Metabolism; Cell respiration + Photosynthesis Flashcards
Metabolism
The sum of all the chemical reactions that occur within you as a living organism
Catabolism
the type of reaction that breaks down complex organic molecules with the release of energy
- are exogernic/exothermic (products of chemical reaction have less energy than reactants)
- are degradative
- example; cellular respiration
Anabolism
the type of reaction that uses energy to build complex organic molecules from simpler organic ones
- are endogernic/thermic (products of chemical reaction have more energy than reactants)
- are biosynthetic
- example; photosynthesis
metabolic pathways
Are catalyzed by enzymes and occur in specific sequences
- Cycles or chains of enzyme-catalyzed reactions
Substrate A —-> Substrate B ——> FINAL PRODUCT!
*arrows represent specific enzymes changing the substrate
INDUCED FIT MODEL
The enzyme changes shape to accommodate the substrate
activation energy
the energy needed to destabilize the existing chemical bonds in the substrate of an enzyme-substrate catalzsed reaction/ minimum energy required for a reaction to take place
what do enzymes do?
Enzymes catalyze/speed up reaction by lowering the activation needed for the reaction to occur and altering the metabolic pathway
Mechanism of enzyme action:
induced fit
The surface of the substrate contacts the active site of the enzyme
The enzyme changes shape to accommodate the substrate
A temporary enzyme-substrate complex forms
The activation energy is lowered and the substrate is altered by the rearrangement of the existing atoms
The transformed substrate, the product, is released from active site
Unchanged enzyme is then free to combine with other substrate molecules
E + S ← → ES ← → E + P
INHIBITION:
How certain molecules affect enzyme active sites, which can change/stop the activity of the enzyme
competitive inhibition
A molecule called a competitive inhibitor competes direction with the usual substrate for the active site of the enzyme, resulting that the substrate has fewer encounters with the active site and rate of the chemical reaction decreases
Must have a structure similar to the substance in order to function that way
May be reversible or irreversible
competitive inhibition example
- Sulfanilamide killing bacteria during an infection by sulfanilamide inhibiting the para aminobenzoic acid enzyme (PABA) to produce folic acid
- Antabuse blocking the enzyme that metabolizes alcohol; preventing it from breaking down to acetic acid. It works through competitive inhibitions and stops the reaction at acetaldehyde, which is toxic and makes you sick; therefore promoting alcoholics from stopping drinking
how can reversible competitive inhibition be overcome?
by increasing substrate concentration
NON- COMPETITIVE INHIBITION
Involves an inhibitor that doesn’t compete for the enzyme’s active site
Instead, it interacts with another site on the enzyme and changes the shape of the enzyme to make it non functional
It’s more effective than competitive inhibition
Also called allosteric inhibition and the site to where it binds to on the enzyme is called the allosteric site
Also reversible or irreversible
allosteric site
the site to where a noncompetitive inhibitor binds to on the enzyme
NON- COMPETITIVE INHIBITION example
Ace Inhibitor: prevents an enzyme from producing
Angiotensin II, which is a substance in your body that narrows your blood vessel and releases hormones that raise blood pressure
Treats high blood pressure, scleroderma and migraines
Reversible
reaction rate + inhibitors?
- Non-Competitive inhibitor results in a lower maximum reaction rate because the inhibitor binds to the enzyme present and isn’t released
The reaction rate will not increase as the substrate increases, as there is a limited amount of active enzymes
Competitive inhibition results in the rate of reaction increases as the substrate concentration increases, and there is a larger curve as more substrate concentration is needed to out-compete the inhibitor
END PRODUCT INHIBITION:
Prevents the cell from wasting chemical resources and energy by making more of a substance than it needs
Uses NEGATIVE FEEDBACK; when the release/production of one thing stops the release and production of another
Example: LAC OPERON
Respiration:
the controlled release of energy from organic compounds in cells to form ATP
respiration equation
6CO2 + C6H12O6 ——> 6CO2 + 6H2O + 32-38 ATP
Structure of ATP?
- adenosine triphosphate
- three phosphate groups
- ribose group
- adenine group
Electron tomography
Technique for obtaining 3D molecule visualization of subcellular structures using electron micrographs
Used to visualize cristae membrane, rotate molecules to see to scale, separation changes and view changes in mitochondrial ultrastructure during
mitochondria membrane (outer)
A membrane that separates the contents of the mitochondrion from the rest of the cell
mitochondrial matrix
An internal cytosol-like area that contains the enzymes for the link reaction and the Krebs cycle
mitchondrial cristae
Tubular regions surrounded by membranes that increase the surface area for oxidative phosphorylation
mitochondrial inner membrane
A membrane that contains the carriers for the electron transport chain and ATP synthase for chemiosmosis
mitochondrial intermembrane space
proton (H+) reserve
OILRIG
oxidation is loss of electrons and hydrogen + gain of oxygen,
reduction is gain of electrons and hydrogen + loss of oxygen
oxidiation in respiration?
glucose is oxidized
RESPIRATION:
reactions involved?
