BSC2010 Exam 3 Terms

metabolism

the building and breakdown (chemical reactions) of carbon sources to harness or release energy

anabolic reaction

bonds are made (dehydration synthesis), requires energy (e.g., amino acid molecules—protein molecule)

catabolic reaction

bonds are broken (hydrolysis), release energy (e.g., glycogen—glucose molecules)

potential energy (PE)

energy that is not associated with movement but rather is stored

kinetic energy (KE)

the energy of motion

anabolic/synthesis reaction

endergonic reactions are also known as…

reactions that require energy input

endergonic reactions

catabolic reactions

exergonic reactions are also known as…

these reactions release energy

exergonic reactions

reaction coupling

the linking of an exergonic reaction to an endergonic reaction so that the energy released drives the nonspontaneous reaction (one reaction powers another by being linked to it)

kinetic energy (exergonic)

heat is a form of…

first law of thermodynamics

energy cannot be created or destroyed; it can only be transformed

second law of thermodynamics

energy transfers increase disorders (entropy), and some energy is lost as heat

ATP hydrolysis

ATP hydrolysis is exergonic (spontaneous) and releases energy (ΔG < 0)

energetic coupling

an exergonic reaction drives an endergonic reaction

energy is released (exergonic)

ΔG < 0

energy is consumed (endergonic)

ΔG > 0

activation energy

energy needed to start a chemical reaction

enzymes lower activation energy by helping reactants reach the transition state more easily

why do enzymes lower the activation energy of a reaction?

allosteric regulation

when a molecule binds to an enzyme at a different site and changes its activity

metabolic pathway

a series of enzyme-controlled steps that turn a starting molecule into a final product

negative feedback

the final product of a pathway shuts down an earlier step

cellular respiration

uses chemical energy (PE stored in bonds of molecules) such as carbohydrates and lipids to produce ATP

redox reactions

chemical reactions where electrons are transferred from one molecule to another

reduced

molecules that gain electron(s) after the reaction are…

oxidized

molecules that lose electron(s) after the reaction are…

coenzymes

small organic helper molecules that assist enzymes in carrying out reactions, they don’t do the reaction alone—but the enzyme often can’t function without them

carry electrons, carry functional groups (like methyl or acetyl groups), help stabilize reactions so they can occur more easily

what are common roles of coenzymes?

NAD+/NADH; FAD/FADH2; Coenzyme A (CoA); they are often derived from vitamins, reusable (not consumed permanently), they may temporarily bind to the enzyme, then leave

common examples of coenzymes

NAD+

carries electrons in cellular respiration

FAD

carries electrons in cellular respiration

Coenzyme A (CoA)

carries acetyl groups (important in metabolism)

glycolysis (in the cytoplasm), pyruvate oxidation (link reaction), Krebs Cycle (Citric Acid Cycle), Electron Transport Chain (ETC) + Chemiosmosis

steps of cellular respiration

glycolysis (in the cytoplasm)

glucose (6C) is split into 2 pyruvate (3C each), does not require oxygen; outputs: 2 ATP (net), 2 NADH

pyruvate oxidation (link reaction)

each pyruvate is converted into acetyl-CoA, occurs in the mitochondrial matrix; outputs (per glucose): 2 NADH, 2 CO2

Krebs Cycle (Citric Acid Cycle)

Acetyl-CoA is fully broken down, carbon is released as CO2; outputs (per glucose): 2 ATP, 6 NADH, 2 FADH2, 4 CO2

electron transport chain (ETC) + chemiosmosis

happens in the inner mitochondrial membrane, NADH and FADH2 donate electrons, energy pumps H+ to create a gradient, ATP synthase uses that gradient to make ATP; key point: oxygen is the final electron acceptor—forms water; outputs: ~26-28 ATP, H2O

aerobic process

requires oxygen, glucose is fully broken down, goes through cellular respiration (ex. cardio)

anaerobic process

occurs without oxygen, only glycolysis occurs, then fermentation regenerates NAD+ so glycolysis can continue (ex. lifting)t

