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Photosynthesis and Cellular Respiration
Transcript of Photosynthesis and Cellular Respiration
Photosynthesis and Cellular Respiration
These eleven questions are more than half of your next big test (after the Disease Test). If you can answer each one of the previous slides in detail at the biochemical and cellular level, you will do just fine on the exam!
Why do you inhale?
Specifically, inhale O2. Where does it go and for what is it used?
Why do you excrete solid waste???
From where specifically do the solids originate, and why?
Why do you excrete liquid waste???
From where SPECIFICALLY does the liquid waste originate?
Why do you eat????
Ingesting solids—what happens to them ultimately and WHY??
Why do leaves change color in the fall?
Describe all specifics involved!
Where does the water that life needs to function really come from?
DETAILS of the process at the organelle level!!
Why are most plants GREEN??
The specific biochemistry and light physics behind COLOR?!
THE eleven questions for survival in this unit
The BIG PICTURE 28
Why do you exhale?
Specifically, exhale CO2. From where does the waste gas come and why?
Why do you drink???
H2O primarily, and includes all other liquids since they are water-based. What happens to the water?
Compare/contrast chloroplast vs. mitochondrion structure and function
Where does the oxygen that animal life breathes come from?
DETAILS of the biochemistry process!!!
The Calvin Cycle will continue to process and rearrange the 3-carbon PGAL molecules until two of them are joined together to form a single glucose (C H O ). Glucose will form the entire basis, then, of energy that originally came from the sun and gets transferred into the bonds of the glucose molecule, allowing it to be stored, built upon, transported throughout the plant, or used immediately by the plant’s mitochondria to make a LOT of ATP for other cellular reactions.
Chemical concentration differences of H+ ions as water is broken down outside the chloroplasts can also provide a source of energy to form the ATP molecule. All of the ATP formed this way goes on to provide the energy for the dark rxns.
Also, the H O breakdown is what gives the waste product formation that animal life needs to survive: O !
We get our oxygen from a plant breaking down water in the light rxns. of photosynthesis!
Photosynthesis uses two sets of reactions (Stages) to make ATP and sugar: the light-dependent rxns. and the dark (or more accurately light-INdependent) rxns.
Light rxns. occur in the inner membranes of the chloroplasts called thylakoids, and the dark rxns. occur in the outer folds/fluid of the chloroplasts called the stroma
Remember the structure of the chloroplast and be able to compare/contrast it with a mitochondrion!
(YES, you need to spell this correctly!) is a plant pigment which absorbs certain wavelengths of light energy (mostly in the red and blue areas) and reflects back other colors
THIS is why most plants are GREEN!!
The energy in NADPH is broken off and used to join a 5-carbon molecule with CO
to form 2 molecules of a 3-carbon basic building block called PGAL (glyceraldehyde phosphate or phosphoglyceraldehyde). This basic building block is the essential “ingredient” in every type of sugar on the planet.
The joining of the C with CO is catalyzed by the enzyme
, the most abundant protein in the world.
Dark Rxn. Specifics
(The Calvin Cycle)
Provide the means of converting the energy carriers (NADPH) into sugar and do NOT require sunlight. These rxns. occur ALL THE TIME, not JUST in the dark. A process of reactions called the Calvin Cycle takes the energy stored in the NADPH molecules and uses it to convert other carbon compound molecules into glucose in a series of step-by-step transfers.
The “Dark” Reactions:
During the light rxns., sunlight causes molecular “excitation” or increased energy that is transferred from one chlorophyll molecule to another in a chain reaction of electron transport until special enzymes finally use the energy to add an electron onto an intermediate carrier called NADP+
NADP+ + e- NADPH
Water is broken down during the light rxns. to constantly replace the electrons being transferred from all the chlorophyll
Which is made up of the nitrogen base adenine plus ribose sugar, plus three (3) phosphate groups which store energy in their bonds. When these bonds are broken, the stored energy is released for chemical reactions and work to be done.
= the conversion of sunlight into chemical energy trapped in the bonds of sugar molecules (from autotrophs)
6 CO + 6 H O C H O + 6 O
The formation of cellular energy
Cellular energy is based on the formation of storage molecules called: (drum roll, please):
A.T.P. (adenosine triphosphate)
The breakdown of glucose for further energy needs. In both auto- and heterotrophs is simply the reverse of the photosynthesis rxn. but instead of requiring energy (sunlight), this rxn. releases it (3811 calories per gram of glucose)
calorie = amt. of heat energy to raise 1 gram of water 1 degree Celcius
Kcal or Calories = 1000 calories (read the nutrition labels on any food product!)
Stage 1—Glycolysis (Intro)
There will be several “intermediate” carriers and coenzyme components along the process that transfer e- ions from organic molecules, such as NAD+ and FAD++ This ability to transfer high-energy ions to other molecules ultimately results in the formation of “storage batteries” for energy, known as ATP
3. Electron transport and oxidative phosphorylation—aerobic, to get the most ATP from the products of the previous two stages; occurs across the cristae (inner membrane) of the mitochondria
Life = order. Specific, structured, patterned and organized. But the nature of the universe tends towards the chaotic, to achieve the lowest energy level “resting” stage possible. So life, by its very existence, is inherently intrinsically unstable. Therefore, energy must be constantly expended by living things in order to maintain their existence against the randomness of the universe. HOW??
Glycolysis and/or fermentation worked great for the first developed lifeforms on earth, the single-celled ones. However, any more complex forms of life needed to have more energy to live. Not possible UNTIL the incorporation of the mitochondrion into cells billions of years ago. By having a specialized organelle that did nothing but make ATP, organisms had the energy to get more complicated, ultimately giving rise to multi-cellular organ systems.
