Transcript Option C: Cells & Energy

Option C: Cells & Energy
C.1 Proteins
• C.1.1: Explain the 4 levels of protein structure,
indicating each level’s significance
• C.1.2: Outline the differences between fibrous &
globular proteins, with reference to two
examples of each type
• C.1.3: Explain the significance of polar and nonpolar amino acids
• C.1.4: State six functions of proteins, giving a
named example of each
4 levels of Protein Structure
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1. Primary
The unique amino acid
sequence
Like the order of
letters in a very long
word
Slight changes in
primary structure
greatly affect overall
conformation and
function
4 levels of Protein Structure
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2. Secondary
Coils and folds of the
primary structure as a
result of hydrogen
bonding
Electronegative O & N
attract H
E.g. – alpha helix,
pleated sheet
4 levels of Protein Structure
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3. Tertiary
Contortions of molecule
by bonding between R
groups of amino acids
Hydrophobic
interactions important
– Core versus outer parts
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May be further
reinforced by disulfide
bonds
4 levels of Protein Structure
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4. Quartnerary
2 or more polypeptide
chains aggregated into
functional unit
Collagen – 3 proteins
together, Hemoglobin
4 proteins together
Shape of subunits
together specifies
function
Fibrous vs. Globular Proteins
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Functional Quaternary proteins are either …
Fibrous – long ropelike structures
1. Collagen – 40% of protein in human body, from
skin, bone, tendons & ligaments
2. Keratin – hair, horns, skin
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Globular –spherical
1. Hemoglobin – oxygen binding protein in blood
2. Lysozyme – immune enzyme in saliva, tears,
sweat that targets bacterial surface proteins
Polar vs Nonpolar
• Polarity of amino acids influences protein
behavior
– Membrane position (polar portions in or out of
cells, nonpolar portions in membrane)
– Hydrophobic channel creation
– Specificity of enzyme active site –
complements properties of the substrate
Important Proteins
Protein
Keratin
Casein
Hemoglobin
Actin
Insulin
Lysozyme
Function
Important Proteins
Protein
Function
Keratin
Support in hair, horns and feathers
Casein
Storage of AA for babies in milk
Hemoglobin
Transport of O2 by blood
Actin
Movement of muscle fibers
Insulin
Hormone regulates sugar in blood
Lysozyme
Defense against foreign
substances
C.2 Enzymes
• C.2.1: State that metabolic pathways consist of
chains and cycles of enzyme catalyzed reactions
• C.2.2: Describe the induced fit model
• C.2.3: Explain that enzymes lower the activation
energy of the chemical reactions which they
catalyze.
• C.2.4: Explain the difference between competitive
and non-competitive inhibition with reference to one
example of each.
• C.2.5: Explain the role of allostery in the control of
metabolic pathways by end-product inhibition
Chemical Reaction Types
• Exergonic reaction  ENERGY
OUTWARD: proceeds with the net
release of free energy
• Endergonic reaction  ENERGY
INWARD: proceeds with the net
absorbtion of energy from the
surroundings
Metabolism
• Metabolism = The totality of an organisms
chemical processes.
• Managing the material and energy resources
of the cell.
• Metabolic Pathways consist of chains and
cycles of enzyme catalyzed reactions
– Catabolic pathways: break down molecules and
release energy
– Anabolic pathways: build complex molecules and
absorb energy
Reaction types: Exergonic &
Endergonic
Models of enzyme function
LOCK & KEY MODEL
INDUCED FIT MODEL
• Each enzyme fits
• Extension of Lock and
exactly one substrate
key model
• Complementary
• Some enzymes can
shapes like a lock and
bond multiple
a key
substrates
• Interaction between
enzyme and substrate
induces change to fit
The induced fit model accounts for the broad
specificity of some enzymes
Competitive vs. non-competitve
• Competitive – inhibiting molecule is structurally
similar to substrate, binds to active site,
prevents substrate bonding
– Inhibition of butanedioic acid dehydrogenase by
propanedoic acid in the Krebs cycle
– Inhibition of folic acid synthesis in bacteria by
sulfonamide protosil (an antibiotic)
• Non-competitive – inhibiting molecule binds to
enzyme (not at A.S.) causing conformational
change to active site
– Hg+2, Ag+, Cu+, inhibition of cytochrome oxidase by
binding to –SH groups and breaking -S-S- linkages
Allosteric Regulation
• Form of non-competitive inhibition
• Inhibition is a natural mechanism of cell
metabolic control
• Shape of allosteric enzymes can be altered by
binding of end products at the allosteric site
• Metabolites or end products can serve in
negative feedback by binding to allosteric site
and decreasing enzyme function
– ATP inhibition of phosphofructokinase in glycolysis
Allosteric Reactions
are and example of
feedback inhibition
C.3 Respiration
• C.3.1: State that oxidation involves the loss of
electrons from an element whereas reduction
involves the gain of electrons, and that oxidation
frequently involves gaining oxygen or losing
hydrogen, while reduction involves losing oxygen or
gaining hydrogen
• C.3.2: Outline the process of glycolysis including
phosphorylation, lysis, oxidation, and ATP formation
• C.3.3: Draw the structure of a mitochondrion as
seen in electron micrographs.
