ 2 Acetyl Co-enzyme A
●This step also produces → 2NADH + 2 H+
●In addition the linking step produces 2 CO2
●The CO2 lost is a result of the carboxl groups ( --COO-) which is already fully
oxidized and has little energy is removed from pyruvate and given off as a
molecule of CO2
●
The linking step
Pyruvate is turned into acetyl coA, in the
process giving off a CO2
●This means that the resulting molecule of acetyl coA only
●
has 2 carbons as it enters the krebs cycle
●COO- (carboxl group) is an anion, it becomes oxidized to form
CO2
Krebs Cycle
The krebs cycle is also refered to as the citric acid cycle or the
tricarboxylic acid cycle
●The 2 Acetyl Co-enzyme A produced during the linking step can
now enter the Krebs cycle
●Each revolution of the krebs cycle is commonly referred to as
one spin
●1 glucose → 2 pyruvate → 2 Acetyl CoA
●Each acetyl coA participates in one revolution of the krebs cycle
●So the krebs cycle spins twice for each glucose
●
Krebs Cycle
The krebs cycle occurs in the mitochondrial matrix
●One spin produces 2 CO2 however uses no oxygen, so 4 for each glucose
●One spin produces 1 ATP, so 2 for each glucose
●3 NADH and 1 FADH2 are produced per spin, so 6 NADH and 2 FADH2
●
This accounts for 8 of 12 reduced co-enzymes from the krebs cycle
●However there where 2 NADH produced during the linking step, so that
brings the total to 10 of 12 reduced co-enzymes
●The other 2 co-enzymes are 2 NADH that came from glycolysis bringing the
total to 12 reduced co-enzymes
●10 NADH and 2 FADH2
●
KREBS CYCLE
The overall reaction for the krebs cycle
including the linking step
●
2 pyruvate + 8 NAD+ + 2 FAD + 2 ADP + 2 Pi + 6 H2O →
●6 CO2 + 8 NADH + 8 H+ + 2 FADH2 + 2 ATP
●The purpose of the krebs cycle is to take glucose from the food we eat that
has been modified by glycolysis and the linking step and oxidize it. Which
basically means steal the electrons. Once the electrons have been removed
from acetyl coA they are donated to NAD+ and FAD. Addition of electrons is
termed reduction. That is why it is said that the krebs cycle produces 10 out
of 12 reduced co-enzymes
●
Oxidative Phosphorylation
Occurs within the inner mitochondrial matrix
●Involves 2 processes simultaneously
●1. Electron transport chain
●2. Chemiosmotic coupling
●Chemiosmosis means energy stored in a
hydrogen concentration gradient across a
membrane is used to perform work for the cell,
in this case synthesis of ATP
●
Oxidative Phosphorylation
This process requires oxygen
●During the krebs cycle NAD+ and FAD where reduced (electrons
where added to them)
●Now they will donate their electron to the electron transport
chain (oxidation)
●The electron transport chain is a series of proteins located in
the inner mitochondrial membrane
●These proteins include iron sulfur proteins, co-enzyme q and
cytochromes
●NADH donates its electron to FMN (Flavin Mono-Nucleotide)
●FADH2 donates its electron to coenzyme Q
●
Electron transport chain
NADH and FADH2 give up their electrons to a
component of the electron transport chain.
Then these electrons are passed to the next
component of the chain.
●Each time an electron is passed from one
component to the next they lose some energy
●This energy is used to move hydrogen ions
against their concentration gradient into the
intermembrane space
●
The last protein in the chain is cytochrome a3
●once the electrons reach cytochrome a3 they react with
hydrogen ions to form hydrogen
●hydrogen then reacts with oxygen to form water
●-e + H+ = hydrogen
●oxygen is the ultimate electron acceptor
●it is very important for oxygen to be present
●without oxygen the electrons have nowhere to go, and the
electron transport chain becomes overwhelmed.
●
Chemiosmotic coupling
This process produces the ATP
●Each time an electron moves from one component of the
electron transport chain to the next, energy is released
●This energy is used to more hydrogens against their
concentration gradient, from the matrix to the intermembrane
space of the mitochondria.
●This process requires energy because the hydrogen ions are
moving against their concentration gradient.
●Once the hydrogen ions have been moved to the
intermembrane space they can move down their concentration
gradient.
●
DO NOT CLOSE THIS PLEASE
When a molecule moves down its concentration
gradient it does not require energy
The hydrogen ions move from the
intermembrane space to the matrix through a
protein called ATP synthase.
ATP synthase is an enzyme located in the inner
mitochondrial membrane