ENERGY
Physiology
Function:worklive
-grows(mitosis)
-reproduce(meiosis+fertilization)
-metabolism(photosynthesis and respiration)
-inheritance(generation)
Definition of Energy
2 Laws of Energy:
1.Conservation of Energy- energy is neither created nor
destroyed, only transformed(1st law)
*forms of energy: solar, potential, mechanical
2.Entropy- during the transformation of energy, some
energy become disordered & becomes heat(2nd law)
*heat: “disordered energy”
Coupled Reactions and Chemical Bonds
*”coupled”: with partner
*coupled reactions= redox reactions
1.Reduction- gains electrons
-creates chemical bond
-stores energy in molecule
-Photosynthesis(anabolic)
2.Oxidation-loses electrons
-breaks chemical bonds
-releases energy
-Respiration
*electron must go to or come from somewhere
*no energy=dead(kaya malamig ung bangkay)
Life processes are driven by energy
Plants are dynamic metabolic systems.
*1000 reactions/sec
Processes can be:
-energy consuming (endergonic) or
-energy releasing (exergonic) and
-catabolic (breakdown) or
-anabolic (synthesis)
*endergonic: energy must be supplied
*exergonic: energy must be released
The most common and important forms of cellular energy:
1.Chemical bonds (e.g. ATP and CH2O)
2.Electrons (redox reactions)
3.Electrochemical gradients
*”gradients”:difference of something
*A–P~P~P
A–P~P+P
Source of energy: Sun
*can’t recycle energy because of 2nd law
*energy flow: one direction only
* only matters and/or chemicals can be recycled
PHOTSYNTHESIS AND RESPIRATION
~PIC1
Overview: The process that Feeds the Biosphere
Photosynthesis-process that converts solar energy to chemical
Energy
-occurs in plants, algae, certain other protists
and some prokaryotes
*no photosyntehsis, we won’t have food
*cyanobacteria (dati tawag sa kanila blue green algae meron
din sabi bacteria so nagging cyanobacteria)
Plants and other autotrophs – producers of the biosphere
Plants are photoautotrophs
-they use the energy of sunlight to make organic molecules
from water and carbon dioxide
Heterotrophs-obtain their organic material from other
Organisms
-are the consumers of the biosphere
*herbivores, carnivores, omnivores (consumers)
Concept 1: Photosynthesis converts light energy to the
chemical energy of food
*Photosynthesis: CO2 + H2O  GLUCOSE, SUGAR + O2
The leaves of plants-major sites of photosynthesis
*some stems (herbaceous plants) and roots: site of
photosynthesis
Stomata
~PIC2&3
Chloroplasts-organelles in which photosynthesis occurs
-contain thylakoids and grana
*parasitic plants: not photosynthetic
Photosynthesis is summarized as:
6 CO2 + 12 H2O + LIGHT ENERGY  C6H12O6 + 6 O2 + 6 H2O
Photosynthesis- generally a reduction process (may oxidized:
water and reduced:CO2)
Chloroplasts split water into
 Hydrogen and oxygen, incorporating the electrons of
hydrogen into sugar molecules
Photosynthesis is a redox process
-Water is oxidized, carbon dioxide is reduced
Photosynthesis consists of two processes
-the light reactions (light dependent reaction)
-the Calvin cycle (light independent reaction)(or Melvin
cycle)
~PIC4
~PIC6
Concept 2: The light reactions convert solar energy to the
chemical energy of ATP and NADPH
ATP Produced in 3 ways
1.Photophosphorylation-source of energy is sunlight
-involving light and ATP
2.Substrate level phosphorylation-bigger chemicals can be
split (ex. Glucose)
3.Oxidative phosphorylation-goping through different
gradientbreakdown of molecule to ATP
NADPH:
NADP + H + e

NADPH
(in thylakoid and grana) (pag NADPH na, punta sa Stroma)
*NADPH:vehicle lang
Light-form of electromagnetic energy, which travels in
Waves
Wavelength-distance between the crests of waves
-determine the type of electromagnetic energy
Electromagnetic Spectrum-the entire range of
electromagnetic energy or radiation
*UV: more energy
*shorter wavelength: more energy
*longer wavelength: less energy
*Impt in photoshynthesis: visible light(ROYGBIV)
*light: absorbed or reflected
*what you see: reflected light
*Absorbed: all except what you see
*White: reflected all colors, absorbed black
*black: absorbed all colors, reflected none
Pigments- substances that absorb visible light
-light deceptors
- reflect light, which include the colors we see
*melanin:pigment in people, the more the darker skin
*blue/red: maximum absorption of plants
*chlorophyll A: mas bida
*pag tinamaan ng light, absorb ng pigment esp. electron
The absorption of spectra of three types of pigments in
chloroplasts
*the different experiments helped reveal which
wavelengths of light are photosynthetically important
*Result: ~PIC5
Chlorophyll A-main photosynthetic pigment
Chlorophyll B- accessory pigment
Other Accessory Pigments-absorb different wavelengths of
light and pass the energy to chlorophyll A’
When a pigment absorbs light
-it goes from a ground state to an excited state, which is
Unstable
*pag excited yung electron, may energy absorbed
*Fluorescence: with small amount of light
*excited state must release energy
Photosystem- a reaction center associated with lightharvesting complexes
-comnposed of a reaction center
surrounded by a number of lightharvesting complexes
-When a reaction-center chlorophyll molecule absorbs
energy, one of its electrons gets bumped up to a
primary electron acceptor
-The light-harvesting complexes
-consist of pigment molecules bound to particular
Proteins
-funnel the energy of photons of light to the
reaction center
~PIC7
Noncyclic electron flow- primary patrhway of energy
transformation in the light reactions
-produces NADPH, ATP, O2
*pigment Molecules: magkukulang ng isang electron
*pag kulang ng 1 electron, parang adik
*most convenient source of e: water
Water splits(through photolysis: breakdown using light)
into electron(to regain lost e) Oxygen(ung hinihinga
natin) and Hydrogen(for the reduction of ATP)
*water breaks down in the presence of light
*splitting of water: only in the presence of chlorophyll
and light
Light Reaction (NonCyclic Electron Flow)
Reactants
Products
H2O
O2(air)
ADP + iP
ATP(Calvin Cycle)
NADP
NADPH(Calvin Cycle)
*iP= inorganic phosphate
~PIC8
Under certain conditions, photoexcited electrons take
an alternative path.
