Cell Unit II: Respiration and Photosynthesis

Themes:

The cell, Structure and Function, Regulation, Evolution, Interaction

with the environment

Objectives for Respiration:

Cellular Respiration and Metabolism are catabolic

Cells recycle ATPRespiration involves: Glycolysis, Krebs

Cycle and ETCFermentation: Lactic Acid, AlcoholicFeedback Mechanisms control cellular

respiration

Root Words

Aero – airAn – notChemi – chemicalGlyco – sweetLysis - split

Cellular Respiration is:

Catabolic Pathway

Exergonic- Products have less energy than reactants.

- G 686 KC/mole of Glucose (approx. 40% efficient).

C6H12O6 & 6 O2 6 H2O & 6 CO2 & Energy (ATP)

(Same as combustion - example gasoline)

ENERGY FLOW AND CHEMICAL RECYCLING IN ECOSYSTEMS.

Chemicals are recycled but energy is not. Energy leaves the system as heat and must be put back into the system by sunlight.

RESPIRATION:RESPIRATION: is a series of REDOX REACTIONS.

(Reduction/Oxidation)

Oxidation -Loss of electrons (H+) also the reducing agent.

Reduction - Gain of electrons (H+) also the oxidizing agent.

LEO goes GERL- LoseE- ElectronO - Oxidation

G - GainE- ElectronO - Reduction

CC66HH1212OO66 & 6 O & 6 O22 6 CO 6 CO22 & 6 & 6 HH22OO

Undergoes oxidation

Undergoes reduction

(Reducing agent)

(Oxidizing agent)

REDOX EXAMPLE: with the use of coenzymes

GLUCOSE Enzymes called Dehydrogenates rip 2H+ off glucose in pairs (2 e & 2 p).

One proton goes into cell solution . The 2e & 1p are picked up by coenzyme (NAD+) & forms NADH. (Glucose is oxidixed & NAD+ is reduced.)

Respiration & Combustion release the same amount of energy (combustion releases it faster)

steps

enzymes

Respiration Lab - # 5

We will be using Vernier Probes

SUBSTRATE-LEVEL SUBSTRATE-LEVEL PHOSPHORYLATIOPHOSPHORYLATIONN

The enzyme takes a substrate that has a phosphate & transfers it to an ADP making it ATP.

EXAMPLES:EXAMPLES:

Pg. 163 reaction # 7 & 10.

OXIDATIVE PHOSPHORYLATION: what is phosphorylation?2H’S From Glucose taken by NAD+ pass their electrons through the Electron Transport Chain (ETC) releasing energy that converts ADP to ATP.

10 steps

8 steps

Each step of respiration is controlled by a different enzyme. (Compare to next slide Fig. 9.16)

GLYCOLYSIS - 1ST 10 STEPS OF RESPIRATION:GLYCOLYSIS - 1ST 10 STEPS OF RESPIRATION:

Glucose(6 C’s) is split into 2 pyruvate molecules (each 2 C’s) Each Pyruvate is an acidEach step has a different enzyme.

This is anerobic respiration (without using O2)

Believed to be most ancient of metabolic processes since it does not need O2; found in all eukaryote & prokaryote cells. The enzymes are in cytosol not in the mitochondria.ATP made only through substrate-level Phosphorylation. (net gain is 2 ATP & 2 NADH)

REMEMBER- NAD+ to NADH (NAD+ reduced) so a substrate went through oxidation.

Substrate phosphorylation yields only 4 ATP

Oxidative phosphorylation yields 34 ATP/ mole of Glucose.

FIG. 9.8.FIG. 9.8.

Formation of 2 pyruvates; 2 ATP by substrate -level Phos. & 2 NADH. (REDOX Reactions)

FIG. 9.9

This is where the 6 carbon molecule is split into 2 3 carbon molecules.

FIG. 9.9FIG. 9.9Here is where 2 ATP are formed (sub-lev. Phos.) and the net gain of 2 ATP, the final product of Glycolysis is formed (pyruvate).

This is the step between the end of GLYCOLYSIS & the beginning of the KREBS CYCLE.

