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Cellular Cellular RespirationRespiration
ObjectivesObjectivesObjectivesObjectives
3.6.0 – Introduction to metabolism (review)
3.6.1 – Review enzyme kinetics and ATP production.
3.7.1 – Define cell respiration
3.7.2 – State that, in cell respiration, glucose in the cytoplasm is broken down by
glycolysis into pyruvate, with a small yield of ATP.
3.7.3 – Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismEnergy needs of living things
AutotrophsGet energy from the sun or chemicalsProducers
HeterotrophsGet energy from consuming foodConsumers
HerbivoresCarnivoresDetritivores
SaprotrophsGet energy from consuming dead materialDecomposers
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolism
Metabolism is the sum of chemical reactions in a body.Metabolic pathways alter molecules in a series of steps.
Catabolic pathways release energy by breaking down complex mole- cules to simpler compounds.Anabolic pathways consume energy to build complicated molecules from simpler compounds.Enzymes selectively accelerate each step.
Metabolic pathways alter molecules in a series of steps.
Enzymes selectively accelerate each step.Catabolic pathways release energy by breaking down
complex molecules to simpler compounds.Anabolic pathways consume energy to build
complicated molecules from simpler compounds.
Metabolic pathway
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismOrganisms transform energy.
Energy is the capacity to do work - to move matter against opposing forces. Energy is also used to rearrange matter.
Kinetic energy is the energy ofmotion - ex: photons, heat.
Potential energy is the energy matter possesses because of its location or structure.
Chemical energy is a form of potential energy in molecules because of the arrangement of atoms. ATP
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismEnergy can be converted from one form to another.
Ex: as a boy climbs a ladder to the top of the slide he is converting his kinetic energy to
potential energy.As he slides down, the potential energy
is converted back to kinetic energy.
It was the potential energy in the food he had eaten earlier that provided
the energy that permitted him to climb up initially.
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismCellular respiration and other catabolic pathways unleash energy stored in sugar and other complex molecules, which were created during photosyn- thesis, an anabolic path-
way.
CO2 + H2O ⇄ C6H12O6 +O2
←←← Respiration
Photosynthesis → → →
Anabolism
Catabolism
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismAnabolic reactions (building molecules) are
endergonic (or endothermic) – ones that absorb energy.
Ex: the overall reaction of photosynthesis:6CO2 + 6H2O → C6H12O6 + 6O2
Through this reaction, energy from the sun has been put into the chemical bonds of a sugar molecule. The sugar has more energy than the CO2 and H2O.
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismCatabolic reactions (breaking molecules) are
exergonic (or exothermic) – ones that release energy.
Ex: the overall reaction of cellular respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O
Through this reaction energy in the sugar is
been made available to do work in the cell.
The products (CO2 and H2O) have less energy
than the reactants.
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismExergonic vs. endergonic reactions
Respiration - Photosynthesis - energy released for work energy gained from the sun
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolism
The energy created by respiration is used to do work. A cell does three main kinds of work:
Mechanical work: beating of cilia, muscle contractionTransport work: pumping substances across membranesChemical work: driving ender-gonic reactions such as the synthesis of polymers from monomers.
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolism
In most cases, the immediate source of energy that powers cellular work (coupling exergonic reactions to endergonic reactions) is ATP (adenosine triphosphate).
Introduction to metabolismIntroduction to metabolismIntroduction to metabolismIntroduction to metabolismEnergy from respiration (burning food with O2) is
used to add a PO4- group to ADP.
When energy is needed by a cell, the PO4- group
is removed, and the energy is released.The energy traveled from the sun, to the plant, to the animal.
Exergonic → ← Endergonic
Enzyme reviewEnzyme reviewEnzyme reviewEnzyme reviewMost chemical reactions do not occur
spontaneously in our bodies at 98.6o F – we’re too cold.Enzymes are proteins that assist our metabolism.
Substrates are held in the active site by weak hydrogen bonds and ionic bonds.