Cyclic electron flow- only photosystem I is used
-only ATP is produced
*electron will return to it original source
*in some bacteria, only product: ATP
~PIC9
Concept 3: the calvin cycle uses ATP and NADPH to
convert CO2 to sugar
Calvin Cycle- similar to the citric acid cycle
-Occurs in stroma
*mas matipid(cycle in stroma: stroma reactions)
*Melvin Calvin used paper chromatography and isotopes
The Calvin cycle has three phases
-Carbon Fixation: CO2 is fixed to an acceptor(RuBP)
*RuBP: 5 carbon sugar
* RuBP + CO2(from air)
-Reduction
-Regeneration of the CO2 acceptor
~PIC10
Calvin Cycle
Reactants
Products
CO2
C6H12O6 / 3GP
ATP
ADP + iP
NADPH
NADP
*C3 Photosynthesis: kc C3 first product
*all plants have C3 Photosynthesis
Concept 4: Atlernative mechanisms of carbon fixation have
evolved in hot, arid climates
*stomata open during day to allow gasses to enter but
water evaporates
On hot, dry days, plants close their stomata
-conserving water but limiting access to CO2
-causing oxygen to build up
*photorespiration: result of building up of oxygen
Photorespiration – O2 substitutes for CO2 in the active site
of enzyme rubisco
-photosynthetic rate is reduced
Rubisco- enzymes responsible for
RuBP + CO2  Carbon
*minsan nagkakamali ung rubisco so…
RuBP + O2  photorespiration
*masisira RuBP, will not continue Calvin cycle
*disadvantage to plants so plants have ways to adapt
Calvin Cycle:
RuBP + CO2  3GP + 3GP (glucose)
*RuBP = C5
Adaptations
1.C4 plants- minimize the cost of photorespiration by
incorporating CO2 into four Carbon compounds in
mesophyll cells
*“C4” kasi initial product 4 C
*These four carbon compounds are exported to bundle
sheath cells, where they release CO2, used in Calvin Cycle
~PIC11
2.CAM Plants- open their stomata at night,
incorporating CO2 into organic acids
-“Crassulean Acid Metabolism”
-looks like cactus
-in hot areas
-During the day, the stomata closes and the CO2 is
released from organic acids for use in the Calvin
Cycle
*The CAM pathway is similar to C4 pathway
~PIC12
*all with Calvin Cycle, some CAM, some C4
*Carbon Dioxide- during day lang nagagamit kasi with
sunlight for light reaction
*No photosynthesis, no body of plants, no food/rice
for us
Organic compounds produced by photosynthesis
-provide the energy and building material for
ecosystems
C3
CAM
C4 Mechanism
Mechanism
Mechanism
CO2
CO2
CO2
NADP
NADP
Reactants
NADP
ADP + iP
ADP + iP
ADP + iP
H2O
H2O
NADPH
NADPH
NADPH
ATP
ATP
ATP
Products
O2
O2
O2
C6H12O6
C6H12O6
C6H12O6
Initial CO2
PEP(at
PEP(mesophyll)
fixation
night)
RuBP
RuBP(bundle
Final CO2
RuBP(at
sheath)
Fixation
daytime)
Example
Rice
Sugarcane
pineapple
*NADPH, O2, ATP :produced in light
*C6H12O6: produced in calvin
*Glucose: w/ many energy but relatively large
*Glucose to ATP(Cellular Respiration)
Cellular Respiration
Harvesting chemical energy
 So we see how energy enters food chains(via autotrophs)
we can look at how organisms use that energy to fuel
their bodies
 Plants and animals both use products of
photosynthesis(glucose) for metabolic fuel
 Heterotrophs: must take in energy from outside sources,
cannot make their own e.g. animals
 When we take in glucose (or other carbs) proteins, and
fats-these foods don’t come to us the way our cells can
use them
Cellular Respiration overview
 Transformation of chemical energy in food into chemical
energy cells can use:ATP
 These reactions proceed the same way in plants and
animals. Process is called cellular respiration
 Overall reaction: C6H12O6 + 6 O2  6 CO2 + 6 H2O
Cellular Respiration- chemical-bond energy in sugars is
converted to energy-rich compound ATP which can then be
used for metabolic reactions
*break down of glucose
*oxidation
*lose electron, break bonds, release energyATP