• C.3.4: Explain aerobic respiration including
oxidative decarboxylation of pyruvate, the krebs
cycle, NADH+ + H+, the electron transport chain,
and the role of oxygen
C.3 Respiration
• C.3.5: Explain oxidative phosphorylation
in terms of chemiosmosis
• C.3.6: Explain the relationship between
the structure of the mitochondrion and its
function.
• C.3.7: Describe the central role of acetyl
CoA in carbohydrate and fat metabolism
• C.3.8: Analyze data relating to respiration
Overall Process
Organic compounds + Oxygen
Carbon dioxide + Water + Energy
For convenience we usually start with
glucose, but can use lipids, proteins and
other carbohydrates.
C6H12O6 + 6 O2
6 CO2 + H2O + Energy
Glucose is oxidized and oxygen is reduced
Oxidation-Reduction
• Always coupled
• Chemical reactions which involve a partial
or complete transfer of electrons from one
reactant to another.
• Oxidation: partial or complete loss of efrom a substance; e- donor is the reducing
agent.
• Reduction: partial or complete addition of
e- to another substance; e- acceptor is an
oxidizing agent.
Comparison of Oxidation and
Reduction
Oxidation
1. Addition of oxygen
atoms
2. Removal of H atoms
3. Loss of e- from a
substance
Reduction
1. Removal of oxygen
atoms
2. Addition of H atoms
3. Addition of e- to a
substance
Overview of Cell Respiration
3. Cell Respiration: a)Glycolysis
• Catalyzed by enzymes in the cytoplasm
• Glucose is partially oxidized and a small
amount of ATP is produced
• Accomplished without the use of oxygen
• Is part of both aerobic and anaerobic
respiration
Glycolysis overview
1.
Energy investment phase: 2 phosphate groups from ATP are
added to a molecule of glucose (hexose sugar) to form a
hexose biphosphate.
2. Lysis: The hexose biphosphate is split to form two molecules
of triose phosphate.
3. Oxidation: 2 molecules of NAD+ are reduced to 2NADH +
2H+; so the triose phosphate is oxidized. The energy is used
to add another phosphate group to each triose.
NADH can enter the electron transport chain in the
mitochondria and be used to produce more ATP in the
process called oxidative phosphorylation
4. ATP Formation: Two phosphate groups are removed from the
two trioses and passed to ADP to form ATP.
So 4 ATPs are generated for a net gain of 2 ATPs.
ATP is produced by a process called substrate-level
phosphorylation because an enzyme transfers a phosphate
group from a substrate (organic molecule generated by the
sequential breakdown of glucose) to ADP
The End of Glycolysis
• A 6 Carbon compound has been turned
into 2 3 Carbon compounds called
pyruvate (A.K.A. oxopropanoate).
• Glucose has been oxidized
• Net gain 2 ATP, 2NADH + 2H+
• ATP made through substrate level
phosphorlyation
• Glycolysis also yields 2 water molecules
for each glucose.
Aerobic respiration
• Each pyruvate must be decarboxylated
(CO2 removed)
• Remaining 2 carbon molecule (acetyl
group) reacts with reduced coenzyme A
• During in the process NADH + H+ are
formed
The Link Reaction: oxidative
decarboxylation
Summary of One Turn of the
Krebs Cycle
• 1. Acetyl CoA (2C) enters the cycle & joins a 4C
molecule.
• 2. In a series of steps, the remaining H and high
energy electrons are removed from the Acetyl CoA.
• 3. Three NAD+ are converted into 3 NADH & 3H+.
• 4. One FAD is converted into 1 FADH2.
• 5. One ATP is made (by substrate phosphorylation).
• 6. Two CO2 are released.
