Metabolism and Cellular Respiration

catabolism

catabolism

breakdown in living organisms of more complex substances into simpler ones together with release of energy ("Downhill rxn") endergonic (negative delta G) involve oxidation

anabolism

the synthesis in living organisms of more complex substances from simpler ones together with the storage of energy ("uphill rxn") endergonic (positive delta G) involve reductions

metabolism

Totality (all) of an organisms chemical reactions

metabolic pathway

specific molecule altered in a series of steps to make a product, each step catalyzed by a specific enzyme

energy

the capacity to cause change, can be used to do work—move matter against opposing forces, such as gravity and friction

Kinetic Energy

Energy associated w/ motion. Moving objects perform work by imparting motion to other matter

Thermal Energy

is the kinetic energy associated with random movement of atoms or molecules (Thermal energy in transfer from one object to another is called heat)

potential energy

energy that matter possesses because of its location or structure. possessed in molecules based on electron arrangement in its bonds

Chemical energy

potential energy available for release in a chemical reaction (stored in chemical bonds)

Thermodynamics

Study of energy transformation

First law of thermodynamics

(also called principle of the conservation of energy)

Energy can be transferred and transformed, but it cannot be created or destroyed

second law of thermodynamics

Every energy transfer or transformation increases the entropy (disorder/randomness) of the universe as some energy is converted to, and lost as, heat. (heat is unable to do work)

Spontaneous processes/reactions

occur without energy input; they can happen quickly or slowly. usually happen slowly and are very inefficient.

Chemical work of a cell

Endergonic rxns

Transport work of a cell

pumping substances across membranes against the direction of spontaneous movement (aka active transport)

Mechanical (movement) work of a cell

beating cilia or contracting muscle cells

endergonic reaction

of a process accompanied by or requiring the absorption of energy; the products of the process are of greater free energy than the reactants (delta G >0)

not spontaneous

exergonic reaction

of a process accompanied by the release of energy. the products of the process are of less free energy than the reactants (delta G < 0)

spontaneous

Structure of ATP

ribose (a sugar), adenine (a nitrogenous base), and three negative phosphate groups.

ADP

Adenosine DIphosphate. When ATP hydrolyzes, a phosphate group is released and it is left w/ 2 phosphate groups instead of 3

phosphorylation

transfer of a phosphate group from ATP to another molecule. typically used to power endergonic reactions

Phosphorylated intermediate

a molecule that has been phosphorylated. becomes more reactive because it is less stable and has more energy

Catalyst

a chemical agent that speeds up a reaction without being consumed by the reaction (renewable)

enzyme

a macromolecule (typically protein) that acts as a catalyst to speed up a specific reaction by lowering the activation energy (through bringing molecules closer together, providing a suitable environment, etc)

Activation energy

The initial energy needed to break the bonds of the reactants. acts as a "barrier" that molecules need to cross before a reaction can occur

Catalysis

the process by which a catalyst SELECTIVELY speeds up a reaction without itself being consumed

Substrate

The reactant that an enzyme acts on

product

the modified version of a susbtrate once it has gone through an enzyme

Enzyme substrate complec

Formed when a substrate binds to an enzyme

Active site

is the region on the enzyme, often a pocket or groove, that binds to the substrate. has a specific shape so the enzyme only binds to a certain substrate

Induced fit

Where the enzymes active site tightens around the substrate for a better fit. caused by chemical interactions

Factors affecting enzyme activity

Temperature, Ph.

How temp and ph affect enzyme activity

as ph goes up, so does the rate of enzyme catalysis until it hits a maximum, and then begins to drop again

cofactors

nonprotein helpers that bind to the enzyme permanently, or reversibly with the substrate

coenzymes

organic cofactors, most popularly vitamins

competitive inhibitors

closely resemble the substrate, and can bind to the enzyme’s active site preventing the substrate from entering

non competitive inhibitors

bind to another part of the enzyme, away from the active site. this causes the enzyme to change shape and make it less effective

allosteric regulation

when a regulatory molecule binds to a protein at one site and affects the protein’s function (Helps or inhibits) at another site

feedback regulation

where the end product of a cycle prevents the cycle from going again. stops the cell from making excess, unneeded, material.

