Transcript Chapter 03 - Hinsdale South High School

Chapter 03
Energy
Light to Life
Overview:
• Energy from the sun is used to make ATP
• ATP is used to activate molecular bonding
• Energy is stored in bonds
• Energy is released when bonds are broken
The structure of atoms
An atom is:
• The smallest unit of a pure substance
(element) which cannot be broken down
by ordinary chemical means
• Composed of protons, neutrons and
electrons
The structure of atoms
• Protons: mass = 1, + charge, found in
nucleus
• Neutrons: mass = 1, no charge, found
in nucleus
• Electrons: mass negligible, - charge,
orbit the nucleus
The structure of atoms
Chemical behavior is determined by electron
number and arrangement :
• Electrons arranged in energy levels
• Highest energy level electron shells are
farthest from nucleus
• Octet Rule: atoms bond in ways to achieve 8
electrons in the highest energy level
The Structure of Atoms
An atom is made of negatively-charged electrons orbiting
around a positively-charged nucleus.
Biological molecules are organic
(carbon-based) compounds
Common elements in living systems:
• C, O, H, N
• Important ions: Ca, K, P, Na, S, Cl, Mg
• Trace ions and minerals: I, Zn, Mn, Cu,
and others
Carbon
• Basis of all organic compounds
• Forms four bonds
• Enables molecules to add backbone
length
• Enables molecules to connect unique
side groups; provide character and
informational value
• Forms bonds most often with O, H, or N
Example of an Organic Compound
Line structure and space-filling model of the dipeptide glycineserine
Making Bonds
Bonds:
• forces that hold atoms together
• form when atoms with correct fit collide
with sufficient force
• store energy
Making Bonds
• Covalent bond: atoms collide and
electrons rearrange so that some of
the electrons are shared by the two
atoms
Making Covalent Bonds
Atoms collide and electrons are rearranged and shared.
Two electron orbits are joined.
Making Bonds
Oxygen forms covalent bonds with two hydrogen atoms
to form water
Molecular Changes
Breaking Bonds
• Bonds break when molecules collide with
enough force and at appropriate angles
• Shared electrons return to their original orbits
and release the stored energy in the bond
• Bond energy can be lost as heat or
transferred to other molecules and preserved
in a new bond
Transferring Energy
Molecules collide, bonds break, and energy is transferred to
the bonds of the new molecule.
Life and the Laws of Energy
All matter and energy in the universe follow
the Laws of Thermodynamics:
• First Law: Energy can be gained or lost
in chemical processes, but it can’t be
created or destroyed.
• Second Law: Energy disperses and
ordered structures become disordered
(entropy increases).
Energy Flow and change in
living systems
How the laws of thermodynamics apply to
cells:
• Over time, all things in the universe tend
toward disorder
• Cells need a continual, external source
of useful energy to do work, overcome
entropy and remain organized
Energy Flow and Equilibrium
• Equilibrium: energy flows as readily
backwards as forwards in a chemical
reaction
• Cells become inactive and die in
equilibrium conditions
• Cells maintain far-from-equilibrium
conditions by adding reactants and
removing products
NO2 molecules
collide to form
N2O4. When
sufficient N2O4
accumulates, the
reverse reaction
begins and N2O4
fragments into
NO2.
Equilibrium is
reached when the
forward and
reverse reactions
occur at the same
rate.
Equilibrium
Energy Flow and Equilibrium
ATP – The Energy Molecule
Each ATP molecule
has three subunits:
• ribose sugar
• adenine
• three phosphate
groups (PO4) linked
to form a
triphosphate group
ATP – The Energy Molecule
• ATP is a high-energy donor molecule
• Energy is released by breaking ATP’s
phosphate bonds (hydrolysis)
• ATP is reassembled by reattaching its
phosphates with an input ? energy
ATP – The Energy Molecule
Some of ATP’s Jobs
Making information chains
Some of ATP’s Jobs
Making proteins contract
Some of ATP’s Jobs
Transporting small molecules
Enzymes
Enzymes:
• Catalysts that speed up and facilitate
chemical reactions
• Molecules fit into active sites (docking
sites)
• Chemically interact with molecules and
force them to react in aided collisions
• Large protein molecules
Enzymes bind substrates at active
sites
Active site:
• groove or cleft on enzyme formed by
tertiary structure of protein
• binds, orients, strains substrate
• has shape specific for substrate
Enzymes
Energy Flow Through Life
Macro View
Food Chain:
• Primary Producers: convert energy from sun
into chemical bonds of sugar (photosynthesis)
• Herbivores: obtain energy directly from plants
• Carnivores: obtain energy from flesh of
herbivores
• Decomposers: obtain energy by breaking down
waste and dead bodies of above groups
Energy Flow Through Life
Macro View
Energy Flow Through Life
Macro View
Plants play an important role:
• produce fuel (sugar)
• produce oxygen to burn fuel
• consume carbon dioxide waste
Energy Flow Through Life
Macro View
Energy Flow Through Life
Micro View
Sugar (glucose)
• energy source
• building material for other molecules
such as amino acids and nucleotides
Glucose
Glucose is a small carbohydrate called a
monosaccharide (mono = “one”, saccharide is
from saccharum = “sugar”)
Starch
Glucose molecules link
together to form
starch, a
polysaccharide
(“many sugar units”).
Amylopectin is a type
of plant starch.