- glycolysis
- link reaction
- krebs cycle
- electron transport chain + chemiosmosis
GLYCOLYSIS
splitting 6 C molecules into x2 3 carbon Carbon Pyruvate molecules
- occurs in cytoplasm
-Anaerobic reaction (occurs in both aerobic and anaerobic reactions)
-Final products:
2 pyruvate molecules,
2 net gain of ATP (4 in total),
2 NADH molecules)
glycolysis steps
Steps:
1. Initial investment of 2 ATP
- Glucose is phosphorylated by ATP, making it unstable and causing it to split into triose phosphate which later forms pyruvate
- Triose phosphate is catalyzed by the NAD coenzyme
Through a redox reaction, NAD+ is reduced to NADH - Total of 4 ATP formed with a net gain of 2 ATP and 2 Pyruvate
- When ATP levels in the cell are high, feedback inhibition will stop the first first enzyme in the metabolic pathway
LINK REACTION
3C Pyruvate —-> 2C Acetyl CoA
Pyruvates and other molecules transported to mitochondria
OXYGEN needed for this stage; oxidative decarboxylation
Pyruvate is decarboxylated to create a 2-Carbon acetyl group
Products:
NAD co-enzyme oxidizes pyruvate (removes hydrogen), Decarboxylation removes carbon dioxide
and NADH is reduced to NAD+
Link reaction steps
Steps:
1. Pyruvate enters the mitochondrial matrix
- Enzyme removes 1 carbon dioxide and hydrogen from pyruvate
- Hydrogen is accepted by NAD+ to form NADH
- Removal of Hydrogen is oxidation, removal of CO2 is decarboxylation
(Link reaction is therefore oxidative decarboxylation) - Product is an acetyl group which reacts with Coenzyme A
- Acetyl CoA enters krebs cycle
KREBS CYCLE (or tricarboxylic acid reaction or citric acid reaction):
Begins and ends with same substance In mitochondrial matrix oxidative decarboxylation involved rdution of FAD to FADH2 and ATP to ADP, and NAD+ to NADH substrate-level phosphorylation
products; 2 ATP molecules (due to the fact that there are 2 pyruvates) 6 NADH molecules 2 FADH molecules 4 Carbon dioxide molecules
electron transport chain and chemiosmosis
Where most of the ATP from glucose catabolism is produced (in chemiosmosis)
requires oxygen as electron acceptor
requires electron carriers
creation of an electrochemical gradient pumping hydrogen ions in and out (electrons pass from carrier to another)
Occurs in the inner mitochondrial membrane and on the cristae membranes
Uses the electron transports
krebs cycle process
- Link reaction converted pyruvate to a form that can be used for the krebs cycle
- Acetyl group from acetyl CoA is transferred to a 4 carbon compound to form a 6 carbon compound
- 6 carbon compound undergoes decarboxylation (Carbon Dioxide removed as waste product and excreted) and oxidation to form a 5 carbon compound. Oxidation releases energy which is stored by carriers which will be used in electron transport chain to produce ATP
- 5 carbon compound undergoes decarboxylation and oxidation again to form a 4 carbon compound. Hydrogen is accepted by NAD+ to form NADH + H+ ( to be used in electron transport chain)
- The 4 carbon compound undergoes substrate-level phosphorylation and during this reaction produces 1 ATP.
ATP is formed by ADP + P+ - Hydrogen is accepted by NAD+ to form NADH + H+
Another H is accepted by FAD to form FADH2 - Four carbon compound ready now to accept another acetyl group and repeat cycle
electron carriers in ETC
- FADH2 enters the ETC at lower free energy levesl than NADH
- thus FADH2 allos the production of two ATPs while NADH allows production of three ATPs
- at the end, de-energized electrons combine with oxygen and hydrogen ions to form wawter
why is oxygen the final electron acceptor?
- high electoneativiy; strong electron attraction
- two hydrogen ions and electron join with one oxygen= water
how is ATP formed in the ETC?
- energy through electrochemical gradient
- movement of of H+ ions back into mitochondrial matrix (due to diffusion from high to low concentration) by ATP synthase causes ATP + Pi to form ATP for each proton pumped back (phosphorylation)
energy flow of cellular respiration?
glucose –> NADH or FADH2
- -> Electron Transport Chain
- -> Chemiosmosis
- -> ATP
how much atp is produced in;
- glycolysis
- krebs cycle
- ETC and chemiosomis
- 2 used, 4 produced, 2 net gain
- 2 net gain
- 32 net gain
where do light dependent reactions occur
In the thylakoids or grana of the chloroplast; a stack of thylakoids are made up of a granum. Light supplies energy for reaction to occur.
where did light independent reactions take place
stroma
photosynthesis equation
carbon dioxide + water—> Glucose + oxygen
How does a plant absorb sunlight?