Within the active site, chemical bonds are stressed, and ATP provides the little energy needed to start the chemical reaction.
Enzyme kineticsEnzyme kineticsEnzyme kineticsEnzyme kineticsAn enzyme is a catalytic protein.
A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction.Enzymes speed up metabolic reactions by lowering energy barriers.
Ex: In a match head, S + O2 → SO2 + energy,
but the reaction is not spontaneous –
friction must be applied to give some initial energy for combustion. In a match head: S + O2 → SO2 + energy
friction
What is cell respiration?What is cell respiration?What is cell respiration?What is cell respiration?Cell respiration is the controlled release of energy
from organic compounds in cells to form ATP.It encompasses different reactions under different circumstances.
Anaerobic respiration:
no oxygenGlycolysisFermentation
Aerobic respiration:
with oxygenCitric acid cycle
GlycolysisGlycolysisGlycolysisGlycolysisGlycolysis (Greek: sugar destruction) is the first
step in cell respiration.An ancient process - occurs in all cells on Earth.Takes place in the cytoplasm. ⇒Does not require oxygen.
Remember: only eukaryotic cells have mitochondria.
GlycolysisGlycolysisGlycolysisGlycolysisGlucose is broken down into pyruvate.Yields a small amount of ATP – only 2 molecules.
2 ATP must be used to activate the glucose; then 4 ATP are pro-duced – enough to power onlya small cell.
BUT without NAD+, the pathway stops.
FermentationsFermentationsFermentationsFermentationsFermentation allows NAD+
to be regenerated, which allows glycolysis to
continue.Two anaerobic pathways:
Alcoholic fermentationLactic acid fermentation
Sole function of fermentationis to regenerate NAD+, but there are many side benefits.
Alcoholic fermentationAlcoholic fermentationAlcoholic fermentationAlcoholic fermentationPyruvate is converted in the cytoplasm into
ethanol and CO2; no more ATP, but NAD+ is regenerated.
The process is present in yeast and some bacteria.Humans use this process to make bread, wine, & beer.
CO2 makes bread rise.
Ethanol forms when CO2 is removed from pyruvate.
Also important now as a bio-fuel (gasoline substitute).
Alcoholic fermentationAlcoholic fermentationAlcoholic fermentationAlcoholic fermentationYeast are critical for bread, beer,
and wine production.
Winery fermenters
Beer production line
Alcoholic Alcoholic fermentation fermentationAlcoholic Alcoholic fermentation fermentation
Production of bio-fuels
Ex: from starch in corn seeds
Lactic acid fermentationLactic acid fermentationLactic acid fermentationLactic acid fermentationMuscle cells switch from aerobic to lactic acid
ferment-ation so ATP is still produced when O2 is scarce.
Ex: athletes such as those running a marathon.The NAD+ must be regenerated to make more ATP.The waste product, lactate, causes muscle fatigue, but ultimately it is converted back
to pyruvate in the liver.
Lactic acid fermentationLactic acid fermentationLactic acid fermentationLactic acid fermentationPyruvate is reduced directly by NADH to lactic acid.
Lactic acid fermentation by some fungi and bacteria is used to make cheese & yogurt.
The “bite” of these products is due to the lactic acid.
Aerobic Cell Respiration
ObjectivesObjectivesObjectivesObjectives
3.7.4 – Explain that, during aerobic cell respiration, pyru- vate can be broken down in the mitochondrion into CO2 and H2O with a large yield of ATP.
C.3.3 – Draw and label a diagram of a mitochondrion; ex- plain the relationship between its structure and its function.
C.3.7 – Analyze data relating to respiration.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationRemember: Remember: glycolysis is the first step in both
aerobic and anaerobic respiration.It’s an ancient process (>3 byo), It’s found in all cells (cytoplasm), It converts glucose into 2 pyru-
vates with a net production of only 2 ATP.