equation for cellular respiration

C6H12O6 (glucose) + 6O2 (oxygen) → 6CO2 (carbon dioxide) + 6H20 (water) + energy (ATP)

redox reaction (oxidation-reduction rxn)

Chemical reactions that transfer electrons between reactants (can be shared in covalent bonds)

oxidation

when a substance LOSES electrons to another substance.

reduction

when a substance GAINS electrons and its positive charge is REDUCED

hydrogen ion

a H without electrons, (think of it as just a proton)

NAD+

Nicotinamide adenine dinucleotide. a coenzyme and electron carrier that carries electrons from cellular respiration to the e- transport chain (reduced form is NADH

How NADH Is formed

Enzymes called dehydrogenases remove a pair of hydrogen atoms (2 electrons and 2 protons) from the substrate, which are transferred to the NAD+. one proton is released as an H ion into the solution

electron transport chain

a series of molecules, each more electroneg than the last, built into the inner membrane of the mitochondria (or plasma membrane of prokaryotes). final electron acceptor is oxygen which turns into water

steps of cellular respiration

glycolysis - pyruvate oxidation - krebs cycle - oxidative phosphorylation

substrate level phosphorylation

enzyme transfers a phosphate group directly from a substrate to ADP to form ATP

phases of glycolysis

energy investment phase (-2 ATP to split glucose) and energy payoff phase (+ 4 ATP, +2 NADH, + 2 H20 and +2 pyruvate)

glycolysis

a metabolic process that occurs in the cytosol that breaks down glucose to form 2 pyruvate as well as other biproducts like NADH and ATP (+ 2 ATP +2 NADH, +2 H20, and +2 pyruvate per glucose) anaerobic, doesn't require oxygen

pyruvate oxidation

pyruvate dehydrogenase oxidize it, releasing co2, creating NADH, and forming acetyl co enzyme A

(+2 CO2, +2 NADH, + 2 Acetyl CoA per glucose)

krebs/citric acid cycle

oxidizes the acetyl coA in a series of 8 steps, runs twice per glucose. firstly starts as oxaloacetate, and over the next 8 steps it returns back to start the cycle again

(+2 ATP, +4 CO2, +6 NADH, and +2 FADH2 per glucose)

oxidative phosphorylation

NADH and FADH2 donate their electrons to the electron transport chain till they reach O2 to form H2O, helping to power ATP synthesis by creating a proton gradient

(+4 H20)

cytochomes

part of the ETC, proteins with heme groups containing an iron atom

FAD+(FADH2)

an electron carrier similar to NADH, but less electronegative

chemiosmosis

the use of energy in a H+ gradient to drive cellular work

chemiosmosis in cellular respiration

H+ ions are pumped into the intermembrane space as their electrons travel through the ETC (which gives the energy to pump the H+ ions in the first place). a conc grad is created and H+ ions move back across the membrane through an ATP synthase, which gives the energy to combine phosphate and ADP to make around 30 ATP

proton-motive force

H+ ion gradient created during chemiosmosis

movement of energy during cellular respiration

glucose → NADH → electron transport chain → proton-motive force → ATP

anaerobic respiration

respiring without the presence of oxygen

fermentation

without oxygen as a final electron acceptor, fermentation must occur where a different organic molecule will accept the electron so NAD+ can be regenerated.

only produces 2 ATP via substrate level phosphorylation

alcohol fermentation

pyruvate is converted to ethanol in two steps

1. releases CO2 from pyruvate

2. produces (regenerate) NAD+ and ethanol

lactic acid fermentation

pyruvate is reduced directly by NADH to form lactate and NAD+, no release of CO2

obligate anaerobes

organisms that carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 exL primitive bacteria

facultative anaerobes

can survive using either fermentation or cellular respiration. can withstand lack of oxygen for short periods of time ex: muscle cells and yeast

deanimation

proteins are used for fuel during glycolysis, and their amino groups are removed.

beta oxidation

how fatty acids are broken down to yield acetyl coA (goes straight to citric acid cycle), NADH, and FADH2

Dehydrogenase

an enzyme with 3 functions:

• takes carboxyl off of pyruvate and releases it as co2 during pyruvate oxidation -takes acetyl coA and adds it onto pyruvate

• takes 2 hydrogen atoms from substates, discards 1 proton, and adds 1 p and 2 e to nad+ (makes it NADH)