Each Pyruvate loses a CO2 & NAD+ is reduced to NADH and Coenzyme A is added to the molecule making

Moving from: Cytosol to the mitochondria

This molecule enters the KREBS CYCLE

4c

2c2c2c

6c

5c

4c

4c

4c

4c

KREBS CYCLE:Note the following:

(A) Where Acetyl CoA comes into reaction.(B) Where CO2’s are produced.(C) Where coenzymes FADH2 & NADH are reduced.(D) How # of carbons change.

Pyruvate from Pyruvate from Glycolysis Glycolysis converted into converted into Acetyl CoAAcetyl CoA

Substrate level Phos.here

6c

2 turns for each glucose molecule

PARTS OF MITOCHONDRIA:PARTS OF MITOCHONDRIA:

(A) Inner Mitochonrial Membrane

(B) Outer Mitochondrial Membrane

(C) Cytosol

(D) Mitochondrial Matrix

(E) Intermembrane Space

F

(F) Cristae -increases surface area.

ELECTRON TRANSPORT CHAIN (ETC)ELECTRON TRANSPORT CHAIN (ETC)

(Located in the inner mitochondrial membrane)

The electrons of the H of NADH & FADH2 that was reduced in Glycolysis & Krebs Cycle enter the ETC.

The Proton of the hydrogen does not enter the ETC.

The electron moves from one compound of ETC to another. (oxidation/reduction)

Electrons release energy as they move from compound to compound of the ETC.

Last compound of ETC releases electron which joins with a proton to make (H) again.

When 2 electrons go through ETC we get 2H. These join with metabolic oxygen to make metabolic water.

***** O2 is to be the final electron acceptor of electron of glucose.*****

Chemiosmosis: How the Mitochondrial membrane couples ETC with Oxidative PhosphorylationAs NADH passes through the ETC, this energy is used to pump H+ ions (protons) from M. Matrix to Intermembrane space.(H+ not from H of NADH)This causes PROTON MOTIVE FORCE. (More H+ in Internal Membrane Space than in Membrane Matrix.)

These H+ ions will “leak” back into the M. Matrix through a protein complex (integral proteins) and this will release enough energy to join ADP with a (P) to make ATP.

IMPORTANT STATEMENT: Since most ATP formed is from oxidative phosphorylation, ATP yield in respiration needs a supply of O2.Since O2 “pulls” electrons down the ETC then if there is not enough Oxygen the ETC will stop (and stop ATP formation).

FERMENTATION - is a process that some cells can use to oxidize food and make ATP without the use of O2.

FERMENTATION - anaerobic respiration bc it is respiration without oxygen.

(Glycolysis is already anaerobic.)

Lactic FermentationLactic Fermentation - Pyruvate can’t enter Krebs Cycle since there is O2 available at the end of the ETC. (All NADH’s are filled and have no where to go). This process is done in human muscle cells, fungi & bacteria.

2 Pyruvates are reduced to Lactate (lactic acid) forming the production of 2 ATP.

In Human muscle cells, this causes muscle fatigue & sometimes pain early in strenuous exercise.

This is when sugar catabolism for ATP outpaces muscle’s supply of O2 in the blood.

Sometimes called O2 debt

ALCOHOL FERMENTATION –Note this is similar to Lactic Fermentation, except CO2 is given off and 2 pyruvates are reduced to Ethanol (Ethyl alcohol.) (2 ATP again).This is substrate-level phosphorylation.

This process happens in yeast and makes alcohol and in bread the CO2 causes bread to rise.

Many bacteria also carry out this process.

Objectives for Photosynthesis:

Plants & other Autotrophs are producersSite of photosynthesis – chloroplastsLight reactions and Calvin Cycle – convert

light energy to chemical energyAlternative mechanisms in hot, dry

environments

Root WordsAuto – - TrophChloro – - phyllElectro –

Magnet –

Hetero –

Meso –

Photo -

SUMMARY REACTION:SUMMARY REACTION:

6 CO2 & 6H2O C6H12O6 & 6 O2

PHOTOSYNTHESIS AS A REDOX REACTION:

RespirationRespiration - energy released from glucose when electrons that came from H are transported by carriers (ETC) to O2 forming H2O. Electrons lose energy as O2 pulls them down the ETC and mitochondria use this energy to make ATP.

