Phosphate available--cell has an unlimited supply of energy.
Energy from Fuels
Digest large molecules into smaller ones
break bonds & move electrons from one molecule to another
as electrons move they “carry energy” with them
that energy is stored in another bond, released as heat or harvested to make ATP
Move electrons in Biology
“Glucose is like money in the bank; ATP is like money in your pocket”
We can write the overall reaction of this process as: 6H2O + 6CO2 ----------> C6H12O6+ 6O2 six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen Basically Opposite of Cellular Respiration
Photosynthesis
Two Reactions of Photosynthesis
Light Reaction ☼ – Light energy (sun) into chemical energy.
Thylakoid Disk
Produces ATP to power Light Independent Reaction.
Oxygen Released
Light Independent Reaction/Dark Reaction (Calvin Cycle) – Uses chemical energy to “Fix” Carbon dioxide into sugar.
Uses ATP and Electrons from Light Reaction
Stroma
Mesophyll Cells
Specialized cells in the middle of the leaf that contain a lot of chloroplast for photosynthesis
Chloroplast: Organelle where photosynthesis occurs Thylakoids-Site of light dependent reactions Grana: Stack of Thylakoids
Chloroplasts
Stomata (stoma) Pores in plant’s cuticles through which water vapor and gases are exchanged between the plant and atmosphere (underside of leaves)
Pigments: Molecules that absorb specific wavelengths of light (Plants: Chlorophyll-absorbs and transfers light energy)
**Chlorophyll forms a and b absorb most wavelengths except green. Because it doesn’t absorb it, it reflects it, hence green appearance.
Fall Colors
Pigments other then chlorophyll
Chlorophyll reduced revealing other pigments (carotenoids that are red, orange or yellow)
Light Dependent Reaction —“photo” of photosynthesis
1.)The light absorbed by chlorophyll causes a transfer of electrons and H+ from H20 molecules already present. This causes the H20 to split into molecular 0xygen (02) and a H+ ion (photolysis). 2.) The O2 is released (we breathe it) and the H+ bonds to NADP+ creating NADPH 3.)ATP is formed through photophosphorylation. (ADP gets a phosphate group added to it creating ATP) 4.) The NADPH and the ATP created here go on to fuel the reactions in the second part of photosynthesis - The Calvin Cycle
Photolysis: light causes water molecule split. Hydrogen to bind to an acceptor, subsequently releasing the oxygen.
Equation: H2O > 2H + O
Function:
Release O2 gas to the atmosphere
Replaces lost electrons
Calvin Cycle/Light Independent
“synthesis” of photosynthesis, making food, trapping CO2.
Rubisco (enzyme) brings together CO2 and sugar, carbon fixation
3 CO2 (atmosphere) and 3, 5-carbon sugars (RuBP).
PGA Formation-Six-carbon product is unstable and splits into 3-carbon products (PGA).
ATP places a phosphate group on each PGA: NADPH donates a pair of electrons, yielding a high energy food, PGAL.
Calvin Cycle Completes
Glucose Production-After several rounds 2 PGAL leave to form glucose
Replenish RuBP (Ribose Biphosphate) Some PGAL reform 5-C Sugar-begin process again
Mitochondria break down glucose to produce energy (ATP)
Overview
Every cell (plants and animals)
Exergonic Reaction(produces energy)
Equation-
C6H12O6 + ADP 6CO2 + 6H2O + ATP
Oxidation/Reduction Reactions
Oxidation
adding O
removing H
loss of electrons
releases energy
exergonic
Reduction
removing O
adding H
gain of electrons
stores energy
endergonic
C6H12O6
6O2
6CO2
6H2O
ATP
+
+
+
oxidation
reduction
Cellular Respiration
Overview three stages:
Glycolysis
Cytoplasm
Glucose splits
Forms pyruvate (Intermediate-Acetyl CoA)
Citric acid cycle (Kreb Cycle)
Converts Acetyl CoA into CO2
Occurs in Mitochondrial Matrix
Electron transport chain
ATP Synthesized
Glycolysis— “Sugar” splitting
CYTOPLASM
Yields little energy
No oxygen required (anaerobic)
Glucose (6 carbon sugar) → 2 Pyruvate and 2 ATP
Prokaryotes and single celled organisms-sole source of energy.