*Supposedly.. C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP
* C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP (photosynthesis)
*Photosynthesis is not the opposite of respiration
*they only use each other’s products
Stages of respiration:
1.Glycolysis
-in cytoplasm
-carbohydrates
-breakdown
*if O2 Absent, hanggang ditto nalang)(Anaerobic)
*If O2 present…(Aerobic)
2. Krebs
3.ATC(Electron transport Chain)
 Breakdown of glucose begins in the cytoplasm: the liquid
matrix inside the cell
 At this point life diverges into two forms and two
pathways
-Anaerobic cellular respiration (aka fermentation)
-Aerobic cellular respiration
Cellular respiration reactions
 Glycolysis
-series of reactions which break the 6-carbon glucose
molecule down into 3-carbonm molecules called
pyruvate
-process is an ancient one-all organisms from simple
bacteria to humans perform it the same way
-yields 2 ATP molecules for every one glucose
molecule broken down
-yields 2 NADH per glucose molecule
Aerobic Cellular reaction
 Oxygen-required=aerobic
 2 more sets of reactions which occur in a specialized
structure within the cell called the mitochondria
-1.krebs cycle
-2.Electron Transport chain
~PIC13 and 14
Kreb’s cycle
 Completes the breakdown of glucose
-takes the pyruvate (3-carbons) and breaks it down
the carbon and oxygen atoms end up in CO2 and H2O
-hydrogens and electrons are stripped and loaded
onto NAD+ and FAD to produce NADH and FADH2
 Production of only 2 more ATP but loads up the
coenzymes with H+ and electrons which move to the
3rd stage
*NADP + H + C  NADPH*NAD + H + C  NADH (respiration)
*FAD + 2 h + 2 c  FADH2 (respiration)
Electron Transport Chain
 Electron carriers loaded with electrons and
protons from the Kreb’s cycle move to this
chain-like a series of steps(staircase)
 As electrons drop down stairs, energy
released to form a total of 32 ATP
 Oxygen waits at bottom of staircase, picks up
electrons and protons and in doing so
becomes water
Energy tally
 36 ATP for aerobic vs. ATP for anaerobic
-Glycolysis
2 ATP
-Kreb’s
2 ATP
-ETC
32 ATP
 Anaerobic organisms can’t be too energetic
but are important for global recycling of
carbon
~PIC15
*1 glucose= 36 ATP
*each cell needs thousands of ATP
Anaerobic cellular respiration
 Some organisms thrice in environments with little or no
oxygen
-marches, bogs, gut of animals, sewage treatment ponds
 No oxygen used=”an”aerobic
 Results in no more ATP, final steps in these pathways
serve only to regenerate NAD+ so it can return to pick up
more electrons and hydrogens in glycolysis
 End products such as ethanol and CO2 (single cell
fungi(yeast) in beer/bread) or lactic acid(muscle cells)
*Ethanol:small amount of ATP9only 21 so yeast will die)
-15% yeast will die(kaya sealed wine)
*fermentation product=yeast
*happens in yeast and cheese
*in animals, will feel cramps (due to presence or building up
of lactic acid)(focus of oxygen brain nalang)
*need CO2:photosyntehsis
*need O2: cellular respiration
*leaves: photosynthesis and respiration
*roots: mainly respiration only
*woody trees(stem):respiration
*non-photosynthetic parts:respiration
*hole in the bark:lenticel(entry of gasses)
*O2:most important for respiration
Reactants
Products
Stages
Aerobic
C6H12O6 + 6 O2
6 CO2 + 6 H2O
=36 ATPS
Glycolysis
Krebs
ETC
Glycolysis
Reactants
C6H12O6
Products
Pyruvate
CO2
Anaerobic
C6H12O6
Ethanol/lactic
acid
2 atp
CO2
glycolysis
Kreb’s
Pyruvate
Acetyl
COa
NAD
FAD
NADH
FADH2
CO2
ETC
ADP + iP
NADH
FADH2
ATP
H2O
Reactants
Products
Events
Where
Photosynthesis Respiration
CO2 + H2O C6H12O6 + 6O2
O2
6 CO2
glucose
2 H2O
Glycolysis
Light reaction
Kreb’s cycle
Calvin cycle
ETC
Mesophyll
Mitochondria
Bundle sheath
cytoplasm
chloroplast