Download Cellular Respiration

Cellular Respiration:
The Release of Energy in Cells
Cellular Respiration
Cells need energy
to carry out
activities
•Muscles need
energy to contract
(or to relax)
•Neurons need
energy to transmit
impulses
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Where does a cell
get energy?
A: From molecules
absorbed in digestion;
One in particular-- glucose
Cells obtain energy by breaking the chemical
bonds of glucose
Covalent bonds between atoms = stored energy
How much energy is
in one molecule of
glucose?
One glucose molecule
gives 38 ATP molecules
Cellular respiration = Energy Conversion:
Chemical energy  Chemical energy
(bonds of glucose)
(bonds of ATP)
What is ATP?
ATP is
•
Adenosine Tri Phosphate
•
A molecule that serves as an energy
carrier in cells
•
Transported to wherever energy is
needed to perform reactions in cell
•
Carries energy in useable amounts
What is ATP?
Adenosine
Diphosphate
ADP
ATP
Triphosphate
How Does ATP
Store and Release
Energy?
Storage of energy
ADP + Phosphate  ATP
Adding one phosphate
group to ADP creates ATP
Energy is stored in the new
bond
How Does ATP
Store and Release
Energy?
Release of energy for use by the cell
ATP  ADP +Phosphate
Removing one phosphate
group from ATP makes ADP
Energy is released for the
cell to use
ATP Production
For aerobic
respiration:
(requires oxygen)
ATP
production
begins in the
cytoplasm
It ends in the
mitochondria
The Reaction
Glucose + Oxygen + 38 ADP
yields
Carbon Dioxide + Water + 38 ATP
Reactants
Products
C6H12O6 +O2 + 38ADP + 38Pi
CO2 + H2O + 38 ATP
Pi = inorganic phosphate
ATP Production
The breakdown of glucose is an
Oxidation-Reduction reaction
Oxidation - the removal of hydrogen atoms
from a molecule
Reduction - the addition of hydrogen atoms to
a molecule
(an electron is transferred too hence the “reduction”)
oxidation
C6H12O6 + 6 O2 + 38 ADP
6 CO2 + 6 H2O + 38 ATP
reduction
What else is needed?
The supporting cast for
Cellular Respiration includes:
• Enzymes
(too numerous to name)
• Coenzymes –
Two require special mention:
•NAD+
•FAD+
(nicotinamide adenine dinucleotide if you must know)
(flavine adenine dinucleotide)
NAD+ and FAD+ receive the hydrogen atoms removed
from glucose and become NADH and FADH2
Glucose Oxidation
Four phases:
Glycolysis
glucose (6 C) splits into two 3-carbon molecules
Preparatory reaction
each 3-carbon molecule divides into a 2-carbon
molecule and CO2
Citric acid cycle (or Krebs cycle)
CO2, NADH, FADH2, and ATP produced
Electron transport chain
Assists in the production of the largest
amount of ATP
Glucose Breakdown
Thanks go to the following locations for
hosting the reactions:
Cytoplasm - Glycolysis
Mitochondria Matrix: Preparatory Reaction and Citric Acid Cycle
Cristae (folds): Electron Transport Chain
Act I: Glycolysis
A metabolic pathway occurring in the cytoplasm
During glycolysis, glucose (a 6-carbon molecule) is
broken down to two pyruvate (3-carbon) molecules.
Glucose (6 C)  2 Pyruvate (3 C)
No oxygen is required for this phase
reactants
Net gain of ATP
products
Glycolysis
Two ATP are used to
begin the reaction
NADH is made from NAD
Four ATP are Produced
(NET of 2 ATP)
Act II: Preparatory
Reaction
Scene 1: Pyruvate from glycolysis enters the
mitochondria matrix
Scene 2: Pyruvate (C3) is oxidized into
an acetyl group (C2) + CO2
Scene 3: NAD+ + H  NADH
Scene 4: The acetyl group is attached to coenzyme A
producing acetyl CoA
Act 2: Preparatory
Reaction
Act III:
Citric Acid
Cycle
Setting:
mitochondria
matrix.
Acetyl CoA gives up
the acetyl group to a
4 Carbon molecule
4 NADH, 6 FADH2,
2 CO2 and 2 ATP
are produced
Krebs
Cycle
reactants
products
Act IV: Electron
Transport Chain
Setting: on the cristae of the mitochondria
Each NADH is converted to 3 ATPs
2 from glycolysis, 2 from preparatory reaction, 6 from Krebs cycle
10 x 3 = 30
Each FADH2 is converted to 2 ATPs
2x2=4
A total of 34 ATP’s will be produced in this step
How Does the
Electron Transport
Chain Work?
A Concentration Gradient
of H+ is created across
the membrane of the
mitochondria
The H+ ions are then
allowed to diffuse
back across the
membrane turning an
ATP generator
Intermembrane
space
High energy electrons are
released by NADH or FADH2
transported from carrier to carrier in the membrane
handed off to - O2 the final electron carrier!!!
(this is the aerobic part)
The oxygen combines with H+ to make - (ta da!) Water
H+ (from NADH and FADH2) is pumped to the intermembrane space
The concentration gradient of H+ will be used to produce ATP
Passive transport (diffusion) generates energy and activates
ATP synthase for ATP synthesis
The End Results :
The Recap:
anaerobic
aerobic
But What if There is
No Oxygen?
Glycolysis will still occur (it’s anaerobic)
Only 2 ATPs will be generated for each
molecule of Glucose
The glucose will be further broken down by
fermentation
Fermentation does not generate more ATP
Anaerobic Respiration
Lactic Acid Fermentation:
Glucose + 2 ADP  Lactic Acid + 2 ATP
Occurs:
•In certain bacteria
•Human muscle cells:
•when used strenuously, not enough O2 can be supplied
•cells switch from aerobic to anaerobic to keep working;
lactic acid buildup causes fatigue, cramps
Anaerobic respiration
Alcoholic fermentation:
Glucose + 2 ADP  Ethyl alcohol + CO2 + 2 ATP
Performed by yeasts (kind of fungi) in bread making,
alcohol brewing
The Encore:
What are the different steps of cellular respiration?
Glycolysis
Preparatory Reactions
Citric Acid Cycle
Electron Transport Chain
The Encore:
Where does each step take place?
Cytoplasm:
Glycolysis
Mitochondria Matrix:
Preparatory Reactions
Citric Acid Cycle
Mitochondria Cristae:
Electron Transport Chain
The Encore:
What are the reactants and products of each step?
Stage
Reactants
Products
Glycolysis
Glucose, 2 ATP, 4
ADP, NAD +
Pyruvate, 4ATP,
NADH
Preparatory Pyruvate, NAD, CoA Acetyl CoA, CO2,
Reaction
NADH
Citric Acid
Cycle
Acetyl CoA, NAD,
FAD+, ADP
CO2, NADH,
FADH2, 2 ATP
Electron
Transport
NADH, FADH2, O2
H2O, 34 ATP
The Encore:
How many ATP molecules are produced in each
step?
Glycolysis
Net 2
Preparatory Reactions
0
Citric Acid Cycle
2 ATP
Electron Transport Chain
34 ATP
The Encore:
What is the difference between
aerobic and anaerobic respiration?
Aerobic
Oxygen
ATP Produced
Needs
38
Anaerobic
Does not need
2
Processing
More steps
Faster energy
End products
CO2 + H2O
Lactic acid or
alcohol and CO2
Location
Cytoplasm &
Mitochondria
Cytoplasm