lactic acid fermentation, alcohol fermentation

types of fermentation

lactic acid fermentation

pyruvate—lactate, happens in muscle cells

alcohol fermentation

pyruvate—ethanol+CO2, happens in yeast

phase 1 of glycolysis: energy-consuming reactions

preparatory phase, uses 2 ATP to convert glucose to fructose-1,6-biphosphate; includes hexokinase and phosphofructokinase (rate-limiting enzyme); no ATP produced, prepares molecule for splitting

phase 2 of glycolysis: splitting glucose

cleavage phase, fructose-1,6-bisphosphate is split into 2 3C molecules (G3P+DHAP); DHAP—G3P, yielding 2 G3P total; no ATP used or produced

phase 3 of glycolysis: energy-producing reactions

payoff phase with production of 4 ATP and 2 NADH

2 G3P—2 pyruvate; produces 4 ATP (net +2 ATP overall) and 2 NADH via substrate-level phosphorylation

free energy changes during glycolysis

glycolysis is overall exergonic: energy invested early, more released later as ATP and NADH

energy is stored as ATP and reduced electron electron carriers (NADH)

mitochondrial matrix

linking step (aka pyruvate oxidation) occurs in…

mitochondrial matrix

innermost compartment of the mitochondrion; contains enzymes for pyruvate oxidation and the Krebs cycle, along with mtDNA (mitochondrial DNA) and ribosomes

mitochondrial DNA (mtDNA)

small circular DNA in the mitochondrial matrix that encodes some proteins for cellular respiration; inherited maternally

glycolysis, linking step, and the Krebs cycle

free energy changes during…

electron transport chain and chemiosmosis (ATP synthase)

phases of oxidative phosphorylation

electron transport chain (ETC)

series of protein complexes in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, pumping H+ to create a proton gradient

chemiosmosis

the process of movement of H+ down their electrochemical gradient through ATP synthase, driving ATP production

store potential energy that is used to make ATP

the ETC pumps H+ (protons) into the intermembrane space, this creates: high H+ outside and low H+ inside (the difference = electrochemical gradient aka stored energy)

what is the point of the proton gradient?

ATP synthase

the enzyme, the protein that protons flow through, actually builds ATP

splits glucose into two smaller molecules, starts with glucose, ends w pyruvate, makes a little ATP and electron carriers

what is glycolysis?

converts pyruvate into acetyl-CoA, releasing CO2 and transferring electrons

what is the linking step (pyruvate oxidation)?

breaks down acetyl-CoA to release CO2 and produces lots of electron carriers (NADH, FADH2)

completes breakdown of carbon molecules

what is the krebs cycle?

uses electrons from earlier steps, creates proton gradient, makes most of the ATP

what is oxidative phosphorylation?

fermentation

in the absence of oxygen, pyruvate can be reduced to lactic acid, this regenerates NAD+

bacteria produce alcohol to make wine; yeast produce carbon dioxide which makes bread rise and alcohol in beer; animals produce lactate in muscles when exercising

examples of fermentation (anaerobic respiration, no oxygen) outside the mitochondria

photosynthesis

converting light energy to chemical energy

chlorophyll

green pigment that absorbs light waves

• 60% is outside the visible range and unavailable for photosynthesis

• 8% reflected or transmitted

• 20% lost during carbohydrate synthesis, including photorespiration

• 8% converted into heat

• maximum 4% yield in the form of carbohydrates

what happens to the sun’s output when photosynthesis occurs?

photorespiration

when Rubisco (an enzyme) uses oxygen instead of carbon dioxide, reducing sugar production

uses energy but does not make sugar, can actually reduce photosynthesis efficiency; happens more when it’s hot and CO2 levels are low

what is the problem of photorespiration?

photosynthetic bacteria (prokaryotes) that produce oxygen

what are cyanobacteria?

endosymbiotic theory

a cyanobacterium was engulfed by a eukaryotic cell and over time, the cyanobacterium lost the ability to live outside the host and became the organelle we know as the chloroplast

heterotrophs

get their energy from “eating others”, consumers of organisms, consume organic molecules (e.g., animals, fungi, many bacteria)

make energy and organic molecules from ingesting organic molecules

autotrophs

get their energy from “self”, get their energy from sunlight, use light energy to synthesize organic molecules (e.g., plants, algae, cyanobacteria)

make energy and organic molecules from light energy

between 400nm and 700nm

visible waves have wavelengths…

photon

a packet of light energy, behave as both particles and as waves