Energy Flow Through Life
Producing Sugar - Photosynthesis
Chloroplasts:
• organelle found in plant cells
• produces sugar using energy from
sunlight
Energy Flow Through Life
Breaking Down Sugar - Respiration
Mitochondria:
• organelles found in both plant and
animal cells
• break down sugar and produce ATP
Energy Flow Through Life
Micro View
Life’s molecules are continuously recycled:
• Chloroplasts:
carbon dioxide + water  sugar + oxygen
• Mitochondria:
sugar + oxygen  carbon dioxide + water
Capturing Light Energy
• Light: electromagnetic energy that travels in
waves of varying lengths
• Photons: packets of light
• Pigments: molecules which absorb some
light wavelengths and reflect others
• The colors we observe correspond to the
wavelengths that are reflected by the pigment
The Electromagnetic Spectrum
Pigments absorb some visible wavelengths of light
and reflect others.
Capturing light energy in chemical
bonds
Photosynthetic pigments:
• Chlorophylls: primary pigments
· Absorb photons of violet-blue and red
• Antenna pigments (carotenoids)
· Absorb photons of green, blue, violet
· Increase range of energy absorption
Chlorophylls absorb violet-blue and
red light. They reflect green and
yellow light.
Photosynthesis Takes Place in
Chloroplasts
Chlorplast
•
•
•
•
Double outer membrane
Stroma: inner chamber
Thylakoids: flattened sacs
Grana: stacks of thylakoids
Photosynthesis
Light-Dependent Reactions
(“Electron Bounce”)
1. Photons hit
chlorophyll
molecules
(photosytem II)
in leaves,
exciting
electrons to
higher-energy
orbits.
Photosynthesis
• 2. Electrons
bounce along
chlorophyll
molecules and
onto small
carrier
molecules (an
electron
transport chain)
in the thylakoid
membrane.
Light-Dependent Reactions
(“Electron Bounce”)
Photosynthesis
Light-Dependent Reactions
(“Electron Bounce”)
• 3. Electrons lost
from chlorophyll are
replaced by
electrons from
water. Oxygen
atoms from the
water pair up with
hydrogen and are
released as an
important
byproduct.
Photosynthesis
Light-Dependent Reactions
(“Ion Shuffle”)
• 4. Electrons on
carrier
molecules
attract hydrogen
ions from the
stroma.
Photosynthesis
Light-Dependent Reactions
(“Ion Shuffle”)
• 5. Carrier molecules bring hydrogen ions to an
enzyme which ejects them into the thylakoid sac.
Photosynthesis
Light-Dependent Reactions
(“Ion Shuffle”)
• 6. Hydrogen ions exit the thylakoid sac through a
channel in an ATP-producing enzyme (ATP synthase).
Photosynthesis
• 7. Spent
electrons
replace
electrons
bouncing off a
new set of
energized
chlorophyll
molecules
(photosystem I).
Light-Dependent Reactions
(“Ion Shuffle”)
Photosynthesis
Light-Dependent Reactions
(“Ion Shuffle”)
• 8. Energized
electrons unite
with hydrogen
ions on NADP
to form reactive
“hot” hydrogens
(NADPH).
Overview of LightDependent Reactions
Photosynthesis
Light-Independent Reactions – Calvin Cycle
Overview:
• Team of five
enzymes uses ATP,
carbon dioxide, and
“hot” hydrogens from
NADPH to produce
half-molecules of
sugar in the stroma
of the chloroplast
(carbon fixation or
Calvin Cycle).
Calvin Cycle
• Enzyme A:
attaches
three carbon
dioxides to
three 5-C
sugars
Calvin Cycle
• Three 6-C
sugars break
into six 3-C
sugars
• Enzyme B:
energizes 3-C
sugar fragments
with ATP
Calvin Cycle
• Enzyme C: attaches
hydrogens from
NADPH to six 3-C
sugars and releases
one
• Released 3-C sugars
(half-sugars) exit
chloroplast and pair
up to form 6-C
glucose in cytoplasm
Calvin Cycle
• Enzyme D:
rearranges
remaining five
3-C sugars to
form three 5C sugars
Calvin Cycle
• Enzyme E:
energizes 5-C
sugars with
ATP
• Repeat cycle
Calvin
Cycle
Respiration Takes Place in the
Mitochondria
Respiration Overview
Three main stages:
• Glycolysis: cytosol
• Krebs Cycle: mitochondrial matrix
• Electron Transport Chain: mitochondrial
inner membrane
Overview of Respiration
Glycolysis
• From greek: lysis = “to break apart”,
glyco = “sugar”
• Glucose is broken into smaller fragments by a
series of enzymes
• Generates two ATP
• Requires no oxygen (anaerobic)
• Prepares glucose for Krebs Cycle
• Emergency energy source
• Early metabolic pathway
Glycolysis
Respiration
Krebs Cycle
• Enzymes extract
energetic
hydrogens from 2C sugar fragments
(from glycolysis of
glucose) [1]
• Carbon and
oxygen combine
and are discarded
as carbon dioxide
(animals exhale)
The Krebs
Cycle
Respiration
Electron Transport Chain
• “Hot” hydrogens (from NADPH) give up their
electrons to an enzyme in the mitochondrion
inner membrane.
• Electrons pass along carriers in the inner
membrane, picking up hydrogen ions [2]
Respiration
Electron Transport Chain
• Enzymes eject hydrogen ions into
intermembrane space [3]
Respiration
Electron Transport Chain
• Hydrogen ions force their way out through a
channel in an ATP-producing enzyme [4]
ATP is the end result
Respiration
• Spent
electrons
combine
with
hydrogen
ions and
oxygen to
form water –
a waste
product [5]
Electron Transport Chain
Respiration – The Electron
Transport Chain
Metabolism
Building up and breaking down materials
Community Energy
Within an organism:
• Groups of cells have special roles that
require additional energy
• Specialized cells divert ATP to duties
that benefit whole organism