More than ¾ of the original energy in glucose is still present after
glycolysis.This energy can be captured in the process of aerobic respiration.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationWith oxygen, pyruvate can be broken down further
to yield much more energy.In the mitochondria, pyruvate is completely oxidized to CO2 and H2O.
There is a large yield of ATP – 34 more than glycolysis.
Most of the energy within the bonds of sugar is made available.
Mitochondrial structureMitochondrial structureMitochondrial structureMitochondrial structure
Mitochondria have a double membrane; membrane ridges are called the cristae, and the soupy space between them is called the matrix. They also have their own DNA and ribosomes.
Mitochondrial structureMitochondrial structureMitochondrial structureMitochondrial structureMitochondrial structure is related to its function.
They were once free-living bacteria (the theory of endosymbiosis).
The outer membrane is thought to be the host’s, from the original endocytosis; the inner is bacterial.
They need a lot of membrane surface area since this is where the enzymes for respiration are located.
More space for more energy production.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationThe 3 stages of cell respiration:
Glycolysis occurs in the cytoplasm.Breaks 1 glucose into 2 molecules of pyruvate; forms 2 NADH and 2 ATP.
The Krebs cycle occurs in the mitochondrial matrix.
Degrades pyruvate to CO2; forms 2 NADH & 2 ATP.
NADH passes electrons to the electron transport chain on the mitochondrial membrane.
Electrons eventually combine with O2 to form water.
In the process, 34 more ATP are produced, and NAD+ is regenerated to be used in glycolysis.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respiration
No oxygenWith oxygen
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respiration
In the Krebs cycle pyruvic acid from glycolysis is degraded to 3 CO2, which
are breathed out.Two ATP and several NADH
are made through enzyme actions from each pyruvate
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationNADH, made in the Krebs cycle in the matrix of the
mito-chondria (its cytoplasm) carries the electrons produced when pyruvate is broken down into CO2 to the inner mitochondrial membranes (the cristae).
The electrons are passed from one molecule to another and give up some energy at each step.This energy is used to pump hydrogen (H+) across the membrane, building up a high concentration inside.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationNADH, made in the Krebs cycle in the matrix of the
mito-chondria (its cytoplasm) carries the electrons to the inner mitochondrial membranes (the cristae).
The H+ can only exit by diffusion through a protein called ATP synthase.
The protein is like a turbine in a dam; the H+ spin the protein and ADP +P → ATP.
Aerobic cell respirationAerobic cell respirationAerobic cell respirationAerobic cell respirationThe electron transfer chain
Energy in the NADH (the electrons from glucose) pump H+ into the cristae, building up a thousand-fold concentration difference.These diffuse out through ATP synthase making ATP.
Aerobic respiration yields 38 ATP vs. 2 from glycolysis alone.
The electrons eventually get picked up by oxygen, hydrogens follow, making H2O (water).
The electrons eventually get picked up by oxygen, hydrogens follow, making H2O (water).
Respiration poisonsRespiration poisonsRespiration poisonsRespiration poisonsSome poisons interrupt cell respiration.
Cyanide decouples electron transport: electrons can’t reach oxygen and back-up. No NAD+ is available for glycolysis, and creatures run out of ATP and die.
An Analysis of respiration dataAn Analysis of respiration dataAn Analysis of respiration dataAn Analysis of respiration dataBiosphere 2, an enormous greenhouse built in the Arizona desert, has
been used to study 5 different ecosystems. It is a closed system, so measurements can be made under controlled conditions. The effects of different factors, including changes in CO2 concentration in the greenhouse, were studied. The data shown below were collected over the course of 1 day in January.
Identify the time of day when the sun rose.Identify the time of minimal CO2 concentration.
What was the CO2 concentration at that time?
An Analysis of respiration dataAn Analysis of respiration dataAn Analysis of respiration dataAn Analysis of respiration dataDetermine the maximum difference in CO2 conc. over the 24-hr period.What is the relationship between CO2 concentration and light intensity?Suggest reasons for changes in CO2 conc. during the 24-hr period.