Through pigment molecules that absorbs photons of light at different wavelengths
Chlorophylls
Carotenoids
light dependent reaction process
a. (chlorophyll/pigments/antenna complex) in photosystem II absorb light;
b. light/photoactivation produces an excited/high energy/free electron;
c. electrons pass from carrier to carrier/along electron transport chain/e.t.c.;
d. protons pumped across thylakoid membrane/into thylakoid space;
e. ATP produced (by the light dependent reactions);
f. ATP production by chemiosmosis/by ATP synthase/ATP synthetase;
g. electrons from photosystem II passed to photosystem I;
h. light/photoactivation excites electrons in photosystem I
(to higher energy level);
i. production of NADPH/reduction of NADP(+) (using electrons from photosystem I); (reject NAD in place of NADP. Accept reduced NADP instead of NADPH)
j. electrons from photolysis (needed) for photosystem II;
k. oxygen from photolysis is a waste product/by-product/passes out/excreted;
l. in cyclic photophosphorylation electrons from photosystem I return to it;
light dependent reaction processes
TWO PROCESSES:
Photosystem I
Photosystem II
process?
A photon of light is absorbed by a pigment in Photosystem II and is transferred to other pigment molecules until it reaches one of the chlorophyll α molecules in the reaction centre.
The photon energy excites one of the chlorophyll α electrons to a higher state
This electron is captured by the primary acceptor of the reaction centre
Water is split by an enzyme to produce electrons, hydrogen ions and an oxygen atom. This process is driven by the energy from light and is called photolysis.
The electrons are supplied one by one to the chlorophyll α molecules of the reaction centre
The energy lost from the electrons moving down the ETC lose energy at each exchange. The first three of the carriers is the plastoquinone (PQ). The middle carrier is a cytochrome complex
A photon of light is absorbed by a pigment in Photosystem I. This energy is transferred through several accessory pigments until received by a chlorophyll molecules. This results in an electron with a higher energy state being transferred to the primary electron acceptor. The de-energized electron from PII fills the void left by the newly energized electron
The electron with the higher energy state is then passed down a second electron transport chain that involved the carrier FERREDOXIN
The enzyme NADP reductase catalyzes the transfer of the electron from FERREDOXIN to the energy carrier NADP+. Two electrons are required to reduce NADP+ fully to NADPH
FINAL PRODUCTS: NADPH and ATP; supply chemical energy for light independent reactions
final product of light depdendent reactiosn
FINAL PRODUCTS: NADPH and ATP; supply chemical energy for light independent reactions
Photosynthesis Chemiosmosis
Involves an electron transport chain in the THYLAKOID membrane
Energy is released when electrons are exchanged from one carrier to another
Released energy is used to pump hydrogen ions actively into the thylakoid space
Hydrogen ions come from the stroma
Hydrogen ions diffuse back into the stroma through the channels of ATP synthase
ATP synthase catalyses the photophosphorylation of ADp to form ATP
respiration Chemiosmosis
Involves an electron transport chain in the CRISTAE membrane
Energy is released when electrons are exchanged from one carrier to another
Released energy is used to pump hydrogen ions actively into the intermembrane space
Hydrogen ions come from the matrix
Hydrogen ions diffuse back into the matrix through the channels of ATP synthase
ATP synthase catalyses the phosphorylation of ADp to form ATP
calvin cycle; light independent reaction
CALVIN CYCLE! Ribulose bisphosphate (RuBP) binds to a CO2 molecule (CARBON FIXATION) catalyzed by the RuBP carboxylase enzyme resulting in a 6 carbon compound
6- carbon compound breaks into two 3-carbon compounds called GLYCERATE 3- PHOSPHATE
The G3P are acted upon by ATP and NADPH to form triose phosphate (reduction reaction)
TP molecules can become sugar phosphates and form complex carbohydrates OR continue in the cycle
To regain RuBP from TP, the Calvin Cycle uses ATP (regeneration)
light dependent reaction summary
Occurs in the thylakoids
Uses light energy to form ATP and NADPH
Splits water in photolysis to provide replacement electrons and H+ and release Oxygen
Includes two electron transport chains and Photosystems I and II
light independent reaction summary
Occurs in stroma
Uses ATP and NADPH to form triose phosphate
Returns ADp, inorganic phosphate and NADP to light dependent reaction
Calvin Cycle
membrane surface area of the thylakoid
Allows greater light absorption
lumen
Small space (lumen) in thylakoid Allows for faster proton accumulation to create concentration gradient
Stroma region
Stroma region similar to cytosol of cell
Allows for an area that enzymes can work in for Calvin cycle
(site for light independent reactions)
double membrane
Double membrane
Isolates working parts and enzymes from surrounding cytosol
granum
stacks of thylakoids
thylakoid
site of light dependent reaction
flattened membrane sacts with chlorophyll component