• 7. At the end of the cycle, nothing remains of the
original glucose molecule
Krebs cycle results per glucose
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2 molecules of pyruvate are oxidized
2 ATPs by substrate level phosphorylation
6 NADH and 2 FADH2
Starting material is regenerated
Electron transport chain couples electron
flow down the chain to ATP synthesis.
ETC / Oxidative Phosphorlyation
• The purpose of the Electron Transport Chain is to
receive the high energy electrons carried by the
coenzymes NADH &FADH2 and use the energy from
these electrons to pump protons out of the matrix. A
high concentration of protons results. As the
protons diffuse back to the matrix, their energy is
used by the ATP synthase to create 32 ATP.
• Oxidative phosphorylation (electron transport) - The
creation of ATP via chemiosmosis as a result of
electron transport.
Electron transport
• a) Occurs at cristae (Inner membranes)
• b) NADH & FADH2 deliver H+ and e- to cristae.
• c) Electrons "transport" along cristae through
electron acceptors, provide energy to pump H+
from matrix to outer compartment.
• d) Concentration of H+ is now higher in outer
compartment. H+ pass through ATP synthetases
in cristae back to matrix. 32 ATP are made. This
is known as chemiosmosis.
• e) Last step involves H+ & e- added to oxygen.
This frees NAD+ to return to glycolysis & Krebs
Cycle to pick up more H+ & e-.
• Chemiosmosis is the process where
protons diffuse from the outer
compartment (high concentration)
through ATP Synthase in the Cristae to
the Matrix (low H+ Concentration). The
energy in the protons as they pass is
used by ATP synthase to create 32 ATP.
XIV: Mitochondria and Chloroplasts
• Main energy transformers of cells; transduce energy
acquired from the surroundings into forms usable
for cellular work.
• BOTH:
a) enclosed by double membranes which are NOT
part of endomembrane system
b) contain ribosomes and some DNA that programs
a small portion of their own protein synthesis
c) are semiautonomous organelles that grow and
reproduce within the cell (see Ch. 26 for a
discussion of the origins of eukaryotic cells from
symbiotic consortiums of prokaryotic cells; Dr. Lynn
Margulis’ endosymbiotic theory.
Mitochondria
1. Sites of cellular respiration (catabolic
oxygen-requiring process that uses
energy extracted from organic
macromolecules to produce ATP).
2. Found in nearly all eukaryotic cells;
number directly correlates with cell’s
metabolic activity.]
3. 1 um in diameter; 1-10 um in length
4. Can move, change shape and divide
Mitochondrion
Mitochondria Structure
BE ABLE TO DRAW AND LABEL
1. Enclosed by two membranes: smooth outer
membrane and convoluted inner membrane which
contains embedded enzymes involved in cellular
respiration.
2. Infoldings or cristae increase surface area
3. Membranes divide mitochondrion into 2 internal
compartments:
a) intermembrane space: same solute composition of
cytosol.
b) mitochondrial matrix: contains enzymes that
catalyze many steps of cell respiration (Krebs cycle)
The Role of acetyl CoA
• Acetyl CoA is an intermediate in
carbohydrate metabolism
• In lipid metabolism, the oxidation of fatty
acid chains results in the formation of
carbon fragments with 2C each
• 2 carbon fragments are acetyl fragments
• They pass into Krebs cycle
Proteins and fats in cell respiration:
Central role of Acetyl CoA
C.4 Photosynthesis
• C.4.1: Draw the structure of a chloroplast as
seen in electron micrographs
• C.4.2: State that photosynthesis consists of
light-dependent and light-independent
reactions.
• C.4.3: Explain the light dependent reactions
• C.4.4: Explain phosphorylation in terms of
chemiosmosis
• C.4.5: Explain the light independent
reactions
C.4 Photosynthesis
• C.4.6: Explain the relationship between the
structure of the chloroplast and its function
• C.4.7: Draw the action spectrum for
photosynthesis
• C.4.8: Explain the relationship between the action
spectrum and the absorption spectrum of
photosynthetic pigments in green plants
• C.4.9: Explain the concept of limiting factors with
reference to light intensity, temperature and
concentration of carbondioxide.
• C.4.10: Analyze data relating to photosynthesis
Chloroplast
B. Chloroplasts
• BE ABLE TO DRAW AND LABEL
• One of a group of plant and algal membrane-bound organelles
• Chloroplasts divided into 3 functional compartments by a system of
membranes.
1. Intermembrane space: space between the double chloroplast
membrane.
2. Stroma: viscous fluid outside the grana (stacks of thylakoids);
light-independent chemical reactions take place here. Carbon
dioxide converted to sugar.