9-step series of reactions to break down one (1) molecule of glucose into two (2) 3-carbon molecules of pyruvate (pyruvic acid), ultimately producing two (2) net molecules of ATP and 2 molecules of NADH. Occurs in the cytoplasm of all cells. Very inefficient!!
Some anaerobic single-celled organisms can take the pyruvic acid and continue its breakdown through fermentation, getting a bit more ATP from each molecule of glucose. Still inefficient!
Entire point of all of three stages is to transfer electrons and form “unstable” phosphate group compounds (ATP), which, when attached to other molecules, makes them reactive and usable for work energy. THIS is how chemical reactions take place in living systems!
1. Glycolysis—anaerobic in the cytoplasm of cells; the most simple and primitive process of gaining energy; ALL lifeforms on this planet use it!
2. Krebs Cycle (Citric Acid Cycle)—also anaerobic directly, although must have oxygen for stage 3 below or process stops; occurs in the mitochondria of cells
Cellular Respiration is a 3-stage breakdown process:
ANY organic compound (we will use C H O since this is the simplest sugar) + oxygen
CO + H O + ATP (energy)
That’s it!! Does this equation look at all familiar?
Now the SPECIFICS are going to get a bit more complicated…
THE equation for cellular respiration!
There are two major pathways that life uses to gain energy to fight randomness, both of them catabolic (breakdown, or digestive):
Fermentation—partial sugar breakdown that is anaerobic (no oxygen)
Cellular respiration—more efficient aerobic breakdown of substances
The exact specifics on HOW life (as we know it) functions
Cellular Respiration 25
The oxaloacetate at the end of each turn of the Krebs Cycle gets recycled back to the NEXT turn, to add to another decarboxylated pyruvic acid, keeping the process going.
REMEMBER, if you start with ONE molecule of glucose at the beginning, EACH pyruvic acid molecule @ the end of Stage 1 goes through the Krebs Cycle, doubling the number of ATP, FADH2 and NADH (and CO2 and water waste) that is produced! Remember this in calculating your numbers!
All of the NADH and FADH2 produced in Krebs AND in Glycolysis now goes into Stage 3 to generate MUCH more ATP than would have been normally possible…
Anything in GREEN = products that leave the Krebs Cycle, either as waste or move on to Stage 3
Anything in BLUE = components that must be added in to keep the rxns. going
Those in RED are recycled back through the next set of Krebs rxns.
The electrons that are broken off and transferred to the carrier molecules are coded in GOLD
LIGHT BLUE CIRCLES at the top of each slide indicate which reaction is happening…
KREBS CYCLE REACTIONS
10 reactions from pyruvic acid breakdown to get MORE ATP and especially more NADH for Stage 3 conversion.
Occurs in the matrix of the mitochondria
Needs a precursor reaction to allow it to start:
Oxidative decarboxylation—removal of a carboxyl group (COOH) from pyruvic acid. Waste carbon group = poopie! (Another possibility exists that the COOH group COULD become CO2 and a hydrogen atom, to be EXHALED!)
The Krebs Cycle #35
Succinate + FAD++ Fumarate
(Succinate is now able to donate two electrons to a more
efficient carrier molecule)
Isocitrate + NAD+
Oxalosuccinate + NADH
(The isocitrate loses an electron that is
picked up by the first of the electron
carrier molecules, altering its shape by
Acetyl (C ) CoA + Oxaloacetate (C )
Citric Acid (C )
(The pyruvic acid that has undergone oxy. decarb. becomes the two-carbon acetyl molecule that is unstable. Temp. bonding to CoEnzyme “A” allows it to enter the matrix and begin the Krebs Cycle by bonding to the four-carbon oxaloacetate molecule left over from the previous turn of the last Cycle)
Pyruvic acid (C H O ) Acetyl (C H O)
This reaction DOES require energy input to make it happen (ATP use)
The now-two-carbon acetyl molecule is small enough to enter the matrix of the mitochondria to start the Krebs Cycle
Malate + NAD+ Oxaloacetate (C4 )
(Malate loses a final electron to the last carrier molecule and becomes the four-carbon oxaloacetate. Guess what happens to it??)
Fumarate + H2O Malate
(The addition of two more hydrogen atoms and another oxygen atom from water turns fumarate into malate. Becha can’t guess where the water comes from??)
Ketoglutarate + NAD+ - CO2
Succinyl CoA + NADH
(The Ketoglutarate loses one electron, two oxygens and one carbon, becoming a molecule of succinyl, which is unstable and needs to be held together by temp. bonding to CoEnzyme “A”)
Aconitate + H2O Isocitrate
(The aconitate now gains BACK two hydrogen atoms
and one oxygen atom IN DIFFERENT PLACES on the
molecule to make ISOcitrate. Significance? WHY?
Where does the water come IN from??)
Citric Acid – H2O Aconitate
(Citric acid loses one atom of oxygen and two atoms
hydrogen from particular places on the molecule, that
will combine together AFTER breaking off to become
a water molecule. Guess where it goes??)
Succinyl\ CoA + ADP Succinate
+ ATP + CoA
(Once succinyl loses another electron, it becomes more
stable and no longer needs the CoA to hold it together. So
where does the CoA go? The electron donation this time
generates the only ATP in the Krebs Cycle rxns.)
Oxalosuccinate - CO2
(The oxalosuccinate loses two molecules of oxygen and one of carbon that will combine together AFTER breaking off to form carbon dioxide. Guess where it goes??)
For everything else, see the Powerpoint!!