PhotosynthesisPhotosynthesis - reverses flow of electrons. Water is split & electrons are transferred along with H ions from water to CO2 reducing it to sugar. The required energy is provided by light.

TYPES OF FEEDERS IN A TYPES OF FEEDERS IN A BIOSPHERE:BIOSPHERE:Autotrophs – “self-feeders” -green plants (AKA producers.) Make organic compounds with light.

PLANTS are Photoautotrophs.

Heterotrophs – “Other feeders” Can’t make their own food.Decomposers: are Heterotrophs that consume the remains of dead organisms. (Detritivores)

Chemoautotroph - produce organic compounds without the use of light. Some Bacteria, think Deep Sea thermal vents

Sites of PhotosynthesisSites of PhotosynthesisLIGHT REACTIONLIGHT REACTION (1st steps) – within Thylakoid membrane. DARK REACTION ( Calvin Cycle ) -DARK REACTION ( Calvin Cycle ) - (2nd steps) – within Stroma.

ETCETC in the Thylakoid membrane will also be involved in chemiosmosis

Fig. 10.4 OVERVIEW OF Fig. 10.4 OVERVIEW OF PHOTOSYNTHESIS.PHOTOSYNTHESIS.

NOTE:NOTE:

H2O is used & releases O2ATP & NADPH is made in Light reaction & used in Calvin Cycle.

(Entire process happens in the chloroplast.)

LIGHT & PHOTOSYNTHESIS: (Fig. 10.5)LIGHT & PHOTOSYNTHESIS: (Fig. 10.5)

Light “acts” as though it was particles, even though it is not.The packets of energy in light are called “photons”.NOTE:NOTE: Energy in light is inversely proportioned to it’s wavelength.

Higher wavelength = Lower energy & vice versa.

EXICITED/“ENERGIZED” ATOMS OF CHLOROPHYLL EXICITED/“ENERGIZED” ATOMS OF CHLOROPHYLL aa

(A) Certain atoms within chlorophyll absorb a “photon” from light & move from ground state to a higher level. (This means that atom now has more potential energy.)(B)

REMEMBER:REMEMBER: Orbits AKA energy levels (further e- is from nucleus = more energy).

(C) Atom stays in this “excited” state for a billionth of a second, then return to ground state & release their energy.

Sometimes electrons picked up by NADP+

Photoexcitation of a Chlorophyll a Photoexcitation of a Chlorophyll a Molecule.Molecule.Same as last slide. Note e- moving from ground to excited state by photon of light.

Excited photon releases energy(heat) & photon returns to ground state.

NoteNote: the pigments of chlorophyll absorb blue & red light which are the most effective in photosynthesis. Pigments reflect green light (the least effective in photosynthesis).Chlorophyll a is green

(participates directly in the light reaction converts solar to chemical energy.)Chlorophyll b is accessory pigment & is yellow-green.

Carotene and Xanthophyll are accessory pigments that are shades of yellow & orange.

Chromatography Lab - #4

Spinach Lab Variation

ABSORBANCE SPECTRAABSORBANCE SPECTRA - Note the wavelengths at which each pigment is absorbed.NOTE:NOTE: Green part of spectrum notnot useful for photosynthesis. Notice other colors which are useful for photosynthesis

Light absorption verses wavelength.

Experiment Demonstrating the Action Experiment Demonstrating the Action Spectrum for Photosynthesis Spectrum for Photosynthesis

(A) Algae illuminated with light that had been passed through a prism (to get the spectrum of light).

(B) Aerobic bacteria were put with algae. They would go to O2 source.

(C) Bacteria went to where Photosynthesis would release O2.

(where red & blue light are) SAME PATTERN AS ACTION SPECTRUM.

HOW A PHOTOSYSTEM HARVESTS LIGHTHOW A PHOTOSYSTEM HARVESTS LIGHT

Photosystems are a complex of proteins & other molecules.A photon hits a pigment molecule, the energy is passed from molecule to molecule until it reaches the reaction center of chlorophyll.

Here, the energy drives a Redox reaction.

Excited e- from reaction center of chlorophyll is captured by primary e- acceptors.

Photosystem I :Photosystem I :Chlorophyll a reaction center called P700 because the pigment is best absorbed by a wavelength of light at 700 nm

Photosystem II:Photosystem II:Chlorophyll a reaction center called P680 because the pigment is best absorbed by a wavelength of light at 680 nm.