3. Thylakoids: flattened membranous sacs inside chloroplast;
chlorophyll is found in membranes; function in the light-dependent
chemical reactions.
4. Thylakoid space: space inside the thylakoids.
Figure 10.8 Evidence that chloroplast pigments participate in photosynthesis:
absorption and action spectra for photosynthesis in an alga
Absorbance
Peaks in:
Red & Blue
Minimum in
Green
Photosynthesis consists of the light dependent and light
independent reactions
2 step process
• Light Dependent Reactions = photo
• Light Independent Reactions (Calvin cycle) =
synthesis
• Light dependent reactions are in the
thylakoid, light independent reactions in the
stroma
• Transforming light energy into chemical
energy of ATP and NADPH
• Creation of Sugars from inorganic
compounds
Photosystems
• In thylakoid membrane chlorophyll organized
with other molecules in photosystems
• “Antenna array” of Chlor. A, B, & carotenoid
pigments, clustered around a reaction center
• Reaction center is a single Chlorophyl A
associated with the “primary electron
acceptor” (PEA)
• Chlorophyl A passes electrons to the PEA
• PEA traps excited electrons before they fall
back to ground state
Figure 10.11 How a photosystem harvests light
Photosystems
• 2 types of photosystems in thylakoid
membrane cooperate in light reactions
• Called Photosystem I & II – different PEA
• Photosystem I – P700 best absorbance at
700 nm wavelength (red)
• Photosystem II – P680 also in red
• Identical chlorophyll but different protein
association
Electron flow
• Light drives synthesis of ATP and NADPH
• Energy transformation based on flow of
electrons
• Two routes of electron flow
– Noncyclic electron Flow = predominates
during light reactions – ejected electrons don’t
cycle back to ground state
– Cyclic electron Flow = uses Photosystem I
not PS II – no production of NADPH or O2
Figure 10.12 How noncyclic electron flow during the light reactions generates ATP
and NADPH (Layer 5)
Light dependent reactions use solar power to produce ATP and NADPH
to fuel sugar production in the Calvin cycle
Cyclic electron Flow
– Cyclic electron Flow = uses Photosystem I
not PS II – no production of NADPH or O2
– Short circuit back into electron transport
chain
– Does produce ATP  cyclic phosphorylation
– Light independent reaction consumes more
ATP than NADPH, Cyclic electron flow
makes up the difference in ATP required
Review of chemiosmosis
• Mechanism of generating ATP
• Electron transport chain pumps protons
across the membrane while electrons are
shuttled through different carriers
• Protons pumped to the inside of thylakoids
• Protons accumulate, pH and charge increase
 move out to stroma through channels
• Movement through channels in ATP synthase
drives production of ATP
Figure 10.15 Comparison of chemiosmosis in mitochondria and chloroplasts
Figure 10.16 The light reactions and chemiosmosis: the organization of the thylakoid
membrane
The Light Independent Reactions:
Synthesis of sugars
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Takes place in the Stroma
Carbon enters as CO2 and leaves as sugar
ATP is the energy source
NADPH provides reducing power for adding
high energy electrons
• Direct product of Calvin cycle is
glyceraldehyde-3-phosphate (G3P)
• 3 cycles to make this product
• Actually fixing three molecules of CO2
Figure 10.17 The Calvin cycle (Layer 3)
Calvin cycle summary
• For the synthesis of 1 molecule of sugar
• Require the input of 9 ATP and 6 NADPH
• Light reactions regenerate ATP, NADPH
• G3P can be used to produce other sugars
Figure 10.20 A review of photosynthesis
Limiting Factors
• Certain factors in the environment can
effect how photosynthesis occurs
• Main limiting factors are Temperature,
Light intensity, and CO2 concentration
• Other factors include nutrient availability,
such as nitrogen, phosphorous and iron
• Different factors limit plant growth in
different areas
Effects of Light Intensity &
Temperature on Photosynthesis
• As light intensity increases the rate of
photosynthesis increases and
• Plateau once photosynthetic machinery is
operating at peak capacity
• Photoinhibition: sunburn for plants, occurs
when too much light overloads photosynthetic
machinery
• For a given light intensity, Higher temperature
 Increased rate of photosynthesis
•A = at low light intensities light is a limiting
factor and temperature has no effect
• B = at higher light intensities, temperature is
a limiting factor, warmer  higher rate of
photosynthesis
Effects of Carbon Dioxide on
Photosynthetic Rate