History of Energy Harvest
Energy transfer first evolved
transfer energy from organic molecules to ATP
still is starting point for ALL cellular respiration
Evolution
Prokaryotes
first cells had no organelles
Anaerobic atmosphere
life on Earth first evolved without free oxygen (O2) in atmosphere
energy had to be captured from organic molecules in absence of O2
Prokaryotes that evolved glycolysis are ancestors of all modern life
ALL cells still utilize glycolysis
Glycolysis Reactants and Products
REACTANTS
1 glucose
Enzymes
2 ATP are needed
2 Pyruvates
4 ATP (net gain 2)
2 NADH (go to Electron Transport Chain (ETC))
Pyruvic acid forms Acetyl CoA
Mitochondrion
Pyruvic Acid combines with Coenzyme A to form acetyl CoA
Intermediate step Reactants and Products
REACTANTS
2 pyruvates (glycolysis)
PRODUCTS
2 Acetyl CoA (Go to Kreb Cycle)
2 CO2 (released as waste)
2 NADH (ETC)
Citric Acid Cycle (Kreb Cycle)
Mitochondria
Series of reactions
Generates electrons for ETC
Aerobic- Needs Oxygen
The Krebs cycle has five main steps. It starts with one molecule of Acetyl CoA (formed at end of glycolosis)
The Krebs cycle has five main steps. It starts with one molecule of Acetyl CoA (formed at end of glycolosis)
Step 1: Acetyl CoA, a two-carbon molecule, bonds with four-carbon oxaloacetic acid to form six-carbon citric acid.
Step 2:Citric acid releases a molecule of CO2 and a hydrogen atom, becoming a five-carbon compound. The hydrogen atom bonds with NAD+, reducing it to NADH.
Step 3: The five-carbon compound releases another CO2 molecule and a hydrogen atom, which again bonds with NAD+, producing NADH. This step is the same as step 2, except in this step one molecule of ATP is formed from an ADP and a phosphate.
Step 4: The new four-carbon compound releases another hydrogen atom. This time, the atom reduces a molecule of FAD to FADH2.
Step 5: The four-carbon molecule formed in step 4 releases a hydrogen atom, reforming oxaloacetic acid. hydrogen atom reduces another molecule of NAD+ to NADH.
Since one glucose molecule is converted into two pyruvic acid molecules by glycolysis, the Krebs cycle completes two turns for every molecule of glucose. This makes it produce 6 NADH molecules, 2 FADH, 2 ATP molecules, and 4 CO2 molecules.
Citric Acid cycle
REACTANTS
2 Acetyl CoA
PRODUCTS
4 CO2 (waste)
6 NADH (ETC)
2 ATP
2 FADH2 (ETC)
Citric Acid Cycle/Kreb Cycle
Electron Transport Chain:
Mitochondria
Series of reactions-electrons transported through chain
NADH and FADH2 from Krebs Cycle carry electrons
Electron route: food---> NADH ---> electron transport chain ---> oxygen
Oxygen used
Water released
Electron Carriers Move electrons by shuffling H+ around
NAD+ → NADH
FAD+ → FADH2
like $$ in the bank
reducing power!
Steps of Electron Transport Chain
Carrier molecules arrives, bumps the ETC’s first carrier, which accepts the electrons, then passes them on along the chain (like a hot potato).
Movement of electrons releases enough energy to power the movement of H+ ions from the inner compartment into the outer compartment (like heat of a hot potato dissipating as it is passed). The ions are being pumped against their concentration gradient.
Hydrogen ions flow downhill through an enzyme called ATP synthase, like a water wheel spinning; as the ions pass, energy is used to transfer phosphate onto ADP to make ATP.
Electron Transport Chain
Greatest amount of energy is made in this stage (32-34 ATP per glucose)
Cellular Respiration
Glycolysis: 2 ATP
Krebs: 2 ATP
Electron Transport: 32 for Eukaryotes, and 34 for prokaryotes.
Total 36 for eukaryotes, and 38 for prokaryotes.
Anaerobic Respiration (fermentation)
Cytoplasm
Regenerates the cells supply of NAD+ (electron carriers)
2 Pyruvate and ONLY 2 ATP (glycolysis)
Oxygen not being available as the final receptor in the ETC.
Lactic Acid Fermentation and Alcohol Fermentation
Lactic Acid Fermentation
Converts pyruvate to lactic acid.
Transfers high energy electron and proteins from NADH.
Strenuous exercise—muscle not supplied with enough oxygen.
LA builds up; muscles become sore, cramps and fatigued
Panting helps provide extra O2; return to aerobic conditions
Alcohol Fermentation
Yeast and bacteria
Pyruvate forms Ethyl Alcohol and CO2
NADH donates electrons; NAD+ is generated.
Baking---CO2 provides bubbles (dough rise)
Alcohol—Consumable and ethanol
Comparison of Photosynthesis and Cellular Respiration
