Unit 3

metabolism: all of the chemical reactions in an organism

metabolic pathways: series of chemical reactions that either build or break down complex molecules; regulated by controlling when and where enzymes are active

^ to stop production, inhibit enzymes 2 or 3

catabolic pathways: release energy by breaking down complex molecules into simpler compounds

anabolic pathways: consume energy to build complex molecules from simpler compounds

exergonic reactions: release energy; change in free energy < 0

endergonic reactions: absorb energy; change in free energy > 0

ENZYMES

  • macromolecules that catalyze reactions by lowering the activation energy

  • has an active site that substrates bind to

  • level off = all active sites have been filed

  • slows down = substrates have been used up

induced fit: enzymes change the shape of their active site to allow the substrate to bind better

enzyme catabolism: enzyme breaks down complex molecules

enzyme anabolism: enzyme builds complex molecules

Efficiency of enzymes can be affected by:

  1. temperature β†’ rate of activity increases due to collision up to a certain point, after, the enzyme will denature

  2. pH levels β†’ being outside the normal pH range can cause hydrogen bonds in the enzyme to break

  3. substrate concentration

  4. enzyme concentration

cofactors: non-protein molecules that assist enzyme function

coenzymes: organic cofactors

enzyme inhibitors: reduce the activity of specific enzymes

  • permanent β†’ binds with covalent bonds

  • reversible β†’ binds with weak interactions

  1. competitive β†’ reduces enzyme activity by blocking substrates from binding to the active site β†’ can be reversed by adding more substrates

  2. noncompetitive β†’ binds to an area other than the active site, which changes the shape of the site, preventing substrates from being able to bind β†’ nonreversible

allosteric regulation: molecules bind to an allosteric site which changes the shape and function of the site

allosteric activator: substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites stay open

allosteric inhibitors: substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain closed

cooperativity: substrate binds to one active site on an enzyme that has more than one active site, which stabilizes the active form

feedback inhibition: when the end product of a metabolic pathway can act as an inhibitor to an early enzyme in the same pathway

PHOTOSYNTHESIS

  • the conversion of light energy into chemical energy

  • occurs in the chloroplast

  • two steps: light reactions and calvin cycle

  • autrophs: organisms that produce their own food (organic molecules from their surroundings)

  • heterotrophs: organisms that are unable to make their own food, so they live off of other organisms

oxidation: loss of H+ and e-, gain of O

reduction: gain of H+ and e-, loss of O

light: electromagnetic energy

  • made up of photons

  • travels in waves

wavelength: the distance from the crest of one wave to the crest of the next

  • short wavelengths = higher energy

  • long wavelengths = lower energy

chlorophyll a: primary pigment, reaction center

chlorophyll b: accessory pigment

carotenoids: broaden the spectrum of colors that drive photosynthesis

photoprotection: carotenoids absorb and dissipate excessive light energy that could damage chlorophyll or interact with oxygen

LIGHT REACTIONS

  1. it takes place in the thylakoid membrane

  2. photosystems (reaction centers and light-capturing complexes) are embedded in the membrane, along with electron transport proteins

  3. pigments, both primary and accessory, are found in PSI, and they absorb energy from photons

  4. PS2 is where photolysis (the splitting of H2O into 02 + H+ + e-) occurs

  5. the e- gets excited (from the energy passed on from the pigments) and transported via an ETC, losing water until it reaches PSI

  6. the e- gets excited again, leaves PSI, and gets accepted by an e-acceptor NADP β†’ which then gets reduced to NADPH

  7. ATP is generated by phosphorylation ADP

CALVIN CYCLE

β†’ the continuous phosphorylation and reduction of G3P and oxidation of NADPH (which is a product of the light reaction) to reduce G3P

β†’ occurs in the stroma

  1. carbon fixation β†’ CO2 (1C) attaches to ruBP (5C) with the help of the enzyme rubisco β†’ it forms a 6C compound, but is unstable; hence, it immediately turns into 3C compound called phosphoglycerate

  2. reduction β†’ G3P gets reduced β†’ one 3C compound leaves the cycle to make organic compounds like glucose

  3. regeneration of ruBP β†’ uses 3ATP to do so β†’ needs to keep regenerating in order to keep making glucose

CELLULAR RESPIRATION

  • cells harvest chemical energy stored in organic molecules and use it to generate ATP

GLYCOLYSIS

β†’ occurs in the cytosol

β†’ splits glucose (6C) into 2 pyruvates (3C)

  1. energy investment β†’ the cell uses ATP to phosphorylate compounds of glucose

  2. energy payoff β†’ energy is produced by substrate level phosphorylation (when you gain a phosphate group)

net:

β†’ 2 pyruvate + 2H2O

β†’ 2 ATP

β†’ 2 NADH + 2H+

PYRUVATE OXIDATION

β†’ occurs in the mitochondrial matrix

  1. the pyruvate is oxidized by CoA into acetyl CoA

  2. NAD+ is reduced to NADH and CO2 is given off as a byproduct

KREBS CYCLE

β†’ occurs in the mitochondrial matrix

  1. acetyl CoA (2C) binds to oxaloacetate (4C) to become citrate (6C)

  2. citrate goes through decarboxylation and releases CO2

  3. also goes through oxidation and releases H

  4. this results in the reduction of NAD to NADH

  5. the conversion of the 4C compound also results in the production of ATP through substrate level phosphorylation

  6. the 4C compound gets to be further oxidized and releases H that is received by FAD β†’ FADH2

net:

β†’ 2 ATP

β†’ 6 NADH

β†’ 4 CO2 (the other 2 were from pyruvate oxidation)

β†’ 2 FADH2

ETC

  • a sequence of membrane proteins that shuttle electrons down a series of redox reactions

  • located in the inner membrane of the mitochondria

  • creates a proton gradient across the membrane



    CHEMIOSMOSIS

  • the movement of water from a region of higher concentration to a region of lower concentration along a concentration gradient

  • ATP synthase is the enzyme that makes ATP from substrate level phosphorylation, powered by an electrochemical gradient

  • H+ ions flow down the gradient through ATP synthase, producing 26-28 ATP per glucose

ANAEROBIC RESPIRATION

  • generates ATP using an ETC in the absence of oxygen

FERMENTATION

  • generates ATP without an ETC

  • an extension of glycolysis

ALCOHOL FERMENTATION

β†’ pyruvate is converted into ethanol

β†’ lactate dehydrogenase allows NADH to be oxidized to NAD+, which is the process of fermentation

β†’ this process allows bacteria to produce ATP by glycolysis

LACTIC ACID FERMENTATION

β†’ pyruvate is reduced by NADH to form lactate

β†’ muscles produce lactate, which goes into the blood, and is broken down back to glucose in the liver

β†’ when the lactate is in the blood, it lowers the pH

β†’ if lactate builds up and is unable to be broken down, it can lead to lactic acidosis (extremely low blood pH)


  • Oxygen is used as the final electron acceptor in the ETC

  • The larger the concentration of glucose in the culture medium, the larger the ATP concentration in the cells

  • Adding a compound that binds and releases protons would increase the proton concentration in the intermembrane space, resulting in a large production of ATP in the cells

  • enzyme activity increases as temperature increases