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Cellular Respiration

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Title: Cellular Respiration


1
Cellular Respiration
2
Objectives
  • 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.

3
Introduction to metabolism
  • Energy needs of living things
  • Autotrophs
  • Get energy from the sun or chemicals
  • Producers
  • Heterotrophs
  • Get energy from
    consuming food
  • Consumers
  • Herbivores
  • Carnivores
  • Detritivores
  • Saprotrophs
  • Get energy from consuming dead material
  • Decomposers

4
Introduction to metabolism
  • 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.
  • 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 pathway
5
Introduction to metabolism
  • Organisms 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 of motion - 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
6
Introduction to metabolism
  • Energy 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.

7
Introduction to metabolism
  • Cellular 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

Anabolism
Photosynthesis ? ? ?
Catabolism
??? Respiration
8
Introduction to metabolism
  • Anabolic 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.

9
Introduction to metabolism
  • Catabolic 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.

10
Introduction to metabolism
  • Exergonic vs. endergonic reactions

Respiration - Photosynthesis -
energy released for work energy
gained from the sun
11
Introduction 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
    contraction
  • Transport work pumping substances across
    membranes
  • Chemical work driving ender- gonic
    reactions such as the synthesis of
    polymers from monomers.

12
Introduction to metabolism
  • In most cases, the immediate source of energy
    that powers cellular work (coupling exergonic
    reactions to endergonic reactions) is ATP
    (adenosine triphosphate).

13
Introduction to metabolism
  • Energy 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

14
Enzyme review
  • Most chemical reactions do not occur
    spontaneously in our bodies at 98.6o F were
    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.
15
Enzyme kinetics
  • An 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.

friction
In a match head S O2 ? SO2 energy
16
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 oxygen
  • Glycolysis
  • Fermentation
  • Aerobic respiration with oxygen
  • Citric acid cycle

17
Glycolysis
  • Glycolysis (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.
18
Glycolysis
  • Glucose 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
only a small cell. BUT without NAD, the
pathway stops.
19
Fermentations
  • Fermentation allows NAD to be
    regenerated, which
    allows glycolysis to
    continue.
  • Two anaerobic pathways
  • Alcoholic fermentation
  • Lactic acid fermentation

Sole function of fermentation is to regenerate
NAD, but there are many side benefits.
20
Alcoholic fermentation
  • Pyruvate 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).

21
Alcoholic fermentation
  • Yeast are critical for bread, beer,
    and wine production.

Beer production line
Winery fermenters
22
Alcoholic fermentation
Production of bio-fuels Ex from starch
in corn seeds
23
Lactic acid fermentation
  • Muscle 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.

24
Lactic acid fermentation
  • Pyruvate 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.
25
Aerobic Cell Respiration
26
Objectives
  • 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.

27
Aerobic cell respiration
  • Remember glycolysis is the first step in both
    aerobic and anaerobic respiration.
  • Its an ancient process (gt3 byo),
  • Its 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.

28
Aerobic cell respiration
  • With 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.
29
Mitochondrial 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.
30
Mitochondrial structure
  • Mitochondrial structure is related to its
    function.
  • They were once free-living bacteria (the theory
    of endosymbiosis).
  • The outer membrane is thought to be the hosts,
    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.

31
Aerobic cell respiration
  • The 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.

32
Aerobic cell respiration

No oxygen
With oxygen
33
Aerobic 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

34
Aerobic cell respiration
  • NADH, 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.

35
Aerobic cell respiration
  • NADH, 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.

36
Aerobic cell respiration
  • The 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).
37
Respiration poisons
  • Some poisons interrupt cell respiration.
  • Cyanide decouples electron transport electrons
    cant reach oxygen and back-up. No NAD is
    available for glycolysis, and creatures run out
    of ATP and die.

38
An Analysis of respiration data
  • Biosphere 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?

39
An Analysis of respiration data
  • Determine 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.
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