Both chlorophyll a’s are identical but different proteins present in each cause the chlorophyll a to have different light- absorbing properties.

Both photosystems are involved in Noncyclic Electron flow but Photosystem I is involved in Cyclic Electron Flow.

NONCYCLIC ELECTRON FLOW:NONCYCLIC ELECTRON FLOW:REMEMBER: how a photosystem harvests light !!! This is happening in the Thylakoid membrane.

Enzyme extracts electrons from water replacing electrons lost from P680.

NOTE:NOTE: O2 lost from water is released by Photo.

Photophosphorylation (noncyclic)

CYCLIC ELECTRON FLOW: CYCLIC ELECTRON FLOW: Everything inEverything in

black does NOT take place.black does NOT take place.

This uses Photosystem I not Photosystem II.The ATP produced is from cyclic

photophosphorylation.

NOTE: There is no NADPH produced & no release of O2.

Chemiosmosis in both mitochondria & Chloroplast. (which bothboth occur in plants.)

NOTE:NOTE: Same process except performed in different parts of the cell.

Stroma

The 2 Photosystems & how they relate to The 2 Photosystems & how they relate to the ETC & Chemiosmosis. the ETC & Chemiosmosis.

NOTE:NOTE: Both light reaction & the Calvin Cycle stop after dark. Photosyn. does not occur at night!

THE CALVIN CYCLE: (AKA Dark Reaction THE CALVIN CYCLE: (AKA Dark Reaction or Light Independent Reaction)or Light Independent Reaction)

(A) Uses ATP & NADPH made during the light reaction for energy & recycled back to the light reaction as ADP & NADP+.(B) CO2 enters & leaves in the form of sugar.(C) Rubisco (also called ribulose biphosphate carboxylase) is the most important enzyme used in the 1st step.

Most abundant protein on the earth

3 cycles to make 1 glucose molecule

Major Major compouncompound d producedproduced..

PHOTORESPIRATION & THE CALVIN CYCLEPHOTORESPIRATION & THE CALVIN CYCLE1) Calvin Cycle is 1st fixation of CO2 with RuBP(ribulose biphosphate)2) Plants discussed so far are C3 Plants since CO2 is fixed with a 3 carbon compound.(A) Hot dry day - stomata close - thus CO2 intake

stops.(B) Plants use up CO2 starving the Calvin Cycle.(C) Rubisco will now accept O2 in place of CO2 & this is added to the Calvin Cycle.(D) 2 carbon compound formed & exported to mitochondria to be broken down.

(E) Photorespiration now takes place -this makes no ATP thus decreases photosynthesis output.

CC44 PLANTS: PLANTS: (called this because they fix CO2 into a 4 carbon compound.) CO2 fixed in the mesophyll cells but the Calvin Cycle takes place in the Bundle-sheath cells.An enzyme called PEP carboxylase adds CO2 to a substrate called PEP.

PEP carboxylase has a higher affinity for CO2 than RuBP carboxylase (rubisco)New 4 C compound exported to the bundle-sheath cells (through plasmodesmata.)

4 carbon compound (Malate) releases CO2

which is re-assimilated into organic material by Rubisco in the Calvin Cycle.What really happens - this keeps CO2 concentration high enough in bundle-sheath cells to allow Rubisco to accept CO2 rather than O2.This minimizes photorespiration and enhances photosynthesis.Important plants such as sugarcane & corn are C4 Plants.

CAM PLANTS:CAM PLANTS: (in water storage plants such as cacti & pineapples called succulents.) ARID ARID CONDITIONS.CONDITIONS.

Open stomata during the night & close them during the day. (reverse of other plants).

1) This helps desert plants conserve water, but CO2 can’t enter the leaves.

2) CO2 is fixed in organic acids during the night in vacuoles when stomata are closed.

3) During the day, light reaction supplies ATP & NADPH for the Calvin Cycle. CO2 is released from organic acids to be used to make sugar.

Fig. 10.19 A REVIEW OF Fig. 10.19 A REVIEW OF PHOTOSYNTHESIS.PHOTOSYNTHESIS.