Cellular Energetics

Catabolic pathways




Fermentation: Partial degradation (O
2
)
Cellular respiration: Full degradation (O
2
)
Organic compounds + O
2 energy (gasoline burning)
 CO
2
+ H
2
O +
C
6
H
12
O
6
+ 6O
2
 6CO
2
+ 6H
2
O + energy

Redox reactions





Explains how energy is yielded by transfer of electrons
Oxidation: Loss of electrons
Reduction: Gain of electrons (OILRIG)
Na + Cl  Na+ + Cl- (complete transfer)
To pull electrons away from an atom requires input of energy



Partial transfer
More electronegative  more energy needed
When electrons shift from less electronegative to more electronegative atom  Electron loses potential energy, which is released as heat






C
6
H
12
O
6
C
6
H
12
O
6
+ 6O
2
 6CO
2
+ 6H
2
O + energy is oxidized/reduced while O
2 is oxidized/reduced
C
6
H
12
O
6 is the _____agent while O
2 is the ____ agent.
This reaction is considered exergonic/endergonic , therefore it is spontaneous/not spontaneous and has a
+/change in free energy
Why are many organic molecules great fuels?
When a spark is applied to gasoline and oxygen it burns and releases a LARGE quantity of energy. Why doesn’t glucose do the same thing in the presence of O body?
2 in your



Enzyme facilitate the break down of organic fuels to CO
2 in a SERIES of steps. Why not just one step?
Electrons (along with a proton) are stripped from glucose, but not directly to O
2
, instead they are transferred to…





NAD
Conezyme derived from the vitamin niacin
NAD ox vs NAD re
Very little PE lost
Energy can be tapped into when ATP needs to be made

 How do electrons finally reach oxygen?

Substrate level phosphorylation


Enzymes transfer a phosphate group from the substrate to
ADP
In oxidative phosphorylation
(discussed tomorrow) inorganic phosphate is added to ADP

Glycolysis “splitting of sugar”




Location?
Inputs?
Outputs?
Purpose?

Fermentation

Lab 5: Cellular Respiration

Lab 5: Cellular Respiration
 Description
 using respirometer to measure rate of O
2 production by pea seeds
 non-germinating peas
 germinating peas
 effect of temperature
 control for changes in pressure & temperature in room


Lab 5: Cellular Respiration
Concepts
 respiration
 experimental design
 control vs. experimental
 function of KOH
 function of vial with only glass beads

Lab 5: Cellular Respiration
 Conclusions


 temp =
 respiration
 germination =
 respiration calculate rate?

Sources of energy
Photosynthesis
(photoautotroph)
Autotrophs (self-feed from CO2 and inorganic materials): plants, some algae, some bacteria
Synonym: Producers
Chemosynthesis (chemoautotroph)

Chloroplast structure
Read through :birth of complex cells to get further detail about other plastids and organelles such as peroxisomes
Water: roots  veins  mesophyll cells
Sugar: mesophyll cells  veins  rest of plant
CO2, O2  stomata

Absorbing/reflecting light


Problem: How do plants utilize energy from light to produce carbohydrates?
Properties of light
 While traveling, acts as a wave (properties depend on this wavelength)
 When interacting with matter
(like your clothes) acts as a particle
 Photon: Discrete packet of light

Pigment structure/function

Pigment structure/function
 When chlorophyll absorbs light, energy is transferred to electrons.
Plant pigments
Chlorophyll a : primary pigment
Chlorophyll b : broadens range of wavelengths that can be used
Carotenoids : Also broadens range, absorbs, dissipates excessive energy, prevents interaction w/ O2
EAT YOUR CARROTS, why?

Light dependent reactions
 Role of chlorophyll:
Capture energy from light
 Role of an electron carrier: transport electrons which carry the energy initially from light
(NADP+ + 2e- + H+
 NADPH)

6CO
2
+ 6H
2
O light
>
C
6
H
12
O
6
+ 6O
2



Where does the O2 come from?
Hypothesis 1: CO2 + C  C + O2
C + H2O  CH2O
Hypothesis 2 (van Niels)

Studies bacteria that DIDN’t produce O2


CO2 + 2H2S  CH2O + H2O + 2S
CO2 + 2H 2O  CH2O + H2O + O2

Visible globules
Confirmed with radioactive tracers to track its fate

REDOX chemistry


 REDOX! Water is split  electrons and Hydrogen ions to CO2. Electrons increase in potential energy, so energy is NEEDED! (endergonic, + ΔG)
CO2 is reduced to sugar
H2O is oxidized

Photosynthesis overview


NAD P + : Same function as NAD+
Photophosphorylation

How do photosystems work?
 Only photons with energy equal to the atoms ground state  excited stated is absorbed
Redox Why does isolated chlorophyll fluoresce?

Noncylic electron flow

Noncylic electron flow

Noncylic electron flow

Noncylic electron flow

Noncylic electron flow

Noncylic electron flow

Cyclin electron flow
Function: Regenerate ATP lost through Calvin Cycle (more
ATP consumed than NADPH)

Electron transport chain
Location: _____
Input: ______
Output: ___
Purpose: _____

Chemiosmosis comparison

Calvin Cycle
 Purpose: _____
 Location: ____
 Input : ____
 Output : ____

Lab 4: Photosynthesis


Lab 4: Photosynthesis
Description
 determine rate of photosynthesis under different conditions
 light vs. dark
 boiled vs. unboiled chloroplasts
 chloroplasts vs. no chloroplasts
 use DPIP in place of NADP +


DPIP ox
= blue
DPIP red
= clear
 measure light transmittance
 paper chromatography to separate plant pigments


Lab 4: Photosynthesis
Concepts
 photosynthesis
 Photosystem 1
 NADPH
 chlorophylls & other plant pigments
 chlorophyll a
 chlorophyll b
 xanthophylls
 carotenoids
 experimental design
 control vs. experimental

Lab 4: Photosynthesis
 Conclusions
 Pigments
 pigments move at different rates based on solubility in solvent
 Photosynthesis
 light & unboiled chloroplasts produced highest rate of photosynthesis
Which is the control?
#2 (DPIP + chloroplasts + light)